Science.gov

Sample records for alkaline paddy soil

  1. Speciation and release kinetics of cadmium in an alkaline paddy soil under various flooding periods and draining conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding the chemical forms in which Cd is present in paddy soils is needed to develop efficient and cost-effective strategies to clean up the soils, and/or minimize Cd uptake by rice. This study aims to determine Cd speciation and release kinetics in an alkaline paddy soil, at various flooding...

  2. Speciation and Release Kinetics of Cadmium in an Alkaline Paddy Soil Under Various Flooding Periods and Draining Conditions

    SciTech Connect

    S Khaokaew; R Chaney; G Landrot; M Ginder-Vogel; D Sparks

    2011-12-31

    This study determined Cd speciation and release kinetics in a Cd-Zn cocontaminated alkaline paddy soil, under various flooding periods and draining conditions, by employing synchrotron-based techniques, and a stirred-flow kinetic method. Results revealed that varying flooding periods and draining conditions affected Cd speciation and its release kinetics. Linear least-squares fitting (LLSF) of bulk X-ray absorption fine structure (XAFS) spectra of the air-dried, and the 1 day-flooded soil samples, showed that at least 50% of Cd was bound to humic acid. Cadmium carbonates were found as the major species at most flooding periods, while a small amount of cadmium sulfide was found after the soils were flooded for longer periods. Under all flooding and draining conditions, at least 14 mg/kg Cd was desorbed from the soil after a 2-hour desorption experiment. The results obtained by micro X-ray fluorescence ({mu}-XRF) spectroscopy showed that Cd was less associated with Zn than Ca, in most soil samples. Therefore, it is more likely that Cd and Ca will be present in the same mineral phases rather than Cd and Zn, although the source of these two latter elements may originate from the same surrounding Zn mines in the Mae Sot district.

  3. Mineralization of metsulfuron-methyl in Chinese paddy soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A laboratory study was conducted to investigate the mineralization of metsulfuron-methyl (MSM) in paddy soils in response to soil moisture, temperature and soil properties. The results indicated that MSM mineralization was relatively limited in the paddy soils when soil temperature was low. Only 2.2...

  4. Fertilization increases paddy soil organic carbon density*

    PubMed Central

    Wang, Shao-xian; Liang, Xin-qiang; Luo, Qi-xiang; Fan, Fang; Chen, Ying-xu; Li, Zu-zhang; Sun, Huo-xi; Dai, Tian-fang; Wan, Jun-nan; Li, Xiao-jun

    2012-01-01

    Field experiments provide an opportunity to study the effects of fertilization on soil organic carbon (SOC) sequestration. We sampled soils from a long-term (25 years) paddy experiment in subtropical China. The experiment included eight treatments: (1) check, (2) PK, (3) NP, (4) NK, (5) NPK, (6) 7F:3M (N, P, K inorganic fertilizers+30% organic N), (7) 5F:5M (N, P, K inorganic fertilizers+50% organic N), (8) 3F:7M (N, P, K inorganic fertilizers+70% organic N). Fertilization increased SOC content in the plow layers compared to the non-fertilized check treatment. The SOC density in the top 100 cm of soil ranged from 73.12 to 91.36 Mg/ha. The SOC densities of all fertilizer treatments were greater than that of the check. Those treatments that combined inorganic fertilizers and organic amendments had greater SOC densities than those receiving only inorganic fertilizers. The SOC density was closely correlated to the sum of the soil carbon converted from organic amendments and rice residues. Carbon sequestration in paddy soils could be achieved by balanced and combined fertilization. Fertilization combining both inorganic fertilizers and organic amendments is an effective sustainable practice to sequestrate SOC. PMID:22467369

  5. Fly ash effect on improving soil properties and rice productivity in Korean paddy soils.

    PubMed

    Lee, Hyup; Ha, Ho Sung; Lee, Chang Hoon; Lee, Yong Bok; Kim, Pil Joo

    2006-09-01

    Paddy soils in Korea generally require the addition of Si to enhance rice productivity. Coal combustion fly ash, which has a high available Si content and alkaline pH, was selected as a potential source of Si in this study. Two field experiments were carried out to evaluate rice (Oryza sativa) productivity in silt loam and loamy sand soils to which 0, 40, 80, and 120 Mg ha(-1) of fly ash were added with 2 Mg ha(-1) Si as a control. Fly ash increased the soil pH and available Si and P contents of both soils. The amount of available B increased to a maximum of 2.57 mg kg(-1), and the B content of the rice plants increased to a maximum of 52-53 mg kg(-1) following the addition of 120 Mg ha(-1) fly ash. The rice plants did not show toxicity effects. The highest rice yields were achieved following the addition of around 90 Mg ha(-1) fly ash. The application of fly ash increased Si, P and K uptake by the rice plants, but did not result in an excessive uptake of heavy metals in the submerged paddy soil. In conclusion, fly ash could be a good supplement to other inorganic soil amendments to improve the nutrient balance in paddy soils. PMID:16153826

  6. Distribution of tetraether lipids in agricultural soils - differentiation between paddy and upland management

    NASA Astrophysics Data System (ADS)

    Mueller-Niggemann, C.; Utami, S. R.; Marxen, A.; Mangelsdorf, K.; Bauersachs, T.; Schwark, L.

    2015-10-01

    Insufficient knowledge of the composition and variation of isoprenoid and branched glycerol dialkyl glycerol tetraethers (GDGTs) in agricultural soils exists, despite of the potential effect of different management types (e.g. soil/water and redox conditions, cultivated plants) on GDGT distribution. Here, we determined the influence of different soil management types on the GDGT composition in paddy (flooded) and adjacent upland (non-flooded) soils, and if available also forest, bushland and marsh soils. To compare the local effects on GDGT distribution patterns, we collected comparable soil samples in various locations from tropical (Indonesia, Vietnam and Philippines) and subtropical (China and Italy) sites. We found that differences in the distribution of isoprenoid GDGTs (iGDGTs) as well as of branched GDGTs (brGDGTs) are predominantly controlled by management type and only secondarily by climatic exposition. In general upland soil had higher crenarchaeol contents than paddy soil, which on the contrary was more enriched in GDGT-0. The GDGT-0 / crenarchaeol ratio was 3-27 times higher in paddy soil and indicates the enhanced presence of methanogenic archaea, which were additionally linked to the number of rice cultivation cycles per year (higher number of cycles was coupled with an increase in the ratio). The TEX86 values were 1.3 times higher in upland, bushland and forest soils than in paddy soils. In all soils brGDGT predominated over iGDGTs, with the relative abundance of brGDGTs increasing from subtropical to tropical soils. Higher BIT values in paddy soils compared to upland soils together with higher BIT values in soil from subtropical climates indicate effects on the amounts of brGDGT through differences in management as well as climatic zones. In acidic soil CBT values correlated well with soil pH. In neutral to alkaline soils, however, no apparent correlation but an offset between paddy and upland managed soils was detected, which may suggest that soil

  7. Distribution of tetraether lipids in agricultural soils - differentiation between paddy and upland management

    NASA Astrophysics Data System (ADS)

    Mueller-Niggemann, Cornelia; Rahayu Utami, Sri; Marxen, Anika; Mangelsdorf, Kai; Bauersachs, Thorsten; Schwark, Lorenz

    2016-03-01

    GDGT predominated over iGDGTs with the relative abundance of brGDGTs increasing from subtropical to tropical soils. Higher branched vs. isoprenoid tetraether (BIT) values in paddy soils compared to upland soils together with higher BIT values in soils from subtropical climates indicated effects on the amounts of brGDGT induced by differences in management as well as climate. In acidic soils cyclization ratio of branched tetraethers (CBT) values correlated well with soil pH. In neutral to alkaline soils, however, no correlation but an offset in CBT between paddy and upland managed soils was detected. This is interpreted as indicating soil moisture exerting an additional control on the CBT in these soils. Lower modified methylation index of branched tetraether (MBT') values and temperatures calculated from this (TMC) in paddy soils compared to upland soils are attributed to a management-induced (e.g. enhanced soil moisture via flooding) effect on mean annual soil temperature (MST).

  8. Enzyme dynamics in paddy soils of the rice district (NE Italy) under different cropping patterns

    NASA Astrophysics Data System (ADS)

    Bini, Claudio; Nadimi-Goki, Mandana; Kato, Yoichi; Fornasier, Flavio; Wahsha, Mohammad; Spiandorello, Massimo

    2014-05-01

    The recent widespread interest on soil enzymes is due to the need to develop sensitive indicators of soil quality that reflect the effects of land management on soil and assist land managers in promoting long-term sustainability of terrestrial ecosystems. The activities of six important enzymes involved in C, N, P, and S cycling were investigated in a paddy soil from the Veneto region, Italy, in four different rotation systems (rice-rice-rice: R-R-R; soya-rice-rice: S-R-R; fallow-rice: F-R; pea-soya-rice: P-S-R) with three replications in April (after field preparation, field moist condition), June (after seedling, waterlogged soil condition), August (after tillering stage of rice, waterlogged soil condition) and October (after rice harvesting, drained soil condition) over the 2012 growing season. Our results demonstrated that enzyme activities varied with rotation systems and growth stages in paddy soil. Compared with field moist soil, drained soil condition resulted in a significant increase (P < 0.05) of β-glucosidase, arylsulfatase, alkaline and acid phosphatases, leucine aminopeptidase (except of fallow-rice), and chitinase activities in all rotations, while compared with drained soil, early waterlogging (in month of June) significantly decreased (P moist soil> late waterlogged>early waterlogged. There was an inhibitory effect of waterlogging (except P-S-R rotation) for both alkaline and acid phosphatases due to high pH and redox conditions. However, the response of enzymes to waterlogging differed with the chemical species and the cropping pattern. The best rotation system for chitinase, leucine aminopeptidase and β-glucosidase activity (C and N cycles) proved R-R-R, while for arylsulfatase, alkaline and acid phosphatases (P and S cycles) it was the S-R-R. Key Words: enzyme activity, paddy soil, Crop Rotation System, Italy __ Corresponding Author: Mandana Nadimi-Goki, Tel.: +39 3891356251 E-mail address: mandy.nadimi@gmail.com

  9. 2000 years of paddy soil development - gain and loss of soil carbon

    NASA Astrophysics Data System (ADS)

    Koelbl, A.; Kalbitz, K.; Fiedler, S.; Braeuer, T.; Grootes, P. M.; Cao, Z.; Jahn, R.; Vogelsang, V.; Wissing, L.; Koegel-Knabner, I.

    2010-12-01

    The long-term impact of lowland rice growing on C stocks in soils was evaluated in the coastal region of subtropical China. During the past 2000 years new farmland was created through consecutive land reclamation by protective dikes, providing a unique chronosequence of soil formation under agricultural use. Parts of the land were used for paddy rice, other parts for a variety of non-irrigated crops, allowing study of the C dynamics of paddy soil development in direct comparison to soils not used for lowland rice cultivation (non-paddy). Beside one soil profile at the mudflat, which represents the parent material, soil profiles of the chronosequence were sampled by horizon in triplicate, ranging from 50 to 2000 years of paddy soil use and from 50 to 700 year old non-paddy soils. All samples were analysed for 14C concentrations and for bulk density, total C (TC) as well as organic C (OC) and inorganic C (IC) concentrations, and the corresponding stocks were calculated. In addition, topsoils were subjected to a physical fractionation procedure to evaluate changes of OC saturation in particle size fractions during soil development. In the first 300 years, rice cultivation did not significantly change TC stocks of the soils compared to that of non-paddy soils. The fast decalcification in paddy soils was compensated by a similar gain of OC in the topsoil. Higher 14C concentrations indicate the original C of the sediment in paddy topsoils was replaced faster by recently photosynthesized C than in non-paddy topsoils. OC accumulation in paddy topsoils appears to be complete after 300 years. High increases of OC in paddy topsoils may be due to high OC inputs associated with retarded decomposition during flooding of paddy fields. After 300 years, the decalcification in paddy soils was not compensated anymore by further enrichment of OC in the topsoil. In addition, the paddy soils lost OC in the subsoil. The dense plough pan decreases OC transport from the paddy topsoil into

  10. Soil type-depending effect of paddy management: composition and distribution of soil organic matter

    NASA Astrophysics Data System (ADS)

    Urbanski, Livia; Kölbl, Angelika; Lehndorff, Eva; Houtermans, Miriam; Schad, Peter; Zhang, Gang-Lin; Rahayu Utami, Sri; Kögel-Knabner, Ingrid

    2016-04-01

    Paddy soil management is assumed to promote soil organic matter accumulation and specifically lignin caused by the resistance of the aromatic lignin structure against biodegradation under anaerobic conditions during inundation of paddy fields. The present study investigates the effect of paddy soil management on soil organic matter composition compared to agricultural soils which are not used for rice production (non-paddy soils). A variety of major soil types, were chosen in Indonesia (Java), including Alisol, Andosol and Vertisol sites (humid tropical climate of Java, Indonesia) and in China Alisol sites (humid subtropical climate, Nanjing). This soils are typically used for rice cultivation and represent a large range of soil properties to be expected in Asian paddy fields. All topsoils were analysed for their soil organic matter composition by solid-state 13C nuclear magnetic resonance spectroscopy and lignin-derived phenols by CuO oxidation method. The soil organic matter composition, revealed by solid-state 13C nuclear magnetic resonance, was similar for the above named different parent soil types (non-paddy soils) and was also not affected by the specific paddy soil management. The contribution of lignin-related carbon groups to total SOM was similar in the investigated paddy and non-paddy soils. A significant proportion of the total aromatic carbon in some paddy and non-paddy soils was attributed to the application of charcoal as a common management practise. The extraction of lignin-derived phenols revealed low VSC (vanillyl, syringyl, cinnamyl) values for all investigated soils, being typical for agricultural soils. An inherent accumulation of lignin-derived phenols due to paddy management was not found. Lignin-derived phenols seem to be soil type-dependent, shown by different VSC concentrations between the parent soil types. The specific paddy management only affects the lignin-derived phenols in Andosol-derived paddy soils which are characterized by

  11. Organic phosphorus fractions in organically amended paddy soils in continuously and intermittently flooded conditions.

    PubMed

    Yang, Changming; Yang, Linzhang; Jianhua, Lee

    2006-01-01

    Soil organic phosphorus (SOP) can greatly contribute to plant-available P and P nutrition. The study was conducted to determine the effects of organic amendments on organic P fractions and microbiological activities in paddy soils. Samples were collected at the Changshu Agro-ecological Experiment Station in Tahu Lake Basin, China, from an experiment that has been performed from 1999 to 2004, on a paddy soil (Gleysols). Treatments consisted of swine manure (SM), wheat straw (WS), swine manure plus wheat straw (SM + WS), and a control (chemical fertilization alone). Organic amendments markedly increased soil total organic phosphorus (TOP) and total organic carbon (TOC), especially in continuously flooded conditions. Based on the fractionation of SOP, organic amendments significantly increased soil labile organic phosphorus (LOP), moderately labile organic phosphorus (MLOP), and moderately stable organic phosphorus (MSOP) compared with the control. For SM and SM + WS treatments, LOP in continuously flooded soils decreased by 30.1 and 36.4%, respectively, compared to intermittently flooded soils. In organically amended soils, continuous flooding showed significantly lower microbial biomass phosphorus (MBP) and alkaline phosphatase activities (APA) than intermittent flooding. In intermittently flooded conditions, incorporating organic amendments into soil resulted in greater P uptake and biomass yield of rice than the control. In the intermittently flooded soils, APA (P < 0.05) and MBP (P < 0.01) were significantly and positively related to TOP, LOP, MLOP, and MSOP, whereas in continuously flooded soils, there was a significant (P < 0.05) negative relationship between MBP, TOP, and MSOP. Based on soil organic P fractions and soil enzymatic and microbiological activities, continuous flooding applied to paddy soils should be avoided, especially when swine manure is incorporated into paddy soil. PMID:16738400

  12. Microbial lipids in Paddy Soils of the Yangtze Area

    NASA Astrophysics Data System (ADS)

    Mueller-Niggemann, Cornelia; Bannert, Andrea; Schloter, Michael; Cao, Zhihong; Schwark, Lorenz

    2010-05-01

    Geobiochemical studies of rice paddy soils and their effect on the global carbon cycle are of paramount importance. Paddy soils comprise manmade wetlands because soil flooding is a prerequisite for lowland rice cultivation. Except for sulphate-rich substrates, rice growth is not very sensitive to soil conditions prevailing prior to conversion of marine tidal flat sediments to paddy cultivation. Thus, soil management practices, such as artificial submergence or drainage, ploughing and puddling (i.e. ploughing a submerged soil), manuring, liming, and fertilization, are the major driving factors of paddy soil development. Soil organic matter (SOM) decomposition and humification proceeds in hydromorphic soils at a slower rate than in well-drained, aerated soils. Rice paddy soils thus also represent a suitable model system to study fundamental aspects of redox sensitive soil processes. These processes are of special interest because in flooded rice fields the anaerobic fermentation of SOM leads to the release of methane and to denitrification losses of inorganic nitrogen. Here we present results from a chronosequence study of paddy soils with different and well known starting dates of cultivation, in the Zhejiang province (Yangtze River delta) by land reclamation through the building of protective dikes over the past 2000 years. We here describe the biomarker geochemistry of six paddy soils that developed on marine tidal sediments and where cultivation started 50, 100, 300, 700, 1000 or 2000 years before present. As reference substrates recent marine and lacustrine sediments were selected. The differentiation of the lipid biomass was achieved by investigating glycerol dialkyl glycerol tetraethers (GDGT). These specific organic geochemical biomarkers allow for determining the abundance of fossil microbial consortia (archaea and bacteria input) into paddy soils, justified by the diversity of the archaeal and bacterial cell membrane constituents. The dominant proportion of

  13. Arsenic mobilization and immobilization in paddy soils

    NASA Astrophysics Data System (ADS)

    Kappler, A.; Hohmann, C.; Zhu, Y. G.; Morin, G.

    2010-05-01

    Arsenic is oftentimes of geogenic origin and in many cases bound to iron(III) minerals. Iron(III)-reducing bacteria can harvest energy by coupling the oxidation of organic or inorganic electron donors to the reduction of Fe(III). This process leads either to dissolution of Fe(III)-containing minerals and thus to a release of the arsenic into the environment or to secondary Fe-mineral formation and immobilisation of arsenic. Additionally, aerobic and anaerobic iron(II)-oxidizing bacteria have the potential to co-precipitate or sorb arsenic during iron(II) oxidation at neutral pH that is usually followed by iron(III) mineral precipitation. We are currently investigating arsenic immobilization by Fe(III)-reducing bacteria and arsenic co-precipitation and immobilization by anaerobic iron(II)-oxidizing bacteria in batch, microcosm and rice pot experiments. Co-precipitation batch experiments with pure cultures of nitrate-dependent Fe(II)-oxidizing bacteria are used to quantify the amount of arsenic that can be immobilized during microbial iron mineral precipitation, to identify the minerals formed and to analyze the arsenic binding environment in the precipitates. Microcosm and rice pot experiments are set-up with arsenic-contaminated rice paddy soil. The microorganisms (either the native microbial population or the soil amended with the nitrate-dependent iron(II)-oxidizing Acidovorax sp. strain BoFeN1) are stimulated either with iron(II), nitrate, or oxygen. Dissolved and solid-phase arsenic and iron are quantified. Iron and arsenic speciation and redox state in batch and microcosm experiments are determined by LC-ICP-MS and synchrotron-based methods (EXAFS, XANES).

  14. Paddy soil cracks: characteristics and their impact on preferential flow

    NASA Astrophysics Data System (ADS)

    Zhang, Zhongbin; Peng, Xinhua

    2015-04-01

    Paddy soils with harrowing and puddling easily crack under alternate flooding and drying cycles (AFD). These cracks in paddy field may become pathways of preferential flow, improving water infiltration and increasing the pollution risk of groundwater. The objectives of this study were to investigate the 2D and 3D characteristics of soil cracks in paddy fields; and to determine their impacts on preferential flow. Two paddy fields, one cultivated for 20 years (YPF) and the other cultivated for more than 100 years (OPF), were subjected to either alternate flooding and drying (AFD) or continuous flooding (CF) during rice growing season. After the harvest of late rice crop, soil surface cracks were recorded using digital camera; and 3D structure of soil cracks was scanned by computed tomography (CT). The characteristics of 2D and 3D soil cracks were quantified with the aid of image analysis. The influence of soil cracks on preferential flow was characterized by tension infiltrometer, dye tracer and ion breakthrough curve. Our main results in this study were summed up as follows: under AFD condition, for the 2D soil cracks, the YPF presented 10 fold more cracks in quantity but these cracks were finer and more complicated as compared to those generated in the OPF. The results of CT scanning showed that the presence of soil cracks under the AFD increased average macropore length but decreased the number of macropores significantly, and it also changed macropore size distribution and macropore area density distribution with soil depth. The 3D structures of soil cracks were complicated but can be quantified using CT. The depth of soil cracks in young paddy field (7.58 cm) was smaller than that in old paddy field (9.34 cm), but soil cracks in both fields did not reach the plough pan (about 15 cm). Soil cracks significantly increased soil hydraulic conductivity. They serviced as pathways for preferential flow only in plow layer, as evidenced by a large dyed area above plough

  15. Arsenic bioavailability to rice is elevated in Bangladeshi paddy soils.

    PubMed

    Khan, K Asaduzzaman; Stroud, Jacqueline L; Zhu, Yong-Guan; McGrath, Steve P; Zhao, Fang-Jie

    2010-11-15

    Some paddy soils in the Bengal delta are contaminated with arsenic (As) due to irrigation of As-laden groundwater, which may lead to yield losses and elevated As transfer to the food chain. Whether these soils have a higher As bioavailability than other soils containing either geogenic As or contaminated by mining activities was investigated in a pot experiment. Fourteen soils varying in the source and the degree (4-138 mg As kg 1⁻¹) of As contamination were collected, 10 from Bangladeshi paddy fields (contaminated by irrigation water) and two each from China and the UK (geogenic or mining impacted), for comparison. Bangladeshi soils had higher percentages of the total As extractable by ammonium phosphate (specifically sorbed As) than other soils and also released more As into the porewater upon flooding. Porewater As concentrations increased with increasing soil As concentrations more steeply in Bangladeshi soils, with arsenite being the dominant As species. Rice growth and grain yield decreased markedly in Bangladeshi soils containing > 13 mg As kg 1⁻¹, but not in the other soils. Phosphate-extractable or porewater As was a better indicator of As bioavailability than total soil As. Rice straw As concentrations increased with increasing soil As concentrations; however, As phytotoxicity appeared to result in lower grain As concentrations. The relative proportions of inorganic As and dimethylarsinic acid (DMA) in grain varied among soils, and the percentage DMA was larger in greenhouse-grown plants than grain samples collected from the paddy fields of the same soil and the same rice cultivar, indicating a strong environmental influence on As species found in rice grain. This study shows that Bangladeshi paddy soils contaminated by irrigation had a higher As bioavailability than other soils, resulting in As phytotoxicity in rice and substantial yield losses. PMID:20977268

  16. Heavy Metal Pollution Enhances Soil Respiration and Reduces Carbon Storage in a Chinese Paddy Soil

    NASA Astrophysics Data System (ADS)

    Pan, Genxing; Li, Zhipeng; Liu, Yongzhuo; Smith, Pete; Crowley, David; Zheng, Jufeng

    2010-05-01

    China's paddy soils are crucial both for food security through high cereal productivity, and for climate mitigation through high soil carbon storage. These functions are increasingly threatened by widespread heavy metal pollution, resulting from rapid industrial development. Heavy metal-polluted soils generally have a reduced microbial biomass and reduced soil respiration, as well as reduced functional diversity through changes in microbial community structure. Here we show that heavy metal pollution enhances soil respiration and CO2 efflux from a Chinese rice paddy soil, and leads to a soil organic carbon (SOC) loss, which is correlated with a decline in the fungal-to-bacterial ratio of the reduced soil microbial community. The pollution-induced SOC loss could offset 70% of the yearly SOC increase from China's paddy soils. Thus, heavy metal pollution impacts long term productivity and the potential for C sequestration in China's paddy soils.

  17. Soil type-depending effect of paddy management: Organic carbon distribution and stocks

    NASA Astrophysics Data System (ADS)

    Kölbl, Angelika; Drechsler, Susanne; Wissing, Livia; Schad, Peter; Rahayu Utami, Sri; Cao, Zhihong; Kögel-Knabner, Ingrid

    2013-04-01

    Paddy soils may originate from many different types of soil but are highly modified by human activities. These soils are mostly managed under submerged conditions, a management which is assumed to favour carbon sequestration. Therefore, the present study aims to investigate the impact of paddy management on soil organic carbon distributions and stocks in major soil types that are typically used for rice cultivation in Asia. Fluvisol and Acrisol sites (sub-tropical monsoon climate, PR China) as well as Andosol, Vertisol and Ferralsol sites (tropical climate of Java, Indonesia) were compared, as they represent a large range of soil properties to be expected in Asian paddy fields. Paddy rice at all of these sites is cultivated under flooded conditions followed by an upland crop. To evaluate the impact of paddy management, paddy soils as well as adjacent agricultural soils which are not used for paddy rice production (non-paddy soils) were chosen. At each site, three soil profiles of paddy and non-paddy soils were sampled horizontally. All samples were analysed for bulk density and organic carbon (OC) concentrations, and the corresponding OC stocks were calculated. Paddy soils derived from Fluvisols and Acrisols(PR China) showed clearly higher OC concentrations in the topsoils, leading to higher cumulative OC stocks in paddy soils compared to the respective non-paddy soils. However, other soil types did not show the expected higher OC sequestration under paddy management. For example, paddy soils derived from Ferralsols and Vertisols of Java are characterised by very similar OC concentrations and OC stocks as compared to their respective non-paddy soils. Also paddy and non-paddy soils derived from Andosols (Java) showed similar OC concentrations and depth distributions; only the slightly higher bulk density values under paddy management lead to slightly higher OC stocks in these soils. As clearly shown by our results, we cannot necessarily assume that rice production

  18. [Microbial anaerobic dechlorination of polychlorinated biphenyls in paddy soil slurry].

    PubMed

    Yang, Kai; Yao, Xiao-yan; Chen, Chen; Shen, Chao-feng; Qin, Zhi-hui; Huang, Rong-lang

    2015-10-01

    We studied the dechlorination process of Aroclor1260, a high-chlorinated polychlorinated biphenyls (PCBs) mixture in an anaerobic paddy soil slurry, and further analyzed the related microbial community structures. The Aroclor1260 was reduced up to 55.5% in the natural paddy soil slurry in 128 days, and the reduction percentage dropped to 46.9% after incoculating the paddy soil slurry with a PCBs-dechlorination enrichment culture. The dechlorination mainly occurred in congeners of pentachlorobiphenyl, hexachlorobiphenyl, and specially, the heptachlorobiphenyl, with pentachlorobiphenyl accumulated as dechlorination intermediate. Hydrogen gas produced from fermentation of organic matters was maintained at a lower partial pressure due to its consumption during the dechlorination process, so that the methanogens was suppressed as well. The microbial community structure was significantly different between natural and inoculated paddy soils. Introducing the PCBs-dechlorination enrichment culture changed the local microbial community by the competition between the exogenetic dchlorinators and the indigenous bacteria, overall decreasing the dechlorination activity. PMID:26995917

  19. Soil removal as a decontamination practice and radiocesium accumulation in tadpoles in rice paddies at Fukushima.

    PubMed

    Sakai, Masaru; Gomi, Takashi; Nunokawa, Masanori; Wakahara, Taeko; Onda, Yuichi

    2014-04-01

    We investigated the biological accumulation of radiocesium in tadpoles [Rana (Pelophylax) porosa porosa] in rice paddies with and without decontamination practice at Fukushima. Radiocesium was accumulated in surface part of soils both in the control and decontaminated paddies one year after decontamination. Mean (134)Cs and (137)Cs concentrations in tadpoles in the control and decontaminated paddies were 3000 and 4500, and 600 and 890 Bq/kg dry weight, respectively. Radiocesium concentrations in surface soil (0-5 cm depth) and tadpoles in the decontaminated paddy were five times smaller than in the control paddy. These results suggest that decontamination practice can reduce radiocesium concentrations in both soil and tadpoles. However, at the decontaminated paddy, radiocesium concentrations in surface soils became 3.8 times greater one year after decontamination, which indicates that monitoring the subsequent movement of radiocesium in rice paddies and surrounding areas is essential for examining contamination propagation. PMID:24463474

  20. [Comparisons of Microbial Numbers, Biomasses and Soil Enzyme Activities Between Paddy Field and Drvland Origins in Karst Cave Wetland].

    PubMed

    Jin, Zhen-jiang; Zeng, Hong-hu; Li, Qiang; Cheng, Ya-ping; Tang, Hua-feng; Li, Min; Huang, Bing-fu

    2016-01-15

    The purpose of this study is to compare microbial number, microbial biomass as well as soil enzyme activity between paddy field and dryland originated karst wetland ecosystems. The soil samples (0-20 cm) of uncultivated wetland, paddy field and dryland were collected in Huixian karst cave wetland, Guilin, China. Microbial numbers and biomass were detected using dilute plate incubation counting and chloroform fumigation-extraction, respectively. Microbial DNA was extracted according to the manufacturer's instructions of the kit. Microbial activity was examined using soil enzyme assays as well. The result showed that the bacteria number in paddy filed was (4.36 +/- 2.25) x 10(7) CFU x g(-1), which was significantly higher than those in wetland and dryland. Fungi numbers were (6.41 +/- 2.16) x 10(4) CFU x g(-1) in rice paddy and (6.52 +/- 1.55) x 10(4) CFU x g(-1) in wetland, which were higher than that in dryland. Actinomycetes number was (2.65 +/- 0.72) x 10(6) CFU x g(-1) in dryland, which was higher than that in wetland. Microbial DNA concentration in rice paddy was (11.92 +/- 3.69) microg x g(-1), which was higher than that in dryland. Invertase activity was (66.87 +/- 18.61) mg x (g x 24 h)(-1) in rice paddy and alkaline phosphatase activity was (2.07 +/- 0.99) mg x (g x 2 h)(-1) in wetland, both of which were higher than those in dryland. Statistical analysis showed there was a significant positive correlation of microbial DNA content, alkaline phosphatase activity and microbial carbon with soil pH, soil organic carbon (SOC), total nitrogen, alkali-hydrolyzable nitrogen, soil moisture, exchangeable Ca2+ and exchangeable Mg2+, as well as a significant positive correlation of intervase activity with the former three microbial factors. The above results indicated that microbial biomass and function responded much more sensitively to land-use change than microbial number in karst cave wetland system. Soil moisture, SOC and some factors induced by land-use change

  1. Kinetic Distribution of 14C-Metsulfuron-methyl Residues in Paddy Soils under Different Moisture Conditions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Rice paddy soils undergo several cycles of drying and wetting during a growing season. A laboratory study was conducted to determine the effect of soil moisture conditions on the distribution and kinetics of extractable and bound residues of 14C-metsulfuron-methyl in six Chinese paddy soils during 8...

  2. Arsenic release from paddy soils during monsoon flooding

    NASA Astrophysics Data System (ADS)

    Roberts, Linda C.; Hug, Stephan J.; Dittmar, Jessica; Voegelin, Andreas; Kretzschmar, Ruben; Wehrli, Bernhard; Cirpka, Olaf A.; Saha, Ganesh C.; Ashraf Ali, M.; Badruzzaman, A. Borhan M.

    2010-01-01

    Bangladesh relies heavily on groundwater for the irrigation of dry-season rice. However, the groundwater used for irrigation often contains high concentrations of arsenic, potentially jeopardizing the future of rice production in the country. In seasonally flooded fields, topsoil arsenic concentrations decrease during the monsoon season, suggesting that flooding attenuates arsenic accumulation in the soils. Here we examine the chemistry of soil porewater and floodwater during the monsoon season in rice paddies in Munshiganj, Bangladesh, to assess whether flooding releases significant quantities of arsenic from the soils. We estimate that between 51 and 250mgm-2 of soil arsenic is released into floodwater during the monsoon season. This corresponds to a loss of 13-62% of the arsenic added to soils through irrigation each year. The arsenic was distributed throughout the entire floodwater column by vertical mixing and was laterally removed when the floodwater receded. We conclude that monsoon floodwater removes a large amount of the arsenic added to paddy soils through irrigation, and suggest that non-flooded soils are particularly at risk of arsenic accumulation.

  3. Phylogenetically Distinct Phylotypes Modulate Nitrification in a Paddy Soil

    PubMed Central

    Zhao, Jun; Wang, Baozhan

    2015-01-01

    Paddy fields represent a unique ecosystem in which regular flooding occurs, allowing for rice cultivation. However, the taxonomic identity of the microbial functional guilds that catalyze soil nitrification remains poorly understood. In this study, we provide molecular evidence for distinctly different phylotypes of nitrifying communities in a neutral paddy soil using high-throughput pyrosequencing and DNA-based stable isotope probing (SIP). Following urea addition, the levels of soil nitrate increased significantly, accompanied by an increase in the abundance of the bacterial and archaeal amoA gene in microcosms subjected to SIP (SIP microcosms) during a 56-day incubation period. High-throughput fingerprints of the total 16S rRNA genes in SIP microcosms indicated that nitrification activity positively correlated with the abundance of Nitrosospira-like ammonia-oxidizing bacteria (AOB), soil group 1.1b-like ammonia-oxidizing archaea (AOA), and Nitrospira-like nitrite-oxidizing bacteria (NOB). Pyrosequencing of 13C-labeled DNA further revealed that 13CO2 was assimilated by these functional groups to a much greater extent than by marine group 1.1a-associated AOA and Nitrobacter-like NOB. Phylogenetic analysis demonstrated that active AOB communities were closely affiliated with Nitrosospira sp. strain L115 and the Nitrosospira multiformis lineage and that the 13C-labeled AOA were related to phylogenetically distinct groups, including the moderately thermophilic “Candidatus Nitrososphaera gargensis,” uncultured fosmid 29i4, and acidophilic “Candidatus Nitrosotalea devanaterra” lineages. These results suggest that a wide variety of microorganisms were involved in soil nitrification, implying physiological diversification of soil nitrifying communities that are constantly exposed to environmental fluctuations in paddy fields. PMID:25724959

  4. Phylogenetically distinct phylotypes modulate nitrification in a paddy soil.

    PubMed

    Zhao, Jun; Wang, Baozhan; Jia, Zhongjun

    2015-05-01

    Paddy fields represent a unique ecosystem in which regular flooding occurs, allowing for rice cultivation. However, the taxonomic identity of the microbial functional guilds that catalyze soil nitrification remains poorly understood. In this study, we provide molecular evidence for distinctly different phylotypes of nitrifying communities in a neutral paddy soil using high-throughput pyrosequencing and DNA-based stable isotope probing (SIP). Following urea addition, the levels of soil nitrate increased significantly, accompanied by an increase in the abundance of the bacterial and archaeal amoA gene in microcosms subjected to SIP (SIP microcosms) during a 56-day incubation period. High-throughput fingerprints of the total 16S rRNA genes in SIP microcosms indicated that nitrification activity positively correlated with the abundance of Nitrosospira-like ammonia-oxidizing bacteria (AOB), soil group 1.1b-like ammonia-oxidizing archaea (AOA), and Nitrospira-like nitrite-oxidizing bacteria (NOB). Pyrosequencing of 13C-labeled DNA further revealed that 13CO2 was assimilated by these functional groups to a much greater extent than by marine group 1.1a-associated AOA and Nitrobacter-like NOB. Phylogenetic analysis demonstrated that active AOB communities were closely affiliated with Nitrosospira sp. strain L115 and the Nitrosospira multiformis lineage and that the 13C-labeled AOA were related to phylogenetically distinct groups, including the moderately thermophilic "Candidatus Nitrososphaera gargensis," uncultured fosmid 29i4, and acidophilic "Candidatus Nitrosotalea devanaterra" lineages. These results suggest that a wide variety of microorganisms were involved in soil nitrification, implying physiological diversification of soil nitrifying communities that are constantly exposed to environmental fluctuations in paddy fields. PMID:25724959

  5. [Straw return to rice paddy: soil carbon sequestration and increased methane emission].

    PubMed

    Lu, Fei; Wang, Xiao-Ke; Han, Bing; Ouyang, Zhi-Yun; Zheng, Hua

    2010-01-01

    Based on the long-term datasets of soil organic matter content and the observation data of rice paddies' methane (CH4) emission collected from the agricultural experiment stations across the country, the rice paddies in China were divided into single cropping and double cropping regions. The soil carbon sequestration potential of straw return in three types of rice paddies in the two regions, i. e., single cropping rice paddies, upland/paddy alternated rice paddies, and double cropping rice paddies, was evaluated, based on the datasets of soil organic matter content; and the total CH4 emission from rice paddies without straw return was estimated, with reference to the experimental data of paddies' CH4 emission and by the method of mean emission coefficient. The total CH4 emission from our paddies after straw return and the global warming potential of the increased CH4 emission were also estimated by using the related methods and parameters given by IPCC. It was estimated that the full popularization of straw return to China's rice paddies would sequester 10.48 Tg x a(-1) of C, and the contribution to the global warming mitigation was 38.43 Tg CO2-eqv x a(-1). In the meanwhile, the CH4 emission from our rice paddies would be increased from 5.796 Tg x a(-1) to 9.114 Tg x a(-1), and the increased 3.318 Tg x a(-1) of CH4 emission would lead to a global warming potential of 82.95 Tg CO2 -eqv x a(-1), which was 2.158 times of the mitigation from carbon sequestration in rice paddies. Therefore, the increased CH4 emission due to straw return should be regarded as an important greenhouse gas leakage, since it could greatly offset the mitigation benefits of soil carbon sequestration in China's rice paddies. PMID:20387430

  6. Microbial communities play important roles in modulating paddy soil fertility

    NASA Astrophysics Data System (ADS)

    Luo, Xuesong; Fu, Xiaoqian; Yang, Yun; Cai, Peng; Peng, Shaobing; Chen, Wenli; Huang, Qiaoyun

    2016-02-01

    We studied microbial communities in two paddy soils, which did not receive nitrogen fertilization and were distinguished by the soil properties. The two microbial communities differed in the relative abundance of gram-negative bacteria and total microbial biomass. Variability in microbial communities between the two fields was related to the levels of phosphorus and soil moisture. Redundancy analysis for individual soils showed that the bacterial community dynamics in the high-yield soil were significantly correlated with total carbon, moisture, available potassium, and pH, and those in the low-yield cores were shaped by pH, and nitrogen factors. Biolog Eco-plate data showed a more active microbial community in the high yield soil. The variations of enzymatic activities in the two soils were significantly explained by total nitrogen, total potassium, and moisture. The enzymatic variability in the low-yield soil was significantly explained by potassium, available nitrogen, pH, and total carbon, and that in the high-yield soil was partially explained by potassium and moisture. We found the relative abundances of Gram-negative bacteria and Actinomycetes partially explained the spatial and temporal variations of soil enzymatic activities, respectively. The high-yield soil microbes are probably more active to modulate soil fertility for rice production.

  7. Microbial communities play important roles in modulating paddy soil fertility

    PubMed Central

    Luo, Xuesong; Fu, Xiaoqian; Yang, Yun; Cai, Peng; Peng, Shaobing; Chen, Wenli; Huang, Qiaoyun

    2016-01-01

    We studied microbial communities in two paddy soils, which did not receive nitrogen fertilization and were distinguished by the soil properties. The two microbial communities differed in the relative abundance of gram-negative bacteria and total microbial biomass. Variability in microbial communities between the two fields was related to the levels of phosphorus and soil moisture. Redundancy analysis for individual soils showed that the bacterial community dynamics in the high-yield soil were significantly correlated with total carbon, moisture, available potassium, and pH, and those in the low-yield cores were shaped by pH, and nitrogen factors. Biolog Eco-plate data showed a more active microbial community in the high yield soil. The variations of enzymatic activities in the two soils were significantly explained by total nitrogen, total potassium, and moisture. The enzymatic variability in the low-yield soil was significantly explained by potassium, available nitrogen, pH, and total carbon, and that in the high-yield soil was partially explained by potassium and moisture. We found the relative abundances of Gram-negative bacteria and Actinomycetes partially explained the spatial and temporal variations of soil enzymatic activities, respectively. The high-yield soil microbes are probably more active to modulate soil fertility for rice production. PMID:26841839

  8. Heavy metals accumulation in parts of paddy Oryza sativa L. grown in paddy field adjacent to ultrabasic soil

    NASA Astrophysics Data System (ADS)

    Hadif, Waqeed Mahdi; Rahim, Sahibin Abd; Sahid, Ismail; Bhuiyan, Atiqur Rahman; Ibrahim, Izyanti

    2015-09-01

    The present study was carried out to evaluate the accumulation and translocation of heavy metals from soil around the root zone to various parts of the paddy plant, namely the roots, stems, leaves and rice grains. This study was conducted in 2014 in paddy field adjacent to ultrabasic soil (field 1 and 2) located in Ranau, Sabah and one field (Field 3) taken as control located at the UKM experimental plot in peninsular of Malaysia. The plant species used in the present investigation is Paddy Batu. The heavy metals studied were Chromium (Cr), Iron (Fe) and Nickel (Ni). Heavy metals in soil and plant were extracted by wet digestion method. Heavy metals present in paddy plants and soils extract were measured using the ICP-MS. Heavy metals concentrations in the plant parts in descending order is the root > leaves > stem > rice grain. Lower concentration of all heavy metals in soils and plant parts was shown by the control site (Field 3) in UKM Bangi. Higher concentration of heavy metals occurred in the roots compared to other above ground parts (stem, leaves, and grains) of the paddy plant in all of the paddy field. The bioaccumulation factor (BAF) of heavy metals in all locations were recorded in descending order as Ni > Cr > Fe, the BAF values for all metals in the rice grains were low, whereas the BAF values were recorded high for Ni in all locations. The results also showed that Fe was the most predominant metal ion in the roots, followed by Ni then Cr.

  9. Phosphorus content as a function of soil aggregate size and paddy cultivation in highly weathered soils.

    PubMed

    Li, Baozhen; Ge, Tida; Xiao, Heai; Zhu, Zhenke; Li, Yong; Shibistova, Olga; Liu, Shoulong; Wu, Jinshui; Inubushi, Kazuyuki; Guggenberger, Georg

    2016-04-01

    Red soils are the major land resource in subtropical and tropical areas and are characterized by low phosphorus (P) availability. To assess the availability of P for plants and the potential stability of P in soil, two pairs of subtropical red soil samples from a paddy field and an adjacent uncultivated upland were collected from Hunan Province, China. Analysis of total P and Olsen P and sequential extraction was used to determine the inorganic and organic P fractions in different aggregate size classes. Our results showed that the soil under paddy cultivation had lower proportions of small aggregates and higher proportions of large aggregates than those from the uncultivated upland soil. The portion of >2-mm-sized aggregates increased by 31 and 20 % at Taoyuan and Guiyang, respectively. The total P and Olsen P contents were 50-150 and 50-300 % higher, respectively, in the paddy soil than those in the upland soil. Higher inorganic and organic P fractions tended to be enriched in both the smallest and largest aggregate size classes compared to the middle size class (0.02-0.2 mm). Furthermore, the proportion of P fractions was higher in smaller aggregate sizes (<2 mm) than in the higher aggregate sizes (>2 mm). In conclusion, soils under paddy cultivation displayed improved soil aggregate structure, altered distribution patterns of P fractions in different aggregate size classes, and to some extent had enhanced labile P pools. PMID:26728283

  10. Arsenic speciation in rice paddy soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arsenic can undergo several chemical and microbial transformations in soil, including oxidation/reduction, methylation/demethylation, and volatilization, which could impact arsenic bioavailability for plant uptake. An experiment was conducted in field plots at Stuttgart, AR to determine whether arse...

  11. CADMIUM SOLUBILITY IN PADDY SOILS: EFFECTS OF SOIL OXIDATION, METAL SULFIDES AND COMPETITIVE IONS.

    EPA Science Inventory

    Cadmium (Cd) is a non-essential element for human nutrition and is an agricultural soil contaminant. Cadmium solubility in paddy soils affects Cd accumulation in the grain of rice. This is a human health risk, exacerbated by the fact that rice grains are deficient in iron (Fe) an...

  12. Effects of sulfur in flooded paddy soils: Implications for iron chemistry and arsenic mobilization

    NASA Astrophysics Data System (ADS)

    Avancha, S.; Boye, K.

    2013-12-01

    In the Mekong delta in Cambodia, naturally occurring arsenic (amplified by erosion in the Himalaya Mountains) in paddy soils is mobilized during the seasonal flooding. As a consequence, rice grown on the flooded soils may take up arsenic and expose people eating the rice to this carcinogenic substance. Iron and sulfur both interact strongly with arsenic in paddy soils: iron oxides are strong adsorbents for arsenic in oxic conditions, and sulfur (in the form of sulfide) is a strong adsorbent under anoxic conditions. In the process of reductive dissolution of iron oxides, arsenic, which had been adsorbed to the iron oxides, is released. Therefore, higher levels of reduced iron (ferrous iron) will likely correlate with higher levels of mobilized arsenic. However, the mobilized arsenic may then co-precipitate with or adsorb to iron sulfides, which form under sulfate-reducing conditions and with the aid of certain microbes already present in the soil. In a batch experiment, we investigated how these processes correlate and which has the greatest influence on arsenic mobilization and potential plant availability. The experiment was designed to measure the effects of various sources of sulfur (dried rice straw, charred rice straw, and gypsum) on the iron and arsenic release in an arsenic-contaminated paddy soil from Cambodia under flooded conditions. The two types of rice straw were designed to introduce the same amount of organic sulfur (7.7 μg/g of soil), but different levels of available carbon, since carbon stimulates microbial activity in the soil. In comparison, two different levels of gypsum (calcium sulfate) were used, 7.7 and 34.65 μg/g of soil, to test the effect of directly available inorganic sulfate without carbon addition. The soil was flooded with a buffer solution at pH 7.07 in airtight serum vials and kept as a slurry on a shaker at 25 °C. We measured pH, alkalinity, ferrous iron, ferric iron, sulfide, sulfate, total iron, sulfur, and arsenic in the

  13. Solubility and Leaching Risks of Organic Carbon in Paddy Soils as Affected by Irrigation Managements

    PubMed Central

    Yang, Shihong; Wei, Qi; Gao, Xiaoli

    2013-01-01

    Influence of nonflooding controlled irrigation (NFI) on solubility and leaching risk of soil organic carbon (SOC) were investigated. Compared with flooding irrigation (FI) paddies, soil water extractable organic carbon (WEOC) and dissolved organic carbon (DOC) in NFI paddies increased in surface soil but decreased in deep soil. The DOC leaching loss in NFI field was 63.3 kg C ha−1, reduced by 46.4% than in the FI fields. It indicated that multi-wet-dry cycles in NFI paddies enhanced the decomposition of SOC in surface soils, and less carbon moved downward to deep soils due to less percolation. That also led to lower SOC in surface soils in NFI paddies than in FI paddies, which implied that more carbon was released into the atmosphere from the surface soil in NFI paddies. Change of solubility of SOC in NFI paddies might lead to potential change in soil fertility and sustainability, greenhouse gas emission, and bioavailability of trace metals or organic pollutants. PMID:23935423

  14. A Simple Evaluation of Soil Quality of Waterlogged Purple Paddy Soils with Different Productivities

    PubMed Central

    Liu, Zhanjun; Zhou, Wei; Lv, Jialong; He, Ping; Liang, Guoqing; Jin, Hui

    2015-01-01

    Evaluation of soil quality can be crucial for designing efficient farming systems and ensuring sustainable agriculture. The present study aimed at evaluating the quality of waterlogged purple paddy soils with different productivities in Sichuan Basin. The approach involved comprehensive analyses of soil physical and chemical properties, as well as enzyme activities and microbial community structure measured by phospholipid fatty acid analysis (PLFA). A total of 36 soil samples were collected from four typical locations, with 12 samples representing high productivity purple paddy soil (HPPS), medium productivity purple paddy soil (MPPS) and low productivity purple paddy soil (LPPS), respectively. Most measured soil properties showed significant differences (P ≤ 0.05) among HPPS, MPPS and LPPS. Pearson correlation analysis and principal component analysis were used to identify appropriate soil quality indicators. A minimum data set (MDS) including total nitrogen (TN), available phosphorus (AP), acid phosphatase (ACP), total bacteria (TB) and arbuscular mycorrhizal fungi was established and accounted for 82.1% of the quality variation among soils. A soil quality index (SQI) was developed based on the MDS method, whilst HPPS, MPPS and LPPS received mean SQI scores of 0.725, 0.536 and 0.425, respectively, with a ranking of HPPS > MPPS > LPPS. HPPS showed relatively good soil quality characterized by optimal nutrient availability, enzymatic and microbial activities, but the opposite was true of LPPS. Low levels of TN, AP and soil microbial activities were considered to be the major constraints limiting the productivity in LPPS. All soil samples collected were rich in available N, K, Si and Zn, but deficient in available P, which may be the major constraint for the studied regions. Managers in our study area should employ more appropriate management in the LPPS to improve its rice productivity, and particularly to any potential limiting factor. PMID:25997107

  15. Differential assemblage of functional units in paddy soil microbiomes.

    PubMed

    Kim, Yongkyu; Liesack, Werner

    2015-01-01

    Flooded rice fields are not only a global food source but also a major biogenic source of atmospheric methane. Using metatranscriptomics, we comparatively explored structural and functional succession of paddy soil microbiomes in the oxic surface layer and anoxic bulk soil. Cyanobacteria, Fungi, Xanthomonadales, Myxococcales, and Methylococcales were the most abundant and metabolically active groups in the oxic zone, while Clostridia, Actinobacteria, Geobacter, Anaeromyxobacter, Anaerolineae, and methanogenic archaea dominated the anoxic zone. The protein synthesis potential of these groups was about 75% and 50% of the entire community capacity, respectively. Their structure-function relationships in microbiome succession were revealed by classifying the protein-coding transcripts into core, non-core, and taxon-specific transcripts based on homologous gene distribution. The differential expression of core transcripts between the two microbiomes indicated that structural succession is primarily governed by the cellular ability to adapt to the given oxygen condition, involving oxidative stress, nitrogen/phosphorus metabolism, and fermentation. By contrast, the non-core transcripts were expressed from genes involved in the metabolism of various carbon sources. Among those, taxon-specific transcripts revealed highly specialized roles of the dominant groups in community-wide functioning. For instance, taxon-specific transcripts involved in photosynthesis and methane oxidation were a characteristic of the oxic zone, while those related to methane production and aromatic compound degradation were specific to the anoxic zone. Degradation of organic matters, antibiotics resistance, and secondary metabolite production were detected to be expressed in both the oxic and anoxic zones, but by different taxonomic groups. Cross-feeding of methanol between members of the Methylococcales and Xanthomonadales was suggested by the observation that in the oxic zone, they both

  16. Evaluation of soil quality indicators in paddy soils under different crop rotation systems

    NASA Astrophysics Data System (ADS)

    Nadimi-Goki, Mandana; Bini, Claudio; Haefele, Stephan; Abooei, Monireh

    2013-04-01

    Evaluation of soil quality indicators in paddy soils under different crop rotation systems Soil quality, by definition, reflects the capacity to sustain plant and animal productivity, maintain or enhance water and air quality, and promote plant and animal health. Soil quality assessment is an essential issue in soil management for agriculture and natural resource protection. This study was conducted to detect the effects of four crop rotation systems (rice-rice-rice, soya-rice-rice, fallow-rice and pea-soya-rice) on soil quality indicators (soil moisture, porosity, bulk density, water-filled pore space, pH, extractable P, CEC, OC, OM, microbial respiration, active carbon) in paddy soils of Verona area, Northern Italy. Four adjacent plots which managed almost similarly, over five years were selected. Surface soil samples were collected from each four rotation systems in four times, during growing season. Each soil sample was a composite of sub-samples taken from 3 points within 350 m2 of agricultural land. A total of 48 samples were air-dried and passed through 2mm sieve, for some chemical, biological, and physical measurements. Statistical analysis was done using SPSS. Statistical results revealed that frequency distribution of most data was normal. The lowest CV% was related to pH. Analysis of variance (ANOVA) and comparison test showed that there are significant differences in soil quality indicators among crop rotation systems and sampling times. Results of multivariable regression analysis revealed that soil respiration had positively correlation coefficient with soil organic matter, soil moisture and cation exchange capacity. Overall results indicated that the rice rotation with legumes such as bean and soybean improved soil quality over a long time in comparison to rice-fallow rotation, and this is reflected in rice yield. Keywords: Soil quality, Crop Rotation System, Paddy Soils, Italy

  17. Fly ash application in nutrient poor agriculture soils: impact on methanotrophs population dynamics and paddy yields.

    PubMed

    Singh, Jay Shankar; Pandey, Vimal Chandra

    2013-03-01

    There are reports that the application of fly ash, compost and press mud or a combination thereof, improves plant growth, soil microbial communities etc. Also, fly ash in combination with farmyard manure or other organic amendments improves soil physico-chemical characteristics, rice yield and microbial processes in paddy fields. However, the knowledge about the impact of fly ash inputs alone or in combination with other organic amendments on soil methanotrophs number in paddy soils is almost lacking. We hypothesized that fly ash application at lower doses in paddy agriculture soil could be a potential amendment to elevate the paddy yields and methanotrophs number. Here we demonstrate the impact of fly ash and press mud inputs on number of methanotrophs, antioxidants, antioxidative enzymatic activities and paddy yields at agriculture farm. The impact of amendments was significant for methanotrophs number, heavy metal concentration, antioxidant contents, antioxidant enzymatic activities and paddy yields. A negative correlation was existed between higher doses of fly ash-treatments and methanotrophs number (R(2)=0.833). The content of antioxidants and enzymatic activities in leaves of higher doses fly ash-treated rice plants increased in response to stresses due to heavy metal toxicity, which was negatively correlated with rice grain yield (R(2)=0.944) and paddy straw yield (R(2)=0.934). A positive correlation was noted between heavy metals concentrations and different antioxidant and enzymatic activities across different fly ash treated plots.The data of this study indicate that heavy metal toxicity of fly ash may cause oxidative stress in the paddy crop and the antioxidants and related enzymes could play a defensive role against phytotoxic damages. We concluded that fly ash at lower doses with press mud seems to offer the potential amendments to improving soil methanotrophs population and paddy crop yields for the nutrient poor agriculture soils. PMID:23260239

  18. Uncultivated Methylocystis Species in Paddy Soil Include Facultative Methanotrophs that Utilize Acetate.

    PubMed

    Leng, Lingqin; Chang, Jiali; Geng, Kan; Lu, Yahai; Ma, Ke

    2015-07-01

    Methanotrophs are crucial in regulating methane emission from rice field systems. Type II methanotrophs in particular are often observed in high abundance in paddy soil. Some cultivated species of Methylocystis are able to grow on acetate in the absence of methane. We hypothesize that the dominant type II methanotrophs in paddy soil might facultatively utilize acetate for growth, which we evaluate in the present study. The measurement of methane oxidation rates showed that the methanotrophic activity in paddy soil was inhibited by the addition of acetate compared to the continuous supplementation of methane, but the paddy soil maintained the methane oxidation capacity and recovered following methane supplementation. Terminal restriction fragment length polymorphism analysis (T-RFLP) combined with cloning and sequencing of pmoA genes showed that Methylocystis was enriched after incubation with added acetate, while the type I methanotrophs Methylocaldum/Methylococcus and Methylobacter were enriched by methane supplementation. A comparison of pmoA sequences obtained in this study with those in the public database indicated that they were globally widespread in paddy soils or in associated with rice roots. Furthermore, we performed stable isotope probing (SIP) of pmoA messenger RNA (mRNA) to investigate the assimilation of (13)C-acetate by paddy soil methanotrophs. RNA-SIP revealed that Methylocystis-related methanotrophs which shared the same genotype of the above enriched species were significantly labelled. It indicates that these methanotrophs actively assimilated the labelled acetate in paddy soil. Altogether, these results suggested that uncultivated Methylocystis species are facultative methanotrophs utilizing acetate as a secondary carbon source in paddy soil. PMID:25475784

  19. Microbial phototrophic fixation of atmospheric CO2 in China subtropical upland and paddy soils

    NASA Astrophysics Data System (ADS)

    Ge, Tida; Wu, Xiaohong; Chen, Xiaojuan; Yuan, Hongzhao; Zou, Ziying; Li, Baozhen; Zhou, Ping; Liu, Shoulong; Tong, Chengli; Brookes, Phil; Wu, Jinshui

    2013-07-01

    Autotrophic microorganisms, which can fix atmospheric CO2 to synthesize organic carbon, are numerous and widespread in soils. However, the extent and the mechanism of CO2 fixation in soils remain poorly understood. We incubated five upland and five paddy soils from subtropical China in an enclosed, continuously 14CO2-labeled, atmosphere and measured 14CO2 incorporated into soil organic matter (SOC14) and microbial biomass (MBC14) after 110 days. The five upland soils supported dominant crops soils (maize, wheat, sweet potato, and rapeseed) in the region, while all paddy soils were cultivated in a regime consisting of permanently-flooded double-cropping rice cultivation. The upland and paddy soils represented typical soil types (fluvisols and ultisols) and three landforms (upland, hill, and low mountain), ranging in total carbon from low (<10 g kg-1 soil organic carbon) to medium (10-20 g kg-1) to high (>20 g kg-1). Substantial amounts of 14CO2 were fixed into SOC14 (mean 20.1 ± 7.1 mg C kg-1 in upland soil, 121.1 ± 6.4 mg C kg-1 in paddy soil) in illuminated soils (12 h light/12 h dark), whereas no 14C was fixed in soils incubated in continuous darkness. We concluded that the microbial CO2 fixation was almost entirely phototrophic rather than chemotrophic. The rate of SOC14 synthesis was significantly higher in paddy soils than in upland soils. The SOC14 comprised means of 0.15 ± 0.01% (upland) and 0.65 ± 0.03% (paddy) of SOC. The extent of 14C immobilized as MBC14 and that present as dissolved organic C (DOC14) differed between soil types, accounting for 15.69-38.76% and 5.54-18.37% in upland soils and 15.57-40.03% and 3.67-7.17% of SOC14 in paddy soils, respectively. The MBC14/MBC and DOC14/DOC were 1.76-5.70% and 1.69-5.17% in the upland soils and 4.23-28.73% and 5.65-14.30% in the paddy soils, respectively. Thus, the newly-incorporated C stimulated the dynamics of DOC and MBC more than the dynamics of SOC. The SOC14 and MBC14 concentrations were highly

  20. Inhibition experiments on nitrous oxide emission from paddy soils

    NASA Astrophysics Data System (ADS)

    Xu, Xingkai; Boeckx, Pascal; Zhou, Likai; Van Cleemput, Oswald

    2002-08-01

    Rice fields using nitrogen-based fertilizers play an important role in the global N2O budget. However, our knowledge is still limited with regard to the mechanisms affecting the N2O emission and to the measures that can reduce the emission. This paper reports a study of N2O emission from paddy soils. The effects of urea, hydroquinone (HQ, a urease inhibitor), and dicyandiamide (DCD, a nitrification inhibitor) have been studied in pot experiments with and without rice plants and with and without addition of wheat straw. With no wheat straw amendment, all treatments with inhibitors, especially with HQ + DCD, had a much smaller N2O emission during the rice growing period than the urea treatment, whereas a substantially increased N2O emission was observed from a rice-free soil with inhibitors. The N2O emission from the rice-planted soil was exponentially positive correlated with the NO3--N concentration in the rice aboveground biomass. By comparing the total N2O emission from the rice-free soil and from the rice-planted soil, we found that urea application alone might induce an apparent plant-mediated N2O emission, being 0.39 +/- 0.08% of the applied urea N. Wheat straw incorporated into the flooded surface layer soil could increase the plant-mediated N2O emission significantly. However, application of HQ + DCD could reduce this emission (0.27 +/- 0.08% of the applied urea N, compared with 0.89 +/- 0.18% in the urea treatment). It also reduced the N2O emission from the rice-free soil and from the rice-planted soil. Stepwise regression analysis indicates that denitrification in the flooded surface layer soil was the main source of N2O emission from this wetland rice cultivation, particularly when wheat straw was added. A significantly nonlinear negative relation was found between the N2O emission and the CH4 emission when no wheat straw was added, but it was hard to quantify this trade-off relation when wheat straw was incorporated into the flooded surface layer soil.

  1. Downward carbon transport in a 2000-year rice paddy soil chronosequence traced by radiocarbon measurements

    NASA Astrophysics Data System (ADS)

    Bräuer, T.; Grootes, P. M.; Nadeau, M.-J.; Andersen, N.

    2013-01-01

    Paddy and non-paddy soils from a chronosequence of 50-2000 years of agricultural use, developed on former estuarine sediments of the Yangtze River, were sampled near Cixi, Zhejiang Province, China, in the framework of the Research Unit “Biogeochemistry of paddy soil evolution” of the German Research Foundation (DFG). In addition samples of Yangtze River estuarine sediments were obtained. The parent sediment shows a fairly homogeneous composition with ca. 0.3% TOC and a 14C concentration of ca. 50 pMC. After being diked-in, gradients in soil organic carbon and 14C concentration develop under the influence of vegetation and cultivation. In the non-paddy soil, a 14C gradient with concentration decreasing with increasing depth from modern (>100 pMC) to original sediment values around 50 pMC is already established after 50 years and can also be observed in the older sites. In contrast, the 50 years old paddy soil shows organic carbon and 14C enrichment only in the A-horizon and a nearly constant TOC and 14C stock of original sediment below the plough pan. To test the basic approach that the soil profile development started on homogeneous sediment, an isotope and mass balance calculation was used. The results show a quite similar age composition of different sample sites. Paddy rice cultivation quickly leads to a dense plough pan, which seriously reduces, but not totally prevents, downward transport of organic matter. The equilibrium times for TOC and 14C in paddy soil profiles are short (decades) in the topsoil and in the order of centuries in the subsoil, underlining the dynamic character of soil organic carbon.

  2. Two-year stability of immobilization effect of sepiolite on Cd contaminants in paddy soil.

    PubMed

    Liang, Xuefeng; Xu, Yi; Xu, Yingming; Wang, Pengchao; Wang, Lin; Sun, Yuebing; Huang, Qingqing; Huang, Rong

    2016-07-01

    The long-term stability of immobilization effect of immobilization agents was critical to the remediation practices. Two years consecutive in situ field-scale demonstration was conducted in Hunan province, with the purpose to certify the long-term stability of immobilization effect of sepiolite on Cd contaminants in paddy soil in the aspect of soil extraction and plant uptake. Natural sepiolite was selected as immobilization, and rice was the model plant. The immobilization effect of sepiolite on Cd contaminants in paddy soil was significant in the first year and remained at the second year. The Cd content of brown rice, 0.025 M HCl extractable Cd content and exchangeable Cd content of paddy soil decreased remarkably. The application of sepiolite led to an obvious increase in pH value of paddy soil and carbonate bounded fraction of Cd in soil. The immobilization effect was maintained even at the second year without any additional amendments. The results indicated the interaction of sepiolite and cadmium was a long-term process. The additional sepiolite at the second year had no significant lift effect on immobilization so that it was unnecessary to add sepiolite every year based on the immobilization effect and operation cost. The dynamics of available Cu, Zn, and Mn contents in paddy soil in two consecutive years indicated sepiolite had negligible effects on the bioavailability of trace metals. The result of the current research confirmed the stability of immobilization effect of sepiolite. PMID:26993515

  3. Effects of Land Use Changes from Paddy Fields on Soil Bacterial Communities in a Hilly and Mountainous Area

    PubMed Central

    Rokunuzzaman, Md; Ueda, Yumiko; Chen, Li; Tanaka, Sota; Ohnishi, Kouhei

    2016-01-01

    Soil bacterial community structures in terraced rice fields and abandoned lands in a hilly and mountainous area were analyzed using 16S rRNA gene sequences. The DGGE band patterns of each soil were similar. Based on pyrosequencing data, the richness and diversity of bacterial species were slightly higher in paddy fields than in other soils. A beta-diversity analysis clearly indicated that the bacterial community structure in paddy fields differed from those in non-paddy field lands and crop fields that had not been used as a paddy field. These results may reflect the history of land use. PMID:27098398

  4. Diversity and abundance of arsenic biotransformation genes in paddy soils from southern China.

    PubMed

    Zhang, Si-Yu; Zhao, Fang-Jie; Sun, Guo-Xin; Su, Jian-Qiang; Yang, Xiao-Ru; Li, Hu; Zhu, Yong-Guan

    2015-04-01

    Microbe-mediated arsenic (As) biotransformation in paddy soils determines the fate of As in soils and its availability to rice plants, yet little is known about the microbial communities involved in As biotransformation. Here, we revealed wide distribution, high diversity, and abundance of arsenite (As(III)) oxidase genes (aioA), respiratory arsenate (As(V)) reductase genes (arrA), As(V) reductase genes (arsC), and As(III) S-adenosylmethionine methyltransferase genes (arsM) in 13 paddy soils collected across Southern China. Sequences grouped with As biotransformation genes are mainly from rice rhizosphere bacteria, such as some Proteobacteria, Gemmatimonadales, and Firmicutes. A significant correlation of gene abundance between arsC and arsM suggests that the two genes coexist well in the microbial As resistance system. Redundancy analysis (RDA) indicated that soil pH, EC, total C, N, As, and Fe, C/N ratio, SO4(2-)-S, NO3(-)-N, and NH4(+)-N were the key factors driving diverse microbial community compositions. This study for the first time provides an overall picture of microbial communities involved in As biotransformation in paddy soils, and considering the wide distribution of paddy fields in the world, it also provides insights into the critical role of paddy fields in the As biogeochemical cycle. PMID:25738639

  5. Mitigating methane emission from paddy soil with rice-straw biochar amendment under projected climate change.

    PubMed

    Han, Xingguo; Sun, Xue; Wang, Cheng; Wu, Mengxiong; Dong, Da; Zhong, Ting; Thies, Janice E; Wu, Weixiang

    2016-01-01

    Elevated global temperatures and increased concentrations of carbon dioxide (CO2) in the atmosphere associated with climate change will exert profound effects on rice cropping systems, particularly on their greenhouse gas emitting potential. Incorporating biochar into paddy soil has been shown previously to reduce methane (CH4) emission from paddy rice under ambient temperature and CO2. We examined the ability of rice straw-derived biochar to reduce CH4 emission from paddy soil under elevated temperature and CO2 concentrations expected in the future. Adding biochar to paddy soil reduced CH4 emission under ambient conditions and significantly reduced emissions by 39.5% (ranging from 185.4 mg kg(-1) dry weight soil, dws season(-1) to 112.2 mg kg(-1) dws season(-1)) under simultaneously elevated temperature and CO2. Reduced CH4 release was mainly attributable to the decreased activity of methanogens along with the increased CH4 oxidation activity and pmoA gene abundance of methanotrophs. Our findings highlight the valuable services of biochar amendment for CH4 control from paddy soil in a future that will be shaped by climate change. PMID:27090814

  6. Mitigating methane emission from paddy soil with rice-straw biochar amendment under projected climate change

    NASA Astrophysics Data System (ADS)

    Han, Xingguo; Sun, Xue; Wang, Cheng; Wu, Mengxiong; Dong, Da; Zhong, Ting; Thies, Janice E.; Wu, Weixiang

    2016-04-01

    Elevated global temperatures and increased concentrations of carbon dioxide (CO2) in the atmosphere associated with climate change will exert profound effects on rice cropping systems, particularly on their greenhouse gas emitting potential. Incorporating biochar into paddy soil has been shown previously to reduce methane (CH4) emission from paddy rice under ambient temperature and CO2. We examined the ability of rice straw-derived biochar to reduce CH4 emission from paddy soil under elevated temperature and CO2 concentrations expected in the future. Adding biochar to paddy soil reduced CH4 emission under ambient conditions and significantly reduced emissions by 39.5% (ranging from 185.4 mg kg‑1 dry weight soil, dws season‑1 to 112.2 mg kg‑1 dws season‑1) under simultaneously elevated temperature and CO2. Reduced CH4 release was mainly attributable to the decreased activity of methanogens along with the increased CH4 oxidation activity and pmoA gene abundance of methanotrophs. Our findings highlight the valuable services of biochar amendment for CH4 control from paddy soil in a future that will be shaped by climate change.

  7. Mitigating methane emission from paddy soil with rice-straw biochar amendment under projected climate change

    PubMed Central

    Han, Xingguo; Sun, Xue; Wang, Cheng; Wu, Mengxiong; Dong, Da; Zhong, Ting; Thies, Janice E.; Wu, Weixiang

    2016-01-01

    Elevated global temperatures and increased concentrations of carbon dioxide (CO2) in the atmosphere associated with climate change will exert profound effects on rice cropping systems, particularly on their greenhouse gas emitting potential. Incorporating biochar into paddy soil has been shown previously to reduce methane (CH4) emission from paddy rice under ambient temperature and CO2. We examined the ability of rice straw-derived biochar to reduce CH4 emission from paddy soil under elevated temperature and CO2 concentrations expected in the future. Adding biochar to paddy soil reduced CH4 emission under ambient conditions and significantly reduced emissions by 39.5% (ranging from 185.4 mg kg−1 dry weight soil, dws season−1 to 112.2 mg kg−1 dws season−1) under simultaneously elevated temperature and CO2. Reduced CH4 release was mainly attributable to the decreased activity of methanogens along with the increased CH4 oxidation activity and pmoA gene abundance of methanotrophs. Our findings highlight the valuable services of biochar amendment for CH4 control from paddy soil in a future that will be shaped by climate change. PMID:27090814

  8. Cadmium solubility in paddy soils: effects of soil oxidation, metal sulfides and competitive ions.

    PubMed

    de Livera, Jennifer; McLaughlin, Mike J; Hettiarachchi, Ganga M; Kirby, Jason K; Beak, Douglas G

    2011-03-15

    Cadmium (Cd) is a non-essential element for human nutrition and is an agricultural soil contaminant. Cadmium solubility in paddy soils affects Cd accumulation in the grain of rice. This is a human health risk, exacerbated by the fact that rice grains are deficient in iron (Fe) and zinc (Zn) for human nutrition. To find ways of limiting this potential risk, we investigated factors influencing Cd solubility relative to Fe and Zn during pre-harvest drainage of paddy soils, in which soil oxidation is accompanied by the grain-filling stage of rice growth. This was simulated in temperature-controlled "reaction cell" experiments by first excluding oxygen to incubate soil suspensions anaerobically, then inducing aerobic conditions. In treatments without sulfur addition, the ratios of Cd:Fe and Cd:Zn in solution increased during the aerobic phase while Cd concentrations were unaffected and the Fe and Zn concentrations decreased. However, in treatments with added sulfur (as sulfate), up to 34 % of sulfur (S) was precipitated as sulfide minerals during the anaerobic phase and the Cd:Fe and Cd:Zn ratios in solution during the aerobic phase were lower than for treatments without S addition. When S was added, Cd solubility decreased whereas Fe and Zn were unaffected. When soil was spiked with Zn the Cd:Zn ratio was lower in solution during the aerobic phase, due to higher Zn concentrations. Decreased Cd:Fe and Cd:Zn ratios during the grain filling stage could potentially limit Cd enrichment in paddy rice grain due to competitive ion effects for root uptake. PMID:21277005

  9. Microprofiling of nitrogen patches in paddy soil: Analysis of spatiotemporal nutrient heterogeneity at the microscale.

    PubMed

    Li, Yilin; Kronzucker, Herbert J; Shi, Weiming

    2016-01-01

    Flooded paddy soil ecosystems in the tropics support the cultivation of the majority of the world's leading crop, rice, and nitrogen (N) availability in the paddy-soil rooting zone limits rice production more than any other nutritional factor. Yet, little is known about the dynamic response of paddy soil to N-fertiliser application, in terms of horizontal and vertical patchiness in N distribution and transformation. Here, we present a microscale analysis of the profile of ammonium (NH4(+)) and nitrate (NO3(-)), nitrification, oxygen (O2water and O2soil), and pH (pHwater and pHsoil) in paddy soils, collected from two representative rice-production areas in subtropical China. NH4(+) and NO3(-) exhibited dramatic spatiotemporal profiles within N patches on the microscale. We show that pHsoil became constant at 1.0-3.5 mm depth, and O2soil became undetectable at 1.7-4.0 mm. Fertiliser application significantly increased pH, and decreased O2, within N patches. Path analysis showed that the factors governing nitrification scaled in the order: pHwater > pHsoil > NH4(+) > O2water > NO3(-) > O2soil. We discuss the soil properties that decide the degree of nutrient patchiness within them and argue that such knowledge is critical to intelligent appraisals of nutrient-use efficiencies in the field. PMID:27265522

  10. Spatial distribution and temporal variability of arsenic in irrigated rice fields in Bangladesh. 2. Paddy soil.

    PubMed

    Dittmar, Jessica; Voegelin, Andreas; Roberts, Linda C; Hug, Stephan J; Saha, Ganesh C; Ali, M Ashraf; Badruzzaman, A Borhan M; Kretzschmar, Ruben

    2007-09-01

    Arsenic-rich groundwater from shallow tube wells is widely used for the irrigation of boro rice in Bangladesh and West Bengal. In the long term this may lead to the accumulation of As in paddy soils and potentially have adverse effects on rice yield and quality. In the companion article in this issue, we have shown that As input into paddy fields with irrigation water is laterally heterogeneous. To assess the potential for As accumulation in soil, we investigated the lateral and vertical distribution of As in rice field soils near Sreenagar (Munshiganj, Bangladesh) and its changes over a 1 year cycle of irrigation and monsoon flooding. At the study site, 18 paddy fields are irrigated with water from a shallow tube well containing 397 +/- 7 microg L(-1) As. The analysis of soil samples collected before irrigation in December 2004 showed that soil As concentrations in paddy fields did not depend on the length of the irrigation channel between well and field inlet. Within individual fields, however, soil As contents decreased with increasing distance to the water inlet, leading to highly variable topsoil As contents (11-35 mg kg(-1), 0-10 cm). Soil As contents after irrigation (May 2005) showed that most As input occurred close to the water inlet and that most As was retained in the top few centimeters of soil. After monsoon flooding (December 2005), topsoil As contents were again close to levels measured before irrigation. Thus, As input during irrigation was at least partly counteracted by As mobilization during monsoon flooding. However, the persisting lateral As distribution suggests net arsenic accumulation over the past 15 years. More pronounced As accumulation may occur in regions with several rice crops per year, less intense monsoon flooding, or different irrigation schemes. The high lateral and vertical heterogeneity of soil As contents must be taken into account in future studies related to As accumulation in paddy soils and potential As transfer into rice

  11. pH regulates ammonia-oxidizing bacteria and archaea in paddy soils in Southern China.

    PubMed

    Li, Hu; Weng, Bo-Sen; Huang, Fu-Yi; Su, Jian-Qiang; Yang, Xiao-Ru

    2015-07-01

    Ammonia-oxidizing archaea (AOA) and bacteria (AOB) play important roles in nitrogen cycling. However, the effects of environmental factors on the activity, abundance, and diversity of AOA and AOB and the relative contributions of these two groups to nitrification in paddy soils are not well explained. In this study, potential nitrification activity (PNA), abundance, and diversity of amoA genes from 12 paddy soils in Southern China were determined by potential nitrification assay, quantitative PCR, and cloning. The results showed that PNA was highly variable between paddy soils, ranging from 4.05 ± 0.21 to 9.81 ± 1.09 mg NOx-N kg(-1) dry soil day(-1), and no significant correlation with soil parameters was found. The abundance of AOA was predominant over AOB, indicating that AOA may be the major members in aerobic ammonia oxidation in these paddy soils. Community compositions of AOA and AOB were highly variable among samples, but the variations were best explained by pH. AOA sequences were affiliated to the Nitrosopumilus cluster and Nitrososphaera cluster, and AOB were classified into the lineages of Nitrosospira and Nitrosomonas, with Nitrosospira being predominant over Nitrosomonas, accounting for 83.6 % of the AOB community. Moreover, the majority of Nitrosomonas was determined in neutral soils. Canonical correspondence analysis (CCA) analysis further demonstrated that AOA and AOB community structures were significantly affected by pH, soil total organic carbon, total nitrogen, and C/N ratio, suggesting that these factors exert strong effects on the distribution of AOB and AOA in paddy soils in Southern China. In conclusion, our results imply that soil pH was a key explanatory variable for both AOA and AOB community structure and nitrification activity. PMID:25744648

  12. Oryzobacter terrae gen. nov., sp. nov., isolated from paddy soil.

    PubMed

    Kim, Soo-Jin; Lim, Jun-Muk; Hamada, Moriyuki; Ahn, Jae-Hyung; Weon, Hang-Yeon; Suzuki, Ken-ichiro; Ahn, Tae-Young; Kwon, Soon-Wo

    2015-09-01

    A bacterial strain, PSGM2-16(T), was isolated from a pot of paddy soil grown with rice in Suwon region, Republic of Korea, and was characterized as having aerobic, Gram-stain-positive, short-rod-shaped cells with one polar flagellum. The 16S rRNA gene sequence of strain PSGM2-16(T) revealed the highest sequence similarities with Knoellia locipacati DMZ1T (97.4%), Fodinibacter luteus YIM C003(T) (97.2%) and Lapillicoccus jejuensis R-Ac013(T) (97.0%), and the phylogenetic tree showed that strain PSGM2-16(T) formed a subgroup with Ornithinibacter aureus HB09001(T) and F. luteus YIM C003(T) within the family Intrasporangiaceae. The major fatty acids (>10% of the total fatty acids) of strain PSGM2-16(T) were iso-C16 : 0, C17 : 1ω8c and iso-C14 : 0. The predominant menaquinone was MK-8(H4). The polar lipids present were diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylinositol, three aminophospholipids and two phospholipids. The peptidoglycan was type A4γ with meso-diaminopimelic acid as the diagnostic diamino acid. DNA-DNA hybridization values between strain PSGM2-16(T) and closely related taxa were much less than 70%. The genomic DNA G+C content of strain PSGM2-16(T) was 70.0 mol%. On the basis of the evidence presented, it is concluded that strain PSGM2-16(T) represents a novel species of a new genus in the family Intrasporangiaceae, for which the name Oryzobacter terrae gen. nov., sp. nov. is proposed. The type strain of the type species is PSGM2-16(T) ( = KACC 17299(T)= DSM 27137(T)= NBRC 109598(T)). PMID:26297674

  13. Roseomonas oryzae sp. nov., isolated from paddy rhizosphere soil.

    PubMed

    Ramaprasad, E V V; Sasikala, Ch; Ramana, Ch V

    2015-10-01

    A non-motile, coccus-shaped, pale-pink-pigmented bacterium, designated strain JC288T, was isolated from a paddy rhizosphere soil collected from Western Ghats, Kankumbi, Karnataka, India. Cells were found to be Gram-stain-negative, and catalase- and oxidase-positive; the major fatty acids were C16 : 0, C16 : 1ω7c/C16 : 1ω6c, C18 : 1ω7c/C18 : 1ω6c and C18 : 1 2-OH. The predominant respiratory quinone was Q-10 and the genomic DNA G+C content was 67.5 mol%. Strain JC288T contained diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, phosphatidylcholine, four unidentified aminolipids, three unidentified phospholipids, two unidentified lipids, an aminophospholipid and a glycolipid. Hydroxyspirilloxanthin was the major carotenoid of strain JC288T. 16S rRNA gene sequence comparisons indicated that strain JC288T represents a member of the genus Roseomonas within the family Acetobacteraceae of the phylum Proteobacteria. Strain JC288T shared the highest 16S rRNA gene sequence similarity with Roseomonas rhizosphaerae YW11T (97.3 %), Roseomonas aestuarii JC17T (97.1 %), Roseomonas cervicalis CIP 104027T (95.9 %) and other members of the genus Roseomonas ( < 95.5 %). The distinct genomic difference and morphological, physiological and chemotaxonomic differences from the previously described taxa support the classification of strain JC288T as a representative of a novel species of the genus Roseomonas, for which the name Roseomonas oryzae sp. nov. is proposed. The type strain is JC288T ( = KCTC 42542T = LMG 28711T). PMID:26297330

  14. Similarities in chemical composition of soil organic matter across a millennia-old paddy soil chronosequence as revealed by advanced solid-state NMR spectroscopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil organic matter (SOM) accumulation in paddy soils has aroused considerable attention due to its vital significance in global food, energy, climate, and environmental issues. Considerable progress has been made toward the understanding of changes in the quantity of SOM in paddy soils over a mille...

  15. Ameliorants to immobilize Cd in rice paddy soils contaminated by abandoned metal mines in Korea.

    PubMed

    Ok, Yong Sik; Kim, Sung-Chul; Kim, Dong-Kuk; Skousen, Jeffrey G; Lee, Jin-Soo; Cheong, Young-Wook; Kim, Su-Jung; Yang, Jae E

    2011-01-01

    The cadmium (Cd) content of rice grain grown in metal-contaminated paddy soils near abandoned metal mines in South Korea was found to exceed safety guidelines (0.2 mg Cd kg⁻¹) set by the Korea Food and Drug Administration (KFDA). However, current remediation technologies for heavy metal-contaminated soils have limited application with respect to rice paddy soils. Laboratory and greenhouse experiments were conducted to assess the effects of amending contaminated rice paddy soils with zerovalent iron (ZVI), lime, humus, compost, and combinations of these compounds to immobilize Cd and inhibit Cd translocation to rice grain. Sequential extraction analysis revealed that treatment with the ameliorants induced a 50-90% decrease in the bioavailable Cd fractions when compared to the untreated control soil. When compared to the control, Cd uptake by rice was decreased in response to treatment with ZVI + humus (69%), lime (65%), ZVI + compost (61%), compost (46%), ZVI (42%), and humus (14%). In addition, ameliorants did not influence rice yield when compared to that of the control. Overall, the results of this study indicated that remediation technologies using ameliorants effectively reduce Cd bioavailability and uptake in contaminated rice paddy soils. PMID:21052787

  16. Sequestration of organic nitrogen in a paddy soil chronosequence as assessed by amino sugars molecular markers

    NASA Astrophysics Data System (ADS)

    Roth, Philipp; Lehndorff, E.; Cao, Z.; Amelung, W.

    2010-05-01

    Available nitrogen is a limiting factor in paddy rice systems due to ammonia volatilization, denitrification and stabilization in organic complexes. Soil organic nitrogen (SON) might therefore constitute a critical component of the nitrogen cycle in rice systems. The objective of this study was to elucidate the role of microorganisms for the sequestration of paddy N in organic forms. For this purpose we analyzed amino sugars as markers for the residues of bacteria and fungi in a chronosequence of soils that were used for paddy rice production for a period of 0 to 2000 years in the Hangzhou bay area in Southeast China. Within the soil profile, amino sugar concentrations were generally highest in the puddled Ap horizon and decreased with increasing depth along with organic carbon concentrations regardless of the time of rice cultivation. Nevertheless, a sharp increase of total amino sugar concentration from 0.1 g kg-1 to 0.3 g kg-1 was observed in the Ah horizon when comparing tidal wetland to salt marsh that had been impoldered 30 years ago, indicating an increasing importance of microbial residues in SON stabilization following the conversion of the semiaquatic marsh to a terrestrial system. With increased time of paddy rice cropping, amino sugar concentrations continued to increase up to a maximum of 2.1 g kg-1 after 300 years of paddy cultivation but declined again to 1 g kg-1 in soils with 700-2000 years history of cultivation despite increasing organic matter accumulation. Changes in the composition of the amino sugars were also most pronounced at initial stages of paddy rice management. The proportions of glucosamine (abundant in fungal chitin) decreased during the first 50 years of cultivation relative to mainly galactosamine (abundant in bacterial gums) and muramic acid (abundant in bacterial peptidoglycan), that remained at constantly low levels. At later stages of paddy rice cultivation, the ratios of glucosamine to galactosamine and to muramic acid re

  17. Soil Physicochemical and Biological Properties of Paddy-Upland Rotation: A Review

    PubMed Central

    Lv, Teng-Fei; Chen, Yong; Westby, Anthony P.; Ren, Wan-Jun

    2014-01-01

    Paddy-upland rotation is an unavoidable cropping system for Asia to meet the increasing demand for food. The reduction in grain yields has increased the research interest on the soil properties of rice-based cropping systems. Paddy-upland rotation fields are unique from other wetland or upland soils, because they are associated with frequent cycling between wetting and drying under anaerobic and aerobic conditions; such rotations affect the soil C and N cycles, make the chemical speciation and biological effectiveness of soil nutrient elements varied with seasons, increase the diversity of soil organisms, and make the soil physical properties more difficult to analyze. Consequently, maintaining or improving soil quality at a desirable level has become a complicated issue. Therefore, fully understanding the soil characteristics of paddy-upland rotation is necessary for the sustainable development of the system. In this paper, we offer helpful insight into the effect of rice-upland combinations on the soil chemical, physical, and biological properties, which could provide guidance for reasonable cultivation management measures and contribute to the improvement of soil quality and crop yield. PMID:24995366

  18. Selenium inhibits sulfate-mediated methylmercury production in rice paddy soil.

    PubMed

    Wang, Yong-Jie; Dang, Fei; Zhao, Jia-Ting; Zhong, Huan

    2016-06-01

    There is increasing interest in understanding factors controlling methylmercury (MeHg) production in mercury-contaminated rice paddy soil. Sulfate has been reported to affect MeHg biogeochemistry under anoxic conditions, and recent studies revealed that selenium (Se) could evidently reduce MeHg production in paddy soil. However, the controls of sulfate and Se on net MeHg production in paddy soil under fluctuating redox conditions remain largely unknown. Microcosm experiments were conducted to explore the effects of sulfate and Se on net MeHg production in rice paddy soil. Soil was added with 0-960 mg/kg sulfate, in the presence or absence of 3.0 mg/kg selenium (selenite or selenate), and incubated under anoxic (40 days) or suboxic conditions (5 days), simulating fluctuating redox conditions in rice paddy field. Sulfate addition moderately affected soil MeHg concentrations under anoxic conditions, while reoxidation resulted in evidently higher (18-40%) MeHg levels in sulfate amended soils than the control. The observed changes in net MeHg production were related to dynamics of sulfate and iron. However, Se could inhibit sulfate-mediated MeHg production in the soils: Se addition largely reduced net MeHg production in the soils (23-86%, compared to the control), despite of sulfate addition. Similarly, results of the pot experiments (i.e., rice cultivation in amended soils) indicated that soil MeHg levels were rather comparable in Se-amended soils during rice growth period, irrespective of added sulfate doses. The more important role of Se than sulfate in controlling MeHg production was explained by the formation of HgSe nanoparticles irrespective of the presence of sulfate, confirmed by TEM-EDX and XANES analysis. Our findings regarding the effects of sulfate and Se on net MeHg production in rice paddy soil together with the mechanistic explanation of the processes advance our understanding of MeHg dynamics and risk in soil-rice systems. PMID:26901075

  19. Metagenomic profiles of antibiotic resistance genes in paddy soils from South China.

    PubMed

    Xiao, Ke-Qing; Li, Bing; Ma, Liping; Bao, Peng; Zhou, Xue; Zhang, Tong; Zhu, Yong-Guan

    2016-03-01

    Overuse and arbitrary discarding of antibiotics have expanded antibiotic resistance reservoirs, from gut, waste water and activated sludge, to soil, freshwater and even the ocean. Based on the structured Antibiotic Resistance Genes Database and next generation sequencing, metagenomic analysis was used for the first time to detect and quantify antibiotic resistance genes (ARGs) in paddy soils from South China. A total of 16 types of ARGs were identified, corresponding to 110 ARG subtypes. The abundances and distribution pattern of ARGs in paddy soil were distinctively different from those in activated sludge and pristine deep ocean sediment, but close to those of sediment from human-impacted estuaries. Multidrug resistance genes were the most dominant type (38-47.5%) in all samples, and the ARGs detected encompassed the three major resistance mechanisms, among which extrusion by efflux pumps was predominant. Redundancy analysis (RDA) showed that pH was significantly correlated with the distribution of ARG subtypes (P < 0.05). Our results provided a broad spectrum profile of ARGs in paddy soil, indicating that ARGs are widespread in paddy soils of South China. PMID:26850156

  20. Effect of Drying on Heavy Metal Fraction Distribution in Rice Paddy Soil

    PubMed Central

    Qi, Yanbing; Huang, Biao; Darilek, Jeremy Landon

    2014-01-01

    An understanding of how redox conditions affect soil heavy metal fractions in rice paddies is important due to its implications for heavy metal mobility and plant uptake. Rice paddy soil samples routinely undergo oxidation prior to heavy metal analysis. Fraction distribution of Cu, Pb, Ni, and Cd from paddy soil with a wide pH range was investigated. Samples were both dried according to standard protocols and also preserved under anaerobic conditions through the sampling and analysis process and heavy metals were then sequentially extracted for the exchangeable and carbonate bound fraction (acid soluble fraction), iron and manganese oxide bound fraction (reducible fraction), organic bound fraction (oxidizable fraction), and residual fraction. Fractions were affected by redox conditions across all pH ranges. Drying decreased reducible fraction of all heavy metals. Curesidual fraction, Pboxidizable fraction, Cdresidual fraction, and Niresidual fraction increased by 25%, 33%, 35%, and >60%, respectively. Pbresidual fraction, Niacid soluble fraction, and Cdoxidizable fraction decreased 33%, 25%, and 15%, respectively. Drying paddy soil prior to heavy metal analysis overestimated Pb and underestimated Cu, Ni, and Cd. In future studies, samples should be stored after injecting N2 gas to maintain the redox potential of soil prior to heavy metal analysis, and investigate the correlation between heavy metal fraction distribution under field conditions and air-dried samples. PMID:24823670

  1. [Characteristics and Inputs of Cd Contamination in Paddy Soils in Typical Mining and Industrial Areas in Youxian County, Hunan Province].

    PubMed

    Zhang, Min; Wang Mei-e; Chen, Wei-ping; Niu, Jun-jie

    2015-04-01

    In order to explore input pathways and pollution characteristics of Cd contamination in paddy soil in Youxian, Hunan Province, Cd contents in paddy soils, sediments of irrigation canals, typical mineral and industrial products such as coal, gangue and cement were analyzed. It was suggested that the average contents of Cd both in surface paddy soil and the corresponding natural soil were higher than the soil quality standard 0.3 mg x kg(-1). Cd contents in gangue and cement were similar as those in the corresponding natural soils. The atmosphere deposition of Cd was the highest in factory area. The profiles of Cd in 0-100 cm paddy soil and 0-40 cm in natural soils varied significantly from the upper to the lower layer. Cd contents in 0-40 cm layer in paddy soil were much higher than those in corresponding natural soils in mineral and mineral-factory areas. The potentiality for downward movement of Cd in soils in mineral area was the highest among the three studied areas. It suggested Cd contents in surface paddy soil were higher in upwind areas than those in downwind areas in mineral-factory and factory areas. It could be concluded that the main input pathways of Cd in mineral and mineral-factory. areas were from irrigation water, while contribution of atmosphere deposition in mineral-factory and factory areas was also very significant. PMID:26164922

  2. Effects of rice straw ash amendment on Cu solubility and distribution in flooded rice paddy soils.

    PubMed

    Huang, Jang-Hung; Hsu, Shen-Huei; Wang, Shan-Li

    2011-02-28

    Rice straw burning is a common post-harvest practice on rice paddy land, and it leads to the accumulation of rice straw ash (RSA) in paddy soil. To understand the role of RSA in determining the mobility and bioavailability of metal contaminants, this study investigated the effects of RSA amendment on the solubility and distribution of Cu in contaminated rice paddy soils with flooding incubation. The addition of RSA to the soils suppressed the release of Cu into the soil solutions, which was primarily attributed to the metal-binding capacity of the RSA. Additionally, after the soils were flooded, the increase in soil pH and decrease in redox potential resulted in the transformation of Cu into less soluble forms. The RSA amendment appeared to enhance the changes in pH and redox potential of the flooded soils and, consequently, the immobilization of Cu in the soils. The results suggest that the RSA can retard the bioavailability and movement of the metal in contaminated soils and, thus, lower the potential environmental risk of Cu toxicity. PMID:21232857

  3. [Research on characteristics of soil clay mineral evolution in paddy field and dry land by XRD spectrum].

    PubMed

    Zhang, Zhi-dan; Li, Qiao; Luo, Xiang-li; Jiang, Hai-chao; Zheng, Qing-fu; Zhao, Lan-po; Wang, Ji-hong

    2014-08-01

    The present paper took the typical saline-alkali soil in Jilin province as study object, and determinated the soil clay mineral composition characteristics of soil in paddy field and dry land. Then XRD spectrum was used to analyze the evolutionary mechanism of clay mineral in the two kinds of soil. The results showed that the physical and chemical properties of soil in paddy field were better than those in dry land, and paddy field would promote the weathering of mineral particles in saline-alkali soil and enhance the silt content. Paddy field soil showed a strong potassium-removal process, with a higher degree of clay mineral hydration and lower degree of illite crystallinity. Analysis of XRD spectrum showed that the clay mineral composition was similar in two kinds of soil, while the intensity and position of diffraction peak showed difference. The evolution process of clay mineral in dry land was S/I mixture-->vermiculite, while in paddy field it was S/I mixture-->vermiculite-->kaolinite. One kind of hydroxylated 'chlorite' mineral would appear in saline-alkali soil in long-term cultivated paddy field. Taking into account that the physical and chemical properties of soil in paddy field were better then those in dry land, we could know that paddy field could help much improve soil structure, cultivate high-fertility soil and improve saline-alkali soil. This paper used XRD spectrum to determine the characteristics of clay minerals comprehensively, and analyzed two'kinds of land use comparatively, and was a new perspective of soil minerals study. PMID:25474976

  4. [Research on characteristics of soil clay mineral evolution in paddy field and dry land by XRD spectrum].

    PubMed

    Zhang, Zhi-dan; Li, Qiao; Luo, Xiang-li; Jiang, Hai-chao; Zheng, Qing-fu; Zhao, Lan-po; Wang, Ji-hong

    2014-08-01

    The present paper took the typical saline-alkali soil in Jilin province as study object, and determinated the soil clay mineral composition characteristics of soil in paddy field and dry land. Then XRD spectrum was used to analyze the evolutionary mechanism of clay mineral in the two kinds of soil. The results showed that the physical and chemical properties of soil in paddy field were better than those in dry land, and paddy field would promote the weathering of mineral particles in saline-alkali soil and enhance the silt content. Paddy field soil showed a strong potassium-removal process, with a higher degree of clay mineral hydration and lower degree of illite crystallinity. Analysis of XRD spectrum showed that the clay mineral composition was similar in two kinds of soil, while the intensity and position of diffraction peak showed difference. The evolution process of clay mineral in dry land was S/I mixture-->vermiculite, while in paddy field it was S/I mixture-->vermiculite-->kaolinite. One kind of hydroxylated 'chlorite' mineral would appear in saline-alkali soil in long-term cultivated paddy field. Taking into account that the physical and chemical properties of soil in paddy field were better then those in dry land, we could know that paddy field could help much improve soil structure, cultivate high-fertility soil and improve saline-alkali soil. This paper used XRD spectrum to determine the characteristics of clay minerals comprehensively, and analyzed two'kinds of land use comparatively, and was a new perspective of soil minerals study. PMID:25508755

  5. Assessing the pollution risk of soil Chromium based on loading capacity of paddy soil at a regional scale

    NASA Astrophysics Data System (ADS)

    Qu, Mingkai; Li, Weidong; Zhang, Chuanrong; Huang, Biao; Zhao, Yongcun

    2015-12-01

    The accumulation of a trace metal in rice grain is not only affected by the total concentration of the soil trace metal, but also by crop variety and related soil properties, such as soil pH, soil organic matter (SOM) and so on. However, these factors were seldom considered in previous studies on mapping the pollution risk of trace metals in paddy soil at a regional scale. In this study, the spatial nonstationary relationships between rice-Cr and a set of perceived soil properties (soil-Cr, soil pH and SOM) were explored using geographically weighted regression; and the relationships were then used for calculating the critical threshold (CT) of soil-Cr concentration that may ensure the concentration of rice-Cr being below the permissible limit. The concept of “loading capacity” (LC) for Cr in paddy soil was then defined as the difference between the CT and the real concentration of Cr in paddy soil, so as to map the pollution risk of soil-Cr to rice grain and assess the risk areas in Jiaxing city, China. Compared with the information of the concentration of the total soil-Cr, such results are more valuable for spatial decision making in reducing the accumulation of rice-Cr at a regional scale.

  6. Assessing the pollution risk of soil Chromium based on loading capacity of paddy soil at a regional scale

    PubMed Central

    Qu, Mingkai; Li, Weidong; Zhang, Chuanrong; Huang, Biao; Zhao, Yongcun

    2015-01-01

    The accumulation of a trace metal in rice grain is not only affected by the total concentration of the soil trace metal, but also by crop variety and related soil properties, such as soil pH, soil organic matter (SOM) and so on. However, these factors were seldom considered in previous studies on mapping the pollution risk of trace metals in paddy soil at a regional scale. In this study, the spatial nonstationary relationships between rice-Cr and a set of perceived soil properties (soil-Cr, soil pH and SOM) were explored using geographically weighted regression; and the relationships were then used for calculating the critical threshold (CT) of soil-Cr concentration that may ensure the concentration of rice-Cr being below the permissible limit. The concept of “loading capacity” (LC) for Cr in paddy soil was then defined as the difference between the CT and the real concentration of Cr in paddy soil, so as to map the pollution risk of soil-Cr to rice grain and assess the risk areas in Jiaxing city, China. Compared with the information of the concentration of the total soil-Cr, such results are more valuable for spatial decision making in reducing the accumulation of rice-Cr at a regional scale. PMID:26675587

  7. Arsenic contamination of Bangladesh paddy field soils: implications for rice contribution to arsenic consumption.

    PubMed

    Meharg, Andrew A; Rahman, Md Mazibur

    2003-01-15

    Arsenic contaminated groundwater is used extensively in Bangladesh to irrigate the staple food of the region, paddy rice (Oryza sativa L.). To determine if this irrigation has led to a buildup of arsenic levels in paddy fields, and the consequences for arsenic exposure through rice ingestion, a survey of arsenic levels in paddy soils and rice grain was undertaken. Survey of paddy soils throughout Bangladesh showed that arsenic levels were elevated in zones where arsenic in groundwater used for irrigation was high, and where these tube-wells have been in operation for the longest period of time. Regression of soil arsenic levels with tube-well age was significant. Arsenic levels reached 46 microg g(-1) dry weight in the most affected zone, compared to levels below l0 microg g(-1) in areas with low levels of arsenic in the groundwater. Arsenic levels in rice grain from an area of Bangladesh with low levels of arsenic in groundwaters and in paddy soils showed that levels were typical of other regions of the world. Modeling determined, even these typical grain arsenic levels contributed considerably to arsenic ingestion when drinking water contained the elevated quantity of 0.1 mg L(-1). Arsenic levels in rice can be further elevated in rice growing on arsenic contaminated soils, potentially greatly increasing arsenic exposure of the Bangladesh population. Rice grain grown in the regions where arsenic is building up in the soil had high arsenic concentrations, with three rice grain samples having levels above 1.7 microg g(-1). PMID:12564892

  8. Cadmium Speciation and Release Kinetics in a Thai Paddy Soil Subjected to Varying Redox Regimes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Understanding the factors controlling Cd speciation and bioavailability in flooded, drained, and alternate flooded/drained paddy soil will be crucial to developing and implementing best management practices needed for productive agricultural areas. Transformation of Cd species can occur in response...

  9. Aging well: methanotrophic potential and community structure along a paddy soil chronosequence of 2000 years.

    NASA Astrophysics Data System (ADS)

    Ho, Adrian; Frenzel, Peter

    2010-05-01

    Given that rice paddies are anthropogenic methane sources and the inevitable need to increase rice production to sustain human population growth, it is pertinent to identify the effects of long term agriculture on the selection of methanotrophs. Methanotrophs play a crucial role in mitigating methane emission from rice paddies. Therefore, we analyzed the methanotroph community along a chronosequence of paddy soils from China covering recently reclaimed sites to paddies under permanent agriculture since 2000 years (Cheng et al., 2009; doi:10.1016/j.geoderma.2009.03.016). Maximum potential methane oxidation rate (PMOR) increased monotonically with age. Our results also showed that long-term agriculture imposes a selection pressure on different groups of methanotrophs. In contrast to younger soils, type Ib methanotrophs were observed to multiply in correspondence with increasing PMOR in ancient soils, while other groups showed a relatively stable community composition as revealed by pmoA-based fingerprints (T-RFLP) and quantitative PCR. Cloning and sequencing the pmoA (a key gene in methane oxidation), the soils were found to harbour known and putative methanotrophs, ammonium-oxidizing bacteria, and interestingly, sequences affiliated to Crenothrix, a methane oxidizer with an unusual pmoA (Stoecker et al., 2006; doi:10.1073/pnas.0506361103). In summary, long-term agriculture shapes the community and allows for an elevated level of potential methane oxidation.

  10. Models for Estimating the Physical Properties of Paddy Soil Using Visible and Near Infrared Reflectance Spectroscopy

    NASA Astrophysics Data System (ADS)

    Gholizadeh, A.; Amin, M. S. M.; Borůvka, L.; Saberioon, M. M.

    2014-07-01

    A fast and convenient soil analytical technique is needed for soil quality assessment and precision soil management. The main objective of this study was to evaluate the ability of visible (Vis) and near-infrared (NIR) refl ectance spectroscopy to predict paddy soil properties in a typical Malaysian paddy fi eld. To assess the utility of spectroscopy for soil physical characteristics (bulk density, moisture content, clay, silt and sand) prediction, 118 soil samples were used for laboratory analysis and optical measurement in the Vis-NIR region using an analytical spectral device (ASD) FieldSpec spectroradiometer (350-2500 nm). The Savitzky-Golay algorithm and stepwise multiple linear regression (SMLR) were then applied to preprocess, model, and predict the properties on the basis of their spectral refl ectance within the Vis-NIR range. One-third of the samples (40 samples) were withheld for validation purposes. The study revealed that Vis and NIR spectroscopy calibration models for all the measured soil physical characteristics provided a good fi t (R2 > 0.78); hence Vis and NIR (specifi cally NIR refl ectance) can be considered to be a reliable tool to assess soil physical properties of Malaysian paddy fi elds. The results of this study could contribute signifi cantly to developing site-specifi c management.

  11. [Effects of different fertilizer species on carbon and nitrogen leaching in a reddish paddy soil].

    PubMed

    Liu, Xi-Yu; Zou, Jing-Dong; Xu, Li-Li; Zhang, Xin-Yu; Yang, Feng-Ting; Dai, Xiao-Qin; Wang, Zhong-Qiang; Sun, Xiao-Min

    2014-08-01

    Enhanced fertilization could decrease nitrogen utilization rate and increase carbon and nitrogen leaching, leading to water pollution in agricultural ecosystem. A long-term field experiment had been established on a reddish paddy soil of Qianyanzhou Ecological Experimental Station (114 degrees 53'E, 26 degrees 48'N) in Jiangxi Province in 1998. Soil solution samples were collected by clay tube and vacuum pump. Four fertilizer species treatments were selected: control with no fertilizer (CK), straw return (ST), nitrogen, phosphorus and potassium mineral fertilizers (NPK) and pig manure (OM), aiming to evaluate the effects of different species of fertilizer on carbon and nitrogen leaching in a double rice cropping system. The results showed that: (1) ammonium nitrogen (NH4(+) -N) was the major type of N in soil leachate in reddish paddy soil. The application of NPK could significantly increase the ammonium nitrogen concentration (1.2 mg x L(-1) +/- 0.1 mg x L(-1)) compared with the CK, ST and OM treatments, and the application of OM could significantly increase the dissolved organic carbon (DOC) concentration (27.3 mg x L(-1) +/- 1.6 mg x L(-1)) in soil leachate. The carbon and nitrogen leaching were more notable in the vegetative growth stage than the reproductive growth stage of rice (P < 0.05); (2) the long-term application of NPK and OM increased the NH4(+) -N, DOC, soil organic carbon (SOC) and total nitrogen (TN) contents. The NPK was best beneficial to improve TN contents and OM to improve SOC contents. (3) The DOC contents in soil leachate and SOC in paddy soil had a positive correlation (P < 0.01), while NH4(+) -N contents in soil leachate and TN contents in paddy soil had a positive correlation (P < 0.01). PMID:25338383

  12. Lignin decomposition and microbial community in paddy soils: effects of alternating redox conditions

    NASA Astrophysics Data System (ADS)

    Cerli, Chiara; Liu, Qin; Hanke, Alexander; Kaiser, Klaus; Kalbitz, Karsten

    2013-04-01

    Paddy soils are characterised by interchanging cycles of anaerobic and aerobic conditions. Such fluctuations cause continuous changes in soil solution chemistry as well as in the composition and physiological responses of the microbial community. Temporary deficiency in oxygen creates conditions favourable to facultative or obligates anaerobic bacteria, while aerobic communities can thrive in the period of water absence. These alterations can strongly affect soil processes, in particular organic matter (OM) accumulation and mineralization. In submerged soils, lignin generally constitutes a major portion of the total OM because of hampered degradation under anoxic conditions. The alternating redox cycles resulting from paddy soil management might promote both degradation and preservation of lignin, affecting the overall composition and reactivity of total and dissolved OM. We sampled soils subjected to cycles of anoxic (rice growing period) and oxic (harvest and growth of other crops) conditions since 700 and 2000 years. We incubated suspended Ap material, sampled from the two paddy plus two corresponding non-paddy control soils under oxic and anoxic condition, for 3 months, interrupted by a short period of three weeks (from day 21 to day 43) with reversed redox conditions. At each sampling time (day 2, 21, 42, 63, 84), we determined lignin-derived phenols (by CuO oxidation) as well as phospholipids fatty acids contents and composition. We aimed to highlight changes in lignin decomposition as related to the potential rapid changes in microbial community composition. Since the studied paddy soils had a long history of wet rice cultivation, the microbial community should be well adapted to interchanging oxic and anoxic cycles, therefore fully expressing its activity at both conditions. In non-paddy soil changes in redox conditions caused modification of quantity and composition of the microbial community. On the contrary, in well-established paddy soils the microbial

  13. [Study on Paddy Soil Chronosequences Based on Visiblc-Near Infrared Diffuse Reflectance Spectra].

    PubMed

    Wu, Deng-wei; Zhang, Gan-lin

    2015-12-01

    To investigate spectral characteristics of different soil compositions, eight soil profiles from two paddy soil chronosequences developed on red clays and red sandstones respectively were collected in Jiangxi Province. A total of 37 soil samples were taken from each soil horizons of the profiles. The paddy soil chronosequences were chosen mainly because all soil profiles have the same land management and thus parent materials and rice cultivation time would be two major soil formative factors. This makes it possible to study spectral response characteristics of soil organic matter (SOM) and parent material characteristics. We measured diffuse reflectance spectra data of soil samples using the Cary 5000 spectrophotometer at 350-2500 nm spectral range. Spectral response characteristics of SOM and inorganic minerals in paddy soils were analyzed according to different soil horizons, soil forming times and parent materials. Experiment results showed that for soil samples from a single parent material, overall reflectance presented by PC_1 score can be calibrated for soil organic matter (SOM) content with high precision (R(RC)² = 0.91, R(RS)² = 0.79), even though the SOM content was low (not more than 20 g · kg⁻¹). The absorption strength (AS) at 1400, 1900 and 2200 nm was mainly affected by the minerals inherited from parent materials. And the more the sample was near to bottom of a soil profile, the higher the AS value. Samples with the same mineral components had the similar AS ratio among these three wavelength locations. The differences in parent materials can significantly affect spectral curve shape and spectral absorption strength. To make the calibration more interpretative, parent material factors should be considered. PMID:26964213

  14. Rice (Oryza sativa L) plantation affects the stability of biochar in paddy soil

    NASA Astrophysics Data System (ADS)

    Wu, Mengxiong; Feng, Qibo; Sun, Xue; Wang, Hailong; Gielen, Gerty; Wu, Weixiang

    2015-05-01

    Conversion of rice straw into biochar for soil amendment appears to be a promising method to increase long-term carbon sequestration and reduce greenhouse gas (GHG) emissions. The stability of biochar in paddy soil, which is the major determining factor of carbon sequestration effect, depends mainly on soil properties and plant functions. However, the influence of plants on biochar stability in paddy soil remains unclear. In this study, bulk and surface characteristics of the biochars incubated without rice plants were compared with those incubated with rice plants using a suite of analytical techniques. Results showed that although rice plants had no significant influence on the bulk characteristics and decomposition rates of the biochar, the surface oxidation of biochar particles was enhanced by rice plants. Using 13C labeling we observed that rice plants could significantly increase carbon incorporation from biochar into soil microbial biomass. About 0.047% of the carbon in biochar was incorporated into the rice plants during the whole rice growing cycle. These results inferred that root exudates and transportation of biochar particles into rice plants might decrease the stability of biochar in paddy soil. Impact of plants should be considered when predicting carbon sequestration potential of biochar in soil systems.

  15. Rice (Oryza sativa L) plantation affects the stability of biochar in paddy soil.

    PubMed

    Wu, Mengxiong; Feng, Qibo; Sun, Xue; Wang, Hailong; Gielen, Gerty; Wu, Weixiang

    2015-01-01

    Conversion of rice straw into biochar for soil amendment appears to be a promising method to increase long-term carbon sequestration and reduce greenhouse gas (GHG) emissions. The stability of biochar in paddy soil, which is the major determining factor of carbon sequestration effect, depends mainly on soil properties and plant functions. However, the influence of plants on biochar stability in paddy soil remains unclear. In this study, bulk and surface characteristics of the biochars incubated without rice plants were compared with those incubated with rice plants using a suite of analytical techniques. Results showed that although rice plants had no significant influence on the bulk characteristics and decomposition rates of the biochar, the surface oxidation of biochar particles was enhanced by rice plants. Using (13)C labeling we observed that rice plants could significantly increase carbon incorporation from biochar into soil microbial biomass. About 0.047% of the carbon in biochar was incorporated into the rice plants during the whole rice growing cycle. These results inferred that root exudates and transportation of biochar particles into rice plants might decrease the stability of biochar in paddy soil. Impact of plants should be considered when predicting carbon sequestration potential of biochar in soil systems. PMID:25944542

  16. Rice (Oryza sativa L) plantation affects the stability of biochar in paddy soil

    PubMed Central

    Wu, Mengxiong; Feng, Qibo; Sun, Xue; Wang, Hailong; Gielen, Gerty; Wu, Weixiang

    2015-01-01

    Conversion of rice straw into biochar for soil amendment appears to be a promising method to increase long-term carbon sequestration and reduce greenhouse gas (GHG) emissions. The stability of biochar in paddy soil, which is the major determining factor of carbon sequestration effect, depends mainly on soil properties and plant functions. However, the influence of plants on biochar stability in paddy soil remains unclear. In this study, bulk and surface characteristics of the biochars incubated without rice plants were compared with those incubated with rice plants using a suite of analytical techniques. Results showed that although rice plants had no significant influence on the bulk characteristics and decomposition rates of the biochar, the surface oxidation of biochar particles was enhanced by rice plants. Using 13C labeling we observed that rice plants could significantly increase carbon incorporation from biochar into soil microbial biomass. About 0.047% of the carbon in biochar was incorporated into the rice plants during the whole rice growing cycle. These results inferred that root exudates and transportation of biochar particles into rice plants might decrease the stability of biochar in paddy soil. Impact of plants should be considered when predicting carbon sequestration potential of biochar in soil systems. PMID:25944542

  17. Microprofiling of nitrogen patches in paddy soil: Analysis of spatiotemporal nutrient heterogeneity at the microscale

    NASA Astrophysics Data System (ADS)

    Li, Yilin; Kronzucker, Herbert J.; Shi, Weiming

    2016-06-01

    Flooded paddy soil ecosystems in the tropics support the cultivation of the majority of the world’s leading crop, rice, and nitrogen (N) availability in the paddy-soil rooting zone limits rice production more than any other nutritional factor. Yet, little is known about the dynamic response of paddy soil to N-fertiliser application, in terms of horizontal and vertical patchiness in N distribution and transformation. Here, we present a microscale analysis of the profile of ammonium (NH4+) and nitrate (NO3‑), nitrification, oxygen (O2water and O2soil), and pH (pHwater and pHsoil) in paddy soils, collected from two representative rice-production areas in subtropical China. NH4+ and NO3‑ exhibited dramatic spatiotemporal profiles within N patches on the microscale. We show that pHsoil became constant at 1.0–3.5 mm depth, and O2soil became undetectable at 1.7–4.0 mm. Fertiliser application significantly increased pH, and decreased O2, within N patches. Path analysis showed that the factors governing nitrification scaled in the order: pHwater > pHsoil > NH4+ > O2water > NO3‑ > O2soil. We discuss the soil properties that decide the degree of nutrient patchiness within them and argue that such knowledge is critical to intelligent appraisals of nutrient-use efficiencies in the field.

  18. Microprofiling of nitrogen patches in paddy soil: Analysis of spatiotemporal nutrient heterogeneity at the microscale

    PubMed Central

    Li, Yilin; Kronzucker, Herbert J.; Shi, Weiming

    2016-01-01

    Flooded paddy soil ecosystems in the tropics support the cultivation of the majority of the world’s leading crop, rice, and nitrogen (N) availability in the paddy-soil rooting zone limits rice production more than any other nutritional factor. Yet, little is known about the dynamic response of paddy soil to N-fertiliser application, in terms of horizontal and vertical patchiness in N distribution and transformation. Here, we present a microscale analysis of the profile of ammonium (NH4+) and nitrate (NO3−), nitrification, oxygen (O2water and O2soil), and pH (pHwater and pHsoil) in paddy soils, collected from two representative rice-production areas in subtropical China. NH4+ and NO3− exhibited dramatic spatiotemporal profiles within N patches on the microscale. We show that pHsoil became constant at 1.0–3.5 mm depth, and O2soil became undetectable at 1.7–4.0 mm. Fertiliser application significantly increased pH, and decreased O2, within N patches. Path analysis showed that the factors governing nitrification scaled in the order: pHwater > pHsoil > NH4+ > O2water > NO3− > O2soil. We discuss the soil properties that decide the degree of nutrient patchiness within them and argue that such knowledge is critical to intelligent appraisals of nutrient-use efficiencies in the field. PMID:27265522

  19. Carbon Dioxide Flux from Rice Paddy Soils in Central China: Effects of Intermittent Flooding and Draining Cycles

    PubMed Central

    Liu, Yi; Wan, Kai-yuan; Tao, Yong; Li, Zhi-guo; Zhang, Guo-shi; Li, Shuang-lai; Chen, Fang

    2013-01-01

    A field experiment was conducted to (i) examine the diurnal and seasonal soil carbon dioxide (CO2) fluxes pattern in rice paddy fields in central China and (ii) assess the role of floodwater in controlling the emissions of CO2 from soil and floodwater in intermittently draining rice paddy soil. The soil CO2 flux rates ranged from −0.45 to 8.62 µmol.m−2.s−1 during the rice-growing season. The net effluxes of CO2 from the paddy soil were lower when the paddy was flooded than when it was drained. The CO2 emissions for the drained conditions showed distinct diurnal variation with a maximum efflux observed in the afternoon. When the paddy was flooded, daytime soil CO2 fluxes reversed with a peak negative efflux just after midday. In draining/flooding alternating periods, a sudden pulse-like event of rapidly increasing CO2 efflux occured in response to re-flooding after draining. Correlation analysis showed a negative relation between soil CO2 flux and temperature under flooded conditions, but a positive relation was found under drained conditions. The results showed that draining and flooding cycles play a vital role in controlling CO2 emissions from paddy soils. PMID:23437170

  20. Mercury Fractionation in Superficial Sediment and Paddy Soil Samples from Tianjin, Northern China.

    PubMed

    Wu, Chao; Zhang, Zhaoji; Fei, Yuhong; Wu, Guoqing; Qian, Yong

    2016-08-01

    Sediment and soil samples from the Beitang River (BR) and the Haihe River (HR) in Tianjin were analyzed to investigate the extent of mercury contamination. The results show that total mercury (THg) contents in the BR and HR sediments were 2241 ± 1024 and 653 ± 450 ng g(-1), and THg in rice paddy soils were 907 ± 345 and 328 ± 286 ng g(-1), respectively. Industrial and domestic sewage were regarded as the main sources of mercury in the two river basins. Sediment-bound mercury in the BR and the HR were found to be predominantly associated with the organic-bound fraction (55 %) and residual fraction and (54 %), while soil-bound mercury was mainly in organic-bound fraction in paddy soils (61 % and 57 %, respectively). The availability of this element (soluble and exchangeable and specifically sorbed fraction) seemed restricted, but significantly higher in the paddy soils than in sediments. Higher soluble and exchangeable, specifically sorbed fraction and organic-bound fraction may promote the higher toxic methylmercury and bioavailable fraction formation in the soils during the rice cultivation. PMID:27283074

  1. Increase of available phosphorus by fly-ash application in paddy soils

    SciTech Connect

    Lee, C.H.; Lee, H.; Lee, Y.B.; Chang, H.H.; Ali, M.A.; Min, W.; Kim, S.; Kim, P.J.

    2007-07-01

    Fly ash from the coal- burning industry may be a potential inorganic soil amendment to increase rice productivity and to restore the soil nutrient balance in paddy soil. In this study, fly ash was applied at rates of 0, 40, 80, and 120 Mg ha{sup -1} in two paddy soils (silt loam in Yehari and loamy sand in Daegok). During rice cultivation, available phosphorus (P) increased significantly with fly ash application, as there was high content of P (786 mg kg{sup -1}) in the applied fly ash. In addition, high content of silicon (Si) and high pH of fly ash contributed to increased available-P content by ion competition between phosphate and silicate and by neutralization of soil acidity, respectively. With fly-ash application, water-soluble P (W-P) content increased significantly together with increasing aluminum- bound P (Al- P) and calcium- bound P (Ca- P) fractions. By contrast, iron- bound P (Fe- P) decreased significantly because of reduction of iron under the flooded paddy soil during rice cultivation. The present experiment indicated that addition of fly ash had a positive benefit on increasing the P availability.

  2. Do microorganism stoichiometric alterations affect carbon sequestration in paddy soil subjected to phosphorus input?

    PubMed

    Zhang, ZhiJian; Li, HongYi; Hu, Jiao; Li, Xia; He, Qiang; Tian, GuangMing; Wang, Hang; Wang, ShunYao; Wang, Bei

    2015-04-01

    Ecological stoichiometry provides a powerful tool for integrating microbial biomass stoichiometry with ecosystem processes, opening far-reaching possibilities for linking microbial dynamics to soil carbon (C) metabolism in response to agricultural nutrient management. Despite its importance to crop yield, the role of phosphorus (P) with respect to ecological stoichiometry and soil C sequestration in paddy fields remains poorly understood, which limits our ability to predict nutrient-related soil C cycling. Here, we collected soil samples from a paddy field experiment after seven years of superphosphate application along a gradient of 0, 30, 60, and 90 (P-0 through P-90, respectively) kg.ha-1.yr-1 in order to evaluate the role of exogenous P on soil C sequestration through regulating microbial stoichiometry. P fertilization increased soil total organic C and labile organic C by 1-14% and 4-96%, respectively, while rice yield is a function of the activities of soil β-1,4-glucosidase (BG), acid phosphatase (AP), and the level of available soil P through a stepwise linear regression model. P input induced C limitation, as reflected by decreases in the ratios of C:P in soil and microbial biomass. An eco-enzymatic ratio indicating microbial investment in C vs. P acquisition, i.e., ln(BG): ln(AP), changed the ecological function of microbial C acquisition, and was stoichiometrically related to P input. This mechanism drove a shift in soil resource availability by increasing bacterial community richness and diversity, and stimulated soil C sequestration in the paddy field by enhancing C-degradation-related bacteria for the breakdown of plant-derived carbon sources. Therefore, the decline in the C:P stoichiometric ratio of soil microorganism biomass under P input was beneficial for soil C sequestration, which offered a "win-win" relationship for the maximum balance point between C sequestration and P availability for rice production in the face of climate change. PMID

  3. Assessment of soil biological quality index (QBS-ar) in different crop rotation systems in paddy soils

    NASA Astrophysics Data System (ADS)

    Nadimi-Goki, Mandana; Bini, Claudio; haefele, Stephan

    2013-04-01

    New methods, based on soil microarthropods for soil quality evaluation have been proposed by some Authors. Soil microarthropods demonstrated to respond sensitively to land management practices and to be correlated with beneficial soil functions. QBS Index (QBS-ar) is calculated on the basis of microarthropod groups present in a soil sample. Each biological form found in the sample receives a score from 1 to 20 (eco-morphological index, EMI), according to its adaptation to soil environment. The objective of this study was to evaluate the effect of various rotation systems and sampling periods on soil biological quality index, in paddy soils. For the purpose of this study surface soil samples (0-15 cm depth) were collected from different rotation systems (rice-rice-rice, soya-rice-rice, fallow-rice and pea-soya-rice) with three replications, and four sampling times in April (after field preparation), June (after seedling), August (after tillering stage) and October (after rice harvesting). The study area is located in paddy soils of Verona area, Northern Italy. Soil microarthropods from a total of 48 samples were extracted and classified according to the Biological Quality of Soil Index (QBS-ar) method. In addition soil moisture, Cumulative Soil Respiration and pH were measured in each site. More diversity of microarthropod groups was found in June and August sampling times. T-test results between different rotations did not show significant differences while the mean difference between rotation and different sampling times is statistically different. The highest QBS-ar value was found in the fallow-rice rotation in the forth soil sampling time. Similar value was found in soya-rice-rice rotation. Result of linear regression analysis indicated that there is significant correlation between QBS-ar values and Cumulative Soil Respiration. Keywords: soil biological quality index (QBS-ar), Crop Rotation System, paddy soils, Italy

  4. Microbes influence the fractionation of arsenic in paddy soils with different fertilization regimes.

    PubMed

    Li, Feng; Zheng, Yuan-Ming; He, Ji-Zheng

    2009-04-01

    Sequential extraction procedures were used to investigate the influence of the microbes on the distribution of arsenic in a Chinese paddy soil under different long-term fertilization treatments. The paddy soil with four long-term fertilization treatments (CK, M, NPK and NPK+M) and three levels of arsenate addition (0, 50, 100 mg As kg(-1) dry soil), were selected to construct microcosms for laboratory incubation. After the incubation, soil samples were sequentially extracted to determine As in various fractions, i.e. water soluble (F0), exchangeable (F1), bound to carbonates (F2), bound to Fe and Mn oxides (F3), bound to organic matter and sulfides (F4), and residual (F5, mineral matrix). Results showed that most of the As was fixed by mineral matrix (F5, ratios ranging from 46.22% to 96.37%), followed by As bound to Fe and Mn oxides (F3, ratios ranging from 3.14% to 28.18%), and the ratios of the other four fractions (F0, F1, F2 and F4) were mostly less than 10%. The microbes in the paddy soil could make As transform from inactive fraction (F5) to relatively active fractions (F0, F1, F2 and F3) and thus increase its environmental risk. With the increase of the As addition levels and with the application of manure or chemical NPK fertilizers, As was distributed more in the relatively active fractions (F0, F1, F2, F3 and F4) in the paddy soil mediated by the microbes. In addition, Fe and Mn oxides could play an important role in decreasing the As leaching potential from the mineral matrix to soil solution and thus abate the As risk to human health. PMID:19155050

  5. Change of PAHs with evolution of paddy soils from prehistoric to present over the last six millennia in the Yangtze River Delta region, China.

    PubMed

    Zhang, Jin; Cornelia, Mueller-Niggemann; Wang, Minyan; Cao, Zhihong; Luo, Xiping; Wong, Minghung; Chen, Wei

    2013-04-01

    To evaluate the influence of hydroponics management on soil organic components with evolution of paddy soil over the last six millennia, PAHs, as a biomarker, as well as total organic carbon content were used to explore changes of paddy soil organic carbon in two entirely buried ancient paddy soil profiles. The results showed that hydroponics management can cause organic carbon deposition in rice paddy. The changing of total PAH concentrations was not always in accordance with the changing of total organic carbon contents in layers of the buried ancient paddy soils. The PAHs in 6280 BP prehistoric paddy soil layer was 3-ring>5-ring>4-ring>6-ring, while in layers of the present paddy soil and the prehistoric upland were 3-ring>4-ring>5-ring>6-ring. The contribution of phenanthrene to total PAHs in two profiles and the increasing ratio of phenanthrene to alkylated PAHs from parent material/6280 BP prehistoric upland to 6280 BP paddy suggested substantial increase of the anthropogenic influence of hydroponics management on rice paddy soil. And in view of the (14)C age and bioremains in the two profiles, it was only possible for PAHs to be derived from hydroponics management with evolution of the paddy soils form the Neolithic age. Cadalene could be used as an indicator for biological sources of PAHs released by rice plant residues, and benzo[g,h,i]fluoranthene and benzo[g,h,i]perylene for pyrogenic sources released by field vegetation fires. PMID:23435064

  6. Immobilization of Cd in a paddy soil using moisture management and amendment.

    PubMed

    Li, Jianrui; Xu, Yingming

    2015-03-01

    To offer basis for remediation of Cd-polluted paddy soil under reasonable water condition, pot experiment was conducted to study the effects of moisture management and amendment on the immobilization of Cd in paddy soil. Application of sepiolite in combination with phosphate fertilizer reduced exchangeable Cd by 18.2%, 13.7% and 12.5%, brown rice Cd by 52.3%, 46.0% and 46.8%, under continuous flooding, conventional irrigation and wetting irrigation, respectively, compared to the control groups. Under no amendments, the content of Fe(II) in root coating in the continuous flooding treatment was 2.3 and 3.6 times of that in the conventional and wetting irrigation treatments, but Cd content in root coating in the continuous flooding treatment was only 82.6% and 73.8% of that in the conventional and wetting irrigation treatments. Amendments application increased Fe(II) in root coating by 40.1%, 70.2% and 78.0%, but reduced the Cd content in root coating by 35.3%, 42.4% and 38.6% under continuous flooding, conventional irrigation and wetting irrigation, respectively. The lower availability of Cd in soil and the competition for adsorption sites in root coating of rice plant between Cd(2+) and Fe(2+) etc. reduced form bivalent ions in paddy soil resulted in lower Cd concentrations in brown rice in amended soil treatments. PMID:25497757

  7. Abundance, composition and activity of denitrifier communities in metal polluted paddy soils

    PubMed Central

    Liu, Yuan; Liu, Yongzhuo; Zhou, Huimin; Li, Lianqing; Zheng, Jinwei; Zhang, Xuhui; Zheng, Jufeng; Pan, Genxing

    2016-01-01

    Denitrification is one of the most important soil microbial processes leading to the production of nitrous oxide (N2O). The potential changes with metal pollution in soil microbial community for N2O production and reduction are not well addressed. In this study, topsoil samples were collected both from polluted and non-polluted rice paddy fields and denitrifier communities were characterized with molecular fingerprinting procedures. All the retrieved nirK sequences could be grouped into neither α- nor β- proteobacteria, while most of the nosZ sequences were affiliated with α-proteobacteria. The abundances of the nirK and nosZ genes were reduced significantly in the two polluted soils. Thus, metal pollution markedly affected composition of both nirK and nosZ denitrifiers. While the total denitrifying activity and N2O production rate were both reduced under heavy metal pollution of the two sites, the N2O reduction rate showed no significant change. These findings suggest that N2O production activity could be sensitive to heavy metal pollution, which could potentially lead to a decrease in N2O emission in polluted paddies. Therefore, metal pollution could have potential impacts on soil N transformation and thus on N2O emission from paddy soils. PMID:26739424

  8. Abundance, composition and activity of denitrifier communities in metal polluted paddy soils

    NASA Astrophysics Data System (ADS)

    Liu, Yuan; Liu, Yongzhuo; Zhou, Huimin; Li, Lianqing; Zheng, Jinwei; Zhang, Xuhui; Zheng, Jufeng; Pan, Genxing

    2016-01-01

    Denitrification is one of the most important soil microbial processes leading to the production of nitrous oxide (N2O). The potential changes with metal pollution in soil microbial community for N2O production and reduction are not well addressed. In this study, topsoil samples were collected both from polluted and non-polluted rice paddy fields and denitrifier communities were characterized with molecular fingerprinting procedures. All the retrieved nirK sequences could be grouped into neither α- nor β- proteobacteria, while most of the nosZ sequences were affiliated with α-proteobacteria. The abundances of the nirK and nosZ genes were reduced significantly in the two polluted soils. Thus, metal pollution markedly affected composition of both nirK and nosZ denitrifiers. While the total denitrifying activity and N2O production rate were both reduced under heavy metal pollution of the two sites, the N2O reduction rate showed no significant change. These findings suggest that N2O production activity could be sensitive to heavy metal pollution, which could potentially lead to a decrease in N2O emission in polluted paddies. Therefore, metal pollution could have potential impacts on soil N transformation and thus on N2O emission from paddy soils.

  9. [Variation characteristics of soil carbon sequestration under long-term different fertilization in red paddy soil].

    PubMed

    Huang, Jing; Zhang, Yang-zhu; Gao, Ju-sheng; Zhang, Wen-ju; Liu, Shu-jun

    2015-11-01

    The objective of this study was to clarify the changes of soil organic carbon (SOC) content, the saturation capacity of soil carbon sequestration and its cooperation with carbon input (crop source and organic fertilizer source carbon) under long-term (1982-2012) different fertilization in red paddy soil. The results showed that fertilization could increase SOC content. The SOC content of all the fertilization treatments demonstrated a trend of stabilization after applying fertilizer for 30 years. The SOC content in the treatments applying organic manure with mineral fertilizers was between 21.02 and 21.24 g · kg(-1), and the increase rate ranged from 0.41 to 0.59 g · kg(-1) · a(-1). The SOC content in the treatments applying mineral fertilizers only was 15.48 g · kg(-1). The average soil carbon sequestration in the treatments that applied organic manure with mineral fertilizers ranged from 43.61 to 48.43 t C · hm(-2), and the average SOC storage over the years in these treatments was significantly greater than those applying mineral fertilizers only. There was an exponentially positive correlation between C sequestration efficiency and annual average organic C input. It must input exogenous organic carbon at least at 0. 12 t C · hm(-2) · a(-1) to maintain the balance of soil organic carbon under the experimental conditions. PMID:26915193

  10. The variations of Oxidation-Reduction Potential in paddy soil and effects on the methane emission from a periodically irrigated paddy field.

    NASA Astrophysics Data System (ADS)

    Yagi, K.; Iwata, T.; Wakikuromaru, N.

    2014-12-01

    Paddy fields are one of the most important eco-system in monsoon Asia and one of the largest source of CH4 emission. CH4 has significant contribution to the global warming next to CO2 and its greenhouse effect is about 21 times as large as same amount of CO2. CH4 is generated by decomposition of organic matter in soil under anaerobic condition. Oxidation-Reduction Potential (ORP) is the most suitable index representing soil aerobic condition. Or, CH4 is more generated under lower ORP conditions. In this study, ORP in paddy soil was measured during rice cultivated season at a periodically irrigated paddy field, and some effects on the methane flux from the paddy soil was investigated. 3-days flood and 4-days drained condition were regularly repeated at the site from late-June to early October. ORP under flooded condition was measured during irrigated term in 2013 at two mode; regular interval measurement every 2 weeks and intensive measurements during two flooded periods. Methane flux was also measured by the aerodynamic gradient technique. ORP showed rapid decrease when irrigation water was introduced in the paddy field, and lower ORP was shown under the longer flooded condition. From the seasonal-term point of view, lower ORP was shown in later rice season. ORP was suitably modeled as a function of irrigation time. During an irrigation period for four days, higher methane emissions were shown under lower OPR conditions as shown in Fig.1. From the seasonal-term point of view, however, no significant relationship between ORP and methane fluxes. Rapid rise of CH4 flux in early August and gradual decrease between late August and September were shown. It is suggested that seasonal change of methane flux is affected by seasonal changes of soil temperature or the growth level of rice plants.

  11. Potential Contribution of Anammox to Nitrogen Loss from Paddy Soils in Southern China

    PubMed Central

    Yang, Xiao-Ru; Li, Hu; Nie, San-An; Su, Jian-Qiang; Weng, Bo-Sen; Zhu, Gui-Bing; Yao, Huai-Ying; Gilbert, Jack A.

    2014-01-01

    The anaerobic oxidation of ammonium (anammox) process has been observed in diverse terrestrial ecosystems, while the contribution of anammox to N2 production in paddy soils is not well documented. In this study, the anammox activity and the abundance and diversity of anammox bacteria were investigated to assess the anammox potential of 12 typical paddy soils collected in southern China. Anammox bacteria related to “Candidatus Brocadia” and “Candidatus Kuenenia” and two novel unidentified clusters were detected, with “Candidatus Brocadia” comprising 50% of the anammox population. The prevalence of the anammox was confirmed by the quantitative PCR results based on hydrazine synthase (hzsB) genes, which showed that the abundance ranged from 1.16 × 104 to 9.65 × 104 copies per gram of dry weight. The anammox rates measured by the isotope-pairing technique ranged from 0.27 to 5.25 nmol N per gram of soil per hour in these paddy soils, which contributed 0.6 to 15% to soil N2 production. It is estimated that a total loss of 2.50 × 106 Mg N per year is linked to anammox in the paddy fields in southern China, which implied that ca. 10% of the applied ammonia fertilizers is lost via the anammox process. Anammox activity was significantly correlated with the abundance of hzsB genes, soil nitrate concentration, and C/N ratio. Additionally, ammonia concentration and pH were found to be significantly correlated with the anammox bacterial structure. PMID:25416768

  12. Baseline soil variation is a major factor in arsenic accumulation in Bengal Delta paddy rice.

    PubMed

    Lu, Ying; Adomako, Eureka E; Solaiman, A R M; Islam, M Rafiqul; Deacon, Claire; Williams, P N; Rahman, G K M M; Meharg, Andrew A

    2009-03-15

    Factors responsible for paddy soil arsenic accumulation in the tubewell irrigated systems of the Bengal Delta were investigated. Baseline (i.e., nonirrigated) and paddy soils were collected from 30 field systems across Bangladesh. For each field, soil sampled at dry season (Boro) harvest i.e., the crop cycle irrigated with tubewell water, was collected along a 90 m transect away from the tubewell irrigation source. Baseline soil arsenic levels ranged from 0.8 to 21. mg/kg, with lower values found on the Pliestocene Terrace around Gazipur (average, 1.6 +/- 0.2 mg/kg), and higher levels found in Holecene sediment tracts of Jessore and Faridpur (average, 6.6 +/- 1.0 mg/kg). Two independent approaches were used to assess the extent of arsenic build-up in irrigated paddy soils. First, arsenic build-up in paddy soil at the end of dry season production (irrigated - baseline soil arsenic) was regressed against number of years irrigated and tubewell arsenic concentration. Years of irrigation was not significant (P = 0.711), indicating no year-on-year arsenic build-up, whereas tubewell As concentration was significant (P = 0.008). The second approach was analysis of irrigated soils for 20 fields over 2 successive years. For nine of the fields there was a significant (P < 0.05) decrease in soil arsenic from year 1 to 2, one field had a significant increase, whereas there was no change for the remaining 10. Over the dry season irrigation cycle, soil arsenic built-up in soils at a rate dependent on irrigation tubewell water, 35* (tubewell water concentration in mg/kg, triple bond mg/L). Grain arsenic rises steeply at low soil/shoot arsenic levels, plateauing out at concentratations. Baseline soil arsenic at Faridpur sites corresponded to grain arsenic levels at the start of this saturation phase. Therefore, variation in baseline levels of soil arsenic leads to a large range in grain arsenic. Where sites have high baseline soil arsenic, further additional arsenic from irrigation

  13. Coal fly ash and phospho-gypsum mixture as an amendment to improve rice paddy soil fertility

    SciTech Connect

    Lee, Y.B.; Ha, H.S.; Lee, C.H.; Kim, P.J.

    2008-04-15

    Rice is a plant that requires high levels of silica (Si). As a silicate NOD source to rice, coal fly ash (hereafter, fly ash), which has an alkaline pH and high available silicate and boron (B) contents, was mixed with phosphor-gypsum (hereafter, gypsum, 50%, wt wt{sup -1}), a by-product from the production of phosphate fertilizer, to improve the fly ash limitation. Field experiments were carried out to evaluate the effect of the mixture on soil properties and rice (Oryza sativa) productivity in silt loam (SiL) and loamy sand (LS) soils to which 0 (FG 0), 20 (FG 20), 40 (FG 40), and 60 (FG 60) Mg ha{sup -1} were added. The mixture increased the amount of available silicate and exchangeable calcium (Ca) contents in the soils and the uptake of silicate by rice plant. The mixture did not result in accumulation of heavy metals in soil and an excessive uptake of heavy metals by the rice grain. The available boron content in soil increased with the mixture application levels up to 1.42 mg kg{sup -1} following the application of 60 Mg ha{sup -1} but did not show toxicity. The mixture increased significantly rice yield and showed the highest yields following the addition of 30-40 Mg ha{sup -1} in two soils. It is concluded that the fly ash and gypsum mixture could be a good source of inorganic soil amendments to restore the soil nutrient balance in rice paddy soil.

  14. [Seasonal dynamics of soil active carbon pool in a purple paddy soil in southwest China].

    PubMed

    Wu, Yan; Jiang, Chang-sheng; Hao, Qing-ju

    2012-08-01

    The seasonal dynamics of soil organic carbon (SOC), readily oxidized carbon (ROC), dissolved organic carbon (DOC) and microbial biomass carbon (MBC) in a purple paddy soil were studied in a long-term field experimental station in Chongqing, China. The results showed that the seasonal variations of the contents of SOC, ROC and MBC had similar trends in the rape growing season. The contents were much higher in the early and late stages than in the middle stage of the rape growth. SOC, ROC and MBC all achieved the highest values of 16.20 g x kg(-1), 3.58 g x kg(-1) and 309.70 mg x kg(-1) at the end of the growing period, respectively. The seasonal change of DOC content presented as a single peak and reached to the highest value of 37.64 mg x kg(-1) at the middle stage of the rape growth. The temporal dynamics of the allocation ratios of ROC, MBC and DOC were similar to that of their contents. The allocation ratios of ROC, MBC and DOC were 15.49%-23.93%, 1.44%-2.06% and 0.11%-0.32% during the rape growing season, respectively. The influencing factors of SOC and ROC contents were the soil temperature at 5 cm soil depth, soil total nitrogen content and pH. MBC content was jointly impacted by the soil temperature at 5 cm soil depth, root biomass and its C and N contents. DOC content was mainly affected by soil moisture. PMID:23213908

  15. Mercury methylation in paddy soil: source and distribution of mercury species at a Hg mining area, Guizhou Province, China

    NASA Astrophysics Data System (ADS)

    Zhao, Lei; Anderson, Christopher W. N.; Qiu, Guangle; Meng, Bo; Wang, Dingyong; Feng, Xinbin

    2016-04-01

    Rice paddy plantation is the dominant agricultural land use throughout Asia. Rice paddy fields have been identified as important sites for methylmercury (MeHg) production in the terrestrial ecosystem and a primary pathway of MeHg exposure to humans in mercury (Hg) mining areas. We compared the source and distribution of Hg species in different compartments of the rice paddy during a complete rice-growing season at two different typical Hg-contaminated mining sites in Guizhou province, China: an abandoned site with a high Hg concentration in soil but a low concentration in the atmosphere and a current-day artisanal site with a low concentration in soil but a high concentration in the atmosphere. Our results showed that the flux of new Hg to the ecosystem from irrigation and atmospheric deposition was insignificant relative to the pool of old Hg in soil; the dominant source of MeHg to paddy soil is in situ methylation of inorganic Hg (IHg). Elevated MeHg concentrations and the high proportion of Hg as MeHg in paddy water and the surface soil layer at the artisanal site demonstrated active Hg methylation at this site only. We propose that the in situ production of MeHg in paddy water and surface soil is dependent on elevated Hg in the atmosphere and the consequential deposition of new Hg into a low-pH anoxic geochemical system. The absence of depth-dependent variability in the MeHg concentration in soil cores collected from the abandoned Hg mining site, consistent with the low concentration of Hg in the atmosphere and high pH of the paddy water and irrigation water, suggested that net production of MeHg at this site was limited. We propose that the concentration of Hg in ambient air is an indicator for the risk of MeHg accumulation in paddy rice.

  16. Transformation of marine sediment to paddy soil: Primary marine, lacustrine, and land plant lipids

    NASA Astrophysics Data System (ADS)

    Mueller-Niggemann, Cornelia; Cao, Zhihong; Schwark, Lorenz

    2010-05-01

    More than fifty percent of the world's population feeds on rice. The continuous population increase and urban sprawl leads to an ever-increasing demand for new rice cultivation area, in particular China. For centuries suitable coastal areas in China have been exploited for land reclamation, i.e. conversion of coastal marine and lacustrine marshlands into rice paddy fields. Flooded rice paddies are considered one of the major biogenic sources of methane into the atmospheric. Methane is thought to be about 30 times more efficient as greenhouse gas, when compared to carbon dioxide. Overall, rice fields are assumed to contribute app. 10-25% to global CH4 production. It is thus paramount importance to study the effects of increasing rice cultivation and land reclamation in China. For global carbon cycle investigation, it is crucial whether paddy soils, due to their large extent and higher carbon turnover, serve as carbon (CO2) sinks or sources. Here we present results from a chronosequence study of paddy soils with different and well known starting dates of cultivation, in the Zhejiang province (Yangtze River delta) by land reclamation through the building of protective dikes over the past 2000 years. Two end members of natural sediments subjected to land reclamation, a marine tidal mudflat in the Yangtze delta and a coastal lake, represent the substrate on which the paddy soil evolution started. Dike systems were constructed 2000, 1000, 700, 300, 100, and 50 years before present. We are thus able to follow the evolution of rice paddy soils developed on marine sediments using eight well defined tie-points. This chronosequence is then used for assessing the relative proportion of primary marine or lacustrine organic matter preserved in present day soils and to identify the amount and composition of organic matter added since cultivation started. Paddy soil management introduces rice plants debris and exudates as well as rice-associated microbial biomass (covered in a

  17. Immobilization of Cd in paddy soil using moisture management and amendment.

    PubMed

    Li, Jianrui; Xu, Yingming

    2015-04-01

    To offer scientific data support for remediation of Cd-contaminated paddy soils under reasonable water condition, pot experiment was conducted to study the effects of moisture management and amendments on Cd immobilization in a paddy soil. Application of biochar combined with organic fertilizer reduced the exchangeable Cd by 20.4, 15.7, and 13.0% and brown rice Cd by 43.8, 35.5, and 42.1% under continuous flooding, conventional irrigation, and wetting irrigation, respectively, compared to the controls. Under no amendments, the content of Fe(II) in root coating in the continuous flooding treatment was 2.3 and 3.6 times of that in the conventional and wetting irrigation treatments, but Cd in root coating in the continuous flooding treatment was only 82.6 and 73.8% of that in the conventional and wetting irrigation treatments. Applying amendments increased the Fe(II) in root coating by 27.3, 59.1, and 65.0% but reduced the Cd in root coating by 33.6, 26.5, and 25.1% under continuous flooding, conventional irrigation, and wetting irrigation, respectively. The lower bioavailability of Cd in paddy soil and the competition for adsorption sites in root coating of rice plant between Cd(2+) and Fe(2+) reduced from bivalent ions jointly caused the lower brown rice Cd in amended soils. PMID:25388557

  18. Effect of ferrihydrite biomineralization on methanogenesis in an anaerobic incubation from paddy soil

    NASA Astrophysics Data System (ADS)

    Zhuang, Li; Xu, Jielong; Tang, Jia; Zhou, Shungui

    2015-05-01

    Microbial reduction of Fe(III) can be one of the major factors controlling methane production from anaerobic sedimentary environments, such as paddy soils and wetlands. Although secondary iron mineralization following Fe(III) reduction is a process that occurs naturally over time, it has not yet been considered in methanogenic systems. This study performed a long-term anaerobic incubation of a paddy soil and ferrihydrite-supplemented soil cultures to investigate methanogenesis during ferrihydrite biomineralization. The results revealed that the long-term effect of ferrihydrite on methanogenesis may be enhancement rather than suppression documented in previous studies. During initial microbial ferrihydrite reduction, methanogenesis was suppressed; however, the secondary minerals of magnetite formation was simultaneous with facilitated methanogenesis in terms of average methane production rate and acetate utilization rate. In the phase of magnetite formation, microbial community analysis revealed a strong stimulation of the bacterial Geobacter, Bacillus, and Sedimentibacter and the archaeal Methanosarcina in the ferrihydrite-supplemented cultures. Direct electric syntrophy between Geobacter and Methanosarcina via conductive magnetite is the plausible mechanism for methanogenesis acceleration along with magnetite formation. Our data suggested that a change in iron mineralogy might affect the conversion of anaerobic organic matter to methane and might provide a fresh perspective on the mitigation of methane emissions from paddy soils by ferric iron fertilization.

  19. Assessing the labile arsenic pool in contaminated paddy soils by isotopic dilution techniques and simple extractions.

    PubMed

    Stroud, Jacqueline L; Khan, M Asaduzzman; Norton, Gareth J; Islam, M Rafiqul; Dasgupta, Tapash; Zhu, Yong-Guan; Price, Adam H; Meharg, Andrew A; McGrath, Steve P; Zhao, Fang-Jie

    2011-05-15

    Arsenic (As) contamination of paddy soils threatens rice cultivation and the health of populations relying on rice as a staple crop. In the present study, isotopic dilution techniques were used to determine the chemically labile (E value) and phytoavailable (L value) pools of As in a range of paddy soils from Bangladesh, India, and China and two arable soils from the UK varying in the degree and sources of As contamination. The E value accounted for 6.2-21.4% of the total As, suggesting that a large proportion of soil As is chemically nonlabile. L values measured with rice grown under anaerobic conditions were generally larger than those under aerobic conditions, indicating increased potentially phytoavailable pool of As in flooded soils. In an incubation study, As was mobilized into soil pore water mainly as arsenite under flooded conditions, with Bangladeshi soils contaminated by irrigation of groundwater showing a greater potential of As mobilization than other soils. Arsenic mobilization was best predicted by phosphate-extractable As in the soils. PMID:21504212

  20. [Response of nitrification/denitrification and their associated microbes to soil moisture change in paddy soil].

    PubMed

    Liu, Ruo-Xuan; He, Ji-Zheng; Zhang, Li-Mei

    2014-11-01

    To investigate the effect of moisture change on nitrification and denitrification and their corresponding functional microbes, an acidic paddy soil from Taoyuan, Hunan Province was selected as the study object, and soil microcosm experiment containing 4 different water holding capacity (WHC) levels (30% WHC, 60% WHC, 90% WHC, and waterlog) was set up in this study. Results showed that no active nitrification and denitrification occurred in 30% WHC treatment as there were no obvious ammonia consumption and nitrate accumulation, while nitrification was active in 60% WHC and 90% WHC treatments as indicated by the obvious accumulation of nitrate in those two treatments. Meanwhile, significant ammonia consumption and N2O emission were only observed in 90% WHC treatment, implying that a much stronger nitrification in 90% WHC treatment than in 60% WHC treatment and the co-occurrence of nitrification and denitrification in 90% WHC treatment. In waterlog treatment, relatively lower N2O emission was detected and no obvious nitrification was detected, corresponding to a significant lower soil Eh in this treatment than in the other three non-waterlog treatments. Except the early stage of incubation (7 d), the abundance of nirS, nirK and ammonia-oxidizing bacteria (AOB) amoA genes showed similar responses to soil moisture change over time. Except the slight decrease in waterlog treatment, the abundances of the three genes increased significantly as the soil moisture increased, and the highest abundances of nirS, nirK, and amoA gene were observed in 90% WHC treatment in which the highest nitrification and denitrification activity was detected. T-RFLP analysis showed that the community composition of nirS gene-containing denitrifiers changed significantly in response to soil moisture change after two weeks, and soil Eh and C(w) were the main factors affecting the community composition of denitrifiers. PMID:25639106

  1. Stability of soil organic matter accumulated under long-term use as a rice paddy

    NASA Astrophysics Data System (ADS)

    Nakahara, Shiko; Zou, Ping; Ando, Ho; Fu, Jianrong; Cao, Zhihong; Nakamura, Toshio; Sugiura, Yuki; Watanabe, Akira

    2016-01-01

    To understand the mechanism responsible for the enhanced accumulation of soil organic matter (SOM) under long-term use as a rice paddy, soil samples from the plow layer from 16 fields that have been used for irrigated rice production from 5 to 2000 years in the Hangzhou Bay, China, were analyzed. The humin in silt/clay particles was isolated as a representative relatively stable SOM pool, and isotopic signatures (δ13C, δ15N, and 14C concentration), 13C nuclear magnetic resonance (NMR) spectra, and biodegradability in an incubation were examined. The amounts of C and N in the bulk soil, silt/clay, and silt/clay-humin increased with increasing period of use as a rice paddy within the east and west zones, respectively. The degree of humification determined for humic acids indicated that the progression of humification did not contribute to the accumulation of C beyond 100 years. The δ15N of silt/clay-humin suggested an increase in organic N derived from chemical fertilizer or recent biological fixation with increasing amount of this fraction. The 14C concentration showed a negative correlation with the amount of silt/clay-humin C. The structural property with regard to 13C NMR spectra and biodegradability of the silt/clay-humin remained constant with the length of use as a rice paddy or 14C concentration. These results suggest that the larger C or N accumulation in the soils with a longer rice paddy history can be attributed to an enhancement in the accumulation of recently generated SOM rather than the stable accumulation of humus over the years.

  2. Identification and isolation of active N2O reducers in rice paddy soil

    PubMed Central

    Ishii, Satoshi; Ohno, Hiroki; Tsuboi, Masahiro; Otsuka, Shigeto; Senoo, Keishi

    2011-01-01

    Dissolved N2O is occasionally detected in surface and ground water in rice paddy fields, whereas little or no N2O is emitted to the atmosphere above these fields. This indicates the occurrence of N2O reduction in rice paddy fields; however, identity of the N2O reducers is largely unknown. In this study, we employed both culture-dependent and culture-independent approaches to identify N2O reducers in rice paddy soil. In a soil microcosm, N2O and succinate were added as the electron acceptor and donor, respectively, for N2O reduction. For the stable isotope probing (SIP) experiment, 13C-labeled succinate was used to identify succinate-assimilating microbes under N2O-reducing conditions. DNA was extracted 24 h after incubation, and heavy and light DNA fractions were separated by density gradient ultracentrifugation. Denaturing gradient gel electrophoresis and clone library analysis targeting the 16S rRNA and the N2O reductase gene were performed. For culture-dependent analysis, the microbes that elongated under N2O-reducing conditions in the presence of cell-division inhibitors were individually captured by a micromanipulator and transferred to a low-nutrient medium. The N2O-reducing ability of these strains was examined by gas chromatography/mass spectrometry. Results of the SIP analysis suggested that Burkholderiales and Rhodospirillales bacteria dominated the population under N2O-reducing conditions, in contrast to the control sample (soil incubated with only 13C-succinate). Results of the single-cell isolation technique also indicated that the majority of the N2O-reducing strains belonged to the genera Herbaspirillum (Burkholderiales) and Azospirillum (Rhodospirillales). In addition, Herbaspirillum strains reduced N2O faster than Azospirillum strains. These results suggest that Herbaspirillum spp. may have an important role in N2O reduction in rice paddy soils. PMID:21677691

  3. Identification and isolation of active N2O reducers in rice paddy soil.

    PubMed

    Ishii, Satoshi; Ohno, Hiroki; Tsuboi, Masahiro; Otsuka, Shigeto; Senoo, Keishi

    2011-12-01

    Dissolved N(2)O is occasionally detected in surface and ground water in rice paddy fields, whereas little or no N(2)O is emitted to the atmosphere above these fields. This indicates the occurrence of N(2)O reduction in rice paddy fields; however, identity of the N(2)O reducers is largely unknown. In this study, we employed both culture-dependent and culture-independent approaches to identify N(2)O reducers in rice paddy soil. In a soil microcosm, N(2)O and succinate were added as the electron acceptor and donor, respectively, for N(2)O reduction. For the stable isotope probing (SIP) experiment, (13)C-labeled succinate was used to identify succinate-assimilating microbes under N(2)O-reducing conditions. DNA was extracted 24  h after incubation, and heavy and light DNA fractions were separated by density gradient ultracentrifugation. Denaturing gradient gel electrophoresis and clone library analysis targeting the 16S rRNA and the N(2)O reductase gene were performed. For culture-dependent analysis, the microbes that elongated under N(2)O-reducing conditions in the presence of cell-division inhibitors were individually captured by a micromanipulator and transferred to a low-nutrient medium. The N(2)O-reducing ability of these strains was examined by gas chromatography/mass spectrometry. Results of the SIP analysis suggested that Burkholderiales and Rhodospirillales bacteria dominated the population under N(2)O-reducing conditions, in contrast to the control sample (soil incubated with only (13)C-succinate). Results of the single-cell isolation technique also indicated that the majority of the N(2)O-reducing strains belonged to the genera Herbaspirillum (Burkholderiales) and Azospirillum (Rhodospirillales). In addition, Herbaspirillum strains reduced N(2)O faster than Azospirillum strains. These results suggest that Herbaspirillum spp. may have an important role in N(2)O reduction in rice paddy soils. PMID:21677691

  4. Comparisons of direct extraction methods of microbial DNA from different paddy soils.

    PubMed

    Islam, Md Rashedul; Sultana, Tahera; Melvin Joe, M; Cho, Jang-Cheon; Sa, Tongmin

    2012-07-01

    Molecular analyses for the study of soil microbial communities often depend on the direct extraction of DNA from soils. The present work compares the effectiveness of three different methods of extracting microbial DNA from seven different paddy soils. Comparison among different DNA extraction methods against different paddy soil samples revealed a marked variation in DNA yields from 3.18-20.17 μg DNA/g of dry soil. However, irrespective of the soil samples and extraction methods the DNA fragment size was >10 kb. Among the methods evaluated, method-C (chemical-enzymatic-mechanical) had better cell lysis efficiency and DNA yield. After purification of crude DNA by Purification Kit, A260/A230 and A260/A280 ratios of the DNA obtained by method-C reached up to 2.27 and 1.89, respectively, sustaining the efficacy of this technique in removing humic acid, protein and other contaminants. Results of the comprehensive evaluation of DNA extraction methods suggest that method-C is superior to other two methods (chemical-enzymatic and chemical-mechanical), and was the best choice for extraction of total DNA from soil samples. Since soil type and microbial community characteristics influence DNA recovery, this study provides guidance for choosing appropriate extraction and purification methods according to experimental goals. PMID:23961194

  5. Flooding impact on the distribution of microbial tetraether lipids in paddy rice soil in China

    NASA Astrophysics Data System (ADS)

    Ayari, Asma; Yang, Huan; Xie, Shucheng

    2013-09-01

    Isoprenoid and branched glycerol dialkyl glycerol tetraethers (GDGTs) lipids were studied in flooded and non-flooded paddy soil in Wuhan, central China, to examine the response of the GDGTs distribution to the soil flooding. Samples were collected before and after the soil flooding in four specific months. Both core (CL) and intact polar (IPL) GDGTs were quantified. Increase in the abundance of archaeol and caldarchaeol may be indicative of the occurrence of methanogens in the flooded soil. A negative correlation was observed between the ratio of IPL branched GDGT-IIa to GDGT-Ia and the soil pH. The rise of the soil pH in the acid soil is known to be controlled by the redox conditions resulting from flooding. Thus, the branched GDGTs distribution may be controlled by the water content in the paddy soil. In addition, we suggest that the anoxic conditions resulting from flooding may also control the abundance of branched GDGTs relative to crenarchaeol, which in turn results in the increase of branched and isoprenoidal tetraethers (BIT) values, the index for the terrestrial input to the marine sediments.

  6. Variations in soil microbial community structure induced by the conversion from paddy fields to upland fields

    NASA Astrophysics Data System (ADS)

    Dai, X.

    2015-12-01

    Land-use conversion is an important factor influencing the carbon and nitrogen gas exchange between land and atmosphere, and soil microorganisms is main driver of soil carbon and nitrogen gas production. Understanding the effect of land-use conversion on soil microbial communities and its influencing factor is important for greenhouse gas emission reduction and soil organic carbon and nitrogen sequestration and stability. The influence of land use conversion on soil process was undergoing a dynamic change, but little research has been done to understand the effect on soil microbial communities during the initial years after land conversion. In the study, the influences of land-use conversion from double rice cropping (RR) to maize-maize (MM) and soybean-peanut (SP) double cropping systems on soil physical and chemical properties, and microbial community structure was studied after two years of the conversion in southern China. The results showed that land use conversion significantly changed soil properties, microbial communities and biomass. Soil pH significantly decreased by 0.50 and 0.52 after conversion to MM and SP, respectively. Soil TN and NH4-N also significantly decreased by 9%-15% and 60% after conversion to upland fields, respectively. The total PLFAs, bacterial, gram-positive bacterial (G+), gram-negative bacterial (G-) and actinomycetic PLFAs decreased significantly. The ng g-1 soil concentration of monounsaturated chain PLFAs 16:1ω7c and 18:1ω9t were significantly higher at paddy fields than at upland fields. No significant differences in soil properties, microbial communities and biomass were found between conversed MM and SP. Our results indicated that land use conversion, not crop type conversed had a significant effects on soil properties and microbial communities at the initial of land conversion. And soil pH was the key factor regulating the variations in soil microbial community structure after land use conversion from paddy to upland fields.

  7. Anaerobic N mineralization in paddy soils in relation to inundation management, physicochemical soil fractions, mineralogy and soil properties

    NASA Astrophysics Data System (ADS)

    Sleutel, Steven; Kader, Mohammed Abdul; Ara Begum, Shamim; De Neve, Stefaan

    2013-04-01

    Anaerobic N mineralization measured from (saturated) repacked soil cores from 25 paddy fields in Bangladesh and was previously found to negatively related to soil N content on a relative basis. This suggests that other factors like soil organic matter (SOM) quality or abiotic factors instead control the anaerobic N mineralization process. We therefore assessed different physical and chemical fractions of SOM, management factors and various soil properties as predictors for the net anaerobic N mineralization. 1° First, we assessed routinely analyzed soil parameters (soil N and soil organic carbon, texture, pH, oxalate- and pyrophosphate-extractable Fe, Al, and Mn, fixed-NH4 content). We found no significant influences of neither soil mineralogy nor the annual length of inundation on soil N mineralization. The anaerobic N mineralization correlated positively with Na-pyrophosphate-extractable Fe and negatively with pH (both at P<0.01). At this stage it is, however, not known if these relations between net evolution of NH4 and pH and Fe content are causal or indirect. 2° Second, the 25 samples collected from farmers' fields were physically fractionated into particulate OM and silt and clay associated OM. The silt and clay sized OM was further chemically fractionated by oxidation with 6%NaOCl to isolate an oxidation-resistant OM fraction, followed by extraction of mineral bound OM with 10%HF thereby isolating the HF-resistant OM. None of the physicochemical SOM fractions were found useful predictors anaerobic N mineralization. The linkage between these chemical soil N fractions and N supplying processes actually occurring in the soil thus appears to be weak. Regardless, we hypothesize that variation in strength of N-mineral and N-OM linkages is likely to explain variation in bio-availability of organic N and proneness to mineralization. Yet, in order to separate kinetically different soil N fractions we then postulated that an alternative approach would be required

  8. Effects of alternating wetting and drying versus continuous flooding on chromium fate in paddy soils.

    PubMed

    Xiao, Wendan; Ye, Xuezhu; Yang, Xiaoe; Li, Tingqiang; Zhao, Shouping; Zhang, Qi

    2015-03-01

    Anthropogenic chromium (Cr) pollution in soils poses a great threat to human health through the food chain. It is imperative to understand Cr fate under the range of conditions suitable for rice growth. In this study, the effects of irrigation managements on dynamics of porewater Cr(VI) concentrations in rice paddies and Cr distribution in rice were investigated with pot experiments under greenhouse conditions. Soil redox potential in continuous flooding (CF) treatments showed that reducing conditions remained for the whole duration of rice growing period, while soil redox potential in alternating wetting and drying (AWD) treatments showed that soil conditions alternately changed between reducing and oxic. As soil redox potential is an important factor affecting Cr(VI) reduction in paddy soils, dynamics of Cr(VI) concentration were clearly different under different irrigation managements. In CF treatments, porewater Cr(VI) concentrations decreased with time after planting, while in AWD treatments porewater Cr(VI) concentrations were increased and decreased alternately response to the irrigation cycles. Chromium(VI) concentrations in the CF treatments were lower than those in AWD treatments for most part of rice-growing season. Moreover, Cr concentrations in rice tissues were significantly influenced by irrigation with relatively higher values in the AWD treatments, which might be attributed to the higher porewater Cr(VI) concentrations in AWD treatments. Therefore, it would be better to use CF than AWD management in Cr-contaminated paddy soils to reduce Cr accumulation in rice, and thus to reduce the potential risk to human health. PMID:25546832

  9. Spatial variability of soil nutrient in paddy plantation: Sites FELCRA Seberang Perak

    NASA Astrophysics Data System (ADS)

    Kamarudin, H.; Adnan, N. A.; Mispan, M. R.; Athirah. A, A.

    2016-06-01

    The conventional methods currently used for rice cultivation in Malaysia are unable to give maximum yield although the yield production of paddy is increasing. This is due to the conversional method being unable to include soil properties as one of their parameters in agriculture management. Soil properties vary spatially in farm scale due to differences in topography, parent material, vegetation or land management and soil characteristics; also plantation productivity varies significantly over small spatial scales. Knowledge of spatial variability in soil fertility is important for site specific nutrient management. Analysis of spatial variability of soil nutrient of nitrogen (N), phosphorus (P) and potassium (K) were conducted in this study with the aid of GIS (i.e ArcGIS) and statistical softwares. In this study different temporal and depths of soil nutrient were extracted on the field and further analysis of N,P,K content were analysed in the chemical laboratory and using spatially technique in GIS sofware. The result indicated that for the Seberang Perak site of 58 hactares area, N and K are met minimum requirements nutrient content as outlines by the MARDI for paddy cultivation. However, P indicated poor condition in the study area; therefore the soil needs further attention and treatment.

  10. Metagenomic analysis revealed highly diverse microbial arsenic metabolism genes in paddy soils with low-arsenic contents.

    PubMed

    Xiao, Ke-Qing; Li, Li-Guan; Ma, Li-Ping; Zhang, Si-Yu; Bao, Peng; Zhang, Tong; Zhu, Yong-Guan

    2016-04-01

    Microbe-mediated arsenic (As) metabolism plays a critical role in global As cycle, and As metabolism involves different types of genes encoding proteins facilitating its biotransformation and transportation processes. Here, we used metagenomic analysis based on high-throughput sequencing and constructed As metabolism protein databases to analyze As metabolism genes in five paddy soils with low-As contents. The results showed that highly diverse As metabolism genes were present in these paddy soils, with varied abundances and distribution for different types and subtypes of these genes. Arsenate reduction genes (ars) dominated in all soil samples, and significant correlation existed between the abundance of arr (arsenate respiration), aio (arsenite oxidation), and arsM (arsenite methylation) genes, indicating the co-existence and close-relation of different As resistance systems of microbes in wetland environments similar to these paddy soils after long-term evolution. Among all soil parameters, pH was an important factor controlling the distribution of As metabolism gene in five paddy soils (p = 0.018). To the best of our knowledge, this is the first study using high-throughput sequencing and metagenomics approach in characterizing As metabolism genes in the five paddy soil, showing their great potential in As biotransformation, and therefore in mitigating arsenic risk to humans. PMID:26736050

  11. Factors affecting paddy soil arsenic concentration in Bangladesh: prediction and uncertainty of geostatistical risk mapping.

    PubMed

    Ahmed, Zia U; Panaullah, Golam M; DeGloria, Stephen D; Duxbury, John M

    2011-12-15

    Knowledge of the spatial correlation of soil arsenic (As) concentrations with environmental variables is needed to assess the nature and extent of the risk of As contamination from irrigation water in Bangladesh. We analyzed 263 paired groundwater and paddy soil samples covering highland (HL) and medium highland-1 (MHL-1) land types for geostatistical mapping of soil As and delineation of As contaminated areas in Tala Upazilla, Satkhira district. We also collected 74 non-rice soil samples to assess the baseline concentration of soil As for this area. The mean soil As concentrations (mg/kg) for different land types under rice and non-rice crops were: rice-MHL-1 (21.2)>rice-HL (14.1)>non-rice-MHL-1 (11.9)>non-rice-HL (7.2). Multiple regression analyses showed that irrigation water As, Fe, land elevation and years of tubewell operation are the important factors affecting the concentrations of As in HL paddy soils. Only years of tubewell operation affected As concentration in the MHL-1 paddy soils. Quantitatively similar increases in soil As above the estimated baseline-As concentration were observed for rice soils on HL and MHL-1 after 6-8 years of groundwater irrigation, implying strong retention of As added in irrigation water in both land types. Application of single geostatistical methods with secondary variables such as regression kriging (RK) and ordinary co-kriging (OCK) gave little improvement in prediction of soil As over ordinary kriging (OK). Comparing single prediction methods, kriging within strata (KWS), the combination of RK for HL and OCK for MHL-1, gave more accurate soil As predictions and showed the lowest misclassification of declaring a location "contaminated" with respect to 14.8 mg As/kg, the highest value obtained for the baseline soil As concentration. Prediction of soil As buildup over time indicated that 75% or the soils cropped to rice would contain at least 30 mg/L As by the year 2020. PMID:22055452

  12. [Accumulation of di-(2-ethylhexyl) phthalate in various genotype Ipomoea aquatica-paddy soil system].

    PubMed

    Cai, Quanying; Mo, Cehui; Zeng, Qiaoyun; Li, Yunhui; Xiao, Kai'en; Li, Haiqin; Xu, Guosheng; Wang, Boguang; Wu, Qingzhu

    2004-08-01

    Various genotypes of Ipomoea aquatica were pot-cultured on paddy soils with different pollution level of di-(2-ethylhexyl) phthalate (DEHP), and the concentrations of DEHP in plant and soil were determined by GC/MS. The results showed that the concentration of DEHP in plant varied directly with soil pollution level, and different genotypes of Ipomoea aquatica had significantly different concentrations of DEHP, which varied directly with leaf area. Soils grown with various genotypes of Ipomoea aquatica also had significantly different DEHP concentrations. The soil DEHP bioaccumulation factors (BCFs) of various Ipomoea aquatica genotypes were all under 1.0 and in inverse proportion to soil pollution level. The BCFs varied significantly among the genotypes of Ipomoea aquatica, with a relatively higher value for those genotypes with middle size leaves. PMID:15574007

  13. An examination of soil and water conservation practices in the paddy fields of Guilan province, Iran.

    PubMed

    Ashoori, Daryoush; Bagheri, Asghar; Allahyari, Mohammad S; Al-Rimawi, Ahmad S

    2016-06-01

    This study examined the use of soil and water conservation (SWC) practices among rice farmers in Iran. A random sample of 400 rice paddy farmers in the Foumanat plain of Guilan province, who use SWC measures, was drawn from a population of 52 thousand farmers. A two-part questionnaire was used to examine the level of utilization of SWC practices and to profile paddy farmers. Internal consistency was demonstrated with a coefficient alpha of 0.76, and the content and face validity of the instrument was confirmed by a panel of soil and water experts. Descriptive and analytical statistics were used to analyze the data. Results of ANOVA indicated that the mean levels of SWC practices vary considerably at the 0.01 level of significance by groups of age, education, non-agricultural income, production costs, yield, cultivated paddies and distance from home to the farm or to the main road. Similarly, significant differences were observed by groups of family size, rice production, ownership of livestock and profits from rice production at 0.05 level. The levels of experience in agriculture and ownership of poultry were found to have no significant effects on SWC practices. PMID:27276379

  14. Incorporating rice residues into paddy soils affects methylmercury accumulation in rice.

    PubMed

    Zhu, Huike; Zhong, Huan; Wu, Jialu

    2016-06-01

    Paddy fields are characterized by frequent organic input (e.g., fertilization and rice residue amendment), which may affect mercury biogeochemistry and bioaccumulation. To explore potential effects of rice residue amendment on methylmercury (MMHg) accumulation in rice, a mercury-contaminated paddy soil was amended with rice root (RR), rice straw (RS) or composted rice straw (CS), and planted with rice. Incorporating RS or CS increased grain MMHg concentration by 14% or 11%. The observed increases could be attributed to the elevated porewater MMHg levels and thus enhanced MMHg uptake by plants, as well as increased MMHg translocation to grain within plants. Our results indicated for the first time that rice residue amendment could significantly affect MMHg accumulation in rice grain, which should be considered in risk assessment of MMHg in contaminated areas. PMID:26974480

  15. Phytoremediation of arsenic contaminated paddy soils with Pteris vittata markedly reduces arsenic uptake by rice.

    PubMed

    Ye, Wen-Ling; Khan, M Asaduzzaman; McGrath, Steve P; Zhao, Fang-Jie

    2011-12-01

    Arsenic (As) accumulation in food crops such as rice is of major concern. To investigate whether phytoremediation can reduce As uptake by rice, the As hyperaccumulator Pteris vittata was grown in five contaminated paddy soils in a pot experiment. Over a 9-month period P. vittata removed 3.5-11.4% of the total soil As, and decreased phosphate-extractable As and soil pore water As by 11-38% and 18-77%, respectively. Rice grown following P. vittata had significantly lower As concentrations in straw and grain, being 17-82% and 22-58% of those in the control, respectively. Phytoremediation also resulted in significant changes in As speciation in rice grain by greatly decreasing the concentration of dimethylarsinic acid (DMA). In two soils the concentration of inorganic As in rice grain was decreased by 50-58%. The results demonstrate an effective stripping of bioavailable As from contaminated paddy soils thus reducing As uptake by rice. PMID:21840633

  16. Silica fertilization and nano-MnO₂ amendment on bacterial community composition in high arsenic paddy soils.

    PubMed

    Shao, Jihai; He, Yaxian; Zhang, Huiling; Chen, Anwei; Lei, Ming; Chen, Junfeng; Peng, Liang; Gu, Ji-Dong

    2016-03-01

    Silica fertilization and nano-MnO2 amendment are reported as useful approaches in lowering the accumulation of arsenic in rice grains, but the effects of silica fertilization or nano-MnO2 amendment on microbial community in the paddy soils containing high concentration of arsenic are still unknown. In order to elucidate this question, the structures and composition of microbial community in the paddy soils, in response to silica fertilization and nano-MnO2 amendment, were investigated using pyrosequencing technique. The results indicated that Proteobacteria, Chloroflexi, and Acidobacteria were the main dominating phyla in these paddy soils. A decrease in the relative abundance of Chloroflexi and Cyanobacteria, but an increase in the relative abundance of Acidobacteria was observed after silica fertilization and nano-MnO2 amendment. The changes of Acidobacteria, Chloroflexi, and Cyanobacteria were strongly correlated with pH and the concentration of bioavailable arsenic in the paddy soils. The α-diversity of bacteria in the paddy soils increased in response to silica fertilization at low amendment level, but decreased under silica or nano-MnO2 amendment at high amendment level. Results of β-diversity analysis indicated that the microbial communities in the control treatment shared more similarity with that of those received low level of nano-MnO2 amendment, and the two silica fertilization treatments also shared more similarity with each other. PMID:26563550

  17. ESTIMATION OF KOREAN PADDY FIELD SOIL PROPERTIES USING OPTICAL REFLECTANCE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An optical sensing approach based on diffuse reflectance has shown potential for rapid and reliable on-site estimation of soil properties. Important sensing ranges and the resulting regression models useful for soil property estimation have been reported. In this study, a similar approach was applie...

  18. Estimation of Korean paddy field soil properties using optical reflectance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An optical sensing approach based on diffuse reflectance has shown potential for rapid and reliable on-site estimation of soil properties. Important sensing ranges and the resulting regression models useful for soil property estimation have been reported. In this study, a similar approach was applie...

  19. Evaluation of potential effects of soil available phosphorus on soil arsenic availability and paddy rice inorganic arsenic content.

    PubMed

    Jiang, Wei; Hou, Qingye; Yang, Zhongfang; Zhong, Cong; Zheng, Guodong; Yang, Zhiqiang; Li, Jie

    2014-05-01

    The transfer of arsenic from paddy field to rice is a major exposure route of the highly toxic element to humans. The aim of our study is to explore the effects of soil available phosphorus on As uptake by rice, and identify the effects of soil properties on arsenic transfer from soil to rice under actual field conditions. 56 pairs of topsoil and rice samples were collected. The relevant parameters in soil and the inorganic arsenic in rice grains were analyzed, and then all the results were treated by statistical methods. Results show that the main factors influencing the uptake by rice grain include soil pH and available phosphorus. The eventual impact of phosphorus is identified as the suppression of As uptake by rice grains. The competition for transporters from soil to roots between arsenic and phosphorus in rhizosphere soil has been a dominant feature. PMID:24598788

  20. Heavy metal speciation and risk assessment in dry land and paddy soils near mining areas at Southern China.

    PubMed

    Liu, Guannan; Wang, Juan; Zhang, Erxi; Hou, Jing; Liu, Xinhui

    2016-05-01

    Heavy metal contamination of soils has been a long-standing environmental problem in many parts of the world, and poses enormous threats to ecosystem and human health. Speciation of heavy metals in soils is crucial to assessing environmental risks from contaminated soils. In this study, total concentrations and speciation of As, Cd, Cr, Cu, Mn, Ni, Pb, and Zn were measured for agricultural soils near mines along the Diaojiang River in Guangxi Zhuang Autonomy Region, China. The sources of heavy metals in soils also were identified to assess their effect on speciation distribution of soil heavy metals. Furthermore, the speciation distribution of Cd and Zn, main soil heavy metal pollutants, in dry land and paddy soils were compared. Results showed that there were two severely polluted regions near mine area reaching alarming pollution level. As, Cd, Pb, and Zn were more affected by mining activities, showing very strong pollution level in soils. The mean percentage of exchangeable and carbonate fraction was highest and up to 46.8 % for Cd, indicating a high environmental risk. Greater bioavailable fractions of As, Cd, Cu, Mn, Pb, and Zn were found in soils heavily polluted by mining activities, whereas Cr and Ni as geogenic elements in the stable residual fraction. In addition, in the dry land soils, reducible fraction proportion of Cd was higher than that in the paddy soils, whereas exchangeable and carbonate fraction of Cd was lower than that in the paddy soils. Oxidizable fraction of Zn was higher in the paddy soils than that in the dry land soils. The results indicate that the sources of soil heavy metals and land types affect heavy metal speciation in the soil and are significant for environmental risk assessment of soil heavy metal pollutions. PMID:26801928

  1. Radiocesium sorption in relation to clay mineralogy of paddy soils in Fukushima, Japan.

    PubMed

    Nakao, Atsushi; Ogasawara, Sho; Sano, Oki; Ito, Toyoaki; Yanai, Junta

    2014-01-15

    Relationships between Radiocesium Interception Potential (RIP) and mineralogical characteristics of the clay fraction isolated from 97 paddy soils (Hama-dori, n = 25; Naka-dori, n = 36; Aizu, n = 36) in Fukushima Prefecture, Japan were investigated to clarify the mineralogical factors controlling the (137)Cs retention ability of soils (half-life 30.1 y). Of all the fission products released by the Fukushima accident, (137)Cs is the most important long-term contributor to the environmental contamination. The RIP, a quantitative index of the (137)Cs retention ability, was determined for the soil clays. The composition of clay minerals in the soil clays was estimated from peak areas obtained using X-ray diffraction (XRD) analyses. The predominant clay mineral was smectite in soils from Hama-dori and Aizu, while this was variable for those from Naka-dori. Native K content of the soil clays was found to be an indicator of the amount of micaceous minerals. The average RIP for the 97 soil clays was 7.8 mol kg(-1), and ranged from 2.4 mol kg(-1) to 19.4 mol kg(-1). The RIP was significantly and positively correlated with native K content for each of the geographical regions, Hama-dori (r = 0.76, p < 0.001), Naka-dori (r = 0.43, p < 0.05), and Aizu (r = 0.76, P < 0.001), while it was not related to the relative abundance of smectite. The linear relationship between RIP and native K content not only indicate a large contribution of micaceous minerals to the (137)Cs retention ability of the soil clays, but also could be used to predict the (137)Cs retention ability of soil clays for other paddy fields in Fukushima and other areas. PMID:24055668

  2. Effects of redox conditions on the adsorption of dissolved organic matter to soil minerals and differently aged paddy soils

    NASA Astrophysics Data System (ADS)

    Sauerwein, Meike; Hanke, Alexander; Kaiser, Klaus; Kalbitz, Karsten

    2010-05-01

    Effects of redox conditions on the adsorption of dissolved organic matter to soil minerals and differently aged paddy soils Meike Sauerwein1, Alexander Hanke2, Klaus Kaiser3, Karsten Kalbitz2 1) Dept. of Soil Ecology, Bayreuth Centre of Ecology and Environmental Research (BayCEER), University of Bayreuth, 95440 Bayreuth, Germany, meike.sauerwein@gmail.com 2) Institute of ecosystem dynamics and biodiversity, University of Amsterdam, 1018 WV, Netherlands, a.hanke@uva.nl, k.kalbitz@uva.nl 3) Soil Sciences, Martin Luther University Halle, 06099 Halle, Germany, klaus.kaiser@landw.uni-halle.de Current knowledge on dissolved organic matter (DOM) in soils is based mainly on observations and experiments in aerobic environments. Adsorption to soil minerals is an important mechanism of DOM retention and stabilization against microbial decay under oxic conditions. Under anoxic conditions where hydrous iron oxides, the potential main adsorbents of DOM, possibly dissolve, the importance of adsorption seems questionable. Therefore, we studied the adsorption of DOM to selected soil minerals and to mineral soils under oxic and anoxic conditions. In detail, we tested the following hypotheses: 1. Minerals and soils adsorb less DOM under anoxic conditions than under oxic ones. 2. The reduced adsorption under anoxic conditions is result of the smaller adsorption to hydrous Fe oxides whereas adsorption to clay minerals and Al hydroxides is not sensitive to changes in redox conditions 3. DOM adsorption will increase with the number of redox cycles, thus time of soil formation, due to increasing contents of poorly crystalline Fe oxides. This will, however, cause a stronger sensitivity to redox changes as poor crystalline Fe oxides are more reactive. 4. Aromatic compounds, being preferentially adsorbed under oxic conditions, will be less strongly adsorbed under anoxic conditions. We chose paddy soils as models because their periodically and regular exposure to changing redox cycles, with

  3. Effect of simulated tillage on microbial autotrophic CO2 fixation in paddy and upland soils

    NASA Astrophysics Data System (ADS)

    Ge, Tida; Wu, Xiaohong; Liu, Qiong; Zhu, Zhenke; Yuan, Hongzhao; Wang, Wei; Whiteley, A. S.; Wu, Jinshui

    2016-01-01

    Tillage is a common agricultural practice affecting soil structure and biogeochemistry. To evaluate how tillage affects soil microbial CO2 fixation, we incubated and continuously labelled samples from two paddy soils and two upland soils subjected to simulated conventional tillage (CT) and no-tillage (NT) treatments. Results showed that CO2 fixation (14C-SOC) in CT soils was significantly higher than in NT soils. We also observed a significant, soil type- and depth-dependent effect of tillage on the incorporation rates of labelled C to the labile carbon pool. Concentrations of labelled C in the carbon pool significantly decreased with soil depth, irrespective of tillage. Additionally, quantitative PCR assays revealed that for most soils, total bacteria and cbbL-carrying bacteria were less abundant in CT versus NT treatments, and tended to decrease in abundance with increasing depth. However, specific CO2 fixation activity was significantly higher in CT than in NT soils, suggesting that the abundance of cbbL-containing bacteria may not always reflect their functional activity. This study highlights the positive effect of tillage on soil microbial CO2 fixation, and the results can be readily applied to the development of sustainable agricultural management.

  4. Effect of simulated tillage on microbial autotrophic CO2 fixation in paddy and upland soils.

    PubMed

    Ge, Tida; Wu, Xiaohong; Liu, Qiong; Zhu, Zhenke; Yuan, Hongzhao; Wang, Wei; Whiteley, A S; Wu, Jinshui

    2016-01-01

    Tillage is a common agricultural practice affecting soil structure and biogeochemistry. To evaluate how tillage affects soil microbial CO2 fixation, we incubated and continuously labelled samples from two paddy soils and two upland soils subjected to simulated conventional tillage (CT) and no-tillage (NT) treatments. Results showed that CO2 fixation ((14)C-SOC) in CT soils was significantly higher than in NT soils. We also observed a significant, soil type- and depth-dependent effect of tillage on the incorporation rates of labelled C to the labile carbon pool. Concentrations of labelled C in the carbon pool significantly decreased with soil depth, irrespective of tillage. Additionally, quantitative PCR assays revealed that for most soils, total bacteria and cbbL-carrying bacteria were less abundant in CT versus NT treatments, and tended to decrease in abundance with increasing depth. However, specific CO2 fixation activity was significantly higher in CT than in NT soils, suggesting that the abundance of cbbL-containing bacteria may not always reflect their functional activity. This study highlights the positive effect of tillage on soil microbial CO2 fixation, and the results can be readily applied to the development of sustainable agricultural management. PMID:26795428

  5. Effect of simulated tillage on microbial autotrophic CO2 fixation in paddy and upland soils

    PubMed Central

    Ge, Tida; Wu, Xiaohong; Liu, Qiong; Zhu, Zhenke; Yuan, Hongzhao; Wang, Wei; Whiteley, A. S.; Wu, Jinshui

    2016-01-01

    Tillage is a common agricultural practice affecting soil structure and biogeochemistry. To evaluate how tillage affects soil microbial CO2 fixation, we incubated and continuously labelled samples from two paddy soils and two upland soils subjected to simulated conventional tillage (CT) and no-tillage (NT) treatments. Results showed that CO2 fixation (14C-SOC) in CT soils was significantly higher than in NT soils. We also observed a significant, soil type- and depth-dependent effect of tillage on the incorporation rates of labelled C to the labile carbon pool. Concentrations of labelled C in the carbon pool significantly decreased with soil depth, irrespective of tillage. Additionally, quantitative PCR assays revealed that for most soils, total bacteria and cbbL-carrying bacteria were less abundant in CT versus NT treatments, and tended to decrease in abundance with increasing depth. However, specific CO2 fixation activity was significantly higher in CT than in NT soils, suggesting that the abundance of cbbL-containing bacteria may not always reflect their functional activity. This study highlights the positive effect of tillage on soil microbial CO2 fixation, and the results can be readily applied to the development of sustainable agricultural management. PMID:26795428

  6. [Influence of paddy rice-upland crop rotation of cold-waterlogged paddy field on crops produc- tion and soil characteristics].

    PubMed

    Wang, Fei; Li, Qing-hua; Lin, Cheng; He, Chun-mei; Zhong, Shao-jie; Li, Yu; Lin, Xin-jian; Huang, Jian-cheng

    2015-05-01

    Two consecutive years (4-crop) experiments were conducted to study the influence of different paddy rice-upland crop rotation in cold-waterlogged paddy field on the growth of crops and soil characteristics. The result showed that compared with the rice-winter fallow (CK) pattern, the two-year average yield of paddy rice under four rotation modes, including rape-rice (R-R), spring corn-rice (C-R), Chinese milk vetch-rice (M-R) and bean-rice (B-R), were increased by 5.3%-26.7%, with significant difference observed in C-R and R-R patterns. Except for M-R pattern, the annual average total economic benefits were improved by 79.0%-392.4% in all rotation pattern compared with the CK, and the ration of output/input was enhanced by 0.06-0.72 unit, with the most significant effect found in the C-R pattern. Likewise, compared with the CK, the contents of chlorophyll and carotenoid, and net photosynthetic rate (Pn) of rice plant were all increased during the full-tillering stage of rice in all rotation patterns. The rusty lines and rusty spots of soils were more obvious compared with the CK during the rice harvest, particularly in R-R, C-R and B-R patterns. The ratio of water-stable soil macro aggregates of plough layer of soil (> 2 mm) decreased at different levels in all rotation patterns while the ratios of middle aggregate (0.25-2 mm, expect for M-R) and micro aggregate of soil (< 0.25 mm) were opposite. There was a decreasing trend for soil active reducing agents in all rotation patterns, whereas the available nutrient increased. The amounts of soil bacteria in C-R and B-R patterns, fungi in B-R rotation pattern, cellulose bacteria in R-R, C-R and B-R patterns and N-fixing bacteria in B-R pattern were improved by 285.7%-403.0%, 221.7%, 64.6-92.2% and 162.2%, respectively. Moreover, the differences in all microorganisms were significant. Thus, based on the experimental results of cold-waterlogged paddy field, it was concluded that changing from single cropping rice system

  7. Arsenic speciation and volatilization from flooded paddy soils amended with different organic matters.

    PubMed

    Huang, Hai; Jia, Yan; Sun, Guo-Xin; Zhu, Yong-Guan

    2012-02-21

    Arsenic (As) methylation and volatilization in soil can be increased after organic matter (OM) amendment, though the factors influencing this are poorly understood. Herein we investigate how amended OM influences As speciation as well as how it alters microbial processes in soil and soil solution during As volatilization. Microcosm experiments were conducted on predried and fresh As contaminated paddy soils to investigate microbial mediated As speciation and volatilization under different OM amendment conditions. These experiments indicated that the microbes attached to OM did not significantly influence As volatilization. The arsine flux from the treatment amended with 10% clover (clover-amended treatment, CT) and dried distillers grain (DDG) (DDG-amended treatment, DT2) were significantly higher than the control. Trimethylarsine (TMAs) was the dominant species in arsine derived from CT, whereas the primary arsine species from DT2 was TMAs and arsine (AsH(3)), followed by monomethylarsine (MeAsH(2)). The predominant As species in the soil solutions of CT and DT2 were dimethylarsinic acid (DMAA) and As(V), respectively. OM addition increased the activities of arsenite-oxidizing bacteria (harboring aroA-like genes), though they did not increase or even decrease the abundance of arsenite oxidizers. In contrast, the abundance of arsenate reducers (carrying the arsC gene) was increased by OM amendment; however, significant enhancement of activity of arsenate reducers was observed only in CT. Our results demonstrate that OM addition significantly increased As methylation and volatilization from the investigated paddy soil. The physiologically active bacteria capable of oxidization, reduction, and methylation of As coexisted and mediated the As speciation in soil and soil solution. PMID:22295880

  8. In Situ Measurement of Some Soil Properties in Paddy Soil Using Visible and Near-Infrared Spectroscopy

    PubMed Central

    Wenjun, Ji; Zhou, Shi; Jingyi, Huang; Shuo, Li

    2014-01-01

    In situ measurements with visible and near-infrared spectroscopy (vis-NIR) provide an efficient way for acquiring soil information of paddy soils in the short time gap between the harvest and following rotation. The aim of this study was to evaluate its feasibility to predict a series of soil properties including organic matter (OM), organic carbon (OC), total nitrogen (TN), available nitrogen (AN), available phosphorus (AP), available potassium (AK) and pH of paddy soils in Zhejiang province, China. Firstly, the linear partial least squares regression (PLSR) was performed on the in situ spectra and the predictions were compared to those with laboratory-based recorded spectra. Then, the non-linear least-square support vector machine (LS-SVM) algorithm was carried out aiming to extract more useful information from the in situ spectra and improve predictions. Results show that in terms of OC, OM, TN, AN and pH, (i) the predictions were worse using in situ spectra compared to laboratory-based spectra with PLSR algorithm (ii) the prediction accuracy using LS-SVM (R2>0.75, RPD>1.90) was obviously improved with in situ vis-NIR spectra compared to PLSR algorithm, and comparable or even better than results generated using laboratory-based spectra with PLSR; (iii) in terms of AP and AK, poor predictions were obtained with in situ spectra (R2<0.5, RPD<1.50) either using PLSR or LS-SVM. The results highlight the use of LS-SVM for in situ vis-NIR spectroscopic estimation of soil properties of paddy soils. PMID:25153132

  9. Speciation and release kinetics of zinc in contaminated paddy soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Zinc is an important nutrient for plants, but it can be toxic at high concentrations. The solubility and speciation of Zn is controlled by many factors, especially soil pH and Eh, which can vary in lowland rice culture. This study determined Zn speciation and release kinetics in Cd-Zn co-contamina...

  10. Eco-stoichiometric alterations in paddy soil ecosystem driven by phosphorus application.

    PubMed

    Li, Xia; Wang, Hang; Gan, Shaohua; Jiang, Daqian; Tian, Guangming; Zhang, Zhijian

    2013-01-01

    Agricultural fertilization may change processes of elemental biogeochemical cycles and alter the ecological function. Ecoenzymatic stoichiometric feature plays a critical role in global soil carbon (C) metabolism, driving element cycles, and mediating atmospheric composition in response to agricultural nutrient management. Despite the importance on crop growth, the role of phosphorous (P) in compliance with eco-stoichiometry on soil C and nitrogen (N) sequestration in the paddy field remains poorly understood in the context of climate change. Here, we collected soil samples from a field experiment after 6 years of chemical P application at a gradient of 0 (P-0), 30 (P-30), 60 (P-60), and 90 (P-90) kg ha(-1) in order to evaluate the role of P on stoichiometric properties in terms of soil chemical, microbial biomass, and eco-enzyme activities as well as greenhouse gas (GHG: CO2, N2O and CH4) emissions. Continuous P input increased soil total organic C and N by 1.3-9.2% and 3%-13%, respectively. P input induced C and N limitations as indicated by the decreased ratio of C:P and N:P in the soil and microbial biomass. A synergistic mechanism among the ecoenzymatic stoichiometry, which regulated the ecological function of microbial C and N acquisition and were stoichiometrically related to P input, stimulated soil C and N sequestration in the paddy field. The lower emissions of N2O and CH4 under the higher P application (P-60 and P-90) in July and the insignificant difference in N2O emission in August compared to P-30; however, continuous P input enhanced CO2 fluxes for both samplings. There is a technical conflict for simultaneously regulating three types of GHGs in terms of the eco-stoichiometry mechanism under P fertilization. Thus, it is recommended that the P input in paddy fields not exceed 60 kg ha(-1) may maximize soil C sequestration, minimize P export, and guarantee grain yields. PMID:23667435

  11. Arsenic dissolution from Japanese paddy soil by a dissimilatory arsenate-reducing bacterium Geobacter sp. OR-1.

    PubMed

    Ohtsuka, Toshihiko; Yamaguchi, Noriko; Makino, Tomoyuki; Sakurai, Kazuhiro; Kimura, Kenta; Kudo, Keitaro; Homma, Eri; Dong, Dian Tao; Amachi, Seigo

    2013-06-18

    Dissimilatory As(V) (arsenate)-reducing bacteria may play an important role in arsenic release from anoxic sediments in the form of As(III) (arsenite). Although respiratory arsenate reductase genes (arrA) closely related to Geobacter species have been frequently detected in arsenic-rich sediments, it is still unclear whether they directly participate in arsenic release, mainly due to lack of pure cultures capable of arsenate reduction. In this study, we isolated a novel dissimilatory arsenate-reducing bacterium, strain OR-1, from Japanese paddy soil, and found that it was phylogenetically closely related to Geobacter pelophilus. OR-1 also utilized soluble Fe(III), ferrihydrite, nitrate, and fumarate as electron acceptors. OR-1 catalyzed dissolution of arsenic from arsenate-adsorbed ferrihydrite, while Geobacter metallireducens GS-15 did not. Furthermore, inoculation of washed cells of OR-1 into sterilized paddy soil successfully restored arsenic release. Arsenic K-edge X-ray absorption near-edge structure analysis revealed that strain OR-1 reduced arsenate directly on the soil solid phase. Analysis of putative ArrA sequences from paddy soils suggested that Geobacter-related bacteria, including those closely related to OR-1, play an important role in arsenic release from paddy soils. Our results provide direct evidence for arsenic dissolution by Geobacter species and support the hypothesis that Geobacter species play a significant role in reduction and mobilization of arsenic in flooded soils and anoxic sediments. PMID:23668621

  12. Conversion of upland to paddy field specifically alters the community structure of archaeal ammonia oxidizers in an acid soil

    NASA Astrophysics Data System (ADS)

    Alam, M. S.; Ren, G. D.; Lu, L.; Zheng, Y.; Peng, X. H.; Jia, Z. J.

    2013-08-01

    The function of ammonia-oxidizing archaea (AOA) and bacteria (AOB) depends on the major energy-generating compounds (i.e., ammonia and oxygen). The diversification of AOA and AOB communities along ecological gradients of substrate availability in a complex environment have been much debated but rarely tested. In this study, two ecosystems of maize and rice crops under different fertilization regimes were selected to investigate the community diversification of soil AOA and AOB upon conversion of an upland field to a paddy field and long-term field fertilization in an acid soil. Real-time quantitative polymerase chain reaction of ammonia monooxygenase (amoA) genes demonstrated that the abundance of AOA was significantly stimulated after conversion of upland to paddy soils for more than 100 yr, whereas a slight decline in AOB numbers was observed. Denaturing gradient gel electrophoresis fingerprints of amoA genes further revealed remarkable changes in the community compositions of AOA after conversion of aerobic upland to flooded paddy field. Sequencing analysis revealed that upland soil was dominated by AOA within the soil group 1.1b lineage, whereas the marine group 1.1a-associated lineage predominated in AOA communities in paddy soils. Irrespective of whether the soil was upland or paddy soil, long-term field fertilization led to increased abundance of amoA genes in AOA and AOB compared with control treatments (no fertilization), whereas archaeal amoA gene abundances outnumbered their bacterial counterparts in all samples. Phylogenetic analyses of amoA genes showed that Nitrosospira cluster-3-like AOB dominated bacterial ammonia oxidizers in both paddy and upland soils, regardless of fertilization treatment. The results of this study suggest that the marine group 1.1a-associated AOA will be better adapted to the flooded paddy field than AOA ecotypes of the soil group 1.1b lineage, and indicate that long-term flooding is the dominant selective force driving the

  13. Assessment of heavy metal contamination of surface soils from typical paddy terrace wetlands on the Yunnan Plateau of China

    NASA Astrophysics Data System (ADS)

    Bai, Junhong; Xiao, Rong; Gong, Adu; Gao, Haifeng; Huang, Laibin

    Little research has been done to investigate heavy metal contamination in paddy soils along different altitudes under domestic sewage irrigation. Total concentrations of As, Cr, Cd and Pb were determined in surface paddy soils from Mengpin (MP) and Quanfuzhang (QFZ) paddy terraces on the Yunnan Plateau of China in December, 2004, in order to assess their contamination status. Results showed that the average concentrations of As and Cd in both terrace soils were significantly ( p < 0.01) greater than the reference concentrations, while lower for Pb in both soils. However, as for Cr, the average concentrations are higher in MP soils while lower in QFZ soil than the reference concentration, while. Compared with MP soils, QFZ soils had lower heavy metal concentrations. However, only Cd greatly exceeded the guide value of soil quality. The contamination factor ( Cfi) values were generally moderate for As and Cd, and low for Pb in both sites. As for Cr, they were moderate in MP soils but low in QFZ soils. The contamination degree ( C d) values were generally moderate, showing a decreasing tendency along the increasing altitudes in MP terrace, while slowly increasing tendency in QFZ terrace.

  14. [Effects of temperature on organic carbon mineralization in paddy soils with different clay content].

    PubMed

    Ren, Xiu-E; Tong, Cheng-Li; Sun, Zhong-Lin; Tang, Guo-Yong; Xiao, He-Ai; Wu, Jin-Shui

    2007-10-01

    An incubation test with three kinds of paddy soil (sandy loam, clay loam, and silty clay soils) in subtropical region was conducted at 10, 15, 20, 25 and 30 degrees C to examine the response of the mineralization of soil organic carbon (SOC) to temperature change. The results showed that during the period of 160 d incubation, the accumulative mineralized amount of SOC in sandy loam, clay loam, and silty clay soils at 30 degrees C was 3.5, 5.2 and 4.7 times as much as that at 10 degrees C, respectively. The mineralization rate was lower and relatively stable at lower temperatures (< or = 20 C), but was higher at the beginning of incubation and decreased and became stable as the time prolonged at higher temperatures (> or = 25 degrees C). During incubation, the temperature coefficient (Q10) of SOC mineralization in test soils fluctuated, with an average Q10 in sandy loam, clay loam, and silty clay soils being 1.92, 2.37 and 2.32, respectively. There was a positive exponential correlation between SOC mineralization constant k and temperature (P < 0.01), and the response of SOC mineralization to temperature change was in the order of clay loam soil > silty clay soil > sandy loam soil. PMID:18163305

  15. Transport of Soil Halides through Rice Paddies: A Viable Mechanism for Rapid Dispersion of the Soil Halide Reservoir

    NASA Astrophysics Data System (ADS)

    Redeker, K. R.; Manley, S.; Wang, N.; Cicerone, R.

    2002-05-01

    On short time scales (1-10 years) soil halide concentrations have been assumed to be primarily driven by leaching and deposition processes. Recent results however, have shown that terrestrial plants volatilize soil halides in the form of methyl halides. Emissions of methyl chloride, methyl bromide and methyl iodide represent major pathways for delivery of inorganic halogen radicals to the atmosphere. Inorganic halogen radicals destroy ozone in the stratosphere and modify the oxidative capacity of the lower atmosphere. We have previously shown that rice paddies emit methyl halides and that emissions depend on growth stage of the rice plant as well as field water management. We show here that rice grown in a greenhouse at UCI is capable of volatilizing and/or storing up to 30%, 5%, and 10% of the available chloride, bromide and iodide within the top meter of soil. The percent of plant tissue halide volatilized as methyl halide over the course of the season is calculated to be 0.05%, 0.25% and 85.0% for chloride, bromide and iodide. We compare our greenhouse soil halide concentrations to other commercial rice fields around the world and estimate the e-folding time for soil halides within each region. We suggest that rice agriculture is the driving removal mechanism for halides within rice paddies and that terrestrial plants play a larger role in global cycling of halides than previously estimated.

  16. Effects of Carbon in Flooded Paddy Soils: Implications for Microbial Activity and Arsenic Mobilization

    NASA Astrophysics Data System (ADS)

    Avancha, S.; Boye, K.

    2014-12-01

    In the Mekong delta in Cambodia, naturally occurring arsenic (originating from erosion in the Himalaya Mountains) in paddy soils is mobilized during the seasonal flooding. As a consequence, rice grown on the flooded soils may take up arsenic and expose people eating the rice to this carcinogenic substance. Microbial activity will enhance or decrease the mobilization of arsenic depending on their metabolic pathways. Among the microbes naturally residing in the soil are denitrifying bacteria, sulfate reducers, metal reducers (Fe, Mn), arsenic reducers, methanogens, and fermenters, whose activity varies based on the presence of oxygen. The purpose of the experiment was to assess how different amendments affect the microbial activity and the arsenic mobilization during the transition from aerobic to anaerobic metabolism after flooding of naturally contaminated Cambodian soil. In a batch experiment, we investigated how the relative metabolic rate of naturally occurring microbes could vary with different types of organic carbon. The experiment was designed to measure the effects of various sources of carbon (dried rice straw, charred rice straw, manure, and glucose) on the microbial activity and arsenic release in an arsenic-contaminated paddy soil from Cambodia under flooded conditions. All amendments were added based on the carbon content in order to add 0.036 g of carbon per vial. The soil was flooded with a 10mM TRIS buffer solution at pH 7.04 in airtight 25mL serum vials and kept at 25 °C. We prepared 14 replicates per treatment to sample both gas and solution. On each sampling point, the solution replicates were sampled destructively. The gas replicates continued on and were sampled for both gas and solution on the final day of the experiment. We measured pH, total arsenic, methane, carbon dioxide, and nitrous oxide at 8 hours, 1.5 days, 3.33 days, and 6.33 days from the start of the experiment.

  17. Efficient Arsenic Methylation and Volatilization Mediated by a Novel Bacterium from an Arsenic-Contaminated Paddy Soil.

    PubMed

    Huang, Ke; Chen, Chuan; Zhang, Jun; Tang, Zhu; Shen, Qirong; Rosen, Barry P; Zhao, Fang-Jie

    2016-06-21

    Microbial arsenic (As) methylation and volatilization are important processes controlling the As biogeochemical cycle in paddy soils. To further understand these processes, we isolated a novel bacterial strain, SM-1, from an As-contaminated paddy soil. SM-1 showed strong As methylation and volatilization abilities, converting almost all arsenite (10 μM) to dimethylarsenate and trimethylarsenic oxide in the medium and trimethylarsine gas into the headspace within 24 h, with trimethylarsine accounting for nearly half of the total As. On the basis of the 16S rRNA sequence, strain SM-1 represents a new species in a new genus within the family Cytophagaceae. Strain SM-1 is abundant in the paddy soil and inoculation of SM-1 greatly enhanced As methylation and volatilization in the soil. An arsenite methyltransferase gene (ArarsM) was cloned from SM-1. When expressed in Escherichia coli, ArArsM conferred the As methylation and volatilization abilities to E. coli and increased its resistance to arsenite. The high As methylation and volatilization abilities of SM-1 are likely attributed to an efficient ArArsM enzyme coupled with low arsenite efflux. These results suggest that strain SM-1 plays an important role in As methylation and volatilization in the paddy soil and has a great potential for As bioremediation. PMID:27258163

  18. The key microorganisms for anaerobic degradation of pentachlorophenol in paddy soil as revealed by stable isotope probing.

    PubMed

    Tong, Hui; Liu, Chengshuai; Li, Fangbai; Luo, Chunling; Chen, Manjia; Hu, Min

    2015-11-15

    Pentachlorophenol (PCP) is a common residual persistent pesticide in paddy soil and has resulted in harmful effect on soil ecosystem. The anaerobic microbial transformation of PCP, therefore, has been received much attentions, especially the functional microbial communities for the reductive transformation. However, the key functional microorganisms for PCP mineralization in the paddy soil still remain unknown. In this work, DNA-based stable isotope probing (SIP) was applied to explore the key microorganisms responsible for PCP mineralization in paddy soil. The SIP results indicated that the dominant bacteria responsible for PCP biodegradation belonged to the genus Dechloromonas of the class β-Proteobacteria. In addition, the increased production of (13)CH4 and (13)CO2 indicated that the addition of lactate enhanced the rate of biodegradation and mineralization of PCP. Two archaea classified as the genera of Methanosaeta and Methanocella of class Methanobacteria were enriched in the heavy fraction when with lactate, whereas no archaea was detected in the absence of lactate. These findings provide direct evidence for the species of bacteria and archaea responsible for anaerobic PCP or its breakdown products mineralization and reveal a new insight into the microorganisms linked with PCP degradation in paddy soil. PMID:26073380

  19. Differential contributions of ammonia oxidizers and nitrite oxidizers to nitrification in four paddy soils

    PubMed Central

    Wang, Baozhan; Zhao, Jun; Guo, Zhiying; Ma, Jing; Xu, Hua; Jia, Zhongjun

    2015-01-01

    Rice paddy fields are characterized by regular flooding and nitrogen fertilization, but the functional importance of aerobic ammonia oxidizers and nitrite oxidizers under unique agricultural management is poorly understood. In this study, we report the differential contributions of ammonia-oxidizing archaea (AOA), bacteria (AOB) and nitrite-oxidizing bacteria (NOB) to nitrification in four paddy soils from different geographic regions (Zi-Yang (ZY), Jiang-Du (JD), Lei-Zhou (LZ) and Jia-Xing (JX)) that are representative of the rice ecosystems in China. In urea-amended microcosms, nitrification activity varied greatly with 11.9, 9.46, 3.03 and 1.43 μg NO3−-N g−1 dry weight of soil per day in the ZY, JD, LZ and JX soils, respectively, over the course of a 56-day incubation period. Real-time quantitative PCR of amoA genes and pyrosequencing of 16S rRNA genes revealed significant increases in the AOA population to various extents, suggesting that their relative contributions to ammonia oxidation activity decreased from ZY to JD to LZ. The opposite trend was observed for AOB, and the JX soil stimulated only the AOB populations. DNA-based stable-isotope probing further demonstrated that active AOA numerically outcompeted their bacterial counterparts by 37.0-, 10.5- and 1.91-fold in 13C-DNA from ZY, JD and LZ soils, respectively, whereas AOB, but not AOA, were labeled in the JX soil during active nitrification. NOB were labeled to a much greater extent than AOA and AOB, and the addition of acetylene completely abolished the assimilation of 13CO2 by nitrifying populations. Phylogenetic analysis suggested that archaeal ammonia oxidation was predominantly catalyzed by soil fosmid 29i4-related AOA within the soil group 1.1b lineage. Nitrosospira cluster 3-like AOB performed most bacterial ammonia oxidation in the ZY, LZ and JX soils, whereas the majority of the 13C-AOB in the JD soil was affiliated with the Nitrosomona communis lineage. The 13C-NOB was overwhelmingly

  20. Seasonal Transition of Active Bacterial and Archaeal Communities in Relation to Water Management in Paddy Soils

    PubMed Central

    Itoh, Hideomi; Ishii, Satoshi; Shiratori, Yutaka; Oshima, Kenshiro; Otsuka, Shigeto; Hattori, Masahira; Senoo, Keishi

    2013-01-01

    Paddy soils have an environment in which waterlogging and drainage occur during the rice growing season. Fingerprinting analysis based on soil RNA indicated that active microbial populations changed in response to water management conditions, although the fundamental microbial community was stable as assessed by DNA-based fingerprinting analysis. Comparative clone library analysis based on bacterial and archaeal 16S rRNAs (5,277 and 5,436 clones, respectively) revealed stable and variable members under waterlogged or drained conditions. Clones related to the class Deltaproteobacteria and phylum Euryarchaeota were most frequently obtained from the samples collected under both waterlogged and drained conditions. Clones related to syntrophic hydrogen-producing bacteria, hydrogenotrophic methanogenic archaea, rice cluster III, V, and IV, and uncultured crenarchaeotal group 1.2 appeared in greater proportion in the samples collected under waterlogged conditions than in those collected under drained conditions, while clones belonging to rice cluster VI related to ammonia-oxidizing archaea (AOA) appeared at higher frequency in the samples collected under drained conditions than in those collected under waterlogged conditions. These results suggested that hydrogenotrophic methanogenesis may become active under waterlogged conditions, whereas ammonia oxidation may progress by rice cluster VI becoming active under drained conditions in the paddy field. PMID:24005888

  1. Field screening of cowpea cultivars for alkaline soil tolerance

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cowpea or Southernpea [Vigna unguiculata (L.) Walp.] is an important legume crop used as a feed for livestock, as a green vegetable and for consumption of its dry beans which provide 22-25% protein. The crop is very sensitive to alkaline soil conditions. When grown at soil pH of 7.5 or higher, cowp...

  2. Yield performance of cowpea genotypes grown in alkaline soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cowpea or Southernpea [Vigna unguiculata (L.) Walp.] is an important legume crop used as a feed for livestock, as a green vegetable and for consumption of its dry beans which provide 22-25% protein. The crop is very sensitive to alkaline soil conditions. When grown at soil pH of 7.5 or higher, cowp...

  3. Impact of model uncertainty on soil quality standards for cadmium in rice paddy fields.

    PubMed

    Römkens, P F A M; Brus, D J; Guo, H Y; Chu, C L; Chiang, C M; Koopmans, G F

    2011-08-01

    At present, soil quality standards used for agriculture do not consider the influence of pH and CEC on the uptake of pollutants by crops. A database with 750 selected paired samples of cadmium (Cd) in soil and paddy rice was used to calibrate soil to plant transfer models using the soil metal content, pH, and CEC or soil Cd and Zn extracted by 0.01 M CaCl₂ as explanatory variables. The models were validated against a set of 2300 data points not used in the calibration. These models were then used inversely to derive soil quality standards for Japonica and Indica rice cultivars based on the food quality standards for rice. To account for model uncertainty, strict soil quality standards were derived considering a maximum probability that rice exceeds the food quality standard equal to 10 or 5%. Model derived soil standards based on Aqua Regia ranged from less than 0.3 mg kg⁻¹ for Indica at pH 4.5 to more than 6 mg kg⁻¹ for Japonica-type cultivars in clay soils at pH 7. Based on the CaCl₂ extract, standards ranged from 0.03 mg kg⁻¹ Cd for Indica cultivars to 0.1 mg kg⁻¹ Cd for Japonica cultivars. For both Japonica and Indica-type cultivars, the soil quality standards must be reduced by a factor of 2 to 3 to obtain the strict standards. The strong impact of pH and CEC on soil quality standards implies that it is essential to correct for soil type when deriving national or local standards. Validation on the remaining 2300 samples indicated that both types of models were able to accurately predict (> 92%) whether rice grown on a specific soil will meet the food quality standard used in Taiwan. PMID:21632090

  4. Paddy soil nutrient assessment using visible and near infrared reflectance spectroscopy

    NASA Astrophysics Data System (ADS)

    Gholizadeh, A.; Saberioon, M. M.; Amin, M. S. M.

    The ability of obtaining soil properties estimations from time and cost efficient remotely sensed techniques has been identified as a valuable technique as there is a great demand for larger amounts of good quality and inexpensive soil data to be used in environmental monitoring, modelling and precision agriculture. Visible (Vis) and Near Infrared (NIR) spectroscopy provides a good alternative that may be used to enhance or replace conventional methods of soil analysis. The aim of this paper is to evaluate the abilities of Vis (350-700 nm) and near infrared (700-2500 nm) for prediction of soil nutrients. In this instance we implemented Savitzky-Golay algorithm and Stepwise Multiple Linear Regression (SMLR) to construct calibration models. The soil nutrients examined were soil Total Nitrogen (N), Available Phosphorus (P) and Exchangeable Potassium (K). Our results revealed the accuracy of SMLR prediction in each of the Vis and NIR spectral regions. The NIR produced more accurate predictions for N and K; however, higher significant correlation was obtained using the Vis for available P. This work demonstrated Vis and NIR spectroscopy could be considered as a good tool to assess soil nutrients in Malaysian paddy fields.

  5. Spatial variability of soil available Zn and Cu in paddy rice fields of China

    NASA Astrophysics Data System (ADS)

    Liu, Xingmei; Xu, Jianming; Zhang, Minghua; Si, Bingcheng; Zhao, Keli

    2008-10-01

    As a source of nutrient supplements, the deficiency or excess of micronutrients in soil is directly connected to the plant uptake and, thereby, status of micronutrients in the human population. Proper management of micronutrients requires an understanding of the variations of soil micronutrients across the fields. This study is to investigate the spatial patterns of soil available Zn and Cu in paddy rice fields. Four hundred and sixty three soil samples were taken in Hangzhou-Jiaxing-Huzhou (HJH) watershed in Zhejiang Province, China, and available Zn and Cu were analyzed using an atomic adsorption spectrometer. Geostatistical semivariograms analysis indicated that the available Zn and Cu were best fitted to a spherical model with a range of 40.5 and 210.4 km, respectively. There were moderate spatial dependences for Zn and Cu over a long distance and the dependence were attributed to soil types and anthropogenic activities. The overlay analysis of spatial patterns and soil types gave us greater understanding about how intrinsic factors affect the spatial variation of available micronutrients. Based on the above, macroscopically regionalized management of soil available micronutrients and the implications to potential risk were discussed.

  6. [Effects and mechanism of alkaline wastes application and zinc fertilizer addition on Cd bioavailability in contaminated soil].

    PubMed

    Liu, Zhao-Bing; Ji, Xiong-Hui; Tian, Fa-Xiang; Peng, Hua; Wu, Jia-Mei; Shi, Li-Hong

    2011-04-01

    The effects of paper mill sludge, red mud and zinc fertilizer addition on remediation of acid cadmium contaminated paddy soil were studied in a pot experiment, and their beneficial effects were verified in a field experiment, by using lime as comparison. The pot experiment results showed that a single application (2 g x kg(-1)) of lime, paper mill sludge or red mud increased soil pH significantly. Compared with no applying alkaline substances, the soil exchangeable Ca content was increased by 33.1%-76.0% at 7 days after applying alkaline substances and 31.0%-78.3% at 30 days after rice transplanting, respectively. The soil available Cd content was significantly decreased by 38.4%-45.0% at 7 days after the three alkaline substances applications, and was decreased by 37.4%-52.9% and 33.2%-38.7% at 30 days and 60 days after rice transplanting, respectively. The Cd content in rice root and brown rice was decreased by 24.0%-48.5% and 26.3%-44.7%, respectively. With equal applications of lime, paper mill sludge and red mud, the effects on increase of soil pH and decrease in Cd accumulation by rice was lime > red mud > paper mill sludge. Compared with a single application (2 g x kg(-1)) of paper mill sludge or red mud, Cd accumulation decreased significantly following the application of zinc fertilizer (0.2 g x kg(-1)) field experimental results were similar to the pot experiment that Cd accumulation apparently declined in the first and second crops (late rice and autumn rape) following the application of paper mill sludge, red mud and addition of zinc fertilizer. The Cd content in brown rice and rape seeds was decreased by 27.1-65.1% and 16.4%-41.6%, respectively, compared with no alkaline substances application. The Cd content in brown rice reached the National Hygienic Standard for Grains (GB 2715-2005). Therefore, combined application of paper mill sludge or red mud with zinc fertilizer was a feasible method to remediate acid cadmium contaminated paddy soil. Rice

  7. Modelling field-data of preferential flow in paddy soil induced by earthworm burrows.

    PubMed

    Sander, Till; Gerke, Horst H

    2009-02-16

    Dye tracer studies revealed that earthworm burrows in the compacted plough pan of a Chinese paddy rice field can serve as preferential flow paths. It is, however, unclear whether the observed bypass of the compacted soil horizon might be explained by differences in hydraulic properties between the plough pan, the worm burrows with a surrounding denser drilosphere and the un-compacted subsoil, or by lower-permeable macropore walls. The objective is to separately analyse effects of the individual flow domains and to identify possible limiting factors (bottlenecks) in the flow system for better soil drainage management. Hydraulic properties are inversely estimated from in situ measurements of pressure heads and evaporation by using HYDRUS_1D code. Field data of 2D pressure head progression after dye tracer infiltration in the vicinity of worm burrows are simulated using HYDRUS_2D. The axisymmetric 2D flow model considers a highly permeable cylindrical macropore region in the centre of the flow domain, assuming Darcy's law is valid. The match between simulated and measured pressure head fields improved after including a lower-permeable drilosphere pore domain. Scenario simulations show that the inflow into the 'bypass-flow' domain are reduced by the homogenized topsoil (i.e., after puddling) and limited if the macropore domain is relatively shallow. The results suggest that basic structural features may in this concept be considered as one possibility to describe observed preferential flow patterns. The separate consideration of soil structural effects may help developing and improving management strategies for manipulation of preferential flow in soils of paddy fields. PMID:19064301

  8. Potential effects of earthworm activity on C and N dynamics in tropical paddy soil

    NASA Astrophysics Data System (ADS)

    John, Katharina; Zaitsev, Andrey S.; Wolters, Volkmar

    2016-04-01

    Earthworms are involved in key ecosystem processes and are generally considered important for sustainable crop production. However, their provision of essential ecosystem services and contribution to tropical soil carbon and nitrogen balance in rice-based agroecosystems are not yet completely understood. We carried out two microcosm experiments to quantify the impact of a tropical earthworm Pheretima sp. from the Philippines on C and N turnover in rice paddy soils. First one was conducted to understand the modulation impact of soil water saturation level and nitrogen fertilizer input intensity on C and N cycles. The second one focused on the importance of additional organic matter (rice straw) amendment on the earthworm modulation of mineralization in non-flooded conditions. We measured CO2, CH4 (Experiments 1 and 2) and N2O evolution (Experiment 2) from rice paddy soil collected at the fields of the International Rice Research Institute (Philippines). Further we analysed changes in soil C and N content as well as nutrient loss via leaching induced by earthworms (Experiment 2). Addition of earthworms resulted in the strong increase of CH4 release under flooded conditions as well as after rice straw amendment. Compared to flooded conditions, earthworms suppressed the distinct CO2 respiration maximum at intermediate soil water saturation levels. In the first few days after the experiment establishment (Experiment 1) intensive nitrogen application resulted in the suppression of CO2 emission by earthworms at non-flooded soil conditions. However, at the longer term perspective addressed in the second experiment (30 days) earthworm activity rather increased average soil respiration under intensive fertilization or rice straw amendment. The lowest N2O release rates were revealed in the microcosms with earthworm and straw treatments. The combined effect of N fertilizer and straw addition to microcosms resulted in the increased leachate volume due to earthworm bioturbation

  9. Arsenic in rice (Oryza sativa L.) related to dynamics of arsenic and silicic acid in paddy soils.

    PubMed

    Bogdan, Katja; Schenk, Manfred K

    2008-11-01

    Paddy rice is a global staple food which in some circumstances can contain high levels of the toxic element arsenic (As). In order to elucidate factors influencing As dissolution in the soil solution during paddy rice cultivation, rice (Oryza sativa L. "Selenio") was cultivated to maturity in six paddy soils in the greenhouse in 2005 and 2006. Concentrations of Mn, Fe, As, P, and silicic acid in soil solution and As concentrations in rice straw and polished rice grain were determined. There was a close relationship between Fe and As concentrations in the soil solution, suggesting that the major part of dissolved As originated from reduced iron-(hydr)oxide. However, in addition to the factors causing As dissolution in the soil, other factors influenced the uptake of As by rice. The inhibitory effect of indigenous silicic acid in the soil solution on As uptake was clearly shown. This implied that soils with high plant available Si contents resulted in low plant As contents and that Si application to soils may decrease the As content of rice. PMID:19031876

  10. Mapping spatial variability of soil salinity in a coastal paddy field based on electromagnetic sensors.

    PubMed

    Guo, Yan; Huang, Jingyi; Shi, Zhou; Li, Hongyi

    2015-01-01

    In coastal China, there is an urgent need to increase land area for agricultural production and urban development, where there is a rapid growing population. One solution is land reclamation from coastal tidelands, but soil salinization is problematic. As such, it is very important to characterize and map the within-field variability of soil salinity in space and time. Conventional methods are often time-consuming, expensive, labor-intensive, and unpractical. Fortunately, proximal sensing has become an important technology in characterizing within-field spatial variability. In this study, we employed the EM38 to study spatial variability of soil salinity in a coastal paddy field. Significant correlation relationship between ECa and EC1:5 (i.e. r >0.9) allowed us to use EM38 data to characterize the spatial variability of soil salinity. Geostatistical methods were used to determine the horizontal spatio-temporal variability of soil salinity over three consecutive years. The study found that the distribution of salinity was heterogeneous and the leaching of salts was more significant in the edges of the study field. By inverting the EM38 data using a Quasi-3D inversion algorithm, the vertical spatio-temporal variability of soil salinity was determined and the leaching of salts over time was easily identified. The methodology of this study can be used as guidance for researchers interested in understanding soil salinity development as well as land managers aiming for effective soil salinity monitoring and management practices. In order to better characterize the variations in soil salinity to a deeper soil profile, the deeper mode of EM38 (i.e., EM38v) as well as other EMI instruments (e.g. DUALEM-421) can be incorporated to conduct Quasi-3D inversions for deeper soil profiles. PMID:26020969

  11. Mapping Spatial Variability of Soil Salinity in a Coastal Paddy Field Based on Electromagnetic Sensors

    PubMed Central

    Guo, Yan; Huang, Jingyi; Shi, Zhou; Li, Hongyi

    2015-01-01

    In coastal China, there is an urgent need to increase land area for agricultural production and urban development, where there is a rapid growing population. One solution is land reclamation from coastal tidelands, but soil salinization is problematic. As such, it is very important to characterize and map the within-field variability of soil salinity in space and time. Conventional methods are often time-consuming, expensive, labor-intensive, and unpractical. Fortunately, proximal sensing has become an important technology in characterizing within-field spatial variability. In this study, we employed the EM38 to study spatial variability of soil salinity in a coastal paddy field. Significant correlation relationship between ECa and EC1:5 (i.e. r >0.9) allowed us to use EM38 data to characterize the spatial variability of soil salinity. Geostatistical methods were used to determine the horizontal spatio-temporal variability of soil salinity over three consecutive years. The study found that the distribution of salinity was heterogeneous and the leaching of salts was more significant in the edges of the study field. By inverting the EM38 data using a Quasi-3D inversion algorithm, the vertical spatio-temporal variability of soil salinity was determined and the leaching of salts over time was easily identified. The methodology of this study can be used as guidance for researchers interested in understanding soil salinity development as well as land managers aiming for effective soil salinity monitoring and management practices. In order to better characterize the variations in soil salinity to a deeper soil profile, the deeper mode of EM38 (i.e., EM38v) as well as other EMI instruments (e.g. DUALEM-421) can be incorporated to conduct Quasi-3D inversions for deeper soil profiles. PMID:26020969

  12. [Effects of soil factors on vegetation community structure in an abandoned subtropical paddy wetland].

    PubMed

    Peng, Yi; Li, Yu-Yuan; Li, Zhong-Wu; Ye, Fang-Yi; Pan, Chun-Xiang; Xie, Xiao-Li

    2009-07-01

    Based on the investigation data from a subtropical wetland having been abandoned from paddy agriculture for one year, a redundancy analysis was conducted on the relationships between vegetation community and soil factors in the wetland. It was found that soil moisture regime, available K and P, and pH were the main factors affecting the distribution of plant species. The common plant species could be classified into three groups, i. e., Ludwigia prostrata - Murdannia triquetra group (G1), Hemarthria altissima - Rotala rotundifolia - Lapsana apogonoides group (G2), and Conyza canadensis - Polygonum hydropiper - Paspalum pasaloides group (G3). G1 mainly distributed on the soils with higher available K, G2 mainly distributed in periodically flooded area, while G3 mainly distributed in drainage area and was positively correlated to soil available P and pH. Species diversity and above-ground biomass had significant positive correlations with soil pH and total K, respectively, while evenness index was significantly negatively correlated with soil available N. No significant correlations were observed among other indices. PMID:19899449

  13. Characteristics of boron accumulation by fly ash application in paddy soil.

    PubMed

    Lee, Seul Bi; Lee, Yong Bok; Lee, Chang Hoon; Hong, Chang Oh; Kim, Pil Joo; Yu, Chan

    2008-09-01

    Fly ash has a high content of plant available silicate which is strongly needed for rice cultivation in Korea. One concern for plants grown on soils amended with fly ash is boron (B) toxicity because most of the fresh fly ash contains considerable B. This study was conducted in paddy soil to determine B uptake by rice and characteristics of B accumulation in soil after fly ash application (0, 40, 80, and 120 Mg fly ash ha(-1)). In all fly ash treatments, B content in rice leaves and available B in soil at all growing stage were higher than those of control, but were not exceeded a toxicity levels. Boron occluded in amorphous Fe and Al oxides comprised ca. 20-39% of total B and was not affected by fly ash application. Most of the B was accumulated by fly ash application as a residual B which is plant-unavailable form, comprised >60% of the total B in soil. Thus, fly ash can be a good soil amendment for rice production without B toxicity. PMID:18194862

  14. Effect of Different Fertilizer Application on the Soil Fertility of Paddy Soils in Red Soil Region of Southern China

    PubMed Central

    Dong, Wenyi; Zhang, Xinyu; Wang, Huimin; Dai, Xiaoqin; Sun, Xiaomin; Qiu, Weiwen; Yang, Fengting

    2012-01-01

    Appropriate fertilizer application is an important management practice to improve soil fertility and quality in the red soil regions of China. In the present study, we examined the effects of five fertilization treatments [these were: no fertilizer (CK), rice straw return (SR), chemical fertilizer (NPK), organic manure (OM) and green manure (GM)] on soil pH, soil organic carbon (SOC), total nitrogen (TN), C/N ratio and available nutrients (AN, AP and AK) contents in the plowed layer (0–20 cm) of paddy soil from 1998 to 2009 in Jiangxi Province, southern China. Results showed that the soil pH was the lowest with an average of 5.33 units in CK and was significantly higher in NPK (5.89 units) and OM (5.63 units) treatments (P<0.05). The application of fertilizers have remarkably improved SOC and TN values compared with the CK, Specifically, the OM treatment resulted in the highest SOC and TN concentrations (72.5% and 51.2% higher than CK) and NPK treatment increased the SOC and TN contents by 22.0% and 17.8% compared with CK. The average amounts of C/N ratio ranged from 9.66 to 10.98 in different treatments, and reached the highest in OM treatment (P<0.05). During the experimental period, the average AN and AP contents were highest in OM treatment (about 1.6 and 29.6 times of that in the CK, respectively) and second highest in NPK treatment (about 1.2 and 20.3 times of that in the CK). Unlike AN and AP, the highest value of AK content was observed in NPK treatments with 38.10 mg·kg−1. Thus, these indicated that organic manure should be recommended to improve soil fertility in this region and K fertilizer should be simultaneously applied considering the soil K contents. Considering the long-term fertilizer efficiency, our results also suggest that annual straw returning application could improve soil fertility in this trial region. PMID:23028550

  15. Plant available silicon in South-east Asian rice paddy soils - relevance of agricultural practice and of abiotic factors

    NASA Astrophysics Data System (ADS)

    Marxen, A.; Klotzbücher, T.; Vetterlein, D.; Jahn, R.

    2012-12-01

    Background Silicon (Si) plays a crucial role in rice production. Si content of rice plants exceeds the content of other major nutrients such as nitrogen, phosphorous or potassium. Recent studies showed that in some environments external supply of Si can enhance the growth of rice plants. Rice plants express specific Si transporters to absorb Si from soil solutions in form of silicic acid, which precipitates in tissue cells forming amorphous silica bodies, called phytoliths. The phytoliths are returned to soils with plant residues. They might be a main source of plant available silicic acid in soils. Aims In this study we assess the effects of rice paddy cultivation on the stocks of `reactive` Si fractions in mineral topsoils of rice paddy fields in contrasting landscapes. The `reactive` Si fractions are presumed to determine the release of plant-available silicic acid in soils. We consider the relevance of abiotic factors (mineral assemblage; soil weathering status) and agricultural practice for these fractions. Agricultural practices, which were assumed to affect the stocks of `reactive` Si were (i) the usage of different rice varieties (which might differ in Si demand), (ii) straw residue management (i.e., whether straw residues are returned to the fields or removed and used e.g. as fodder), and (iii) yield level and number of crops per year. Material and methods Soils (top horizon of about 0-20 cm depth) were sampled from rice paddy fields in 2 mountainous and 5 lowland landscapes of contrasting geologic conditions in Vietnam and the Philippines. Ten paddy fields were sampled per landscape. The rice paddy management within landscapes differed when different farmers and/or communities managed the fields. We analysed the following fractions of `reactive` Si in the soils: acetate-extractable Si (dissolved and easily exchangeable Si), phosphate-extractable Si (adsorbed Si), oxalate extractable Si (Si associated with poorly-ordered sesquioxides), NaOH extractable Si

  16. Microbial utilization of rice straw and its derived biochar in a paddy soil.

    PubMed

    Pan, Fuxia; Li, Yaying; Chapman, Stephen James; Khan, Sardar; Yao, Huaiying

    2016-07-15

    The application of straw and biochar to soil has received great attention because of their potential benefits such as fertility improvement and carbon (C) sequestration. The abiotic effects of these materials on C and nitrogen (N) cycling in the soil ecosystem have been previously investigated, however, the effects of straw or its derived biochar on the soil microbial community structure and function are not well understood. For this purpose, a short-term incubation experiment was conducted using (13)C-labeled rice straw and its derived biochar ((13)C-labeled biochar) to deepen our understanding about soil microbial community dynamics and function in C sequestration and greenhouse gas emission in the acidic paddy soil amended with these materials. Regarding microbial function, biochar and straw applications increased CO2 emission in the initial stage of incubation and reached the highest level (0.52 and 3.96mgCkg(-1)soilh(-1)) at 1d and 3d after incubation, respectively. Straw amendment significantly (p<0.01) increased respiration rate, total phospholipid fatty acids (PLFAs) and (13)C-PLFA as compared to biochar amendment and the control. The amount and percent of Gram positive bacteria, fungi and actinomycetes were also significantly (p<0.05) higher in (13)C-labeled straw amended soil than the (13)C-labeled biochar amended soil. According to the (13)C data, 23 different PLFAs were derived from straw amended paddy soil, while only 17 PLFAs were derived from biochar amendments. The profile of (13)C-PLFAs derived from straw amendment was significantly (p<0.01) different from biochar amendment. The PLFAs18:1ω7c and cy17:0 (indicators of Gram negative bacteria) showed high relative abundances in the biochar amendment, while 10Me18:0, i17:0 and 18:2ω6,9c (indicators of actinomycetes, Gram positive bacteria and fungi, respectively) showed high relative abundance in the straw amendments. Our results suggest that the function, size and structure of the microbial

  17. Effects of changing redox conditions on the dynamics of dissolved organic matter and CO2 in paddy soils

    NASA Astrophysics Data System (ADS)

    Hanke, Alexander; Cao, Zhi Hong; Liu, Qin; Muhr, Jan; Kalbitz, Karsten

    2010-05-01

    The current knowledge about dissolved organic matter (DOM) dynamics in soils and its dependence on different C pools based mainly on observations and experiments in aerobic environments. We have only a limited understanding about the effects of changing redox conditions on production and composition of DOM although this fraction of soil organic matter is important for greenhouse gas emission and carbon storage in soils. In many ecosystems temporal and spatial changes of oxic and anoxic conditions are evident and might even increase in future. It is assumed that changing redox conditions are the key drivers of DOM dynamics in such ecosystems. More detailed we tested the following hypotheses: Anoxic conditions result in relative DOM accumulation due to less mineralization of already produced DOM Close relationship between DOM production and CO2 emission 14C signature of CO2 enables the identification of different C pools degraded at oxic and anoxic conditions We chose paddy soils as a model ecosystem because these soils are anoxic during the rice growing period and oxic during harvest and growth of other crops. Furthermore, paddy soils have oxic and anoxic horizons. Soils of a unique chronosequence of paddy soil evolution (50 to 2000 years, China) were studied in direct comparison to non-paddy soils of the same age. In these soils, exposed to different redox conditions over defined periods of times, the dynamics of DOM, CO2, 14C of the CO2 and other redox sensitive elements were followed in laboratory experiments. In the latter redox conditions were changed every 3 weeks from oxic to anoxic and vice versa. Besides analysis of the composition of the soil solution and the gas phase we determined differences in C pools being respired at oxic and anoxic conditions by 14C AMS of the CO2. The measured redox potentials of -50 mV to 250mV at anoxic conditions and 350 mV to 550 mV at oxic conditions were in the expected range and proofed the appropriate setting of the chosen

  18. On the apparent CO2 absorption by alkaline soils

    NASA Astrophysics Data System (ADS)

    Chen, X.; Wang, W. F.

    2014-02-01

    Alkaline soils in the Gubantonggut Desert were recently demonstrated socking away large quantities of CO2 in an abiotic form. This demands a better understanding of abiotic CO2 exchange in alkaline sites. Reaction of CO2 with the moisture or dew in the soil was conjectured as a potential mechanism. The main goal of this study is to determine the extent to which the dew deposition modulates Land-Atmosphere CO2 exchange at highly alkaline sites (pH ~ 10). Experiments were conducted at the most barren sites (canopy coverage < 5%) to cut down uncertainty. Dew quantities and soil CO2 fluxes were measured using a micro-lysimeters and an automated flux system (LI-COR, Lincoln, Nebraska, USA), respectively. There is an evident increase of dew deposition in nocturnal colder temperatures and decrease in diurnal warmer temperatures. Variations of soil CO2 flux are almost contrary, but the increase in diurnal warmer temperatures is obscure. It was shown that the accumulation and evaporation of dew in the soil motivates the apparent absorption and release of CO2. It was demonstrated that dew amounts in the soil has an exponential relation with the part in Fc beyond explanations of the worldwide utilized Q10 model. Therefore dew deposition in highly alkaline soils exerted a potential CO2 sink and can partly explain the apparent CO2 absorption. This implied a crucial component in the net ecosystem carbon balance (NECB) at alkaline sites which occupies approximately 5% of the Earth's land surface (7 million km). Further explorations for its mechanisms and representativeness over other arid climate systems have comprehensive perspectives in the quaternary research.

  19. Phyllosphere Bacterial Community of Floating Macrophytes in Paddy Soil Environments as Revealed by Illumina High-Throughput Sequencing

    PubMed Central

    Xie, Wan-Ying

    2014-01-01

    The phyllosphere of floating macrophytes in paddy soil ecosystems, a unique habitat, may support large microbial communities but remains largely unknown. We took Wolffia australiana as a representative floating plant and investigated its phyllosphere bacterial community and the underlying driving forces of community modulation in paddy soil ecosystems using Illumina HiSeq 2000 platform-based 16S rRNA gene sequence analysis. The results showed that the phyllosphere of W. australiana harbored considerably rich communities of bacteria, with Proteobacteria and Bacteroidetes as the predominant phyla. The core microbiome in the phyllosphere contained genera such as Acidovorax, Asticcacaulis, Methylibium, and Methylophilus. Complexity of the phyllosphere bacterial communities in terms of class number and α-diversity was reduced compared to those in corresponding water and soil. Furthermore, the bacterial communities exhibited structures significantly different from those in water and soil. These findings and the following redundancy analysis (RDA) suggest that species sorting played an important role in the recruitment of bacterial species in the phyllosphere. The compositional structures of the phyllosphere bacterial communities were modulated predominantly by water physicochemical properties, while the initial soil bacterial communities had limited impact. Taken together, the findings from this study reveal the diversity and uniqueness of the phyllosphere bacterial communities associated with the floating macrophytes in paddy soil environments. PMID:25362067

  20. Effects of biochar addition on the sorption of polar herbicides in paddy soils

    NASA Astrophysics Data System (ADS)

    Garcia-Jaramillo, Manuel; Cox, Lucía; Hermosín, Mari Carmen; Helmus, Rick; Parsons, John R.; Kalbitz, Karsten

    2016-04-01

    Organic amendments, and their water soluble fraction, induce an important impact on pesticide dissipation in soils, affecting their adsorption and transport processes through various chemical interactions. Although in most cases addition of organic amendments increases sorption, leaching of the pesticides can be either reduced or promoted. Because of that, their effect on pesticide behavior must be assessed in order to optimize their use. The major objectives of this study were to investigate the impact of biochar and biochar water extractable substances (BWES) on the sorption behavior of two polar herbicides, azimsulfuron and penoxsulam, in two amended and unamended paddy soils under flooded conditions. The adsorption - desorption of these herbicides was studied in soils amended with fresh biochar and in soils amended with a washed version of the biochar, simulating the conditions of a soil recently amended and a soil where biochar was applied longer time before and most part of the BWES has been already removed because of the flooded conditions. Therefore, sorption on biochar was assessed before and after removing 80% of its water extractable substances, separately and in combination with each soil (at 2 and 5% w/w). BWES were analyzed by high resolution mass spectrometry. The most abundant fractions present in the high mass range were nitrogen-containing molecules. The aromatic character of the DOC-extracts of the unamended and amended soils, based on the specific UV absorbance at 280 nm (SUVA280), was increased with the amendment in all the conditions tested. Adsorption data of both herbicides fitted very well to the Freundlich equation, with R2 values higher than 0.9 in all the conditions tested. Sorption isotherms were in all cases nonlinear, with Nf values <1, resembling L-type isotherms. Biochar had a very different effect on the sorptive properties of each soil. The highest sorption affinity of azimsulfuron to amended soils was observed for the soils

  1. Bacterial colonization of a fumigated alkaline saline soil.

    PubMed

    Bello-López, Juan M; Domínguez-Mendoza, Cristina A; de León-Lorenzana, Arit S; Delgado-Balbuena, Laura; Navarro-Noya, Yendi E; Gómez-Acata, Selene; Rodríguez-Valentín, Analine; Ruíz-Valdiviezo, Victor M; Luna-Guido, Marco; Verhulst, Nele; Govaerts, Bram; Dendooven, Luc

    2014-07-01

    After chloroform fumigating an arable soil, the relative abundance of phylotypes belonging to only two phyla (Actinobacteria and Firmicutes) and two orders [Actinomycetales and Bacillales (mostly Bacillus)] increased in a subsequent aerobic incubation, while it decreased for a wide range of bacterial groups. It remained to be seen if similar bacterial groups were affected when an extreme alkaline saline soil was fumigated. Soil with electrolytic conductivity between 139 and 157 dS m(-1), and pH 10.0 and 10.3 was fumigated and the bacterial community structure determined after 0, 1, 5 and 10 days by analysis of the 16S rRNA gene, while an unfumigated soil served as control. The relative abundance of the Firmicutes increased in the fumigated soil (52.8%) compared to the unfumigated soil (34.2%), while that of the Bacteroidetes decreased from 16.2% in the unfumigated soil to 8.8% in the fumigated soil. Fumigation increased the relative abundance of the genus Bacillus from 14.7% in the unfumigated soil to 25.7%. It was found that phylotypes belonging to the Firmicutes, mostly of the genus Bacillus, were dominant in colonizing the fumigated alkaline saline as found in the arable soil, while the relative abundance of a wide range of bacterial groups decreased. PMID:24846742

  2. [Long-term effects of tillage methods on heavy metal accumulation and availability in purple paddy soil].

    PubMed

    Chang, Tong-Ju; Cui, Xiao-Qiang; Ruan, Zhen; Zhao, Xiu-Lan

    2014-06-01

    A long-term experiment, conducted at Southwest University since 1990, was used to evaluate the effect of tillage methods on the total and available contents of heavy metals (Fe, Mn, Cu, Zn, Pb, Cd) in the profile of purple paddy soil and the contents of those metals in root, stem leaf and brown rice. The experiment included five tillage methods: conventional tillage, paddy-upland rotation, no-tillage and fallow in winter, ridge-no-tillage and compartments-no-tillage. The results showed that the total concentrations of Fe, Cu, Zn, Pb and Cd in the soil profile had no significant differences among five treatments, but it was found that total Mn has a significant decline in 0-20 cm under conventional tillage, paddy-upland rotation and no-tillage and fallow in winter compared with ridge-no-tillage and compartments-no-tillage. The availability of Fe, Cu, Zn, Pb and Cd decreased with the increase of soil depth in all treatments, but the availability of Mn was found to be the highest in the 20-40 cm layers except those in the paddy-upland rotation. In the ploughed layer, the contents of available Fe, Mn was the highest in paddy-upland rotation, while the contents of available Zn and Pb was the highest in conventional tillage, but tillage treatments had not significant influence to the contents of available Cu. Correlation analysis showed that available Fe was significantly negatively related to the pH values and significantly negatively related to the organic matter of soils, available Mn was significantly negatively related to the pH values and organic matter of soils, whereas the available Zn was significantly positively related to total Zn. The contents of Fe, Mn in rice root, the contents of Fe, Mn, Cu and Cd in rice straw and Cu in brown rice were higher under paddy-upland rotation, ridge-no-tillage and compartments-no-tillage than those in conventional tillage and no-tillage and fellow in winter. Paddy-upland rotation can significantly lower the migration

  3. Response of a Rice Paddy Soil Methanogen to Syntrophic Growth as Revealed by Transcriptional Analyses

    PubMed Central

    Liu, Pengfei; Yang, Yanxiang; Lü, Zhe

    2014-01-01

    Members of Methanocellales are widespread in paddy field soils and play the key role in methane production. These methanogens feature largely in these organisms' adaptation to low H2 and syntrophic growth with anaerobic fatty acid oxidizers. The adaptive mechanisms, however, remain unknown. In the present study, we determined the transcripts of 21 genes involved in the key steps of methanogenesis and acetate assimilation of Methanocella conradii HZ254, a strain recently isolated from paddy field soil. M. conradii was grown in monoculture and syntrophically with Pelotomaculum thermopropionicum (a propionate syntroph) or Syntrophothermus lipocalidus (a butyrate syntroph). Comparison of the relative transcript abundances showed that three hydrogenase-encoding genes and all methanogenesis-related genes tested were upregulated in cocultures relative to monoculture. The genes encoding formylmethanofuran dehydrogenase (Fwd), heterodisulfide reductase (Hdr), and the membrane-bound energy-converting hydrogenase (Ech) were the most upregulated among the evaluated genes. The expression of the formate dehydrogenase (Fdh)-encoding gene also was significantly upregulated. In contrast, an acetate assimilation gene was downregulated in cocultures. The genes coding for Fwd, Hdr, and the D subunit of F420-nonreducing hydrogenase (Mvh) form a large predicted transcription unit; therefore, the Mvh/Hdr/Fwd complex, capable of mediating the electron bifurcation and connecting the first and last steps of methanogenesis, was predicted to be formed in M. conradii. We propose that Methanocella methanogens cope with low H2 and syntrophic growth by (i) stabilizing the Mvh/Hdr/Fwd complex and (ii) activating formate-dependent methanogenesis. PMID:24837392

  4. Direct interspecies electron transfer accelerates syntrophic oxidation of butyrate in paddy soil enrichments.

    PubMed

    Li, Huijuan; Chang, Jiali; Liu, Pengfei; Fu, Li; Ding, Dewen; Lu, Yahai

    2015-05-01

    Syntrophic interaction occurs during anaerobic fermentation of organic substances forming methane as the final product. H2 and formate are known to serve as the electron carriers in this process. Recently, it has been shown that direct interspecies electron transfer (DIET) occurs for syntrophic CH4 production from ethanol and acetate. Here, we constructed paddy soil enrichments to determine the involvement of DIET in syntrophic butyrate oxidation and CH4 production. The results showed that CH4 production was significantly accelerated in the presence of nanoFe3 O4 in all continuous transfers. This acceleration increased with the increase of nanoFe3 O4 concentration but was dismissed when Fe3 O4 was coated with silica that insulated the mineral from electrical conduction. NanoFe3 O4 particles were found closely attached to the cell surfaces of different morphology, thus bridging cell connections. Molecular approaches, including DNA-based stable isotope probing, revealed that the bacterial Syntrophomonadaceae and Geobacteraceae, and the archaeal Methanosarcinaceae, Methanocellales and Methanobacteriales, were involved in the syntrophic butyrate oxidation and CH4 production. Among them, the growth of Geobacteraceae strictly relied on the presence of nanoFe3 O4 and its electrical conductivity in particular. Other organisms, except Methanobacteriales, were present in enrichments regardless of nanoFe3 O4 amendment. Collectively, our study demonstrated that the nanoFe3 O4 -facilitated DIET occurred in syntrophic CH4 production from butyrate, and Geobacter species played the key role in this process in the paddy soil enrichments. PMID:25059331

  5. Biochar amendment immobilizes lead in rice paddy soils and reduces its phytoavailability

    PubMed Central

    Li, Honghong; Liu, Yuting; Chen, Yanhui; Wang, Shanli; Wang, Mingkuang; Xie, Tuanhui; Wang, Guo

    2016-01-01

    This study aimed to determine effects of rice straw biochar on Pb sequestration in a soil-rice system. Pot experiments were conducted with rice plants in Pb-contaminated paddy soils that had been amended with 0, 2.5, and 5% (w/w) biochar. Compared to the control treatment, amendment with 5% biochar resulted in 54 and 94% decreases in the acid soluble and CaCl2-extractable Pb, respectively, in soils containing rice plants at the maturity stage. The amount of Fe-plaque on root surfaces and the Pb concentrations of the Fe-plaque were also reduced in biochar amended soils. Furthermore, lead species in rice roots were determined using Pb L3-edge X-ray absorption near edge structure (XANES), and although Pb-ferrihydrite complexes dominated Pb inventories, increasing amounts of organic complexes like Pb-pectins and Pb-cysteine were found in roots from the 5% biochar treatments. Such organic complexes might impede Pb translocation from root to shoot and subsequently reduce Pb accumulation in rice with biochar amendment. PMID:27530495

  6. Bulliform Phytolith Research in Wild and Domesticated Rice Paddy Soil in South China

    PubMed Central

    Huan, Xiujia; Lu, Houyuan; Wang, Can; Tang, Xiangan; Zuo, Xinxin; Ge, Yong; He, Keyang

    2015-01-01

    Bulliform phytoliths play an important role in researching rice origins as they can be used to distinguish between wild and domesticated rice. Rice bulliform phytoliths are characterized by numerous small shallow fish-scale decorations on the lateral side. Previous studies have shown that domesticated rice has a larger number of these decorations than wild rice and that the number of decorations ≥9 is a useful feature for identifying domesticated rice. However, this standard was established based on limited samples of modern rice plants. In this study, we analyzed soil samples from both wild and domesticated rice paddies. Results showed that, in wild rice soil samples, the proportion of bulliform phytoliths with ≥9 decorations was 17.46% ± 8.29%, while in domesticated rice soil samples, the corresponding proportion was 63.70% ± 9.22%. This suggests that the proportion of phytoliths with ≥9 decorations can be adopted as a criterion for discriminating between wild and domesticated rice in prehistoric soil. This indicator will be of significance in improving the application of fish-scale decorations to research into rice origins and the rice domestication process. PMID:26488583

  7. Biochar amendment immobilizes lead in rice paddy soils and reduces its phytoavailability.

    PubMed

    Li, Honghong; Liu, Yuting; Chen, Yanhui; Wang, Shanli; Wang, Mingkuang; Xie, Tuanhui; Wang, Guo

    2016-01-01

    This study aimed to determine effects of rice straw biochar on Pb sequestration in a soil-rice system. Pot experiments were conducted with rice plants in Pb-contaminated paddy soils that had been amended with 0, 2.5, and 5% (w/w) biochar. Compared to the control treatment, amendment with 5% biochar resulted in 54 and 94% decreases in the acid soluble and CaCl2-extractable Pb, respectively, in soils containing rice plants at the maturity stage. The amount of Fe-plaque on root surfaces and the Pb concentrations of the Fe-plaque were also reduced in biochar amended soils. Furthermore, lead species in rice roots were determined using Pb L3-edge X-ray absorption near edge structure (XANES), and although Pb-ferrihydrite complexes dominated Pb inventories, increasing amounts of organic complexes like Pb-pectins and Pb-cysteine were found in roots from the 5% biochar treatments. Such organic complexes might impede Pb translocation from root to shoot and subsequently reduce Pb accumulation in rice with biochar amendment. PMID:27530495

  8. Anaerobic 2-propanol degradation in anoxic paddy soil and the possible role of methanogens in its degradation.

    PubMed

    Tonouchi, Akio

    2004-08-01

    The anaerobic degradation of 2-propanol in anoxic paddy soil was studied with soil cultures and a 2-propanol-utilizing methanogen. Acetone was the first and the major intermediate involved in the methanogenic degradation of 2-propanol. Analyses with a methanogenesis inhibitor, bacteria antibiotics, and the addition of H2 to the gas phase revealed that 2-propanol oxidation to acetone directly occurred using 2-propanol-utilizing methanogens, but not with H2-producing syntrophic bacteria, for which the removal of acetone is required for complete 2-propanol oxidation. The 2-propanol-utilizing strain IIE1, which is phylogenetically closely related to Methanoculleus palmolei, was isolated from paddy soil, and the potential role of the strain in 2-propanol degradation was investigated. 2-Propanol is one of the representative fermentation intermediates in anaerobic environments. This is the first report on the anaerobic 2-propanol degradation process. PMID:15297909

  9. Aging effect on the leaching behavior of heavy metals (Cu, Zn, and Cd) in red paddy soil.

    PubMed

    Huang, Bin; Li, Zhongwu; Huang, Jinquan; Chen, Guiqiu; Nie, Xiaodong; Ma, Wenming; Yao, Hongbo; Zhen, Jiamei; Zeng, Guangming

    2015-08-01

    Aging effect can influence the fractions distribution and mobility of metals after they are added into soil. In this study, incubation and soil column experiments under simulated acid rain condition were conducted to evaluate aging effect on the leaching characteristic of Cu, Zn, and Cd in artificial polluted red paddy soil. Our results showed that aging effect reduced metal contents in exchangeable and HoAc soluble fractions. Power function was the most excellent to describe the variation of exchangeable fraction, while pseudo first- and second-order functions were more successful to describe the leaching characteristic of metals from soil columns. The leaching amount of the metals from the polluted soil only accounted for a small part of their total content in soil, and the leachability of Cu was the weakest. Both the exchangeable and HoAc soluble fraction were available as indicators to evaluate the leachability of metals in red paddy soil. The shorter time the soil was contaminated, the more amounts of metals released from the soil. The reduction of exchangeable fraction caused by aging effect was the main reason for the decrease of metal mobility in soil. PMID:25821039

  10. Conventional methanotrophs are responsible for atmospheric methane oxidation in paddy soils

    PubMed Central

    Cai, Yuanfeng; Zheng, Yan; Bodelier, Paul L. E.; Conrad, Ralf; Jia, Zhongjun

    2016-01-01

    Soils serve as the biological sink of the potent greenhouse gas methane with exceptionally low concentrations of ∼1.84 p.p.m.v. in the atmosphere. The as-yet-uncultivated methane-consuming bacteria have long been proposed to be responsible for this ‘high-affinity' methane oxidation (HAMO). Here we show an emerging HAMO activity arising from conventional methanotrophs in paddy soil. HAMO activity was quickly induced during the low-affinity oxidation of high-concentration methane. Activity was lost gradually over 2 weeks, but could be repeatedly regained by flush-feeding the soil with elevated methane. The induction of HAMO activity occurred only after the rapid growth of methanotrophic populations, and a metatranscriptome-wide association study suggests that the concurrent high- and low-affinity methane oxidation was catalysed by known methanotrophs rather than by the proposed novel atmospheric methane oxidizers. These results provide evidence of atmospheric methane uptake in periodically drained ecosystems that are typically considered to be a source of atmospheric methane. PMID:27248847

  11. Evaluation of soil characteristics potentially affecting arsenic concentration in paddy rice (Oryza sativa L.).

    PubMed

    Bogdan, Katja; Schenk, Manfred K

    2009-10-01

    Paddy rice may contribute considerably to the human intake of As. The knowledge of soil characteristics affecting the As content of the rice plant enables the development of agricultural measures for controlling As uptake. During field surveys in 2004 and 2006, plant samples from 68 fields (Italy, Po-area) revealed markedly differing As concentration in polished rice. The soil factors total As(aqua regia), pH, grain size fractions, total C, plant available P(CAL), poorly crystalline Fe(oxal.) and plant available Si(Na-acetate) content that potentially affect As content of rice were determined. A multiple linear regression analysis showed a significant positive influence of the total As(aqua regia) and plant available P(CAL) content and a negative influence of the poorly crystalline Fe(oxal.) content of the soil on the As content in polished rice and rice straw. Si concentration in rice straw varied widely and was negatively related to As content in straw and polished rice. PMID:19482396

  12. Conventional methanotrophs are responsible for atmospheric methane oxidation in paddy soils

    NASA Astrophysics Data System (ADS)

    Cai, Yuanfeng; Zheng, Yan; Bodelier, Paul L. E.; Conrad, Ralf; Jia, Zhongjun

    2016-06-01

    Soils serve as the biological sink of the potent greenhouse gas methane with exceptionally low concentrations of ~1.84 p.p.m.v. in the atmosphere. The as-yet-uncultivated methane-consuming bacteria have long been proposed to be responsible for this `high-affinity' methane oxidation (HAMO). Here we show an emerging HAMO activity arising from conventional methanotrophs in paddy soil. HAMO activity was quickly induced during the low-affinity oxidation of high-concentration methane. Activity was lost gradually over 2 weeks, but could be repeatedly regained by flush-feeding the soil with elevated methane. The induction of HAMO activity occurred only after the rapid growth of methanotrophic populations, and a metatranscriptome-wide association study suggests that the concurrent high- and low-affinity methane oxidation was catalysed by known methanotrophs rather than by the proposed novel atmospheric methane oxidizers. These results provide evidence of atmospheric methane uptake in periodically drained ecosystems that are typically considered to be a source of atmospheric methane.

  13. Conventional methanotrophs are responsible for atmospheric methane oxidation in paddy soils.

    PubMed

    Cai, Yuanfeng; Zheng, Yan; Bodelier, Paul L E; Conrad, Ralf; Jia, Zhongjun

    2016-01-01

    Soils serve as the biological sink of the potent greenhouse gas methane with exceptionally low concentrations of ∼1.84 p.p.m.v. in the atmosphere. The as-yet-uncultivated methane-consuming bacteria have long been proposed to be responsible for this 'high-affinity' methane oxidation (HAMO). Here we show an emerging HAMO activity arising from conventional methanotrophs in paddy soil. HAMO activity was quickly induced during the low-affinity oxidation of high-concentration methane. Activity was lost gradually over 2 weeks, but could be repeatedly regained by flush-feeding the soil with elevated methane. The induction of HAMO activity occurred only after the rapid growth of methanotrophic populations, and a metatranscriptome-wide association study suggests that the concurrent high- and low-affinity methane oxidation was catalysed by known methanotrophs rather than by the proposed novel atmospheric methane oxidizers. These results provide evidence of atmospheric methane uptake in periodically drained ecosystems that are typically considered to be a source of atmospheric methane. PMID:27248847

  14. phoD Alkaline Phosphatase Gene Diversity in Soil

    PubMed Central

    Kertesz, Michael A.; Bünemann, Else K.

    2015-01-01

    Phosphatase enzymes are responsible for much of the recycling of organic phosphorus in soils. The PhoD alkaline phosphatase takes part in this process by hydrolyzing a range of organic phosphoesters. We analyzed the taxonomic and environmental distribution of phoD genes using whole-genome and metagenome databases. phoD alkaline phosphatase was found to be spread across 20 bacterial phyla and was ubiquitous in the environment, with the greatest abundance in soil. To study the great diversity of phoD, we developed a new set of primers which targets phoD genes in soil. The primer set was validated by 454 sequencing of six soils collected from two continents with different climates and soil properties and was compared to previously published primers. Up to 685 different phoD operational taxonomic units were found in each soil, which was 7 times higher than with previously published primers. The new primers amplified sequences belonging to 13 phyla, including 71 families. The most prevalent phoD genes identified in these soils were affiliated with the orders Actinomycetales (13 to 35%), Bacillales (1 to 29%), Gloeobacterales (1 to 18%), Rhizobiales (18 to 27%), and Pseudomonadales (0 to 22%). The primers also amplified phoD genes from additional orders, including Burkholderiales, Caulobacterales, Deinococcales, Planctomycetales, and Xanthomonadales, which represented the major differences in phoD composition between samples, highlighting the singularity of each community. Additionally, the phoD bacterial community structure was strongly related to soil pH, which varied between 4.2 and 6.8. These primers reveal the diversity of phoD in soil and represent a valuable tool for the study of phoD alkaline phosphatase in environmental samples. PMID:26253682

  15. Increase of As release and phytotoxicity to rice seedlings in As-contaminated paddy soils by Si fertilizer application.

    PubMed

    Lee, Chia-Hsing; Huang, Hsuan-Han; Syu, Chien-Hui; Lin, Tzu-Huei; Lee, Dar-Yuan

    2014-07-15

    Silicon (Si) was shown to be able to reduce arsenic (As) uptake by rice in hydroponic culture or in low As soils using high Si application rates. However, the effect of Si application on As uptake of rice grown in As-contaminated soils using Si fertilizer recommendation rate has not been investigated. In this study, the effect of Si application using Si fertilizer recommendation rate on As release and phytotoxicity in soils with different properties and contents of As was examined. The results show that the concentrations of As in soil solutions increased after Si applications due to competitive adsorption between As and Si on soil solids and the Si concentrations in soil solutions were also elevated to beneficial levels for rice growth. The rice seedlings accumulated more As and its growth was inhibited by Si application in As contaminated/spiked soils. The results indicate that there is an initial aggravation in As toxicity before the beneficial effects of Si fertilizing to rice were revealed when Si application based on fertilizer recommendation rate to As-contaminated paddy soils. Therefore, for As-contaminated paddy soils with high levels of As, the application of Si fertilizer could result in increasing As phytotoxicity and uptake by rice. PMID:24892775

  16. Effect of organic matter and calcium carbonate on behaviors of cadmium adsorption-desorption on/from purple paddy soils.

    PubMed

    Zhao, Xiulan; Jiang, Tao; Du, Bin

    2014-03-01

    Batch experiments and sequential extraction analysis were employed to investigate the effects of soil organic matter and CaCO3 on the adsorption and desorption of cadmium (Cd(2+)) onto and from two purple paddy soils, an acidic purple paddy soil (APPS) and a calcareous purple paddy soil (CPPS). The Cd(2+) adsorption isotherms on both soils could be well-described by the Langmuir and Freundlich equations. CPPS had a higher capacity and a stronger affinity for Cd(2+) adsorption compared with APPS. The adsorption process of Cd(2+) on APPS was dominated by electrostatic attractions, whereas the adsorption mechanism varied depending on the Cd(2+) concentrations in equilibrium solutions on CPPS. At low equilibrium concentrations, the adsorption process was primarily specific adsorption, but nonspecific adsorption dominated at high equilibrium concentrations. Removal of organic matter decreased the amount of Cd(2+) adsorption on both of the soils, slightly affected the Cd(2+) desorption rate and exchangeable Cd (EXC-Cd) in APPS and increased the desorption rate and EXC-Cd in CPPS, suggesting that the effect of organic matter on Cd(2+) adsorption-desorption depends on the soils. CPPS and APPS containing CaCO3 exhibited higher adsorption amounts but lower desorption rates and lower proportions of EXC-Cd than those of their corresponding soils without CaCO3, demonstrating that CaCO3 played an important role in Cd(2+) specific adsorption on soil. The changes in the thermodynamic parameters, including free energy (ΔG(0)), enthalpy (ΔH(0)) and entropy (ΔS(0)), as evaluated by the Van't Hoff equations, indicated that the adsorption was a spontaneous and endothermic process with the primary interaction forces of dipole interactions and hydrogen bonds on APPS, whereas both physical and chemical interactions dominated the adsorption on CPPS. PMID:24289979

  17. Effects of rapeseed residue on lead and cadmium availability and uptake by rice plants in heavy metal contaminated paddy soil.

    PubMed

    Ok, Yong Sik; Usman, Adel R A; Lee, Sang Soo; Abd El-Azeem, Samy A M; Choi, Bongsu; Hashimoto, Yohey; Yang, Jae E

    2011-10-01

    Rapeseed (Brassica napus L.) has been cultivated for biodiesel production worldwide. Winter rapeseed is commonly grown in the southern part of Korea under a rice-rapeseed double cropping system. In this study, a greenhouse pot experiment was conducted to assess the effects of rapeseed residue applied as a green manure alone or in combinations with mineral N fertilizer on Cd and Pb speciation in the contaminated paddy soil and their availability to rice plant (Oryza sativa L.). The changes in soil chemical and biological properties in response to the addition of rapeseed residue were also evaluated. Specifically, the following four treatments were evaluated: 100% mineral N fertilizer (N100) as a control, 70% mineral N fertilizer+rapeseed residue (N70+R), 30% mineral N fertilizer+rapeseed residue (N30+R) and rapeseed residue alone (R). The electrical conductivity and exchangeable cations of the rice paddy soil subjected to the R treatment or in combinations with mineral N fertilizer treatment, N70+R and N30+R, were higher than those in soils subjected to the N100 treatment. However, the soil pH value with the R treatment (pH 6.3) was lower than that with N100 treatment (pH 6.9). Use of rapeseed residue as a green manure led to an increase in soil organic matter (SOM) and enhanced the microbial populations in the soil. Sequential extraction also revealed that the addition of rapeseed residue decreased the easily accessible fraction of Cd by 5-14% and Pb by 30-39% through the transformation into less accessible fractions, thereby reducing metal availability to the rice plant. Overall, the incorporation of rapeseed residue into the metal contaminated rice paddy soils may sustain SOM, improve the soil chemical and biological properties, and decrease the heavy metal phytoavailability. PMID:21764102

  18. Arsenic binding to iron(II) minerals produced by an iron(III)-reducing Aeromonas strain isolated from paddy soil.

    PubMed

    Wang, Xin-Jun; Chen, Xue-Ping; Kappler, Andreas; Sun, Guo-Xin; Zhu, Yong-Guan

    2009-11-01

    An iron reducing bacterial strain was isolated from a paddy soil and identified as a member of the Aeromonas group by 16S rRNA gene sequence analysis. When the cells were growing with dissolved Fe(III) as electron acceptor in the presence of As(V), Fe(II) minerals (siderite and vivianite) were formed and dissolved As was removed efficiently from solution. When the cells were growing with the Fe(III) hydroxide mineral (ferrihydrite) as electron acceptor in the presence of As(V), ferrihydrite was reduced and dissolved As(V) concentrations decreased sharply. Our results demonstrated firstly that members of the Aeromonas group can reduce Fe(III) in paddy soils, and secondly that iron reduction does not necessarily lead to arsenic mobilization. However, As immobilization can occur in environments that contain significant concentrations of counter ions such as bicarbonate and phosphate. PMID:19572768

  19. Draft Genome Sequence of Geobacter sp. Strain OR-1, an Arsenate-Respiring Bacterium Isolated from Japanese Paddy Soil

    PubMed Central

    Ehara, Ayaka; Suzuki, Haruo

    2015-01-01

    Here, we report a draft genome sequence of Geobacter sp. strain OR-1, an arsenate-respiring bacterium isolated from Japanese paddy soil. It contained two distinct arsenic islands, one including genes for a respiratory arsenate reductase (Arr) as well as for arsenic resistance (arsD-arsA-acr3-arsR-arrA-arrB) and the second containing only genes for arsenic resistance. PMID:25635012

  20. Draft Genome Sequence of Geobacter sp. Strain OR-1, an Arsenate-Respiring Bacterium Isolated from Japanese Paddy Soil.

    PubMed

    Ehara, Ayaka; Suzuki, Haruo; Amachi, Seigo

    2015-01-01

    Here, we report a draft genome sequence of Geobacter sp. strain OR-1, an arsenate-respiring bacterium isolated from Japanese paddy soil. It contained two distinct arsenic islands, one including genes for a respiratory arsenate reductase (Arr) as well as for arsenic resistance (arsD-arsA-acr3-arsR-arrA-arrB) and the second containing only genes for arsenic resistance. PMID:25635012

  1. The large-scale distribution of ammonia oxidizers in paddy soils is driven by soil pH, geographic distance, and climatic factors

    PubMed Central

    Hu, Hang-Wei; Zhang, Li-Mei; Yuan, Chao-Lei; Zheng, Yong; Wang, Jun-Tao; Chen, Deli; He, Ji-Zheng

    2015-01-01

    Paddy soils distribute widely from temperate to tropical regions, and are characterized by intensive nitrogen fertilization practices in China. Mounting evidence has confirmed the functional importance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in soil nitrification, but little is known about their biogeographic distribution patterns in paddy ecosystems. Here, we used barcoded pyrosequencing to characterize the effects of climatic, geochemical and spatial factors on the distribution of ammonia oxidizers from 11 representative rice-growing regions (75–1945 km apart) of China. Potential nitrification rates varied greatly by more than three orders of magnitude, and were significantly correlated with the abundances of AOA and AOB. The community composition of ammonia oxidizer was affected by multiple factors, but changes in relative abundances of the major lineages could be best predicted by soil pH. The alpha diversity of AOA and AOB displayed contrasting trends over the gradients of latitude and atmospheric temperature, indicating a possible niche separation between AOA and AOB along the latitude. The Bray–Curtis dissimilarities in ammonia-oxidizing community structure significantly increased with increasing geographical distance, indicating that more geographically distant paddy fields tend to harbor more dissimilar ammonia oxidizers. Variation partitioning analysis revealed that spatial, geochemical and climatic factors could jointly explain majority of the data variation, and were important drivers defining the ecological niches of AOA and AOB. Our findings suggest that both AOA and AOB are of functional importance in paddy soil nitrification, and ammonia oxidizers in paddy ecosystems exhibit large-scale biogeographic patterns shaped by soil pH, geographic distance, and climatic factors. PMID:26388866

  2. The large-scale distribution of ammonia oxidizers in paddy soils is driven by soil pH, geographic distance, and climatic factors.

    PubMed

    Hu, Hang-Wei; Zhang, Li-Mei; Yuan, Chao-Lei; Zheng, Yong; Wang, Jun-Tao; Chen, Deli; He, Ji-Zheng

    2015-01-01

    Paddy soils distribute widely from temperate to tropical regions, and are characterized by intensive nitrogen fertilization practices in China. Mounting evidence has confirmed the functional importance of ammonia-oxidizing archaea (AOA) and bacteria (AOB) in soil nitrification, but little is known about their biogeographic distribution patterns in paddy ecosystems. Here, we used barcoded pyrosequencing to characterize the effects of climatic, geochemical and spatial factors on the distribution of ammonia oxidizers from 11 representative rice-growing regions (75-1945 km apart) of China. Potential nitrification rates varied greatly by more than three orders of magnitude, and were significantly correlated with the abundances of AOA and AOB. The community composition of ammonia oxidizer was affected by multiple factors, but changes in relative abundances of the major lineages could be best predicted by soil pH. The alpha diversity of AOA and AOB displayed contrasting trends over the gradients of latitude and atmospheric temperature, indicating a possible niche separation between AOA and AOB along the latitude. The Bray-Curtis dissimilarities in ammonia-oxidizing community structure significantly increased with increasing geographical distance, indicating that more geographically distant paddy fields tend to harbor more dissimilar ammonia oxidizers. Variation partitioning analysis revealed that spatial, geochemical and climatic factors could jointly explain majority of the data variation, and were important drivers defining the ecological niches of AOA and AOB. Our findings suggest that both AOA and AOB are of functional importance in paddy soil nitrification, and ammonia oxidizers in paddy ecosystems exhibit large-scale biogeographic patterns shaped by soil pH, geographic distance, and climatic factors. PMID:26388866

  3. Methanogenic degradation of lignin-derived monoaromatic compounds by microbial enrichments from rice paddy field soil.

    PubMed

    Kato, Souichiro; Chino, Kanako; Kamimura, Naofumi; Masai, Eiji; Yumoto, Isao; Kamagata, Yoichi

    2015-01-01

    Anaerobic degradation of lignin-derived aromatics is an important metabolism for carbon and nutrient cycles in soil environments. Although there are some studies on degradation of lignin-derived aromatics by nitrate- and sulfate-reducing bacteria, knowledge on their degradation under methanogenic conditions are quite limited. In this study, methanogenic microbial communities were enriched from rice paddy field soil with lignin-derived methoxylated monoaromatics (vanillate and syringate) and their degradation intermediates (protocatechuate, catechol, and gallate) as the sole carbon and energy sources. Archaeal community analysis disclosed that both aceticlastic (Methanosarcina sp.) and hydrogenotrophic (Methanoculleus sp. and Methanocella sp.) methanogens dominated in all of the enrichments. Bacterial community analysis revealed the dominance of acetogenic bacteria (Sporomusa spp.) only in the enrichments on the methoxylated aromatics, suggesting that Sporomusa spp. initially convert vanillate and syringate into protocatechuate and gallate, respectively, with acetogenesis via O-demethylation. As the putative ring-cleavage microbes, bacteria within the phylum Firmicutes were dominantly detected from all of the enrichments, while the dominant phylotypes were not identical between enrichments on vanillate/protocatechuate/catechol (family Peptococcaceae bacteria) and on syringate/gallate (family Ruminococcaceae bacteria). This study demonstrates the importance of cooperation among acetogens, ring-cleaving fermenters/syntrophs and aceticlastic/hydrogenotrophic methanogens for degradation of lignin-derived aromatics under methanogenic conditions. PMID:26399549

  4. Effect of microbial mediated iron plaque reduction on arsenic mobility in paddy soil.

    PubMed

    Wang, Xinjun; Chen, Xueping; Yang, Jing; Wang, Zhaosu; Sun, Guoxin

    2009-01-01

    The potential of microbial mediated iron plaque reduction, and associated arsenic (As) mobility were examined by iron reducing bacteria enriched from As contaminated paddy soil. To our knowledge, this is the first time to report the impact of microbial iron plaque reduction on As mobility. Iron reduction occurred during the inoculation of iron reducing enrichment culture in the treatments with iron plaque and ferrihydrite as the electron acceptors, respectively. The Fe(II) concentration with the treatment of anthraquinone-2, 6-disulfonic acid (AQDS) and iron reducing bacteria increased much faster than the control. Arsenic released from iron plaque with the iron reduction, and a significant correlation between Fe(II) and total As in culture was observed. However, compared with control, the increasing rate of As was inhibited by iron reducing bacteria especially in the presence of AQDS. In addition, the concentrations of As(III) and As(V) in abiotic treatments were higher than those in the biotic treatments at day 30. These results indicated that both microbial and chemical reductions of iron plaque caused As release from iron plaque to aqueous phase, however, microbial iron reduction induced the formation of more crystalline iron minerals, leading to As sequestration. In addition, the presence of AQDS in solution can accelerate the iron reduction, the As release from iron plaque and subsequently the As retention in the crystalline iron mineral. Thus, our results suggested that it is possible to remediate As contaminated soils by utilizing iron reducing bacteria and AQDS. PMID:20108691

  5. Methanogenic degradation of lignin-derived monoaromatic compounds by microbial enrichments from rice paddy field soil

    PubMed Central

    Kato, Souichiro; Chino, Kanako; Kamimura, Naofumi; Masai, Eiji; Yumoto, Isao; Kamagata, Yoichi

    2015-01-01

    Anaerobic degradation of lignin-derived aromatics is an important metabolism for carbon and nutrient cycles in soil environments. Although there are some studies on degradation of lignin-derived aromatics by nitrate- and sulfate-reducing bacteria, knowledge on their degradation under methanogenic conditions are quite limited. In this study, methanogenic microbial communities were enriched from rice paddy field soil with lignin-derived methoxylated monoaromatics (vanillate and syringate) and their degradation intermediates (protocatechuate, catechol, and gallate) as the sole carbon and energy sources. Archaeal community analysis disclosed that both aceticlastic (Methanosarcina sp.) and hydrogenotrophic (Methanoculleus sp. and Methanocella sp.) methanogens dominated in all of the enrichments. Bacterial community analysis revealed the dominance of acetogenic bacteria (Sporomusa spp.) only in the enrichments on the methoxylated aromatics, suggesting that Sporomusa spp. initially convert vanillate and syringate into protocatechuate and gallate, respectively, with acetogenesis via O-demethylation. As the putative ring-cleavage microbes, bacteria within the phylum Firmicutes were dominantly detected from all of the enrichments, while the dominant phylotypes were not identical between enrichments on vanillate/protocatechuate/catechol (family Peptococcaceae bacteria) and on syringate/gallate (family Ruminococcaceae bacteria). This study demonstrates the importance of cooperation among acetogens, ring-cleaving fermenters/syntrophs and aceticlastic/hydrogenotrophic methanogens for degradation of lignin-derived aromatics under methanogenic conditions. PMID:26399549

  6. Archaeal Communities in a Heterogeneous Hypersaline-Alkaline Soil.

    PubMed

    Navarro-Noya, Yendi E; Valenzuela-Encinas, César; Sandoval-Yuriar, Alonso; Jiménez-Bueno, Norma G; Marsch, Rodolfo; Dendooven, Luc

    2015-01-01

    In this study the archaeal communities in extreme saline-alkaline soils of the former lake Texcoco, Mexico, with electrolytic conductivities (EC) ranging from 0.7 to 157.2 dS/m and pH from 8.5 to 10.5 were explored. Archaeal communities in the 0.7 dS/m pH 8.5 soil had the lowest alpha diversity values and were dominated by a limited number of phylotypes belonging to the mesophilic Candidatus Nitrososphaera. Diversity and species richness were higher in the soils with EC between 9.0 and 157.2 dS/m. The majority of OTUs detected in the hypersaline soil were members of the Halobacteriaceae family. Novel phylogenetic branches in the Halobacteriales class were detected in the soil, and more abundantly in soil with the higher pH (10.5), indicating that unknown and uncharacterized Archaea can be found in this soil. Thirteen different genera of the Halobacteriaceae family were identified and were distributed differently between the soils. Halobiforma, Halostagnicola, Haloterrigena, and Natronomonas were found in all soil samples. Methanogenic archaea were found only in soil with pH between 10.0 and 10.3. Retrieved methanogenic archaea belonged to the Methanosarcinales and Methanomicrobiales orders. The comparison of the archaeal community structures considering phylogenetic information (UniFrac distances) clearly clustered the communities by pH. PMID:26074731

  7. Archaeal Communities in a Heterogeneous Hypersaline-Alkaline Soil

    PubMed Central

    Navarro-Noya, Yendi E.; Valenzuela-Encinas, César; Sandoval-Yuriar, Alonso; Jiménez-Bueno, Norma G.; Marsch, Rodolfo

    2015-01-01

    In this study the archaeal communities in extreme saline-alkaline soils of the former lake Texcoco, Mexico, with electrolytic conductivities (EC) ranging from 0.7 to 157.2 dS/m and pH from 8.5 to 10.5 were explored. Archaeal communities in the 0.7 dS/m pH 8.5 soil had the lowest alpha diversity values and were dominated by a limited number of phylotypes belonging to the mesophilic Candidatus Nitrososphaera. Diversity and species richness were higher in the soils with EC between 9.0 and 157.2 dS/m. The majority of OTUs detected in the hypersaline soil were members of the Halobacteriaceae family. Novel phylogenetic branches in the Halobacteriales class were detected in the soil, and more abundantly in soil with the higher pH (10.5), indicating that unknown and uncharacterized Archaea can be found in this soil. Thirteen different genera of the Halobacteriaceae family were identified and were distributed differently between the soils. Halobiforma, Halostagnicola, Haloterrigena, and Natronomonas were found in all soil samples. Methanogenic archaea were found only in soil with pH between 10.0 and 10.3. Retrieved methanogenic archaea belonged to the Methanosarcinales and Methanomicrobiales orders. The comparison of the archaeal community structures considering phylogenetic information (UniFrac distances) clearly clustered the communities by pH. PMID:26074731

  8. Cadmium Speciation and Release Kinetics in a Thai Paddy Soil: An In situ Molecular-Scale Investigation Using X-ray Absorption Spectroscopy (XAS)

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transformation of Cd species can occur in response to fluctuating soil moisture conditions. Redox potential is a master variable controlling Cd speciation and bioavailability in paddy soils, and soil pH influences the transport and fate of Cd (e.g., via sorption to organic matter or metal oxides an...

  9. [Dynamics of the mineralization and transformation of rice photosynthesized carbon in paddy soils--a batch incubation experiment].

    PubMed

    Tan, Li-Min; Peng, Pei-Qin; Li, Ke-Lin; Li, Bao-Zhen; Nie, San-An; Ge, Ti-Da; Tong, Cheng-Li; Wu, Jin-Shui

    2014-01-01

    Photosynthesized carbon is an important part in C cycling of "atmosphere-plant-soil" and is the source of soil organic carbon (SOC), but its mineralization and transformation dynamics in paddy soils remains still unclear. Therefore, a batch incubation experiment was conducted to investigate the mineralization and transformation of rice photosynthesized carbon in paddy soils after rice harvest. The results showed that the mineralization rate of native SOC ranged from 4.44 to 17.8 microg x (g x d)(-1), while that of photosynthesized carbon (new carbon) was 0.15- 1.51 micro x (gx d)(-1) during the course of 100-day-incubation span. Rice photosynthesized carbon input significantly influenced the soil active carbon (DOC, MBC) transformation. During the incubation period (100 d), the amount of 14C-DOC transformation ranged from 1.89 to 5.32 mg x 8 kg(-1), and that of native DOC varied from 61.13 to 90.65 mg x kg(-2), with the transformation rates ranged from 0.18 to 0.34 mg x (kg x d)(-1) and from 4.10 to 5.48 mg. (kg x d)(-1), respectively. However, the 14C-MBC and native original MBC were 10.92-44.11 mg x kg(-1) and 463.31-1153.46 mg x kg(-1), respectively, and their transformation rates were 0.80-2.87, 41.60-74.46 mg x (kg-d)(-1), respectively. It suggested that the turnover of MBC was greater than that of DOC. Furthermore, "new carbon" was easier to be mineralized and decomposed than native SOC. The mineralized portion in "new carbon" was 13.5%-20.2%, whereas that in native SOC was only 2.2%-3.7%. Therefore, we concluded that the incorporation of rice photosynthesized carbon was vital to maintain the soil carbon sink for paddy soils. PMID:24720210

  10. Arsenic release from flooded paddy soils is influenced by speciation, Eh, pH, and iron dissolution.

    PubMed

    Yamaguchi, N; Nakamura, T; Dong, D; Takahashi, Y; Amachi, S; Makino, T

    2011-05-01

    Arsenic (As) is highly mobilized when paddy soil is flooded, causing increased uptake of As by rice. We investigated factors controlling soil-to-solution partitioning of As under anaerobic conditions. Changes in As and iron (Fe) speciation due to flooded incubation of two paddy soils (soils A and B) were investigated by HPLC/ICP-MS and XANES. The flooded incubation resulted in a decrease in Eh, a rise in pH, and an increase in the As(III) fraction in the soil solid phase up to 80% of the total As in the soils. The solution-to-soil ratio of As(III) and As(V) (R(L/S)) increased with pH due to the flooded incubation. The R(L/S) for As(III) was higher than that for As(V), indicating that As(III) was more readily released from soil to solution than was As(V). Despite the small differences in As concentrations between the two soils, the amount of As dissolved by anaerobic incubation was lower in soil A. With the development of anaerobic conditions, Fe(II) remained in the soil solid phase as the secondary mineral siderite, and a smaller amount of Fe was dissolved from soil A than from soil B. The dissolution of Fe minerals rather than redox reaction of As(V) to As(III) explained the different dissolution amounts of As in the two paddy soils. Anaerobic incubation for 30 d after the incomplete suppression of microbial activity caused a drop in Eh. However, this decline in Eh did not induce the transformation of As(V) to As(III) in either the soil solid or solution phases, and the dissolution of As was limited. Microbial activity was necessary for the reductive reaction of As(V) to As(III) even when Eh reached the condition necessary for the dominance of As(III). Ratios of released As to Fe from the soils were decreased with incubation time during both anaerobic incubation and abiotic dissolution by sodium ascorbate, suggesting that a larger amount of As was associated with an easily soluble fraction of Fe (hydr) oxide in amorphous phase and/or smaller particles. PMID

  11. Effectiveness of lime and peat applications on cadmium availability in a paddy soil under various moisture regimes.

    PubMed

    Chen, Yanhui; Xie, Tuanhui; Liang, Qiaofeng; Liu, Mengjiao; Zhao, Mingliu; Wang, Mingkuang; Wang, Guo

    2016-04-01

    In paddy soils, amendments and moisture play important role in the immobilization of cadmium (Cd). The effects of applying lime, peat, and a combination of both on soil Eh, pH, and Cd availability in contaminated soils were investigated under wetted (80 ± 5 % of water holding capacity) and flooded (completely submerged) conditions. In wetted soils, there was little change in Eh, compared to flooded soils where Eh reduced rapidly. Amendments of lime only or in a mixture with peat increased soil pH to different degrees, depending on the lime application rate. However, peat addition only slightly affected soil pH. The decreased Cd availability in flooded soils was related to submergence duration and was significantly lower than that in wetted soils after 14 days. Liming wetted and flooded soils decreased exchangeable Cd and increased carbonates or Fe-Mn oxides bound fractions, while peat addition transformed Cd from carbonates to organic matter bound fractions. The combined application of peat and lime generally showed better inhibitory effects on the availability of Cd than separately application of lime or peat. Higher application rates of lime, peat, or their mixture were more effective at reducing Cd contamination in flooded soil. This indicates that application of peat and lime mixture under flooded conditions was most effective for in situ remediation of Cd-contaminated soils. Further studies are required to assess the long-term effectiveness of the peat and lime mixture on Cd availability in paddy soils. PMID:26755172

  12. Anaerobic arsenite oxidation by an autotrophic arsenite-oxidizing bacterium from an arsenic-contaminated paddy soil.

    PubMed

    Zhang, Jun; Zhou, Wuxian; Liu, Bingbing; He, Jian; Shen, Qirong; Zhao, Fang-Jie

    2015-05-19

    Microbe-mediated arsenic (As) redox reactions play an important role in the biogeochemical cycling of As. Reduction of arsenate [As(V)] generally leads to As mobilization in paddy soils and increased As availability to rice plants, whereas oxidation of arsenite [As(III)] results in As immobilization. A novel chemoautotrophic As(III)-oxidizing bacterium, designated strain SY, was isolated from an As-contaminated paddy soil. The isolate was able to derive energy from the oxidation of As(III) to As(V) under both aerobic and anaerobic conditions using O2 or NO3(-) as the respective electron acceptor. Inoculation of the washed SY cells into a flooded soil greatly enhanced As(III) oxidation to As(V) both in the solution and adsorbed phases of the soil. Strain SY is phylogenetically closely related to Paracoccus niistensis with a 16S rRNA gene similarity of 96.79%. The isolate contains both the denitrification and ribulose 1,5-bisphosphate carboxylase/oxygenase gene clusters, underscoring its ability to denitrify and to fix CO2 while coupled to As(III) oxidation. Deletion of the aioA gene encoding the As(III) oxidase subunit A abolished the As(III) oxidation ability of strain SY and led to increased sensitivity to As(III), suggesting that As(III) oxidation is a detoxification mechanism in this bacterium under aerobic and heterotrophic growth conditions. Analysis of the aioA gene clone library revealed that the majority of the As(III)-oxidizing bacteria in the soil were closely related to the genera Paracoccus of α-Proteobacteria. Our results provide direct evidence for As(III) oxidation by Paracoccus species and suggest that these species may play an important role in As(III) oxidation in paddy soils under both aerobic and denitrifying conditions. PMID:25905768

  13. Controlled-release urea commingled with rice seeds reduced emission of ammonia and nitrous oxide in rice paddy soil.

    PubMed

    Yang, Yuechao; Zhang, Min; Li, Yuncong; Fan, Xiaohui; Geng, Yuqing

    2013-11-01

    Reduction of ammonia (NH) and nitrous oxide (NO) emission and enhanced nitrogen (N) fertilizer use efficiency have been investigated with different N fertilizer management and application methods for irrigated rice production. Few studies have examined NH and NO emissions from rice paddy soil when commingling controlled release urea with rice seeds. The objective of this study was to assess NH volatilization and NO emission from a novel controlled-release urea formulation (CRU-180) when commingled at the full application rate with seeds in a single application during the preparation of plant plugs at the nursery stage. The experiment was conducted as a factorial design with two fertilizer sources (conventional urea and CRU-180), four rates (0, 100, 200, and 300 kg N ha), and three replicates. The entire amount of CRU-180 was incorporated into each plug with germinated seed. The conventional urea was split into four applications based on the standard practice for fertilizer application. The CRU-180 treatments reduced the NH and NO concentration in the paddy flood water and paddy soil solution as compared with the conventional urea treatments. The percentage of applied N fertilizer emitted as NH volatilization and NO emission in the CRU-180 treatments was only about 10% of that from the conventional urea treatments at the same N application rate. The application of CRU-180 with seeds offers a novel N fertilizer management technique, a method to reduce environmental impacts associated with rice production and the cost of rice production. PMID:25602407

  14. Arsenic concentrations in paddy soil and rice and health implications for major rice-growing regions of Cambodia.

    PubMed

    Seyfferth, Angelia L; McCurdy, Sarah; Schaefer, Michael V; Fendorf, Scott

    2014-05-01

    Despite the global importance of As in rice, research has primarily focused on Bangladesh, India, China, and the United States with limited attention given to other countries. Owing to both indigenous As within the soil and the possible increases arising from the onset of irrigation with groundwater, an assessment of As in rice within Cambodia is needed, which offers a "base-case" comparison against sediments of similar origin that comprise rice paddy soils where As-contaminated water is used for irrigation (e.g., Bangladesh). Here, we evaluated the As content of rice from five provinces (Kandal, Prey Veng, Battambang, Banteay Meanchey, and Kampong Thom) in the rice-growing regions of Cambodia and coupled that data to soil-chemical factors based on extractions of paddy soil collected and processed under anoxic conditions. At total soil As concentrations ranging 0.8 to 18 μg g(-1), total grain As concentrations averaged 0.2 μg g(-1) and ranged from 0.1 to 0.37 with Banteay Meanchey rice having significantly higher values than Prey Veng rice. Overall, soil-extractable concentrations of As, Fe, P, and Si and total As were poor predictors of grain As concentrations. While biogeochemical factors leading to reduction of As(V)-bearing Fe(III) oxides are likely most important for predicting plant-available As, husk and straw As concentrations were the most significant predictors of grain-As levels among our measured parameters. PMID:24712677

  15. [Distribution characteristics of soil profile nitrous oxide concentration in paddy fields with different rice-upland crop rotation systems].

    PubMed

    Liu, Ping-li; Zhang, Xiao-lin; Xiong, Zheng-qin; Huang, Tai-qing; Ding, Min; Wang, Jin-yang

    2011-09-01

    To investigate the dynamic distribution patterns of nitrous oxide (N2O) in the soil profiles in paddy fields with different rice-upland crop rotation systems, a special soil gas collection device was adopted to monitor the dynamics of N2O at the soil depths 7, 15, 30, and 50 cm in the paddy fields under both flooding and drainage conditions. Two rotation systems were installed, i.e., wheat-single rice and oilseed rape-double rice, each with or without nitrogen (N) application. Comparing with the control, N application promoted the N2O production in the soil profiles significantly (P < 0.01), and there existed significant correlations in the N2O concentration among the four soil depths during the whole observation period (P < 0.01). In the growth seasons of winter wheat and oilseed rape under drainage condition and with or without N application, the N2O concentrations at the soil depths 30 cm and 50 cm were significantly higher than those at the soil depths 7 cm and 15 cm; whereas in the early rice growth season under flooding condition and without N application, the N2O concentrations at the soil depth 7 cm and 15 cm were significantly higher than those at the soil depths 30 cm and 50 cm (P < 0.05). No significant differences were observed in the N2O concentrations at the test soil depths among the other rice cropping treatments. The soil N2O concentrations in the treatments without N application peaked in the transitional period from the upland crops cropping to rice planting, while those in the treatments with N application peaked right after the second topdressing N of upland crops. Relatively high soil N2O concentrations were observed at the transitional period from the upland crops cropping to rice planting. PMID:22126049

  16. Bacillus haikouensis sp. nov., a facultatively anaerobic halotolerant bacterium isolated from a paddy soil.

    PubMed

    Li, Jibing; Yang, Guiqin; Lu, Qin; Zhao, Yong; Zhou, Shungui

    2014-10-01

    A Gram-stain positive, rod-shaped, endospore-forming and facultatively anaerobic halotolerant bacterium, designated as C-89(T), was isolated from a paddy field soil in Haikou, Hainan Province, People's Republic of China. Optimal growth was observed at 37 °C and pH 7.0 in the presence of 4% NaCl (w/v). The predominant menaquinone was identified as MK-7, the major cellular fatty acids were identified as anteiso-C(15:0) and iso-C(15:0), and the major cellular polar lipids were identified as phosphatidylethanolamine, diphosphatidylglycerol, phosphatidylglycerol and two unknown phospholipids. The peptidoglycan type was determined to be based on meso-DAP. Based on 16S rRNA gene sequence similarity, the closest phylogenetic relatives were identified as Bacillus vietnamensis JCM 11124(T) (98.8% sequence similarity), Bacillus aquimaris JCM 11545(T) (98.6%) and Bacillus marisflavi JCM 11544(T) (98.5%). The DNA G+C content of strain C-89(T) was determined to be 45.4 mol%. The DNA-DNA relatedness values of strain C-89(T) with its closest relatives were below 18%. Therefore, on the basis of phylogenetic, chemotaxonomic, and phenotypic results, strain C-89(T) can be considered to represent a novel species within the genus Bacillus, for which the name Bacillus haikouensis sp. nov., is proposed. The type strain is C-89(T) (=KCTC 33545(T) = CCTCC AB 2014076(T)). PMID:25100188

  17. Mitigating yield-scaled greenhouse gas emissions through combined application of soil amendments: A comparative study between temperate and subtropical rice paddy soils.

    PubMed

    Ali, Muhammad Aslam; Kim, P J; Inubushi, K

    2015-10-01

    Effects of different soil amendments were investigated on methane (CH4) and nitrous oxide (N2O) emissions, global warming potential (GWP) and yield scaled GWPs in paddy soils of Republic of Korea, Japan and Bangladesh. The experimental treatments were NPK only, NPK+fly ash, NPK+silicate slag, NPK+phosphogypsum(PG), NPK+blast furnace slag (BFS), NPK+revolving furnace slag (RFS), NPK+silicate slag (50%)+RFS (50%), NPK+biochar, NPK+biochar+Azolla-cyanobacteria, NPK+silicate slag+Azolla-cyanobacteria, NPK+phosphogypsum (PG)+Azolla-cyanobacteria. The maximum decrease in cumulative seasonal CH4 emissions was recorded 29.7% and 32.6% with Azolla-cyanobacteria plus phospho-gypsum amendments in paddy soils of Japan and Bangladesh respectively, followed by 22.4% and 26.8% reduction with silicate slag plus Azolla-cyanobacteria application. Biochar amendments in paddy soils of Japan and Bangladesh decreased seasonal cumulative N2O emissions by 31.8% and 20.0% respectively, followed by 26.3% and 25.0% reduction with biochar plus Azolla-cyanobacteria amendments. Although seasonal cumulative CH4 emissions were significantly increased by 9.5-14.0% with biochar amendments, however, global warming potentials were decreased by 8.0-12.0% with cyanobacterial inoculation plus biochar amendments. The maximum decrease in GWP was calculated 22.0-30.0% with Azolla-cyanobacteria plus silicate slag amendments. The evolution of greenhouse gases per unit grain yield (yield scaled GWP) was highest in the NPK treatment, which was decreased by 43-50% from the silicate slag and phosphogypsum amendments along with Azolla-cyanobacteria inoculated rice planted soils. Conclusively, it is recommended to incorporate Azolla-cyanobacteria with inorganic and organic amendments for reducing GWP and yield scaled GWP from the rice planted paddy soils of temperate and subtropical countries. PMID:26011612

  18. [Variations of arsenic species in the solution of arsenic-contaminated paddy soil under flooding and at different temperatures].

    PubMed

    Wang, Zhao; Cui, Jiang-Hui; Chen, Zheng; Lu, Xiu-Jun; Liu, Wen-Ju

    2013-05-01

    Taking arsenic (As)-contaminated paddy soil as test object, and by using high performance liquid chromatography inductively coupled plasma-mass spectrometry (HPLC-ICP-MS), this paper studied the variations of As species in soil solution when the soil was sterilized or non-sterilized and incubated at different temperatures (5, 27, and 50 degrees C) under flooding. In the soil solution (pore water), only As(III) (arsenite), As(V) (arsenate), and DMA(V) ( dimethylarsinic acid) were detected, but no MMA(V)(mono methylarsinic acid) was found. With the increasing time of flooding and at the test temperatures, arsenite became the predominant species, averagely accounting for 64%, followed by As(V), with the proportion of 35%, and DMA(V), with the least proportion of 1%. Soil sterilization or non-sterilization had less effect on the concentrations of As(III) and DMA(V) in the soil solution, but remarkably affected the reduction of As(V) and the methylation of As(III). The promotion effect of soil sterilization decreased gradually with the increasing time of flooding and incubation. At 50 degrees C and after flooded for 23 days, the DMA(V) concentration in sterilized soil solution was the highest and up to 23.7 ng x mL(-1), indicating that some thermophilic microbes remained in sterilized soil became predominant species, and promoted the methylation of As(III) In sum, the total arsenic concentration in non-sterilized soil at incubation temperature 27 degrees C and flooded for 23 days was relatively low (501 ng x mL(-1)), and thus, in As-contaminated paddy rice planting areas, to adopt the water management mode of short cycle flooding-non-flooding could decrease the As level in soil solution as far as possible, and in the same time, save water resources and ensure yielding. PMID:24015564

  19. Silicon improves maize photosynthesis in saline-alkaline soils.

    PubMed

    Xie, Zhiming; Song, Ri; Shao, Hongbo; Song, Fengbin; Xu, Hongwen; Lu, Yan

    2015-01-01

    The research aimed to determine the effects of Si application on photosynthetic characteristics of maize on saline-alkaline soil, including photosynthetic rate (P n ), stomatal conductance (g s ), transpiration rate (E), and intercellular CO2 concentration (C i ) of maize in the field with five levels (0, 45, 90, 150, and 225 kg · ha(-1)) of Si supplying. Experimental results showed that the values of P n, g s, and C i of maize were significantly enhanced while the values of E of maize were dramatically decreased by certain doses of silicon fertilizers, which meant that Si application with proper doses significantly increased photosynthetic efficiency of maize in different growth stages under stressing environment of saline-alkaline soil. The optimal dose of Si application in this experiment was 150 kg · ha(-1) Si. It indicated that increase in maize photosynthesis under saline-alkaline stress took place by Si application with proper doses, which is helpful to improve growth and yield of maize. PMID:25629083

  20. Silicon Improves Maize Photosynthesis in Saline-Alkaline Soils

    PubMed Central

    Xie, Zhiming; Song, Ri; Shao, Hongbo; Song, Fengbin; Xu, Hongwen; Lu, Yan

    2015-01-01

    The research aimed to determine the effects of Si application on photosynthetic characteristics of maize on saline-alkaline soil, including photosynthetic rate (Pn), stomatal conductance (gs), transpiration rate (E), and intercellular CO2 concentration (Ci) of maize in the field with five levels (0, 45, 90, 150, and 225 kg·ha−1) of Si supplying. Experimental results showed that the values of Pn, gs, and Ci of maize were significantly enhanced while the values of E of maize were dramatically decreased by certain doses of silicon fertilizers, which meant that Si application with proper doses significantly increased photosynthetic efficiency of maize in different growth stages under stressing environment of saline-alkaline soil. The optimal dose of Si application in this experiment was 150 kg·ha−1 Si. It indicated that increase in maize photosynthesis under saline-alkaline stress took place by Si application with proper doses, which is helpful to improve growth and yield of maize. PMID:25629083

  1. Predicting Phosphorus Release from Anaerobic, Alkaline, Flooded Soils.

    PubMed

    Amarawansha, Geethani; Kumaragamage, Darshani; Flaten, Don; Zvomuya, Francis; Tenuta, Mario

    2016-07-01

    Anaerobic conditions induced by prolonged flooding often lead to an enhanced release of phosphorus (P) to floodwater; however, this effect is not consistent across soils. This study aimed to develop an index to predict P release potential from alkaline soils under simulated flooded conditions. Twelve unamended or manure-amended surface soils from Manitoba were analyzed for basic soil properties, Olsen P (Ols-P), Mehlich-3 extractable total P (M3P), Mehlich-3 extractable molybdate-reactive P (M3P), water extractable P (WEP), soil P fractions, single-point P sorption capacity (P), and Mehlich-3 extractable Ca (M3Ca), and Mg (M3Mg). Degree of P saturation (DPS) was calculated using Ols-P, M3P or M3P as the intensity factor, and an estimated adsorption maximum based on either P or M3Ca + M3Mg as the capacity factor. To develop the model, we used the previously reported floodwater dissolved reactive P (DRP) concentration changes during 8 wk of flooding for the same unamended and manured soils. Relative changes in floodwater DRP concentration (DRP), calculated as the ratio of maximum to initial DRP concentration, ranged from 2 to 15 across ten of the soils, but were ≤1.5 in the two soils with the greatest clay content. Partial least squares analysis indicated that DPS3 calculated using M3P as the intensity factor and (2 × P) + M3P as the capacity factor with clay percentage can effectively predict DRP ( = 0.74). Results suggest that P release from a soil to floodwater may be predicted using simple and easily measurable soil properties measured before flooding, but validation with more soils is needed. PMID:27380097

  2. [Effect of monocalcium phosphate and potassium chloride on nitrogen leaching in paddy soil].

    PubMed

    Li, Shou-tian; Zhou, Jian-min; Wang, Huo-yan; Du, Chang-wen; Chen, Xiao-qin

    2004-05-01

    In this article, influence of monocalcium phosphate and potassium chloride application on nitrogen leaching in paddy soil of Taihu region was studied by soil column leaching. The results showed that nitrate nitrogen was the main component of nitrogen leaching without urea application which accounts for 93.39 percent of total nitrogen leaching (including urea, ammonium, and nitrate nitrogen). Amounts of urea, ammonium, and nitrate nitrogen in leachates increased significantly after urea application which account for 3.95, 15.25, and 80.80 percent of total nitrogen leaching respectively and for 0.26, 0.80, and 2.54 percent of applied nitrogen respectively. Amounts of urea, ammonium, and nitrate nitrogen in leachates were enhanced prominently by monocalcium phosphate or potassium chloride which are 4.54, 24.11, 71.34, and 3.45, 24.53, 72.02 percent of total nitrogen leaching respectively, and which are 0.39, 1.86, 3.34, and 0.32, 2.12, 4.06 percent of applied nitrogen separately. There is interactive influence on nitrogen leaching after application of monocalcium phosphate and potassium chloride together, and amounts of urea, ammonium, and nitrate nitrogen were 4.10, 27.35, and 68.55 percent of total nitrogen leaching, and 0.42, 2.60, and 4.26 percent of total applied nitrogen respectively. The leaching order of different form nitrogen followed as urea N > ammonium N > nitrate N, and leaching amounts of different form nitrogen followed as urea N < ammonium N < nitrate N. PMID:15327269

  3. Soil carbon cycle of different saline and alkaline soils under cotton fields in Tarim River Basin

    NASA Astrophysics Data System (ADS)

    Zhao, Xiaoning; Zhao, Chengyi; Stahr, Karl; Kuzyakov, Yakov

    2015-04-01

    Calcium carbonate is the most common form of carbon (C) in semiarid and arid soils. Depending on pH and salinity changes, soils can act as sink or source of atmospheric CO2 as well as contribute to C exchange between CO2 and CaCO3 leading to formation of pedogenic carbonates. However, the rates of these processes and the effects of environmental factors remains unknown. 14CO2 was used to assess carbonate recrystallization in 4 saline and alkaline soils (Aksu alkaline, Aksu saline, Yingbazar alkaline, Yingbazar saline) (EC = 0.32, 1.35, 1.72, 3.67 (1:20) mS cm-1, pH = 8.5, 8.2, 8.9, 7.9 respectively) and to trace the C exchange in the soils of the Tarim River basin depending on CO2 concentrations in soils (0.02%, 0.04%, 0.2%, 0.4% and 4%). 14C was traced in soil water and air as well as in carbonates. The highest 14C in 14CO2 (95% of the 14C input) was observed in Aksu alkaline soil and the highest 14C incorporation in CaCO3 (54%) was observed in Yingbazar saline soil. There were close negative linear relationships between initial CO2 concentrations (0.04%, 0.4% and 4%) and the 14C in Ca14CO3 and in 14CO2. The carbonate recrystallization rate increased with the CO2 concentration and were depended on the recrystalliztion period. The average carbonate recrystallization rate was highest at 4% CO2 concentration for Yingbazar saline soil (6.59×10-4 % per day) and the lowest at 0.04% CO2 concentration for Aksu alkaline soil (0.03×10-4 % per day). The carbonate recrystallization rate linearly increased with the soil EC and with 0.04% and 0.4% CO2 concentration , whereas the carbonate recrystallization rate decreased with pH. The highest CO2 concentration of 4% can 10 to 100 times shorten the full carbonate recrystallization of the remaining primary carbonates compared to lower CO2 concentrations 0.4% and 0.04% for complete (95%) recrystallization of soil carbonate. We conclude that microbial and root respiration affecting CO2 concentration in soil is the most important

  4. Inconsistent Changes in Microbial Community Structure and Abundance with Biochar Amendment in Rice Paddy Soils from South China

    NASA Astrophysics Data System (ADS)

    Chen, J.; Qu, J.; Liu, X.; Zheng, J.; Li, L.; Pan, G.

    2012-04-01

    Effects of biochar amendment on soil microbiota had not yet been well understood. We conducted a cross site field study on biochar amendment to rice paddies from south China in 2010. The experiment was performed with four treatments including N fertilization only (C0N), N fertilization plus biochar at 20t/ha (C1N) and at 40t/ha (C2N) as well as a control without N fertilization and biochar (C0N0) consistently with three sites. Biochar was spread at soil surface and incorporated into soil and thoroughly mixed to depth of about 12cm before padding for rice seedling transplantation. Rice production was conducted with conventional water and nutrient management practices adapting to local climate and cultivar conditions. Topsoil samples were collected from each treatment plot across sites for chemical properties and molecular analysis after rice harvest in autumn of 2010. Contents of organic carbon, total N as well as soil microbial biomass carbon were determined with recommended methods. Quantitative real-time PCR coupled with 16S rRNA gene and 18S rRNA gene denaturing gradient gel electrophoresis (DGGE) were respectively employed to trace changes in abundance and structure of bacteria and fungi community with biochar amendment. Increase in microbial biomass carbon (SMBC) was not observed in one site but by 10-20% in other two sites while SOC contents were increased by 25-45% in all sites under biochar treatments. Copy numbers of bacterial genes were different between the sites but no changes with biochar treatment in a single site. However, cluster analysis revealed a more or less decreased similarity of bacterial community to the control (ranging from 75% to 85%) by biochar treatment in a single site. Nevertheless, a number of special bands appeared both in bacterial and fungal DGGE patterns under biochar treatments, though varying with site also. While the fungi copy numbers markedly varied both with sites and with biochar treatments, lower similarity and greater

  5. Quantitative and qualitative trapping of arsines deployed to assess loss of volatile arsenic from paddy soil.

    PubMed

    Mestrot, Adrien; Uroic, M Kalle; Plantevin, Thomas; Islam, Md Rafiqul; Krupp, Eva M; Feldmann, Jörg; Meharg, Andrew A

    2009-11-01

    Arsenic volatilization in the environment is thought to be an important pathway for transfer from terrestrial pools to the atmosphere. However, this phenomenon is not well characterized due to inherent sampling issues in trapping, quantifying and qualifying these arsine gases; including arsine (AsH(3)), monomethyl arsine (MeAsH(2)), dimethyl arsine (Me(2)AsH) and trimethyl arsine (TMAs). To quantify and qualify arsines in air we developed a novel technique based on silver nitrate impregnated silica gel filled tubes. The method was characterized by measuring the recovery of trapped arsines after elution of this chemo-trap with hot boiling diluted nitric acid. Results from three separate experiments, measured by ICP-MS, showed that the method is reproducible and quantitative. Arsine species recovery ranged from 80.1 to 95.6%, with limit of detection as low as 3.8 ng per chemo-trap tube. Moreover, HPLC-ICP-MS analysis of hot boiling water eluted traps showed that the corresponding oxy ions of the arsines were formed with the As-C bonds of the molecule intact, hence, allowing qualification of trapped arsine species. A microcosm study examining volatile arsenic evolution from field contaminated Bangladeshi paddy soils (24.2 mg/kg arsenic) was used to show the application of silver nitrate chemo-trapping approach. Traps were placed on the inlet and the outlet of microcosms containing the soils that were either (cattle derived) manured or not, or flooded or not, in a factorial design. The headspace was purged with air at a flow rate of 12 mL/min. Results showed that as much as 320 ng of arsenic (0.014% of total soil content) could be emitted in a 3 week period for manured and flooded soils and that TMAs was the dominant species evolved, with lesser quantities of Me(2)AsH. No volatile arsenic evolution was observed for nonmanured treatments, and arsine release from the nonflooded, manured treatment was much less than the flooded treatment. PMID:19924955

  6. Burkholderiales participating in pentachlorophenol biodegradation in iron-reducing paddy soil as identified by stable isotope probing.

    PubMed

    Tong, Hui; Hu, Min; Li, Fangbai; Chen, Manjia; Lv, Yahui

    2015-07-01

    As the most prevalent preservative worldwide for many years, pentachlorophenol (PCP) has attracted much interest in the study of biodegradation in soil and aquatic ecosystems. However, the key microorganisms involved in anaerobic degradation are less well understood. Hence, we used DNA-based stable isotope probing (SIP) to identify the PCP-degrading microorganisms in iron-rich paddy soil under anaerobic conditions. (12)C- and (13)C-labeled PCP were almost completely degraded in 30 days under iron-reducing conditions. The results of terminal restriction fragment length polymorphism (T-RFLP) of 16S rRNA genes showed that 197 and 217 bp (HaeIII digests) restriction fragments (T-RFs) were enriched in heavy DNA fractions of (13)C-labeled samples, and the information from 16S rRNA gene clone libraries suggested that the microorganisms corresponding to these T-RF fragments, which increased in relative abundance during incubation, belonged to the order of Burkholderiales, in which 197 and 217 bp were classified as unclassified Burkholderiales and the genus Achromobacter, respectively. The results of the present study indicated that Burkholderiales-affiliated microorganisms were responsible for PCP degradation in anaerobic paddy soil and shed new light on in situ bioremediation in anaerobic PCP contaminated soil. PMID:26051859

  7. SAMPLING AND CALIBRATION REQUIREMENTS FOR OPTICAL REFLECTANCE SOIL PROPERTY SENSORS FOR KOREAN PADDY SOILS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optical diffuse reflectance sensing has potential for rapid and reliable on-site estimation of soil properties. For good results, proper calibration to measured soil properties is required. One issue is whether it is necessary to develop calibrations using samples from the specific area or areas (e....

  8. Influence of Heavy Metals and PCBs Pollution on the Enzyme Activity and Microbial Community of Paddy Soils around an E-Waste Recycling Workshop

    PubMed Central

    Tang, Xianjin; Hashmi, Muhammad Z.; Long, Dongyan; Chen, Litao; Khan, Muhammad I.; Shen, Chaofeng

    2014-01-01

    Due to the emerging environmental issues related to e-waste there is concern about the quality of paddy soils near e-waste workshops. The levels of heavy metals and PCBs and their influence on the enzyme activity and microbial community of paddy soils obtained from the immediate vicinity of an e-waste workshop were investigated in the present study. The results indicated that the heavy metal and PCB pollution did not differ significantly with an increase of the sampling point distances (5 to 30 m). The concentration of Cd (2.16 mg·kg−1) and Cu (69.2 mg·kg−1) were higher, and the PCB pollution was also serious, ranging from 4.9 to 21.6 μg·kg−1. The highest enzyme activity was found for urease compared to phosphatase and catalase, and a fluctuating trend in soil enzyme activity was observed in soils from different sampling sites. The microbial analysis revealed that there was no apparent correlation between the microbial community and the pollutants. However, a slight influence for soil microbial communities could be found based on DGGE, the Shannon index and PCA analysis. The present study suggests that the contamination stress of heavy metals and PCBs might have a slight influence on microbial activity in paddy soils. This study provides the baseline data for enzyme activities and microbial communities in paddy soil under the influence of mixed contamination. PMID:24637907

  9. Quantitative analyses of ribulose-1,5-bisphosphate carboxylase/oxygenase (RubisCO) large-subunit genes (cbbL) in typical paddy soils.

    PubMed

    Xiao, Ke-Qing; Bao, Peng; Bao, Qiong-Li; Jia, Yan; Huang, Fu-Yi; Su, Jian-Qiang; Zhu, Yong-Guan

    2014-01-01

    The Calvin cycle is known to be the major pathway for CO2 fixation, but our current understanding of its occurrence and importance in paddy soils is poor. In this study, the diversity of three ribulose-1,5-bisphosphate carboxylase/oxygenase large-subunit genes (cbbLG, cbbLR, cbbM) was investigated by clone library, T-RFLP, qPCR, and enzyme assay in five paddy soils in China. The cbbLG sequences revealed a relatively low level of diversity and were mostly related to the sequences of species from Thiobacillus. In contrast, highly diverse cbbLR and cbbM sequences were dispersed on the phylogenetic trees, and most of them were distantly related to known sequences, even forming separate clusters. Abundances of three cbbL genes ranged from 10(6) to 10(9) copies g(-1) soil, and cbbLR outnumbered cbbM and cbbLG in all soil samples, indicating that cbbLR may play a more important role than other two cbbL genes. Soil properties significantly influenced cbbL diversity in five paddy soils, of which clay content, C/N ratio, CEC, pH, and SOC correlated well with variations in microbial composition and abundance. In summary, this study provided a comparison of three cbbL genes, advancing our understanding of their role in carbon sequestration and nutrient turnover in the paddy soil. PMID:24024547

  10. Influence of heavy metals and PCBs pollution on the enzyme activity and microbial community of paddy soils around an e-waste recycling workshop.

    PubMed

    Tang, Xianjin; Hashmi, Muhammad Z; Long, Dongyan; Chen, Litao; Khan, Muhammad I; Shen, Chaofeng

    2014-03-01

    Due to the emerging environmental issues related to e-waste there is concern about the quality of paddy soils near e-waste workshops. The levels of heavy metals and PCBs and their influence on the enzyme activity and microbial community of paddy soils obtained from the immediate vicinity of an e-waste workshop were investigated in the present study. The results indicated that the heavy metal and PCB pollution did not differ significantly with an increase of the sampling point distances (5 to 30 m). The concentration of Cd (2.16 mg·kg-1) and Cu (69.2 mg·kg-1) were higher, and the PCB pollution was also serious, ranging from 4.9 to 21.6 μg·kg-1. The highest enzyme activity was found for urease compared to phosphatase and catalase, and a fluctuating trend in soil enzyme activity was observed in soils from different sampling sites. The microbial analysis revealed that there was no apparent correlation between the microbial community and the pollutants. However, a slight influence for soil microbial communities could be found based on DGGE, the Shannon index and PCA analysis. The present study suggests that the contamination stress of heavy metals and PCBs might have a slight influence on microbial activity in paddy soils. This study provides the baseline data for enzyme activities and microbial communities in paddy soil under the influence of mixed contamination. PMID:24637907

  11. Forces and straw cutting performance of double disc furrow opener in no-till paddy soil.

    PubMed

    Ahmad, Fiaz; Weimin, Ding; Qishuo, Ding; Hussain, Mubshar; Jabran, Khawar

    2015-01-01

    Conservation tillage is an energy efficient and low cost tillage system to improve soil environment compared with conventional tillage systems. However, the rice residue management becomes an "impossible to achieve" task due to high soil moisture content at harvest time and the thickness of rice straw. Disc type furrow openers are used for both seed drilling as well as straw cutting during no tillage sowing. A study was conducted to evaluate the draft requirement and straw cutting performances of different sized furrow openers in no-till paddy soil conditions. Double disc furrow opener was tested on an in-field traction bench for three working depths, i.e. 30, 60 and 90 mm, and three forwarding speeds, i.e. 0.1, 0.2 and 0.3 m/s. The draft and vertical forces on the disc were recorded with load cells. These sensors were connected to a data acquisition system developed with hardware and software. The results revealed that the size of the furrow opener, operating depth and the forwarding speed had significant effects (P<0.05) on the horizontal and vertical forces, and the straw cutting performance. Mean values of the draft were 648.9, 737.2 and 784.6 N for the opener with diameters of 330, 450 and 600 mm respectively, and the vertical forces for similar openers were 904.7, 1553.9 and 1620.4 N, respectively. Furthermore, the mean straw cutting efficiencies for the double disc opener with diameters of 330, 450 and 600 mm were 39.36, 78.47 and 65.46%, respectively. The opener with 450 mm diameter provided higher straw cutting efficiency as compared to 600 mm diameter disc, while lowest straw cutting efficiency was observed with 330 mm diameter disc. The 450 mm diameter opener provided the highest straw cutting efficiency (88.6%) at 90 mm working depth and expressed optimum performance compared with other furrow openers. PMID:25822984

  12. Forces and Straw Cutting Performance of Double Disc Furrow Opener in No-Till Paddy Soil

    PubMed Central

    Ahmad, Fiaz; Weimin, Ding; Qishuo, Ding; Hussain, Mubshar; Jabran, Khawar

    2015-01-01

    Conservation tillage is an energy efficient and low cost tillage system to improve soil environment compared with conventional tillage systems. However, the rice residue management becomes an “impossible to achieve” task due to high soil moisture content at harvest time and the thickness of rice straw. Disc type furrow openers are used for both seed drilling as well as straw cutting during no tillage sowing. A study was conducted to evaluate the draft requirement and straw cutting performances of different sized furrow openers in no-till paddy soil conditions. Double disc furrow opener was tested on an in-field traction bench for three working depths, i.e. 30, 60 and 90 mm, and three forwarding speeds, i.e. 0.1, 0.2 and 0.3 m/s. The draft and vertical forces on the disc were recorded with load cells. These sensors were connected to a data acquisition system developed with hardware and software. The results revealed that the size of the furrow opener, operating depth and the forwarding speed had significant effects (P<0.05) on the horizontal and vertical forces, and the straw cutting performance. Mean values of the draft were 648.9, 737.2 and 784.6 N for the opener with diameters of 330, 450 and 600 mm respectively, and the vertical forces for similar openers were 904.7, 1553.9 and 1620.4 N, respectively. Furthermore, the mean straw cutting efficiencies for the double disc opener with diameters of 330, 450 and 600 mm were 39.36, 78.47 and 65.46%, respectively. The opener with 450 mm diameter provided higher straw cutting efficiency as compared to 600 mm diameter disc, while lowest straw cutting efficiency was observed with 330 mm diameter disc. The 450 mm diameter opener provided the highest straw cutting efficiency (88.6%) at 90 mm working depth and expressed optimum performance compared with other furrow openers. PMID:25822984

  13. Genome sequence of the anaerobic bacterium Bacillus sp. strain ZYK, a selenite and nitrate reducer from paddy soil.

    PubMed

    Bao, Peng; Su, Jian-Qiang; Hu, Zheng-Yi; Häggblom, Max M; Zhu, Yong-Guan

    2014-06-15

    Bacillus sp. strain ZYK, a member of the phylum Firmicutes, is of interest for its ability to reduce nitrate and selenite and for its resistance to arsenic under anaerobic conditions. Here we describe some key features of this organism, together with the complete genome sequence and annotation. The 3,575,797 bp long chromosome with its 3,454 protein-coding and 70 RNA genes, and the information gained from its sequence will be relevant to the elucidation of microbially-mediated transformations of nitrogen, selenium and arsenic in paddy soil. PMID:25197451

  14. Genome sequence of the anaerobic bacterium Bacillus sp. strain ZYK, a selenite and nitrate reducer from paddy soil

    PubMed Central

    Bao, Peng; Su, Jian-Qiang; Hu, Zheng-Yi; Häggblom, Max M.

    2014-01-01

    Bacillus sp. strain ZYK, a member of the phylum Firmicutes, is of interest for its ability to reduce nitrate and selenite and for its resistance to arsenic under anaerobic conditions. Here we describe some key features of this organism, together with the complete genome sequence and annotation. The 3,575,797 bp long chromosome with its 3,454 protein-coding and 70 RNA genes, and the information gained from its sequence will be relevant to the elucidation of microbially-mediated transformations of nitrogen, selenium and arsenic in paddy soil. PMID:25197451

  15. [Effect of sulfur on the species of Fe and As under redox condition in paddy soil].

    PubMed

    Tang, Bing-Pei; Yang, Shi-Jie; Wang, Dai-Zhang; Rao, Wei; Zhang, Ya-Nan; Wang, Dan; Zhu, Yun-Ji

    2014-10-01

    Redox conditions of the polluted paddy soil with exogenous As were simulated by redox reaction apparatus after flowing N2 and O2 applied with different forms of inorganic sulfur(CK-S0, elemental sulfur-S1 and sulfate-S2). Results showed that redox potential (Eh) was about -100 - -200 mV and the pH 7.0-8.0 and the pe + pH 4-7 in soil solution when flowed N2, and Eh about 200 mV and the pH 6.5-7.5 and pe + pH 9-12 when continuously flowed O2. Concentrations of the dissolved Fe in soil solution were in 1.2-1.6 mg x L(-1) either flowed N2 or O2, and the order of Fe concentrations was AsS0 treatment > AsS1 treatment > AsS2 treatment. Amounts of soil Fe oxide by HCl extraction from different treatments were 5 g · kg(-1) lower than the original soil [(21.4 ± 0.3) g · kg(-1)] when flowed N2, and it was in favor of the transformation of crystal Fe into amorphous iron and Fe2+. Activity of Fe oxides from different treatments increased comparing to that of the original soil (46. 8%), and the order of activity of Fe oxides was AsS2 treatment (49.4%) < AsS1 treatment (60%). Fe2+ in solution and FeS were oxidized into Fe3+, and hydrolysis of Fe3+ was produced into Fe(OH)3 precipitation when flowed O2. It increased the contents of acid-soluble and crystal Fe oxide, and the order of activity of Fe oxides was AsS1 (41.2%) treatment > AsS2 (36.1%) treatment. Concentrations of As in soil solution were in the order of AsS0 [(1.13 ± 0.04) mg · L(-1)] > AsS1 [(0.89 ± 0.01) mg L(- 1)] > AsS2 [ (0.77 ± 0.04 )mg · L(-1)] when flowed N2 and was AsS1 [(0.77 ± 0.01) mg · L(-1)] > AsS0 [(0.20 ± 0.09 ) mg · L(-1)] > AsS2 [(0.09 ± 0.01) mg · L(-1)] when flowed O2. The proportions of arsenic fractions followed the order of the residual phases (34.9%-41.4%) ≈ specifically-sorbed (37.4%-39.5%) > well-crystallized hydrous oxides of Fe/Mn (23.3%-25.6%) > non-specifically sorbed (2.4%-3.3%) > amorphous hydrous oxides of Fe/Mn (0.5%-0.8%) when flowed N2, and was the residual phases (30

  16. Partitioning of arsenic in soil-crop systems irrigated using groundwater: a case study of rice paddy soils in southwestern Taiwan.

    PubMed

    Hsu, Wen-Ming; Hsi, Hsing-Cheng; Huang, You-Tuan; Liao, Chien-Sen; Hseu, Zeng-Yei

    2012-02-01

    The accumulation of As in rice due to groundwater irrigation in paddy fields represents a serious health hazard in South and Southeast Asia. In Taiwan, the fate of As in long-term irrigated paddy fields is poorly understood. Groundwater, surface soil, and rice samples were collected from a paddy field that was irrigated with As-containing groundwater in southwestern Taiwan. The purpose of this study is to elucidate the source and sink of As in the paddy field by comparing the As fractions in the soils that were obtained by a sequential extraction procedure (SEP) with the As uptake of rice. The risks associated with eating rice from the field can thus be better understood. The concentration of As in groundwater varied with time throughout the growing seasons of rice, but always exceeded the permitted maximum (10 μg L(-1)) for drinking water by the WHO. The As concentration increased with the concentration of Fe in the groundwater, supporting the claim that a large amount of As was concentrated in the Fe flocs collected from the internal wall of the groundwater pump. The results of the SEP revealed that As bound with amorphous and crystalline hydrous oxides exhibited high availability in the soils. The root of rice accumulated the largest amount of As, followed by the straw, husk, and grain. Although the As concentration in the rice grain was less than 1.0 mg kg(-1), the estimated intake level was close to the maximum tolerable daily intake of As, as specified by the WHO. PMID:22094052

  17. The influence of continuous rice cultivation and different waterlogging periods on morphology, clay mineralogy, Eh, pH and K in paddy soils.

    PubMed

    Bahmanyar, M A

    2007-09-01

    The effect of different rice cultivation periods on the properties of selected soils in alluvial plain were studied in Mazandaran province (north of Iran) in 2004. Soils were sampled form 0, 6, 16, 26 and over 40 years rice cultivation fields. In each treatment three soil profiles and six nearby auger holes were studied. The present study results indicated that continuous rice cultivation have changed soil moisture regime from xeric to aquic, soil color from brown to grayish, surface horizons from mollic to ochric epipedon and soil structure changed from granular or blocky to massive. Therefore, the soil order has changed from Mollisols to Inceptisols. No illuviation and eluviation of clay minerals occurred as a consequence of rice cultivation. X-ray diffraction analysis showed that clay minerals in non-rice cultivated field were illite, vermiculite, montmorillonite, kaolinite and chlorite, but in rice field were illite, montmorillonite, kaolinite and chlorite, respectively. In contrast of montmorillonite, the amount of illite and vermiculite have been decreased by increasing periods of rice cultivation. The pH values of the saturated soil surface in six weeks past plantation have shifted toward neutrality. While Eh value of non-paddy soils were about +90 mv, surface horizons of paddy soils at field conditions had Eh value about +40, -12, -84, -122 mv, respectively. The amounts of organic matter and available Fe, Mn, Zn and Cu were increased whereas available K was decreased in paddy soils. PMID:19090186

  18. Effect of rice straw application on microbial community and activity in paddy soil under different water status.

    PubMed

    Pan, Fuxia; Li, Yaying; Chapman, Stephen James; Yao, Huaiying

    2016-03-01

    Rice straw application and flooding are common practices in rice production, both of which can induce changes in the microbial community. This study used soil microcosms to investigate the impact of water status (saturated and nonsaturated) and straw application (10 g kg(-1) soil) on soil microbial composition (phospholipid fatty acid analysis) and activity (MicroResp(™) method). Straw application significantly increased total PLFA amount and individual PLFA components independent of soil moisture level. The amount of soil fungal PLFA was less than Gram-negative, Gram-positive, and actinomycete PLFA, except the drained treatment with rice straw application, which had higher fungal PLFA than actinomycete PLFA at the initial incubation stage. Straw amendment and waterlogging had different effects on microbial community structure and substrate-induced pattern. PLFA profiles were primarily influenced by straw application, whereas soil water status had the greater influence on microbial respiration. Of the variation in PLFA and respiration data, straw accounted for 30.1 and 16.7 %, while soil water status explained 7.5 and 29.1 %, respectively. Our results suggest that (1) the size of microbial communities in paddy soil is more limited by carbon substrate availability rather than by the anaerobic conditions due to waterlogging and (2) that soil water status is more important as a control of fungal growth and microbial community activity. PMID:26596827

  19. Estimating CH4 emission from paddy managed soils in southern guinea savanna zone of Nigeria using an integrated approach

    NASA Astrophysics Data System (ADS)

    Akpeokhai, Agatha; Menz, Gunter; Thonfeld, Frank; Akinluyi, Francis

    2016-04-01

    ESTIMATING CH4 EMISSION FROM PADDY MANAGED SOILS IN SOUTHERN GUINEA SAVANNA ZONE OF NIGERIA USING AN INTEGRATED APPROACH Akpeokhai Agatha 1, Menz Gunter 1, Thonfeld Frank 1, Akinluyi Francis 2 1 Remote Sensing Research Group (RSRG), Geography Institute, University of Bonn, Germany. 2 Department Remote Sensing and Geo-Science Information System, School of Earth and Mineral Science, Federal University of Technology, Akure Nigeria. Methane is one of the most important greenhouse gases as it has the second greatest climate forcing potential. Paddy fields have been identified to be sources of methane and Nigerian paddies are not left out. In Nigeria, the guinea savanna region is regarded as the bread basket of the nation and this area is one of the major rice producing regions in Nigeria. Its location in the food basket region of the country makes this part a very important study site. However, since Nigerian paddies contribute to methane emission by how much do these paddies contribute to the emissions? Also, so far, there limited studies on methane from rice fields in West Africa thus making this study a very important start off point. To answer this huge question, methane emission will be estimated using an integrated approach in the North Central part of Nigeria. Land use change cultivated to rice was analysed using Remote sensing techniques to determine the changes in land cultivated to rice. Methane emission from these identified rice fields will be estimated using the IPCC Tier 1 set of equations. First relevant indices (Normalized Differential Moisture Index, Normalized Differential Wetness Index and Rice Growth Vegetation Index) were generated to aid classification of rice fields using LANDSAT data from the USGS. Next the LANDSAT datasets were analyzed for land use change cultivated to rice from 1990 to 2014 to generate rice field maps. ERDAS Imagine, ARCGIS and ENVI tools were used to meet these spatial needs. Methane emissions from this region will be

  20. Bacterial Populations Colonizing and Degrading Rice Straw in Anoxic Paddy Soil

    PubMed Central

    Weber, Sabine; Stubner, Stephan; Conrad, Ralf

    2001-01-01

    Rice straw is a major substrate for the production of methane, a greenhouse gas, in flooded rice fields. The bacterial community degrading rice straw under anoxic conditions was investigated with molecular methods. Rice straw was incubated in paddy soil anaerobically for 71 days. Denaturing gradient gel electrophoresis (DGGE) of the amplified bacterial 16S rRNA genes showed that the composition of the bacterial community changed during the first 15 days but then was stable until the end of incubation. Fifteen DGGE bands with different signal intensities were excised, cloned, and sequenced. In addition, DNA was extracted from straw incubated for 1 and 29 days and the bacterial 16S rRNA genes were amplified and cloned. From these clone libraries 16 clones with different electrophoretic mobilities on a DGGE gel were sequenced. From a total of 31 clones, 20 belonged to different phylogenetic clusters of the clostridia, i.e., clostridial clusters I (14 clones), III (1 clone), IV (1 clone), and XIVa (4 clones). One clone fell also within the clostridia but could not be affiliated to one of the clostridial clusters. Ten clones grouped closely with the genera Bacillus (3 clones), Nitrosospira (1 clone), Fluoribacter (1 clones), and Acidobacterium (2 clones) and with clone sequences previously obtained from rice field soil (3 clones). The relative abundances of various phylogenetic groups in the rice straw-colonizing community were determined by fluorescence in situ hybridization (FISH). Bacteria were detached from the incubated rice straw with an efficiency of about 80 to 90%, as determined by dot blot hybridization of 16S rRNA in extract and residue. The number of active (i.e., a sufficient number of ribosomes) Bacteria detected with a general eubacterial probe (Eub338) after 8 days of incubation was 61% of the total cell counts. This percentage decreased to 17% after 29 days of incubation. Most (55%) of the active cells on day 8 belonged to the genus Clostridium, mainly

  1. Carbon decomposition process of the residual biomass in the paddy soil of a single-crop rice field

    NASA Astrophysics Data System (ADS)

    Okada, K.; Iwata, T.

    2014-12-01

    In cultivated fields, residual organic matter is plowed into soil after harvest and decaying in fallow season. Greenhouse gases such as CO2 and CH4 is generated by the decomposition of the substantial organic matter and released into the atmosphere. In some fields, open burning is carried out by tradition, when carbon in residual matter is released into atmosphere as CO2. However, burning effect on carbon budget between crop lands and atmosphere is not entirely considered yet. In this study, coarse organic matter (COM) in paddy soil of a single-crop rice field was sampled on regular intervals between January, 2011 and August, 2014 The amount of carbon release from residual matter was estimated by analyzing of the variations in carbon content of COM. Effects of soil temperature (Ts) and soil water content (SWC) at the paddy field on the rate of carbon decomposition was investigated. Though decreasing rate of COM was much smaller in winter season, it is accelerated at the warming season between April and June every year. Decomposition was resisted for next rice cultivated season despite of highest soil temperature. In addition, the observational field was divided into two areas, and three time open burning experiments were conducted in November, 2011, 2012, and 2013. In each year, three sampling surveys, or plants before harvest and residuals before and after the burning experiment, were done. From these surveys, it is suggested that about 48±2% of carbon contents of above-ground plant was yield out as grain by harvest, and about 27±2% of carbon emitted as CO2 by burning. Carbon content of residuals plowed into soil after the harvest was estimated 293±1 and 220±36gC/m2 in no-burned and burned area, respectively, based on three-years average. It is estimated that 70 and 60% of the first input amount of COM was decomposed after a year in no-burned and burned area, respectively.

  2. H2-Producing Bacterial Community during Rice Straw Decomposition in Paddy Field Soil: Estimation by an Analysis of [FeFe]-Hydrogenase Gene Transcripts

    PubMed Central

    Baba, Ryuko; Asakawa, Susumu; Watanabe, Takeshi

    2016-01-01

    The transcription patterns of [FeFe]-hydrogenase genes (hydA), which encode the enzymes responsible for H2 production, were investigated during rice straw decomposition in paddy soil using molecular biological techniques. Paddy soil amended with and without rice straw was incubated under anoxic conditions. RNA was extracted from the soil, and three clone libraries of hydA were constructed using RNAs obtained from samples in the initial phase of rice straw decomposition (day 1 with rice straw), methanogenic phase of rice straw decomposition (day 14 with rice straw), and under a non-amended condition (day 14 without rice straw). hydA genes related to Proteobacteria, Firmicutes, Bacteroidetes, Chloroflexi, and Thermotogae were mainly transcribed in paddy soil samples; however, their proportions markedly differed among the libraries. Deltaproteobacteria-related hydA genes were predominantly transcribed on day 1 with rice straw, while various types of hydA genes related to several phyla were transcribed on day 14 with rice straw. Although the diversity of transcribed hydA was significantly higher in the library on day 14 with rice straw than the other two libraries, the composition of hydA transcripts in the library was similar to that in the library on day 14 without rice straw. These results indicate that the composition of active H2 producers and/or H2 metabolic patterns dynamically change during rice straw decomposition in paddy soil. PMID:27319579

  3. Risk Assessment of Heavy Metals Contamination in Paddy Soil, Plants, and Grains (Oryza sativa L.) at the East Coast of India

    PubMed Central

    Satpathy, Deepmala; Reddy, M. Vikram; Dhal, Soumya Prakash

    2014-01-01

    Heavy metals known to be accumulated in plants adversely affect human health. This study aims to assess the effects of agrochemicals especially chemical fertilizers applied in paddy fields, which release potential toxic heavy metals into soil. Those heavy metals get accumulated in different parts of paddy plant (Oryza sativa L.) including the grains. Concentrations of nonessential toxic heavy metals (Cd, Cr, and Pb) and the micronutrients (Cu, Mn, and Zn) were measured in the paddy field soil and plant parts. Mn and Cd are found to be accumulated more in shoot than in root. The metal transfer factors from soil to rice plant were significant for Pb, Cd, Cu, Cr, Mn, and Zn. The ranking order of bioaccumulation factor (BAF) for heavy metals was Zn > Mn > Cd > Cu > Cr > Pb indicating that the accumulation of micronutrients was more than that of nonessential toxic heavy metals. The concentrations of heavy metals were found to be higher in paddy field soils than that of the nearby control soil but below permissible limits. The higher Health Index (HI) values of rice consuming adults (1.561) and children (1.360) suggest their adverse health effects in the near future. PMID:24995308

  4. Fate of organic carbon in paddy soils - results of Alisol and Andosol incubation with 13C marker

    NASA Astrophysics Data System (ADS)

    Winkler, Pauline; Cerli, Chiara; Fiedler, Sabine; Woche, Susanne; Rahayu Utami, Sri; Jahn, Reinhold; Kalbitz, Karsten; Kaiser, Klaus

    2016-04-01

    For a better understanding of organic carbon (OC) decomposition in paddy soils an incubation experiment was performed. Two soil types with contrasting mineralogy (Alisol and Andosol) were exposed to 8 anoxic‒oxic cycles over 1 year. Soils received rice straw marked with 13C (228 ‰) at the beginning of each cycle. A second set of samples without straw addition was used as control. Headspaces of the incubation vessels were regularly analysed for CO2 and CH4. In soil solutions, redox potential, pH, dissolved organic C (DOC), and Fe2+ were measured after each anoxic and each oxic phase. Soils were fractionated by density at the end of the experiment and the different fractions were isotopically analysed. Samples of genuine paddy soils that developed from the test soils were used as reference. During anoxic cycles, soils receiving rice straw released large amounts of CO2 and CH4, indicating strong microbial activity. Consequently, Eh values dropped and pH as well as Fe2+ concentrations increased. Concentrations of DOC were relatively small, indicating either strong consumption and/or strong retention of dissolved organic compounds. During oxic cycles, concentrations of dissolved Fe dropped in both soils while DOC concentrations remained constant in the Alisol and decreased in the Andosol. Density fractionation revealed increased contents of mineral associated OC for the Andosol incubated with straw addition as compared to the parent soil. No changes were found for the Alisol. However, the mineral-associated OC fraction of both soil types contained 13C of the added straw. Hence, fresh organic matter is incorporated while part of the older organic matter has been released or mineralized. The increase in the Andosol might be due to effective binding of fresh OC to minerals and/or stronger retention/preservation of older OC. Both could be explained by the more reactive mineralogy of the Andosol than of the Alisol. XPS analyses of the soils are currently performed and

  5. Antimony (Sb) and arsenic (As) in Sb mining impacted paddy soil from Xikuangshan, China: differences in mechanisms controlling soil sequestration and uptake in rice.

    PubMed

    Okkenhaug, Gudny; Zhu, Yong-Guan; He, Junwen; Li, Xi; Luo, Lei; Mulder, Jan

    2012-03-20

    Foods produced on soils impacted by antimony (Sb) mining activities are a potential health risk due to plant uptake of the contaminant metalloids (Sb) and arsenic (As). Here we report for the first time the chemical speciation of Sb in soil and porewater of flooded paddy soil, impacted by active Sb mining, and its effect on uptake and speciation in rice plants (Oryza sativa L. cv Jiahua). Results are compared with behavior and uptake of As. Pot experiments were conducted under controlled conditions in a climate chamber over a period of 50 days. In pots without rice plants, flooding increased both the concentration of dissolved Sb (up to ca. 2000 μg L(-1)) and As (up to ca. 1500 μg L(-1)). When rice was present, Fe plaque developing on rice roots acted as a scavenger for both As and Sb, whereby the concentration of As, but not Sb, in porewater decreased substantially. Dissolved Sb in porewater, which occurred mainly as Sb(V), correlated with Ca, indicating a solubility governed by Ca antimonate. No significant differences in bioaccumulation factor and translocation factor between Sb and As were observed. Greater relative concentration of Sb(V) was found in rice shoots compared to rice root and porewater, indicating either a preferred uptake of Sb(V) or possibly an oxidation of Sb(III) to Sb(V) in shoots. Adding soil amendments (olivine, hematite) to the paddy soil had no effect on Sb and As concentrations in porewater. PMID:22309044

  6. A humic substance analogue AQDS stimulates Geobacter sp. abundance and enhances pentachlorophenol transformation in a paddy soil.

    PubMed

    Chen, Manjia; Tong, Hui; Liu, Chengshuai; Chen, Dandan; Li, Fangbai; Qiao, Jiangtao

    2016-10-01

    Soil humic substances can be used as redox mediators in accelerating the biotransformation of organic pollutants, and humus-respiring bacteria are widely distributed in soils. However, the impact of humic substances on the soil microbial community during the biotransformation of organic pollutants is expected to be crucial while remains to be unclear. In this study, the biostimulation of indigenous microbial communities and the consequent effects on anaerobic transformation of pentachlorophenol (PCP) by a model humic substance, anthraquinone-2,6-disulfonate (AQDS), were systematically investigated in a paddy soil. The addition of AQDS was observed to increase the production of HCl-extractable Fe(II) and enhance the PCP transformation rates consequently. The pseudo-first-order rate constants of the PCP transformation showed a positive exponential relationship with the AQDS dosage. The terminal restriction fragment length polymorphism (T-RFLP) results indicated the substantial effect of added AQDS on soil microbial community. The enhanced abundance of Geobacter sp. was disclosed to be most critical for accelerated PCP transformation when with AQDS, in which Geobacter sp. functioned for promoting the generation of active Fe(II) and consequently enhancing the PCP transformation rates. The transformation rates of PCP were exponentially correlated with the abundance of Geobacter sp. positively. The findings are expected to improve the understanding of diversity and ubiquity of microorganisms in humic substances-rich soils for accelerating the transformations of soil chlorinated pollutants. PMID:27372263

  7. Efficiency evaluation for remediating paddy soil contaminated with cadmium and arsenic using water management, variety screening and foliage dressing technologies.

    PubMed

    Liao, Guojian; Wu, Qianhua; Feng, Renwei; Guo, Junkang; Wang, Ruigang; Xu, Yingming; Ding, Yongzhen; Fan, Zhilian; Mo, Liangyu

    2016-04-01

    Paddy soils in many regions of China have been seriously polluted by multiple heavy metals or metalloids, such as arsenic (As), cadmium (Cd) and lead (Pb). In order to ensure the safety of food and take full advantage of the limited farmland resources of China, exploring an effective technology to repair contaminated soils is urgent and necessary. In this study, three technologies were employed, including variety screening, water management and foliage dressing, to assess their abilities to reduce the accumulation of Cd and As in the grains of different rice varieties, and meanwhile monitor the related yields. The results of variety screening under insufficient field drying condition showed that the As and Cd contents in the grains of only four varieties [Fengliangyouxiang 1 (P6), Zhongzheyou 8 (P7), Guangliangyou 1128 (P10), Y-liangyou 696 (P11)] did not exceed their individual national standard. P6 gained a relatively high grain yield but accumulated less As and Cd in the grains despite of the relatively high As and Cd concentrations in the rhizosphere soil. However, long-playing field drying in water management trial significantly increased Cd but decreased As content in the grains of all tested three varieties including P6, suggesting an important role of water supply in controlling the accumulation of grain As and Cd. Selenium (Se) showed a stronger ability than silicon (Si) to reduce As and Cd accumulation in the grains of Fengliangyou 4 (P2) and Teyou 524 (P13), and keep the yields. The results of this study suggest that combined application of water management and foliage dressing may be an efficient way to control As and Cd accumulation in the grains of paddy rice exposing to As- and Cd-contaminated soils. PMID:26807822

  8. Effect of long-term paddy-upland yearly rotations on rice (Oryza sativa) yield, soil properties, and bacteria community diversity.

    PubMed

    Chen, Song; Zheng, Xi; Wang, Dangying; Chen, Liping; Xu, Chunmei; Zhang, Xiufu

    2012-01-01

    A 10-year-long field trial (between 2001 and 2010) was conducted to investigate the effect of paddy-upland rotation on rice yield, soil properties, and bacteria community diversity. Six types of paddy-upland crop rotations were evaluated: rice-fallow (control; CK), rice-rye grass (RR), rice-potato with rice straw mulches (RP), rice-rapeseed with straw incorporated into soil at flowering (ROF), rice-rapeseed incorporated in soil after harvest (ROM), and rice-Chinese milk vetch (RC). Analysis of terminal restriction fragment length polymorphism (T-RFLP) was used to determine microbial diversity among rotations. Rice yield increased for upland crops planted during the winter. RC had the highest average yield of 7.74 t/ha, followed by RR, RP, ROM, and ROF. Soil quality differences among rotations were found. RC and RP improved the soil mean weight diameter (MWD), which suggested that rice rotated with milk vetch and potato might improve the paddy soil structure. Improved total nitrogen (TN) and soil organic matter (SOM) were also found in RC and RP. The positive relationship between yield and TN/SOM might provide evidence for the effect of RC rotation on rice yield. A strong time dependency of soil bacterial community diversity was also found. PMID:22919301

  9. Impact of S fertilizers on pore-water Cu dynamics and transformation in a contaminated paddy soil with various flooding periods.

    PubMed

    Yang, Jianjun; Zhu, Shenhai; Zheng, Cuiqing; Sun, Lijuan; Liu, Jin; Shi, Jiyan

    2015-04-01

    Impact of S fertilization on Cu mobility and transformation in contaminated paddy soils has been little reported. In this study, we investigated the dynamics and transformation of dissolved and colloidal Cu in the pore water of a contaminated paddy soil after applying ammonium sulphate (AS) and sulfur coated urea (SCU) with various flooding periods (1, 7 and 60 days). Compared to the control soil, the AS-treated soil released more colloidal and dissolved Cu over the entire flooding period, while the SCU-treated soil had lower colloidal Cu after 7-day flooding but higher colloidal and dissolved Cu after 60-day flooding. Microscopic X-ray fluorescence (μ-XRF) analysis found a close relationship between Fe and Cu distribution on soil colloids after 60-day flooding, implying the formation of colloidal Fe/Cu sulphide coprecipitates. Cu K-edge X-ray absorption near-edge structure (XANES) spectroscopy directly revealed the transformation of outer-sphere complexed Cu(II) species to Cu(II) sulphide and reduced Cu2O in the colloids of S-treated soils after 60-day flooding. These results demonstrated the great influence of S fertilization on pore-water Cu mobility by forming Cu sulphide under flooding conditions, which facilitated our understanding and control of Cu loss in contaminated paddy soils under S fertilization. PMID:25603292

  10. The Potential of Soft Soil Improvement Through a Coupled Technique Between Electro Kinetic and Alkaline Activation of Soft Soil

    NASA Astrophysics Data System (ADS)

    Ahmed, G. E.; Ismail, H. B.; Huat, B. K.; Afshin, A.; Azhar, A. T. S.

    2016-07-01

    Soil stabilization techniques have been in development for decades with different rates of success. Alkaline activation of soft soil is one of those techniques that has proved to deliver some of the best shear strength values with minor drawbacks in comparison with conventional soil stabilization methods. However, environmental considerations have not been taken into account, as major mineral glassy phase activators are poisoning alkaline solutions, such as sodium-, potassium-hydroxide, and sodium-, potassium-silicate, which poses serious hazards to man and environment. This paper addresses the ways of discarding the involvement of the aforementioned alkaline solutions in soft soil stabilization by investigating the potential of a coupled electro kinetic alkaline activation technique for soft soil strengthening, through which the provision of alkaline pH is governed by electro kinetic potential. Uncertainties in regard to the dissolution of aluminosilicate as well as the dominance of acidic front are challenges that need to be overcome.

  11. Positive feedback of crop residue incorporation on dissolved organic carbon contents under anaerobic conditions in temperate rice paddy soils

    NASA Astrophysics Data System (ADS)

    Said-Pullicino, Daniel; Sodano, Marcella; Bertora, Chiara; Lerda, Cristina; Sacco, Dario; Celi, Luisella

    2016-04-01

    Rice paddy soils are generally characterized by large concentrations and fluxes of DOC in comparison to other ecosystems. Our recent studies have shown that the combination of relatively high pore-water DOC concentrations under anoxic soil conditions (>10-20 mg C l‑1) and important percolation fluxes of water during field flooding may contribute significant organic C inputs into the subsoil (18-51 g C m‑2) over the cropping season. Crop residues incorporated into the soil after harvest represent the main input of organic C into paddy soils, returning about 200-300 g C m‑2 y‑1 in single-cropped rice paddies. The anaerobic decomposition of these residues may supply important amounts of DOC to soil pore waters. Moreover, the supply of electron donors with the input of residue-derived labile OM may further increase DOC contents by stimulating the microbially-catalyzed reductive dissolution of Fe and Mn oxyhydroxides under anoxic conditions, and release of DOC previously stabilized on the mineral matrix (i.e. positive feedback). This could have important implications on organic C inputs into the subsoil as well as substrate availability for methane production. We therefore hypothesized that crop residue management practices that influence the amount of labile organic matter present in the soil at the time of field flooding may strongly influence soil solution DOC concentrations as well as the positive feedback on the release of soil-derived DOC. We tested this hypothesis at field-scale by evaluating variations in the contents and quality of DOC above and beneath the plough pan over the cropping season as a function of crop residue management practices involving: tillage and crop residue incorporation in spring (SPR), tillage and crop residue incorporation in spring, dry seeding and 1 month delayed flooding (DRY), tillage and crop residue incorporation in autumn (AUT), and straw removal after harvest and tillage in spring (REM). Moreover, we linked changes in DOC

  12. Effect of Elevated CO2 Concentration, Elevated Temperature and No Nitrogen Fertilization on Methanogenic Archaeal and Methane-Oxidizing Bacterial Community Structures in Paddy Soil

    PubMed Central

    Liu, Dongyan; Tago, Kanako; Hayatsu, Masahito; Tokida, Takeshi; Sakai, Hidemitsu; Nakamura, Hirofumi; Usui, Yasuhiro; Hasegawa, Toshihiro; Asakawa, Susumu

    2016-01-01

    Elevated concentrations of atmospheric CO2 ([CO2]) enhance the production and emission of methane in paddy fields. In the present study, the effects of elevated [CO2], elevated temperature (ET), and no nitrogen fertilization (LN) on methanogenic archaeal and methane-oxidizing bacterial community structures in a free-air CO2 enrichment (FACE) experimental paddy field were investigated by PCR-DGGE and real-time quantitative PCR. Soil samples were collected from the upper and lower soil layers at the rice panicle initiation (PI) and mid-ripening (MR) stages. The composition of the methanogenic archaeal community in the upper and lower soil layers was not markedly affected by the elevated [CO2], ET, or LN condition. The abundance of the methanogenic archaeal community in the upper and lower soil layers was also not affected by elevated [CO2] or ET, but was significantly increased at the rice PI stage and significantly decreased by LN in the lower soil layer. In contrast, the composition of the methane-oxidizing bacterial community was affected by rice-growing stages in the upper soil layer. The abundance of methane-oxidizing bacteria was significantly decreased by elevated [CO2] and LN in both soil layers at the rice MR stage and by ET in the upper soil layer. The ratio of mcrA/pmoA genes correlated with methane emission from ambient and FACE paddy plots at the PI stage. These results indicate that the decrease observed in the abundance of methane-oxidizing bacteria was related to increased methane emission from the paddy field under the elevated [CO2], ET, and LN conditions. PMID:27600710

  13. [Impacts of different alkaline soil on canopy spectral characteristics of overlying vegetation].

    PubMed

    Jia, Ke-Li; Zhang, Jun-Hua

    2014-03-01

    The relationship between alkalinity and pH of the soil, reflectance spectra and red-edge parameters of the sunflower canopy in different growth periods under different alkalinity soil were analyzed, respectively. The results showed that the spectral reflectance of the sunflower canopy in different stage under different alkalinity soil is the same as the spectral reflectance characters of the other greenery canopy. Along with the advancement of the sunflower growth period, sunflower canopy spectral reflectance increases gradually at different stages, the spectral reflectance is higher at flowering stage than 7-leaf stage and budding stage, and there exists a high reflection peak at 809nm at flowering period. At the same time, the spectral reflectance is affected by salinity-alkalinity stress at different stages, in the near infrared shortwave band, the spectral reflectance of the sunflower canopy in different stage increases with the decreases in soil alkalinity. When the derivatives are applied to determine the wavelength of the red-edge, there is a shift phenomenon of the red edge. The red edges were at 702-720 nm during every growth period of the sunflower. The "blue shift" phenomenon is also emerged for red edge position and red edge sloped with the increase in the soil alkalinity. Conversely, at the same growth periods, the red edge positions and red edge slope move to longer wave bands with the decrease in soil alkalinity. There is a "red shift" phenomenon before flowering period and "blue shift" phenomenon after flowering period for the red edge position and red edge slope of canopy spectrum at the same soil alkalinity. Respectively. The red edges at different growth stages of the sunflower show very significant positive correlation and quadratic polynomial to alkalinity and pH of the soil. Therefore, we thought used the red edge features of greenery could indicate the soil alkalization degree, it providing scientific basis for monitoring soil alkalization

  14. [Effects of wheat-straw returning into paddy soil on dissolved organic carbon contents and rice grain yield].

    PubMed

    Xu, Ke; Liu, Meng; Chen, Jing-du; Gu, Hai-yan; Dai, Qi-gen; Ma, Ke-qiang; Jiang, Feng; He, Li

    2015-02-01

    A tank experiment using conventional rice cultivar Nanjing 44 as experimental material was conducted at the Experimental Farm of Yangzhou University to investigate the dynamics of wheat straw decomposition rate and the amount of carbon release in clay and sandy soils, as well as its effects on the content of dissolved organic carbon (DOC) and rice yield. The two rates of wheat straw returning were 0 and 6000 kg · hm(-2), and three N application levels were 0, 225, 300 kg · hm(-2). The results showed that, the rate of wheat straw decomposition and the amount of carbon release in clay and sandy soils were highest during the initial 30 days after wheat straw returning, and then slowed down after, which could be promoted by a higher level of nitrogen application. The rate of wheat straw decomposition and the amount of carbon release in clay soil were higher than that in sandy soil. The DOC content in soil increased gradually with wheat straw returning into paddy soil and at the twenty-fifth day, and then decreased gradually to a stable value. The DOC content at the soil depth of 15 cm was significantly increased by wheat straw returning, but not at the soil depth of 30 cm and 45 cm. It was concluded that wheat straw returning increased the DOC content in the soil depth of 0-15 cm mainly. N application decreased the DOC content and there was no difference between the two N application levels. Straw returning decreased the number of tillers in the early growth period, resulted in significantly reduced panicles per unit area, but increased spikelets per panicle, filled-grain percentages, 1000-grain mass, and then enhanced grain yield. PMID:26094457

  15. Nitrate isotopes illuminate the black box of paddy soil biogeochemistry: water and carbon management control nitrogen sources and sinks

    NASA Astrophysics Data System (ADS)

    Wells, N. S.; Clough, T. J.; Johnson-Beebout, S. E.; Buresh, R. J.

    2010-12-01

    Accurate prediction of the available nitrogen (N) pool in submerged paddy soils is needed in order to produce rice, one of the world’s most essential crops, in an economically and environmentally sustainable manner. By applying emerging nitrate dual-isotope (δ15N- δ18O- NO3-) techniques to paddy systems, we were able to obtain a unique process-level quantification of the synergistic impacts of carbon (C) and water management on N availability. Soil and water samples were collected from fallow experimental plots, with or without organic C amendments, that were maintained under 1 of 3 different hydrologic regimens: continuously submerged, water excluded, or alternate wetting and drying. In continuously submerged soils the δ15N-NO3- : δ18O-NO3- signal of denitrification was not present, indicating that there was no N attenuation. Biological nitrogen fixation (BNF) was the dominant factor in defining the available N pool under these conditions, with δ15N-NO3- approaching atmospheric levels as size of the pool increased. Using an isotope-based pool-mixing model, it was calculated that 10±2 µg N g-1 soil were contributed by BNF during the fallow. A lack of BNF combined with removal via denitrification (δ15N-NO3- : δ18O-NO3- = 1) caused relatively lower available N levels in dried and alternate wetting-drying soils during this period. Magnitude and net impact of denitrification was defined by the extent of drying and C availability, with rice straw C additions driving tighter coupling of nitrification and denitrification (δ15N:δ18O <1). However, despite high rates of attenuation during wetting events, soils that had been completely dried and received straw amendments ultimately retained a significantly larger available N pool due to enhanced input from soil organic matter. These findings underline the necessity of, and validate a new means for, accurate quantification micro-scale biogeochemical interactions for developing farm-scale management practices that

  16. Role of Iron Oxyhydrates in Accumulation and Stabilization of Soil Organic Matter in Rice Paddy: Case Studies from China

    NASA Astrophysics Data System (ADS)

    Pan, G.; Lu, H.; Sun, J.; Li, L.; Liu, X.; Zheng, J.; Zhang, X.; Cheng, K.

    2014-12-01

    Iron is an important element in soils, often in forms either of crystalline mineral or amorphous colloids upon redox cycling in hydromorphic soils. However, role of iron particularly via oxyhydrates in organic matter dynamics n rice soils has been not yet well assessed. Rice paddy soils of China have been recognized as a unique type of Anthrosols mostly with iron accumulation and dynamic movement in soil profile through long term hydroagric management. Soil organic matter contents of rice soils are shown significantly correlated with the contents of free or amorphous iron oxyhydrates. And organic matter accumulation in young rice soils followed iron oxyhydrate content changes as rice cultivation proceed, which could be often traced by the changes in iron oxyhydrate-bound OC fractions. The importance of association of OC with iron oxyhydrates is known by the fact that organic carbon was not related to total free iron oxyhydrates in wetland but in rice soil shifted from the wetlands, with OC contents much higher in rice soils than in the precedent wetland soil. This could be attributed to the chemical binding of OC to oxyhydrate surface, contributing to the stabilization of newly sequestered OC. This has been again confirmed by lab incubation studies, where total mineralization of OC has been found significantly lower in iron-oxyhrate rich soil than in iron-oxyhrate poor soils. This effect has been further explored in an incubation study with experimental warming that the temperature dependence of OC mineralization of rice soils from a long term fertilizer treated trial was linked to the abundance of iron oxyhydrate content, varying with the long term management practice. Initial carbon sequestration in rice soil subject to new carbon input was promoted by the iron oxyhydrates in the soil, showing a fast increase in iron hydrate-bound OC in the initial stage. The bound OC exerted further stabilization through enhanced humification to form residual OC fraction in long

  17. [Responses of microbial biomass P to the changes of organic C and P in paddy soils under different fertilization systems].

    PubMed

    Chen, An-Lei; Wang, Kai-Rong; Xie, Xiao-Li; Liu, Ying-Xin

    2007-12-01

    Based on a fifteen years field experiment in double rice-cropping region of subtropical China, the responses of microbial biomass P (MB-P) to organic C and P in red paddy soils under different fertilization systems were investigated. The results indicated that a long-term input of organic carbon sources and the increasing soil organic carbon made soil microbial biomass remain at a high level (MB-C > 800 mg x kg(-1)), being a main reason of the increase of MB-P. Under long-term zero chemical P fertilization, there was a significant decrease in soil total P (P < 0.05), but soil organic P increased by 29.3% on average. The inorganic P forms in deficit were mainly Al-P, Fe-P, Ca-P and O-P, with the lowest content of Al-P (only 0.5 mg x kg(-1) on average). The content of soil MB-P under zero chemical P fertilization was much higher than that of Olsen-P. Correlation analysis showed that there was a significant relationship (P < 0.05) between MB-P and Al-P, from which, it was deduced that the utilization of Al-P, Fe-P, Ca-P and O-P by soil microbes could be the key approach of promoting these P forms transformed into available P. Chemical P fertilization combined with organic nutrient recycling could not only enlarge the soil P pool, but also improve the P availability. PMID:18333448

  18. Response of hydrolytic enzyme activities and nitrogen mineralization to fertilizer and organic matter application in subtropical paddy soils

    NASA Astrophysics Data System (ADS)

    Kader, Mohammed Abdul; Yeasmin, Sabina; Akter, Masuda; Sleutel, Steven

    2016-04-01

    Driving controllers of nitrogen (N) mineralization in paddy soils, especially under anaerobic soil conditions, remain elusive. The influence of exogenous organic matter (OM) and fertilizer application on the activities of five relevant enzymes (β-glucosaminidase, β-glucosidase, L-glutaminase, urease and arylamidase) was measured in two long-term field experiments. One 18-years field experiment was established on a weathered terrace soil with a rice-wheat crop rotation at the Bangabandhu Sheikh Mujibur Rahman Agricultural University (BSMRAU) having five OM treatments combined with two mineral N fertilizer levels. Another 30-years experiment was established on a young floodplain soil with rice-rice crop rotation at the Bangladesh Agricultural University (BAU) having eight mineral fertilizer treatments combined with organic manure. At BSMRAU, N fertilizer and OM amendments significantly increased all enzyme activities, suggesting them to be primarily determined by substrate availability. At BAU, non-responsiveness of β-glucosidase activity suggested little effect of the studied fertilizer and OM amendments on general soil microbial activity. Notwithstanding probably equal microbial demand for N, β-glucosaminidase and L-glutaminase activities differed significantly among the treatments (P>0.05) and followed strikingly opposite trends and correlations with soil organic N mineralization. So enzymatic pathways to acquire N differed by treatment at BAU, indicating differences in soil N quality and bio-availability. L-glutaminase activity was significantly positively correlated to the aerobic and anaerobic N mineralization rates at both field experiments. Combined with negative correlations between β-glucosaminidase activity and N mineralization rates, it appears that terminal amino acid NH2 hydrolysis was a rate-limiting step for soil N mineralization at BAU. Future investigations with joint quantification of polyphenol accumulation and binding of N, alongside an

  19. Cadmium availability in rice paddy fields from a mining area: The effects of soil properties highlighting iron fractions and pH value.

    PubMed

    Yu, Huan-Yun; Liu, Chuanping; Zhu, Jishu; Li, Fangbai; Deng, Dong-Mei; Wang, Qi; Liu, Chengshuai

    2016-02-01

    Cadmium (Cd) availability can be significantly affected by soil properties. The effect of pH value on Cd availability has been confirmed. Paddy soils in South China generally contain high contents of iron (Fe). Thus, it is hypothesized that Fe fractions, in addition to pH value, may play an important role in the Cd bioavailability in paddy soil and this requires further investigation. In this study, 73 paired soil and rice plant samples were collected from paddy fields those were contaminated by acid mine drainage containing Cd. The contents of Fe in the amorphous and DCB-extractable Fe oxides were significantly and negatively correlated with the Cd content in rice grain or straw (excluding DCB-extractable Fe vs Cd in straw). In addition, the concentration of HCl-extractable Fe(II) derived from Fe(III) reduction was positively correlated with the Cd content in rice grain or straw. These results suggest that soil Fe redox could affect the availability of Cd in rice plant. Contribution assessment of soil properties to Cd accumulation in rice grain based on random forest (RF) and stochastic gradient boosting (SGB) showed that pH value should be the most important factor and the content of Fe in the amorphous Fe oxides should be the second most important factor in affecting Cd content in rice grain. Overall, compared with the studies from temperate regions, such as Europe and northern China, Fe oxide exhibited its unique role in the bioavailability of Cd in the reddish paddy soil from our study area. The exploration of practical remediation strategies for Cd from the perspective of Fe oxide may be promising. PMID:26629644

  20. C and N accumulations in soil aggregates determine nitrous oxide emissions from cover crop treated rice paddy soils during fallow season.

    PubMed

    Pramanik, Prabhat; Haque, Md Mozammel; Kim, Sang Yoon; Kim, Pil Joo

    2014-08-15

    Combination of leguminous and non-leguminous plant residues are preferably applied in rice paddy soils to increase the rate of organic matter mineralization and to improve plant growth. However, organic matter addition facilitates methane (CH4) emission from rice paddy soil. Mineralization of organic nitrogen (N) increases NO3-N concentrations in soil, which are precursors for the formation of nitrous oxide (N2O). However, N2O is a minor greenhouse gas emitted from submerged rice field and hence is not often considered during calculation of total global warming potential (GWP) during rice cultivation. The hypothesis of this study was that fluxes of N2O emissions might be changed after removal of flooded water from rice field and the effect of cover crops on N2O emissions in the fallow season might be interesting. However, the effects of N-rich plant residues on N2O emission rates in the fallow season and its effect on annual GWP were not studied before. In this experiment, combination of barley (non-leguminous) and hairy vetch (leguminous) biomasses were applied at 9 Mg ha(-1) and 27 Mg ha(-1) rates in rice paddy soil. Cover crop application significantly increased CH4 emission flux while decreased N2O emissions during rice cultivation. The lowest N2O emission was observed in 27 Mg ha(-1) cover crop treated plots. Cover crop applications increased N contents in soil aggregates especially in smaller aggregates (<250 μm), and that proportionately increased the N2O emission potentials of these soil aggregates. Fluxes of N2O emissions in the fallow season were influenced by the N2O emission potentials of soil aggregates and followed opposite trends as those observed during rice cultivation. Therefore, it could be concluded that the doses of cover crop applications for rice cultivation should not be optimized considering only CH4, but N2O should also be considered especially for fallow season to calculate total GWP. PMID:24880551

  1. Biochar amendment reduces rice Cd uptake in polluted and unpolluted paddy soils: a long term field experiment

    NASA Astrophysics Data System (ADS)

    Bian, R.; Cui, L.; Pan, G.; Li, L.

    2012-04-01

    The bioavailability of Cd in agricultural soils has been a great health concern due to the potential risk through exposure of agro-food produced in Cd-contaminated fields. Yet, rice subject to Cd contamination appears to have expanded at the last decade due to irrigation with waste water and chemical fertilization in south china. This is supposed to raise the Cd accumulation of rice grain. Therefore, techniques to reduce Cd mobility and plant uptake have been a urgent demand for food safety in China.A field experiment was performed in a high-polluted (HP), mid-pollute (MP) and unpolluted (UP) paddy soil with biochar(BC) amendment in 2011. BC was applied in HP, MP and UP in 2008, 2009, 2009 with the rates of 0, 10, 20, 40t ha-1 in HP, MP and 0, 40t ha-1 in UP. The experiment was monitored in 2011. It was observed that BC amendment did not affect rice grain yield but significantly increased soil pH by 0.58-0.77, 1.30 units in MP, UP and there was no difference in HP. The Cacl2 extracted Cd in soil was decreased by 18.1%-28.9% in HP, 49.3%-67.5% in MP and 83.1% in UP, respectively. Meanwhile, H2O extractable Cd in soil was decreased by 20.0%-31.7% in HP, 32.7%-44.2% in MP and 25.0% in UP, respectively. With the BC treatment, rice grain Cd concentration was decreased 4.7%-17.6% in HP, 35.9%-53.4% in MP. Especially in UP field, the rice grain Cd concentration was decreased from 0.22mg kg-1 to 0.07mg kg-1 which was below National standard (0.20mg kg-1) in China. The straw and root Cd contents were also significantly decreased with BC application. Therefore, BC amendment in polluted and unpolluted fields can sustainably reduce rice Cd uptake and it may offer a basic option to reduce Cd levels in rice. Keywords: Biochar, Cd, bioavailability, paddy soil, food safety

  2. Toxic assessment of the leachates of paddy soils and river sediments from e-waste dismantling sites to microalga, Pseudokirchneriella subcapitata.

    PubMed

    Nie, Xiangping; Fan, Canpeng; Wang, Zhaohui; Su, Tian; Liu, Xinyu; An, Taicheng

    2015-01-01

    The potential adverse effects of e-waste recycling activity on environment are getting increasing concern. In this work, a model alga, Pseudokirchneriella subcapitata, was employed to assess the toxic effects of the leachates of paddy soils and river sediments collected from e-waste dismantling sites. Chemical analysis of the paddy soils and river sediments and their leachates were carried out and the growth rate, chlorophyll a fluorescence and anti-oxidative systems of the alga were measured. Results showed that two leachates decreased the amount of PSII active reaction centers and affected photosynthesis performance, interfered with chlorophyll synthesis and inhibited algal growth. Some chemical pollutants in the sediments and soils such as polybrominated diphenyl ethers (PBDEs) and metals derived from e-waste recycling activity may impose oxidative stress on algae and affect the activity of anti-oxidative enzymes such as GST, SOD, CAT and APX. The leachates of both river sediments and paddy soils are potentially toxic to the primary producers, P. subcapitata and the leachate from sediments was more deleterious than that from soils. PMID:25450930

  3. The availabilities of arsenic and cadmium in rice paddy fields from a mining area: The role of soil extractable and plant silicon.

    PubMed

    Yu, Huan-Yun; Ding, Xiaodong; Li, Fangbai; Wang, Xiangqin; Zhang, Shirong; Yi, Jicai; Liu, Chuanping; Xu, Xianghua; Wang, Qi

    2016-08-01

    Adequate silicon (Si) can greatly boost rice yield and improve grain quality through alleviating stresses associated with heavy metals and metalloids such as arsenic (As) and cadmium (Cd). The soil plant-available Si is relatively low in South China due to severe desilicification and allitization of the soils in this region. Conversely, pollution of heavy metals and metalloids in the soils of this region occurs widely, especially As and Cd pollution in paddy soil. Therefore, evaluating the plant availability of Si in paddy soil of South China and examining its correlation with the availability of heavy metals and metalloids are of great significance. Accordingly, in our study, 107 pairs of soil and rice plant samples were collected from paddy fields contaminated by As and Cd in South China. Significantly positive correlations between Si in rice plants and Si fractions in soils extracted with citric acid, NaOAc-HOAc buffer, and oxalate-ammonium oxalate buffer suggest that these extractants are more suitable for use in extracting plant-available Si in the soils of our present study. Significantly negative correlations between different Si fractions and As or Cd in rice plant tissues and negative exponential correlations between the molar ratios of Si to As/Cd in rice roots, straws, husks or grains and As/Cd in rice grains indicate that Si can significantly alleviate the accumulation of As/Cd from soils to the rice plants. Finally, a contribution assessment of soil properties to As/Cd accumulation in rice grains based on random forest showed that in addition to Si concentrations in soil or rice plants, other factors such as Fe fractions and total phosphorus also contributed largely to As/Cd accumulation in rice grains. Overall, Si exhibited its unique role in mitigating As or Cd stress in rice, and our study results provide strong field evidence for this role. PMID:27209244

  4. [Effects of rice straw on the diversity of nitrifying genes (amoA and hao) in paddy soil].

    PubMed

    Chen, Chun-Lan; Chen, Zhe; Zhu, Yi-Jun; Wu, Min-Na; Qin, Hong-Ling; Wei, Wen-Xue

    2010-06-01

    The effects of long-term (16 years) fertilization on the diversity and community structure of soil ammonia-oxidizing gene (amoA) and hydroxylamine-oxidizing gene (hao) in paddy soil were evaluated using the methods of polymerase chain reaction, cloning and sequencing. The soil samples were collected from the treatments of NPK (CK) and NPK plus rice straw (SR) of the long-term field fertilization experiment in Taoyuan Agro-ecological Experimental Station. The Shannon Indices showed that the diversity of amoA and hao in SR treatment was lower than that in CK, and LUBSHUFF statistical analyses demonstrated that the sequence compositions of both amoA and huo libraries were significantly different between CK and SR. The phylogenetic trees indicated that some clusters appeared in SR treatment but were not detected in CK treatment. As to amoA, only Nitrosospira besides the uncultured amoA sequences were cloned from the two treatments, while no Nitrosomonas species were detected. As to hao, the strains from Silicibacter and Methylococcus were dominant in CK, while in SR the strains from Nitrosospira and Nitrosomonas were dominant. Sum up, the long-term rice straw application has caused a remarkable impact on the diversity and community structure on Nitrosobacteria. PMID:20698282

  5. Spatial Changes in the Bacterial Community Structure along a Vertical Oxygen Gradient in Flooded Paddy Soil Cores

    PubMed Central

    Lüdemann, Heiner; Arth, Inko; Liesack, Werner

    2000-01-01

    Molecular ecology techniques were applied to assess changes in the bacterial community structure along a vertical oxygen gradient in flooded paddy soil cores. Microsensor measurements showed that oxygen was depleted from 140 μM at the floodwater/soil interface to nondetectable amounts at a depth of approximately 2.0 mm and below. Bacterial 16S rRNA gene (rDNA)-based community fingerprint patterns were obtained from 200-μm-thick soil slices of both the oxic and anoxic zones by using the T-RFLP (terminal restriction fragment length polymorphism) technique. The fingerprints revealed a tremendous shift in the community patterns in correlation to the oxygen depletion measured with depth. 16S rDNA clone sequences recovered from the oxic or anoxic zone directly corresponded to those terminal restriction fragments which were highly characteristic of the respective zone. Comparative sequence analysis of these clones identified members of the α and β subclasses of Proteobacteria as the abundant populations in the oxic zone. In contrast, members of clostridial cluster I were determined to be the predominant bacterial group in the oxygen-depleted soil. The extraction of total RNA followed by reverse transcription-PCR of the bacterial 16S rRNA and T-RFLP analysis resulted for both oxic and anoxic zones of flooded soil cores in community fingerprint patterns similar to those obtained by the rDNA-based analysis. This finding suggests that the microbial groups detected on the rDNA level are the metabolically active populations within the oxic and anoxic soil slices examined. PMID:10653747

  6. Electro-kinetic remediation coupled with phytoremediation to remove lead, arsenic and cesium from contaminated paddy soil.

    PubMed

    Mao, Xinyu; Han, Fengxiang X; Shao, Xiaohou; Guo, Kai; McComb, Jacqueline; Arslan, Zikri; Zhang, Zhanyu

    2016-03-01

    The objectives of this study were to investigate distribution and solubility of Pb, Cs and As in soils under electrokinetic field and examine the processes of coupled electrokinetic phytoremediation of polluted soils. The elevated bioavailability and bioaccumulation of Pb, As and Cs in paddy soil under an electro-kinetic field (EKF) were studied. The results show that the EKF treatment is effective on lowering soil pH to around 1.5 near the anode which is beneficial for the dissolution of metal(loid)s, thus increasing their overall solubility. The acidification in the anode soil efficiently increased the water soluble (SOL) and exchangeable (EXC) Pb, As and Cs, implying enhanced solubility and elevated overall potential bioavailability in the anode region while lower solubility in the cathode areas. Bioaccumulations of Pb, As and Cs were largely determined by the nature of elements, loading levels and EKF treatment. The native Pb in soil usually is not bioavailable. However, EKF treatment tends to transfer Pb to the SOL and EXC fractions improving the phytoextraction efficiency. Similarly, EKF transferred more EXC As and Cs to the SOL fraction significantly increasing their bioaccumulation in plant roots and shoots. Pb and As were accumulated more in plant roots than in shoots while Cs was accumulated more in shoots due to its similarity of chemical properties to potassium. Indian mustard, spinach and cabbage are good accumulators for Cs. Translocation of Pb, As and Cs from plant roots to shoots were enhanced by EKF. However, this study indicated the overall low phytoextraction efficiency of these plants. PMID:26650421

  7. Effects of Different Application Methods of Methane Fermentation Digested Liquid into the Paddy Plot on Soil Nitrogen Behavior and Rice Yield

    NASA Astrophysics Data System (ADS)

    Watanabe, Satoko; Nakamura, Kimihito; Seok Ryu, Chan; Iida, Michihisa; Kawashima, Shigeto

    Methane fermentation technique with the treatment of animal waste and food waste is drawing public attention as a good option for the utilization of biomass resources and it is investigated how to apply the by-product of fermentation (methane fermentation digested liquid) to agricultural fields as a fertilizer. It is important to determine an adequate method of applying digested liquid to a paddy plot as fertilizer taking into account the concentrations of soil nitrogen components and rice yield. The objective of this study is to compare the performances of three methods of applying digested liquid to paddy plots in terms of the nitrogen transformation in soil, rice yield, and nitrogen load in effluent. The three methods were pouring (with irrigation water), spreading onto the surface of a plot, and injection into paddy soil. It was found that the ammonium nitrogen concentration and the dissolved organic nitrogen concentration in soil of the spreading plot were higher than that for the pouring plot and that for the injecting plot. The rice yield was higher in the spreading plot than in the injecting and pouring plots. And, there was a significant correlation between the rice yield and the dissolved organic nitrogen just before and after the panicle initiation stage. There were no differences in the nitrogen effluent loads with surface drainage.

  8. Highly stable rice-straw-derived charcoal in 3700-year-old ancient paddy soil: evidence for an effective pathway toward carbon sequestration.

    PubMed

    Wu, Mengxiong; Yang, Min; Han, Xingguo; Zhong, Ting; Zheng, Yunfei; Ding, Pin; Wu, Weixiang

    2016-01-01

    Recalcitrant charcoal application is predicted to decelerate global warming through creating a long-term carbon sink in soil. Although many studies have showed high stability of charcoal derived from woody materials, few have focused on the dynamics of straw-derived charcoal in natural environment on a long timescale to evaluate its potential for agricultural carbon sequestration. Here, we examined straw-derived charcoal in an ancient paddy soil dated from ~3700 calendar year before present (cal. year BP). Analytical results showed that soil organic matter consisted of more than 25% of charcoal in charcoal-rich layer. Similarities in morphology and molecular structure between the ancient and the fresh rice-straw-derived charcoal indicated that ancient charcoal was derived from rice straw. The lower carbon content, higher oxygen content, and obvious carbonyl of the ancient charcoal compared with fresh rice straw charcoal implied that oxidation occurred in the scale of thousands years. However, the dominant aromatic C of ancient charcoal indicated that rice-straw-derived charcoal was highly stable in the buried paddy soil due to its intrinsic chemical structures and the physical protection of ancient paddy wetland. Therefore, it may suggest that straw charcoal application is a potential pathway for C sequestration considering its longevity. PMID:25850742

  9. Evaluation of carbon dioxide emission factor from urea during rice cropping season: A case study in Korean paddy soil

    NASA Astrophysics Data System (ADS)

    Kim, Gil Won; Jeong, Seung Tak; Kim, Gun Yeob; Kim, Pil Joo; Kim, Sang Yoon

    2016-08-01

    Fertilization with urea can lead to a loss of carbon dioxide (CO2) that was fixed during the industrial production process. The extent of atmospheric CO2 removal from urea manufacturing was estimated by the Industrial Processes and Product Use sector (IPPU sector). On its basis, the Intergovernmental Panel on Climate Change (IPCC) has proposed a value of 0.2 Mg C per Mg urea (available in 2006 revised IPCC guidelines for greenhouse gas inventories), which is the mass fractions of C in urea, as the CO2 emission coefficient from urea for the agricultural sector. Notably, due to the possibility of bicarbonate leaching to waters, all C in urea might not get released as CO2 to the atmosphere. Hence, in order to provide an accurate value of the CO2 emission coefficient from applied urea in the rice ecosystem, the CO2 emission factors were characterized under different levels of 13C-urea applied paddy field in the current study. The total CO2 fluxes and rice grain yields increased significantly with increasing urea application (110-130 kg N ha-1) and thereafter, decreased. However, with increasing 13C-urea application, a significant and proportional increase of the 13CO2sbnd C emissions from 13C-urea was also observed. From the relationships between urea application levels and 13CO2sbnd C fluxes from 13C-urea, the CO2sbnd C emission factor from urea was estimated to range between 0.0143 and 0.0156 Mg C per Mg urea. Thus, the CO2sbnd C emission factor of this study is less than that of the value proposed by IPCC. Therefore, for the first time, we propose to revise the current IPCC guideline value of CO2sbnd C emission factor from urea as 0.0143-0.0156 Mg C per Mg urea for Korean paddy soils.

  10. Microbial dynamics and arsenic speciation in rice paddy soil under two water management practices

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Arsenic (As) undergoes several microbial transformations, including oxidation/reduction, methylation/demethylation, and volatilization in soil, which impact As bioavailability. Different water management systems for rice cultivation alter soil-redox conditions and As biogeochemistry. Soil microbial ...

  11. [Influences of water-saved and nitrogen-reduced practice on soil microbial and microfauna assemblage in paddy field].

    PubMed

    Gui, Juan; Chen, Xiao-yun; Liu, Man-qiang; Zhuang, Xi-ping; Sun, Zhen; Hu, Feng

    2016-01-01

    The resource and environmental problems caused by excessive consumption of water and fertilizer in rice production have recently aroused widespread concern. This study investigated the effects of irrigation modes (conventional irrigation and 25% water-saved irrigation) and different N application rates (conventional high-nitrogen fertilization and 40% nitrogen-reduced fertilization) on microbial and microfauna assemblages at tillering and ripening stages in paddy field. The results showed that compared with conventional irrigation (CF), water-saved irrigation (WS) decreased the soil pH at tillering stage. Soil dissolved organic matter (dissolved organic C and N) and microbial biomass C and N were significantly affected by irrigation, nitrogen fertilizer and their interactions. WS or N-reduced fertilization (LN) decreased the contents of dissolved organic matter; WS increased microbial biomass C but decreased microbial biomass N. Nitrate was significantly higher in WS than CF, while ammonium showed reverse pattern. At tillering stage, the soil microbial biomass from bacteria, fungi, actinomy and protozoa was higher in WS than in CF, but the trend was opposite at ripening stage. There was a significant interation between irrigation and fertilization on soil rotifer numbers and microbial-feeding nematodes. At tillering stage, WS increased the numbers of rotifer and nematode, and also the proportion of bacterial-feeding nematode; LN increased the abundance of rotifer but decreased the abundance of nematode. In summary, soil microbial and microfauna assemblages showed different response to water-saved and nitrogen-reduced agricultural managements, which depended on different crop growth stages, but also the complex interactions of water and nitrogen and between biological groups in food webs. PMID:27228599

  12. The specific role of fungal community structure on soil aggregation and carbon sequestration: results from long-term field study in a paddy soil

    NASA Astrophysics Data System (ADS)

    Murugan, Rajasekaran; Kumar, Sanjay

    2015-04-01

    Soil aggregate stability is a crucial soil property that affects soil biota, biogeochemical processes and C sequestration. The relationship between soil aggregate stability and soil C cycling is well known but the influence of specific fungal community structure on this relationship is largely unknown in paddy soils. The aim of the present study was to evaluate the long-term fertilisation (mineral fertiliser-MIN; farmyard manure-FYM; groundnut oil cake-GOC) effects on soil fungal community shifts associated with soil aggregates under rice-monoculture (RRR) and rice-legume-rice (RLR) systems. Fungal and bacterial communities were characterized using phospholipid fatty acids, and glucosamine and muramic acid were used as biomarkers for fungal and bacterial residues, respectively. Microbial biomass C and N, fungal biomass and residues were significantly higher in the organic fertiliser treatments than in the MIN treatment, for all aggregate sizes under both crop rotation systems. In general, fungal/bacterial biomass ratio and fungal residue C/bacterial residue C ratio were significantly higher in macroaggregate fractions (> 2000 and 250-2000 μm) than in microaggregate fractions (53-250 and <53 μm). In both crop rotation systems, the long-term application of FYM and GOC led to increased accumulation of saprotrophic fungi (SF) in aggregate fractions > 2000 μm. In contrast, we found that arbuscular mycorrhizal fungi (AMF) was surprisingly higher in aggregate fractions > 2000 μm than in aggregate fraction 250-2000 μm under MIN treatment. The RLR system showed significantly higher AMF biomass and fungal residue C/ bacterial residue C ratio in both macroaggregate fractions compared to the RRR system. The strong relationships between SF, AMF and water stable aggregates shows the specific contribution of fungi community on soil aggregate stability. Our results highlight the fact that changes within fungal community structure play an important role in shaping the soil

  13. Alkaline biosolids and EDTA for phytoremediation of an acidic loamy soil spiked with cadmium.

    PubMed

    Wong, Jonathan W C; Wong, Winnie W Y; Wei, Zhenggui; Jagadeesan, Hema

    2004-05-25

    A greenhouse experiment was conducted to investigate the growth of Brassica juncea and Cd phytoextraction in a mimicked Cd contaminated acidic loamy soil amended with alkaline biosolids, prepared from sewage sludge and coal fly ash, in the presence and absence of EDTA at 2 mmol kg(-1). The acidic loamy soil was spiked with 0, 5, 20, 50 and 100 mg Cd kg(-1) in the form of CdCO(3) and then amended with 4% alkaline biosolids (w/w). Alkaline biosolids and 0.12% CaCO(3) amendments resulted in a higher biomass than unamended soil spiked with 20 mg kg(-1) Cd where plants did not survive and of the two amendments, alkaline biosolids amendment had higher plant dry weight yield and phytoextraction of Cd. Adding 2 mmol kg(-1) EDTA to alkaline biosolids amended soil significantly increased the solubility of Cd ions by 9- to 29-fold, but plant Cd accumulation decreased by a factor of 24-48%. The results indicate that alkaline biosolids amendment is an effective approach for assisting growth of B. juncea and phytoextraction of Cd from the contaminated acidic loamy soil, but further application of chelating agents did not enhance the phytoextraction efficiency of Cd. PMID:15081709

  14. Heavy metal pollution and ecological risk assessment of the paddy soils near a zinc-lead mining area in Hunan.

    PubMed

    Lu, Sijin; Wang, Yeyao; Teng, Yanguo; Yu, Xuan

    2015-10-01

    Soil pollution by Cd, Hg, As, Pb, Cr, Cu, and Zn was characterized in the area of the mining and smelting of metal ores at Guiyang, northeast of Hunan Province. A total of 150 topsoil (0-20 cm) samples were collected in May 2012 with a nominal density of one sample per 4 km(2). High concentrations of heavy metals especially, Cd, Zn, and Pb were found in many of the samples taken from surrounding paddy soil, indicating a certain extent of spreading of heavy metal pollution. Sequential extraction technique and risk assessment code (RAC) were used to study the mobility of chemical forms of heavy metals in the soils and their ecological risk. The results reveal that Cd represents a high ecological risk due to its highest percentage of the exchangeable and carbonate fractions. The metals of Zn and Cu pose a medium risk, and the rest of the metals represent a low environmental risk. The range of the potential ecological risk of soil calculated by risk index (RI) was 123.5~2791.2 and revealed a considerable-high ecological risk in study area especially in the neighboring and surrounding the mining activities area. Additionally, cluster analyses suggested that metals such as Pb, As, Hg, Zn, and Cd could be from the same sources probably related to the acidic drainage and wind transport of dust. Cluster analysis also clearly distinguishes the samples with similar characteristics according to their spatial distribution. The results could be used during the ecological risk screening stage, in conjunction with total concentrations and metal fractionation values to better estimate ecological risk. PMID:26373302

  15. Pollution, fractionation, and mobility of Pb, Cd, Cu, and Zn in garden and paddy soils from a Pb/Zn mining area.

    PubMed

    Lei, Ming; Zhang, Yong; Khan, Sardan; Qin, Pu-feng; Liao, Bo-han

    2010-09-01

    This study was conducted to investigate the pollution load index, fraction distributions, and mobility of Pb, Cd, Cu, and Zn in garden and paddy soils collected from a Pb/Zn mine in Chenzhou City, China. The samples were analyzed using Leleyter and Probst's sequential extraction procedures. Total metal concentrations including Pb, Cd, Cu, and Zn exceeded the maximum permissible limits for soils set by the Ministry of Environmental Protection of China, and the order of the pollution index was Cd > Zn > Pb > Cu, indicating that the soils from both sites seriously suffered from heavy metal pollution, especially Cd. The sums of metal fractions were in agreement with the total contents of heavy metals. However, there were significant differences in fraction distributions of heavy metals in garden and paddy soils. The residual fractions of heavy metals were the predominant form with 43.0% for Pb, 32.3% for Cd, 33.5% for Cu, and 44.2% for Zn in garden soil, while 51.6% for Pb, 40.4% for Cd, 40.3% for Cu, and 40.9% for Zn in paddy soil. Furthermore, the proportions of water-soluble and exchangeable fractions extracted by the selected analytical methods were the lowest among all fractions. On the basis of the speciation of heavy metals, the mobility factor values of heavy metals have the following order: Cd (25.2-19.8%) > Cu (22.6-6.3%) > Zn (9.6-6.0%) > Pb (6.7-2.5%) in both contaminated soils. PMID:19669583

  16. Pseudomonas zhaodongensis sp. nov., isolated from saline and alkaline soils.

    PubMed

    Zhang, Lei; Pan, Yuanyuan; Wang, Kaibiao; Zhang, Xiaoxia; Zhang, Cheng; Zhang, Shuang; Fu, Xiaowei; Jiang, Juquan

    2015-03-01

    Strain NEAU-ST5-21(T) was isolated from saline and alkaline soils in Zhaodong City, Heilongjiang Province, China. It was aerobic, Gram-stain-negative, rod-shaped and motile with a polar flagellum. It produced yellow-orange colonies with a smooth surface, and grew in the presence of 0-5 % (w/v) NaCl (optimum 0 %, w/v), at temperatures of 20-40 °C (optimum 28 °C) and at pH 7-11 (optimum pH 7). Phylogenetic analyses based on the separate 16S rRNA gene sequences and concatenated 16S rRNA, gyrB and rpoD gene sequences indicated that strain NEAU-ST5-21(T) belongs to the genus Pseudomonas in the class Gammaproteobacteria. The most closely related species is Pseudomonas xanthomarina, whose type strain (KMM 1447(T)) showed gene sequence similarities of 99.0 % for 16S rRNA, 81.8 % for gyrB and 85.0 % for rpoD with strain NEAU-ST5-21(T). DNA-DNA hybridization values between strain NEAU-ST5-21(T) and P. xanthomarina DSM 18231(T), Pseudomonas kunmingensis CGMCC 1.12273(T), Pseudomonas stutzeri DSM 5190(T), Pseudomonas oleovorans subsp. lubricantis DSM 21016(T), Pseudomomas chengduensis CGMCC 2318(T), Pseudomonas alcaliphila DSM 17744(T) and Pseudomonas toyotomiensis DSM 26169(T) were 52±0 % to 25±2 %. The DNA G+C content of strain NEAU-ST5-21(T) was 65 mol%. The major fatty acids (>10 %) were C18 : 1ω7c and/or C18 : 1ω6c, C16 : 1ω7c and/or C16 : 1ω6c and C16 : 0, the predominant respiratory quinone was ubiquinone 9, and polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, one unknown phospholipid, phosphatidylglycerol, one unknown aminolipid, one unknown lipid and a glycolipid. The proposed name is Pseudomonas zhaodongensis sp. nov., NEAU-ST5-21(T) ( = ACCC 06362(T) = DSM 27559(T)) being the type strain. PMID:25574037

  17. Lysinibacillus halotolerans sp. nov., isolated from saline-alkaline soil.

    PubMed

    Kong, Delong; Wang, Yanwei; Zhao, Bingqiang; Li, Yanting; Song, Jinlong; Zhai, Yi; Zhang, Chi; Wang, Huimin; Chen, Xiaorong; Zhao, Bin; Ruan, Zhiyong

    2014-08-01

    A novel aerobic, halotolerant bacterium, designated strain LAM612(T), was isolated from saline-alkaline soil samples from Lingxian County, Shandong Province, China. Cells of strain LAM612(T) were Gram-reaction-positive, endospore-forming, motile and rod-shaped. The optimal temperature and pH for growth were 35 °C and pH 6.0, respectively. Strain LAM612(T) could grow in the presence of up to 10% (w/v) NaCl. The genomic DNA G+C conten was 36.4 mol% as detected by the T(m) method. Comparative analysis of 16S rRNA gene sequences revealed that LAM612(T) was closely related to Lysinibacillus sinduriensis KACC 16611(T) (98.0%), L. chungkukjangi KACC 16626(T) (97.5%), L. massiliensis KCTC 13178(T) (97.4%), L. xylanilyticus KACC 15113(T) (97.2%), L. macroides DSM 54(T) (97.0%) and L. manganicus DSM 26584(T) (96.5%). The DNA-DNA hybridization values between strain LAM612(T) and its closest relatives ranged from 20.6% to 41.9%. The major fatty acids of strain LAM612(T) were iso-C(15 : 0) (40.8%), iso-C(16 : 0) (15.2%) and anteiso-C(15 : 0) (10.8%). The cell-wall peptidoglycan content was A4α (L-Lys-D-Asp). The predominant menaquinone was MK-7 and the main polar lipids were diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, three unknown phospholipids, five unknown glycolipids and an unknown lipid. Based on the DNA-DNA hybridization results and phenotypic, phylogenetic and chemotaxonomic properties, strain LAM612(T) could be distinguished from the recognized species of the genus Lysinibacillus, and was suggested to represent a novel species of this genus, for which the name Lysinibacillus halotolerans sp. nov. is proposed. The type strain is LAM612(T) ( = ACCC 00718(T) = JCM 19611(T)). PMID:24814335

  18. Fate of rice shoot and root residues, rhizodeposits, and microbe-assimilated carbon in paddy soil - Part 1: Decomposition and priming effect

    NASA Astrophysics Data System (ADS)

    Zhu, Zhenke; Zeng, Guanjun; Ge, Tida; Hu, Yajun; Tong, Chengli; Shibistova, Olga; He, Xinhua; Wang, Juan; Guggenberger, Georg; Wu, Jinshui

    2016-08-01

    The input of recently photosynthesized C has significant implications on soil organic C sequestration, and in paddy soils, both plants and soil microbes contribute to the overall C input. In the present study, we investigated the fate and priming effect of organic C from different sources by conducting a 300-day incubation study with four different 13C-labelled substrates: rice shoots (shoot-C), rice roots (root-C), rice rhizodeposits (rhizo-C), and microbe-assimilated C (micro-C). The efflux of both 13CO2 and 13CH4 indicated that the mineralization of C in shoot-C-, root-C-, rhizo-C-, and micro-C-treated soils rapidly increased at the beginning of the incubation and decreased gradually afterwards. The highest cumulative C mineralization was observed in root-C-treated soil (45.4 %), followed by shoot-C- (31.9 %), rhizo-C- (7.90 %), and micro-C-treated (7.70 %) soils, which corresponded with mean residence times of 39.5, 50.3, 66.2, and 195 days, respectively. Shoot and root addition increased C emission from native soil organic carbon (SOC), up to 11.4 and 2.3 times higher than that of the control soil by day 20, and decreased thereafter. Throughout the incubation period, the priming effect of shoot-C on CO2 and CH4 emission was strongly positive; however, root-C did not exhibit a significant positive priming effect. Although the total C contents of rhizo-C- (1.89 %) and micro-C-treated soils (1.90 %) were higher than those of untreated soil (1.81 %), no significant differences in cumulative C emissions were observed. Given that about 0.3 and 0.1 % of the cumulative C emission were derived from labelled rhizo-C and micro-C, we concluded that the soil organic C-derived emissions were lower in rhizo-C- and micro-C-treated soils than in untreated soil. This indicates that rhizodeposits and microbe-assimilated C could be used to reduce the mineralization of native SOC and to effectively improve soil C sequestration. The contrasting behaviour of the different

  19. Factors affecting variation in CH4 emission from paddy soils grown with different rice cultivars: A pot experiment

    NASA Astrophysics Data System (ADS)

    Watanabe, Akira; Kimura, Makoto

    1998-08-01

    The growth of rice plants greatly influences CH4 emission from paddy fields through the supply of organic materials such as root exudates and sloughed tissues, the release of oxygen to the root environment, and the transfer of CH4 from the rhizosphere into the atmosphere through the aerenchyma. In the present pot experiments, the effects of the release of water-soluble organic substances from roots, the air space in roots, and the CH4-oxidizing capacity of roots on intervarietal differences in CH4 emission were examined using three Japonica type cultivars (Norin 25, Nipponbare, and Aoinokaze), which differ in morphological properties. The CH4 emission rates varied among the cultivars from mid-July (tillering stage) to the beginning of September (heading stage).Total CH4 emission throughout the rice growth period was largest for Norin 25, followed by Nipponbare, and Aoinokaze. In August, the rate of release of water-soluble organic substances from roots was largest for Norin 25. The air space in roots was also largest in Norin 25 and least in Aoinokaze. The stable carbon isotopic ratios (δ13C) of CH4 in roots were 3-10‰ higher than those in soil in August. The difference in δ13C values of CH4 between roots and soil was largest for Aoinokaze and smallest for Norin 25. In September, the difference in δ13C values of CH4 between roots and soil became small (2-3‰). These findings suggest that the proportion of CH4 oxidation in the rhizosphere was largest in the cultivar which emitted the smallest amount of CH4 and that the proportion became smaller with continued plant growth.

  20. Competitive interactions between methane- and ammonia-oxidizing bacteria modulate carbon and nitrogen cycling in paddy soil

    NASA Astrophysics Data System (ADS)

    Zheng, Y.; Huang, R.; Wang, B. Z.; Bodelier, P. L. E.; Jia, Z. J.

    2014-03-01

    Pure culture studies have demonstrated that methanotrophs and ammonia oxidizers can both carry out the oxidation of methane and ammonia. However, the expected interactions resulting from these similarities are poorly understood, especially in complex, natural environments. Using DNA-based stable isotope probing and pyrosequencing of 16S rRNA and pmoA genes, we report on biogeochemical and molecular evidence for growth stimulation of methanotrophic communities by ammonium fertilization, and that methane modulates nitrogen cycling by competitive inhibition of nitrifying communities in a rice paddy soil. Pairwise comparison between microcosms amended with CH4, CH4+Urea, and Urea indicated that urea fertilization stimulated methane oxidation activity by 6-fold during a 19 day incubation period, while ammonia oxidation activity was significantly inhibited in the presence of CH4. Pyrosequencing of the total 16S rRNA genes revealed that urea amendment resulted in rapid growth of Methylosarcina-like type Ia MOB, and nitrifying communities appeared to be suppressed by methane. High-throughput sequencing of the 13C-labeled DNA further revealed that methane amendment resulted in clear growth of Methylosarcina-related MOB while methane plus urea led to equal increase in Methylosarcina and Methylobacter-related MOB, indicating the differential growth requirements of representatives of these genera. Strikingly, type Ib MOB did not respond to methane nor to urea. Increase in 13C-assimilation by microorganisms related to methanol oxidizers clearly indicated carbon transfer from methane oxidation to other soil microbes, which was enhanced by urea addition. The active growth of type Ia methanotrops was significantly stimulated by urea amendment, and the pronounced growth of methanol-oxidizing bacteria occurred in CH4-treated microcosms only upon urea amendment. Methane addition inhibited the growth of Nitrosospira and Nitrosomonas in urea-amended microcosms, in addition of nitrite

  1. Depth distribution of abiotic drivers of N mineralization and methane emission from a continuously and intermittently flooded Bangladeshi paddy soil

    NASA Astrophysics Data System (ADS)

    Akter, Masuda; Kader, Md. Abdul; Pierreux, Sofie; Boeckx, Pascal; Kamal, Ahammad Mostafa; Sleutel, Steven

    2016-04-01

    logically linked. The elevated redox potential in puddle layer depth increments during AWD drainage events, significantly (p<0.01) declined the cumulative CH4 emission by 47% when compared to CF management. Moreover, seasonal CH4 emissions in N-fertilized fields (N120) decreased by 29 and 8% under CF and AWD, respectively relative to the control (N0), possibly due to promotion of methanotrophs, which were N-limited in N0. Mostly, mineral N content in N120 plots of AWD and CF exceeded contents in the N0 fields. Contrary to CH4 emission, irrigation management did not affect evolutions of pH, Fe, Mn and DOC in soil solution. Likewise, soil exchangeable N content evolution was unaffected and followed zero-order kinetics (N120: R2=0.53 to 0.81; N0: R2=0.12 to 0.48). Our results generally indicate that in Northern Bangladesh's Boro season, evolutions in paddy soil solution chemistry and CH4 emission are strongly depending on course soil temperature and only secondarily on irrigation management. Whether temperature steers microbial activity and methanogenesis directly or via concomitant plant activity and exudation is not known. Key words: Redox, CH4, emission, mineralization, Fe, Mn, DOC, water management

  2. The Distribution Coefficients and Gasification Ratios of [1,2-{sup 14}C] Sodium Acetate for Various Paddy Soils in Japan

    SciTech Connect

    Ishii, N.; Takeda, H.; Uchida, S.

    2008-07-01

    For appropriate safety assessment of the disposal of TRU waste, distribution coefficients (K{sub d}) and gasification ratios of {sup 14}C labeled [1, 2-{sup 14}C] sodium acetate ({sup 14}C-NaOAc) were determined by batch sorption tests for 85 Japanese paddy soil samples. The soil studied were from four soil types: Andsol; Gley; Gray lowland; and Yellow. The range of K{sub d} values for all soil samples was from 7.5 to 295.2 mL g{sup -1}, and the mean value was 105.6 mL g{sup -1}. This mean value was higher than that of previous study (1). The high K{sub d} values of the present study could be a result of the properties of the paddy soils. The comparison of K{sub d} values by each soil type revealed statistically significant difference between Andsol and Gray lowland soils (P < 0.05). The soil type was one of the factors affecting partitioning of {sup 14}C-NaOAc. Gasification ratios ranged from 29.1% to 83.3%, and its mean value was 66.4% of the total {sup 14}C-NaOAc added. These results suggest that most of the radiocarbon in {sup 14}C-NaOAc will be released from soil into the air as gases. The gasification ratio between soil types was also compared, but no statistically significant difference was found. Gas production may be controlled by other than physicochemical properties of soil, for example by factors such as bacterial community. In addition, both the K{sub d} values and the gasification ratios for Gley soil were decreased according to the increase in pH although the underlaying mechanisms for this observation are not clear. (authors)

  3. [Effect of municipal sludge and chemical fertilizers on phthalic acid esters (PAEs) contents in Ipomoea aquatica grown on paddy soils].

    PubMed

    Cai, Quanying; Mo, Cehui; Zhu, Xizhen; Wu, Qitang; Wang, Boguang; Jiang, Chengai; Li, Haiqin

    2003-11-01

    GC/MS determinations on six phthalic acid esters (PAEs) in Ipomoea aquatic grown on potted paddy soil fertilized with municipal sludge and chemical fertilizers showed that the total contents of PAEs (sigma PAEs) in Ipomoea aquatic aboveground parts ranged from 2.129 mg.kg-1 to 7.111 mg.kg-1, decreasing in order of Guangzhou sludge + fertilizers (7.111 mg.kg-1) > Guangzhou sludge (4.767 mg.kg-1) > Foshan sludge (3.569 mg.kg-1) > Foshan sludge + fertilizers (3.305 mg.kg-1) > fertilizers (2.638 mg.kg-1) > control (2.129 mg.kg-1), indicating that compared with control, fertilization increased sigma PAEs in Ipomoea aquatica to a different extent. Only certain compounds of PAEs in different treatments of Ipomoea aquatica were dominant, e.g., butylbenzyl phthalate (BBP) in control, chemical fertilizers, Foshan sludge, and Guangzhou sludge accounted for 40% to 80% of sigma PAEs, di-n-butyl phthalate(DnBP) in foshan sludge + chemical fertilizers accounted for 56%, while di-n-octyl phthalate(DnOP), di(2-ethylhexyl)phthalate(DEHP) and BBP in Guangzhou sludge + chemical fertilizers accounted for approximately 30%. sigma PAEs and the contents of its most compounds were higher in the plants of Ipomoea aquatica than in its roots to a different extent. PMID:14997666

  4. Long-term nitrogen fertilization of paddy soil shifts iron-reducing microbial community revealed by RNA-(13)C-acetate probing coupled with pyrosequencing.

    PubMed

    Ding, Long-Jun; Su, Jian-Qiang; Xu, Hui-Juan; Jia, Zhong-Jun; Zhu, Yong-Guan

    2015-03-01

    Iron reduction is an important biogeochemical process in paddy soils, yet little is known about the microbial coupling between nitrogen and iron reduction. Here, we investigated the shift of acetate-metabolizing iron-reducers under long-term nitrogen fertilization using (13)C-acetate-based ribosomal RNA (rRNA)-stable isotope probing (SIP) and pyrosequencing in an incubation experiment, and the shift of putative iron-reducers in original field samples were investigated by 16S rRNA gene-based pyrosequencing. During SIP incubations, in the presence of iron(III) oxyhydroxides, more iron(II) formation and less methane production were detected in nitrogen-fertilized (N) compared with non-fertilized (NF) soil. In (13)C-rRNA from microcosms amended with ferrihydrite (FER), Geobacter spp. were the important active iron-reducers in both soils, and labeled to a greater extent in N (31% of the bacterial classified sequences) than NF soils (11%). Pyrosequencing of the total 16S rRNA transcripts from microcosms at the whole community level further revealed hitherto unknown metabolisms of potential FER reduction by microorganisms including Pseudomonas and Solibacillus spp. in N soil, Dechloromonas, Clostridium, Bacillus and Solibacillus spp. in NF soil. Goethite (GOE) amendment stimulated Geobacter spp. to a lesser extent in both soils compared with FER treatment. Pseudomonas spp. in the N soil and Clostridium spp. in the NF soil may also be involved in GOE reduction. Pyrosequencing results from field samples showed that Geobacter spp. were the most abundant putative iron-reducers in both soils, and significantly stimulated by long-term nitrogen fertilization. Overall, for the first time, we demonstrate that long-term nitrogen fertilization promotes iron(III) reduction and modulates iron-reducing bacterial community in paddy soils. PMID:25171335

  5. Fractionation and solubility of cadmium in paddy soils amended with porous hydrated calcium silicate.

    PubMed

    Zhao, Xiu-Lan; Masaihiko, Saigusa

    2007-01-01

    Previous studies have shown that porous hydrated calcium silicate (PS) is very effective in decreasing cadmium (Cd) content in brown rice. However, it is unclear whether the PS influences cadmium transformation in soil. The present study examined the effect of PS on pH, cadmium transformation and cadmium solubility in Andosol and Alluvial soil, and also compared its effects with CaCO3, acidic porous hydrated calcium silicate (APS) and silica gel. Soil cadmium was operationally fractionationed into exchangeable (Exch), bound to carbonates (Carb), bound to iron and manganese oxides (FeMnO(x)), bound to organic matters (OM) and residual (Res) fraction. Application of PS and CaCO3 at hig rates enhanced soil pH, while APS and silica gel did not obviously change soil pH. PS and CaCO3 also increased the FeMnO(x)-Cd in Andosol and Carb-Cd in Alluvial soil, thus reducing the Exch-Cd in the tested soils. However, PS was less effective than CaCO3 at the same application rate. Cadmium fractions in the two soils were not changed by the treatments of APS and silica gel. There were no obvious differences in the solubility of cadmium in soils treated with PS, APS, silica gel and CaCO3 except Andosol treated 2.0% CaCO3 at the same pH of soil-CaCl2 suspensions. These findings suggested that the decrease of cadmium availability in soil was mainly attributed to the increase of soil pH caused by PS. PMID:17918598

  6. Comparative Phylogenetic Assignment of Environmental Sequences of Genes Encoding 16S rRNA and Numerically Abundant Culturable Bacteria from an Anoxic Rice Paddy Soil

    PubMed Central

    Hengstmann, Ulf; Chin, Kuk-Jeong; Janssen, Peter H.; Liesack, Werner

    1999-01-01

    We used both cultivation and direct recovery of bacterial 16S rRNA gene (rDNA) sequences to investigate the structure of the bacterial community in anoxic rice paddy soil. Isolation and phenotypic characterization of 19 saccharolytic and cellulolytic strains are described in the accompanying paper (K.-J. Chin, D. Hahn, U. Hengstmann, W. Liesack, and P. H. Janssen, Appl. Environ. Microbiol. 65:5042–5049, 1999). Here we describe the phylogenetic positions of these strains in relation to 57 environmental 16S rDNA clone sequences. Close matches between the two data sets were obtained for isolates from the culturable populations determined by the most-probable-number counting method to be large (3 × 107 to 2.5 × 108 cells per g [dry weight] of soil). This included matches with 16S rDNA similarity values greater than 98% within distinct lineages of the division Verrucomicrobia (strain PB90-1) and the Cytophaga-Flavobacterium-Bacteroides group (strains XB45 and PB90-2), as well as matches with similarity values greater than 95% within distinct lines of descent of clostridial cluster XIVa (strain XB90) and the family Bacillaceae (strain SB45). In addition, close matches with similarity values greater than 95% were obtained for cloned 16S rDNA sequences and bacteria (strains DR1/8 and RPec1) isolated from the same type of rice paddy soil during previous investigations. The correspondence between culture methods and direct recovery of environmental 16S rDNA suggests that the isolates obtained are representative geno- and phenotypes of predominant bacterial groups which account for 5 to 52% of the total cells in the anoxic rice paddy soil. Furthermore, our findings clearly indicate that a dual approach results in a more objective view of the structural and functional composition of a soil bacterial community than either cultivation or direct recovery of 16S rDNA sequences alone. PMID:10543822

  7. Contrasting effects of elevated CO2 and warming on temperature sensitivity of soil organic matter decomposition in a Chinese paddy field.

    PubMed

    Chen, Zhaozhi; Wang, Bingyu; Wang, Jinyang; Pan, Genxing; Xiong, Zhengqin

    2015-10-01

    Climate changes including elevated CO2 and temperature have been known to affect soil carbon (C) storage, while the effects of climate changes on the temperature sensitivity of soil organic matter (SOM) are unclear. A 365-day laboratory incubation was used to investigate the temperature sensitivity for decomposition of labile (Q 10-L) and recalcitrant (Q 10-R) SOMs by comparing the time required to decompose a given amount of C at 25 and 35 °C. Soils were collected from a paddy field that was subjected to four treatments: ambient CO2 and temperature, elevated CO2 (500 μmol/mol), enhanced temperature (+2 °C), and their combination. The results showed that the temperature sensitivity of SOM decomposition increased with increasing SOM recalcitrance in this paddy soil (Q 10-L = 2.21 ± 0.16 vs. Q 10-R = 2.78 ± 0.42; mean ± SD). Elevated CO2 and enhanced temperature showed contrasting effects on the temperature sensitivity of SOM decomposition. Elevated CO2 stimulated Q 10-R but had no effect on Q 10-L; in contrast, enhanced temperature increased Q 10-L but had no effect on Q 10-R. Furthermore, the elevated CO2 combined with enhanced temperature treatment significantly increased Q 10-L and Q 10-R by 18.9 and 10.2 %, respectively, compared to the ambient conditions. Results suggested that the responses of SOM to temperature, especially for the recalcitrant SOM pool, were altered by climate changes. The greatly enhanced temperature sensitivity of SOM decomposition by elevated CO2 and temperature indicates that more CO2 will be released to the atmosphere and losses of soil C may be even greater than that previously expected in paddy field. PMID:27590882

  8. Effects of Tillage and Nitrogen Fertilizers on CH4 and CO2 Emissions and Soil Organic Carbon in Paddy Fields of Central China

    PubMed Central

    Zhi-Kui, Kou; Zhi-Sheng, Zhang; Jin-Ping, Wang; Ming-Li, Cai; Cou-Gui, Cao

    2012-01-01

    Quantifying carbon (C) sequestration in paddy soils is necessary to help better understand the effect of agricultural practices on the C cycle. The objective of the present study was to assess the effects of tillage practices [conventional tillage (CT) and no-tillage (NT)] and the application of nitrogen (N) fertilizer (0 and 210 kg N ha−1) on fluxes of CH4 and CO2, and soil organic C (SOC) sequestration during the 2009 and 2010 rice growing seasons in central China. Application of N fertilizer significantly increased CH4 emissions by 13%–66% and SOC by 21%–94% irrespective of soil sampling depths, but had no effect on CO2 emissions in either year. Tillage significantly affected CH4 and CO2 emissions, where NT significantly decreased CH4 emissions by 10%–36% but increased CO2 emissions by 22%–40% in both years. The effects of tillage on the SOC varied with the depth of soil sampling. NT significantly increased the SOC by 7%–48% in the 0–5 cm layer compared with CT. However, there was no significant difference in the SOC between NT and CT across the entire 0–20 cm layer. Hence, our results suggest that the potential of SOC sequestration in NT paddy fields may be overestimated in central China if only surface soil samples are considered. PMID:22574109

  9. Effects of tillage and nitrogen fertilizers on CH4 and CO2 emissions and soil organic carbon in paddy fields of central China.

    PubMed

    Cheng-Fang, Li; Dan-Na, Zhou; Zhi-Kui, Kou; Zhi-Sheng, Zhang; Jin-Ping, Wang; Ming-Li, Cai; Cou-Gui, Cao

    2012-01-01

    Quantifying carbon (C) sequestration in paddy soils is necessary to help better understand the effect of agricultural practices on the C cycle. The objective of the present study was to assess the effects of tillage practices [conventional tillage (CT) and no-tillage (NT)] and the application of nitrogen (N) fertilizer (0 and 210 kg N ha(-1)) on fluxes of CH(4) and CO(2), and soil organic C (SOC) sequestration during the 2009 and 2010 rice growing seasons in central China. Application of N fertilizer significantly increased CH(4) emissions by 13%-66% and SOC by 21%-94% irrespective of soil sampling depths, but had no effect on CO(2) emissions in either year. Tillage significantly affected CH(4) and CO(2) emissions, where NT significantly decreased CH(4) emissions by 10%-36% but increased CO(2) emissions by 22%-40% in both years. The effects of tillage on the SOC varied with the depth of soil sampling. NT significantly increased the SOC by 7%-48% in the 0-5 cm layer compared with CT. However, there was no significant difference in the SOC between NT and CT across the entire 0-20 cm layer. Hence, our results suggest that the potential of SOC sequestration in NT paddy fields may be overestimated in central China if only surface soil samples are considered. PMID:22574109

  10. Transport behavior and rice uptake of radiostrontium and radiocesium in flooded paddy soils contaminated in two contrasting ways.

    PubMed

    Choi, Yong-Ho; Lim, Kwang-Muk; Jun, In; Keum, Dong-Kwon; Han, Moon-Hee; Kim, In-Gyu

    2011-12-15

    In order to investigate the transport behavior and rice uptake of radiostrontium and radiocesium in flooded rice fields, lysimeter experiments with two paddy soils were performed in a greenhouse. A solution containing (85)Sr and (137)Cs was applied in two different ways - being mixed with the top soil 27 d before transplanting or being dropped to the surface water 1d after transplanting. Rice uptake was quantified with two kinds of transfer factor - TF(m) (dimensionless) and TF(a) (m(2)kg(-1)-dry) for the pre- and post-transplanting depositions, respectively. For brown rice, the TF(m) values of (85)Sr and (137)Cs differed between the soils by factors of 2 (1.6×10(-2) and 2.5×10(-2)) and 7 (2.2×10(-2) and 1.5×10(-1)), respectively. Corresponding factors by the TF(a) values were 2 (2.5×10(-4) and 4.4×10(-4)) for (85)Sr and 3 (1.1×10(-3) and 2.9×10(-3)) for (137)Cs. Straws had several times higher TF(m) and TF(a) values of (85)Sr than of (137)Cs. The surface-water concentrations were substantially higher for the TF(a) than for the TF(m), indicating the possibility of a much higher plant-base uptake for the TF(a). In the TF(a) soils, (137)Cs and, to a lesser degree, (85)Sr were severely localized towards the soil surface, probably leading to an increased root uptake. The activity loss due to plant uptake and water percolation was generally inconsiderable. Time-dependent K(d) values of (85)Sr measured in a parallel experiment ranged from 20 to 170, whereas (137)Cs had much higher K(d) values. The use of TF(a) values instead of TF(m) values turned out to be a reasonable approach to the evaluation of a vegetation-period deposition. PMID:22071438

  11. Variation of grain Cd and Zn concentrations of 110 hybrid rice cultivars grown in a low-Cd paddy soil.

    PubMed

    Shi, Jing; Li, Lianqing; Pan, Genxing

    2009-01-01

    Enhanced Cd uptake and Zn depletion in rice grains and high potential for food Cd exposure by the high-yielding hybrid cultivars of China had been addressed. A field experiment was conducted in 2006 to determine the difference in grain Cd and Zn between cultivars. Total 110 cultivars including super rice and common hybrid rice cultivars were grown on a single paddy soil (Entic Haplaquept) with a neutral reaction and low total Cd content. Grain Cd and Zn concentrations were determined with graphite atomic adsorption spectrophotometer (GFAAS) and flame atomic adsorption spectrophotometer (AAS) respectively. Wide variation of Cd content in grain was found in a range of 0.004-0.057 mg/kg, while the Zn content in a range of 10.25-30.06 mg/kg among the cultivars. Higher Cd but lower Zn concentration in grains of super rice cultivars was observed compared to the common hybrid ones. A highly significant positive linear correlation of grain Cd/Zn with grain Cd was found for super rice and common hybrid cultivars, meanwhile much higher slope for these hybrid cultivars than the reported non-hybrid cultivars was also observed. Using the limit value of the Chinese chemical guidelines for foods (MOHC and SSC, 2005), calculated potential risk of food Cd exposure with "Zn hungry" through diet intake was prominent with all the studied 110 hybrid rice cultivars, possessing high potential health problems for rice production in South China using the super rice cultivars. Breeding of genotypes of rice cultivars with low grain Cd and low Cd/Zn ratio is needed for rice production in acidic red soils where Cd bioavailability is prevalently high. PMID:19402417

  12. Competitive interactions between methane- and ammonia-oxidizing bacteria modulate carbon and nitrogen cycling in paddy soil

    NASA Astrophysics Data System (ADS)

    Zheng, Y.; Huang, R.; Wang, B. Z.; Bodelier, P. L. E.; Jia, Z. J.

    2014-06-01

    Pure culture studies have demonstrated that methanotrophs and ammonia oxidizers can both carry out the oxidation of methane and ammonia. However, the expected interactions resulting from these similarities are poorly understood, especially in complex, natural environments. Using DNA-based stable isotope probing and pyrosequencing of 16S rRNA and functional genes, we report on biogeochemical and molecular evidence for growth stimulation of methanotrophic communities by ammonium fertilization, and that methane modulates nitrogen cycling by competitive inhibition of nitrifying communities in a rice paddy soil. Pairwise comparison between microcosms amended with CH4, CH4+Urea, and Urea indicated that urea fertilization stimulated methane oxidation activity 6-fold during a 19-day incubation period, while ammonia oxidation activity was significantly suppressed in the presence of CH4. Pyrosequencing of the total 16S rRNA genes revealed that urea amendment resulted in rapid growth of Methylosarcina-like MOB, and nitrifying communities appeared to be partially inhibited by methane. High-throughput sequencing of the 13C-labeled DNA further revealed that methane amendment resulted in clear growth of Methylosarcina-related MOB while methane plus urea led to an equal increase in Methylosarcina and Methylobacter-related type Ia MOB, indicating the differential growth requirements of representatives of these genera. An increase in 13C assimilation by microorganisms related to methanol oxidizers clearly indicated carbon transfer from methane oxidation to other soil microbes, which was enhanced by urea addition. The active growth of type Ia methanotrops was significantly stimulated by urea amendment, and the pronounced growth of methanol-oxidizing bacteria occurred in CH4-treated microcosms only upon urea amendment. Methane addition partially inhibited the growth of Nitrosospira and Nitrosomonas in urea-amended microcosms, as well as growth of nitrite-oxidizing bacteria. These

  13. Growing season net ecosystem CO2 exchange of two desert ecosystems with alkaline soils in Kazakhstan

    PubMed Central

    Li, Longhui; Chen, Xi; van der Tol, Christiaan; Luo, Geping; Su, Zhongbo

    2014-01-01

    Central Asia is covered by vast desert ecosystems, and the majority of these ecosystems have alkaline soils. Their contribution to global net ecosystem CO2 exchange (NEE) is of significance simply because of their immense spatial extent. Some of the latest research reported considerable abiotic CO2 absorption by alkaline soil, but the rate of CO2 absorption has been questioned by peer communities. To investigate the issue of carbon cycle in Central Asian desert ecosystems with alkaline soils, we have measured the NEE using eddy covariance (EC) method at two alkaline sites during growing season in Kazakhstan. The diurnal course of mean monthly NEE followed a clear sinusoidal pattern during growing season at both sites. Both sites showed significant net carbon uptake during daytime on sunny days with high photosynthetically active radiation (PAR) but net carbon loss at nighttime and on cloudy and rainy days. NEE has strong dependency on PAR and the response of NEE to precipitation resulted in an initial and significant carbon release to the atmosphere, similar to other ecosystems. These findings indicate that biotic processes dominated the carbon processes, and the contribution of abiotic carbon process to net ecosystem CO2 exchange may be trivial in alkaline soil desert ecosystems over Central Asia. PMID:24455157

  14. Mitigation of arsenic contamination in irrigated paddy soils in South and South-East Asia.

    PubMed

    Brammer, Hugh

    2009-08-01

    It has recently become apparent that arsenic-contaminated groundwater used for irrigation in several countries of South and South-east Asia is adding arsenic to soils and rice, thus posing a serious threat to sustainable agricultural production and to the health and livelihoods of affected people in those countries. This paper describes the many environmental, agricultural and social factors that determine practical mitigation strategies and research needs, and describes possible mitigation measures that need to be tested. These measures include providing alternative irrigation sources, various agronomic measures, use of soil amendments, growing hyperaccumulator plants, removing contaminated soil and using alternative cooking methods. PMID:19394085

  15. Utilization of phosphorus loaded alkaline residue to immobilize lead in a shooting range soil.

    PubMed

    Yan, Yubo; Qi, Fangjie; Seshadri, Balaji; Xu, Yilu; Hou, Jiexi; Ok, Yong Sik; Dong, Xiaoli; Li, Qiao; Sun, Xiuyun; Wang, Lianjun; Bolan, Nanthi

    2016-11-01

    The alkaline residue generated from the production of soda ash using the ammonia-soda method has been successfully used in removing phosphorus (P) from aqueous solution. But the accumulation of P-containing solid after P removal is an undesirable menace to the environment. To achieve the goal of recycling, this study explored the feasibility of reusing the P loaded alkaline residue as an amendment for immobilization of lead (Pb) in a shooting range soil. The main crystalline phase and micromorphology of amendments were determined using X-ray diffraction (XRD) and scanning electron microscopy-electron dispersion spectroscopy (SEM-EDS) methods. The toxicity characteristic leaching procedure (TCLP), sequential extraction procedure, and physiologically based extraction test (PBET) were employed to evaluate the effectiveness of Pb immobilization in soil after 45 d incubation. Treatment with P loaded alkaline residue was significantly effective in reducing the TCLP and PBET extractable Pb concentrations in contrast to the untreated soil. Moreover, a positive change in the distribution of Pb fractions was observed in the treated soil, i.e., more than 60% of soil-Pb was transformed to the residual fraction compared to the original soil. On the other hand, P loaded amendments also resulted in a drastic reduction in phytoavailable Pb to the winter wheat and a mild release of P as a nutrient in treated soil, which also confirmed the improvement of soil quality. PMID:27513552

  16. Pathways and relative contributions to arsenic volatilization from rice plants and paddy soil.

    PubMed

    Jia, Yan; Huang, Hai; Sun, Guo-Xin; Zhao, Fang-Jie; Zhu, Yong-Guan

    2012-08-01

    Recent studies have shown that higher plants are unable to methylate arsenic (As), but it is not known whether methylated As species taken up by plants can be volatilized. Rice (Oryza sativa L.) plants were grown axenically or in a nonsterile soil using a two-chamber system. Arsenic transformation and volatilization were investigated. In the axenic system, uptake of As species into rice roots was in the order of arsenate (As(V)) > monomethylarsonic acid (MMAs(V)) > dimethylarsinic acid (DMAs(V)) > trimethylarsine oxide (TMAs(V)O), but the order of the root-to-shoot transport index (Ti) was reverse. Also, volatilization of trimethylarsine (TMAs) from rice plants was detected when plants were treated with TMAs(V)O but not with As(V), DMAs(V), or MMAs(V). In the soil culture, As was volatilized mainly from the soil. Small amounts of TMAs were also volatilized from the rice plants, which took up DMAs(V), MMAs(V), and TMAs(V)O from the soil solution. The addition of dried distillers grain (DDG) to the soil enhanced As mobilization into the soil solution, As methylation and volatilization from the soil, as well as uptake of different As species and As volatilization from the rice plants. Results show that rice is able to volatilize TMAs after the uptake of TMAs(V)O but not able to convert inorganic As, MMAs(V) or DMAs(V) into TMAs and that the extent of As volatilization from rice plants was much smaller than that from the flooded soil. PMID:22724924

  17. DNA-based determination of microbial biomass suitable for frozen and alkaline soil samples

    NASA Astrophysics Data System (ADS)

    Semenov, Mikhail; Blagodatskaya, Evgeniya; Kogut, Boris; Kuzyakov, Yakov

    2015-04-01

    Microbial biomass is a sensitive indicator of changes due to soil management, long before other basic soil measures such as Corg or Ntot. Improvement of methods for determination of microbial biomass still remains relevant, and these methods should be correctly applicable for the soil samples being in various state. This study was designed to demonstrate the applicability of DNA-based determination of microbial biomass under conditions when the common basic approaches, namely chloroform fumigation-extraction (CFE) and substrate-induced respiration (SIR), are restricted by certain soil properties, experimental designs or research needs, e.g. in frozen, alkaline or carbonaceous soils. We compared microbial biomass determined by CFE, SIR and by DNA approaches in the range of neutral and slightly alkaline Chernozem and alkaline Calcisol of semi-arid climate. The samples of natural and agricultural ecosystems were taken throughout the soil profile from long-term static field experiments in the European part of Russia. Extraction and subsequent quantification of dsDNA revealed a strong agreement with SIR and CFE when analyzing the microbial biomass content in soils with pH below 8. The conversion factors (FDNA) from dsDNA to SIR-Cmic (5.10) and CFE-Cmic (4.41) were obtained by testing a range of the soil samples down to 1.5 m depth and indicated a good reproducibility of DNA-based estimations. In alkaline soils (pH > 8), CO2 retention due to alkaline pH and exchange with carbonates resulted in a strong underestimation of soil microbial biomass by SIR or even in the absence of any CO2 emission, especially at low absolute values of microbial biomass in subsoil. Correction of CO2 efflux by theoretical retention pH-dependent factors caused overestimation of SIR-biomass. In alkaline conditions, DNA extraction proved to be a reliable alternative for microbial biomass determination. Moreover, the DNA-based approach can serve as an excellent alternative enabling correct

  18. Paddy-field contamination with 134Cs and 137Cs due to Fukushima Dai-ichi Nuclear Power Plant accident and soil-to-rice transfer coefficients.

    PubMed

    Endo, Satoru; Kajimoto, Tsuyoshi; Shizuma, Kiyoshi

    2013-02-01

    The transfer coefficient (TF) from soil to rice plants of (134)Cs and (137)Cs in the form of radioactive deposition from the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March 2011 was investigated in three rice paddy fields in Minami-Soma City. Rice crops were planted in the following May and harvested at the end of September. Soil cores of 30-cm depth were sampled from rice-planted paddy fields to measure (134)Cs and (137)Cs radioactivity at 5-cm intervals. (134)Cs and (137)Cs radioactivity was also measured in rice ears (rice with chaff), straws and roots. The rice ears were subdivided into chaff, brown rice, polished rice and rice bran, and the (134)Cs and (137)Cs radioactivity concentration of each plant part was measured to calculate the respective TF from the soil. The TF of roots was highest at 0.48 ± 0.10 in the field where the (40)K concentration in the soil core was relatively low, in comparison with TF values of 0.31 and 0.38 in other fields. Similar trends could be found for the TF of whole rice plants, excluding roots. The TF of rice ears was relatively low at 0.019-0.026. The TF of chaff, rice bran, brown rice and polished rice was estimated to be 0.049, 0.10-0.16, 0.013-0.017 and 0.005-0.013, respectively. PMID:23103577

  19. Dynamics of the microbial community and Fe(III)-reducing and dechlorinating microorganisms in response to pentachlorophenol transformation in paddy soil.

    PubMed

    Chen, Manjia; Liu, Chengshuai; Chen, Pengcheng; Tong, Hui; Li, Fangbai; Qiao, Jiangtao; Lan, Qing

    2016-07-15

    Soil microorganisms play crucial roles in the fates of pollutants, and understanding the behaviour of these microorganisms is critical for the bioremediation of PCP-contaminated soil. However, shifts remain unclear in the community structure and Fe(III)-reducing and dechlorinating microorganisms during PCP transformation processes, especially during the stages from the lag to the dechlorination phase and from the dechlorination to the stationary phase. Here, a set of lab-scale experiments was performed to investigate the microbial community dynamics accompanying PCP transformation in paddy soil. 19μM of PCP was biotransformed completely in 10days for all treatments. T-RFLP analysis of the microbial community confirmed that Veillonellaceae and Clostridium sensu stricto were the dominant groups during PCP transformation, and the structures of the microbial communities changed due to the degree of biotransformation and the addition of lactate and AQDS. However, similar temporal dynamics of the microbial communities were obtained among all treatments. Furthermore, as revealed by quantitative PCR, the dynamics of Fe(III)-reducing and dechlorinating microorganisms, including Geobacter sp., Shewanella sp., and Dehalobacter sp., were consistent with the transformation kinetics of PCP, suggesting the critical roles played by these microorganisms in PCP transformation. These findings are valuable for making predictions of and proposing methods for the microbial detoxification of residual organochlorine pesticides in paddy soil. PMID:27017395

  20. Effects of 10-Year Management Regimes on the Soil Seed Bank in Saline-Alkaline Grassland

    PubMed Central

    Ma, Hongyuan; Yang, Haoyu; Liang, Zhengwei; Ooi, Mark K. J.

    2015-01-01

    Background Management regimes for vegetation restoration of degraded grasslands can significantly affect the process of ecological succession. However, few studies have focused on variation in the soil seed bank during vegetation restoration under different management regimes, especially in saline-alkaline grassland habitats. Our aim was to provide insights into the ecological effects of grassland management regimes on soil seed bank composition and vegetation establishment in mown, fenced, transplanted and natural grassland sites, all dominated by the perennial rhizomatous grass Leymus chinensis. Methodology We studied species composition and diversity in both the soil seed bank and aboveground vegetation in differently managed grasslands in Northeast China. An NMDS (nonmetric multidimensional scaling) was used to evaluate the relationship between species composition, soil seed banks, aboveground vegetation and soil properties. Principal Findings Fenced and mown grassland sites had high density and species richness in both the soil seed bank and aboveground vegetation. The Transplanted treatment exhibited the highest vegetation growth and seed production of the target species L. chinensis. Seeds of L. chinensis in the soil occurred only in transplanted and natural grassland. Based on the NMDS analysis, the number of species in both the soil seed bank and aboveground vegetation were significantly related to soil Na+, Cl-, RSC (residual sodium carbonate), alkalinity, ESP (exchangeable sodium percentage) and AP (available phosphorus). Conclusions Soil seed bank composition and diversity in the saline-alkaline grassland were significantly affected by the management regimes implemented, and were also significantly related to the aboveground vegetation and several soil properties. Based on vegetative growth, reproductive output and maintenance of soil seed bank, the transplanting was identified as the most effective method for relatively rapid restoration of the target

  1. Effect of nitrogen fertilizer and/or rice straw amendment on methanogenic archaeal communities and methane production from a rice paddy soil.

    PubMed

    Bao, Qiongli; Huang, Yizong; Wang, Fenghua; Nie, Sanan; Nicol, Graeme W; Yao, Huaiying; Ding, Longjun

    2016-07-01

    Nitrogen fertilization and returning straw to paddy soil are important factors that regulate CH4 production. To evaluate the effect of rice straw and/or nitrate amendment on methanogens, a paddy soil was anaerobically incubated for 40 days. The results indicated that while straw addition increased CH4 production and the abundances of mcrA genes and their transcripts, nitrate amendment showed inhibitory effects on them. The terminal restriction fragment length polymorphism (T-RFLP) analysis based on mcrA gene revealed that straw addition obviously changed methanogenic community structure. Based on mcrA gene level, straw-alone addition stimulated Methanosarcinaceaes at the early stage of incubation (first 11 days), but nitrate showed inhibitory effect. The relative abundance of Methanobacteriaceae was also stimulated by straw addition during the first 11 days. Furthermore, Methanosaetaceae were enriched by nitrate-alone addition after 11 days, while Methanocellaceae were enriched by nitrate addition especially within the first 5 days. The transcriptional methanogenic community indicated more dynamic and complicated responses to straw and/or nitrate addition. Based on mcrA transcript level, nitrate addition alone resulted in the increase of Methanocellaceae and the shift from Methanosarcinaceae to Methanosaetaceae during the first 5 days of incubation. Straw treatments increased the relative abundance of Methanobacteriaceae after 11 days. These results demonstrate that nitrate addition influences methanogens which are transcriptionally and functionally active and can alleviate CH4 production associated with straw amendment in paddy soil incubations, presumably through competition for common substrates between nitrate-utilizing organisms and methanogens. PMID:26923143

  2. Residues of 14C-metsulfuron-methyl in Chinese Paddy soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Metsulfuron-methyl is widely used for controlling many annual grasses and broadleaf weeds in cereal crops. Nonetheless, increasing evidence has demonstrated that even extremely low levels of metsulfuron-methyl residues in soil were toxic to the subsequent crops or non-target organisms. The behavior ...

  3. Soil organic carbon (SOC) accumulation in rice paddies under long-term agro-ecosystem experiments in southern China - VI. Changes in microbial community structure and respiratory activity

    NASA Astrophysics Data System (ADS)

    Liu, D.; Liu, X.; Liu, Y.; Li, L.; Pan, G.; Crowley, D.; Tippkötter, R.

    2011-02-01

    Biological stabilization within accumulated soil organic carbon (SOC) has not been well understood, while its role in physical and chemical protection as well as of chemical recalcitrance had been addressed in Chinese rice paddies. In this study, topsoil samples were collected and respiratory activity measured in situ following rice harvest under different fertilization treatments of three long-term experimental sites across southern China in 2009. The SOC contents, microbial biomass carbon (SMBC) and nitrogen (SMBN) were analysed using chemical digestion and microbial community structure assessment via clony dilute plate counting methods. While SOC contents were consistently higher under compound chemical fertilization (Comp-Fert) or combined organic and inorganic fertilization (Comb-Fert) compared to N fertilization only (N-Fert), there was significantly higher fungal-bacterial ratio under Comb-Fert than under N-Fert and Comp-Fert. When subtracting the background effect under no fertilization treatment (Non-Fert), the increase both in SMBC and SMBN under fertilization treatment was found very significantly correlated to the increase in SOC over controls across the sites. Also, the ratio of culturable fungal to bacterial population numbers (F/B ratio) was well correlated with soil organic carbon contents in all samples across the sites studied. SOC accumulation favoured a build-up the microbial community with increasing fungal dominance in the rice paddies under fertilization treatments. While soil respiration rates were high under Comb-Fert as a result of enhanced microbial community build-up, the specific soil respiratory activity based on microbial biomass carbon was found in a significantly negatively correlation with the SOC contents for overall samples. Thus, a fungal-dominated microbial community seemed to slow SOC turnover, thereby favouring SOC accumulation under Comp-Fert or under Comb-Fert in the rice paddies. Therefore, the biological stabilization

  4. Interactive effects of straw-derived biochar and N fertilization on soil C storage and rice productivity in rice paddies of Northeast China.

    PubMed

    Sui, Yanghui; Gao, Jiping; Liu, Caihong; Zhang, Wenzhong; Lan, Yu; Li, Shuhang; Meng, Jun; Xu, Zhengjin; Tang, Liang

    2016-02-15

    Impacts of biochar on greenhouse gas emissions and C sequestration in agricultural soils have been considered as the key to mitigate climate change. There is limited knowledge regarding the effects of rice straw-derived biochar and interaction with N fertilization on soil C sequestration and rice productivity in fertile paddy fields. A 2-year (2013 and 2014) consecutive field trial was performed using straw treatment (5.05 t ha(-1)) and biochar amendment (0, 1.78, 14.8 and 29.6 t ha(-1)) with or without urea application in a rice paddy in Northeast China. A super high yielding rice variety (Oryza sativa L. subsp. Japonica cv. 'Shennong 265') was cultivated with permanent flooding. Results showed that biochar amendments significantly decreased CH4 emissions relative to straw treatment irrespective of N fertilization, especially in N-fertilized soils with 1.78 t ha(-1) biochar. There were no differences in CO2 emissions with respect to biochar amendments, except for 14.8 t ha(-1) biochar with N fertilization. Straw treatment had the highest global warming potential over a 100-year time frame, which was nearly 1.5 times that of 14.8 t ha(-1) biochar amendment without N fertilization. Biochar addition increased total soil C by up to 5.75 mg g(-1) and 11.69 mg g(-1) (with 14.8 and 29.6 t ha(-1) biochar, respectively), whereas straw incorporation increased this value by only 3.92 mg g(-1). The aboveground biomass of rice in biochar-amended soils increased to varying degrees compared with that in straw-treated soils. However, biochar application had no effects on rice yield, regardless of N fertilization. This study indicated that transforming straw to biochar was more stabilized and more suitable to mitigate greenhouse gas emissions and increase C storage in agriculture soils in Northeast China. PMID:26657366

  5. [Effect of carbon substrate concentration on N2, N2O, NO, CO2, and CH4 emissions from a paddy soil in anaerobic condition].

    PubMed

    Chen, Nuo; Liao, Ting-ting; Wang, Rui; Zheng, Xun-hua; Hu, Rong-gui; Butterbach-Bahl, Klaus

    2014-09-01

    Understanding the effects of carbon and nitrogen substrates concentrations on the emissions of denitrification gases including nitrogen (N2) , nitrous oxide (N2O) and nitric oxide (NO), carbon dioxide (CO2) and methane (CH4) from anaerobic paddy soils is believed to be helpful for development of greenhouse gas mitigation strategies. Moreover, understanding the quantitative dependence of denitrification products compositions on carbon substrate concentration could provide some key parameters or parameterization scheme for developing process-oriented model(s) of nitrogen transformation. Using a silt loam soil collected from a paddy field, we investigated the influence of carbon substrate concentration on the emissions of the denitrification gases, CO2 and CH4 from anaerobically incubated soils by setting two treatments: control (CK) with initial soil nitrate and dissolved organic carbon (DOC) concentrations of ~ 50 mg.kg-1 and -28 mg kg-1 , respectively; and DOC added (C + ) with initial soil nitrate and DOC concentrations of ~50 mg.kg-1 and ~300 mg.kg-1 , respectively. The emissions of denitrification gases, CO2 and CH4, as well as concentrations of carbon and nitrogen substrates for each treatment were dynamically measured, using the gas-flow-soil-core technique and a paralleling substrate monitoring system. The results showed that CH4 emission was not observed in CK treatment while observed in C treatment. Aggregate emission of greenhouse gases for C + treatment was significantly higher comparing with the CK treatment (P <0. 01). The mass fractions of NO, N20 and N2 emissions in total nitrogen gases emissions were approximately 9% , 35% and 56% for CK treatment, respectively; and approximately 31% , 50% and 19% for C+ treatment, respectively, with significant differences between these two treatments (P < 0.01). The results indicated that carbon substrate concentrations can significantly change the composition of nitrogen gas emissions. The results also implicated

  6. Comparison of the spectroscopic speciation and chemical fractionation of chromium in contaminated paddy soils.

    PubMed

    Hsu, Liang-Ching; Liu, Yu-Ting; Tzou, Yu-Min

    2015-10-15

    Sequential extraction has been widely used to classify metal species in soils and sediments; however, the lack of selectivity in extraction reagents may lead to the misinterpretation of metal speciation. In this study, we used X-ray absorption near edge structure (XANES) spectroscopy to classify Cr species based on its molecular form. These results complement the conventional Cr fractionation derived from the Tessier extraction method. The linear combination fitting (LCF) for the Cr-XANES spectra indicated that the Cr species in the soils could generally be described as Cr(III) sorbed on ferrihydrite (Cr-FH), Cr(III) complexed with humic acid (Cr-HA), and precipitated Cr. While the sum of the adsorbed Cr(III) and Cr(III)/Fe coprecipitates showed a nearly 1:1 relationship with reducible Cr, the total of Cr precipitates and organic Cr also followed the same trend with oxidizable Cr. This result indicated that there might be a underestimation in the reducible fraction as pure Cr(III) precipitates associated with surfaces of Fe minerals would not be extracted in the reducible process. Instead, such pure Cr(III) precipitates were dissolved during the oxidizable process, resulting in a overestimation in the fractionation of organic-related Cr. PMID:25935296

  7. Effects of manure and mineral fertilization strategies on soil antibiotic resistance gene levels and microbial community in a paddy-upland rotation system.

    PubMed

    Lin, Hui; Sun, Wanchun; Zhang, Zulin; Chapman, Stephen J; Freitag, Thomas E; Fu, Jianrong; Zhang, Xin; Ma, Junwei

    2016-04-01

    This work investigated the responses of antibiotic resistance genes (ARGs) and the soil microbial community in a paddy-upland rotation system to mineral fertilizer (NPK) and different application dosages of manure combined with NPK. The occurrence of five tetracycline ARGs (tetA, tetB, tetC, tetG and tetW), two sulfonamide ARGs (sul1 and sul2) and one genetic element (IntI1) was quantified. NPK application showed only slight or no impact on soil ARGs abundances compared with the control without fertilizer. Soil ARGs abundances could be increased by manure-NPK application but was related to manure dosage (2250-9000 kg ha(-1)). Principal component analysis (PCA) showed that the soil ARG profile of the treatment with 9000 kg ha(-1) manure separated clearly from the other treatments; the ARGs that contributed most to the discrimination of this treatment were tetA, tetG, tetW, sul1, sul2 and IntI1. Community level physiological profile (CLPP) analysis showed that increasing manure dosage from 4500 kg ha(-1) to 9000 kg ha(-1) induced a sharp increase in almost all of the detected ARGs but would not change the microbial community at large. However, 9000 kg ha(-1) manure application produced a decline in soil microbial activity. Determination of antibiotics and heavy metals in soils suggested that the observed bloom of soil ARGs might associate closely with the accumulation of copper and zinc in soil. PMID:26774780

  8. Clonal Integration Enhances the Performance of a Clonal Plant Species under Soil Alkalinity Stress

    PubMed Central

    Sun, Juanjuan; Chen, Jishan; Zhang, Yingjun

    2015-01-01

    Clonal plants have been shown to successfully survive in stressful environments, including salinity stress, drought and depleted nutrients through clonal integration between original and subsequent ramets. However, relatively little is known about whether clonal integration can enhance the performance of clonal plants under alkalinity stress. We investigated the effect of clonal integration on the performance of a typical rhizomatous clonal plant, Leymus chinensis, using a factorial experimental design with four levels of alkalinity and two levels of rhizome connection treatments, connected (allowing integration) and severed (preventing integration). Clonal integration was estimated by comparing physiological and biomass features between the rhizome-connected and rhizome-severed treatments. We found that rhizome-connected treatment increased the biomass, height and leaf water potential of subsequent ramets at highly alkalinity treatments but did not affect them at low alkalinity treatments. However, rhizome-connected treatment decreased the root biomass of subsequent ramets and did not influence the photosynthetic rates of subsequent ramets. The biomass of original ramets was reduced by rhizome-connected treatment at the highest alkalinity level. These results suggest that clonal integration can increase the performance of clonal plants under alkalinity stress. Rhizome-connected plants showed dramatically increased survival of buds with negative effects on root weight, indicating that clonal integration influenced the resource allocation pattern of clonal plants. A cost-benefit analysis based on biomass measures showed that original and subsequent ramets significantly benefited from clonal integration in highly alkalinity stress, indicating that clonal integration is an important adaptive strategy by which clonal plants could survive in local alkalinity soil. PMID:25790352

  9. In situ electrokinetic remediation of As-, Cu-, and Pb-contaminated paddy soil using hexagonal electrode configuration: a full scale study.

    PubMed

    Jeon, Eun-Ki; Jung, Ji-Min; Kim, Woo-Seung; Ko, Sung-Hwan; Baek, Kitae

    2015-01-01

    We investigated the in situ applicability of the electrokinetic process with a hexagonal electrode configuration in order to remediate arsenic (As)-, copper (Cu)-, and lead (Pb)-contaminated paddy rice field soil at a field scale (width 17 m, length 12.2 m, and depth 1.6 m). An iron electrode was used in order to prevent the severe acidification of the soil near the anode. We selected ethylenediaminetetraacetic acid (EDTA) as a pursing electrolyte to enhance the extraction of Cu and Pb. The system removed 44.4% of the As, 40.3% of the Cu, and 46.6% of the Pb after 24 weeks of operation. Fractionation analysis showed that the As bound to amorphous ion (Fe) and aluminum (Al) oxyhydroxides was changed into a form of As specifically bound. In the case of Cu and Pb, the fraction bound to Fe-Mn oxyhydroxide primarily decreased. The EDTA formed negatively charged complexes with Cu and Pb, and those complexes were transported toward the anode. The energy consumption was very low compared to that on a small scale because there was less energy consumption due to Joule heating. These results show that the in situ electrokinetic process could be applied in order to remediate paddy rice fields contaminated with multiple metals. PMID:25103944

  10. Hexavalent uranium diffusion into soils from concentrated acidic and alkaline solutions

    SciTech Connect

    Tokunaga, Tetsu K.; Wan, Jiamin; Pena, Jasquelin; Sutton, Stephen R.; Newville, Matthew

    2004-03-29

    Uranium contamination of soils and sediments often originates from acidic or alkaline waste sources, with diffusion being a major transport mechanism. Measurements of U(VI) diffusion from initially pH 2 and pH 11 solutions into a slightly alkaline Altamont soil and a neutral Oak Ridge soil were obtained through monitoring uptake from boundary reservoirs and from U concentration profiles within soil columns. The soils provided pH buffering, resulting in diffusion at nearly constant pH. Micro x-ray absorption near edge structure spectra confirmed that U remained in U(VI) forms in all soils. Time trends of U(VI) depletion from reservoirs, and U(VI) concentration profiles within soil columns yielded K{sub d} values consistent with those determined in batch tests at similar concentrations ({approx} 1 mM), and much lower than values for sorption at much lower concentrations (nM to {mu}M). These results show that U(VI) transport at high concentrations can be relatively fast at non-neutral pH, with negligible surface diffusion, because of weak sorption.

  11. Root-Derived Short-Chain Suberin Diacids from Rice and Rape Seed in a Paddy Soil under Rice Cultivar Treatments

    PubMed Central

    Ji, Haishi; Ding, Yuanjun; Liu, Xiaoyu; Li, Lianqing; Zhang, Dengxiao; Li, Zichuan; Sun, Jingling; Lashari, Muhammad Siddique; Joseph, Stephen; Meng, Yuanduo; Kuzyakov, Yakov; Pan, Genxing

    2015-01-01

    Suberin-derived substituted fatty acids have been shown to be potential biomarkers for plant-derived carbon (C) in soils across ecosystems. Analyzing root derived suberin compounds bound in soil could help to understand the root input into a soil organic carbon pool. In this study, bound lipids were extracted and identified in root and topsoil samples. Short-chain suberin diacids were quantified under rice (Oryza sativa L.) and rape (Brassica campestris) rotations with different cultivar combinations in a Chinese rice paddy. After removal of free lipids with sequential extraction, the residual bound lipids were obtained with saponification and derivatization before analysis using gas chromatography–mass spectrometry (GC-MS). Diacids C16 and C18 in bound lipids were detected both in rice and rape root samples, while diacids C20 and C22 were detected only in rape root samples. Accordingly, diacids were quantified in both rhizosphere and bulk soil (0–15 cm). The amount of total root-derived diacids in bulk soil varied in a range of 5.6–9.6 mg/kg across growth stages and crop seasons. After one year-round rice-rape rotation, root-derived suberin diacids were maintained at a level of 7–9 mg/kg in bulk soil; this was higher under a super rice cultivar LY than under a hybrid cultivar IIY. While concentrations of the analyzed diacids were generally higher in rhizosphere than in bulk soil, the total diacid (DA) concentration was higher at the time of rape harvest than at rice harvest, suggesting that rape roots made a major contribution to the preservation of diacids in the paddy. Moreover, the net change in the concentration and the ratios of C16:0 DA to C18:1 DA, and of C16:0 DA to C18:0 DA, over a whole growing season, were greater under LY than under IIY, though there was no difference between cultivars within a single growth stage. Overall, total concentration of root-derived suberin diacids was found to be positively correlated to soil organic carbon

  12. Root-Derived Short-Chain Suberin Diacids from Rice and Rape Seed in a Paddy Soil under Rice Cultivar Treatments.

    PubMed

    Ji, Haishi; Ding, Yuanjun; Liu, Xiaoyu; Li, Lianqing; Zhang, Dengxiao; Li, Zichuan; Sun, Jingling; Lashari, Muhammad Siddique; Joseph, Stephen; Meng, Yuanduo; Kuzyakov, Yakov; Pan, Genxing

    2015-01-01

    Suberin-derived substituted fatty acids have been shown to be potential biomarkers for plant-derived carbon (C) in soils across ecosystems. Analyzing root derived suberin compounds bound in soil could help to understand the root input into a soil organic carbon pool. In this study, bound lipids were extracted and identified in root and topsoil samples. Short-chain suberin diacids were quantified under rice (Oryza sativa L.) and rape (Brassica campestris) rotations with different cultivar combinations in a Chinese rice paddy. After removal of free lipids with sequential extraction, the residual bound lipids were obtained with saponification and derivatization before analysis using gas chromatography-mass spectrometry (GC-MS). Diacids C16 and C18 in bound lipids were detected both in rice and rape root samples, while diacids C20 and C22 were detected only in rape root samples. Accordingly, diacids were quantified in both rhizosphere and bulk soil (0-15 cm). The amount of total root-derived diacids in bulk soil varied in a range of 5.6-9.6 mg/kg across growth stages and crop seasons. After one year-round rice-rape rotation, root-derived suberin diacids were maintained at a level of 7-9 mg/kg in bulk soil; this was higher under a super rice cultivar LY than under a hybrid cultivar IIY. While concentrations of the analyzed diacids were generally higher in rhizosphere than in bulk soil, the total diacid (DA) concentration was higher at the time of rape harvest than at rice harvest, suggesting that rape roots made a major contribution to the preservation of diacids in the paddy. Moreover, the net change in the concentration and the ratios of C16:0 DA to C18:1 DA, and of C16:0 DA to C18:0 DA, over a whole growing season, were greater under LY than under IIY, though there was no difference between cultivars within a single growth stage. Overall, total concentration of root-derived suberin diacids was found to be positively correlated to soil organic carbon concentration

  13. Characterization of commercial iron chelates and their behavior in an alkaline and calcareous soil.

    PubMed

    Cantera, Rodrigo G; Zamarreño, Angel M; García-Mina, José M

    2002-12-18

    Iron deficiency is a common problem for many plants grown in alkaline and calcareous soils. To correct this problem, iron is supplied to plants as chelates. Several iron chelates are sold under diverse trademarks with different characteristics. This work evaluated 18 commercial products containing the most representative chelated iron sources used in agricultural practice in Spain when the study was done, namely the ferric chelates of EDDHA, EDDHMA, EDDCHA, EDDHSA, EDTA, and DTPA. The chelates were comprehensively characterized and quantitated by several techniques, including several chromatographic methods. Iron and chelate dynamics in soil were also studied in a model alkaline and calcareous soil. Results indicate that, in this model soil, among the different iron compounds studied only FeEDDHA and analogues have the capacity to maintain soluble iron in soil solution over time. These results are in agreement with general experience under field conditions. Furthermore, among the different ortho-ortho isomers of FeEDDHA's, FeEDDHSA and FeEDDCHA showed greater capacity than FeEDDHA and FeEDDHMA to maintain the chelated iron in soil solution over time. PMID:12475278

  14. Quantification and modelling of water flow in rain-fed paddy fields in NE Thailand: Evidence of soil salinization under submerged conditions by artesian groundwater

    NASA Astrophysics Data System (ADS)

    Hammecker, Claude; Maeght, Jean-Luc; Grünberger, Olivier; Siltacho, Siwaporn; Srisruk, Kriengsak; Noble, Andrew

    2012-08-01

    SummaryWater flow and solute transport in soils forms an essential part in many groundwater hydrology studies. This is especially true for Northeast Thailand, where the agricultural land is affected by the soil salinity, which is a widespread and an increasing phenomenon affecting 25% of the agricultural land. Salinization appears as scattered discrete patches of 10-100 m2 in the lowlands, illustrated by white efflorescences during the dry season and bare soil during the cropping season. A field study was undertaken in farm plots to measure the water flow and solute transport within the soil surface and the vadose zone, both inside and outside a saline patch. The water flow was measured on the soil surface with lysimeters and infiltration rings, and was derived in the soil from the hydraulic gradients measured with tensiometers placed at different depths. The salt transport was evaluated with water traps also placed at different depths, where the soil water's electrical conductivity was measured throughout the rainy season. Field study results demonstrated that the accumulation of saline solutions in rain fed paddy fields, occurred mainly during the rainy season while the soil surface remained flooded. During this period the saline water table rose towards the soil surface independently of infiltration into the soil. It happened in specific places where the compacted soil layer, generally ubiquitous in the area at a depth of 40-50 cm, is interrupted. Therefore salinity appeareds in discret points as patches. Artesian upward flow already described in this area (Haworth et al., 1966; Williamson et al., 1989; Imaizumi et al., 2002) is most probably responsible for this water table rise, thereby affecting crop productivity. Numerical modelling of water flow using HYDRUS-3D further supported these results and showed that managing the depth of flooding within the plot can significantly reduce the outbreak of these saline plumes.

  15. Effects of the Application of Digestates from Wet and Dry Anaerobic Fermentation to Japanese Paddy and Upland Soils on Short-Term Nitrification

    PubMed Central

    Sawada, Kozue; Toyota, Koki

    2015-01-01

    Wet and dry anaerobic fermentation processes are operated for biogas production from organic matter, resulting in wet and dry digestates as by-products, respectively. The application of these digestates to soil as fertilizer has increased in recent years. Therefore, we herein compared the effects of applying wet digestates (pH 8.2, C/N ratio 4.5), dry digestates (pH 8.8, C/N ratio 23.4), and a chemical fertilizer to Japanese paddy and upland soils on short-term nitrification under laboratory aerobic conditions. Chloroform-labile C, an indicator of microbial biomass, was only minimally affected by these applications, indicating that a small amount of labile N was immobilized by microbes. All applications led to rapid increases in NO3 -N contents in both soils, and ammonia-oxidizing bacteria, but not archaea may play a critical role in net nitrification in the amended soils. The net nitrification rates for both soils were the highest after the application of dry digestates, followed by wet digestates and then the chemical fertilizer in order of decreasing soil pH. These results suggest that the immediate effects of applying digestates, especially dry digestates with the highest pH, on nitrate leaching need to be considered when digestates are used as alternative fertilizers. PMID:25740173

  16. Zoom in new insights of potential microbial control of N and CH4 gaseous losses induced by different agricultural practices in temperate paddy soils

    NASA Astrophysics Data System (ADS)

    Cucu, Maria Alexandra; Bardi, Laura; Said-Pullicino, Daniel; Sacco, Dario; Celi, Luisella; Gorra, Roberta

    2016-04-01

    Rice is the world's single most important food crop and a primary food source for more than a third of the world's population. Usually, rice is grown in flooded paddies that result in anoxic soil conditions throughout a major part of the cropping period. Redox processes in wetland ecosystems combined with crop residue incorporation play an important role in element cycling and ecological functions of rice ecosystems. Microbial communities are at the basis of the functioning of wetlands and the ecosystem services they provide. Agronomic management practices adopted in rice paddies may have important effects on microbial biomass functionality and interactions, but these are largely unknown in situ. They mediate important processes such as nitrification, anaerobic ammonia oxidation (Anammox), denitrification, and methanogenesis that regulate ecosystem functioning and control greenhouse gases (GHG) emissions. Therefore, it is crucial to comprehend the microbial control of these processes as a function of different crop residue and water management practices. Here we highlight recent findings based on the exploration of microbial functional genes as biogeochemical indicators. Through both lab and field experiments and by linking to GHG emissions and soil chemistry, we evaluated niche differentiation between microbial communities and the crucial role of agronomic management in regulating their potential functionality. Recent studies showed a high abundance of both 16S communities, bacteria and archaea, confirming the high relevance of archaeal mediated processes in rice ecosystems. Our results unravel the complete denitrification as key player in regulating major nitrogen (N) fluxes in fertilized paddies. In a laboratory experiment this process was shown to be driven by both archaea and bacteria harboring nosZ gene, but especially by archaea in the absence of straw. In addition, part of the immobilized N was attributed to nitrous oxide (N2O) reducing archaea, suggesting

  17. [Effect of long-term application of nitrogen fertilizer on the diversity of nitrifying genes (amoA and hao) in paddy soil].

    PubMed

    Chen, Chun-lan; Wu, Min-na; Wei, Wen-xue

    2011-05-01

    The aim of this study was to determine the effect of long-term (16 years) application of nitrogen fertilizer on the diversity of nitrifying genes (amoA and hao) in paddy soil on the basis of long-term paddy field experimental station (started in 1990) located in Taoyuan, with the molecular approaches of PCR, constructing libraries and sequencing. The fertilizer was urea and no fertilizer was as control. The Shannon index showed that long-term application of nitrogen fertilizer made the diversity of amoA gene descend while no effect on the diversity of hao gene. The LIBSHUFF statistical analyses demonstrated that both amoA and hao libraries of CK and N treatments were significantly different from each other and the rarefaction curves of libraries failed to meet the plateaus indicating that there were lots kinds of genes haven't been detected. The results of blasting with GenBank and the phylogenetic tree showed that the amoA genes detected in our study had a similarity with the uncultured gene of amoA, which showed some similar to Nitrosospira. Otherwise, the hao genes cloned showed a relationship to the genes of cultured bacteria such as Silicibacteria, Nitrosospira and Methylococcus, and the hao genes found in the N treatment dominated in alpha-Proteobacteria. These results suggest that long-term fertilization of nitrogen had significant impacts on the diversity or community of amoA and hao genes. PMID:21780610

  18. Arsenic fractionation and bioaccessibility in two alkaline Texas soils incubated with sodium arsenate.

    PubMed

    Datta, Rupali; Makris, Konstantinos C; Sarkar, Dibyendu

    2007-05-01

    Elevated arsenic (As) concentrations in urban soils with prolonged arsenical pesticide application history have increased the risk associated with accidental hand-to-mouth soil ingestion by children. Earlier work by the authors suggested that the conservative statement of 100% As bioaccessibility in soils was not valid for a set of acidic soils incubated with sodium arsenate. In this study, two alkaline Texas soils incubated with a commonly used As pesticide (sodium arsenate) were evaluated for their potential in reducing soil As bioaccessibility. The objective of this study was to evaluate the effects of incubation time and As load on soil As fractionation and bioaccessibility. Soils were subjected to a sequential As fractionation scheme, and bioaccessible As was quantified using an in vitro stomach phase test. Results showed a reduction in the water-soluble As fraction with incubation time (after 4 months), which remained unchanged after 12 months. This reduction with time was accompanied by an increase in the NaOH- and H(2)SO(4)-extractable As fractions, suggesting As sorption by amorphous Fe/Al hydroxides and/or Ca/Mg compounds, respectively. Organic/sulfides-bound As increased with incubation time after 12 months but not after 4 months of incubation. The aging effect was also observed with the amount of bioaccessible As at all As loads, showing significant positive correlations with the water-extractable and exchangeable As fractions. Bioaccessible As concentrations even after 12 months of incubation were not significantly reduced, suggesting that natural attenuation might prove inadequate to control As bioaccessibility in these alkaline soils. PMID:17387422

  19. Diversity and activity of methanotrophs in alkaline soil from a Chinese coal mine.

    PubMed

    Han, Bing; Chen, Yin; Abell, Guy; Jiang, Hao; Bodrossy, Levente; Zhao, Jiangang; Murrell, J Colin; Xing, Xin-Hui

    2009-11-01

    Culture-independent molecular biological techniques, including 16S rRNA gene and functional gene clone libraries and microarray analyses using pmoA (encoding a key subunit of particulate methane monooxygenase), were applied to investigate the methanotroph community structure in alkaline soil from a Chinese coal mine. This environment contained a high diversity of methanotrophs, including the type II methanotrophs Methylosinus/Methylocystis, type I methanotrophs related to Methylobacter/Methylosoma and Methylococcus, and a number of as yet uncultivated methanotrophs. In order to identify the metabolically active methane-oxidizing bacteria from this alkaline environment, DNA stable isotope probing (DNA-SIP) experiments using (13)CH(4) were carried out. This showed that both type I and type II methanotrophs were active, together with methanotrophs related to Methylocella, which had previously been found only in acidic environments. Methylotrophs, including Methylopila and Hyphomicrobium, were also detected in soil DNA and after DNA-SIP experiments. DNA sequence information on the most abundant, active methanotrophs in this alkaline soil will facilitate the design of oligonucleotide probes to monitor enrichment cultures when isolating key alkaliphilic methanotrophs from such environments. PMID:19515201

  20. Biochar affects soil organic matter cycling and microbial functions but does not alter microbial community structure in a paddy soil.

    PubMed

    Tian, Jing; Wang, Jingyuan; Dippold, Michaela; Gao, Yang; Blagodatskaya, Evgenia; Kuzyakov, Yakov

    2016-06-15

    The application of biochar (BC) in conjunction with mineral fertilizers is one of the most promising management practices recommended to improve soil quality. However, the interactive mechanisms of BC and mineral fertilizer addition affecting microbial communities and functions associated with soil organic matter (SOM) cycling are poorly understood. We investigated the SOM in physical and chemical fractions, microbial community structure (using phospholipid fatty acid analysis, PLFA) and functions (by analyzing enzymes involved in C and N cycling and Biolog) in a 6-year field experiment with BC and NPK amendment. BC application increased total soil C and particulate organic C for 47.4-50.4% and 63.7-74.6%, respectively. The effects of BC on the microbial community and C-cycling enzymes were dependent on fertilization. Addition of BC alone did not change the microbial community compared with the control, but altered the microbial community structure in conjunction with NPK fertilization. SOM fractions accounted for 55% of the variance in the PLFA-related microbial community structure. The particulate organic N explained the largest variation in the microbial community structure. Microbial metabolic activity strongly increased after BC addition, particularly the utilization of amino acids and amines due to an increase in the activity of proteolytic (l-leucine aminopeptidase) enzymes. These results indicate that microorganisms start to mine N from the SOM to compensate for high C:N ratios after BC application, which consequently accelerate cycling of stable N. Concluding, BC in combination with NPK fertilizer application strongly affected microbial community composition and functions, which consequently influenced SOM cycling. PMID:26974565

  1. Fenton process-affected transformation of roxarsone in paddy rice soils: Effects on plant growth and arsenic accumulation in rice grain.

    PubMed

    Qin, Junhao; Li, Huashou; Lin, Chuxia

    2016-08-01

    Batch and greenhouse experiments were conducted to examine the effects of Fenton process on transformation of roxarsone in soils and its resulting impacts on the growth of and As uptake by a rice plant cultivar. The results show that addition of Fenton reagent markedly accelerated the degradation of roxarsone and produced arsenite, which was otherwise absent in the soil without added Fenton reagent. Methylation of arsenate was also enhanced by Fenton process in the earlier part of the experiment due to abundant supply of arsenate from Roxarsone degradation. Overall, addition of Fenton reagent resulted in the predominant presence of arsenate in the soils. Fenton process significantly improved the growth of rice in the maturity stage of the first crop, The concentration of methylated As species in the rice plant tissues among the different growth stages was highly variable. Addition of Fenton reagent into the soils led to reduced uptake of soil-borne As by the rice plants and this had a significant effect on reducing the accumulation of As in rice grains. The findings have implications for understanding As biogeochemistry in paddy rice field receiving rainwater-borne H2O2 and for development of mitigation strategies to reduce accumulation of As in rice grains. PMID:27060198

  2. [Characteristics of N2, N2O, NO, CO2 and CH4 Emissions in Anaerobic Condition from Sandy Loam Paddy Soil].

    PubMed

    Cao, Na; Wang, Rui; Liao, Ting-ting; Chen, Nuo; Zheng, Xun-hua; Yao, Zhi-sheng; Zhang, Hai; Butterbach-Bahl, Klaus

    2015-09-01

    Understanding the characteristics of the production of nitrogen gases (N2, N2O and NO), CO2 and CH4 in anaerobic paddy soils is not only a prerequisite for an improved mechanistic understanding of key microbial processes involved in the production of atmospheric greenhouse gases (GHG), but might also provide the basis for designing greenhouse gas mitigation strategies. Moreover, quantifying the composition fractions of denitrification gaseous products is of key importance for improving parameterization schemes of microbial processes in process-oriented models which are increasingly used for assessing soil GHG emissions at site and national scales. In our experiments we investigated two sandy loam soils from two paddy fields. The initial concentrations of soil nitrate and dissolved organic carbon (DOC) were set at approximately 50 mg.kg-1 and mg.kg-1, respectively, by adding a mixture solution of KNO3 and glucose. The emissions of N2, N2O NO, CO2 and CH4, as well as concentrations of carbon and nitrogen substrates for each soil sample were measured simultaneously, using a gas-flow-soil-core technique and a paralleling substrate monitoring system. The results showed that the accumulative emissions of N2, N2O and NO of the two soil samples for the entire incubation period were 6 - 8, 20, and 15 - 18 mg.kg-1, respectively. By measuring the cumulative emissions of denitrification gases (N, = N2 + N2O + NO) we were able to explain 95% to 98% of observed changes in s1ifr nilrate concentrations. The mass fractions of N2, N2O and NO emissions to Nt were approximately 15% -19%, 47% -49%, and 34% -36%, respectively. Thus, in our experiments N2O and NO were the main products of denitrification for the entire incubation period. However, as the temporal courses of hourly or daily production of the denitrification gases showed, NO production dominated and peaked firstly, and then N2O, before finally N2 became the dominant product. Our results show the high temporal dynamic of

  3. Effects of Different Organic Manures on the Biochemical and Microbial Characteristics of Albic Paddy Soil in a Short-Term Experiment

    PubMed Central

    Zhang, Qian; Zhou, Wei; Liang, Guoqing; Wang, Xiubin; Sun, Jingwen; He, Ping; Li, Lujiu

    2015-01-01

    This study aimed to evaluate the effects of chemical fertilizer (NPK), NPK with livestock manure (NPK+M), NPK with straw (NPK+S), and NPK with green manure (NPK+G) on soil enzyme activities and microbial characteristics of albic paddy soil, which is a typical soil with low productivity in China. The responses of extracellular enzyme activities and the microbial community diversity (determined by phospholipid fatty acid analysis [PLFA] and denaturing gradient gel electrophoresis [DGGE]) were measured. The results showed that NPK+M and NPK+S significantly increased rice yield, with NPK+M being approximately 24% greater than NPK. The NPK+M significantly increased soil organic carbon (SOC) and available phosphate (P) and enhanced phosphatase, β-cellobiosidase, L-leucine aminopeptidase and urease activities. The NPK+S significantly increased SOC and available potassium (K) and significantly enhanced N-acetyl-glucosamidase, β-xylosidase, urease, and phenol oxidase activities. The NPK+G significantly improved total nitrogen (N), ammonium N, available P, and N-acetyl-glucosamidase activity. The PLFA biomass was highest under NPK+S, followed by NPK+M and NPK+G treatments. Principal component analysis (PCA) of the PLFA indicated that soils with NPK+M and NPK+S contained higher proportions of unsaturated and cyclopropane fatty acids (biomarkers of fungi and gram-negative bacteria) and soil under NPK+G contained more straight chain saturated fatty acids (representing gram-positive bacteria). PCA of the DGGE patterns showed that organic amendments had a greater influence on fungal community. Cluster analysis of fungal DGGE patterns revealed that NPK+G was clearly separated. Meanwhile, the bacterial community of NPK+M treatment was the most distinct. RDA analysis revealed changes of microbial community composition mostly depended on β-xylosidase, β-cellobiosidase activities, total N and available K contents. The abundances of gram-negative bacterial and fungal PLFAs probably

  4. A three-year in-situ study on the persistence of a combined amendment (limestone+sepiolite) for remedying paddy soil polluted with heavy metals.

    PubMed

    Wu, Yu-Jun; Zhou, Hang; Zou, Zi-Jin; Zhu, Wei; Yang, Wen-Tao; Peng, Pei-Qin; Zeng, Min; Liao, Bo-Han

    2016-08-01

    In order to study the persistence of a combined amendment (LS, limestone+sepiolite) for remedying paddy soil polluted with the heavy metals Pb and Cd, a three-year in-situ experiment was conducted in a paddy soil near a mining area in southern Hunan, China. LS was applied at rates of 0, 2, 4, and 8g/kg (w/w); rice was subsequently planted for the three consecutive years of 2012 (first season), 2013 (second season), and 2014 (third season). Experimental results indicated that LS significantly increased soil pH values for all three seasons, and the enhancement ranked as follows: first season>second season>third season. Under the experimental conditions, the effect of LS on decreasing exchangeable concentrations of soil Pb and Cd was as follows: first season (97.6-99.8% for Pb and 88.3-98.9% for Cd)>second season (80.7-97.7% for Pb and 28.3-88.0% for Cd)>third season (32.6-97.7% for Pb and 8.3-71.4% for Cd); the effect of LS on reducing Pb concentrations in brown rice was: first season (73.5-81.2%)>third season (29.6-68.1%)>second season (0-9.7%), and that for reducing Cd concentrations in brown rice was third season (72.7-81.0%)>first season (56.1-66.8%)>second season (20.9-32.3%). For all three seasons, the effect of LS on reducing Cd content in brown rice was better than that for Pb. The highest translocation factors for Pb and Cd were from rice straw to husk, implying that the husk of rice plants was the main organ in which heavy metals accumulated. The effect of LS for decreasing soil exchangeable Cd content was relatively persistent, but that for Pb gradually decreased with time, implying that LS was more suitable for the long-term remediation of Cd-polluted soil than Pb-polluted soil. PMID:27107177

  5. Genetic diversity and community structure of rhizobia nodulating Sesbania cannabina in saline-alkaline soils.

    PubMed

    Li, Yan; Li, Xiangyue; Liu, Yajing; Wang, En Tao; Ren, Chenggang; Liu, Wei; Xu, Hualing; Wu, Hailong; Jiang, Nan; Li, Yunzhao; Zhang, Xiaoli; Xie, Zhihong

    2016-05-01

    Sesbania cannabina is a plant that grows naturally along the seashores in Rudong County, China (RDC) and it has been introduced into the Yellow River Delta (YRD) as a pioneer plant to improve the saline-alkaline soils. In order to investigate the diversity of S. cannabina rhizobia in these soils, a total of 198 rhizobial isolates were characterized and phylogenetic trees were constructed based on data from multilocus sequence analysis (MLSA) of the housekeeping genes recA, atpD and glnII, as well as 16S rRNA. Symbiotic features were also studied by establishing the phylogeny of the symbiotic genes nodA and nifH, and by performing nodulation assays. The isolates had highly conserved symbiotic genes and were classified into nine genospecies belonging to the genera Ensifer, Agrobacterium, Neorhizobium and Rhizobium. A unique community structure was detected in the rhizobia associated with S. cannabina in the saline-alkaline soils that was characterized by five novel genospecies and four defined species. In addition, Ensifer sp. I was the predominant rhizobia in YRD, whereas Ensifer meliloti and Neorhizobium huautlense were the dominant species in RDC. Therefore, the study demonstrated for the first time that this plant strongly selected the symbiotic gene background but not the genomic background of its microsymbionts. In addition, biogeographic patterns existed in the rhizobial populations associated with S. cannabina, which were mainly correlated with pH and salinity, as well as the mineral nutrient contents. This study provided novel information concerning the interaction between soil conditions, host plant and rhizobia, in addition to revealing the diversity of S. cannabina rhizobia in saline-alkaline soils. PMID:27061259

  6. Molecular analysis of bacterial community structures in paddy soils for environmental risk assessment with two varieties of genetically modified rice, Iksan 483 and Milyang 204.

    PubMed

    Kim, Min-Cheol; Ahn, Jae-Hyung; Shin, Hye-Chul; Kim, Taesung; Ryu, Tae-Hun; Kim, Dong-Hern; Song, Hong-Gyu; Lee, Geon Hyoung; Ka, Jong-Ok

    2008-02-01

    The impacts of planted transgenic rice varieties on bacterial communities in paddy soils were monitored using both cultivation and molecular methods. The rice field plot consisted of eighteen subplots planted with two genetically modified (GM) rice and four non-GM rice plants in three replicates. Analysis with denaturing gradient gel electrophoresis (DGGE) of PCR-amplified 16S rRNA genes revealed that the bacterial community structures were quite similar to each other in a given month, suggesting that there were no significant differences in bacterial communities between GM and non- GM rice soils. The bacterial community structures appeared to be generally stable with the seasons, as shown by a slight variation of microbial population levels and DGGE banding patterns over the year. Comparison analysis of 16S rDNA clone libraries constructed from soil bacterial DNA showed that there were no significant differences between GM and non-GM soil libraries but revealed seasonal differences of phyla distribution between August and December. The composition profile of phospholipid fatty acids (PLFA) between GM and non-GM soils also was not significantly different to each other. When soil DNAs were analyzed with PCR by using primers for the bar gene, which was introduced into GM rice, positive DNA bands were found in October and December soils. However, no bar gene sequence was detected in PCR analysis with DNAs extracted from both cultured and uncultured soil bacterial fractions. The result of this study suggested that, in spite of seasonal variations of bacterial communities and persistence of the bar gene, the bacterial communities of the experimental rice field were not significantly affected by cultivation of GM rice varieties. PMID:18309263

  7. Using DET and DGT probes (ferrihydrite and titanium dioxide) to investigate arsenic concentrations in soil porewater of an arsenic-contaminated paddy field in Bangladesh.

    PubMed

    Garnier, Jean-Marie; Garnier, Jérémie; Jézéquel, Didier; Angeletti, Bernard

    2015-12-01

    Arsenic concentration in the pore water of paddy fields (Csoln) irrigated with arsenic-rich groundwater is a key parameter in arsenic uptake by rice. Pore water extracts from cores and in situ deployment of DET and DGT probes were used to measure the arsenic concentration in the pore water. Ferrihydrite (Fe) and titanium dioxide (Ti) were used as DGT binding agents. Six sampling events during different growing stages of the rice, inducing different biogeochemical conditions, were performed in one rice field. A time series of DGT experiments allow the determination of an in situ arsenic diffusion coefficient in the diffusive gel (3.34×10(-6) cm(2) s(-1)) needed to calculate the so-called CDGT(Fe) and CDGT(Ti) concentrations. Over 3 days of a given sampling event and for cores sampled at intervals smaller than 50 cm, great variability in arsenic Csoln concentrations between vertical profiles was observed, with maxima of concentrations varying from 690 to 2800 μg L(-1). Comparisons between arsenic measured Csol and CDET and calculated CDGT(Fe) and CDGT(Ti) concentrations show either, in a few cases, roughly similar vertical profiles, or in other cases, significantly different profiles. An established iron oxyhydroxide precipitation in the DET gel may explain why measured arsenic CDET concentrations occasionally exceeded Csoln. The large spread in results suggests limitations to the use of DET and type of DGT probes used here for similarly representing the spatio-temporal variations of arsenic content in soil pore water in specific environmental such as paddy soils. PMID:26225738

  8. Alkaline ameliorants increase nitrous oxide emission from acidified black soil in Northeastern China.

    PubMed

    Han, Zuoqiang; Zhang, Xilin; Qiao, Yanjiao; Wang, Lianfeng

    2011-06-01

    Lime and plant ash are common management used to achieve optimum pH for plant growth and improve soil properties in agricultural soils. Laboratory incubation was conducted to assess N20 emissions as influenced by different soil amendments (lime and plant ash) in a slightly acidic arable soil (pH 5.34). The experimental treatments consisted of CK, lime and plant ash fertilized with NH4(+)-N or N03(-)-N as nitrogen resource. The results show that lime and plant ash dramatically increases the soil pH and N20 emission. For N03(-)-N fertilization, the cumulative N20 emissions from CK, lime and ash are 421, 1669 and 921 μg N20-N/kg, respectively. For NH4(+)-N fertilization, the cumulative N20 emissions from CK, lime and ash are 361, 576 and 559 μg N20-N/kg, respectively. N03(-)-N addition leads to more N20 emission than that of NH4(+)-N addition, and lime increases more N20 emission than that of plant ash. After incubation, N03(-)-N content decreased largely. The findings suggested that alkaline ameliorants increase N20 emissions due to enhancement of soil denitrification. PMID:25084592

  9. [Effects of rice straw returning on the community structure and diversity of nitrogen-fixing gene (nifH) in paddy soil].

    PubMed

    Zhang, Miao-miao; Liu, Yi; Sheng, Rong; Qin, Hong-ling; Wu, Yan-zheng; Wei, Wen-xue

    2013-08-01

    Taking a long-term fertilization experiment in Taoyuan Agro-ecosystem Research Station under Chinese Academy of Sciences as the platform, and selecting four treatments (no fertilization, CK; rice straw returning, C; nitrogen, phosphorus and potassium fertilization, NPK; and NPK+C) as the objects, soil samples were collected at the tillering, booting and maturing stages of rice, and the abundance, composition and diversity of nifH-containing bacterial community were measured by real-time quantitative PCR and terminal restriction fragment length polymorphism (T-RFLP), aimed to understand the effects of rice straw returning on the nifH-containing bacterial community in paddy soil. Compared with CK, treatments NPK+C and NPK increased the abundance of nifH-containing microorganisms significantly (except at tillering stage), and NPK+C had the highest abundance of nifH-containing microorganisms. Under the effects of long-term fertilization, the composition of nifH gene community in CK differed obviously from that in the other three treatments. The nifH composition had definite difference between C and NPK, but less difference between NPK and NPK+C. Long-term fertilization did not induce significant changes in nifH diversity. Therefore, long-term rice straw returning not only induced the changes of nifH gene community composition, but also resulted in a significant increase in the abundance of nifH-containing community, and hence, the increase of soil nitrogen fixing capacity. PMID:24380357

  10. Gypsum amendment to rice paddy soil stimulated bacteria involved in sulfur cycling but largely preserved the phylogenetic composition of the total bacterial community.

    PubMed

    Wörner, Susanne; Zecchin, Sarah; Dan, Jianguo; Todorova, Nadezhda Hristova; Loy, Alexander; Conrad, Ralf; Pester, Michael

    2016-06-01

    Rice paddies are indispensable for human food supply but emit large amounts of the greenhouse gas methane. Sulfur cycling occurs at high rates in these water-submerged soils and controls methane production, an effect that is increased by sulfate-containing fertilizers or soil amendments. We grew rice plants until their late vegetative phase with and without gypsum (CaSO4 ·2H2 O) amendment and identified responsive bacteria by 16S rRNA gene amplicon sequencing. Gypsum amendment decreased methane emissions by up to 99% but had no major impact on the general phylogenetic composition of the bacterial community. It rather selectively stimulated or repressed a small number of 129 and 27 species-level operational taxonomic units (OTUs) (out of 1883-2287 observed) in the rhizosphere and bulk soil, respectively. Gypsum-stimulated OTUs were affiliated with several potential sulfate-reducing (Syntrophobacter, Desulfovibrio, unclassified Desulfobulbaceae, unclassified Desulfobacteraceae) and sulfur-oxidizing taxa (Thiobacillus, unclassified Rhodocyclaceae), while gypsum-repressed OTUs were dominated by aerobic methanotrophs (Methylococcaceae). Abundance correlation networks suggested that two abundant (>1%) OTUs (Desulfobulbaceae, Rhodocyclaceae) were central to the reductive and oxidative parts of the sulfur cycle. PMID:27085098

  11. Arsenic accumulation and speciation in rice grains influenced by arsenic phytotoxicity and rice genotypes grown in arsenic-elevated paddy soils.

    PubMed

    Syu, Chien-Hui; Huang, Chia-Chen; Jiang, Pei-Yu; Lee, Chia-Hsing; Lee, Dar-Yuan

    2015-04-01

    Rice consumption is a major route of As exposure to human for the population of worldwide. This study investigates the effect of phytotoxicity and rice genotypes on the content and speciation of As in rice grains grown in different levels of As-elevated paddy soils from Taiwan. Three levels of As-elevated soils and six rice genotypes commonly planted in Taiwan were used for this study. The results indicate that As contents in grains of rice is not proportional to soil As concentrations and they were equal or higher in indica genotypes than japonica genotypes used in this study. It was also found that the As phytotoxicity not only reducing the grain yields but also the As concentrations in grain of rice. The predominant As species found in rice grains were dimethylarsinic acid (DMA) and arsenite. The concentrations of DMA increased with total As concentrations, wherggeas the arsenite remained in a narrow range from 0.1 to 0.3 mg kg(-1). Because of the lower toxicity of DMA than inorganic As species, the health risks may not be increased through consumption of rice even when total As content in the grains is increased. PMID:25577320

  12. Isolation and identification of myxobacteria from saline-alkaline soils in Xinjiang, China.

    PubMed

    Zhang, Xianjiao; Yao, Qing; Cai, Zhuoping; Xie, Xiaolin; Zhu, Honghui

    2013-01-01

    Fifty-eight terrestrial and salt-tolerant myxobacteria were isolated from the saline-alkaline soils collected from Xinjiang, China. Based on the morphologies and the 16S rRNA gene sequences, these isolates were assigned into 6 genera, Myxococcus, Cystobacter, Corallococcus, Sorangium, Nannocystis and Polyangium. All the strains grew better with 1% NaCl than without NaCl. Some Myxococcus strains were able to grow at 2% NaCl concentration, suggesting that these strains may be particular type of terrestrial myxobacteria. PMID:23936436

  13. Impact of biochar application on nitrogen nutrition of rice, greenhouse-gas emissions and soil organic carbon dynamics in two paddy soils of China

    SciTech Connect

    Xie, Zubin; Xu, Yanping; Liu, Gang; Liu, Qi; Zhu, Jianguo; Tu, Cong; Amonette, James E.; Cadisch, Georg; Yong, Jean W.; Hu, Shuijin

    2013-09-01

    Two field microcosm experiments and 15N labeling techniques were used to investigate the first-year effects of biochar addition on rice N nutrition and GHG emissions in an Inceptisol and an Ultisol. Biochar N bioavailability and effect of biochar on fertilizer nitrogen-use efficiency (NUE) were studied by 15N-enriched wheat biochar (7.8803 atom% 15N) and fertilizer urea (5 atom% 15N) (Experiment I). Corn biochar and corn stalks were applied at 12 Mg ha-1 to study their effects on GHG emissions (Experiment II). Biochar had no significant impact on rice production and less than 2% of the biochar N was available to plants in the first season. Biochar addition increased soil C and N contents and decreased urea NUE.. Seasonal cumulative CH4 emissions with biochar were similar to the controls, but significantly lower than the local practice of straw amendment. Soil emissions of N2O with biochar amendment were similar to the control in the acidic Ultisol, but significantly higher in the slightly alkaline Inceptisol. Carbon-balance calculations found no major losses of biochar-C. Low bio-availability of biochar N did not make a significant impact on rice production or N nutrition during the first year.. Replacement of straw amendments with biochar could decrease CH4 emissions and increase SOC stocks.

  14. [Modeling the ammonia volatilization from common urea and controlled releasing urea fertilizers in paddy soil of Taihui region of China by Jayaweera-Mikkelsen model].

    PubMed

    Li, Hui-lin; Han, Yong; Cai, Zu-cong

    2008-04-01

    The ammonia volatilization on the Typic Gleyi-stagnic Anthrosol with application of common urea and controlled release urea (LP-S100) fertilizers in the rice seasons in paddy soil of Taihui region of China was modeled by Jayaweera-Mikkelsen model. Results showed great difference of ammonia volatilization from two type fertilizers was detected with lysimeter experiment in the rice season. Nitrogen loss via ammonia volatilization after common urea application with conventional ways was 29%-35%, while only 5% of controlled release urea-N was volatilized. The Jayaweera-Mikkelsen model was over estimated the total amount of ammonia volatilization in the whole season, and great deviation from the measured data was obvious for the higher volatilization from common urea fertilizer. The estimated data were 2.95-4.19 times of the measures one for common urea treatments, while they were 1.19-1.40 times of those measured for LP-S100 treatments. The order of magnitude quotient was one of the indicators to evaluate the model estimation. The value of it was 0.8, which indicated the estimation of the model need improvement. Though sensitive analysis for the five parameters in the model was tested and amended the parameter of the concentration of NH4+ -N, a limited term was inducted in the model operation. The amended model got better results as the ratio of estimation to measured data was decreased to 1.12-1.28. The alga activity in the paddy field influenced ammonia volatilization and might make the failure of the model estimation of the original model. PMID:18637360

  15. Cyanide Degradation under Alkaline Conditions by a Strain of Fusarium solani Isolated from Contaminated Soils

    PubMed Central

    Dumestre, A.; Chone, T.; Portal, J.; Gerard, M.; Berthelin, J.

    1997-01-01

    Several cyanide-tolerant microorganisms have been selected from alkaline wastes and soils contaminated with cyanide. Among them, a fungus identified as Fusarium solani IHEM 8026 shows a good potential for cyanide biodegradation under alkaline conditions (pH 9.2 to 10.7). Results of K(sup14)CN biodegradation studies show that fungal metabolism seems to proceed by a two-step hydrolytic mechanism: (i) the first reaction involves the conversion of cyanide to formamide by a cyanide-hydrolyzing enzyme, cyanide hydratase (EC 4.2.1.66); and (ii) the second reaction consists of the conversion of formamide to formate, which is associated with fungal growth. No growth occurred during the first step of cyanide degradation, suggesting that cyanide is toxic to some degree even in cyanide-degrading microorganisms, such as F. solani. The presence of organic nutrients in the medium has a major influence on the occurrence of the second step. Addition of small amounts of yeast extract led to fungal growth, whereas no growth was observed in media containing cyanide as the sole source of carbon and nitrogen. The simple hydrolytic detoxification pathway identified in the present study could be used for the treatment of many industrial alkaline effluents and wastes containing free cyanide without a prior acidification step, thus limiting the risk of cyanhydric acid volatilization; this should be of great interest from an environmental and health point of view. PMID:16535647

  16. Contrasting pH buffering patterns in neutral-alkaline soils along a 3600 km transect in northern China

    NASA Astrophysics Data System (ADS)

    Luo, W. T.; Nelson, P. N.; Li, M.-H.; Cai, J. P.; Zhang, Y. Y.; Zhang, Y. G.; Yang, S.; Wang, R. Z.; Wang, Z. W.; Wu, Y. N.; Han, X. G.; Jiang, Y.

    2015-12-01

    Soil pH buffering capacity (pHBC) plays a crucial role in predicting acidification rates, yet its large-scale patterns and controls are poorly understood, especially for neutral-alkaline soils. Here, we evaluated the spatial patterns and drivers of pHBC along a 3600 km long transect (1900 km sub-transect with carbonate-containing soils and 1700 km sub-transect with non-carbonate-containing soils) across northern China. Soil pHBC was greater in the carbonate-containing soils than in the non-carbonate-containing soils. Acid addition decreased soil pH in the non-carbonate-containing soils more markedly than in the carbonate-containing soils. Within the carbonate soil sub-transect, soil pHBC was positively correlated with cation exchange capacity (CEC), carbonate content and exchangeable sodium (Na) concentration, but negatively correlated with initial pH and clay content, and not correlated with soil organic carbon (SOC) content. Within the non-carbonate sub-transect, soil pHBC was positively related to initial pH, clay content, CEC and exchangeable Na concentration, but not related to SOC content. Carbonate content was the primary determinant of pHBC in the carbonate-containing soils and CEC was the main determinant of buffering capacity in the non-carbonate-containing soils. Along the transect, soil pHBC was different in regions with different aridity index. Soil pHBC was positively related to aridity index and carbonate content across the carbonate-containing soil sub-transect. Our results indicated that mechanisms controlling pHBC differ among neutral-alkaline soils of northern China, especially between carbonate- and non-carbonate-containing soils. This understanding should be incorporated into the acidification risk assessment and landscape management in a changing world.

  17. High resolution depth distribution of Bacteria, Archaea, methanotrophs, and methanogens in the bulk and rhizosphere soils of a flooded rice paddy

    PubMed Central

    Lee, Hyo Jung; Jeong, Sang Eun; Kim, Pil Joo; Madsen, Eugene L.; Jeon, Che Ok

    2015-01-01

    The communities and abundances of methanotrophs and methanogens, along with the oxygen, methane, and total organic carbon (TOC) concentrations, were investigated along a depth gradient in a flooded rice paddy. Broad patterns in vertical profiles of oxygen, methane, TOC, and microbial abundances were similar in the bulk and rhizosphere soils, though methane and TOC concentrations and 16S rRNA gene copies were clearly higher in the rhizosphere soil than in the bulk soil. Oxygen concentrations decreased sharply to below detection limits at 8 mm depth. Pyrosequencing of 16S rRNA genes showed that bacterial and archaeal communities varied according to the oxic, oxic-anoxic, and anoxic zones, indicating that oxygen is a determining factor for the distribution of bacterial and archaeal communities. Aerobic methanotrophs were maximally observed near the oxic-anoxic interface, while methane, TOC, and methanogens were highest in the rhizosphere soil at 30–200 mm depth, suggesting that methane is produced mainly from organic carbon derived from rice plants and is metabolized aerobically. The relative abundances of type I methanotrophs such as Methylococcus, Methylomonas, and Methylocaldum decreased more drastically than those of type II methanotrophs (such as Methylocystis and Methylosinus) with increasing depth. Methanosaeta and Methanoregula were predominant methanogens at all depths, and the relative abundances of Methanosaeta, Methanoregula, and Methanosphaerula, and GOM_Arc_I increased with increasing depth. Based on contrasts between absolute abundances of methanogens and methanotrophs at depths sampled across rhizosphere and bulk soils (especially millimeter-scale slices at the surface), we have identified populations of methanogens (Methanosaeta, Methanoregula, Methanocella, Methanobacterium, and Methanosphaerula), and methanotrophs (Methylosarcina, Methylococcus, Methylosinus, and unclassified Methylocystaceae) that are likely physiologically active in situ. PMID

  18. High resolution depth distribution of Bacteria, Archaea, methanotrophs, and methanogens in the bulk and rhizosphere soils of a flooded rice paddy.

    PubMed

    Lee, Hyo Jung; Jeong, Sang Eun; Kim, Pil Joo; Madsen, Eugene L; Jeon, Che Ok

    2015-01-01

    The communities and abundances of methanotrophs and methanogens, along with the oxygen, methane, and total organic carbon (TOC) concentrations, were investigated along a depth gradient in a flooded rice paddy. Broad patterns in vertical profiles of oxygen, methane, TOC, and microbial abundances were similar in the bulk and rhizosphere soils, though methane and TOC concentrations and 16S rRNA gene copies were clearly higher in the rhizosphere soil than in the bulk soil. Oxygen concentrations decreased sharply to below detection limits at 8 mm depth. Pyrosequencing of 16S rRNA genes showed that bacterial and archaeal communities varied according to the oxic, oxic-anoxic, and anoxic zones, indicating that oxygen is a determining factor for the distribution of bacterial and archaeal communities. Aerobic methanotrophs were maximally observed near the oxic-anoxic interface, while methane, TOC, and methanogens were highest in the rhizosphere soil at 30-200 mm depth, suggesting that methane is produced mainly from organic carbon derived from rice plants and is metabolized aerobically. The relative abundances of type I methanotrophs such as Methylococcus, Methylomonas, and Methylocaldum decreased more drastically than those of type II methanotrophs (such as Methylocystis and Methylosinus) with increasing depth. Methanosaeta and Methanoregula were predominant methanogens at all depths, and the relative abundances of Methanosaeta, Methanoregula, and Methanosphaerula, and GOM_Arc_I increased with increasing depth. Based on contrasts between absolute abundances of methanogens and methanotrophs at depths sampled across rhizosphere and bulk soils (especially millimeter-scale slices at the surface), we have identified populations of methanogens (Methanosaeta, Methanoregula, Methanocella, Methanobacterium, and Methanosphaerula), and methanotrophs (Methylosarcina, Methylococcus, Methylosinus, and unclassified Methylocystaceae) that are likely physiologically active in situ. PMID

  19. Effect of systemic herbicides on N2-fixing and phosphate solubilizing microorganisms in relation to availability of nitrogen and phosphorus in paddy soils of West Bengal.

    PubMed

    Das, Amal Chandra; Debnath, Anjan

    2006-11-01

    A field experiment has been conducted with four systemic herbicides viz., butachlor [N-(butoxymethyl)-2-chloro-2',6'-diethyl-acetanilide], fluchloralin [N-(2-chloroethyl)-(2,6-dinitro-N-propyl-4-trifluoromethyl) aniline], oxadiazon [5-terbutyl-3-(2,4-dichloro-5-isopro poxyphenyl)-1,3,4-oxadiazol-2-one] and oxyfluorfen [2-chloro-1-(3-ethoxy-4-nitrophenyl)-4-(trifluoromethyl) benzene] at their recommended field rates (2.0, 1.5, 0.4 and 0.12kga.i.ha(-1), respectively) to investigate their effects on growth and activities of aerobic non-symbiotic N(2)-fixing bacteria and phosphate solubilizing microorganisms in relation to availability of nitrogen and phosphorus in the rhizosphere soils as well as yield of the rice crop (Oryza sativa L cv. IR-36). Application of herbicides, in general, highly stimulated the population and activities of the target microorganisms, which resulted in a greater amount of atmospheric nitrogen fixation and phosphate solubilization in the rhizosphere soils of the test crop. The greater microbial activities subsequently augmented the mineralization and availability of nitrogen and phosphorus in the soil solution, which in turn increased the yield of the crop. Among the herbicides, oxyfluorfen was most stimulative followed by fluchloralin and oxadiazon in augmenting the microbial activities in soil. Butachlor also accentuated the mineralization and availability of nitrogen due to higher incitement of non-symbiotic N(2)-fixing bacteria in paddy soil. The grain and straw yields of the crop were also significantly increased due to the application of oxyfluorfen (20.2% and 21%) followed by fluchloralin (13.1% and 15.4%) and butachlor (9.1% and 10.2%), respectively. PMID:16630642

  20. An improved protocol for DNA extraction from alkaline soil and sediment samples for constructing metagenomic libraries.

    PubMed

    Verma, Digvijay; Satyanarayana, T

    2011-09-01

    An improved single-step protocol has been developed for extracting pure community humic substance-free DNA from alkaline soils and sediments. The method is based on direct cell lysis in the presence of powdered activated charcoal and polyvinylpolypyrrolidone followed by precipitation with polyethyleneglycol and isopropanol. The strategy allows simultaneous isolation and purification of DNA while minimizing the loss of DNA with respect to other available protocols for metagenomic DNA extraction. Moreover, the purity levels are significant, which are difficult to attain with any of the methods reported in the literature for DNA extraction from soils. The DNA thus extracted was free from humic substances and, therefore, could be processed for restriction digestion, PCR amplification as well as for the construction of metagenomic libraries. PMID:21519906

  1. Biases in community structures of ammonia/ammonium-oxidizing microorganisms caused by insufficient DNA extractions from Baijiang soil revealed by comparative analysis of coastal wetland sediment and rice paddy soil.

    PubMed

    Han, Ping; Li, Meng; Gu, Ji-Dong

    2013-10-01

    Repetitive extraction of DNAs from surface sediments of a coastal wetland in Mai Po Nature Reserve (MP) of Hong Kong and surface Baijiang soils from a rice paddy (RP) in Northeast China was conducted to compare the microbial diversity in this study. Community structures of ammonia/ammonium-oxidizing microorganisms in these samples were analyzed by PCR-DGGE technique. The diversity and abundance of ammonia-oxidizing archaea (AOA), ammonia-oxidizing bacteria (AOB), and anaerobic ammonium-oxidizing (anammox) bacteria were also analyzed based on archaeal and bacterial ammonia monooxygenase subunit A encoding (amoA) and anammox bacterial 16S rRNA genes, respectively. DGGE profiles of archaeal and bacterial amoA and anammox bacterial 16S rRNA genes showed a similar pattern among all five repetitively extracted DNA fractions from both MP and RP, except the anammox bacteria in RP, indicating a more diverse anammox community retrieved in the second to the fifth fractions than the first one. Both soil and marine group AOA were detected while soil and coastal group AOB and Scalindua-anammox bacteria were dominant in MP. Soil group AOA and marine group AOB were dominant in RP, while both Scalindua and Kuenenia species were detected in RP. Pearson correlation analysis showed that the abundance of archaeal and bacterial amoA and anammox bacterial 16S rRNA genes was significantly correlated with the DNA concentrations of the five DNA fractions from MP, but not from RP (except the archaeal amoA gene). Results suggest that anammox bacteria diversity may be biased by insufficient DNA extraction of rice paddy soil samples. PMID:23974369

  2. Contrasting pH buffering patterns in neutral-alkaline soils along a 3600 km transect in northern China

    NASA Astrophysics Data System (ADS)

    Luo, W.; Nelson, P. N.; Li, M.-H.; Cai, J.; Zhang, Y.; Zhang, Y.; Shan, Y.; Wang, R.; Han, X.; Jiang, Y.

    2015-08-01

    Soil pH buffering capacity (pHBC) plays a crucial role in predicting acidification rates, yet its large-scale patterns and controls are poorly understood, especially for neutral-alkaline soils. Here, we evaluated the spatial patterns and drivers of pHBC along a 3600 km long transect (1900 km sub-transect with carbonate containing soils and 1700 km sub-transect with non-carbonate containing soils) across northern China. Soil pHBC was greater in the carbonate containing soils than in the non-carbonate containing soils. Acid addition decreased soil pH in the non-carbonate containing soils more markedly than in the carbonate containing soils. Within the carbonate soil sub-transect, soil pHBC was positively correlated with cation exchange capacity (CEC), carbonate content and exchangeable sodium (Na) concentration, but negatively correlated with initial pH and clay content, and not correlated with soil organic carbon (SOC) content. Within the non-carbonate sub-transect, soil pHBC was positively related to initial pH, clay content, CEC and exchangeable Na concentration, but not related to SOC content. Carbonate content was the primary determinant of pHBC in the carbonate containing soils and CEC was the main determinant of buffering capacity in the non-carbonate containing soils. Soil pHBC was positively related to aridity index and carbonate content across the carbonate containing soil sub-transect. Our results indicated that mechanisms controlling pHBC differ among neutral-alkaline soils of northern China, especially between carbonate and non-carbonate containing soils, leading to different rates, risks, and impacts of acidification. This understanding should be incorporated into the acidification risk assessment and landscape management in a changing world.

  3. Microbial population index and community structure in saline-alkaline soil using gene targeted metagenomics.

    PubMed

    Keshri, Jitendra; Mishra, Avinash; Jha, Bhavanath

    2013-03-30

    Population indices of bacteria and archaea were investigated from saline-alkaline soil and a possible microbe-environment pattern was established using gene targeted metagenomics. Clone libraries were constructed using 16S rRNA and functional gene(s) involved in carbon fixation (cbbL), nitrogen fixation (nifH), ammonia oxidation (amoA) and sulfur metabolism (apsA). Molecular phylogeny revealed the dominance of Actinobacteria, Firmicutes and Proteobacteria along with archaeal members of Halobacteraceae. The library consisted of novel bacterial (20%) and archaeal (38%) genera showing ≤95% similarity to previously retrieved sequences. Phylogenetic analysis indicated ability of inhabitant to survive in stress condition. The 16S rRNA gene libraries contained novel gene sequences and were distantly homologous with cultured bacteria. Functional gene libraries were found unique and most of the clones were distantly related to Proteobacteria, while clones of nifH gene library also showed homology with Cyanobacteria and Firmicutes. Quantitative real-time PCR exhibited that bacterial abundance was two orders of magnitude higher than archaeal. The gene(s) quantification indicated the size of the functional guilds harboring relevant key genes. The study provides insights on microbial ecology and different metabolic interactions occurring in saline-alkaline soil, possessing phylogenetically diverse groups of bacteria and archaea, which may be explored further for gene cataloging and metabolic profiling. PMID:23083746

  4. Runoff and degradation of aerially applied dinotefuran in paddy fields and river.

    PubMed

    Yokoyama, Sayako; Ito, Masataka; Nagasawa, Shunsuke; Morohashi, Masayuki; Ohno, Masaki; Todate, Yukitaka; Kose, Tomohiro; Kawata, Kuniaki

    2015-06-01

    Variation, run-off and degradation characteristics of the insecticide dinotefuran, (EZ)-(RS)-1-methyl-2-nitro-3-(tetrahydro-3-furyl-methyl)guanidine, in water and soil from two paddy fields after aerial application was investigated as well as in river water. Maximum concentrations of dinotefuran were 290 and 720 µg/L in the two paddy waters, 25 and 28 µg/kg dry in the two paddy soils, and 10 µg/L in the river water. Runoff ratios of dinotefuran from the paddy fields were calculated as 14%-41%. Mean half-lives of dinotefuran were 5.4 days in the paddy water and 12 days in the paddy soil. Results obtained in this study are important for the evaluation of the actual behavior of dinotefuran in paddy fields and rivers. PMID:25917847

  5. Genotypic alteration and competitive nodulation of Mesorhizobium muleiense against exotic chickpea rhizobia in alkaline soils.

    PubMed

    Zhang, Jun Jie; Yu, Tao; Lou, Kai; Mao, Pei Hong; Wang, En Tao; Chen, Wen Feng; Chen, Wen Xin

    2014-10-01

    Mesorhizobium muleiense, Mesorhizobium mediterraneum and Mesorhizobium ciceri are chickpea (Cicer arietinum L.) rhizobia that share a high similarity of the symbiotic genes nodC and nifH, but they have different geographic distributions. M. muleiense has been isolated and found only in alkaline soils of Xinjiang, China, whereas the other two strains have been found in the Mediterranean and India. To investigate the species stability of M. muleiense during natural evolution and its capability of competitive nodulation against the other two exotic species, re-sampling of nodules in the field and competition experiments between the three species were conducted. The results showed that the predominant microsymbiont associated with chickpea grown in Xinjiang was still M. muleiense, but the predominant genotypes of M. muleiense had changed significantly during the four years since a previous survey. The data also showed that M. mediterraneum and M. ciceri were more competitive than the residential strain of M. muleiense CCBAU 83963(T) in sterilized vermiculite or soils from Xinjiang. However, in non-sterilized soils, M. muleiense was the predominant nodule occupier. These results indicated that natural or adapting evolution of M. muleiense was occurring in fields subjected to changing environmental factors. In addition, the biogeography and symbiotic associations of rhizobia with their host legumes were also influenced by biological factors in the soil, such as indigenous rhizobia and other organisms. PMID:25123757

  6. Paddy field, groundwater and land subsidence

    SciTech Connect

    Wen, L.J.

    1995-12-31

    Through many years of research and technical interchange both at home and abroad, it is commonly recognized that paddy fields possess the functions of micro-climate adjustment, flood detection and prevention, soil and water conservation, river-flow stabilization, soil salinization prevention, water purification, groundwater recharge, rural area beautification and environmental protection which are all beneficial to the public. In recent years, the global environmental problems have become a series concern throughout the world. These include the broken ozone layer, green house effects, acid rain, land desertion, tropical rain forest disappearing etc. Among them, rain forest disappearing draws great attention. Both rain forests and paddy fields are in tropical areas. They have similar functions and are disappearing because of economic pressure. This paper describes the special functions of paddy fields on water purification, ground water recharge and prevention of land subsidence, and reiterates groundwater utilization and land subsidence prevention measures. In view of the importance of groundwater resources, paddy fields, which can not be replaced by any other artificial groundwater recharge facilities, should not be reduced in acreage, nor can they be left idle. Paddy fields shall be properly maintained and managed in order to strengthen their special functions in the years to come even under heavy pressure from foreign countries.

  7. The contents of alkali and alkaline earth metals in soils of the southern Cis-Ural region

    NASA Astrophysics Data System (ADS)

    Asylbaev, I. G.; Khabirov, I. K.

    2016-01-01

    The contents and distribution patterns of alkali and alkaline earth metals in soils and rocks of the southern Cis-Ural region were studied. A database on the contents of these metals was developed, the soils were classified with respect to their provision with these metals, and corresponding schematic maps showing their distribution in soils of the region were compiled. It was found that the contents of these metals decrease from east to west (from the Yuryuzan-Aisk Piedmont Plain to the Ufa Plateau and to the Belebeevsk Upland), and their distribution patterns change. Among alkali metals, the highest accumulation in the soils is typical of potassium, sodium, and cesium; among alkaline earth metals, of strontium and barium.

  8. The essential role of coumarin secretion for Fe acquisition from alkaline soil

    PubMed Central

    Clemens, Stephan; Weber, Michael

    2016-01-01

    ABSTRACT Plant productivity is limited by the scarcity of the essential micronutrient iron particularly in alkaline soils. The root secretion of phenolics has long been recognized as a component of the acidification-reduction strategy to acquire iron (strategy I). However, very little molecular insight into this process was available until recently several research groups independently discovered the important role of coumarins for the growth of Arabidopsis thaliana under Fe-limited conditions. Genome-wide analyses of iron deficiency responses, mutant screening and metabolomics experiments all converged on the finding that the synthesis and root exudation of scopoletin, esculetin and other coumarins is essential for iron uptake from substrates with low iron availability. Here we describe the evidence supporting this conclusion and discuss important questions that now have to be addressed in order to better understand the mechanistic basis of coumarin-dependent iron uptake and its significance within the plant kingdom. PMID:26618918

  9. Kinetics of the alkaline hydrolysis of 2,4,6-trinitrotoluene in aqueous solution and highly contaminated soils

    SciTech Connect

    Emmrich, M.

    1999-11-01

    During the two World Wars, large amounts of TNT were released into the environment. Until today, high concentrations of TNT can be found in the soil of former ammunition plants. To obtain basic data for a novel treatment process for highly contaminated soils, the homogeneous aqueous hydrolysis of TNT in the pH range from 10 to 12 and the alkaline treatment of two contaminated soils at pH 11 and pH 12 were investigated. The experimental data were described for their respective pH values using a pseudo-first-order model. In the homogeneous experiments, 95--97% of the TNT was hydrolyzed. During alkaline hydrolysis, up to two nitrogroups per TNT molecule were released, indicating the irreversible destruction of TNT. Except for the formation of small traces of amino dinitrotoluenes and trinitrobenzenes, no nitroaromatic benzenes or toluenes were detected during GC analysis. For the less contaminated soil, ELBP2, with an initial TNT concentration of 116 mg/kg, a destruction of 99% was achieved. The highly contaminated soil, HTNT2 (16.1 g of TNT/kg), showed a hydrolyzation level of 90-94%. The results show that the alkaline treatment of highly contaminated soils may prove to be effective as an alternative treatment technology.

  10. Chemical equilibria model of strontium-90 adsorption and transport in soil in response to dynamic alkaline conditions.

    PubMed

    Spalding, B P; Spalding, I R

    2001-01-15

    Strontium-90 is a major hazardous contaminant of radioactive wastewater and its processing sludges at many Department of Energy (DOE) facilities. In the past, such contaminated wastewater and sludge have been disposed in soil seepage pits, lagoons, or cribs often under highly perturbed alkaline conditions (pH > 12) where 90Sr solubility is low and its adsorption to surrounding soil is high. As natural weathering returns these soils to near-neutral or slightly acidic conditions, the adsorbed and precipitated calcium and magnesium phases, in which 90Sr is carried, change significantly in both nature and amounts. No comprehensive computational method has been formulated previously to quantitatively simulate the dynamics of 90Sr in the soil-groundwater environment under such dynamic and wide-ranging conditions. A computational code, the Hydrologic Utility Model for Demonstrating Integrated Nuclear Geochemical Environmental Responses (HUMDINGER), was composed to describe the changing equilibria of 90Sr in soil based on its causative chemical reactions including soil buffering, pH-dependent cation-exchange capacity, cation selectivity, and the precipitation/dissolution of calcium carbonate, calcium hydroxide, and magnesium hydroxide in response to leaching groundwater characteristics including pH, acid-neutralizing capacity, dissolved cations, and inorganic carbonate species. The code includes a simulation of one-dimensional transport of 90Sr through a soil column as a series of soil mixing cells where the equilibrium soluble output from one cell is applied to the next cell. Unamended soil leaching and highly alkaline soil treatments, including potassium hydroxide, sodium silicate, and sodium aluminate, were simulated and compared with experimental findings using large (10 kg) soil columns that were leached with 90Sr-contaminated groundwater after treatment. HUMDINGER's simulations were in good agreement with dynamic experimental observations of soil exchange capacity

  11. Fate of Zinc Oxide Nanoparticles Coated onto Macronutrient Fertilizers in an Alkaline Calcareous Soil

    PubMed Central

    Milani, Narges; Hettiarachchi, Ganga M.; Kirby, Jason K.; Beak, Douglas G.; Stacey, Samuel P.; McLaughlin, Mike J.

    2015-01-01

    Zinc oxide (ZnO) nanoparticles may provide a more soluble and plant available source of Zn in Zn fertilizers due to their greater reactivity compared to equivalent micron- or millimetre-sized (bulk) particles. However, the effect of soil on solubility, spatial distribution and speciation of ZnO nanoparticles has not yet been investigated. In this study, we examined the diffusion and solid phase speciation of Zn in an alkaline calcareous soil following application of nanoparticulate and bulk ZnO coated fertilizer products (monoammonium phosphate (MAP) and urea) using laboratory-based x-ray techniques and synchrotron-based μ-x-ray fluorescence (μ–XRF) mapping and absorption fine structure spectroscopy (μ–XAFS). Mapping of the soil-fertilizer reaction zones revealed that most of the applied Zn for all treatments remained on the coated fertilizer granule or close to the point of application after five weeks of incubation in soil. Zinc precipitated mainly as scholzite (CaZn2(PO4)2.2H2O) and zinc ammonium phosphate (Zn(NH4)PO4) species at the surface of MAP granules. These reactions reduced dissolution and diffusion of Zn from the MAP granules. Although Zn remained as zincite (ZnO) at the surface of urea granules, limited diffusion of Zn from ZnO-coated urea granules was also observed for both bulk and nanoparticulate ZnO treatments. This might be due to either the high pH of urea granules, which reduced solubility of Zn, or aggregation (due to high ionic strength) of released ZnO nanoparticles around the granule/point of application. The relative proportion of Zn(OH)2 and ZnCO3 species increased for all Zn treatments with increasing distance from coated MAP and urea granules in the calcareous soil. When coated on macronutrient fertilizers, Zn from ZnO nanoparticles (without surface modifiers) was not more mobile or diffusible compared to bulk forms of ZnO. The results also suggest that risk associated with the presence of ZnO NPs in calcareous soils would be the

  12. Fate of Zinc Oxide Nanoparticles Coated onto Macronutrient Fertilizers in an Alkaline Calcareous Soil.

    PubMed

    Milani, Narges; Hettiarachchi, Ganga M; Kirby, Jason K; Beak, Douglas G; Stacey, Samuel P; McLaughlin, Mike J

    2015-01-01

    Zinc oxide (ZnO) nanoparticles may provide a more soluble and plant available source of Zn in Zn fertilizers due to their greater reactivity compared to equivalent micron- or millimetre-sized (bulk) particles. However, the effect of soil on solubility, spatial distribution and speciation of ZnO nanoparticles has not yet been investigated. In this study, we examined the diffusion and solid phase speciation of Zn in an alkaline calcareous soil following application of nanoparticulate and bulk ZnO coated fertilizer products (monoammonium phosphate (MAP) and urea) using laboratory-based x-ray techniques and synchrotron-based μ-x-ray fluorescence (μ-XRF) mapping and absorption fine structure spectroscopy (μ-XAFS). Mapping of the soil-fertilizer reaction zones revealed that most of the applied Zn for all treatments remained on the coated fertilizer granule or close to the point of application after five weeks of incubation in soil. Zinc precipitated mainly as scholzite (CaZn2(PO4)2.2H2O) and zinc ammonium phosphate (Zn(NH4)PO4) species at the surface of MAP granules. These reactions reduced dissolution and diffusion of Zn from the MAP granules. Although Zn remained as zincite (ZnO) at the surface of urea granules, limited diffusion of Zn from ZnO-coated urea granules was also observed for both bulk and nanoparticulate ZnO treatments. This might be due to either the high pH of urea granules, which reduced solubility of Zn, or aggregation (due to high ionic strength) of released ZnO nanoparticles around the granule/point of application. The relative proportion of Zn(OH)2 and ZnCO3 species increased for all Zn treatments with increasing distance from coated MAP and urea granules in the calcareous soil. When coated on macronutrient fertilizers, Zn from ZnO nanoparticles (without surface modifiers) was not more mobile or diffusible compared to bulk forms of ZnO. The results also suggest that risk associated with the presence of ZnO NPs in calcareous soils would be the same

  13. [Effect of Long-term Fertilizer Application on the Stability of Organic Carbon in Particle Size Fractions of a Paddy Soil in Zhejiang Province, China].

    PubMed

    Mao, Xia-li; Lu, Kou-ping; Sun, Tao; Zhang, Xiao-kai; He, Li-zhi; Wang, Hai-long

    2015-05-01

    Effects of chemical fertilizers and organic manure on the soil organic carbon (SOC) content in particle size fractions of paddy soil were investigated in a 17-year long-term fertilization field experiment in Zhejiang Province, China. The inherent chemical composition of silt- and clay-associated SOC was evaluated with solid-state 13C-NMR spectroscopy. Compared to CK (no fertilizer treatment), NPKRS (NPK fertilizers plus rice straw) , NPKOM (NPK fertilizers plus organic manure) , NPK (NPK fertilizers) and OM (organic manure alone) treatments significantly (P <0. 05) increased the SOC content of sand- (2-0.02 mm), silt- (0.02-0.002 mm) and clay-sized (< 0.002 mm) fractions. However, no significant difference was observed in the accumulation of silt- and clay-associated SOC between CK and rice straw (RS) treatments. Besides, in comparison with plots applied with NPK fertilizers alone, combined application of organic amendments and NPK fertilizers facilitated the storage of newly sequestered SOC in silt- and clay-sized fractions, which could be more conducive to the stability of SOC. Based on 13C-NMR spectra, both silt and clay fractions were composed of Alkyl-C, O-alkyl-C, Aromatic-C and carbonyl-C. Changes in the relative proportion of different C species were observed between silt and clay fractions: the clay fraction had relatively more Alkyl-C, carbonyl-C and less O-alkyl-C, Aromatic-C than those in the silt fraction. This might be ascribed to the fact that the organic matter complexed with clay was dominated by microbial products, whereas the silt appeared to be rich in aromatic residues derived from plants. The spectra also showed that the relative proportion of different C species was modified by fertilization practices. In comparison with organic amendments alone, the relative proportion of Alkyl-C was decreased by 9.1%-11.9% and 13.7%-19.9% under combined application of organic amendments and chemical fertilizers, for silt and clay, respectively, and that of

  14. Characterization and selection of biochar for an efficient retention of tricyclazole in a flooded alluvial paddy soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biochars, produced from different organic residues, are increasingly proposed as soil amendment for their agronomic and environmental benefits. Nevertheless, a systematic detection method that relates correlates the biochar properties of these biochars to their ability to adsorb organic compounds is...

  15. Organic matter-solid phase interactions are critical for predicting arsenic release and plant uptake in Bangladesh paddy soils.

    PubMed

    Williams, Paul N; Zhang, Hao; Davison, William; Meharg, Andrew A; Hossain, Mahmud; Norton, Gareth J; Brammer, Hugh; Islam, M Rafiqul

    2011-07-15

    Agroecological zones within Bangladesh with low levels of arsenic in groundwater and soils produce rice that is high in arsenic with respect to other producing regions of the globe. Little is known about arsenic cycling in these soils and the labile fractions relevant for plant uptake when flooded. Soil porewater dynamics of field soils (n = 39) were recreated under standardized laboratory conditions to investigate the mobility and interplay of arsenic, Fe, Si, C, and other elements, in relation to rice grain element composition, using the dynamic sampling technique diffusive gradients in thin films (DGT). Based on a simple model using only labile DGT measured arsenic and dissolved organic carbon (DOC), concentrations of arsenic in Aman (Monsoon season) rice grain were predicted reliably. DOC was the strongest determinant of arsenic solid-solution phase partitioning, while arsenic release to the soil porewater was shown to be decoupled from that of Fe. This study demonstrates the dual importance of organic matter (OM), in terms of enhancing arsenic release from soils, while reducing bioavailability by sequestering arsenic in solution. PMID:21692537

  16. The carbon distribution among the functional groups of humic acids isolated by sequential alkaline extraction from gray forest soil

    NASA Astrophysics Data System (ADS)

    Kholodov, V. A.; Konstantinov, A. I.; Perminova, I. V.

    2009-11-01

    Preparations of humic acids (HAs) were isolated from a gray forest soil by sequential alkaline extraction. From a sample of 500 g, HA preparations of 2.24, 0.23, and 0.20 g were obtained from the first, second, and third alkaline extracts, respectively. The structure of the preparations was determined by 13C NMR spectroscopy. At each next extraction step, the portion of aliphatic fragments in the HA preparations increased and the content of aromatic structures decreased. The conclusion was drawn that a single extraction is sufficient for obtaining a representative HA sample.

  17. Bioavailability and release of nonextractable (bound) residues of chiral cycloxaprid using geophagous earthworm Metaphire guillelmi in rice paddy soil.

    PubMed

    Liu, Xuanqi; Xu, Xiaoyong; Zhang, Hanxue; Li, Chao; Shao, Xusheng; Ye, Qingfu; Li, Zhong

    2015-09-01

    The widespread adoption of neonicotinoids has led to a move away from integrated pest management (IPM) and caused adverse effects on non-target invertebrate species. Due to their living in close contact with and consuming large amounts of soil, earthworms are a model organism used to study bioaccumulation. We investigated the bioaccumulation and release of bound, or non-extractable, residues (BRs) of (14)C labeled racemic cycloxaprid (CYC) and its individual enantiomers by the geophagous earthworm Metaphire guillelmi. In a previous work, the fraction of BRs of (14)C-CYC individual enantiomers reached up to 70-85% of the initially spiked radioactivity after 100 d of treatment. The bulk volume of the soil was then diluted by a factor of 15 with fresh soil. Here we showed that after earthworms lived in the soil-bound residues for 28 d, 11-25% of the previously bound radioactivity in soil was extractable by solvent, mineralized to CO2, and accumulated in earthworm tissues. While earthworms were exposed to (14)C-CYC a two-compartment accumulation model could explain the bio-accumulation as individual enantiomers. At the end of the experiment, the biota-sediment accumulation factors were between 0.59 and 0.82, which suggested CYC immobilization in the soil resulted in its bioavailability being reduced which enhanced its degradation. Additionally, the elimination of CYC individual enantiomers from M. guillelmi was fitted to an availability-adjusted decay model with a half-life of 9 d. Stereoselective release or bioavailability between CYC enantiomers was not observed. These results provide the important data about the release of BRs of CYC and potential transfer in the food chain to support the long-term environmental risk assessment of neonicotinoids. PMID:25933294

  18. Effects of elevated ozone concentration on CH4 and N2O emission from paddy soil under fully open-air field conditions.

    PubMed

    Tang, Haoye; Liu, Gang; Zhu, Jianguo; Kobayashi, Kazuhiko

    2015-04-01

    We investigated the effects of elevated ozone concentration (E-O3) on CH4 and N2O emission from paddies with two rice cultivars: an inbred Indica cultivar Yangdao 6 (YD6) and a hybrid one II-you 084 (IIY084), under fully open-air field conditions in China. A mean 26.7% enhancement of ozone concentration above the ambient level (A-O3) significantly reduced CH4 emission at tillering and flowering stages leading to a reduction of seasonal integral CH4 emission by 29.6% on average across the two cultivars. The reduced CH4 emission is associated with O3-induced reduction in the whole-plant biomass (-13.2%), root biomass (-34.7%), and maximum tiller number (-10.3%), all of which curbed the carbon supply for belowground CH4 production and its release from submerged soil to atmosphere. Although no significant difference was detected between the cultivars in the CH4 emission response to E-O3, a larger decrease in CH4 emission with IIY084 (-33.2%) than that with YD6 (-7.0%) was observed at tillering stage, which may be due to the larger reduction in tiller number in IIY084 by E-O3. Additionally, E-O3 reduced seasonal mean NOx flux by 5.7% and 11.8% with IIY084 and YD6, respectively, but the effects were not significant statistically. We found that the relative response of CH4 emission to E-O3 was not significantly different from those reported in open-top chamber experiments. This study has thus confirmed that increasing ozone concentration would mitigate the global warming potential of CH4 and suggested consideration of the feedback mechanism between ozone and its precursor emission into the projection of future ozone effects on terrestrial ecosystem. PMID:25403809

  19. Characterization and selection of biochar for an efficient retention of tricyclazole in a flooded alluvial paddy soil.

    PubMed

    García-Jaramillo, Manuel; Cox, Lucía; Knicker, Heike E; Cornejo, Juan; Spokas, Kurt A; Hermosín, M Carmen

    2015-04-01

    Biochars, from different organic residues, are increasingly proposed as soil amendments for their agronomic and environmental benefits. A systematic detection method that correlates biochar properties to their abilities to adsorb organic compounds is still lacking. Seven biochars obtained after pyrolysis at different temperatures and from different feedstock (alperujo compost, rice hull, and woody debris), were characterized and tested to reveal potential remedial forms for pesticide capture in flooded soils. Biochar properties were determined by nuclear magnetic resonance (NMR) spectroscopy, Fourier transform infrared spectroscopy, specific surface area (SSA) assessment and scanning electron microscopy. In addition, dissolved organic matter (DOM) from these biochars was extracted and quantified in order to evaluate the effect on pesticide sorption. The biochars from alperujo compost presented very high affinity to the fungicide tricyclazole (55.9, 83.5, and 90.3% for B1, B4, and B5, respectively). This affinity was positively correlated with the pyrolysis temperature, the pH, the increased SSA of the biochars, and the enhanced aromaticity. Sorptive capacities were negatively related to DOM contents. The amendment with a mixture of compost and biochar endows the alluvial soil with high sorptive properties (from K(fads(soil)) = 9.26 to K(fads(mixture)) = 17.89) without impeding the slow release of tricyclazole. PMID:25643874

  20. Varying effect of biochar on Cd, Pb and As mobility in a multi-metal contaminated paddy soil.

    PubMed

    Yin, Daixia; Wang, Xin; Chen, Can; Peng, Bo; Tan, Changyin; Li, Hailong

    2016-06-01

    Cd, Pb and As stand as the most prominent contaminants prevailing in Chinese soils. In the present study, biochars derived from water hyacinth (BCW) and rice straw (BCR) were investigated regarding their applicability and durability in soil Cd, Pb, and As immobilization under acid precipitation. Total Cd, Pb, and As in both BCs were below the maximum allowed threshold according to biochar toxicity standard recommended by International Biochar Initiative. To evaluate BCs effect on Cd, Pb, As bioavailability and mobility, CaCl2, KH2PO4 and SPLP extractions were firstly carried out. In neutral extraction with CaCl2 and KH2PO4, significantly reduced Cd/Pb concentrations in CaCl2 extract along with elevated KH2PO4-extractable As were recorded with either BC at 2% or 5%. In SPLP with simulated acid rainwater as extractant, comparable Cd, Pb and As levels were determined in SPLP extract with 2% BCW, while slight to significant increase in SPLP-Cd, Pb or As was recorded with other treatments. Longer-term leaching column test further confirmed the high durability of 2% BCW in Cd immobilization under continuous acid exposure. In parallel, little increase in As concentrations in eluate was determined with 2% BCW compared to no-biochar control, indicating a lowered risk of As mobilization with acid input. However, remarkably higher Pb in leachate from both BCW-only control and 2% BCW-amended soils were noticed at the initial stage of acid leaching, indicating a higher acid-solubility of Pb minerals in BCW (most probably PbO) than in tested soil (PbO2, PbAs2O6). Taken together, BCW exhibited important potential for soil Cd sequestration with little effect on As mobilization under acid precipitation. But it may simultaneously load highly acid-soluble Pb minerals into soils, resulting in elevated Pb mobility upon acid exposure. Therefore, more stringent threshold for Pb content in biochar need to be put forward to secure biochar application in soils subject to anthropogenic

  1. The influence of biochar type on long-term stabilization for Cd and Cu in contaminated paddy soils.

    PubMed

    Li, Hongying; Ye, Xinxin; Geng, Zhigang; Zhou, Hongjian; Guo, Xisheng; Zhang, Yunxia; Zhao, Huijun; Wang, Guozhong

    2016-03-01

    Long-term effect of biochar on PTEs (potential toxic elements) immobilization depends upon biochar own property and its aging process in soil. To understand the role of biachar type on PTEs stabilization, two types of biochar, corn-straw-derived biochar (CB) and hardwood-derived biochar (HB), were compared for their efficacy in achieving a stable decrease in the bio-availability of Cd and Cu in soils. The 3-year pot-culture experiment showed that HB reduced the concentration of CaCl2-extractable Cd and Cu by 57.9 and 63.8% in soil, and Cd and Cu uptake by 63.6 and 56.3% in rice tissue respectively, in the first year, whereas these values increased in the next two years. On the other hand, CB decreased these values steadily year by year. At the end of the 3 years, CB at 5% level had lowered the levels of CaCl2-extractable Cd and Cu by 53.6 and 66.8%, respectively. These variations between CB and HB were due to the differences in the way the two types of biochar age in the soil. The aging process was simulated in the laboratory, and the XPS results showed that the oxidization of the biochars introduced more oxygen-containing groups (especially carboxyl) on the surface of CB than HB, leading to a correspondingly greater number of oxygenated binding sites for Cd and Cu in the case of CB. The content of lignin was the major factor resulting in the variation of oxidation degree in two biochars. These results suggest that it is important to select the right kind of biochar to stably decrease the bio-availability of potential toxic elements (Cd and Cu) in contaminated soils. PMID:26546702

  2. Alternative sorbents for the dispersive solid-phase extraction step in quick, easy, cheap, effective, rugged and safe method for extraction of pesticides from rice paddy soils with determination by liquid chromatography tandem mass spectrometry.

    PubMed

    Arias, Jean Lucas de Oliveira; Rombaldi, Caroline; Caldas, Sergiane Souza; Primel, Ednei Gilberto

    2014-09-19

    The clean-up step is essential to reduce interferences, improve quantification and help to maintain the integrity of the chromatographic system when working with complex matrices. In this study, alternative materials were evaluated as sorbents in the dispersive solid-phase extraction (D-SPE) for the determination and extraction of seventeen pesticides from rice paddy soil samples by the quick, easy, cheap, effective, rugged and safe (QuEChERS) method coupled with liquid chromatography-tandem mass spectrometry (LC-MS/MS). Chitin, chitosan, diatomaceous earth and PSA were compared in terms of extraction efficiency and matrix effect. The best results were achieved when chitosan was used. Quantification limits ranged from 0.1 to 100μgkg(-1). Calibration curves showed correlation coefficient values higher than 0.98. Results of accuracy and precision in the spiked soil samples between 60% and 120%, with a relative standard deviation lower than 20%, were reached for 15 out of 17 pesticides. The matrix effect was evaluated and only one compound was influenced by the matrix components, showing medium effect. Results showed that alternative materials are more effective and less expensive than traditional sorbents which have been usually employed, i.e., they may be used in the D-SPE step during the extraction of pesticides from rice paddy soils. PMID:25115454

  3. Kocuria aegyptia sp. nov., a novel actinobacterium isolated from a saline, alkaline desert soil in Egypt.

    PubMed

    Li, Wen-Jun; Zhang, Yu-Qin; Schumann, Peter; Chen, Hua-Hong; Hozzein, Wael N; Tian, Xin-Peng; Xu, Li-Hua; Jiang, Cheng-Lin

    2006-04-01

    A coccoid, non-motile actinobacterium, designated strain YIM 70003T, was isolated from a saline, alkaline, desert-soil sample from Egypt. Phylogenetic analysis based on 16S rRNA gene sequences revealed that the organism formed a distinct phyletic line within the genus Kocuria and was most closely related to Kocuria polaris DSM 14382T (98.6 % sequence similarity) and Kocuria rosea DSM 20447T (98.2 %). Chemotaxonomic data, including the Lys-Ala3 peptidoglycan type, the presence of phosphatidylglycerol and diphosphatidylglycerol as the predominant phospholipids, the presence of MK-8(H2) and MK-9(H2) as the major menaquinones, the predominance of fatty acids ai-C(15 : 0) and i-C(15 : 0) and the DNA G+C content, also supported the affiliation of the isolate to the genus Kocuria. The low DNA-DNA relatedness with K. polaris DSM 14382T (56.6 %) and K. rosea DSM 20447T (15.5 %) in combination with phenotypic data show that strain YIM 70003T should be classified as a novel species of the genus Kocuria. The name Kocuria aegyptia sp. nov. is proposed, with strain YIM 70003T (=CCTCC AA203006T = CIP 107966T = KCTC 19010T = DSM 17006T) as the type strain. PMID:16585685

  4. Brevundimonas terrae sp. nov., isolated from an alkaline soil in Korea.

    PubMed

    Yoon, Jung-Hoon; Kang, So-Jung; Lee, Jung-Sook; Oh, Tae-Kwang

    2006-12-01

    A Gram-negative, rod-shaped, Brevundimonas-like bacterial strain, KSL-145(T), was isolated from an alkaline soil in Korea and subjected to a polyphasic taxonomic investigation. Strain KSL-145(T) grew optimally at pH 7.5-8.0 and 30 degrees C without NaCl. It was characterized chemotaxonomically as containing Q-10 as the predominant ubiquinone and C(18 : 1)omega7c and C(16 : 0) as the major fatty acids. The DNA G+C content was 61.8 mol%. A phylogenetic analysis based on 16S rRNA gene sequences showed that strain KSL-145(T) fell within the radiation of the cluster comprising Brevundimonas species and Mycoplana bullata. The levels of 16S rRNA gene sequence similarity between strain KSL-145(T) and the type strains of Brevundimonas species and M. bullata ranged from 95.3 to 98.7 %. The mean DNA-DNA relatedness values between strain KSL-145(T) and the type strains of Brevundimonas diminuta and M. bullata, the closest phylogenetic relatives, were 26 and 15 %, respectively. Strain KSL-145(T) could be differentiated from Brevundimonas species and M. bullata by differences in several phenotypic characteristics. On the basis of the phenotypic, phylogenetic and genetic data, strain KSL-145(T) represents a novel species in the genus Brevundimonas, for which the name Brevundimonas terrae sp. nov. is proposed. The type strain is KSL-145(T) (=KCTC 12481(T)=JCM 13476(T)). PMID:17158998

  5. Natural speciation of Mn, Ni and Zn at a micrometer scale in aclayey paddy soil using X-ray fluorescence, absorption anddiffraction

    SciTech Connect

    Manceau, Alain; Tommaseo, Caterina; Rihs, Sophie; Geoffroy,Nicolas; Chateigner, Daniel; Schlegel, Michel; Tisserand, Delphine; Marcus, Matthew A.; Tamura, Nobumichi; Chen, Zueng-Sang

    2005-08-29

    The natural speciation of Mn (0.19 g/kg), Ni (46 mg/kg), and Zn (42 mg/kg) in the argillic horizon (120 cm depth, pH = 5.6) of an Ultisol from a paddy soil in northern Taiwan was investigated by advanced X-ray synchrotron techniques. Microchemical associations were imaged by synchrotron-based X-ray microfluorescence, host minerals were identified by standard and micrometer-resolved X-ray diffraction, and the local coordination environment of Mn, Ni, and Zn was probed using extended X-ray absorption fine structure (EXAFS) spectroscopy on a powdered sample and a soil thin section, and polarized EXAFS spectroscopy on a highly textured self-supporting clay film from the <2 mu m fraction of the soil. Manganese was concentrated in Fe-Mn soft mottles (44.4 g/kg) as turbostratic hexagonal birnessite and lithiophorite having Mn3+/Mn4+atomic ratios of {approx} 20 percent and 50 percent, respectively. Quantitative analysis of high-order scattering paths of the EXAFS spectrum for natural and synthetic (Al0.67Li0.32)(Mn0.684+Mn0.323+)O2(OH)2 lithiophorite revealed that Mn3+ and Mn4+ are ordered in the[(Mn0.684+Mn0.323+)O2]0.32- layer. A structural model is proposed, in which Mn4+ and Mn3+ are ordered similarly to Al and Li in the [(Al0.673+Li0.32+)(OH)2]0.32- layer, with Mn3+ cations being surrounded by six Mn4+, and Mn4+ cations by three Mn3+ and three Mn4+. Similar cation ordering in the manganese and aluminum layers likely provides a more homogeneous local balance of the excess and deficit of charges in each layer and increases the stability of lithiophorite. Ni (r = 0.70Angstrom) substitutes for Mn(r(Mn4+) = 0.54 Angstrom, r(Mn3+) = 0.65Angstrom) in the manganese layer in the natural lithiophorite. In contrast, Zn(r = 0.74 Angstrom) fills vacant sites in the gibbsitic layer of natural lithiophorite, in a similar manner as lithium (r = 0.74) Angstrom in synthetic lithiophorite. The partitioning of Ni and Zn between the two layers is a result of the general preference of Ni

  6. Black carbon accrual during 2000 years of paddy-rice and non-paddy cropping in the Yangtze River Delta, China.

    PubMed

    Lehndorff, Eva; Roth, Philipp J; Cao, Zhi H; Amelung, W

    2014-06-01

    Rice straw burning has accompanied paddy management for millennia, introducing black carbon (BC) into soil as the residue of incomplete combustion. This study examined the contribution of BC to soil organic matter and the rate at which it accumulates in paddy soils as a result of prolonged paddy management. Soil depth profiles were sampled along a chronosequence of 0-2000 years of rice-wheat rotation systems and adjacent non-paddy systems (50-700 years) in the Bay of Hangzhou (Zhejiang province, China). The soil BC content and its degree of condensation were assessed using benzene-polycarboxylic acids (BPCAs) as geochemical markers. The results showed that despite regular long term BC input, BC only contributed 7-11% of total soil organic carbon (SOC) in the topsoil horizons. Nevertheless, along with SOC, paddy soils accumulated BC with increasing duration of management until 297 years to reach a steady-state of 13 t BC ha(-1). This was 1.8 times more than in non-paddy soils. The fate of BC in paddy soils (0-1 m) could be modeled revealing an average annual input of 44 kg ha(-1) yr(-1), and a mean residence time of 303 years. The subsoils contributed at least 50% to overall BC stocks, which likely derived from periods prior to land embankment and episodic burial of ancient topsoil, as also indicated by BPCA pattern changes. We conclude that there is a significant but limited accumulation of C in charred forms upon prolonged paddy management. The final contribution of BC to total SOC in paddy soils was similar to that in other aerobic ecosystems of the world. PMID:24227744

  7. [Effects of tillage-cropping systems on methane and nitrous oxide emissions from agro-ecosystems in a purple paddy soil].

    PubMed

    Zhang, Jun-Ke; Jiang, Chang-Sheng; Hao, Qing-Ju; Tang, Qi-Wen; Cheng, Bing-Hong; Li, Hui; Chen, Lu-Hao

    2012-06-01

    Using the static opaque chamber method, a field experiment, located in the Key Field Station for Monitoring of Eco-Environment of Purple Soil of the Ministry of Agriculture of China in the farm of Southwest University (30 degrees 26'N, 106 degrees 26'E) in Chongqing, was conducted in situ for one year to study the effect of different tillage systems on CH4 and N2O emission from ago-ecosystems in a purple paddy soil. In this paper, four tillage treatments including conventional tillage with rice only system (CT), conventional tillage with rotation of rice and rape system (CTR), no-till and plain culture with rotation of rice and rape system (NTP) and no-till and ridge culture with rotation of rice and rape system (NTR) were selected as research objectives. The results showed that the annual CH4 and N2O emissions were mainly occurred in the rice growing period, and were about 77.6% and 55.0% of the total annual of them emitted from this period. The total annual CH4 under CT was higher than that of other treatments. The annual average flux of CH4[CH4, mg x (m2 x h)(-1)] order was CT (2.96 +/- 0.04) >NTR (1.83 +/- 0.21) >NTP (1.42 +/- 0.01) >CTR (0.96 +/- 0.09); the annual average flux of N2O[N2O, microg x (m2 x h)(-1)] order was CTR (123.6 +/- 47.1) > NTR (115.2 +/- 22.1) > NTP (100.5 +/- 25.8) > CT (81.3 +/- 13.5), and the total annual N2O under CTR was higher than that of CT. The global warming potentials (GWPs) of CH4 and N2O emissions under different tillage-cropping systems were assessed in an integrated way. The results showed that the integrated GWPs of CH4 and N2O emission were in the following sequence: CT > NTR > NTP > CTR, and CTR was the best treatment for decrease the integrated GWPs in this area. PMID:22946185

  8. Degradation of benzo[a]pyrene in an experimentally contaminated paddy soil by vetiver grass (Vetiveria zizanioides).

    PubMed

    Li, H; Luo, Y M; Song, J; Wu, L H; Christie, P

    2006-01-01

    A pot experiment was conducted to study the effect of growing vetiver grass on the biodegradation of benzo[a]pyrene (B[a]P) under glasshouse conditions. Plant biomass, microbial biomass C and degradation of B[a]P were determined. B[a]P disappeared faster in the plant treatments than in unplanted controls. Disappearance of B[a]P was accompanied by an increase in soil microbial biomass C. Vetiver grass may promote the biodegradation of B[a]P under flooded conditions by plant roots by stimulating the microbial biomass. Microbial biomass was the main factor affecting dissipation of B[a]P under flooded conditions. PMID:16528581

  9. Effects of water-saving irrigation on emissions of greenhouse gases and prokaryotic communities in rice paddy soil.

    PubMed

    Ahn, Jae-Hyung; Choi, Min-Young; Kim, Byung-Yong; Lee, Jong-Sik; Song, Jaekyeong; Kim, Gun-Yeob; Weon, Hang-Yeon

    2014-08-01

    The effects of water-saving irrigation on emissions of greenhouse gases and soil prokaryotic communities were investigated in an experimental rice field. The water layer was kept at 1-2 cm in the water-saving (WS) irrigation treatment and at 6 cm in the continuous flooding (CF) irrigation treatment. WS irrigation decreased CH(4) emissions by 78 % and increased N(2)O emissions by 533 %, resulting in 78 % reduction of global warming potential compared to the CF irrigation. WS irrigation did not affect the abundance or phylogenetic distribution of bacterial/archaeal 16S rRNA genes and the abundance of bacterial/archaeal 16S rRNAs. The transcript abundance of CH(4) emission-related genes generally followed CH(4) emission patterns, but the difference in abundance between mcrA transcripts and amoA/pmoA transcripts best described the differences in CH(4) emissions between the two irrigation practices. WS irrigation increased the relative abundance of 16S rRNAs and functional gene transcripts associated with Anaeromyxobacter and Methylocystis spp., suggesting that their activities might be important in emissions of the greenhouse gases. The N(2)O emission patterns were not reflected in the abundance of N(2)O emission-related genes and transcripts. We showed that the alternative irrigation practice was effective for mitigating greenhouse gas emissions from rice fields and that it did not affect the overall size and structure of the soil prokaryotic community but did affect the activity of some groups. PMID:24682309

  10. Field application of electrokinetic remediation for multi-metal contaminated paddy soil using two-dimensional electrode configuration.

    PubMed

    Kim, Woo-Seung; Jeon, Eun-Ki; Jung, Ji-Min; Jung, Hong-Bae; Ko, Sung-Hwan; Seo, Chang-Il; Baek, Kitae

    2014-03-01

    In this study, we evaluated the feasibility of in situ electrokinetic remediation for arsenic (As)-, copper (Cu)-, and lead (Pb)-contaminated soil, in a pilot-scale field application with two-dimensional electrode configurations. Square and hexagonal configurations with different electrode spacing, 1 m and 2 m, were investigated under a constant 100 V. A square configuration with electrode spacing of 2 m removed 61.5 % of As, 11.4 % of Cu, and 0.9 % of Pb, respectively, and a hexagonal configuration with the same spacing showed a higher removal efficiency in top (59 % of As, 0-0.5 m) and middle (53 % of As, 0.5-1.0 m) layers, but much lower removal efficiency in the bottom layer (1-1.5 m), which was thought to be due to groundwater flow through periodic rise and fall of tides. Fractionation analysis showed that As bound to Fe-Mn oxyhydroxide was the main form of As removed by the electrokinetic process. The two-dimensional configuration wasted less electrical energy by Joule heating, and required fewer electrode installations, compared to the one-dimensional electrode configuration. PMID:24338001

  11. Differences in Cellulosic Supramolecular Structure of Compositionally Similar Rice Straw Affect Biomass Metabolism by Paddy Soil Microbiota

    PubMed Central

    Ogura, Tatsuki; Date, Yasuhiro; Kikuchi, Jun

    2013-01-01

    Because they are strong and stable, lignocellulosic supramolecular structures in plant cell walls are resistant to decomposition. However, they can be degraded and recycled by soil microbiota. Little is known about the biomass degradation profiles of complex microbiota based on differences in cellulosic supramolecular structures without compositional variations. Here, we characterized and evaluated the cellulosic supramolecular structures and composition of rice straw biomass processed under different milling conditions. We used a range of techniques including solid- and solution-state nuclear magnetic resonance (NMR) and Fourier transform infrared spectroscopy followed by thermodynamic and microbial degradability characterization using thermogravimetric analysis, solution-state NMR, and denaturing gradient gel electrophoresis. These measured data were further analyzed using an “ECOMICS” web-based toolkit. From the results, we found that physical pretreatment of rice straw alters the lignocellulosic supramolecular structure by cleaving significant molecular lignocellulose bonds. The transformation from crystalline to amorphous cellulose shifted the thermal degradation profiles to lower temperatures. In addition, pretreated rice straw samples developed different microbiota profiles with different metabolic dynamics during the biomass degradation process. This is the first report to comprehensively characterize the structure, composition, and thermal degradation and microbiota profiles using the ECOMICS toolkit. By revealing differences between lignocellulosic supramolecular structures of biomass processed under different milling conditions, our analysis revealed how the characteristic compositions of microbiota profiles develop in addition to their metabolic profiles and dynamics during biomass degradation. PMID:23840554

  12. Impact of cultivation year, nitrogen fertilization rate and irrigation water quality on soil salinity and soil nitrogen in saline-sodic paddy fields in Northeast China

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Saline-sodic soils are a valuable potential arable land resource, and are widely distributed in the western Songnen Plain of Northeast China. Reclaiming and planting rice is an effective and feasible approach for improving saline-sodic soil and increasing food production. Assessment of the effective...

  13. Short-Term Effect of Vermicompost Application on Biological Properties of an Alkaline Soil with High Lime Content from Mediterranean Region of Turkey

    PubMed Central

    Uz, Ilker; Tavali, Ismail Emrah

    2014-01-01

    This study was conducted to investigate direct short-term impact of vermicompost on some soil biological properties by monitoring changes after addition of vermicompost as compared to farmyard manure in an alkaline soil with high lime content from semiarid Mediterranean region of Turkey. For this purpose, mixtures of soil and organic fertilizers in different doses were incubated under greenhouse condition. Soil samples collected in regular intervals were analyzed for biological parameters including dehydrogenase, β-glucosidase, urease, alkaline phosphatase activities, and total number of aerobic mesophilic bacteria. Even though soil dehydrogenase activity appeared to be dose-independent based on overall evaluation, organic amendments were found to elevate dehydrogenase activity when sampling periods are evaluated individually. β-glucosidase, urease, alkaline phosphatase activity, and aerobic mesophilic bacterial numbers in vermicompost treatments fluctuated but remained significantly above the control. A slight but statistically significant difference was detected between organic amendments in terms of urease activity. Vermicompost appeared to more significantly increase bacterial number in soil. Clearly, vermicompost has a potential to be used as an alternative to farmyard manure to improve and maintain soil biological activity in alkaline calcareous soils from the Mediterranean region of Turkey. Further studies are needed to assess its full potential for these soils. PMID:25254238

  14. Short-term effect of vermicompost application on biological properties of an alkaline soil with high lime content from Mediterranean region of Turkey.

    PubMed

    Uz, Ilker; Tavali, Ismail Emrah

    2014-01-01

    This study was conducted to investigate direct short-term impact of vermicompost on some soil biological properties by monitoring changes after addition of vermicompost as compared to farmyard manure in an alkaline soil with high lime content from semiarid Mediterranean region of Turkey. For this purpose, mixtures of soil and organic fertilizers in different doses were incubated under greenhouse condition. Soil samples collected in regular intervals were analyzed for biological parameters including dehydrogenase, β-glucosidase, urease, alkaline phosphatase activities, and total number of aerobic mesophilic bacteria. Even though soil dehydrogenase activity appeared to be dose-independent based on overall evaluation, organic amendments were found to elevate dehydrogenase activity when sampling periods are evaluated individually. β-glucosidase, urease, alkaline phosphatase activity, and aerobic mesophilic bacterial numbers in vermicompost treatments fluctuated but remained significantly above the control. A slight but statistically significant difference was detected between organic amendments in terms of urease activity. Vermicompost appeared to more significantly increase bacterial number in soil. Clearly, vermicompost has a potential to be used as an alternative to farmyard manure to improve and maintain soil biological activity in alkaline calcareous soils from the Mediterranean region of Turkey. Further studies are needed to assess its full potential for these soils. PMID:25254238

  15. Occurrence and bioaccumulation of polybrominated diphenyl ethers in sediments and paddy ecosystems of Liaohe River Basin, northeast China.

    PubMed

    Ma, Xindong; Zhang, Haijun; Yao, Wenjun; Guo, Wen; Li, Depeng; Yao, Ziwei; Chen, Jiping

    2016-05-01

    Concentrations of 16 polybrominated diphenyl ether (PBDE) congeners were measured in river sediments, paddy soils and three species of paddy-field organisms (crab, loach and carp) collected from the Liaohe River Basin, northeastern China. The total contents of PBDEs (∑16PBDEs) in sediments and paddy soils were in the ranges of 273.4-3246.3pg/g dry weight (dw), and 192.1-1783.8pg/gdw, respectively. BDE 209 was the dominant congener both in sediments and paddy soils. The concentrations of ∑16PBDEs in sediments were significantly higher than those in the adjacent paddy soils, indicating a potential transport of PBDEs from river to paddy ecosystems via river water irrigation. The biota-soil accumulation factor (BSAF) was calculated as the ratio between the lipid-normalized concentration in paddy-field organisms and the total organic carbon-normalized concentration in paddy soil. The average BSAF values of ∑15PBDEs followed the sequence of crab (3.6)>loach (3.3)>carp (2.1). BDE 154 had the highest BSAF value, and a parabolic trend between BSAF values of individual PBDE congeners and their logKOW values was observed. In view of the fact that crab had the larger BSAF value and higher lipid content, the ecological risk and health risk for crab cultivation in paddy fields should be of particular concern. PMID:27155431

  16. Kocuria dechangensis sp. nov., an actinobacterium isolated from saline and alkaline soils.

    PubMed

    Wang, Kaibiao; Zhang, Lei; Liu, Yanshuang; Pan, Yuanyuan; Meng, Lin; Xu, Tong; Zhang, Cheng; Liu, Henan; Hong, Shan; Huang, Haipeng; Jiang, Juquan

    2015-09-01

    A Gram-stain positive, strictly aerobic, non-motile and coccus-shaped actinobacterium, designated strain NEAU-ST5-33(T), was isolated from saline and alkaline soils in Dechang Township, Zhaodong City, PR China. It formed beige-yellow colonies and grew at NaCl concentrations of 0-5% (w/v) (optimum 0%), at pH 6.0-9.0 (optimum pH 7.0) and over a temperature range of 4-50 °C (optimum 35 °C). Based on 16S rRNA gene sequence analysis, strain NEAU-ST5-33(T) was phylogenetically closely related to the type strains of species of the genus Kocuria, Kocuria polaris CMS 76or(T), Kocuria rosea DSM 20447(T), Kocuria turfanensis HO-9042(T), Kocuria aegyptia YIM 70003(T), Kocuria himachalensis K07-05(T) and Kocuria flava HO-9041(T), with respective sequence similarities of 98.8%, 98.8%, 98.3%, 98.1%, 98.1% and 97.9%. DNA-DNA hybridization relatedness values of strain NEAU-ST5-33(T) with type strains of the closely related species ranged from 54 ± 1% to 34 ± 1%. The DNA G+C content was 61.2 mol%. The major fatty acids (>5%) were C15 : 0 anteiso, C15 : 0 iso and C16 : 1ω7c and/or C16 : 1ω6c. The major menaquinone detected was MK-8 (H2), and the polar lipids consisted of diphosphatidylglycerol, phosphatidylethanolamine, phosphatidylglycerol, one unknown aminolipid and one unknown lipid. On the basis of the genotypic, chemotaxonomic and phenotypic data, we propose that strain NEAU-ST5-33(T) represents a novel species of the genus Kocuria, with the name Kocuria dechangensis sp. nov. The type strain is NEAU-ST5-33(T) ( = CGMCC 1.12187(T) = DSM 25872(T)). PMID:26048314

  17. Halomonas heilongjiangensis sp. nov., a novel moderately halophilic bacterium isolated from saline and alkaline soil.

    PubMed

    Dou, Guiming; He, Wei; Liu, Hongcan; Ma, Yuchao

    2015-08-01

    A moderately halophilic bacterium, designated strain 9-2(T), was isolated from saline and alkaline soil collected in Lindian county, Heilongjiang province, China. The strain was observed to be strictly aerobic, Gram-negative, rod-shaped, oxidase-positive, catalase-positive and motile. It was found to require NaCl for growth and to grow at NaCl concentrations of 0.5-14 % (w/v) (optimum, 7-10 %, w/v), at temperatures of 10-45 °C (optimum 25-30 °C) and at pH 5.0-10.0 (optimum pH 8.0). Phylogenetic analysis based on 16S rRNA gene sequences revealed that strain 9-2(T) is a member of the genus Halomonas and is closely related to Halomonas desiderata DSM 9502(T) (96.68 %), Halomonas campaniensis DSM 1293(T) (96.46 %), Halomonas ventosae DSM 15911(T) (96.27 %) and Halomonas kenyensis DSM 17331(T) (96.27 %). The DNA-DNA hybridization value was 38.9 ± 0.66 % between the novel isolate 9-2(T) and H. desiderata DSM 9502(T). The predominant ubiquinones were identified as Q9 (75.1 %) and Q8 (24.9 %). The major fatty acids were identified as C16:0 (22.0 %), Summed feature 8 (C18:1 ω6c/C18:1 ω7c, 19.6 %), Summed feature 3 (C16:1 ω6c/C16:1 ω7c, 12.6 %), C12:0 3-OH (12.0 %) and C10:0 (11.7 %). The DNA G+C content was determined to be 69.7 mol%. On the basis of the evidence presented in this study, strain 9-2(T) is considered to represent a novel species of the genus Halomonas, for which the name Halomonas heilongjiangensis sp. nov. is proposed. The type strain is 9-2(T) (=DSM 26881(T) = CGMCC 1.12467(T)). PMID:26036672

  18. Pseudomonas songnenensis sp. nov., isolated from saline and alkaline soils in Songnen Plain, China.

    PubMed

    Zhang, Lei; Pan, Yuanyuan; Wang, Kaibiao; Zhang, Xiaoxia; Zhang, Shuang; Fu, Xiaowei; Zhang, Cheng; Jiang, Juquan

    2015-03-01

    The strain NEAU-ST5-5(T) was isolated from the saline and alkaline soil in Songnen Plain, North East of China. The bacterium was found to be aerobic, Gram-stain negative, rod-shaped and motile by means of several polar flagella. It forms yellow-orange colonies with a radial wrinkled surface. Phylogenetic analyses based on the separate 16S rRNA gene sequences and concatenated 16S rRNA, gyrB and rpoD gene sequences indicated that it belongs to the genus Pseudomonas in the class Gammaproteobacteria. Strain NEAU-ST5-5(T) shows gene sequence similarities of 98.8-97.1 % for 16S rRNA, 90.5-78.4 % for gyrB and 90.4-71.1 % for rpoD with type strains of the closely related species of the genus Pseudomonas, respectively. DNA-DNA hybridization relatedness between strain NEAU-ST5-5(T) and type strains of the most closely related species, Pseudomonas stutzeri DSM 5190(T), P. xanthomarina DSM 18231(T), P. kunmingensis CGMCC 1.12273(T), P. alcaliphila DSM 17744(T) and P. oleovorans subsp. lubricantis DSM 21016(T) were 43 ± 1 to 25 ± 2 %. The major fatty acids (>10 %) were determined to be C18:1 ω7c/C18:1 ω6c, C16:1 ω7c/C16:1 ω6c and C16:0, the predominant respiratory quinone was identified as ubiquinone 9 and polar lipids were found to consist of phosphatidylethanolamine, phosphatidylglycerol, diphosphatidylglycerol, one unknown phospholipid, one unidentified aminophospholipid and one unknown lipid. The genotypic, chemotaxonomic and phenotypic analysis indicated that strain NEAU-ST5-5(T) represents a novel species of the genus Pseudomonas, for which the name Pseudomonas songnenensis sp. nov. is proposed. The type strain is NEAU-ST5-5(T) (=ACCC 06361(T) = DSM 27560(T)). PMID:25550067

  19. Temporal changes of radiocesium in irrigated paddy fields and its accumulation in rice plants in Fukushima.

    PubMed

    Yang, Baolu; Onda, Yuichi; Wakiyama, Yoshifumi; Yoshimura, Kazuya; Sekimoto, Hitoshi; Ha, Yiming

    2016-01-01

    About half of the total paddy field area, which is the dominant agricultural land in Fukushima Prefecture, was contaminated by radiocesium released by the Fukushima Daiichi Nuclear Power Plant accident. In this study, we investigated the temporal changes of radiocesium in soil, irrigation water, and rice plant in two adjacent rice paddies, with and without surface-soil-removal, in Fukushima Prefecture for over three years (2012-2014) after the nuclear accident. Our results showed that radiocesium migrated into 24-28 cm soil layers and that the activity concentration of radiocesium in paddy soils showed a significant reduction in 2014. The newly added radiocesium to paddies through irrigation water contributed only a maximum value of 0.15% and 0.75% of the total amount present in control and decontaminated paddies, respectively, throughout the study period. The radiocesium activity concentration in suspended sediment in irrigation water exponentially decreased, and the effective half-lives (Teff) for (137)Cs and (134)Cs were 1.3 and 0.9 years, respectively. Additionally, the average suspended sediment concentration in irrigation water increased between 2012 and 2014, suggesting that enhanced soil erosion had occurred in the surrounding environment. Radiocesium accumulation in rice plant also decreased with time in both paddies. However, the concentration ratio of radiocesium for rice plant in the decontaminated paddy increased compared with control paddy, despite approximately 96% of fallout radiocesium removed in paddy soil. Further analysis is required to clarify the reasons of high concentration ratio of radiocesium for rice plant in the decontaminated paddy. PMID:26561453

  20. Diversity and food web structure of nematode communities under high soil salinity and alkaline pH.

    PubMed

    Salamún, Peter; Kucanová, Eva; Brázová, Tímea; Miklisová, Dana; Renčo, Marek; Hanzelová, Vladimíra

    2014-10-01

    A long-term and intensive magnesium (Mg) ore processing in Slovenské Magnezitové Závody a.s. in Jelšava has resulted in a high Mg content and alkaline pH of the soil environment, noticeable mainly in the close vicinity of the smelter. Nematode communities strongly reacted to the contamination mostly by a decrease in abundance of the sensitive groups. Nematodes from c-p 1 group and bacterivores, tolerant to pollution played a significant role in establishing the dominance at all sites. With increasing distance from the pollution source, the nematode communities were more structured and complex, with an increase in proportion of sensitive c-p 4 and 5 nematodes, composed mainly of carnivores and omnivores. Various ecological indices (e.g. MI2-5, SI, H') indicated similar improvement of farther soil ecosystems. PMID:24996531

  1. Measurement and estimation of radiocesium discharge rate from paddy field during land preparation and mid-summer drainage.

    PubMed

    Miyazu, Susumu; Yasutaka, Tetsuo; Yoshikawa, Natsuki; Tamaki, Shouhei; Nakajima, Kousei; Sato, Iku; Nonaka, Masanori; Harada, Naoki

    2016-05-01

    In this research, we evaluated the range of (137)Cs discharge rates from paddy fields during land preparation and mid-summer drainage. First, we investigated (137)Cs discharge loads during land preparation and mid-summer drainage and their ratio to the (137)Cs inventory of paddy field soil. We found that total discharge rates were 0.003-0.028% during land preparation and 0.001-0.011% during mid-summer drainage. Next, we validated the range of obtained total discharge of (137)Cs from the paddy fields using a simplified equation and literature review. As a result, we conclude that the range of total outflow loads of suspended solids for the investigated paddy field was generally representative of paddy fields in Japan. Moreover, the (137)Cs discharge ratio had a wide range, but was extremely small relative to (137)Cs present in paddy field soil before irrigation. PMID:26895347

  2. Testing CO2 Sequestration in an Alkaline Soil Treated with Flue Gas Desulfurization Gypsum (FGDG)

    NASA Astrophysics Data System (ADS)

    Han, Y.; Tokunaga, T. K.

    2012-12-01

    Identifying effective and economical methods for increasing carbon storage in soils is of interest for reducing soil CO2 fluxes to the atmosphere in order to partially offset anthropogenic CO2 contributions to climate change This study investigates an alternative strategy for increasing carbon retention in soils by accelerating calcite (CaCO3) precipitation and promoting soil organic carbon (SOC) complexation on mineral surfaces. The addition of calcium ion to soils with pH > 8, often found in arid and semi-arid regions, may accelerate the slow process of calcite precipitation. Increased ionic strength from addition of a soluble Ca source also suppresses microbial activity which oxidizes SOC to gaseous CO2. Through obtaining C mass balances in soil profiles, this study is quantifying the efficiency of gypsum amendments for mitigating C losses to the atmosphere. The objective of this study is to identify conditions in which inorganic and organic C sequestration is practical in semi-arid and arid soils by gypsum treatment. As an inexpensive calcium source, we proposed to use flue gas desulfurization gypsum (FGDG), a byproduct of fossil fuel burning electric power plants. To test the hypothesis, laboratory column experiments have been conducted in calcite-buffered soil with addition of gypsum and FGDG. The results of several months of column monitoring are demonstrating that gypsum-treated soil have lowered amounts of soil organic carbon loss and increased inorganic carbon (calcite) production. The excess generation of FGDG relative to industrial and agricultural needs, FGDG, is currently regarded as waste. Thus application of FGDG application in some soils may be an effective and economical means for fixing CO2 in soil organic and inorganic carbon forms.Soil carbon cycle, with proposed increased C retention by calcite precipitation and by SOC binding onto soil mineral surfaces, with both processes driven by calcium released from gypsum dissolution.

  3. Methane emission from single cropping rice paddies amended different manures

    SciTech Connect

    Du Daodeng; Tao Zhan

    1996-12-31

    Methane emission fluxes were determined from single cropping rice paddies amended with different manures through a productively comparative experiment. The average fluxes in the whole growth season ranged from 3.92 to 10.96 mg/m{sup 2}.hr. The compost amended paddies gave the highest emission fluxes of 10.26 mg/m{sup 2}.hr, while the fluxes from the other manure amended paddies ranked as follows: horse dung biogas digester sediment 10.02, chemical fertilizer only 8.81, nightsoil biogas sediment 7.76, chicken dropping biogas digester sediment 4.48 and pig dung biogas digester sediment 3.92 mg/m{sup 2}.hr. The latter 3 sediments gave the significant less ({alpha} < 0.05) fluxes than compost. The highest fluxes peaks of all treated paddies appeared unanimously between the stages of the midtillering and the earing, with a half of total CH{sub 4} emissions were produced in this period which could be chosen as the key period for control of CH{sub 4} emission from the single cropping rice paddies. The positive correlation of the fluxes with the temperatures in 5 cm soil layers and the negative correlation of the fluxes with the rice yields, the soil N and P{sub 2}O{sub 5} contents were also observed.

  4. Comparing Soil Organic Carbon Dynamics in Perennial Grasses and Shrubs in a Saline-Alkaline Arid Region, Northwestern China

    PubMed Central

    Su, Jiaqi; Zhang, Jingli; Zheng, Yuanrun; Ni, Jian; Xiao, Chunwang; Wang, Renzhong

    2012-01-01

    Background Although semi-arid and arid regions account for about 40% of terrestrial surface of the Earth and contain approximately 10% of the global soil organic carbon stock, our understanding of soil organic carbon dynamics in these regions is limited. Methodology/Principal Findings A field experiment was conducted to compare soil organic carbon dynamics between a perennial grass community dominated by Cleistogenes squarrosa and an adjacent shrub community co-dominated by Reaumuria soongorica and Haloxylon ammodendron, two typical plant life forms in arid ecosystems of saline-alkaline arid regions in northwestern China during the growing season 2010. We found that both fine root biomass and necromass in two life forms varied greatly during the growing season. Annual fine root production in the perennial grasses was 45.6% significantly higher than in the shrubs, and fine root turnover rates were 2.52 and 2.17 yr−1 for the perennial grasses and the shrubs, respectively. Floor mass was significantly higher in the perennial grasses than in the shrubs due to the decomposition rate of leaf litter in the perennial grasses was 61.8% lower than in the shrubs even though no significance was detected in litterfall production. Soil microbial biomass and activity demonstrated a strong seasonal variation with larger values in May and September and minimum values in the dry month of July. Observed higher soil organic carbon stocks in the perennial grasses (1.32 Kg C m−2) than in the shrubs (1.12 Kg C m−2) might be attributed to both greater inputs of poor quality litter that is relatively resistant to decay and the lower ability of microorganism to decompose these organic matter. Conclusions/Significance Our results suggest that the perennial grasses might accumulate more soil organic carbon with time than the shrubs because of larger amounts of inputs from litter and slower return of carbon through decomposition. PMID:22900067

  5. FUNGUS INDEX AND RESIDUAL EFFECTS OF PESTICIDES IN ACID AND ALKALINE SOILS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil applied pesticides have profound effects on the population density and diversity of fungi, however, such information is lacking in tropical soils of the Amazon region. Field experiments were implemented at two experimental farms ("El Choclito", "Bello Horizonte”) of Tropical Crop Institute (ICT...

  6. Chemical stabilization of cadmium in acidic soil using alkaline agronomic and industrial by-products.

    PubMed

    Chang, Yao-Tsung; Hsi, Hsing-Cheng; Hseu, Zeng-Yei; Jheng, Shao-Liang

    2013-01-01

    In situ immobilization of heavy metals using reactive or stabilizing materials is a promising solution for soil remediation. Therefore, four agronomic and industrial by-products [wood biochar (WB), crushed oyster shell (OS), blast furnace slag (BFS), and fluidized-bed crystallized calcium (FBCC)] and CaCO3 were added to acidic soil (Cd = 8.71 mg kg(-1)) at the rates of 1%, 2%, and 4% and incubated for 90 d. Chinese cabbage (Brassica chinensis L.) was then planted in the soil to test the Cd uptake. The elevation in soil pH caused by adding the by-products produced a negative charge on the soil surface, which enhanced Cd adsorption. Consequently, the diethylenetriamine pentaacetic acid (DTPA)-extractable Cd content decreased significantly (P < 0.05) in the incubated soil. These results from the sequential extraction procedure indicated that Cd converted from the exchangeable fraction to the carbonate or Fe-Mn oxide fraction. The long-term effectiveness of Cd immobilization caused by applying the 4 by-products was much greater than that caused by applying CaCO3. Plant shoot biomass clearly increased because of the by-product soil amendment. Cd concentration in the shoots was < 10.0 mg kg(-1) following by-product application, as compared to 24 mg kg(-1) for plants growing in unamended soil. PMID:23947715

  7. Fixation kinetics of chelated and non-chelated zinc in semi-arid alkaline soils: application to zinc management

    NASA Astrophysics Data System (ADS)

    Udeigwe, Theophilus K.; Eichmann, Madeleine; Menkiti, Matthew C.

    2016-07-01

    This study was designed to examine the fixation pattern and kinetics of zinc (Zn) in chelated (ethylenediaminetetraacetic acid, EDTA) and non-chelated mixed micronutrient systems of semi-arid alkaline soils from the Southern High Plains, USA. Soils were characterized for a suite of chemical and physical properties and data obtained from extraction experiments fitted to various kinetic models. About 30 % more plant-available Zn was fixed in the non-chelated system within the first 14 days with only about 18 % difference observed between the two systems by day 90, suggesting that the effectiveness of the chelated compounds tended to decrease over time. The strengths of the relationships of change in available Zn with respect to other micronutrients (copper, iron, and manganese) were higher and more significant in the non-chelated system (average R2 of 0.83), compared to the chelated (average R2 of 0.42). Fixation of plant-available Zn was best described by the power-function model (R2 = 0.94, SE = 0.076) in the non-chelated system, and was poorly described by all the models examined in the chelated system. Reaction rate constants and relationships generated from this study can serve as important tools for micronutrient management and for future micronutrient modeling studies on these soils and other semi-arid regions of the world.

  8. Organic Control of Dioctahedral and Trioctahedral Clay Formation in an Alkaline Soil System in the Pantanal Wetland of Nhecolândia, Brazil

    PubMed Central

    Meunier, Jean-François; Martins-Silva, Elisângela R.; Furian, Sonia

    2016-01-01

    Recent studies have focused on the formation of authigenic clays in an alkaline soil system surrounding lakes of the Nhecolândia region, Pantanal wetland. The presence of trioctahedral Mg-smectites (stevensite and saponite types), which requires low Al and Fe contents in the soil solution for its formation, contrasts with the neoformation of dioctahedral Fe-mica (glauconite, and Fe-illite), which instead requires solutions relatively enriched in Al and Fe. This study aims to understand the conditions of co-existence of both, Mg-smectite and Fe-mica a common clay association in former or modern alkaline soil systems and sediments. The study was carried out along an alkaline soil catena representative of the region. The soil organization revealed that Mg-smectite occur in top soil close to the lake, whereas Fe-mica dominate in the clay fraction of deeper greenish horizons a few meters apart. We propose here that this spatial distribution is controlled by the lateral transfer of Fe and Al with organic ligands. Alkaline organic rich solutions (DOC up to 738 mg L-1) collected in the watertable were centrifuged and filtered through membranes of decreasing pore size (0.45 μm, 0.2 μm, 30 KDa, 10 KDa, 3 KDa) to separate colloidal and dissolved fractions. Fe, Al, Si, Mg and K were analysed for each fraction. Although the filtration had no influence on Si and K contents, almost 90% of Fe (up to 2.3 mg L-1) and Al (up to 7 mg L-1) are retained at the first cutoff threshold of 0.45μm. The treatment of the same solutions by oxygen peroxide before filtration shows that a large proportion of Fe and Al were bonded to organic colloids in alkaline soil solution at the immediate lake border, allowing Mg-smectite precipitation. The fast mineralization of the organic matter a few meters apart from the lake favors the release of Fe and Al necessary for Fe-mica neoformation. In comparison with chemical and mineralogical characteristics of alkaline environments described in the

  9. Organic Control of Dioctahedral and Trioctahedral Clay Formation in an Alkaline Soil System in the Pantanal Wetland of Nhecolândia, Brazil.

    PubMed

    Barbiero, Laurent; Berger, Gilles; Rezende Filho, Ary T; Meunier, Jean-François; Martins-Silva, Elisângela R; Furian, Sonia

    2016-01-01

    Recent studies have focused on the formation of authigenic clays in an alkaline soil system surrounding lakes of the Nhecolândia region, Pantanal wetland. The presence of trioctahedral Mg-smectites (stevensite and saponite types), which requires low Al and Fe contents in the soil solution for its formation, contrasts with the neoformation of dioctahedral Fe-mica (glauconite, and Fe-illite), which instead requires solutions relatively enriched in Al and Fe. This study aims to understand the conditions of co-existence of both, Mg-smectite and Fe-mica a common clay association in former or modern alkaline soil systems and sediments. The study was carried out along an alkaline soil catena representative of the region. The soil organization revealed that Mg-smectite occur in top soil close to the lake, whereas Fe-mica dominate in the clay fraction of deeper greenish horizons a few meters apart. We propose here that this spatial distribution is controlled by the lateral transfer of Fe and Al with organic ligands. Alkaline organic rich solutions (DOC up to 738 mg L-1) collected in the watertable were centrifuged and filtered through membranes of decreasing pore size (0.45 μm, 0.2 μm, 30 KDa, 10 KDa, 3 KDa) to separate colloidal and dissolved fractions. Fe, Al, Si, Mg and K were analysed for each fraction. Although the filtration had no influence on Si and K contents, almost 90% of Fe (up to 2.3 mg L-1) and Al (up to 7 mg L-1) are retained at the first cutoff threshold of 0.45μm. The treatment of the same solutions by oxygen peroxide before filtration shows that a large proportion of Fe and Al were bonded to organic colloids in alkaline soil solution at the immediate lake border, allowing Mg-smectite precipitation. The fast mineralization of the organic matter a few meters apart from the lake favors the release of Fe and Al necessary for Fe-mica neoformation. In comparison with chemical and mineralogical characteristics of alkaline environments described in the

  10. Mapping of arsenic pollution with reference to paddy cultivation in the middle Indo-Gangetic Plains.

    PubMed

    Srivastava, Pankaj Kumar; Singh, Manvi; Gupta, Manjul; Singh, Nandita; Kharwar, Ravindra Nath; Tripathi, Rudra Deo; Nautiyal, Chandra Shekhar

    2015-04-01

    A detailed field study was carried out to monitor (i) the arsenic contents in irrigation groundwater and paddy soil and (ii) the accumulation of arsenic in the roots and grains of different paddy varieties grown in the arsenic-contaminated middle Indo-Gangetic Plains of Northern India. Results showed the highest arsenic contamination in the irrigation groundwater (312 μg l(-1)) and in paddy soil (35 mg kg(-1)) values that were significantly exceeded the recommended threshold values of 100 μg l(-1) (EU) and 20 mg kg(-1) (FAO), respectively. The paddy soil arsenic content ranged from 3 to 35 mg kg(-1) with a mean value of 15 mg kg(-1). The soil arsenic content was found to be influenced by the soil texture, carbon, macronutrients, phosphorus, sulfur, hydrolases, and oxidoreductases properties of the paddy soils as revealed in the principal component analyses. Higher root accumulation (>10 mg kg(-1)) of arsenic was observed in 6 of the 17 paddy varieties grown in the study area. The range of arsenic content accumulated in the paddy roots was 4.1 to 16.2 mg kg(-1) dry weight (dw) and in the grains 0.179 to 0.932 mg kg(-1) dw. Out of 17 paddy varieties, eight had 0 > .55 mg kg(-1) grain arsenic content and were found unsafe for subsistence maximum daily tolerable dietary intake (MTDI) by human beings according to the regulatory standards. PMID:25796519

  11. Repeated annual paper mill and alkaline residuals application affects soil metal fractions.

    PubMed

    Gagnon, Bernard; Robichaud, Annie; Ziadi, Noura; Karam, Antoine

    2014-03-01

    The application of industrial residuals in agriculture may raise concerns about soil and crop metal accumulation. A complete study using a fractionation scheme would reveal build-up in metal pools occurring after material addition and predict the transformation of metals in soil between the different forms and potential metal release into the environment. An experimental study was conducted from 2000 to 2008 on a loamy soil at Yamachiche, Quebec, Canada, to evaluate the effects of repeated annual addition of combined paper mill biosolids when applied alone or with several liming by-products on soil Cu, Zn, and Cd fractions. Wet paper mill biosolids at 0, 30, 60, or 90 Mg ha and calcitic lime, lime mud, or wood ash, each at 3 Mg ha with 30 Mg paper mill biosolids ha, were surface applied after seeding. The soils were sampled after 6 (soybean [ (L.) Merr.]) and 9 [corn ( L.)] crop years and analyzed using the Tessier fractionation procedure. Results indicated that biosolids addition increased exchangeable Zn and Cd, carbonate-bound Cd, Fe-Mn oxide-bound Zn and Cd, organically bound Cu and Zn, and total Zn and Cd fractions but decreased Fe-Mn oxide-bound Cu in the uppermost 30-cm layer. With liming by-products, there was a shift from exchangeable to carbonate-bound forms. Even with very small metals addition, paper mill and liming materials increased the mobility of soil Zn and Cd after 9 yr of application, and this metal redistribution resulted into higher crop grain concentrations. PMID:25602653

  12. Evolution of soil properties and metals in acid and alkaline mine tailing ponds after amendments and microorganisms application

    NASA Astrophysics Data System (ADS)

    Acosta, Jose A.; Faz, Ángel; Zornoza, Raúl; Martínez-Martínez, Silvia; Bech, Jaume

    2015-04-01

    Intense mining activities in the past were carried out in Cartagena-La Unión mining district, SE Spain, and caused excessive accumulation of toxic metals in tailing ponds which poses a high environmental and ecological risk. One of the remediation options gaining considerable interest in recent years is the in situ immobilization of metals. A corresponding reduction in the plant-available metal fraction allows re-vegetation and ecosystem restoration of the heavily contaminated sites. In addition, the use of microorganisms to improve the soil condition is a new tool used to increase spontaneous plant colonization. The aim of this research was to assess the effect of amendments (pig manure, sewage sludge, and lime) and microorganisms on the evolution of soil properties and metals in acid and alkaline tailing ponds and to evaluate the content of metals in Zygophylum fabago one year after amendments application. The study was carried out in two mine ponds (acid and alkaline). Twenty seven square field plots, each one consisting of 4 m2, were located in each pond. Four different doses of microorganism (EM) (0 ml, 20 ml, 100 ml and 200 ml of microorganism solution in each plot) and one dose of pig manure (5 kg per plot), sewage sludge (4 kg per plot) and lime (22 kg per plot) were used. Organic amendment doses were calculated according to European nitrogen legislations, and lime dose was calculated according with the potential acid production through total sulphur oxidation. Three replicates of each treatment (organic amendment + lime + microorganism dose 0, 1, 2, or 3) and control soil (with no amendments) were carried out. Plots were left to the semi-arid climate conditions after the addition of amendments to simulate real potential applications of the results. Soil samples was collected every 4 month from each plot during one year, after this time Zygophylum fabago plants were sampled from each plots. Soil properties including: pH, salinity, total, inorganic and

  13. Effectiveness of recovered magnesium phosphates as fertilizers in neutral and slightly alkaline soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Magnesium phosphates such as struvite (MgNH4PO4x6H2O) can be recovered from municipal, industrial and agricultural wastewaters. However, minimal research has been conducted on the beneficial reuse of these recovered products; conducted research has focused on low pH soils. This study determined wh...

  14. Draft Genome Sequence of Jeotgalibacillus soli DSM 23228, a Bacterium Isolated from Alkaline Sandy Soil

    PubMed Central

    Chan, Kok-Gan; Yaakop, Amira Suriaty; Chan, Chia Sing; Ee, Robson; Tan, Wen-Si; Gan, Han Ming

    2015-01-01

    Jeotgalibacillus soli, a bacterium capable of degrading N-acyl homoserine lactone, was isolated from a soil sample in Portugal. J. soli constitutes the only Jeotgalibacillus species isolated from a non-marine source. Here, the draft genome, several interesting glycosyl hydrolases, and its putative N-acyl homoserine lactonases are presented. PMID:25999554

  15. ECOSYSTEM RESTORATION ON METAL-TOXIC SOILS USING BIOSOLIDS AND ALKALINE BYPRODUCTS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soils in many locations are mineralized or were contaminated by industry (e.g. mine wastes; smelter emissions). Zn-Pb-Ag-Cu ores often caused severe Zn phytotoxicity which killed vegetation and prevented normal colonization; severe N and P infertility also contributed to difficulty of remediation. A...

  16. ECOSYSTEM RESOTRATION ON METAL-TOXIC SOILS USING BIOSOLIDS AND ALKALINE BYPRODUCTS (ABSTRACT)

    EPA Science Inventory

    Soils in many locations are mineralized or were contaminated by industry (e.g. mine wastes; smelter emissions). Zn-Pb-Ag-Cu ores often caused severe Zn phytotoxicity which killed vegetation and prevented normal colonization; severe N and P infertility also contributed to difficul...

  17. ECOSYSTEM RESTORATION ON METAL-TOXIC SOILS USING BIOSOLIDS AND ALKALINE BYPRODUCTS

    EPA Science Inventory

    Soils in many locations are mineralized or were contaminated by industry (e.g. mine wastes; smelter emissions). Zn-Pb-Ag-Cu ores often caused severe Zn phytotoxicity which killed vegetation and prevented normal colonization; severe N and P infertility also contributed to difficul...

  18. Organic and inorganic amendments affect soil concentration and accumulation of cadmium and lead in wheat in calcareous alkaline soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Irrigation with untreated effluent in periurban agriculture could result in accumulation and bioconcentrations of cadmium (Cd) and lead (Pb). Different amendments were used to investigate their effect on availability, concentration, and uptake of metals by wheat in texturally different soils. Crop w...

  19. Isolation and fractionation of soil humin using alkaline urea and dimethylsulphoxide plus sulphuric acid.

    PubMed

    Song, Guixue; Hayes, Michael H B; Novotny, Etelvino H; Simpson, Andre J

    2011-01-01

    Humin, the most recalcitrant and abundant organic fraction of soils and of sediments, is a significant contributor to the stable carbon pool in soils and is important for the global carbon budget. It has significant resistance to transformations by microorganisms. Based on the classical operational definition, humin can include any humic-type substance that is not soluble in water at any pH. We demonstrate in this study how sequential exhaustive extractions with 0.1 M sodium hydroxide (NaOH) + 6 M urea, followed by dimethylsulphoxide (DMSO) + 6% (v/v) sulphuric acid (H(2)SO(4)) solvent systems, can extract 70-80% of the residual materials remaining after prior exhaustive extractions in neutral and aqueous basic media. Solid-state (13)C NMR spectra have shown that the components isolated in the base + urea system were compositionally similar to the humic and fulvic acid fractions isolated at pH 12.6 in the aqueous media. The NMR spectra indicated that the major components isolated in the DMSO + H(2)SO(4) medium had aliphatic hydrocarbon associated with carboxyl functionalities and with lesser amounts of carbohydrate and peptide and minor amounts of lignin-derived components. The major components will have significant contributions from long-chain fatty acids, waxes, to cuticular materials. The isolates in the DMSO + H(2)SO(4) medium were compositionally similar to the organic components that resisted solvation and remained associated with the soil clays. It is concluded that the base + urea system released humic and fulvic acids held by hydrogen bonding or by entrapment within the humin matrix. The recalcitrant humin materials extracted in DMSO + H(2)SO(4) are largely biological molecules (from plants and the soil microbial population) that are likely to be protected from degradation by their hydrophobic moieties and by sorption on the soil clays. Thus, the major components of humin do not satisfy the classical definitions for humic

  20. Isolation and fractionation of soil humin using alkaline urea and dimethylsulphoxide plus sulphuric acid

    NASA Astrophysics Data System (ADS)

    Song, Guixue; Hayes, Michael H. B.; Novotny, Etelvino H.; Simpson, Andre J.

    2011-01-01

    Humin, the most recalcitrant and abundant organic fraction of soils and of sediments, is a significant contributor to the stable carbon pool in soils and is important for the global carbon budget. It has significant resistance to transformations by microorganisms. Based on the classical operational definition, humin can include any humic-type substance that is not soluble in water at any pH. We demonstrate in this study how sequential exhaustive extractions with 0.1 M sodium hydroxide (NaOH) + 6 M urea, followed by dimethylsulphoxide (DMSO) + 6% ( v/ v) sulphuric acid (H2SO4) solvent systems, can extract 70-80% of the residual materials remaining after prior exhaustive extractions in neutral and aqueous basic media. Solid-state 13C NMR spectra have shown that the components isolated in the base + urea system were compositionally similar to the humic and fulvic acid fractions isolated at pH 12.6 in the aqueous media. The NMR spectra indicated that the major components isolated in the DMSO + H2SO4 medium had aliphatic hydrocarbon associated with carboxyl functionalities and with lesser amounts of carbohydrate and peptide and minor amounts of lignin-derived components. The major components will have significant contributions from long-chain fatty acids, waxes, to cuticular materials. The isolates in the DMSO + H2SO4 medium were compositionally similar to the organic components that resisted solvation and remained associated with the soil clays. It is concluded that the base + urea system released humic and fulvic acids held by hydrogen bonding or by entrapment within the humin matrix. The recalcitrant humin materials extracted in DMSO + H2SO4 are largely biological molecules (from plants and the soil microbial population) that are likely to be protected from degradation by their hydrophobic moieties and by sorption on the soil clays. Thus, the major components of humin do not satisfy the classical definitions for humic substances which emphasise that these arise from

  1. Decontamination of metals, pentachlorophenol, and polychlorined dibenzo-p-dioxins and dibenzofurans polluted soil in alkaline conditions using an amphoteric biosurfactant.

    PubMed

    Reynier, Nicolas; Blais, Jean-François; Mercier, Guy; Besner, Simon

    2014-01-01

    In this paper, flotation in acidic conditions and alkaline leaching soil washing processes were compared to decontaminate four soils with variable contamination with metals, pentachlorophenol (PCP), and polychlorodibenzo dioxins and furans (PCDD/F). The measured concentrations of the four soils prior treatment were between 50 and 250 mg/kg for As, 35 and 220mg/kg for Cr, 80 and 350mg/kg for Cu, and 2.5 and 30mg/kg for PCP. PCDD/F concentrations reached 1394, 1375, 3730, and 6289ng/kg for F1, S1, S2, and S3 soils, respectively. The tests were carried out with masses of 100g of soil (fraction 0-2 mm) in a 2 L beaker or in a 1 L flotation cell. Soil flotation in sulphuric acid for 1 h at 60 degreeC with three flotation cycles using the surfactant cocamidopropyl betaine (BW) at 1% allows the solubilization of metals and PCP with average removal yields of 85%, 51%, 90%, and 62% for As, Cr, Cu, and PCP, respectively. The alkaline leaching for 2 h at 80 degreeC solubilizes As, Cr, Cu, and PCP with average removal yields of 60%, 32%, 77%, and 87%, respectively. Tests on PCDD/F solubilization with different surfactants were carried out in combination with the alkaline leaching process. PCDD/F removal yields of 25%, 72%, 70%, and 74% for F1, S1, S2, and S3 soils, respectively, were obtained using the optimized conditions. PMID:24600855

  2. Arsenic behavior in paddy fields during the cycle of flooded and non-flooded periods.

    PubMed

    Takahashi, Yoshio; Minamikawa, Reiko; Hattori, Kéiko H; Kurishima, Katsuaki; Kihou, Nobuharu; Yuita, Kouichi

    2004-02-15

    The behavior of As in paddy fields is of great interest considering high As contents of groundwater in several Asian countries where rice is the main staple. We determined the concentrations of Fe, Mn, and As in soil, soil water, and groundwater samples collected at different depths down to 2 m in an experimental paddy field in Japan during the cycle of flooded and non-flooded periods. In addition, we measured the oxidation states of Fe, Mn, and As in situ in soil samples using X-ray absorption near-edge structure (XANES) and conducted sequential extraction of the soil samples. The results show that Fe (hydr)oxide hosts As in soil. Arsenic in irrigation waters is incorporated in Fe (hydr)oxide in soil during the non-flooded period, and the As is quickly released from soil to water during the flooded period because of reductive dissolution of the Fe (hydr)oxide phase and reduction of As from As(V) to As(III). The enhancement of As dissolution by the reduction of As is supported by high As/Fe ratios of soil water during the flooded period and our laboratory experiments where As(III) concentrations and As(III)/As(V) ratios in submerged soil were monitored. Our work, primarily based on data from an actual paddy field, suggests that rice plants are enriched in As because the rice grows in flooded paddy fields when mobile As(III) is released to soil water. PMID:14998016

  3. One millimetre makes the difference: high-resolution analysis of methane-oxidizing bacteria and their specific activity at the oxic–anoxic interface in a flooded paddy soil

    PubMed Central

    Reim, Andreas; Lüke, Claudia; Krause, Sascha; Pratscher, Jennifer; Frenzel, Peter

    2012-01-01

    Aerobic methane-oxidizing bacteria (MOB) use a restricted substrate range, yet >30 species-equivalent operational taxonomical units (OTUs) are found in one paddy soil. How these OTUs physically share their microhabitat is unknown. Here we highly resolved the vertical distribution of MOB and their activity. Using microcosms and cryosectioning, we sub-sampled the top 3-mm of a water-saturated soil at near in situ conditions in 100-μm steps. We assessed the community structure and activity using the particulate methane monooxygenase gene pmoA as a functional and phylogenetic marker by terminal restriction fragment length polymorphism (t-RFLP), a pmoA-specific diagnostic microarray, and cloning and sequencing. pmoA genes and transcripts were quantified using competitive reverse transcriptase PCR combined with t-RFLP. Only a subset of the methanotroph community was active. Oxygen microprofiles showed that 89% of total respiration was confined to a 0.67-mm-thick zone immediately above the oxic–anoxic interface, most probably driven by methane oxidation. In this zone, a Methylobacter-affiliated OTU was highly active with up to 18 pmoA transcripts per cell and seemed to be adapted to oxygen and methane concentrations in the micromolar range. Analysis of transcripts with a pmoA-specific microarray found a Methylosarcina-affiliated OTU associated with the surface zone. High oxygen but only nanomolar methane concentrations at the surface suggested an adaptation of this OTU to oligotrophic conditions. No transcripts of type II methanotrophs (Methylosinus, Methylocystis) were found, which indicated that this group was represented by resting stages only. Hence, different OTUs within a single guild shared the same microenvironment and exploited different niches. PMID:22695859

  4. Environmental controls over methyl halide emissions from rice paddies

    NASA Astrophysics Data System (ADS)

    Redeker, K. R.; Cicerone, R. J.

    2004-03-01

    This paper examines primary controlling factors that affect methyl halide emissions from rice paddy ecosystems. Observations of four cultivars under multiple growth conditions during studies in commercial fields and the University of California, Irvine, greenhouse lead to the conclusion that daily emissions of methyl halides are primarily determined by the growth stage of the rice plant, with the exception that methyl chloride emissions show no clear seasonal pattern. Methyl chloride emissions appear to be more from the paddy water and/or soil as opposed to the plants; however, in soils with high chloride content, these emissions appear to peak during the reproductive phase. Strong secondary influences include air temperature, soil halide concentration, and soil pore water saturation. The cultivars studied had statistically separate seasonally integrated emissions. Irradiant light and aboveground biomass appear to have little effect on emissions. Emissions of methyl chloride, methyl bromide, and methyl iodide are estimated to be 3.5, 2.3, and 48 mg/m2/yr, or 5.3, 3.5, and 72 Gg/yr, from rice paddies globally.

  5. Phytoactinopolyspora alkaliphila sp. nov., an alkaliphilic actinomycete isolated from a saline-alkaline soil.

    PubMed

    Zhang, Yong-Guang; Lu, Xin-Hua; Ding, Yan-Bo; Zhou, Xing-Kui; Li, Li; Guo, Jian-Wei; Wang, Hong-Fei; Duan, Yan-Qing; Li, Wen-Jun

    2016-05-01

    An alkaliphilic, filamentous actinomycete, designated EGI 80629T, was isolated from a soil sample of Xinjiang, north-west China. Strain EGI 80629T grew at pH 6.0-11.0 (optimum pH 9.0-10.0) and in the presence of 0-13.0 % NaCl (optimum 3.0-5.0 %). The isolate formed fragmented substrate mycelia, and aerial hyphae with short spore chains with rod-like spores. Whole-cell hydrolysates of the isolate contained ll-diaminopimelic acid as the diagnostic diamino acid, and mannose and rhamnose as diagnostic sugars. The major fatty acids identified were iso-C15 : 0, iso-C16 : 0, anteiso-C15 : 0 and iso-C17 : 0. The predominant menaquinone was MK-9(H4), while the polar lipids were diphosphatidylglycerol, phosphatidylglycerol, two phosphatidylinositol mannosides, five unknown phospholipids, three unknown phosphoglycolipids, one unknown glycolipid, four unknown polar lipids and one unknown aminophospholipid. The G+C content of the genomic DNA was 67.3 mol%. Phylogenetic analysis based on 16S rRNA gene sequences showed that strain EGI 80629T clustered with the genus Phytoactinopolyspora. The 16S rRNA gene sequence similarity between strain EGI 80629T and Phytoactinopolyspora endophytica EGI 60009T was 96.8 %. Based on morphological, chemotaxonomic and phylogenetic characteristics, strain EGI 80629T represents a novel species of the genus Phytoactinopolyspora, for which the name Phytoactinopolyspora alkaliphila sp. nov. is proposed. The type strain is EGI 80629T ( = CGMCC 4.7225T = KCTC 39701T). PMID:26920762

  6. Groundwater impact on methane emissions from flooded paddy fields

    NASA Astrophysics Data System (ADS)

    Rizzo, A.; Boano, F.; Revelli, R.; Ridolfi, L.

    2015-09-01

    High methane (CH4) fluxes emitted from paddy fields strongly contribute to the accumulation of greenhouse gases into the atmosphere, compromising the eco-compatibility of one of the most important world foods. A strong link exists between infiltration rates of irrigation water and CH4 emissions. Since depth to the groundwater table affects infiltration rates, a relevant groundwater impact is expected on CH4 emissions from paddy fields. In this work, a theoretical approach is adopted to investigate the aquifer effect on CH4 dynamics in paddies. Infiltration rates are strongly affected by the development of different connection states between aquifer and irrigation ponded water. A strong reduction in infiltration rates results from a water table near to the soil surface, when the system is hydraulically connected. When the groundwater level increases, the infiltration rate reduction due to the switch from disconnected to connected state promotes a relevant increase of CH4 emissions. This is due to a strong reduction of dissolved organic carbon (DOC) percolation, which leads to higher DOC availability for microbial CH4 production and, consequently, higher CH4 emissions. Our simulations show that CH4 fluxes can be reduced by up to 24% when groundwater level is decreased and the aquifer is disconnected from ponding water. In paddies with shallow aquifers, lowering the water table with a drainage system could thus represent a promising CH4 mitigation option.

  7. Spatial landuse planning using land evaluation and dynamic system to define sustainable area of paddy field: Case study in Karawang Regency, West Java, Indonesia

    NASA Astrophysics Data System (ADS)

    Widiatmaka, Widiatmaka; Ambarwulan, Wiwin; Firmansyah, Irman; Munibah, Khursatul; Santoso, Paulus B. K.

    2015-04-01

    Indonesia is the country with the 4th largest population in the worlds; the population reached more than 237 million people. With rice as the staple food for more than 95 percent of the population, there is an important role of paddy field in Indonesian food security. Actually, paddy field in Java has produced 52,6% of the total rice production in Indonesia, showing the very high dependence of Indonesia on food production from paddy fields in Java island. Karawang Regency is one of the regions in West Java Province that contribute to the national food supply, due to its high soil fertility and its high extent of paddy field. Dynamics of land use change in this region are high because of its proximity to urban area; this dynamics has led to paddy field conversion to industry and residential landuse, which in turn change the regional rice production capacity. Decreasing paddy field landuse in this region could be serve as an example case of the general phenomena which occurred in Javanese rice production region. The objective of this study were: (i) to identify the suitable area for paddy field, (ii) to modelize the decreasing of paddy field in socio-economic context of the region, and (iii) to plan the spatial priority area of paddy field protection according to model prediction. A land evaluation for paddy was completed after a soil survey, while IKONOS imagery was analyzed to delineate paddy fields. Dynamic system model of paddy field land use is built, and then based on the model built, the land area of paddy field untill 2040 in some scenarios was developped. The research results showed that the land suitability class for paddy fields in Karawang Regency ranged from very suitable (S1) to marginally suitable (S3), with various land characteristics as limiting factors. The model predicts that if the situation of paddy field land use change continues in its business as usual path, paddy field area that would exist in the region in 2040 will stay half of the recent

  8. Fipronil application on rice paddy fields reduces densities of common skimmer and scarlet skimmer

    PubMed Central

    Kasai, Atsushi; Hayashi, Takehiko I.; Ohnishi, Hitoshi; Suzuki, Kazutaka; Hayasaka, Daisuke; Goka, Koichi

    2016-01-01

    Several reports suggested that rice seedling nursery-box application of some systemic insecticides (neonicotinoids and fipronil) is the cause of the decline in dragonfly species noted since the 1990s in Japan. We conducted paddy mesocosm experiments to investigate the effect of the systemic insecticides clothianidin, fipronil and chlorantraniliprole on rice paddy field biological communities. Concentrations of all insecticides in the paddy water were reduced to the limit of detection within 3 months after application. However, residuals of these insecticides in the paddy soil were detected throughout the experimental period. Plankton species were affected by clothianidin and chlorantraniliprole right after the applications, but they recovered after the concentrations decreased. On the other hand, the effects of fipronil treatment, especially on Odonata, were larger than those of any other treatment. The number of adult dragonflies completing eclosion was severely decreased in the fipronil treatment. These results suggest that the accumulation of these insecticides in paddy soil reduces biodiversity by eliminating dragonfly nymphs, which occupy a high trophic level in paddy fields. PMID:26979488

  9. Fipronil application on rice paddy fields reduces densities of common skimmer and scarlet skimmer.

    PubMed

    Kasai, Atsushi; Hayashi, Takehiko I; Ohnishi, Hitoshi; Suzuki, Kazutaka; Hayasaka, Daisuke; Goka, Koichi

    2016-01-01

    Several reports suggested that rice seedling nursery-box application of some systemic insecticides (neonicotinoids and fipronil) is the cause of the decline in dragonfly species noted since the 1990s in Japan. We conducted paddy mesocosm experiments to investigate the effect of the systemic insecticides clothianidin, fipronil and chlorantraniliprole on rice paddy field biological communities. Concentrations of all insecticides in the paddy water were reduced to the limit of detection within 3 months after application. However, residuals of these insecticides in the paddy soil were detected throughout the experimental period. Plankton species were affected by clothianidin and chlorantraniliprole right after the applications, but they recovered after the concentrations decreased. On the other hand, the effects of fipronil treatment, especially on Odonata, were larger than those of any other treatment. The number of adult dragonflies completing eclosion was severely decreased in the fipronil treatment. These results suggest that the accumulation of these insecticides in paddy soil reduces biodiversity by eliminating dragonfly nymphs, which occupy a high trophic level in paddy fields. PMID:26979488

  10. Simulating the dissipation of two herbicides using micro paddy lysimeters.

    PubMed

    Nhung, Dang Thi Tuyet; Phong, Thai Khanh; Watanabe, Hirozumi; Iwafune, Takashi; Thuyet, Dang Quoc

    2009-11-01

    A set of packed micro paddy lysimeters, placed in a greenhouse, was used to simulate the dissipation of two herbicides, simetryn and thiobencarb, in a controlled environment. Data from a field monitoring study in 2003, including the soil condition and water balances, were used in the simulation. The herbicides were applied and monitored over a period of 21 d. The water balances under two water management scenarios, intermittent irrigation management (AI) and continuous irrigation management (CI), were simulated. In the AI scenario, the pattern of herbicide dissipation in the surface water of the field were simulated, following the first-order kinetics. In the CI scenario, similarity was observed in most lysimeter and field concentrations, but there were differences in some data points. Dissipation curves of both herbicides in the surface water of the two simulated scenarios were not significantly different (P>0.05) from the field data except for intercept of the thiobencarb curve in the CI scenario. The distribution of simetryn and thiobencarb in the soil profile after simulation were also similar to the field data. The highest concentrations of both herbicides were found on the topsoil layer at 0-2.5 cm depth. Only a small amount of herbicides moved down to the deeper soil layers. Micro paddy lysimeters are thus a good alternative for the dissipation study of pesticides in the paddy environment. PMID:19811801

  11. Mobility and Bioavailability of Technetium in Rice Paddy Fields

    SciTech Connect

    Uchida, S.; Tagami, K.

    2003-02-24

    Field observations and radiotracer experiments were carried out to investigate the behavior of 99Tc in paddy fields. The concentrations of global fallout 99Tc in soil collected from paddy fields in Japan were 6-88 milli-bequerels per kilogram (mBq/kg)-dry and activity ratios of 99Tc to 137Cs ranged from 1.1 x 10-3 to 7.0 x 10-3 with an average of (4.8 {+-} 2.1) x 10-3. (The theoretical activity ratio from nuclear fission yield is presently calculated as 3.3 x 10-4 with correction for radioactive decay.) This result implies that there was a tendency for 99Tc to accumulate in rice paddy fields. To understand the mechanisms of the accumulation, a sequential extraction method was applied over a 6-month period to waterlogged soils contaminated with TcO4-. From the results, it was clear that the TcO4- in soil under waterlogged conditions was readily changed to other insoluble physicochemical forms, such as TcO2, TcS2 and organically bound forms.

  12. Influence of the nonexchangeable potassium of mica on radiocesium uptake by paddy rice.

    PubMed

    Eguchi, Tetsuya; Ohta, Takeshi; Ishikawa, Tetsuya; Matsunami, Hisaya; Takahashi, Yoshihiko; Kubo, Katashi; Yamaguchi, Noriko; Kihou, Nobuharu; Shinano, Takuro

    2015-09-01

    A pot cultivation experiment was conducted to elucidate the influence of the nonexchangeable potassium (K) of mica on radiocesium ((137)Cs) uptake by paddy rice (Oryza sativa L. cv. Koshihikari), and to evaluate the potential of mica application as a countermeasure to reduce radiocesium transfer from soil to paddy rice. The increase in the exchangeable K concentrations of soils, measured before planting, due to mica (muscovite, biotite, and phlogopite) application was negligible. However, in trioctahedral mica (biotite and phlogopite)-treated soil, the release of nonexchangeable K from the mica interlayer maintained the soil-solution K at a higher level during the growing season in comparison to the control, and consequently decreased the (137)Cs transfer factor for brown rice (TF). The sodium tetraphenylboron (TPB)-extractable K concentration of the soils, measured before planting, was strongly negatively correlated with the TF, whereas the exchangeable K concentration of the soils, also measured before planting, was not correlated with the TF. Therefore, we conclude that TPB-extractable K is more reliable than exchangeable K as a basis of fertilizer recommendations for radiocesium-contaminated paddy fields. Phlogopite-treated soils exhibited higher TPB-extractable K concentrations and lower TF values than biotite-treated soils. We thus conclude that phlogopite application is an effective countermeasure to reduce radiocesium uptake in paddy rice. PMID:26026983

  13. Tier 1 Rice Model for Estimating Pesticide Concentrations in Rice Paddies

    EPA Science Inventory

    The Tier 1 Rice Model estimates screening level aquatic concentrations of pesticides in rice paddies. It is a simple pesticide soil:water partitioning model with default values for water volume, soil mass, and organic carbon. Pesticide degradation is not considered in the mode...

  14. Methane Emissions From Global Paddy Rice Agriculture - a New Estimate Based on DNDC Model Simulations

    NASA Astrophysics Data System (ADS)

    Hagen, S. C.; Li, C.; Salas, W.; Ingraham, P.; Li, J.; Beach, R.; Frolking, S.

    2012-12-01

    Roughly one-quarter of global methane emissions to the atmosphere come from the agricultural sector. Agricultural emissions are dominated by livestock (ruminants) and paddy-rice agriculture. We report on a new estimate of global methane emissions from paddy rice c.2010, based on DNDC model simulations of rice cropping around the world. We first generated a global map of rice cropping at 0.5°-resolution, based on existing global crop maps and various other published data. For each 0.5° grid cell that has rice agriculture, we simulated all rice cropping systems that our mapping indicated to be occurring there - irrigated and/or rainfed; single-rice, double-rice, triple-rice, and/or rice-rotated with other upland crops - under local climate and soil conditions, with assumptions about crop management (e.g., fertilizer type and amount, irrigation, flooding frequency and duration, manure application, tillage, crop residue management). We estimate global paddy rice emissions at 23 Tg CH4/yr from 120 Mha of rice paddies (land area) and 160 Mha of rice cropping (harvested area) for the baseline management scenario. We also report on the spatial distribution of these emissions, and the impacts of various management alternatives (flooding methods, fertilizer types, crop residue incorporation etc.) on yield, soil carbon sequestration and emissions of methane and nitrous oxide. For example, simulations with continuous flooding on all paddies increased simulated global paddy rice emissions to 33 Tg CH4/yr, while simulations where all fertilizer was applied as ammonium sulfate reduced simulated global paddy rice emissions to about 19 Tg CH4/yr. Simulated global paddy rice yield was about 320 Tg C in grain.

  15. Depth distribution of radiocesium in Fukushima paddy fields three years after the accident

    NASA Astrophysics Data System (ADS)

    Lepage, Hugo; Laceby, J. Patrick; Evrard, Olivier; Onda, Yuichi; Lefèvre, Irène; Ayrault, Sophie

    2015-04-01

    Rice paddy fields located in the vicinity of the Fukushima Dai-Ichi Nuclear Power Plant (FDNPP) were contaminated by radioactive fallout from the March 2011 accident. Although many studies have investigated the fate of radiocesium in soil in the months following the accident, the potential migration of radiocesium in rice paddy fields requires further examination after major typhoons occurred in this region in 2011 and 2013. Further investigations are also required because paddy fields are typically comprised of Andosols, a soil type in which radiocesium has been known to potentially migrate deeper in the depth profile. To investigate the depth migration of radiocesium we collected soil cores in 10 paddy fields located less than 20 km from the FDNPP in November 2013. The maximum depth penetration of 137Cs was attributed to field maintenance (e.g. grass cutting) (97% of 137Cs in the upper 5-cm) and farming operations (tillage/cultivation - 83% of 137Cs in the upper 5-cm). The low migration observed in undisturbed paddy fields could be attributed to the presence of phyllosilicates that were detected by X-ray diffraction in Andosols. As radiocesium is mainly located in the uppermost soil layers, we recommend the rapid removal of these upper layers (e.g. the top 5 cm) to reduce radiocesium export during erosive events such as the major typhoons known to impact the region. Further research is required to thoroughly understand the impacts of erosion on the transfer and migration of radiocesium throughout the Fukushima Prefecture.

  16. Impact of long-term fertilization on the composition of denitrifier communities based on nitrite reductase analyses in a paddy soil.

    PubMed

    Chen, Zhe; Luo, Xiqian; Hu, Ronggui; Wu, Minna; Wu, Jinshui; Wei, Wenxue

    2010-11-01

    The effect of long-term fertilization on soil-denitrifying communities was determined by measuring the abundance and diversity of the nitrite reductase genes nirK and nirS. Soil samples were collected from plots of a long-term fertilization experiment started in 1990, located in Taoyuan (110°72″ E, 28°52″ N), China. The treatments were no fertilizer (NF), urea (UR), balanced mineral fertilizers (BM), and BM combined with rice straw (BMR). The abundance, diversity, and composition of the soil-denitrifying bacteria were determined by using real-time quantitative PCR, terminal restriction fragment length polymorphism (T-RFLP), and cloning and sequencing of nirK and nirS genes. There was a pronounced difference in the community composition and diversity of nirK-containing denitrifiers responding to the long-term fertilization regimes; however, less variation was observed in communities of nirS-containing denitrifiers, indicating that denitrifiers possessing nirK were more sensitive to the fertilization practices than those with nirS. In contrast, fertilization regimes had similar effects on the copy numbers of nirK and nirS genes. The BMR treatment had the highest copy numbers of nirK and nirS, followed by the two mineral fertilization regimes (UR and BM), and the lowest was in the NF treatment. Of the measured soil parameters, the differences in the community composition of nirK and the abundance of nir denitrifiers were highly correlated with the soil carbon content. Therefore, long-term fertilization resulted in a strong impact on the community structure of nirK populations only, and total organic carbon was the dominant factor in relation to the variations of nir community sizes. PMID:20563573

  17. The effectiveness of ferrous iron and sodium dithionite for decreasing resin-extractable Cr(VI) in Cr(VI)-spiked alkaline soils.

    PubMed

    Cheng, Chia-Jung; Lin, Tzu-Huei; Chen, Chiou-Pin; Juang, Kai-Wei; Lee, Dar-Yuan

    2009-05-30

    Ferrous iron, Na(2)S(2)O(4), and a mixture of Fe(II) and Na(2)S(2)O(4) (4:1 mol/mol) were tested for their effectiveness for decreasing resin-extractable Cr(VI) in alkaline Cr(VI)-spiked soils. The results indicated that adding those reductants greatly decreased the amount of resin-extractable Cr(VI) when the application rate of reductants equaled the number of equivalents of dichromate added to the Cr(VI)-spiked soils. This was mainly as a result of the Cr(VI) reduction into Cr(III), as supported by the XANES spectra. Among the tested reductants, a mixture of Fe(II) and Na(2)S(2)O(4) was the most effective to decrease resin-extractable Cr(VI). The extent to which resin-extractable Cr(VI) and soil pH were decreased was affected by the pH of the reductants. Among the tested reductants at various pH, FeSO(4) at pH below 1 was the most effective in decreasing resin-extractable Cr(VI) in alkaline soils. However, the soil pH was the most decreased as well. On the other hand, the mixtures of ferrous iron and dithionite at a wide range of pH were all efficient (>70% efficiency) in decreasing resin-extractable Cr(VI). Moreover, the extent of the decrease in soil pH was much smaller than that by FeSO(4) (pH<1) alone, and thus the possibility of the Cr(III) hazard can be avoided. PMID:18824300

  18. Bacillus lindianensis sp. nov., a novel alkaliphilic and moderately halotolerant bacterium isolated from saline and alkaline soils.

    PubMed

    Dou, Guiming; Liu, Hongcan; He, Wei; Ma, Yuchao

    2016-01-01

    Two alkaliphilic and halotolerant Gram-stain positive, rod-shaped and endospore-forming bacteria, designated strains 12-3(T) and 12-4, were isolated from saline and alkaline soils collected in Lindian county, Heilongjiang province, China. Both strains were observed to grow well at a wide range of temperature and pH values, 10-45 °C and pH 8-12, with optimal growth at 37 °C and pH 9.0, respectively. Growth of the two strains was found to occur at total salt concentrations of 0-12 % (w/v), with an optimum at 4 % (w/v). The G+C contents of the genomic DNA of strains 12-3(T) and 12-4 were determined to be 42.7 and 42.4 mol%, respectively, and the major cellular fatty acids were identified as anteiso-C15:0 and anteiso-C17:0. In isolate 12-3(T), meso-diaminopimelic acid was found to be the diagnostic diamino acid of the cell wall peptidoglycan; diphosphatidylglycerol, phosphatidylethanolamine and phosphatidylglycerol were identified as the major cellular polar lipids; and menaquinone-7 was identified as the predominant isoprenoid quinone. Strains 12-3(T) and 12-4 share very close 16S rRNA gene sequence similarity (99.74 %) and their DNA-DNA relatedness was 95.3 ± 0.63 %, meaning that the two strains can be considered to belong to the same species. 16S rRNA gene sequence-based phylogenetic analysis revealed strains 12-3(T) and 12-4 exhibit high similarities to Bacillus pseudofirmus DSM 8715(T) (98.7 %), Bacillus marmarensis DSM 21297(T) (97.2 %) and Bacillus nanhaiisediminis CGMCC 1.10116(T) (97.1 and 97.0 %, respectively). DNA-DNA hybridization values between isolate 12-3(T) and the type strains of closely related Bacillus species were below 30 %. On the basis of the polyphasic evidence presented, strains 12-3(T) and 12-4 are considered to represent a novel species of the genus Bacillus, for which the name Bacillus lindianensis sp. nov. is proposed. The type strain is 12-3(T) (DSM 26864(T) = CGMCC 1.12717(T)). PMID:26604103

  19. A field study on heavy metals phytoattenuation potential of monocropping and intercropping of maize and/or legumes in weakly alkaline soils.

    PubMed

    Zhu, Saiyong; Ma, Xinwang; Guo, Rui; Ai, Shiwei; Liu, Bailin; Zhang, Wenya; Zhang, Yingmei

    2016-10-01

    The study focused on the phytoattenuation effects of monocropping and intercropping of maize (Zea mays) and/or legumes on Cu, Zn, Pb, and Cd in weakly alkaline soils. Nine growth stages of monocropping maize were chosen to study the dynamic process of extraction of heavy metals. The total content of heavy metals extracted by the aerial part of monocropped maize increased in a sigmoidal pattern over the effective accumulative temperature. The biggest biomass, highest extraction content, and lowest heavy metals bioaccumulation level occurred at physiological maturity. Among the different planting patterns, including monocropping and intercropping of maize and/or soybean (Glycine max), pea (Pisum sativum), and alfalfa (Medicago sativa), the extraction efficiency of Cu, Zn, Pb, and Cd varied greatly. Only intercropping of maize and soybean yielded relatively higher extraction efficiency for the four metals with no significant difference in the total biomass. Moreover, the heavy metals concentrations in dry biomass from all the planting patterns in the present study were within China's national legal thresholds for fodder use. Therefore, slightly polluted alkaline soils can be safely used through monocropping and intercropping of maize and/or legumes for a range of purposes. In particular, this study indicated that intercropping improves soil ecosystems polluted by heavy metals compared with monocropping. PMID:27159531

  20. Persistence behaviour of thiamethoxam and lambda cyhalothrin in transplanted paddy.

    PubMed

    Barik, Suhrid Ranjan; Ganguly, Pritam; Kunda, Samir Kumar; Kole, Ramen Kumar; Bhattacharyya, Anjan

    2010-10-01

    A field study was conducted in Pre-Kharif season 2007 on paddy to determine the persistence of thiamethoxam (12.6%) and lambda cyhalothrin (9.4%) [in a 'Readymix' formulation Alika 247 ZC], following the application of 33 g. a.i. ha⁻¹ (T₁) and 66 g. a.i. ha⁻¹ (T₂). Spraying of insecticide was done during milking stage of the crop (63 days after transplantation). Thiamethoxam and lambda cyhalothrin residues were estimated by HPLC and GLC respectively. The half-life values were 5.2-5.8 and 4.8 days for thiamethoxam and lambda cyhalothrin respectively. No residue was detected in the harvested paddy, straw, grain, and soil samples. PMID:20703448

  1. Mapping South Korea's Paddy Rice During 2001-2015 Based on Landsat Images

    NASA Astrophysics Data System (ADS)

    Huang, Y.; Ryu, Y.; Jiang, C.

    2015-12-01

    Agricultural land use change substantially affects terrestrial water and carbon cycles, and it is also significant for food security. Rice is an important food crop in South Korea, and its planting area has changed over the past years due to climate change and social development. However, the paddy rice maps in South Korea with high spatial, temporal resolutions and quality are still unavailable. In this study, annual paddy rice planting areas in South Korea during 2001-2015 were extracted using the phenology-based and artificial neural networks(ANN)-based method according to the availability of Landsat images. Three types of vegetation indices, Normalized Difference Vegetation Index(NDVI), Normalized Difference Water Index (NDWI) and Land Surface Water Index (LSWI), were calculated for both methods. For the phenology-based method, we calculated difference and ratio of the vegetation indices from the Landsat images before and after the inundating/transplanting phase, and set the extraction thresholds for rice paddy using the training samples. For the ANN-based method, using the vegetation indices of the Landsat image after inundation, slope and soil type data of the training samples as input, an ANN was established for rice paddy identification. The resultant maps of paddy rice were evaluated using validation samples and agricultural statistics. Finally, we analyzed the spatial and temporal patterns of South Korea's rice paddy during 2001-2015, and investigated the possible reasons.

  2. Human brains found in a fire-affected 4000-years old Bronze Age tumulus layer rich in soil alkalines and boron in Kutahya, Western Anatolia.

    PubMed

    Altinoz, M A; Ince, B; Sav, A; Dincer, A; Cengiz, S; Mercan, S; Yazici, Z; Bilgen, M N

    2014-02-01

    Undecomposed human bodies and organs always attracted interest in terms of understanding biological tissue stability and immortality. Amongst these, cases of natural mummification found in glaciers, bog sediments and deserts caused even more attention. In 2010, an archeological excavation of a Bronze Age layer in a tumulus near the Western Anatolia city Kütahya revealed fire affected regions with burnt human skeletons and charred wooden objects. Inside of the cracked skulls, undecomposed brains were discernible. To analyze the burial taphonomy of the rare phenomenon of brain preservation, we analyzed brains, bone, teeth and surrounding soils elements using Inductively Coupled Plasma-Mass Spectrometer (ICP-MS). Adipocere formation or saponification of postmortem tissue fat requires high levels of alkalinity and especially potassium. Indeed, ICP-MS analysis of the brain, teeth and bone and also of the surrounding soil revealed high levels of potassium, magnesium, aluminum and boron, which are compatible with the famous role of Kütahya in tile production with its soil containing high level of alkalines and tile-glazing boron. Fatty acid chromatography revealed simultaneous saturation of fats and protection of fragile unsaturated fatty acids consistent with soil-presence of both pro-oxidant and anti-oxidant trace metals. Computerized tomography revealed protection of diencephalic, metencephalic and occipital tissue in one of the best-preserved specimens. Boron was previously found as an intentional preservative of Tutankhamen and Deir el Bahari mummies. Here, in natural soil with its insect-repellant, anti-bacterial and fire-resistance qualities it may be a factor to preserve heat-affected brains as almost bioporcellain specimens. PMID:24060546

  3. Effects of supplementary composts on microbial communities and rice productivity in cold water paddy fields.

    PubMed

    Xie, Kaizhi; Xu, Peizhi; Yang, Shaohai; Lu, Yusheng; Jiang, Ruiping; Gu, Wenjie; Li, Wenying; Sun, Lili

    2015-05-01

    Cold water paddy field soils are relatively unproductive, but can be ameliorated by supplementing with inorganic fertilizer from animal waste-based composts. The yield of two rice cultivars was significantly raised by providing either chicken manure or cow dung-based compost. The application of these composts raised the soil pH as well as both the total nitrogen and ammonium nitrogen content, which improved the soil's fertility and raised its nitrification potential. The composts had a measurable effect on the abundance of nitrogencycling- related soil microbes, as measured by estimating the copy number of various bacterial and archaeal genes using quantitative real-time PCR. The abundance of ammonia oxidizing archaea and bacteria was markedly encouraged by the application of chicken manure-based compost. Supplementation with the composts helped promote the availability of soil nitrogen in the cold water paddy field, thereby improving the soil's productivity and increasing the yield of the rice crop. PMID:25406532

  4. High-quality permanent draft genome sequence of Ensifer medicae strain WSM244, a microsymbiont isolated from Medicago polymorpha growing in alkaline soil

    SciTech Connect

    Ardley, Julie; Tian, Rui; O’Hara, Graham; Seshadri, Rekha; Reddy, T. B. K.; Pati, Amrita; Woyke, Tanja; Markowitz, Victor; Ivanova, Natalia; Kyrpides, Nikos; Howieson, John; Reeve, Wayne

    2015-12-01

    We report that Ensifer medicae WSM244 is an aerobic, motile, Gram-negative, non-spore-forming rod that can exist as a soil saprophyte or as a legume microsymbiont of Medicago species. WSM244 was isolated in 1979 from a nodule recovered from the roots of the annual Medicago polymorpha L. growing in alkaline soil (pH 8.0) in Tel Afer, Iraq. WSM244 is the only acid-sensitive E. medicae strain that has been sequenced to date. It is effective at fixing nitrogen with M. polymorpha L., as well as with more alkaline-adapted Medicago spp. such as M. littoralis Loisel., M. scutellata (L.) Mill., M. tornata (L.) Mill. and M. truncatula Gaertn. This strain is also effective with the perennial M. sativa L. Here we describe the features of E. medicae WSM244, together with genome sequence information and its annotation. The 6,650,282 bp high-quality permanent draft genome is arranged into 91 scaffolds of 91 contigs containing 6,427 protein-coding genes and 68 RNA-only encoding genes, and is one of the rhizobial genomes sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) project proposal.

  5. High-quality permanent draft genome sequence of Ensifer medicae strain WSM244, a microsymbiont isolated from Medicago polymorpha growing in alkaline soil

    DOE PAGESBeta

    Ardley, Julie; Tian, Rui; O’Hara, Graham; Seshadri, Rekha; Reddy, T. B. K.; Pati, Amrita; Woyke, Tanja; Markowitz, Victor; Ivanova, Natalia; Kyrpides, Nikos; et al

    2015-12-01

    We report that Ensifer medicae WSM244 is an aerobic, motile, Gram-negative, non-spore-forming rod that can exist as a soil saprophyte or as a legume microsymbiont of Medicago species. WSM244 was isolated in 1979 from a nodule recovered from the roots of the annual Medicago polymorpha L. growing in alkaline soil (pH 8.0) in Tel Afer, Iraq. WSM244 is the only acid-sensitive E. medicae strain that has been sequenced to date. It is effective at fixing nitrogen with M. polymorpha L., as well as with more alkaline-adapted Medicago spp. such as M. littoralis Loisel., M. scutellata (L.) Mill., M. tornata (L.)more » Mill. and M. truncatula Gaertn. This strain is also effective with the perennial M. sativa L. Here we describe the features of E. medicae WSM244, together with genome sequence information and its annotation. The 6,650,282 bp high-quality permanent draft genome is arranged into 91 scaffolds of 91 contigs containing 6,427 protein-coding genes and 68 RNA-only encoding genes, and is one of the rhizobial genomes sequenced as part of the DOE Joint Genome Institute 2010 Genomic Encyclopedia for Bacteria and Archaea-Root Nodule Bacteria (GEBA-RNB) project proposal.« less

  6. Mercury methylation in rice paddies and its possible controlling factors in the Hg mining area, Guizhou province, Southwest China.

    PubMed

    Zhao, Lei; Qiu, Guangle; Anderson, Christopher W N; Meng, Bo; Wang, Dingyong; Shang, Lihai; Yan, Haiyu; Feng, Xinbin

    2016-08-01

    Understanding mercury (Hg) methylation/demethylation processes and the factors controlling methylmercury (MeHg) production within the rice paddy ecosystem of Hg mining areas is critical to assess the risk of MeHg contamination in rice grain. Two typical Hg-contaminated mining sites, a current-day artisanal site (Gouxi) and an abandoned site (Wukeng), were chosen in this study. We qualified the in situ specific methylation/demethylation rate constants in rice paddy soil during a complete rice-growing season. Our results demonstrate that MeHg levels in rice paddy soil were a function of both methylation and demethylation processes and the net methylation potential in the rice paddy soil reflected the measured MeHg production at any time point. Sulfate stimulating the activity of sulfate-reducing bacteria was a potentially important metabolic pathway for Hg methylation in rice paddies. We suggest that bioavailable Hg derived from new atmospheric deposition appears to be the primary factor regulating net MeHg production in rice paddies. PMID:27176759

  7. Arbuscular mycorrhizal fungal diversity, root colonization, and soil alkaline phosphatase activity in response to maize-wheat rotation and no-tillage in North China.

    PubMed

    Hu, Junli; Yang, Anna; Zhu, Anning; Wang, Junhua; Dai, Jue; Wong, Ming Hung; Lin, Xiangui

    2015-07-01

    Monitoring the effects of no-tillage (NT) in comparison with conventional tillage (CT) on soil microbes could improve our understanding of soil biochemical processes and thus help us to develop sound management strategies. The objective of this study was to compare the species composition and ecological function of soil arbuscular mycorrhizal (AM) fungi during the growth and rotation of crops under NT and CT. From late June 2009 to early June 2010, 32 topsoil (0-15 cm) samples from four individual plots per treatment (CT and NT) were collected at both the jointing and maturation stages of maize (Zea mays L.) and wheat (Triticum aestivum L.) from a long-term experimental field that was established in an Aquic Inceptisol in North China in June 2006. The AM fungal spores were isolated and identified and then used to calculate species diversity indices, including the Shannon- Wiener index (H'), Evenness (E), and Simpson's index (D). The root mycorrhizal colonization and soil alkaline phosphatase activity were also determined. A total of 34 species of AM fungi within nine genera were recorded. Compared with NT, CT negatively affected the soil AM fungal community at the maize sowing stage, leading to decreases in the average diversity indices (from 2.12, 0.79, and 0.82 to 1.79, 0.72, and 0.74 for H', E, and D, respectively), root mycorrhizal colonization (from 28% to 20%), soil alkaline phosphatase activity (from 0.24 to 0.19 mg/g/24 h) and available phosphorus concentration (from 17.4 to 10.5 mg/kg) at the maize jointing stage. However, reductions in diversity indices of H', E, and D were restored to 2.20, 0.81, and 0.84, respectively, at the maize maturation stage. CT should affect the community again at the wheat sowing stage; however, a similar restoration in the species diversity of AM fungi was completed before the wheat jointing stage, and the highest Jaccard index (0.800) for similarity in the species composition of soil AM fungi between CT and NT was recorded at

  8. Characterizing Spatiotemporal Dynamics of Methane Emissions from Rice Paddies in Northeast China from 1990 to 2010

    PubMed Central

    Zhang, Yuan; Su, Shiliang; Zhang, Feng; Shi, Runhe; Gao, Wei

    2012-01-01

    Background Rice paddies have been identified as major methane (CH4) source induced by human activities. As a major rice production region in Northern China, the rice paddies in the Three-Rivers Plain (TRP) have experienced large changes in spatial distribution over the recent 20 years (from 1990 to 2010). Consequently, accurate estimation and characterization of spatiotemporal patterns of CH4 emissions from rice paddies has become an pressing issue for assessing the environmental impacts of agroecosystems, and further making GHG mitigation strategies at regional or global levels. Methodology/Principal Findings Integrating remote sensing mapping with a process-based biogeochemistry model, Denitrification and Decomposition (DNDC), was utilized to quantify the regional CH4 emissions from the entire rice paddies in study region. Based on site validation and sensitivity tests, geographic information system (GIS) databases with the spatially differentiated input information were constructed to drive DNDC upscaling for its regional simulations. Results showed that (1) The large change in total methane emission that occurred in 2000 and 2010 compared to 1990 is distributed to the explosive growth in amounts of rice planted; (2) the spatial variations in CH4 fluxes in this study are mainly attributed to the most sensitive factor soil properties, i.e., soil clay fraction and soil organic carbon (SOC) content, and (3) the warming climate could enhance CH4 emission in the cool paddies. Conclusions/Significance The study concluded that the introduction of remote sensing analysis into the DNDC upscaling has a great capability in timely quantifying the methane emissions from cool paddies with fast land use and cover changes. And also, it confirmed that the northern wetland agroecosystems made great contributions to global greenhouse gas inventory. PMID:22235268

  9. [Effects of simulated acid rain on decomposition of soil organic carbon and crop straw].

    PubMed

    Zhu, Xue-Zhu; Huang, Yao; Yang, Xin-Zhong

    2009-02-01

    To evaluate the effects of acid rain on the organic carbon decomposition in different acidity soils, a 40-day incubation test was conducted with the paddy soils of pH 5.48, 6.70 and 8.18. The soils were amended with 0 and 15 g x kg(-1) of rice straw, adjusted to the moisture content of 400 g x kg(-1) air-dried soil by using simulated rain of pH 6.0, 4.5, and 3.0, and incubated at 20 degrees C. The results showed that straw, acid rain, and soil co-affected the CO2 emission from soil system. The amendment of straw increased the soil CO2 emission rate significantly. Acid rain had no significant effects on soil organic carbon decomposition, but significantly affected the straw decomposition in soil. When treated with pH 3.0 acid rain, the amount of decomposed straw over 40-day incubation in acid (pH 5.48) and alkaline (pH 8.18) soils was 8% higher, while that in neutral soil (pH 6.70) was 15% lower, compared to the treatment of pH 6.0 rain. In the treatment of pH 3.0 acid rain, the decomposition rate of soil organic C in acid (pH 5.48) soil was 43% and 50% (P < 0.05) higher than that in neutral (pH 6.70) and alkaline (pH 8.18) soils, while the decomposition rate of straw in neutral soil was 17% and 16% (P < 0.05) lower than that in acid and alkaline soils, respectively. PMID:19459394

  10. Quantitative Eatimation of Ground Water Recharge Process in Vadose Zone Beneath a Rice Paddy Field Using Cross-Borehole Radar

    NASA Astrophysics Data System (ADS)

    Kuroda, S.; Shiina, Y.; Okuyama, T.; Takeutch, M.

    2005-12-01

    Wet Rice Paddy field is one of most important components of land uses in monsoon Asia. It is known to have some other beneficial functions than food production, for example ground water recharge, purification of surface and subsurface water, and alleviation of flood. Though ground water recharge process of paddy field is essential for those functions, the actual conditions of ground water recharge process beneath paddy field has not been clarified besides in the zone of about 1m depth from soil surface. Recently cross borehole radar is recognized as one of usefull methods for measurement of soil water distribution and its change. We applied cross borehole radar for monitoring of soil water in vadose zone beneath a paddy field to clarify the ground water recharge process. Cross borehole radar monitoring clarified the infiltration process into the vadose zone and shallow ground water aquifer beneath the paddy field. We estimated the increment of soil volumetric water content from CRIME model, the descent velocity of wetting front, and infiltration rate from cross borehole radar data quantitatively. They were almost coincident with the directly measured results. Using these results,we tried to estimate permeability based on some hypothesis of infiltration process.

  11. Plants increase arsenic in solution but decrease the non-specifically bound fraction in the rhizosphere of an alkaline, naturally rich soil.

    PubMed

    Obeidy, Carole; Bravin, Matthieu N; Bouchardon, Jean-Luc; Conord, Cyrille; Moutte, Jacques; Guy, Bernard; Faure, Olivier

    2016-04-01

    We aimed at determining the major physical-chemical processes that drive arsenic (As) dynamic in the rhizosphere of four species (Holcus lanatus, Dittrichia viscosa, Lotus corniculatus, Plantago lanceolata) tested for phytostabilization. Experiments were performed with an alkaline soil naturally rich in As. Composition of the soil solution of planted and unplanted pots was monitored every 15 days for 90 days, with a focus on the evolution of As concentrations in solution and in the non-specifically bound (i.e. easily exchangeable) fraction. The four species similarly increased As concentration in solution, but decreased As concentration in the non-specifically bound fraction. The major part (60%) of As desorbed from the non-specifically bound fraction in planted pots was likely redistributed on the less available fractions of As on the solid phase. A second part (35%) of desorbed As was taken up by plants. The minor part (5%) of desorbed As supplied As increase in solution. To conclude, plants induced a substantial redistribution of As on the less available fractions in the rhizosphere, as expected in phytostabilization strategies. Plants however concomitantly increased As concentration in the rhizosphere solution which may contribute to As transfer through plant uptake and leaching. PMID:26707185

  12. Effects of changes in straw chemical properties and alkaline soils on bacterial communities engaged in straw decomposition at different temperatures

    PubMed Central

    Zhou, Guixiang; Zhang, Jiabao; Zhang, Congzhi; Feng, Youzhi; Chen, Lin; Yu, Zhenghong; Xin, Xiuli; Zhao, Bingzi

    2016-01-01

    Differences in the composition of a bacterial community engaged in decomposing wheat straw in a fluvo-aquic soil at 15 °C, 25 °C, and 35 °C were identified using barcode pyrosequencing. Functional carbon groups in the decomposing wheat straw were evaluated by 13C-NMR (nuclear magnetic resonance). Actinobacteria and Firmicutes were more abundant, whereas Alphaproteobacteria and Bacteroidetes were less abundant, at higher temperatures during the later stages of decomposition. Differences in the chemical properties of straw accounted for 19.3% of the variation in the community composition, whereas soil properties accounted for more (24.0%) and temperature, for less (7.4%). Carbon content of the soil microbial biomass and nitrogen content of straw were significantly correlated with the abundance of Alphaproteobacteria, Actinobacteria, and Bacteroidetes. The chemical properties of straw, especially the NCH/OCH3, alkyl O-C-O, and O-alkyl functional groups, exercised a significant effect on the composition of the bacterial community at different temperatures during decomposition—results that extend our understanding of bacterial communities associated with the decomposition of straw in agro-ecosystems and of the effects of temperature and chemical properties of the decomposing straw and soil on such communities. PMID:26916902

  13. Eco-toxicological effects of two kinds of lead compounds on forest tree seed in alkaline soil.

    PubMed

    Yang, Nan; Zhou, Fu-Rong; Wang, Jin-Xin

    2016-03-01

    In order to compare the different eco-toxicological effects of lead nitrate and lead acetate on forest tree seed, a biological incubation experiment was conducted to testify the inhibition effects of two lead compounds on rates of seed germination, root and stem elongation, and seedling fresh weight for six plants (Amaorpha fruticosa L., Robinia psedoacacia L., Pinus tabuliformis Carr., Platycladus orientalis L., Koelreuteria paniculata Laxm., Hippophae rhamnoides L.) in soil. The results indicate that the inhibition effects of the two lead compounds on the rates of root elongation of plants were greater than other indices; root elongation can possibly be used as indices to investigate the relationship between lead toxicity and plant response. The response of trees to lead toxicity varied significantly, and the order of tolerance to lead pollution was as follows: Amaorpha fruticosa L. > Platycladus orientalis L. > Koelreuteria paniculata Laxm. > Robinia psedoacacia L. > Pinus tabuliformis Carr. > Hippophae rhamnoides L. Therefore, we suggest that Amaorpha fruticosa L. and Platycladus orientalis L. be used as tolerant plants for soil phytoremediation and Hippophae rhamnoides L. as an indicative plant to diagnose the toxicity of lead pollution on soil quality. Lead nitrate and lead acetate differentially restrain seeds, with seeds being more sensitive to lead nitrate than lead acetate in the soil. Thus, the characteristics of lead compounds should be taken into full consideration to appraise its impact on the environment. PMID:26927657

  14. A CHEMICAL EQUILIBRIA MODEL OF STRONTIUM-90 ADSORPTION AND TRANSPORT IN SOIL IN RESPONSE TO DYNAMIC ALKALINE CONDITIONS

    EPA Science Inventory

    Strontium-90 is a major hazardous contaminant of radioactive wastewater and its processing sludges at many Department of Energy (DOE) facilities. In the past, such contaminated wastewater and sludge has been disposed in soil seepage pits, lagoons, or cribs often under highly pert...

  15. Field investigation to assess nutrient emission from paddy field to surface water in river catchment

    NASA Astrophysics Data System (ADS)

    Kogure, Kanami; Aichi, Masaatsu; Zessner, Matthias

    2015-04-01

    In order to maintain good river environment, it is remarkably important to understand and to control nutrient behavior such as Nitrogen and Phosphorus. Our former research dealing with nutrient emission analysis in the Tone River basin area in Japan, in addition to urban and industrial waste water, nutrient emission from agricultural activity is dominant pollution source into the river system. Japanese style agriculture produces large amount of rice and paddy field occupies large areas in Japanese river basin areas. While paddy field can deteriorate river water quality by outflow of fertilizer, it is also suggested that paddy field has water purification function. As we carried out investigation in the Tone River Basin area, data were obtained which dissolved nitrogen concentration is lower in discharging water from paddy field than inflowing water into the field. Regarding to nutrient emission impact from paddy field, sufficient data are required to discuss quantitatively seasonal change of material behavior including flooding season and dry season, difference of climate condition, soil type, and rice species, to evaluate year round comprehensive impact from paddy field to the river system. In this research, field survey in paddy field and data collection relating rice production were carried out as a preliminary investigation to assess how Japanese style paddy field contributes year round on surface water quality. Study sites are three paddy fields located in upper reach of the Tone River basin area. The fields are flooded from June to September. In 2014, field investigations were carried out three times in flooding period and twice in dry period. To understand characteristics of each paddy field and seasonal tendency accompanying weather of agricultural event, short term investigations were conducted and we prepare for further long term investigation. Each study site has irrigation water inflow and outflow. Two sites have tile drainage system under the field and

  16. Radiocesium discharge from paddy fields with different initial scrapings for decontamination after the Fukushima Dai-ichi Nuclear Power Plant accident.

    PubMed

    Wakahara, Taeko; Onda, Yuich; Kato, Hiroaki; Sakaguchi, Aya; Yoshimura, Kazuya

    2014-11-01

    To explore the behavior of radionuclides released after the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) accident in March 2011, and the distribution of radiocesium in paddy fields, we monitored radiocesium (Cs) and suspended sediment (SS) discharge from paddy fields. We proposed a rating scale for measuring the effectiveness of surface soil removal. Our experimental plots in paddy fields were located ∼40 km from the FDNPP. Two plots were established: one in a paddy field where surface soil was not removed (the "normally cultivated paddy field") and the second in a paddy field where the top 5-10 cm of soil was removed before cultivation (the "surface-removed paddy field"). The amounts of Cs and SS discharge from the paddy fields were continuously measured from June to August 2011. The Cs soil inventory measured 3 months after the FDNPP accident was approximately 200 kBq m(-2). However, after removing the surface soil, the concentration of Cs-137 decreased to 5 kBq m(-2). SS discharged from the normally cultivated and surface-removed paddy fields after puddling (mixing of soil and water before planting rice) was 11.0 kg and 3.1 kg, respectively, and Cs-137 discharge was 630,000 Bq (1240 Bq m(-2)) and 24,800 Bq (47.8 Bq m(-2)), respectively. The total amount of SS discharge after irrigation (natural rainfall-runoff) was 5.5 kg for the normally cultivated field and 70 kg for the surface-removed field, and the total amounts of Cs-137 discharge were 51,900 Bq (102 Bq m(-2)) and 165,000 Bq (317 Bq m(-2)), respectively. During the irrigation period, discharge from the surface-removed plot showed a twofold greater inflow than that from the normally cultivated plot. Thus, Cs inflow may originate from the upper canal. The topsoil removal process eliminated at least approximately 95% of the Cs-137, but upstream water contaminated with Cs-137 flowed into the paddy field. Therefore, to accurately determine the Cs discharge, it is important to examine Cs inflow from the

  17. A comparison of methane emissions following rice paddies conversion to crab-fish farming wetlands in southeast China.

    PubMed

    Hu, Zhiqiang; Wu, Shuang; Ji, Cheng; Zou, Jianwen; Zhou, Quansuo; Liu, Shuwei

    2016-01-01

    Rice paddies and aquaculture wetlands are typical agricultural wetlands that constitute one of the important sources of atmospheric methane (CH4). Traditional transplanted rice paddies have been experiencing conversion to pond aquaculture wetlands for pursuing higher economic benefits over the past decades in southeast China. A parallel field experiment was carried out to compare CH4 emissions from a transplanted rice paddy and its converted crab-fish farming wetland in southeast China. Over the rice-growing season, CH4 fluxes averaged 1.86 mg m(-2) h(-1) from rice paddies, and 1.14 and 0.50 mg m(-2) h(-1) for the treatments with or without aquatic vegetation present in the crab-fish farming wetlands, respectively. When averaged across the treatments, seasonal CH4 emissions from crab-fish framing wetlands were 52% lower than those from rice paddies. The CH4 fluxes were negatively related to water dissolved oxygen (DO) concentration but positively related to soil/sediment dissolved organic carbon (DOC) content in crab-fish farming wetlands. Dependence of CH4 fluxes on DO or DOC was intensified by the aquatic vegetation presence. By extrapolating the present CH4 emission rate with the current rice paddy-converted aquaculture cultivation area, the seasonal CH4 emissions from inland aquaculture wetlands during the critical farming stage (20 June to 18 October) were estimated to be 33.6 Gg ha(-1) in southeast China in 2012. Rice paddies conversion to crab-fish farming wetlands might have reduced CH4 emissions by 22-54% in mainland China. Results of this study suggest that the conversion of transplanted rice paddies to crab-fish aquaculture wetlands for higher economic benefits would also lead to a lower ecosystem CH4 release rate. PMID:26374545

  18. Examining the fixation kinetics of chelated and non-chelated copper micronutrient and the applications to micronutrient management in semi-arid alkaline soils

    NASA Astrophysics Data System (ADS)

    Udeigwe, T. K.; Eichmann, M. B.; Menkiti, M. C.

    2015-10-01

    The relationship between the deficiency of a nutrient in plants and its total concentration in the soil is complex. This study examined and compared the fixation and fixation kinetics of copper (Cu) in chelated (Ethylene diamine tetraacetic acid, EDTA) and non-chelated mixed systems of micronutrients in the semi-arid soils of the Southern High Plains, US using findings from Cu extraction studies and kinetic models. Approximately, 22 % more Cu was fixed in the non-chelated system within the first 14 days with only 7 % difference between the two systems by day 90. Findings suggest a decrease in the effectiveness of chelated micronutrient over time, highlighting the significance of timing even when chelated micronutrients are applied. The strengths of the relationship of change in available Cu with respect to other micronutrients [iron (Fe), manganese (Mn), and zinc (Zn)] were higher in the non-chelated system (R2: 0.68-0.94), compared to the chelated (R2: 0.42-0.81) with slopes of 0.40 (Cu-Fe), 0.31 (Cu-Mn), and 1.04 (Cu-Zn) in the non-chelated system and 0.26 (Cu-Fe), 0.22 (Cu-Mn), and 0.90 (Cu-Zn) in the chelated. Reduction in the amount of available Cu was best described by the power function model (R2 = 0.91, SE = 0.081) in the non-chelated system and second order model (R2 = 0.95, SE = 0.010) in the chelated system. The applications generated from this study could be used as tools for improved micronutrient management and also provide baseline data for future work in other semi-arid/arid alkaline soils of the world. Findings are also more applicable to field settings, an improvement over related previous studies.

  19. A study of the efficiency of edible oils degraded in alkaline conditions by Pseudomonas aeruginosa SS-219 and Acinetobacter sp. SS-192 bacteria isolated from Japanese soil.

    PubMed

    Sugimori, Daisuke; Utsue, Tomohiro

    2012-03-01

    High lipid concentration contained in wastewater inhibits the activity of microorganisms in biological wastewater treatment systems such as activated sludge and methane fermentation. To reduce the inhibitory effects, microorganisms capable of efficiently degrading edible oils were screened from various environmental sources. From Japanese soil, we isolated 2 bacteria strains with high degradation abilities at an alkaline pH without consumption of biological oxygen demand (BOD) constituents. Acinetobacter sp. strain SS-192 and Pseudomonas aeruginosa strain SS-219 degraded 77.5 ± 0.6% and 89.5 ± 1.5%, respectively, of 3,000 ppm of mixed oil consisting of salad oil/lard/beef tallow (1/1/1, w/w/w) at 37°C and pH 9.0 in 24 h. Efficient degradation by the two strains occurred at pH 8-9 and 25-40°C. Strain SS-219 degraded lipids even at pH 3. The degradation rate of 3,000 ppm of salad oil, lard, and beef tallow by strain SS-192 was 79.9 ± 2.6%, 63.6 ± 1.9%, and 70.1 ± 1.2%, respectively, during a 24-h cultivation. The degradation rate of 3,000 ppm of salad oil, lard, and beef tallow by strain SS-219 was 82.3 ± 2.1%, 71.9 ± 2.2%, and 71.0 ± 1.1%, respectively, during a 24-h cultivation. After mixed oil degradation by both strains, the BOD value of the cell culture increased from 2,100 ppm to 3,200-4,000 ppm. The fact that neither strain utilizes BOD ingredients will be beneficial to pretreatment of methane fermentation systems such as upflow anaerobic sludge blanket reactors. In addition, the growth of usual heterotrophic microorganisms utilizing soluble BOD can be suppressed under alkaline pH. PMID:22805803

  20. Behavior of iodine-129 in rice paddy fields

    SciTech Connect

    Uchida, Shigeo; Muramatsu, Yasuyuki

    1995-12-31

    Transfer factors of iodine from soil to rice were obtained by laboratory experiments using {sup 125}I tracer. Two typical soil types in Japan, Andosol and Gray lowland soil, were used. The transfer factor (TF) is defined as concentration of the nuclide in a plant organ at harvest divided by concentration of the nuclide in dry soil. The TFs for brown (hulled) rice were 0.006 for Andosol and 0.002 for Gray lowland soil. The TFs for different organs of rice plants decreased in the order of blade > stem > rachis > unhulled rice {much_gt} brown rice. The concentration of iodine in soil solution under flooded conditions varied with time during cultivation. The iodine concentration in rice plants seemed to be influenced by the soil solution. The effect of removal of I-129 from paddy fields by harvesting rice plants was also modeled. Even assuming continuous deposition of I-129 on the field, annual harvesting of the blades and stems of rice plants could effectively reduce the amount of the nuclide in the root zone.

  1. Nutrient runoff from a Korean rice paddy watershed during multiple storm events in the growing season

    NASA Astrophysics Data System (ADS)

    Kim, Jin S.; Oh, Seung Y.; Oh, Kwang Y.

    2006-07-01

    SummaryThe concentrations and loading characteristics of total nitrogen (TN) and total phosphorous (TP) in runoff from a 50.1-ha rice paddy field watershed in South Korea were investigated for eight storm events during the 1998-2001 growing seasons. TN concentrations in total runoff were inversely related to discharge, except in periods with high fertilization rates. In contrast, TP concentrations were strongly proportional to discharge under non-ponded paddy conditions, but not correlated with discharge under most ponded paddy conditions. Stormflow and irrigation return flow were separated from total runoff using the constant-discharge method. The flow-weighted mean TN concentration in stormflow was lower than that in irrigation return flow, mainly because of rainwater dilution, except for periods with a residual fertilizer effect. The flow-weighted mean TP concentration in stormflow, however, was always higher than that in irrigation return flow, likely a result of sediment-associated phosphorus transport. The ratio of mean TP concentration in stormflow to that in irrigation return flow under ponded paddy conditions (1.6) was approximately one-half that under non-ponded conditions (3.1), suggesting that ponding on paddy fields played an important role in reducing soil erosion-related phosphorus export. Relationships between TN loads and stormflow runoff volumes were found except during a storm event in the high fertilization period ( p < 0.05). TP loads were also correlated with stormflow runoff volumes ( p < 0.05), except for storm events under non-ponded and dry antecedent conditions. These results indicate that nitrogen runoff from paddy field watersheds depends on fertilization rates, while phosphorus runoff is controlled by ponding conditions.

  2. Environmental profile of paddy rice cultivation with different straw management.

    PubMed

    Fusi, Alessandra; Bacenetti, Jacopo; González-García, Sara; Vercesi, Annamaria; Bocchi, Stefano; Fiala, Marco

    2014-10-01

    Italy is the most important European country in terms of paddy rice production. North Italian districts such as Vercelli, Pavia, Novara, and Milano are known as some of the world's most advanced rice cultivation sites. In 2013 Italian rice cultivation represented about 50% of all European rice production by area, and paddy fields extended for over 216,000 ha. Cultivation of rice involves different agricultural activities which have environmental impacts mainly due to fossil fuels and agrochemical requirements as well as the methane emission associated with the fermentation of organic material in the flooded rice fields. In order to assess the environmental consequences of rice production in the District of Vercelli, the cultivation practices most frequently carried out were inventoried and evaluated. The general approach of this study was not only to gather the inventory data for rice production and quantify their environmental impacts, but also to identify the key environmental factors where special attention must be paid. Life Cycle Assessment methodology was applied in this study from a cradle-to-farm gate perspective. The environmental profile was analyzed in terms of seven different impact categories: climate change, ozone depletion, human toxicity, terrestrial acidification, freshwater eutrophication, marine eutrophication, and fossil depletion. Regarding straw management, two different scenarios (burial into the soil of the straw versus harvesting) were compared. The analysis showed that the environmental impact was mainly due to field emissions, the fuel consumption needed for the mechanization of field operations, and the drying of the paddy rice. The comparison between the two scenarios highlighted that the collection of the straw improves the environmental performance of rice production except that for freshwater eutrophication. To improve the environmental performance of rice production, solutions to save fossil fuel and reduce the emissions from

  3. [Rules and impact factors of greenhouse gases emission in the saline-alkali paddy fields in different years].

    PubMed

    Tang, Jie; Fang, Tian-Ru; Hou, Ke-Yi; Zhao, Ren-Zhu; Liang, Shuang

    2014-12-01

    With the method of combining field sampling and plot test, we took saline-alkali paddy field of Qianguo county, Jilin province as an investigation object. According to the nature of soil in the area, we monitored CH4 and N2O which released from soil during rice growth period and tested the soil pH and soil organic carbon to analyze the law and reasons of greenhouse gas emission in the paddy fields. The results showed that N2O emission from paddy fields presented three peaks with distinct seasonal patterns. Application of fertilizer provided additional reactive substrate, which affected N2O emission significantly. Under flooding conditions, the main source of N2O is a denitrification process, while after drainage, nitrification was the predominance. CH4 emission showed a single peak at rice tillering stage when rice grew vigorously. That deoxidation condition dominated in the deep water layer in the paddy fields provided suitable conditions for CH4 producing microorganisms, which result in the emergence of CH4 emission peak. The pH doesn't have an obvious influence on CH4 and N2O, while SOC content in soil and pattern of CH4 emission showed a significantly positive correlation. PMID:25826947

  4. Paddy rice ecohydrology pattern and influence on nitrogen dynamics in middle-to-high latitude area

    NASA Astrophysics Data System (ADS)

    Ouyang, Wei; Chen, Siyang; Wang, Xuelei; Shan, Yushu

    2015-10-01

    Paddy rice in middle-to-high latitude areas has a longer growing period with lower temperature. Therefore, it was hypothesized to have a different soil ecohydrology pattern and nitrogen (N) efficiency. Based on daily monitoring of soil moisture and N concentrations in soil water at four depth layers, the characteristics and their ecohydrological interactions, soil environmental indexes and N dynamics were analyzed. The temporal-vertical observations of soil moisture and soil water acquisition rates demonstrated the existence of an impermeable soil layer at 30 cm, which had lower soil organic carbon content. The soil moisture greater in the upper layer had higher soil organic carbon content, which provided the critical conditions for the rice tillage. Lower than the 60 cm depth, the soil moisture increased and had a peak acquisition rate of approximately 0.0075 cm3 s-1. The concentration of NO3--N in the water at the soil subsurface was approximately 2.4 times than that of NH4+-N. The NO3--N had a larger concentration at the deeper layer as a result of downing leaching, but the NH4+-N had a greater concentration in the tops soil layer than the other depths. The soils under the influence of freeze-thawing had the largest TN concentration in surface water at the end of April, which was about three times than that of the peak during the growing period. This study aligned the interactions between the N dynamics with soil microclimatic factors such as temperature, water pH and moisture across the 90 cm profile. The temporal-vertical pattern of soil moisture and the N in soil water provided evidence for the hypothesis that the soil ecohydrology dynamics in this area. These findings were of particular significance to understanding the impacts of paddy rice ecohydrology with N dynamics in middle-to-high latitude areas, which can help to optimize the N availability and water efficiency.

  5. Evidence of the Generation of Isosaccharinic Acids and Their Subsequent Degradation by Local Microbial Consortia within Hyper-Alkaline Contaminated Soils, with Relevance to Intermediate Level Radioactive Waste Disposal

    PubMed Central

    Rout, Simon P.; Charles, Christopher J.; Garratt, Eva J.; Laws, Andrew P.; Gunn, John; Humphreys, Paul N.

    2015-01-01

    The contamination of surface environments with hydroxide rich wastes leads to the formation of high pH (>11.0) soil profiles. One such site is a legacy lime works at Harpur Hill, Derbyshire where soil profile indicated in-situ pH values up to pH 12. Soil and porewater profiles around the site indicated clear evidence of the presence of the α and β stereoisomers of isosaccharinic acid (ISA) resulting from the anoxic, alkaline degradation of cellulosic material. ISAs are of particular interest with regards to the disposal of cellulosic materials contained within the intermediate level waste (ILW) inventory of the United Kingdom, where they may influence radionuclide mobility via complexation events occurring within a geological disposal facility (GDF) concept. The mixing of uncontaminated soils with the alkaline leachate of the site resulted in ISA generation, where the rate of generation in-situ is likely to be dependent upon the prevailing temperature of the soil. Microbial consortia present in the uncontaminated soil were capable of surviving conditions imposed by the alkaline leachate and demonstrated the ability to utilise ISAs as