Science.gov

Sample records for soil water interactions

  1. Molecular interactions of pesticides at the soil-water interface.

    PubMed

    Shirzadi, Azadeh; Simpson, Myrna J; Kumar, Rajeev; Baer, Andrew J; Xu, Yunping; Simpson, André J

    2008-08-01

    High-resolution magic angle spinning (HR-MAS) NMR spectroscopy combined with saturation-transfer double difference (STDD) NMR can be used to analyze the molecular-level interactions of pesticides and whole soils occurring at the soil-water interface. Here 1H HR-MAS STDD NMR has been applied to some common pesticides (trifluralin, acifluorfen, and (4-nitro-3-(trifluoromethyl) phenol) and a pesticide degradation product (1-naphthol). Results indicate that dipolar interactions, H-bonding, hydrophobic associations, and potentially pi-pi interactions are the predominant sorption mechanisms for these molecules at the soil-aqueous interface. It is evident that the physical and chemical characteristics of soil are highly influential in determining the mechanisms of pesticide sorption, as they significantly affect soil conformation. In particular, different binding mechanisms were observed for 1-naphthol in soil swollen using a buffer versus D2O, indicating that the K(oc) alone may not be enough to accurately predict the behavior of a molecule in a real soil environment. Preliminary kinetic-based studies suggest that both the swelling solvent and soil moisture content significantly influence the sequestration of trifluralin. These studies demonstrate that HR-MAS and STDD NMR are powerful and versatile tools which can be applied to expand our knowledge of the mechanistic interactions of agrochemicals at the molecular level. PMID:18754469

  2. Scaling Soil Microbe-Water Interactions from Pores to Ecosystems

    NASA Astrophysics Data System (ADS)

    Manzoni, S.; Katul, G. G.

    2014-12-01

    The spatial scales relevant to soil microbial activity are much finer than scales relevant to whole-ecosystem function and biogeochemical cycling. On the one hand, how to link such different scales and develop scale-aware biogeochemical and ecohydrological models remains a major challenge. On the other hand, resolving these linkages is becoming necessary for testing ecological hypotheses and resolving data-theory inconsistencies. Here, the relation between microbial respiration and soil moisture expressed in water potential is explored. Such relation mediates the water availability effects on ecosystem-level heterotrophic respiration and is of paramount importance for understanding CO2 emissions under increasingly variable rainfall regimes. Respiration has been shown to decline as the soil dries in a remarkably consistent way across climates and soil types (open triangles in Figure). Empirical models based on these respiration-moisture relations are routinely used in Earth System Models to predict moisture effects on ecosystem respiration. It has been hypothesized that this consistency in microbial respiration decline is due to breakage of water film continuity causing in turn solute diffusion limitations in dry conditions. However, this hypothesis appears to be at odds with what is known about soil hydraulic properties. Water film continuity estimated from soil water retention (SWR) measurements at the 'Darcy' scale breaks at far less negative water potential (<-0.1 MPa) levels than where microbial respiration ceases (approximately -15 MPa) as shown in the Figure (violet frequency distribution). Also, this threshold point inferred from SWR shows strong texture dependence, in contrast to the respiration curves. Employing theoretical tools from percolation theory, it is demonstrated that hydrological measurements can be spatially downscaled at a micro-level relevant to microbial activity. Such downscaling resolves the inconsistency between respiration thresholds and

  3. Study on the subgrade deformation under high-speed train loading and water-soil interaction

    NASA Astrophysics Data System (ADS)

    Han, Jian; Zhao, Guo-Tang; Sheng, Xiao-Zhen; Jin, Xue-Song

    2015-11-01

    It is important to study the subgrade characteristics of high-speed railways in consideration of the water-soil coupling dynamic problem, especially when high-speed trains operate in rainy regions. This study develops a nonlinear water-soil interaction dynamic model of slab track coupling with subgrade under high-speed train loading based on vehicle-track coupling dynamics. By using this model, the basic dynamic characteristics, including water-soil interaction and without water induced by the high-speed train loading, are studied. The main factors-the permeability coefficient and the porosity-influencing the subgrade deformation are investigated. The developed model can characterize the soil dynamic behaviour more realistically, especially when considering the influence of water-rich soil.

  4. Study on the subgrade deformation under high-speed train loading and water-soil interaction

    NASA Astrophysics Data System (ADS)

    Han, Jian; Zhao, Guo-Tang; Sheng, Xiao-Zhen; Jin, Xue-Song

    2016-04-01

    It is important to study the subgrade characteristics of high-speed railways in consideration of the water-soil coupling dynamic problem, especially when high-speed trains operate in rainy regions. This study develops a nonlinear water-soil interaction dynamic model of slab track coupling with subgrade under high-speed train loading based on vehicle-track coupling dynamics. By using this model, the basic dynamic characteristics, including water-soil interaction and without water induced by the high-speed train loading, are studied. The main factors-the permeability coefficient and the porosity-influencing the subgrade deformation are investigated. The developed model can characterize the soil dynamic behaviour more realistically, especially when considering the influence of water-rich soil.

  5. Fecal Coliform Interaction with Soil Aggregates: Effect of Water Content and Bovine Manure Application

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Aims: To test the hypothesis that fecal coliform (FC) interaction with soil aggregates is affected by aggregate size, water content and bovine manure application. Methods and Results: Tyler loam soil aggregates were separated into fractions of 3.35-4.75 mm, 4.75-7.93 mm and 7.93-9.5 mm. Air-dry an...

  6. Gravel admix, vegetation, and soil water interactions in protective barriers: Experimental design, construction, and initial conditions

    SciTech Connect

    Waugh, W.J.

    1989-05-01

    The purpose of this study is to measure the interactive effects of gravel admix and greater precipitation on soil water storage and plant abundance. The study is one of many tasks in the Protective Barrier Development Program for the disposal of Hanford defense waste. A factorial field-plot experiment was set up at the site selected as the borrow area for barrier topsoil. Gravel admix, vegetation, and enhanced precipitation treatments were randomly assigned to the plots using a split-split plot design structure. Changes in soil water storage and plant cover were monitored using neutron probe and point intercept methods, respectively. The first-year results suggest that water extraction by plants will offset gravel-caused increases in soil water storage. Near-surface soil water contents were much lower in graveled plots with plants than in nongraveled plots without plants. Large inherent variability in deep soil water storage masked any effects gravel may have had on water content below the root zone. In the future, this source of variation will be removed by differencing monthly data series and testing for changes in soil water storage. Tests of the effects of greater precipitation on soil water storage were inconclusive. A telling test will be possible in the spring of 1988, following the first wet season during which normal precipitation is doubled. 26 refs., 9 figs., 9 tabs.

  7. Interacting vegetative and thermal contributions to water movement in desert soil

    USGS Publications Warehouse

    Garcia, C.A.; Andraski, B.J.; Stonestrom, D.A.; Cooper, C.A.; Simunek, J.; Wheatcraft, S.W.

    2011-01-01

    Thermally driven water-vapor flow can be an important component of total water movement in bare soil and in deep unsaturated zones, but this process is often neglected when considering the effects of soil-plant-atmosphere interactions on shallow water movement. The objectives of this study were to evaluate the coupled and separate effects of vegetative and thermal-gradient contributions to soil water movement in desert environments. The evaluation was done by comparing a series of simulations with and without vegetation and thermal forcing during a 4.7-yr period (May 2001-December 2005). For vegetated soil, evapotranspiration alone reduced root-zone (upper 1 m) moisture to a minimum value (25 mm) each year under both isothermal and nonisothermal conditions. Variations in the leaf area index altered the minimum storage values by up to 10 mm. For unvegetated isothermal and nonisothermal simulations, root-zone water storage nearly doubled during the simulation period and created a persistent driving force for downward liquid fluxes below the root zone (total net flux ~1 mm). Total soil water movement during the study period was dominated by thermally driven vapor fluxes. Thermally driven vapor flow and condensation supplemented moisture supplies to plant roots during the driest times of each year. The results show how nonisothermal flow is coupled with plant water uptake, potentially influencing ecohydrologic relations in desert environments. ?? Soil Science Society of America 5585 Guilford Rd., Madison, WI 53711 USA. All rights reserved.

  8. Drought Impact on Water - Carbon Interaction in Soil: A Stable Isotopic Approach

    NASA Astrophysics Data System (ADS)

    Joseph, J.; Weiler, M.; Gessler, A.

    2014-12-01

    Extreme climatic conditions like drought introduce drastic changes in carbon and water dynamics in the plant - soil continuum, starting from carbon assimilation till carbon allocation in the soil, root water uptake till transpiration via leaves. Our objective was to study the drought impact on the dynamics of Carbon, and water cycles, as well as the interaction between them under extreme climatic conditions in the plant soil continuum. The first phase of the experiment involved 13CO2 pulse labeling of drought exposed and well-water beech microcosms, during which we monitored the 13C allocation to roots, and in the soil by measuring the CO2 concentration, ∂13C, and ∂18O of root derived CO2. We found that drought had a significant impact on, a) carbon assimilation, allocation, and translocation rate in the plant - soil system. The drought stressed plants not only assimilated fewer amounts of CO2, but also translocation of those assimilates belowground was extremely slow, and root respiration was low in comparison the well watered control plants. The second phase involved rewetting of the drought chambers (and the application of similar amounts of water to the controls) using D218O enriched water followed by an additional 13CO2 pulse labeling approach so as to study the effects of drought on the infiltration patterns of a precipitation event as well as the recovery of the carbon relations of previously drought stressed beech saplings.

  9. Interacting vegetative and thermal contributions to water movement in desert soil

    USGS Publications Warehouse

    Garcia, C.A.; Andraski, B.J.; Stonestrom, D.A.; Cooper, C.A.; Šimůnek, J.; Wheatcraft, S.W.

    2011-01-01

    Thermally driven water-vapor flow can be an important component of total water movement in bare soil and in deep unsaturated zones, but this process is often neglected when considering the effects of soil–plant–atmosphere interactions on shallow water movement. The objectives of this study were to evaluate the coupled and separate effects of vegetative and thermal-gradient contributions to soil water movement in desert environments. The evaluation was done by comparing a series of simulations with and without vegetation and thermal forcing during a 4.7-yr period (May 2001–December 2005). For vegetated soil, evapotranspiration alone reduced root-zone (upper 1 m) moisture to a minimum value (25 mm) each year under both isothermal and nonisothermal conditions. Variations in the leaf area index altered the minimum storage values by up to 10 mm. For unvegetated isothermal and nonisothermal simulations, root-zone water storage nearly doubled during the simulation period and created a persistent driving force for downward liquid fluxes below the root zone (total net flux ~1 mm). Total soil water movement during the study period was dominated by thermally driven vapor fluxes. Thermally driven vapor flow and condensation supplemented moisture supplies to plant roots during the driest times of each year. The results show how nonisothermal flow is coupled with plant water uptake, potentially influencing ecohydrologic relations in desert environments.

  10. Interactions between biochar and mycorrhizal fungi in a water-stressed agricultural soil.

    PubMed

    Mickan, Bede S; Abbott, Lynette K; Stefanova, Katia; Solaiman, Zakaria M

    2016-08-01

    Biochar may alleviate plant water stress in association with arbuscular mycorrhizal (AM) fungi but research has not been conclusive. Therefore, a glasshouse experiment was conducted to understand how interactions between AM fungi and plants respond to biochar application under water-stressed conditions. A twin chamber pot system was used to determine whether a woody biochar increased root colonisation by a natural AM fungal population in a pasture soil ('field' chamber) and whether this was associated with increased growth of extraradical AM fungal hyphae detected by plants growing in an adjacent ('bait') chamber containing irradiated soil. The two chambers were separated by a mesh that excluded roots. Subterranean clover was grown with and without water stress and harvested after 35, 49 and 63 days from each chamber. When biochar was applied to the field chamber under water-stressed conditions, shoot mass increased in parallel with mycorrhizal colonisation, extraradical hyphal length and shoot phosphorus concentration. AM fungal colonisation of roots in the bait chamber indicated an increase in extraradical mycorrhizal hyphae in the field chamber. Biochar had little effect on AM fungi or plant growth under well-watered conditions. The biochar-induced increase in mycorrhizal colonisation was associated with increased growth of extraradical AM fungal hyphae in the pasture soil under water-stressed conditions. PMID:27067713

  11. Barrier erosion control test plan: Gravel mulch, vegetation, and soil water interactions

    SciTech Connect

    Waugh, W.J.; Link, S.O. )

    1988-07-01

    Soil erosion could reduce the water storage capacity of barriers that have been proposed for the disposal of near-surface waste at the US Department of Energy's Hanford Site. Gravel mixed into the top soil surface may create a self-healing veneer that greatly retards soil loss. However, gravel admixtures may also enhance infiltration of rainwater, suppress plant growth and water extraction, and lead to the leaching of underlying waste. This report describes plans for two experiments that were designed to test hypotheses concerning the interactive effects of surface gravel admixtures, revegetation, and enhanced precipitation on soil water balance and plant abundance. The first experiment is a factorial field plot set up on the site selected as a soil borrow area for the eventual construction of barriers. The treatments, arranged in a a split-split-plot design structure, include two densities of gravel admix, a mixture of native and introduced grasses, and irrigation to simulate a wetter climate. Changes in soil water storage and plant cover are monitored with neutron moisture probes and point intercept sampling, respectively. The second experiment consists of an array of 80 lysimeters containing several different barrier prototypes. Surface treatments are similar to the field-plot experiment. Drainage is collected from a valve at the base of each lysimeter tube, and evapotranspiration is estimated by subtraction. The lysimeters are also designed to be coupled to a whole-plant gas exchange system that will be used to conduct controlled experiments on evapotranspiration for modeling purposes. 56 refs., 6 figs., 8 tabs.

  12. Soil-water interactions: implications for the sustainability of urban areas

    NASA Astrophysics Data System (ADS)

    Ferreira, António J. D.; Ferreira, Carla S. S.; Walsh, Rory P. D.

    2015-04-01

    Cities have become recently the home for more than half of the world's population. Cities are often seen as ecological systems just a short step away from collapse [Newman 2006]. Being a human construction, cities disrupt the natural cycles and the patterns of temporal and spatial distribution of environmental and ecological processes. Urbanization produces ruptures in biota, water, energy and nutrients connectivity that can lead to an enhanced exposure to disruptive events that hamper the wellbeing and the resilience of urban communities in a global change context. And yet, mankind can't give up of these structures one step away from collapse. In this paper we visit the ongoing research at the Ribeira dos Covões peri-urban catchment, as the basis to discuss several important processes and relations in the water-soil interface: A] the impact of the build environment and consequently the increase of the impervious area on the generation and magnitude of hydrological processes at different scales, the impact on flash flood risk and the mitigation approaches. B] the pollutant sources transport and fade in urban areas, with particular emphasis in the role of vegetation and soils in the transmission of pollutants from the atmosphere to the soil and to the water processes. C] the use and the environmental services of the urban ecosystems (where the relations of water, soil and vegetation have a dominate role) to promote a better risk and resources governance. D] the special issue of urban agriculture, where all the promises of sustainability and threats to wellbeing interact, and where the soil and water relations in urban areas are more significant and have the widest and deepest implications.

  13. Interaction of soil type and carbon dioxide concentration in grassland soil pore water nitrogen concentrations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increasing CO2 concentrations have been shown to limit soil nitrogen availability in terrestrial ecosystems, thereby limiting plant growth. Because changes in nitrogen availability can affect the composition of available nitrogen forms, we are interested in how changes in CO2 concentrations could af...

  14. Climate and Soil Interactions in the Context of Climate, Water, Ecosystems and Food Systems

    NASA Astrophysics Data System (ADS)

    Hatfield, J.

    2015-12-01

    Soil as source of ecosystem services is a major component of climate resilience. Two of the critical ecosystem services derived from soil are water and nutrient cycling. High quality soils improve the capacity to absorb and retain precipitation leading to enhanced water availability to plants which increases climate resilience. The trend towards increasing variability in precipitation requires that the soil be capable of maintaining infiltration rates under extreme precipitation events. Climate resilience will occur when crop productivity is stabilized under more variable climate regimes and dependent upon having adequate soil water supplies to each crop. There is a direct relationship between soil quality and crop productivity and as the soil resource is degraded there is a greater gap between attainable and actual productivity of crop. As the soil is improved there is enhanced nutrient cycling which in turn increases nutrient availability to the crop and food security. Soil becomes the foundation of sustainable ecosystems and enhancing the quality of soil will have a benefit to food and water resources. Improving the soil will benefit humankind through multiple impacts on water, food, and ecosystems.

  15. Soil carbonates and soil water

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The presence of soil carbonates occurring as solidified masses or dispersed particles can alter soil water dynamics from what would be expected based on non-carbonate soil properties. Carbonate minerals in the soil can be derived from high carbonate parent material, additions in the form of carbonat...

  16. Investigation of Interactive Effects on Water Flow and Solute Transport in Sandy Loam Soil Using Time Domain Reflectometry

    PubMed Central

    Merdun, Hasan

    2012-01-01

    Surface-applied chemicals move through the unsaturated zone with complex flow and transport processes due to soil heterogeneity and reach the saturated zone, resulting in groundwater contamination. Such complex processes need to be studied by advanced measurement and modeling techniques to protect soil and water resources from contamination. In this study, the interactive effects of factors like soil structure, initial soil water content (SWC), and application rate on preferential flow and transport were studied in a sandy loam field soil using measurement (by time domain reflectometry (TDR)) and modeling (by MACRO and VS2DTI) techniques. In addition, statistical analyses were performed to compare the means of the measured and modeled SWC and EC, and solute transport parameters (pore water velocity and dispersion coefficient) in 12 treatments. Research results showed that even though the effects of soil structural conditions on water and solute transport were not so clear, the applied solution moved lower depths in the profiles of wet versus dry initial SWC and high application rate versus low application rates. The effects of soil structure and initial SWC on water and solute movement could be differentiated under the interactive conditions, but the effects of the application rates were difficult to differentiate under different soil structural and initial SWC conditions. Modeling results showed that MACRO had somewhat better performance than VS2DTI in the estimation of SWC and EC with space and time, but overall both models had relatively low performances. The means of SWC, EC, and solute transport parameters of the 12 treatments were divided into some groups based on the statistical analyses, indicating different flow and transport characteristics or a certain degree nonuniform or preferential flow and transport in the soil. Conducting field experiments with more interactive factors and applying the models with different approaches may allow better understanding

  17. Impact of interspecific interactions on the soil water uptake depth in a young temperate mixed species plantation

    NASA Astrophysics Data System (ADS)

    Grossiord, Charlotte; Gessler, Arthur; Granier, André; Berger, Sigrid; Bréchet, Claude; Hentschel, Rainer; Hommel, Robert; Scherer-Lorenzen, Michael; Bonal, Damien

    2014-11-01

    Interactions between tree species in forests can be beneficial to ecosystem functions and services related to the carbon and water cycles by improving for example transpiration and productivity. However, little is known on below- and above-ground processes leading to these positive effects. We tested whether stratification in soil water uptake depth occurred between four tree species in a 10-year-old temperate mixed species plantation during a dry summer. We selected dominant and co-dominant trees of European beech, Sessile oak, Douglas fir and Norway spruce in areas with varying species diversity, competition intensity, and where different plant functional types (broadleaf vs. conifer) were present. We applied a deuterium labelling approach that consisted of spraying labelled water to the soil surface to create a strong vertical gradient of the deuterium isotope composition in the soil water. The deuterium isotope composition of both the xylem sap and the soil water was measured before labelling, and then again three days after labelling, to estimate the soil water uptake depth using a simple modelling approach. We also sampled leaves and needles from selected trees to measure their carbon isotope composition (a proxy for water use efficiency) and total nitrogen content. At the end of the summer, we found differences in the soil water uptake depth between plant functional types but not within types: on average, coniferous species extracted water from deeper layers than did broadleaved species. Neither species diversity nor competition intensity had a detectable influence on soil water uptake depth, foliar water use efficiency or foliar nitrogen concentration in the species studied. However, when coexisting with an increasing proportion of conifers, beech extracted water from progressively deeper soil layers. We conclude that complementarity for water uptake could occur in this 10-year-old plantation because of inherent differences among functional groups (conifers

  18. CHEMFLO-2000: INTERACTIVE SOFTWARE FOR PREDICTING AND VISUALIZING TRANSIENT WATER AND CHEMICAL MOVEMENT IN SOILS AND ASSOCIATED UNCERTAINTIES

    EPA Science Inventory

    An interactive Java applet and a stand-alone application program will be developed based on the CHEMFLO model developed in the mid-1980s and published as an EPA report (EPA/600/8-89/076). The model solves Richards Equation for transient water movement in unsaturated soils, and so...

  19. Interaction of carbon dioxide enrichment and soil moisture on photosynthesis, transpiration, and water use efficiency of soybean

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soybean (Glycine max (L.) Merrill) is one of the most important oil and protein sources in the world. Interactive effect of elevated carbon dioxide (CO2) and soil water availability will have the potential impact on crops and future food security of the world under climate change scenario. A rhizotr...

  20. Spatial Heterogeneity of Soil Water after Large Rainfall Events in a Dry Forest: Interacting Canopy, Surface and Soil Effects

    NASA Astrophysics Data System (ADS)

    Magliano, P. N.; Fernández, R. J.; Breshears, D. D.; Paez, R. A.; Jobbagy, E. G.

    2014-12-01

    Ecohydrology of dry forest depends on the proportion of rainfall that enters the soil and it is spatial distribution at the patch scale. While the central role of patch scale redistribution has been widely documented, we know less about its response to rainfall intensity and its interplay with site properties (canopy, surface, soil). Here we explore water capture (infiltrated water depth, 24 hours after a rainfall event) and its determinants at the patch scale in a forest stand of the Dry Chaco (33.47 S, 66.44 W, Argentina). Water capture from 4 large rainfall events (>30 mm) was measured along 3 transects (36 m) in 18 regularly spaced (2 m) microsites, complemented by 2 years of hourly TDR moisture measurements in 3 microsites. Twelve canopy, surface and soil variables were characterized at each microsite. As the intensity of rainfall increased across events (9 to 34 mm/h) the heterogeneity of water capture became larger (coefficient of variation from 29 to 53%). Despite the intense internal redistribution of rainfall, net runoff was virtually nil (<3%) for all events, showing high capture at the stand level. Microsite variables influencing water capture changed with rainfall intensity. Canopy and soil litter cover reduced microsite water capture for the lowest intensity event (r=-0.44 and -0.37, respectively), but favor it for the highest intensity one (r=0.44 and 0.39, respectively). On intermediate intensity events water capture was predominantly explained by microtopography (greater capture in low microsites, p<0.05). Frequent TDR measurements supported these results. Water redistribution responds to rainfall intensity, creating different water capture patterns (contrasting effects of microsite conditions) for each rainfall event, an issue that may strongly influence key ecohydrological process such as E/T partition at the stand level. This study expands our perspective on dry forest water capture by quantifying its response to rainfall intensity.

  1. Oxygen isotope fractionation effects in soil water via interaction with cations (Mg, Ca, K, Na) adsorbed to phyllosilicate clay minerals

    NASA Astrophysics Data System (ADS)

    Oerter, Erik; Finstad, Kari; Schaefer, Justin; Goldsmith, Gregory R.; Dawson, Todd; Amundson, Ronald

    2014-07-01

    In isotope-enabled hydrology, soil and vadose zone sediments have been generally considered to be isotopically inert with respect to the water they host. This is inconsistent with knowledge that clay particles possessing an electronegative surface charge and resulting cation exchange capacity (CEC) interact with a wide range of solutes which, in the absence of clays, have been shown to exhibit δ18O isotope effects that vary in relation to the ionic strength of the solutions. To investigate the isotope effects caused by high CEC clays in mineral-water systems, we created a series of monominerallic-water mixtures at gravimetric water contents ranging from 5% to 32%, consisting of pure deionized water of known isotopic composition with homoionic (Mg, Ca, Na, K) montmorillonite. Similar mixtures were also created with quartz to determine the isotope effect of non-, or very minimally-, charged mineral surfaces. The δ18O value of the water in these monominerallic soil analogs was then measured by isotope ratio mass spectrometry (IRMS) after direct headspace CO2 equilibration. Mg- and Ca-exchanged homoionic montmorillonite depleted measured δ18O values up to 1.55‰ relative to pure water at 5% water content, declining to 0.49‰ depletion at 30% water content. K-montmorillonite enriched measured δ18O values up to 0.86‰ at 5% water content, declining to 0.11‰ enrichment at 30% water. Na-montmorillonite produces no measureable isotope effect. The isotope effects observed in these experiments may be present in natural, high-clay soils and sediments. These findings have relevance to the interpretation of results of direct CO2-water equilibration approaches to the measurement of the δ18O value of soil water. The adsorbed cation isotope effect may bear consideration in studies of pedogenic carbonate, plant-soil water use and soil-atmosphere interaction. Finally, the observed isotope effects may prove useful as molecular scale probes of the nature of mineral-water

  2. Plant Interactions with Changes in Coverage of Biological Soil Crusts and Water Regime in Mu Us Sandland, China

    PubMed Central

    Gao, Shuqin; Pan, Xu; Cui, Qingguo; Hu, Yukun; Ye, Xuehua; Dong, Ming

    2014-01-01

    Plant interactions greatly affect plant community structure. Dryland ecosystems are characterized by low amounts of unpredictable precipitation as well as by often having biological soil crusts (BSCs) on the soil surface. In dryland plant communities, plants interact mostly as they compete for water resources, and the direction and intensity of plant interaction varies as a function of the temporal fluctuation in water availability. Since BSCs influence water redistribution to some extent, a greenhouse experiment was conducted to test the hypothesis that the intensity and direction of plant interactions in a dryland plant community can be modified by BSCs. In the experiment, 14 combinations of four plant species (Artemisia ordosica, Artemisia sphaerocephala, Chloris virgata and Setaria viridis) were subjected to three levels of coverage of BSCs and three levels of water supply. The results show that: 1) BSCs affected plant interaction intensity for the four plant species: a 100% coverage of BSCs significantly reduced the intensity of competition between neighboring plants, while it was highest with a 50% coverage of BSCs in combination with the target species of A. sphaerocephala and C. virgata; 2) effects of the coverage of BSCs on plant interactions were modified by water regime when the target species were C. virgata and S. viridis; 3) plant interactions were species-specific. In conclusion, the percent coverage of BSCs affected plant interactions, and the effects were species-specific and could be modified by water regimes. Further studies should focus on effects of the coverage of BSCs on plant-soil hydrological processes. PMID:24498173

  3. CHEMFLO-2000: INTERACTIVE SOFTWARE FOR SIMULATING WATER AND CHEMICAL MOVEMENT IN UNSATURATED SOILS

    EPA Science Inventory

    The movement of water and chemicals into and through soils has a large impact upon our environment and the entire ecosystem. Understanding these processes is of great importance in managing, utilizing, and protecting our natural resources. This software was written to enhance our...

  4. Space-Time Dynamics of Soil Water and Process Interactions in Semi-Arid Terrain, Colorado, USA

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water is a dominant control of plant growth and hydrologic response in dryland (rainfed) agriculture. In agricultural fields, soil water is typically assumed to move vertically with no differential subsurface lateral flow in semi-arid regions. However, soil water dynamics in the profile can v...

  5. Interactions of soil water content heterogeneity and species diversity patterns in semi-arid steppes on the Loess Plateau of China

    NASA Astrophysics Data System (ADS)

    Wu, Gao-Lin; Zhang, Zhi-Nan; Wang, Dong; Shi, Zhi-Hua; Zhu, Yuan-Jun

    2014-11-01

    Soil water is a major driving force for plant community succession in semi-arid area. Many studies have focused on the relationships of species diversity-productivity, but few studies have paid attentions to the effects of soil water content heterogeneity on the plant species diversity in the semi-arid loess regions. To determine relationship of soil water content heterogeneity and plant community structure properties a semi-arid steppe on the Loess Plateau, we conducted a gradient analysis of soil water content variation and above- and below-ground properties of plant communities. Results showed that community coverage, above- and below-ground biomass were significantly and positively related to the surface soil water contents (0-5 cm). Plant diversity (Shannon index and Richness index) were closely correlated to soil water content at the soil depth of 0-10 cm. But plant height, litter biomass and root/shoot ratio were not related to soil water content. These results showed that there is an positive interaction effects for plant diversity and soil water content in the semi-arid grassland communities. Our observations indicate that change of plant species diversity is also an important community responses to soil water content heterogeneity in the semi-arid grassland ecosystem.

  6. Vegetation and soil water interactions on a tailings sand storage facility in the athabasca oil sands region of Alberta Canada

    NASA Astrophysics Data System (ADS)

    Naeth, M. A.; Chanasyk, D. S.; Burgers, T. D.

    The relationship between vegetation and soil water was studied on the Syncrude South West Sand Storage facility in the Athabasca Oil Sands region of Alberta, Canada. Soil water and relevant soil chemical and physical properties were measured at the soil surface, as well as above and below the reclamation soil and tailings sand interface, in areas of low and high vegetation cover. The interface between the reclamation soil and the tailings sand acted as a capillary barrier. Water content was highest under low vegetation cover but soil water conditions above field capacity were rare and unlikely to have impacted vegetation. Periods of water stress occurred, where volumetric water content was below wilting point; these periods were of short duration and generally typical of ecosystems in the study area. Differences in surface soil water between the two vegetation covers were attributed to evapotranspiration and/or canopy interception. Differences above and below the interface were attributed to variation in canopy cover at the surface and resulting quantities of water available for percolation through the soil profiles. At the interface of the reclamation soil and tailings sand, water movement was restricted. High and low canopy covers responded differently to precipitation events; low vegetation cover areas had greater fluctuations in volumetric water content at all depths. The occurrence of a capillary barrier effect will need to be accounted for in developing reclamation soil profiles.

  7. Exploring C-water-temperature interactions and non-linearities in soils through developments in process-based models

    NASA Astrophysics Data System (ADS)

    Esteban Moyano, Fernando; Vasilyeva, Nadezda; Menichetti, Lorenzo

    2016-04-01

    Soil carbon models developed over the last couple of decades are limited in their capacity to accurately predict the magnitudes and temporal variations in observed carbon fluxes and stocks. New process-based models are now emerging that attempt to address the shortcomings of their more simple, empirical counterparts. While a spectrum of ideas and hypothetical mechanisms are finding their way into new models, the addition of only a few processes known to significantly affect soil carbon (e.g. enzymatic decomposition, adsorption, Michaelis-Menten kinetics) has shown the potential to resolve a number of previous model-data discrepancies (e.g. priming, Birch effects). Through model-data validation, such models are a means of testing hypothetical mechanisms. In addition, they can lead to new insights into what soil carbon pools are and how they respond to external drivers. In this study we develop a model of soil carbon dynamics based on enzymatic decomposition and other key features of process based models, i.e. simulation of carbon in particulate, soluble and adsorbed states, as well as enzyme and microbial components. Here we focus on understanding how moisture affects C decomposition at different levels, both directly (e.g. by limiting diffusion) or through interactions with other components. As the medium where most reactions and transport take place, water is central en every aspect of soil C dynamics. We compare results from a number of alternative models with experimental data in order to test different processes and parameterizations. Among other observations, we try to understand: 1. typical moisture response curves and associated temporal changes, 2. moisture-temperature interactions, and 3. diffusion effects under changing C concentrations. While the model aims at being a process based approach and at simulating fluxes at short time scales, it remains a simplified representation using the same inputs as classical soil C models, and is thus potentially

  8. Interaction of Actinide Species with Microorganisms & Microbial Chelators: Cellular Uptake, Toxicity, & Implications for Bioremediation of Soil & Ground Water.

    SciTech Connect

    Hakim Boukhalfa Mary, P. Neu Alvin Crumbliss

    2006-03-28

    Microorganisms influence the natural cycle of major elements, including C, N, P, S, and transition metals such as Mn and Fe. Bacterial processes can also influence the behavior of actinides in soil and ground water. While radionuclides have no known biological utility, they have the potential to interact with microorganisms and to interfere with processes involving other elements such as Fe and Mn. These interactions can transform radionuclides and affect their fate and transport. Organic acids, extruded by-products of cell metabolism, can solubilize radionuclides and facilitate their transport. The soluble complexes formed can be taken up by the cells and incorporated into biofilm structures. We have examined the interactions of Pu species with bacterial metabolites, studied Pu uptake by microorganisms and examined the toxicity of Pu and other toxic metals to environmentally relevant bacteria. We have also studied the speciation of Pu(IV) in the presence of natural and synthetic chelators.

  9. Soil Erosion by Water

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil erosion by water, the wearing away of the earth's surface by the forces of water and gravity, consists of rock or soil particle dislodgement, entrainment, transport, and deposition. This sequence of events occurs over a wide range of temporal and spatial scales, from raindrop splash moving par...

  10. MANE: A MULTIPHASE, AQUEOUS, NON-STEADY STATE EQUILIBRIUM MODEL FOR SIMULATING SOIL-WATER INTERACTIONS

    EPA Science Inventory

    A variety of chemical equilibrium models have been developed to help assess environmental chemistry problems, but few were specifically developed as research and teaching tools for use in conjunction with soil chemistry experiments. MANE model was developed to calculate equilibri...

  11. Responses of soil water percolation to dynamic interactions among rainfall, antecedent moisture and season in a forest site

    NASA Astrophysics Data System (ADS)

    Lai, Xiaoming; Liao, Kaihua; Feng, Huihui; Zhu, Qing

    2016-09-01

    Knowledge of soil water percolation below the rooting zone and its responses to the dynamic interactions of different factors are important for the control of non-point source pollution. Based on 3600 scenarios in Hydrus-1D simulation, this study revealed the integrated effects of rainfall characteristics (rainfall amount, maximum rainfall intensity or MRI, time distribution characteristics of rainfall or TDC), antecedent moisture and the season on deep percolation (DP) at a forest site in Taihu Lake Basin, China. Results showed that Hydrus-1D model can well simulate the soil water dynamics at this site. Antecedent moisture had the greatest relative contribution to DP (85.7%), followed by rainfall amount (10.9%) and MRI (3.4%). As the antecedent moisture increased, the relative contribution of the season on DP increased from 0.0% to 16.4%. In comparison, that of MRI decreased from 58.7% to 38.5% and that of rainfall amount followed a bell shape pattern (greatest when the antecedent moisture was 0.26 m3 m-3). The relative contribution of antecedent moisture to DP in summer was the greatest (87.8%), while that of the rainfall was the least. The TDC influenced DP by affecting the responses of DP to other factors. When the rainfall amount was ⩾80 mm and the antecedent moisture content was ⩾0.34 m3 m-3, effect of TDC on DP could be observed. The DP of TDC_B (rainfall intensity linearly increased with time) was the lowest, while that of TDC_E (rainfall intensity kept constant with time) was the greatest. Findings of this study have practical significance for investigating the water and pollutant transport in vadose zone.

  12. Oxytetracycline interactions at the soil-water interface: effects of environmental surfaces on natural transformation and growth inhibition of Azotobacter vinelandii.

    PubMed

    Goetsch, Heather E; Mylon, Steven E; Butler, Shane; Zilles, Julie L; Nguyen, Thanh H

    2012-10-01

    The mechanism of oxytetracycline (OTC) adsorption to a silty clay loam soil was investigated using sorption isotherm experiments, Fourier transform infrared spectroscopy (FTIR), and X-ray diffraction spectroscopy (XRD). Sorption data fit well to a cation-exchange capacity sorption model. Spectroscopic data indicate that the interactions between oxytetracycline and silty clay loam soil were primarily through electrostatic interactions between the protonated dimethylamino group of OTC and the negatively charged moieties on the surface of the soil. Based on XRD results, OTC adsorption appeared to inhibit the ethylene glycol solvation of the expandable clay minerals, suggesting that OTC had diffused into the clay interlayer space. The presence of adsorbed OTC did not significantly affect the transformation frequency of the soil bacterium Azotobacter vinelandii with plasmid DNA (soil alone 3 × 10(6)  ± 4 × 10(6) and soil with adsorbed OTC 4 × 10(6)  ± 0.5 × 10(6) ). Growth was inhibited by adsorbed OTC, although a greater mass of adsorbed OTC was required to achieve the same degree of inhibition as the system of dissolved OTC alone. These results suggest that the interactions of tetracyclines at the soil-water interface will affect the growth of sensitive microorganisms in soil microbial communities. PMID:22821843

  13. Groundwater-soil moisture-climate interactions: lessons from idealized model experiments with forced water table depth

    NASA Astrophysics Data System (ADS)

    Ducharne, Agnès; Lo, Min-Hui; Decharme, Bertrand; Wang, Fuxing; Cheruy, Frédérique; Ghattas, Josefine; Chien, Rong-You; lan, Chia-Wei; Colin, Jeanne; Tyteca, Sophie

    2016-04-01

    Groundwater (GW) constitutes by far the largest volume of liquid freshwater on Earth. The most active part is soil moisture (SM), recognized as a key variable of land/atmosphere interactions, especially in so-called transition zones, where/when SM varies between wet and dry values. But GW can also be stored in deeper reservoirs than soils, in particular unconfined aquifer systems, in which the saturated part is called the water table (WT). The latter is characterized by slow and mostly horizontal water flows towards the river network, with well-known buffering effects on streamflow variability. Where/when the WT is shallow enough, it can also sustain SM by means of capillary rise, thus increase evapotranspiration (ET), with potential impact on the climate system (including temperatures and precipitation). The large residence time of GW may also increase the Earth system's memory, with consequences on the persistence of extreme events, hydro-climatic predictability, and anthropogenic climate change, particularly the magnitude of regional warming. Here, our main goal is to explore the potential impacts of the water table depth (WTD) on historical climate through idealized model analyses. To this end, we force three state-of-the art land surface models (LSMs), namely CLM, ORCHIDEE, and SURFEX, with prescribed WTDs ranging from 0.5 to 10 m. The LSMs are run either off-line or coupled to their parent climate model, following LMIP/AMIP-like protocols for intercomparability. Within this framework, we want to assess the sensitivity of ET and the simulated climate to the WTD in a systematic way. In particular, we will identify and compare the patterns of the critical WTD, defined as the deepest one to achieve a significant change in ET. To this end, we estimate derivatives of ET with respect to WTD, which tell how the sensitivity of ET to a unit change in WTD evolves with WTD. In each grid-point, these derivatives can be used to define the critical WTD, given a threshold ET

  14. Triazine Soil Interactions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The fate of triazine herbicides in soils is controlled by three basic processes: transformation, retention, and transport. Sorption of triazines on surfaces of soil particles is the primary means by which triazines are retained in soils. Soils are very complex mixtures of living organisms, various t...

  15. Interactions between root water uptake, groundwater levels, and soil moisture dynamics in Tuolumne Meadows, Yosemite National Park, CA

    NASA Astrophysics Data System (ADS)

    Lowry, C.; Loheide, S. P.

    2009-12-01

    In high elevation meadow environments within the Sierra Nevada Mountains soil moisture is controlled by the position of the water table and the partitioning of evapotranspiration through root water uptake and evaporation at the land surface. Because of the relative lack of precipitation over the growing season plant communities rely on stored soil moisture and shallow groundwater during the dry summer months. Field result, from Tuolumne Meadows show both temporally and spatially dynamic soil moisture patterning caused by the timing of spring snowmelt and subsequent drying of the meadow. Through the use of numerical modeling we are able to examine the temporal and spatial distribution of soil moisture and the potential impact on water use by plant communities. Results highlight the importance of both the position of the water table in the early growing season and sediment layering within the meadow on plant water up take. These results have implications for current meadow restorations projects and stress the importance of designing projects that focus on soil moisture dynamics in order to supply sufficient water for native plant communities.

  16. Soil cultivation in vineyards alters interactions between soil biota and soil physical and hydrological properties

    NASA Astrophysics Data System (ADS)

    Zaller, Johann G.; Buchholz, Jacob; Querner, Pascal; Winter, Silvia; Kratschmer, Sophie; Pachinger, Bärbel; Strauss, Peter; Bauer, Thomas; Stiper, Katrin; Potthoff, Martin; Guernion, Muriel; Scimia, Jennifer; Cluzeau, Daniel

    2016-04-01

    Several ecosystem services provided by viticultural landscapes result from interactions between soil organisms and soil parameters. However, to what extent different soil cultivation intensities in vineyards compromise soil organisms and their interactions between soil physical and hydrological properties is not well understood. In this study we examined (i) to what extent different soil management intensities affect the activity and diversity of soil biota (earthworms, Collembola, litter decomposition), and (ii) how soil physical and hydrological properties influence these interactions, or vice versa. Investigating 16 vineyards in Austria, earthworms were assessed by hand sorting, Collembola via pitfall trapping and soil coring, litter decomposition by using the tea bag method. Additionally, soil physical (water infiltration, aggregate stability, porosity, bulk density, soil texture) and chemical (pH, soil carbon content, cation exchange capacity, potassium, phosphorus) parameters were assessed. Results showed complex ecological interactions between soil biota and various soil characteristics altered by management intensity. These investigations are part of the transdisciplinary BiodivERsA project VineDivers and will ultimately lead into management recommendations for various stakeholders.

  17. Interaction between soils and gas pipelines

    NASA Astrophysics Data System (ADS)

    Karpachevskii, L. O.; Goroshevskii, A. V.; Zubkova, T. A.

    2011-03-01

    The interaction between pipelines and soils manifests itself in the soil disturbance in the course of the pipe installation, in the transformation of the water and temperature regimes in the trenches, and in the appearance of corrosion and cracks on the pipe walls. The more contrasting the soil water regime in the pipe-adjacent sections of the trench, the greater the amount of the pipe damage. The damage of the pipe insulation activates the pipe corrosion. The emission of gases (H2S, CH4, CO2, CO, and H2) and the activity of sulfate-reducing bacteria are the main causes of the pipes' destruction. The humus content and the redox potential decrease, and the soil density and concentrations of ferrous compounds increase in the soils of the trench zone. Accidents along pipelines occur most often in the area of serozems and chestnut soils, and this is related to the salinization in the lower soil horizons and to the contrasting soil water regime near the pipe. The number of accidents along the pipelines installed into soddy-podzolic soils is lower.

  18. Hydraulic Redistribution of Soil Water in a Drained Loblolly Pine Plantation: Quantifying Patterns and Controls over Soil-to-Root and Canopy-to-Atmosphere Interactions

    NASA Astrophysics Data System (ADS)

    Domec, J.; Noormets, A.; King, J. S.; Sun, G.; McNulty, S. G.; Gavazzi, M. J.; Strickland, S.; Boggs, J. L.

    2007-12-01

    The conversion of wetlands to intensively managed forest lands in eastern North Carolina is widespread and the consequences on water and carbon balances are not well studied. Quantification of evapotranspiration (ET), tree transpiration and their biophysical regulation are needed for assessing forest water management options. We characterized vertical variation in the diurnal and seasonal soil volumetric water content at 10 cm intervals to evaluate changes in water availability for root uptake and monitored eddy covariance ET and tree transpiration (sap flux) in a drained Loblolly pine (Pinus taeda L.) plantation. We also quantified the magnitude of hydraulic redistribution (HR), the passive movement of soil water from deep to shallow roots, to identify factors affecting the seasonal dynamics of root water uptake, root and plant water potentials and stomatal conductance. Soil water content varied with soil depth and total water use from the upper 1m peaked between 4 and 6.5 mm/day during the growing season and was strongly correlated and similar to ET (ET represented 90-95% of total water depletion). After periods of more than 10 days without rain, water extraction shifted to the deeper layers, and recharge from HR approached 0.5 mm/day in the upper 60 cm. However, the upper 30cm accounted for 40% of total water depletion from the upper 1m at peak water uptake (>4 mm/day), and increased to 65% during days of low water uptake (<2 mm/day), illustrating the contribution of deeper roots to water uptake during days of high evaporative demand. This result was supported by the fact that deep roots (from 30-50cm) accounted for 65% of the total water redistributed. Because of stomatal regulation to prevent water potentials from reaching critical values that would cause significant loss of tree hydraulic conductivity, maximum tree transpiration during high evaporative demand remained constant at around 3 mm/day. Tree transpiration represented on average 60% of ET. However

  19. Field study of gravel admix, vegetation, and soil water interactions: Protective Barrier Program Status Reprt - FY 1989

    SciTech Connect

    Waugh, W.J.; Thiede, M.E.; Kemp, C.J.; Cadwell, L.L. Link, S.O.

    1990-08-01

    Pacific Northwest Laboratory (PNL) and Westinghouse Hanford Company (Westinghouse Hanford) are collaborating on a field study of the effects of gravel admixtures on plant growth and soil water storage in protective barriers. Protective barriers are engineered earthern covers designed to prevent water, plants, and animals from contacting buried waste and transporting contaminants to groundwater or the land surface. Some of the proposed designs include gravel admixtures or gravel mulches on the barrier surface to control soil loss by wind and runoff. The purpose of this study is to measure, in a field setting, the influence of surface gravel additions on soil water storage and plant cover. The study plots are located northwest of the Yakima Gate in the McGee Ranch old field. Here we report the status of work completed in FY 1989 on the creation of a data management system, a test of water application uniformity, field calibration of neutron moisture gages, and an analysis of the response of plants to various combinations of gravel admixtures and increased rainfall. 23 refs., 11 figs., 6 tabs.

  20. Sources, interactions, and ecological impacts of organic contaminants in water, soil, and sediment: an introduction to the special series.

    PubMed

    Pignatello, Joseph J; Katz, Brian G; Li, Hui

    2010-01-01

    Agricultural and urban activities result in the release of a large number of organic compounds that are suspected of impacting human health and ecosystems: herbicides, insecticides, human and veterinary pharmaceuticals, natural and synthetic hormones, personal care products, surfactants, plasticizers, fire retardants, and others. Sorbed reservoirs of these compounds in soil represent a potentially chronic source of water contamination. This article is an introduction to a series of technical papers stemming from a symposium at the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America 2008 Annual Meeting, which was held jointly with The Geological Society of America, The Gulf Coast Association of Geological Scientists, and the Houston Geological Society, under one of the Joint Meeting's overarching themes: Emerging Trace Contaminants in Surface and Ground Water Generated from Waste Water and Solid Waste Application. The symposium emphasized the role of soils as sources, sinks, and reaction catalysts for these contaminants and the occurrence and fate of these contaminants in surface and underground water supplies. Topics covered included novel advances in analytical techniques, transport of infectious agents, occurrence and fate of veterinary pharmaceuticals, characterization of sorption mechanism, biotic and abiotic transformation reactions, the role of soil components, occurrence and fate in wastewater treatment systems, transport of engineered nanoparticles, groundwater contamination resulting from urban runoff, and issues in water reuse. Overviews of the reports, trends, gaps in our knowledge, and topics for further research are presented in this special series of papers. The technical papers in this special series reflect current gains in knowledge and simultaneously underscore how poorly we are able to predict the fate and, hence, the associated risk to ecological and human receptors of these contaminants. PMID

  1. Crop Residue and Soil Water

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crop yield is greatly influenced by the amount of water that moves from the soil, through the plant, and out into the atmosphere. Winter wheat yield responds linearly to available soil water content at planting (bu/a = 5.56 + 5.34*inches). Therefore, storing precipitation in the soil during non-crop...

  2. Application of time-lapse ERT to Characterize Soil-Water-Disease Interactions of Citrus Orchard - Case Study

    NASA Astrophysics Data System (ADS)

    Peddinti, S. R.; Kbvn, D. P.; Ranjan, S.; Suradhaniwar, S.; J, P. A.; R M, G.

    2015-12-01

    Vidarbha region in Maharashtra, India (home for mandarin Orange) experience severe climatic uncertainties resulting in crop failure. Phytopthora are the soil-borne fungal species that accumulate in the presence of moisture, and attack the root / trunk system of Orange trees at any stage. A scientific understanding of soil-moisture-disease relations within the active root zone under different climatic, irrigation, and crop cycle conditions can help in practicing management activities for improved crop yield. In this study, we developed a protocol for performing 3-D time-lapse electrical resistivity tomography (ERT) at micro scale resolution to monitor the changes in resistivity distribution within the root zone of Orange trees. A total of 40 electrodes, forming a grid of 3.5 m x 2 m around each Orange tree were used in ERT survey with gradient and Wenner configurations. A laboratory test on un-disturbed soil samples of the region was performed to plot the variation of electrical conductivity with saturation. Curve fitting techniques were applied to get the modified Archie's model parameters. The calibrated model was further applied to generate the 3-D soil moisture profiles of the study area. The point estimates of soil moisture were validated using TDR probe measurements at 3 different depths (10, 20, and 40 cm) near to the root zone. In order to understand the effect of soil-water relations on plant-disease relations, we performed ERT analysis at two locations, one at healthy and other at Phytopthora affected Orange tree during the crop cycle, under dry and irrigated conditions. The degree to which an Orange tree is affected by Phytopthora under each condition is evaluated using 'grading scale' approach following visual inspection of the canopy features. Spatial-temporal distribution of moisture profiles is co-related with grading scales to comment on the effect of climatic and irrigation scenarios on the degree and intensity of crop disease caused by Phytopthora.

  3. Quantitative simulation tools to analyze up- and downstream interactions of soil and water conservation measures: supporting policy making in the Green Water Credits program of Kenya.

    PubMed

    Hunink, J E; Droogers, P; Kauffman, S; Mwaniki, B M; Bouma, J

    2012-11-30

    Upstream soil and water conservation measures in catchments can have positive impact both upstream in terms of less erosion and higher crop yields, but also downstream by less sediment flow into reservoirs and increased groundwater recharge. Green Water Credits (GWC) schemes are being developed to encourage upstream farmers to invest in soil and water conservation practices which will positively effect upstream and downstream water availability. Quantitative information on water and sediment fluxes is crucial as a basis for such financial schemes. A pilot design project in the large and strategically important Upper-Tana Basin in Kenya has the objective to develop a methodological framework for this purpose. The essence of the methodology is the integration and use of a collection of public domain tools and datasets: the so-called Green water and Blue water Assessment Toolkit (GBAT). This toolkit was applied in order to study different options to implement GWC in agricultural rainfed land for the pilot study. Impact of vegetative contour strips, mulching, and tied ridges were determined for: (i) three upstream key indicators: soil loss, crop transpiration and soil evaporation, and (ii) two downstream indicators: sediment inflow in reservoirs and groundwater recharge. All effects were compared with a baseline scenario of average conditions. Thus, not only actual land management was considered but also potential benefits of changed land use practices. Results of the simulations indicate that especially applying contour strips or tied ridges significantly reduces soil losses and increases groundwater recharge in the catchment. The model was used to build spatial expressions of the proposed management practices in order to assess their effectiveness. The developed procedure allows exploring the effects of soil conservation measures in a catchment to support the implementation of GWC. PMID:22922092

  4. Soil and Human Interactions in Maya Wetlands

    NASA Astrophysics Data System (ADS)

    Beach, Timothy; Luzzadder-Beach, Sheryl

    2013-04-01

    Since the early 1990s, we have studied Maya interaction with soils in Mexico, Belize, Guatemala, and elsewhere. We studied upland and lowland soils, but here we focus on seasonal or 'Bajo' wetlands and perennial wetlands for different reasons. Around the bajos, the ancient Maya focused on intensive agriculture and habitation despite the difficulties their Vertisol soils posed. For the perennial wetlands, small populations spread diffusely through Mollisol and Histisol landscapes with large scale, intensive agro-ecosystems. These wetlands also represent important repositories for both environmental change and how humans responded in situ to environmental changes. Work analyzing bajo soils has recorded significant diversity but the soil and sediment record shows two main eras of soil instability: the Pleistocene-Holocene transition as rainfall fluctuated and increased and tropical forest pulsed through the region, and the Maya Preclassic to Classic 3000 to 1000 BP as deforestation, land use intensity, and drying waxed and waned. The ancient Maya adapted their bajo soil ecosystems successfully through agro-engineering but they also withdrew in many important places in the Late Preclassic about 2000 BP and Terminal Classic about 1200 BP. We continue to study and debate the importance of perennial wetland agro-ecosystems, but it is now clear that Maya interaction with these soil landscapes was significant and multifaceted. Based on soil excavation and coring with a broad toolkit of soil stratigraphy, chemistry, and paleoecology from 2001 to 2013, our results show the ancient Maya interacted with their wetland soils to maintain cropland for maize, tree crops, arrow root, and cassava against relative sea level rise, increased flooding, and aggradation by gypsum precipitation and sedimentation. We have studied these interactions across an area of 2000 km2 in Northern Belize to understand how Maya response varied and how these soil environments varied over time and distance

  5. Spatial patterns of interaction among climate variability and change, soil water deficit and transpiration in small mountain catchments of Southern Sierra Critical Zone Observatory

    NASA Astrophysics Data System (ADS)

    Son, K.; Tague, C.

    2011-12-01

    In snow-dominated mountain systems, a warming climate alters soil water deficit through changing the timing and magnitude of moisture inputs as precipitation and snowmelt and through changes in the timing and magnitude of evapotranspiration losses. The net effect of climate warming on soil water deficit and associated ecosystem processes ultimately depends on the interaction between changes in inputs and outputs and on vegetation, micro-climate and soil properties that control the sensitivity of soil water to changes in input/output drivers. In mountain environments, steep spatial gradients result in substantial variation in atmospheric forcing and vegetation and soil properties over relatively short spatial scales, which necessitate providing finer-scale assessment of climate change impact. Measurements of soil moisture and forest responses to climate are often made at plot scales but are limited in spatial coverage. Coupled eco-hydrologic models, applied at relatively fine (m) scales provide a method of extrapolating findings from local measurements and exploring hillslope and watershed scale impacts of climate warming on moisture deficit. In this study, we use RHESSys (Regional hydro-ecologic simulation system) combined with spatially intensive monitoring of coupled ecohydrologic variables at the Southern Sierra Critical Zone Observatory (SSCZO), located in the Sierra National Forest, California. We initially use the model to identify clusters of distinctive water deficit behavior as summarized by indices of summertime soil moisture and transpiration recessions. The resulting clusters demonstrate that both elevational differences in energy availability and topographic controls on drainage are 1st order controls on spatial patterns of summertime moisture deficit and tree transpiration. We then use these initial model clusters to guide soil moisture and sapflux data collection. The collected data are used to characterize soil moisture deficit and transpiration for

  6. Container Soil-Water Reactions.

    ERIC Educational Resources Information Center

    Spomer, L. Art; Hershey, David R.

    1990-01-01

    Presented is an activity that illustrates the relationship between the soil found in containers and soil in the ground including the amount of air and water found in each. Sponges are used to represent soil. Materials, procedures, and probable results are described. (KR)

  7. A new model for humic materials and their interactions with hydrophobic organic chemicals in soil-water or sediment-water systems

    USGS Publications Warehouse

    Wershaw, R. L.

    1986-01-01

    A generalized model of humic materials in soils and sediments, which is consistent with their observed properties, is presented. This model provides a means of understanding the interaction of hydrophobic pollutants with humic materials. In this model, it is proposed that the humic materials in soils and sediments consist of a number of different oligomers and simple compounds which result from the partial degradation of plant remains. These degradation products are stabilized by incorporation into humic aggregates bound together by weak bonding mechanisms, such as hydrogen bonding, pi bonding, and hydrophobic interactions. The resulting structures are similar to micelles or membranes, in which the interiors of the structures are hydrophobic and the exteriors are hydrophilic. Hydrophobic compounds will partition into the hydrophobic interiors of the humic micelles or "membrane-like" structures. ?? 1986.

  8. Parameter selection and testing the soil water model SOIL

    NASA Astrophysics Data System (ADS)

    McGechan, M. B.; Graham, R.; Vinten, A. J. A.; Douglas, J. T.; Hooda, P. S.

    1997-08-01

    The soil water and heat simulation model SOIL was tested for its suitability to study the processes of transport of water in soil. Required parameters, particularly soil hydraulic parameters, were determined by field and laboratory tests for some common soil types and for soils subjected to contrasting treatments of long-term grassland and tilled land under cereal crops. Outputs from simulations were shown to be in reasonable agreement with independently measured field drain outflows and soil water content histories.

  9. Investigation of soil-atmosphere interaction in pyroclastic soils

    NASA Astrophysics Data System (ADS)

    Rianna, Guido; Pagano, Luca; Urciuoli, Gianfranco

    2014-03-01

    This paper investigates the interaction between soil and atmosphere in pyroclastic soils with a view to understanding whether and to what extent the prediction of the hydraulic (and mechanical) behaviour of geotechnical problems (cuts, slope stabilities, embankments, foundation, retaining structures) regulated by rainfall-induced fluctuations of matric suction is influenced by evaporation phenomena. Evaporation fluxes are quantified and compared with other fluxes (precipitation, run-off, deep drainage) affecting soil water content and matric suction. This work is based on the data collected through a physical model over 2 years of experimental tests. The model consisted of a 1 m3 tank, filled in this case with pyroclastic soil and exposed to natural weather elements. The system was extensively monitored to record atmospheric and soil variables. The results provided by the experiments highlight the importance of the top-soil state in determining the intensities of infiltrating rainfall and actual evaporation. The results also bring to light the significance of evaporation which, during the dry season, largely prevails over infiltration, raising suction to very high values. Also during the wet season, evaporation gives rise to a non-negligible flux with respect to the infiltrated precipitation. The reliability of two pre-existing empirical models to estimate evaporation flux is also investigated and appraised within this paper.

  10. Profiling soil water content sensor

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A waveguide-on-access-tube (WOAT) sensor system based on time domain reflectometry (TDR) principles was developed to sense soil water content and bulk electrical conductivity in 20-cm (8 inch) deep layers from the soil surface to depths of 3 m (10 ft) (patent No. 13/404,491 pending). A Cooperative R...

  11. Soil and Water: Some Teaching Suggestions.

    ERIC Educational Resources Information Center

    Fischer, Richard B.

    1987-01-01

    Outlines six soil and water investigations that students can pursue outdoors, in nature centers, or in classrooms: soil characteristics; relationship between soil ph and plant life; what aggregates tell us; differences in soil structure; differences in rate of water absorption by soil; and soil exploration with a Berlesi funnel. (NEC)

  12. Interactive effects of soil water deficit and air vapour pressure deficit on mesophyll conductance to CO2 in Vitis vinifera and Olea europaea.

    PubMed

    Perez-Martin, A; Flexas, J; Ribas-Carbó, M; Bota, J; Tomás, M; Infante, J M; Diaz-Espejo, A

    2009-01-01

    The present work aims to study the interactive effect of drought stress and high vapour pressure deficit (VPD) on leaf gas exchange, and especially on mesophyll conductance to CO(2) (g(m)), in two woody species of great agronomical importance in the Mediterranean basin: Vitis vinifera L. cv. Tempranillo and Olea europaea L. cv. Manzanilla. Plants were grown in specially designed outdoor chambers with ambient and below ambient VPD, under both well-irrigated and drought conditions. g(m) was estimated by the variable J method from simultaneous measurements of gas exchange and fluorescence. In both species, the response to soil water deficit was larger in g(s) than in g(m), and more important than the response to VPD. Olea europaea was apparently more sensitive to VPD, so that plants growing in more humid chambers showed higher g(s) and g(m). In V. vinifera, in contrast, soil water deficit dominated the response of g(s) and g(m). Consequently, changes in g(m)/g(s) were more related to VPD in O. europaea and to soil water deficit in V. vinifera. Most of the limitations of photosynthesis were diffusional and especially due to stomatal closure. No biochemical limitation was detected. The results showed that structural parameters played an important role in determining g(m) during the acclimation process. Although the relationship between leaf mass per unit area (M(A)) with g(m) was scattered, it imposed a limitation to the maximum g(m) achievable, with higher values of M(A) in O. europaea at lower g(m) values. M(A) decreased under water stress in O. europaea but it increased in V. vinifera. This resulted in a negative relationship between M(A) and the CO(2) draw-down between substomatal cavities and chloroplasts in O. europaea, while being positive in V. vinifera. PMID:19457982

  13. Elementary soil and water engineering

    SciTech Connect

    Schwab, G.O.; Frevert, R.K.

    1985-01-01

    Between 1967-1975 the Northwest lost 325 acres per day of prime farmland, the Midwest (our nation's bread basket) 493 acres, and the Southwest 548 acres per day. We lost one million acres like this each year, three million for all rural land. Six problems affect our diminishing soil and water resources: erosion, drainage, irrigation, conservation of soil moisture, efficiency of water storage, floods. The first five problems are discussed in this book.

  14. Estimating soil water retention using soil component additivity model

    NASA Astrophysics Data System (ADS)

    Zeiliger, A.; Ermolaeva, O.; Semenov, V.

    2009-04-01

    Soil water retention is a major soil hydraulic property that governs soil functioning in ecosystems and greatly affects soil management. Data on soil water retention are used in research and applications in hydrology, agronomy, meteorology, ecology, environmental protection, and many other soil-related fields. Soil organic matter content and composition affect both soil structure and adsorption properties; therefore water retention may be affected by changes in soil organic matter that occur because of both climate change and modifications of management practices. Thus, effects of organic matter on soil water retention should be understood and quantified. Measurement of soil water retention is relatively time-consuming, and become impractical when soil hydrologic estimates are needed for large areas. One approach to soil water retention estimation from readily available data is based on the hypothesis that soil water retention may be estimated as an additive function obtained by summing up water retention of pore subspaces associated with soil textural and/or structural components and organic matter. The additivity model and was tested with 550 soil samples from the international database UNSODA and 2667 soil samples from the European database HYPRES containing all textural soil classes after USDA soil texture classification. The root mean square errors (RMSEs) of the volumetric water content estimates for UNSODA vary from 0.021 m3m-3 for coarse sandy loam to 0.075 m3m-3 for sandy clay. Obtained RMSEs are at the lower end of the RMSE range for regression-based water retention estimates found in literature. Including retention estimates of organic matter significantly improved RMSEs. The attained accuracy warrants testing the 'additivity' model with additional soil data and improving this model to accommodate various types of soil structure. Keywords: soil water retention, soil components, additive model, soil texture, organic matter.

  15. Interactive response of photosynthetic characteristics in Haloxylon ammodendron and Hedysarum scoparium exposed to soil water and air vapor pressure deficits.

    PubMed

    Gong, Chunmei; Wang, Jiajia; Hu, Congxia; Wang, Junhui; Ning, Pengbo; Bai, Juan

    2015-08-01

    C4 plants possess better drought tolerance than C3 plants. However, Hedysarum scoparium, a C3 species, is dominant and widely distributed in the desert areas of northwestern China due to its strong drought tolerance. This study compared it with Haloxylon ammodendron, a C4 species, regarding the interactive effects of drought stress and different leaf-air vapor pressure deficits. Variables of interest included gas exchange, the activity levels of key C4 photosynthetic enzymes, and cellular anatomy. In both species, gas exchange parameters were more sensitive to high vapor pressure deficit than to strong water stress, and the net CO2 assimilation rate (An) was enhanced as vapor pressure deficits increased. A close relationship between An and stomatal conductance (gs) suggested that the species shared a similar response mechanism. In H. ammodendron, the activity levels of key C4 enzymes were higher, including those of phosphoenolpyruvate carboxylase (PEPC) and nicotinamide adenine dinucleotide phosphate-malate enzyme (NADP-ME), whereas in H. scoparium, the activity level of nicotinamide adenine dinucleotide-malate enzyme (NAD-ME) was higher. Meanwhile, H. scoparium utilized adaptive structural features, including a larger relative vessel area and a shorter distance from vein to stomata, which facilitated the movement of water. These findings implied that some C4 biochemical pathways were present in H. scoparium to respond to environmental challenges. PMID:26257361

  16. Water in the critical zone: soil, water and life from profile to planet

    NASA Astrophysics Data System (ADS)

    Kirkby, Mike

    2015-04-01

    Water is essential to the critical zone between bedrock and the atmosphere, and without water the soil is dead. Water provides the basis for the abundant life within the soil and, interacting with micro-organisms, drives the key processes in the critical zone. This review looks at the balances that control the flow of water through the soil, and how water movement is one of the major controls on the fluxes and transformations that control the formation, evolution and loss of material that controls the 'life' and 'health' of the soil. At regional scales, climate, acting largely through the soil hydrology, plays a major part in determining the type of soils developed - from hyper arid soils dominated by aeolian inputs, through arid and semi-arid soils with largely vertical water exchanges with the atmosphere, to temperate soils with substantial lateral drainage, and humid soils dominated by organic peats. Soil water balance controls the partition of precipitation between evaporative loss, lateral subsurface flow and groundwater recharge, and, in turn, has a major influence on the potential for plant growth and on the lateral connectivity between soils on a hillslope. Sediment and solute balances distinguish soils of accumulation from soils that tend towards a stable chemical depletion ratio. Reflecting the availability of water and the soil material, carbon balance plays a major role in soil horizonation and distinguishes soils dominated by mineral or organic components. At finer catena and catchment scales, lateral connectivity, or its absence, determines how soils evolve through the transfer of water and sediment downslope, creating more or less integrated landscapes in a balance between geomorphological and pedological processes. Within single soil profiles, the movement of water controls the processes of weathering and soil horizonation by ion diffusion, advective leaching and bioturbation, creating horizonation that, in turn, modifies the hydrological responses

  17. Water Extraction from Martian Soil

    NASA Astrophysics Data System (ADS)

    Wiens, J.; Bommarito, F.; Blumenstein, E.; Ellsworth, M.; Cisar, T.; McKinney, B.; Knecht, B.

    2001-01-01

    With the projected growth in space exploration, several milestones have been set for future space programs. One milestone in particular is the landing of a human on the planet Mars. However, one major barrier to the successful placement of persons on Mars is a lack of water on the Martian surface. Because of the massive quantity of water that would be necessary for a mission to Mars, it is not possible to transport the amount necessary from Earth to Mars. Water would be necessary for human consumption as well as a base for jet propulsion fuel. Past unmanned missions to Mars, such as the Viking missions of the 1970's, have revealed the presence of small quantities of water in Martian soil. Research has determined that the water in the soil can be recovered when the soil is heated to a temperature between 200 C and 500 C. Team JFEET has designed a system with the capability to extract water from the soil of Mars, and then meter and deliver the water to a storage tank for later use.

  18. WATER CONSERVATION IN SOIL

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Water conservation is important for agricultural, residential, industrial, and recreational users in all climatic regions, but becomes increasingly important when going from humid to semiarid and arid regions. This report briefly describes techniques that can be used to increase the storage of water...

  19. Remote sensing of soil water content at large scales

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water content at the near surface is a critical parameter for understanding land surface atmosphere interactions, influencing surface energy balances. Using microwave radiometry, an accurate global map of surface soil water content can be generated on a near daily basis. The accuracy of the p...

  20. INTERACTION OF METHYL-TERT BUTYL ETHER AND WATER STRESS ON SEED GERMINATION AND SEEDLING GROWTH IN SOIL MICROCOSMS

    EPA Science Inventory

    Methyl tert-butyl ether (MTBE) is a widespread contaminant in surface and ground water in the United States. Frequently irrigation is used to water fields to germinate planted seeds and sustain plant growth. A likely possibility exists that water used may have some MTBE. Our s...

  1. Simulations and field observations of root water uptake in plots with different soil water availability.

    NASA Astrophysics Data System (ADS)

    Cai, Gaochao; Vanderborght, Jan; Couvreur, Valentin; Javaux, Mathieu; Vereecken, Harry

    2015-04-01

    Root water uptake is a main process in the hydrological cycle and vital for water management in agronomy. In most models of root water uptake, the spatial and temporal soil water status and plant root distributions are required for water flow simulations. However, dynamic root growth and root distributions are not easy and time consuming to measure by normal approaches. Furthermore, root water uptake cannot be measured directly in the field. Therefore, it is necessary to incorporate monitoring data of soil water content and potential and root distributions within a modeling framework to explore the interaction between soil water availability and root water uptake. But, most models are lacking a physically based concept to describe water uptake from soil profiles with vertical variations in soil water availability. In this contribution, we present an experimental setup in which root development, soil water content and soil water potential are monitored non-invasively in two field plots with different soil texture and for three treatments with different soil water availability: natural rain, sheltered and irrigated treatment. Root development is monitored using 7-m long horizontally installed minirhizotubes at six depths with three replicates per treatment. The monitoring data are interpreted using a model that is a one-dimensional upscaled version of root water uptake model that describes flow in the coupled soil-root architecture considering water potential gradients in the system and hydraulic conductances of the soil and root system (Couvreur et al., 2012). This model approach links the total root water uptake to an effective soil water potential in the root zone. The local root water uptake is a function of the difference between the local soil water potential and effective root zone water potential so that compensatory uptake in heterogeneous soil water potential profiles is simulated. The root system conductance is derived from inverse modelling using

  2. iSOIL: Interactions between soil related sciences - Linking geophysics, soil science and digital soil mapping

    NASA Astrophysics Data System (ADS)

    Dietrich, Peter; Werban, Ulrike; Sauer, Uta

    2010-05-01

    High-resolution soil property maps are one major prerequisite for the specific protection of soil functions and restoration of degraded soils as well as sustainable land use, water and environmental management. To generate such maps the combination of digital soil mapping approaches and remote as well as proximal soil sensing techniques is most promising. However, a feasible and reliable combination of these technologies for the investigation of large areas (e.g. catchments and landscapes) and the assessment of soil degradation threats is missing. Furthermore, there is insufficient dissemination of knowledge on digital soil mapping and proximal soil sensing in the scientific community, to relevant authorities as well as prospective users. As one consequence there is inadequate standardization of techniques. At the poster we present the EU collaborative project iSOIL within the 7th framework program of the European Commission. iSOIL focuses on improving fast and reliable mapping methods of soil properties, soil functions and soil degradation risks. This requires the improvement and integration of advanced soil sampling approaches, geophysical and spectroscopic measuring techniques, as well as pedometric and pedophysical approaches. The focus of the iSOIL project is to develop new and to improve existing strategies and innovative methods for generating accurate, high resolution soil property maps. At the same time the developments will reduce costs compared to traditional soil mapping. ISOIL tackles the challenges by the integration of three major components: (i)high resolution, non-destructive geophysical (e.g. Electromagnetic Induction EMI; Ground Penetrating Radar, GPR; magnetics, seismics) and spectroscopic (e.g., Near Surface Infrared, NIR) methods, (ii)Concepts of Digital Soil Mapping (DSM) and pedometrics as well as (iii)optimized soil sampling with respect to profound soil scientific and (geo)statistical strategies. A special focus of iSOIL lies on the

  3. A review on temporal stability of soil water contents

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Temporal stability of soil water content (TS SWC) has been observed across a wide range of soil types, landscapes, climates and scales. A better understanding of TS SWC controls and their interactions needs to be developed. The objective of this work is to develop a comprehensive inventory of publis...

  4. Macroscopic modeling of plant water uptake: soil and root resistances

    NASA Astrophysics Data System (ADS)

    Vogel, Tomas; Votrubova, Jana; Dohnal, Michal; Dusek, Jaromir

    2014-05-01

    The macroscopic physically-based plant root water uptake (RWU) model, based on water-potential-gradient formulation (Vogel et al., 2013), was used to simulate the observed soil-plant-atmosphere interactions at a forest site located in a temperate humid climate of central Europe and to gain an improved insight into the mutual interplay of RWU parameters that affects the soil water distribution in the root zone. In the applied RWU model, the uptake rates are directly proportional to the potential gradient and indirectly proportional to the local soil and root resistances to water flow. The RWU algorithm is implemented in a one-dimensional dual-continuum model of soil water flow based on Richards' equation. The RWU model is defined by four parameters (root length density distribution, average active root radius, radial root resistance, and the threshold value of the root xylem potential). In addition, soil resistance to water extraction by roots is related to soil hydraulic conductivity function and actual soil water content. The RWU model is capable of simulating both the compensatory root water uptake, in situations when reduced uptake from dry layers is compensated by increased uptake from wetter layers, and the root-mediated hydraulic redistribution of soil water, contributing to more natural soil moisture distribution throughout the root zone. The present study focusses on the sensitivity analysis of the combined soil water flow and RWU model responses in respect to variations of RWU model parameters. Vogel T., M. Dohnal, J. Dusek, J. Votrubova, and M. Tesar. 2013. Macroscopic modeling of plant water uptake in a forest stand involving root-mediated soil-water redistribution. Vadose Zone Journal, 12, 10.2136/vzj2012.0154.

  5. Microwave remote sensing of soil water content

    NASA Technical Reports Server (NTRS)

    Cihlar, J.; Ulaby, F. T.

    1975-01-01

    Microwave remote sensing of soils to determine water content was considered. A layered water balance model was developed for determining soil water content in the upper zone (top 30 cm), while soil moisture at greater depths and near the surface during the diurnal cycle was studied using experimental measurements. Soil temperature was investigated by means of a simulation model. Based on both models, moisture and temperature profiles of a hypothetical soil were generated and used to compute microwave soil parameters for a clear summer day. The results suggest that, (1) soil moisture in the upper zone can be predicted on a daily basis for 1 cm depth increments, (2) soil temperature presents no problem if surface temperature can be measured with infrared radiometers, and (3) the microwave response of a bare soil is determined primarily by the moisture at and near the surface. An algorithm is proposed for monitoring large areas which combines the water balance and microwave methods.

  6. Soil water sensing for water balance, ET, and WUE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The soil water balance can be solved for evapotranspiration (ET) using data from either weighing lysimetry or soil water sensing and measurement. Weighing lysimeters are expensive and, although accurate, are difficult to manage and afford little replication. Direct soil water measurement by coring i...

  7. Soil water sensing for water balance, ET and WUE

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The soil water balance can be solved for evapotranspiration (ET) using data from either weighing lysimetry or soil water sensing and measurement. Weighing lysimeters are expensive and, although accurate, are difficult to manage and afford little replication. Direct soil water measurement by coring i...

  8. Soil water repellency of Antarctic soils (Elephant Point). First results

    NASA Astrophysics Data System (ADS)

    Pereira, Paulo; Oliva, Marc; Ruiz Fernández, Jesus

    2015-04-01

    Hydrophobicity it is a natural properties of many soils around the world. Despite the large body of research about soil water hydrophobicity (SWR) in many environments, little information it is available about Antarctic soils and their hydro-geomorphological consequences. According to our knowledge, no previous work was carried out on this environment. Soil samples were collected in the top-soil (0-5 cm) and SWR was analysed according to the water drop penetration test. The preliminary results showed that all the soils collected were hydrophilic, however further research should be carried out in order to understand if SWR changes with soil depth and if have implications on soil infiltration during the summer season.

  9. Soil Water and Temperature System (SWATS) Handbook

    SciTech Connect

    Bond, D

    2005-01-01

    The soil water and temperature system (SWATS) provides vertical profiles of soil temperature, soil-water potential, and soil moisture as a function of depth below the ground surface at hourly intervals. The temperature profiles are measured directly by in situ sensors at the Central Facility and many of the extended facilities of the SGP climate research site. The soil-water potential and soil moisture profiles are derived from measurements of soil temperature rise in response to small inputs of heat. Atmospheric scientists use the data in climate models to determine boundary conditions and to estimate the surface energy flux. The data are also useful to hydrologists, soil scientists, and agricultural scientists for determining the state of the soil.

  10. Biophysical interactions between plant and soil: theory and practice

    NASA Astrophysics Data System (ADS)

    van der Ploeg, Martine

    2016-04-01

    Vegetation plays an essential role in the hydrological cycle, as it regulates the water flux to the atmosphere through evapotranspiration, while it is dependent on adequate water supply. Vegetation shapes the land surface by changing infiltration characteristics as a result of root growth, and controls soil moisture storage, which in turn affect runoff characteristics and groundwater recharge. Vegetation and the underlying geology are in constant interaction, wherein water plays a key role. The resilience of the coupled vegetation-soil system critically depends on its sensitivity to environmental changes. Models are a useful tool to explore interaction and feedbacks between vegetation, soil and landscape. Plants respond biochemically to their environment, while the models used for hydrology are often based on physical interactions. Gene-expression and genotype adaptation may complicate our modelling efforts in for example climate change impacts. Combination of new techniques to assess soil and plant properties facilitates assessment of biophysical interactions. This poster will review these techniques and compare the obtained insights of soil-plant relationships with the current modeling approaches.

  11. Mechanics of wheel-soil interaction

    NASA Technical Reports Server (NTRS)

    Houland, H. J.

    1973-01-01

    An approximate theory for wheel-soil interaction is presented which forms the basis for a practical solution to the problem. It is shown that two fundamental observations render the problem determinate: (1) The line of action of the resultant of radial stresses acting at the wheel soil interface approximately bisects the wheel-soil contact angle for all values of slip. (2) A shear stress surface can be hypothesized. The influence of soil inertia forces is also evaluated. A concept of equivalent cohesion is introduced which allows a convenient experimental comparison for both cohesive and frictional soils. This theory compares favorably with previous analyses and experimental data, and shows that soil inertia forces influencing the motion of a rolling wheel can be significant.

  12. Data assimilation with soil water content sensors and pedotransfer functions in soil water flow modeling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water flow models are based on a set of simplified assumptions about the mechanisms, processes, and parameters of water retention and flow. That causes errors in soil water flow model predictions. Soil water content monitoring data can be used to reduce the errors in models. Data assimilation (...

  13. A minimalist probabilistic description of root zone soil water

    USGS Publications Warehouse

    Milly, P.C.D.

    2001-01-01

    The probabilistic response of depth-integrated soil water to given climatic forcing can be described readily using an existing supply-demand-storage model. An apparently complex interaction of numerous soil, climate, and plant controls can be reduced to a relatively simple expression for the equilibrium probability density function of soil water as a function of only two dimensionless parameters. These are the index of dryness (ratio of mean potential evaporation to mean precipitation) and a dimensionless storage capacity (active root zone soil water capacity divided by mean storm depth). The first parameter is mainly controlled by climate, with surface albedo playing a subsidiary role in determining net radiation. The second is a composite of soil (through moisture retention characteristics), vegetation (through rooting characteristics), and climate (mean storm depth). This minimalist analysis captures many essential features of a more general probabilistic analysis, but with a considerable reduction in complexity and consequent elucidation of the critical controls on soil water variability. In particular, it is shown that (1) the dependence of mean soil water on the index of dryness approaches a step function in the limit of large soil water capacity; (2) soil water variance is usually maximized when the index of dryness equals 1, and the width of the peak varies inversely with dimensionless storage capacity; (3) soil water has a uniform probability density function when the index of dryness is 1 and the dimensionless storage capacity is large; and (4) the soil water probability density function is bimodal if and only if the index of dryness is <1, but this bimodality is pronounced only for artificially small values of the dimensionless storage capacity.

  14. Uptake and Hydraulic Redistribution of Soil Water in a Natural Forested Wetland and in two Contrasting Drained Loblolly Pine Plantations: Quantifying Patterns over Soil-to-Root and Canopy-to-Atmosphere Interactions

    NASA Astrophysics Data System (ADS)

    Domec, J.; King, J. S.; Noormets, A.; Sun, G.; McNulty, S. G.; Gavazzi, M. G.; Treasure, E.; Boggs, J. L.

    2009-05-01

    The conversion of wetlands to intensively managed forest lands in eastern North Carolina is widespread and the consequences on water and carbon balances are not well studied. Quantification of evapotranspiration (ET), tree transpiration and their biophysical regulation are needed for assessing forest water management options. We characterized vertical variation in the diurnal and seasonal soil volumetric water content at 10 cm intervals to evaluate changes in water availability for root uptake and monitored eddy covariance ET and tree transpiration (sap flux) in three contrasting loblolly pine (Pinus taeda L.) stands. Those stands included a 50- yr-old wetland natural regeneration (NG), a 17-yr-old drained mid-rotation plantation (MP) and a 5-yr-old drained plantation (YP) in eastern North Carolina. We also quantified the magnitude of hydraulic redistribution (HR), the passive movement of soil water from deep to shallow roots, to identify factors affecting the seasonal dynamics of root water uptake, root and plant water potentials and stomatal conductance. In NG, soil water content was always at full saturation and total tree water use peaked between 6-7 mm/day, and this stand was used as reference. In MP, soil water content varied with soil depth and total water use from the upper 1m peaked between 4 and 6.5 mm/day during the growing season and was strongly correlated and similar to ET (ET represented 90-95% of total water depletion). In YP, soil water used was limited to the upper 30 cm and was strongly affected by summer drought by declining progressively from 0.9 mm/day in spring to 0.4 m/day in September. After periods of more than 10 days without rain, water extraction in MP shifted to the deeper layers, and recharge from HR approached 20% of ET. During days of high evaporative demand, water use in MP was comparable to NG thanks to HR and to the contribution of deeper roots to water uptake. In YP, HR never contributed for more than 8% of ET. There was no HR

  15. Least limiting water range of soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The least limiting water range (LLWR) has been developed as an index of the soil structural quality. The LLWR was defined as the region bounded by the upper and lower soil water content over which water, oxygen, and mechanical resistance become major limitations for root growth. Thus, it combines th...

  16. Current advancements and challenges in soil-root interactions modelling

    NASA Astrophysics Data System (ADS)

    Schnepf, Andrea; Huber, Katrin; Abesha, Betiglu; Meunier, Felicien; Leitner, Daniel; Roose, Tiina; Javaux, Mathieu; Vanderborght, Jan; Vereecken, Harry

    2015-04-01

    Roots change their surrounding soil chemically, physically and biologically. This includes changes in soil moisture and solute concentration, the exudation of organic substances into the rhizosphere, increased growth of soil microorganisms, or changes in soil structure. The fate of water and solutes in the root zone is highly determined by these root-soil interactions. Mathematical models of soil-root systems in combination with non-invasive techniques able to characterize root systems are a promising tool to understand and predict the behaviour of water and solutes in the root zone. With respect to different fields of applications, predictive mathematical models can contribute to the solution of optimal control problems in plant recourse efficiency. This may result in significant gains in productivity, efficiency and environmental sustainability in various land use activities. Major challenges include the coupling of model parameters of the relevant processes with the surrounding environment such as temperature, nutrient concentration or soil water content. A further challenge is the mathematical description of the different spatial and temporal scales involved. This includes in particular the branched structures formed by root systems or the external mycelium of mycorrhizal fungi. Here, reducing complexity as well as bridging between spatial scales is required. Furthermore, the combination of experimental and mathematical techniques may advance the field enormously. Here, the use of root system, soil and rhizosphere models is presented through a number of modelling case studies, including image based modelling of phosphate uptake by a root with hairs, model-based optimization of root architecture for phosphate uptake from soil, upscaling of rhizosphere models, modelling root growth in structured soil, and the effect of root hydraulic architecture on plant water uptake efficiency and drought resistance.

  17. Current Advancements and Challenges in Soil-Root Interactions Modelling

    NASA Astrophysics Data System (ADS)

    Schnepf, A.; Huber, K.; Abesha, B.; Meunier, F.; Leitner, D.; Roose, T.; Javaux, M.; Vanderborght, J.; Vereecken, H.

    2014-12-01

    Roots change their surrounding soil chemically, physically and biologically. This includes changes in soil moisture and solute concentration, the exudation of organic substances into the rhizosphere, increased growth of soil microorganisms, or changes in soil structure. The fate of water and solutes in the root zone is highly determined by these root-soil interactions. Mathematical models of soil-root systems in combination with non-invasive techniques able to characterize root systems are a promising tool to understand and predict the behaviour of water and solutes in the root zone. With respect to different fields of applications, predictive mathematical models can contribute to the solution of optimal control problems in plant recourse efficiency. This may result in significant gains in productivity, efficiency and environmental sustainability in various land use activities. Major challenges include the coupling of model parameters of the relevant processes with the surrounding environment such as temperature, nutrient concentration or soil water content. A further challenge is the mathematical description of the different spatial and temporal scales involved. This includes in particular the branched structures formed by root systems or the external mycelium of mycorrhizal fungi. Here, reducing complexity as well as bridging between spatial scales is required. Furthermore, the combination of experimental and mathematical techniques may advance the field enormously. Here, the use of root system, soil and rhizosphere models is presented through a number of modelling case studies, including image based modelling of phosphate uptake by a root with hairs, model-based optimization of root architecture for phosphate uptake from soil, upscaling of rhizosphere models, modelling root growth in structured soil, and the effect of root hydraulic architecture on plant water uptake efficiency and drought resistance.

  18. A modified soil water based Richards equation for layered soils

    NASA Astrophysics Data System (ADS)

    Kalinka, F.; Ahrens, B.

    2010-09-01

    Most Soil-Vegetation-Atmosphere-Transfer (SVAT) models like TERRA-ML (implemented e.g. in the CCLM model (www.clm-community.eu)) use the soil moisture based Richards equation to simulate vertical water fluxes in soils, assuming a homogeneous soil type. Recently, high-resolution soil type datasets (e.g. BüK 1000, only for Germany (Federal Institute for Geosciences and Natural Resources, BGR, www.bgr.bund.de) or Harmonized World Soil Database (HWSD, version 1.1, FAO/IIASA/ISRIC/ISSCAS/JRC, March 2009)) have been developed. Deficiencies in the numerical solution of the soil moisture based Richards equation may occur if inhomogeneous soil type data is implemented, because there are possibly discontinuities in soil moisture due to various soil type characteristics. One way to fix this problem is to use the potential based Richards equation, but this may lead to problems in conservation of mass. This presentation will suggest a possible numerical solution of the soil moisture based Richards equation for inhomogeneous soils. The basic idea is to subtract the equilibrium state of it from soil moisture fluxes. This should reduce discontinuities because each soil layer aspires the equilibrium state and therefore differences might be of the same order. First sensitivity studies have been done for the Main river basin, Germany.

  19. Temporal stability of soil water content and soil water flux patterns across agricultural fields

    Technology Transfer Automated Retrieval System (TEKTRAN)

    When an agricultural field is repeatedly surveyed for soil water content, sites often can be spotted where soil is consistently wetter or consistently dryer than average across the study area. Temporal stability presents significant interest for upscaling observed soil water content, improving soil ...

  20. Ecohydrological interactions between soil and trees in Alpine apple orchards

    NASA Astrophysics Data System (ADS)

    Penna, Daniele; Scandellari, Francesca; Zanotelli, Damiano; Michael, Engel; Tagliavini, Massimo; Comiti, Francesco

    2016-04-01

    Tracer-based investigations of water exchanges between soil and trees in natural forested catchments are receiving relevant attention in modern ecohydrology. However, the interactions between tree water use and the hydrological cycle in agricultural environments are still poorly understood. In this work, we use stable isotopes of water (2H and 18O) and electric conductivity as tracers to improve our understanding of the functional interrelations between water generating surface runoff and recharging groundwater, and water taken up by apple trees (Malus domestica, cv. 'Pinova') in an Alpine valley in South Tyrol, Northern Italy. From April to October 2015 we monitored two orchards approximately of the same size (roughly 400 m2) and soil texture (silt loam) located in a flat area at different distance from the Adige/Etsch River (50 m vs. 450 m). We have addressed the following questions: i) at which soil depth do apple trees take up water? ii) do apple trees take up water from shallow groundwater? iii) are there differences in the isotopic composition of the water fluxes between the two sites? Samples for isotopic analysis were taken approximately fortnightly from the river, two groundwater wells close to each field, mobile soil water (from suction cups at 25 cm and 50 cm), open area precipitation, throughfall, irrigation and sap (through a portable pressure bomb). Tightly-bound soil water was also cryogenically extracted from samples taken every 10 cm from 60 cm-long soil cores taken at three locations for each field on one occasion in mid-summer. Ancillary measurements were electrical conductivity of all water sources except for sap. In addition to meteorological and discharge data, soil moisture was continuously measured at 10 cm and 50 cm in three locations, and sap flow on three trees, for each field. Preliminary results show that two water pools with distinct isotopic signature exist: i) river water, groundwater and irrigation water show values relatively

  1. Interactive effects of ozone and climate on water use, soil moisture content and streamflow in a southern Applachian forest in the USA

    SciTech Connect

    McLaughlin, Samuel B.; Wullschleger, Stan D; Sun, G.; Nosal, M.

    2007-01-01

    Documentation of the degree and direction of effects of ozone on transpiration of canopies of mature forest trees is critically needed to model ozone effects on forest water use and growth in a warmer future climate. Patterns of sap flow in stems and soil moisture in the rooting zones of mature trees, coupled with late-season streamflow in three forested watersheds in east Tennessee, USA, were analyzed to determine relative influences of ozone and other climatic variables on canopy physiology and streamflow patterns. Statistically significant increases in whole-tree canopy conductance, depletion of soil moisture in the rooting zone, and reduced late-season streamflow in forested watersheds were detected in response to increasing ambient ozone levels. Short-term changes in canopy water use and empirically modeled streamflow patterns over a 23-yr observation period suggest that current ambient ozone exposures may exacerbate the frequency and level of negative effects of drought on forest growth and stream health.

  2. Water-Mediated Hydrophobic Interactions.

    PubMed

    Ben-Amotz, Dor

    2016-05-27

    Hydrophobic interactions are driven by the combined influence of the direct attraction between oily solutes and an additional water-mediated interaction whose magnitude (and sign) depends sensitively on both solute size and attraction. The resulting delicate balance can lead to a slightly repulsive water-mediated interaction that drives oily molecules apart rather than pushing them together and thus opposes their direct (van der Waals) attraction for each other. As a consequence, competing solute size-dependent crossovers weaken hydrophobic interactions sufficiently that they are only expected to significantly exceed random thermal energy fluctuations for processes that bury more than ∼1 nm(2) of water-exposed area. PMID:27215821

  3. Water-Mediated Hydrophobic Interactions

    NASA Astrophysics Data System (ADS)

    Ben-Amotz, Dor

    2016-05-01

    Hydrophobic interactions are driven by the combined influence of the direct attraction between oily solutes and an additional water-mediated interaction whose magnitude (and sign) depends sensitively on both solute size and attraction. The resulting delicate balance can lead to a slightly repulsive water-mediated interaction that drives oily molecules apart rather than pushing them together and thus opposes their direct (van der Waals) attraction for each other. As a consequence, competing solute size-dependent crossovers weaken hydrophobic interactions sufficiently that they are only expected to significantly exceed random thermal energy fluctuations for processes that bury more than ˜1 nm2 of water-exposed area.

  4. Climate Change Effects on Soil Water and Temperature

    NASA Astrophysics Data System (ADS)

    Seyfried, M. S.; Chandler, D. G.; Marks, D. G.

    2011-12-01

    Soil serves as the critical interface between physical changes in climate and the biological impacts of those changes. While there is general agreement among Global Climate Models concerning the amount and trend of world air temperature change in the upcoming decades, there is less agreement regarding precipitation trends and much less agreement with respect to trends in the "soil climate" (soil water content and temperature). The difficulties with soil are probably related to variable and poorly tested land surface parameterizations. Working at sites spanning a 1000 m elevation gradient in the Reynolds Creek Experimental Watershed (RCEW) in Idaho, we showed that, over a 45 year period, the annual air temperature increased about 2° C. During that time, the amount of precipitation remained constant, but the precipitation phase shifted considerably from snow to rain depending on site elevation. Most predictions for this environment are for drier, warmer soils. We used soil water and temperature data collected at the same sites for the past 30 years in the RCEW to determine if those trends occurred. We found no significant trend in either soil water content or temperature at any site over the 30 year period. The lack of a soil water trend is related to the vegetation dynamics in this semiarid environment, where very low leaf are index values, and very dry soils much of the year, serve to restrict the impact of increased evaporative demand on transpiration. The lack of soil temperature trends is related to interactions with vegetative and snow cover, especially snow cover, which can effectively modulate exceptionally cold air temperatures. In both cases, it is clear that climate change is not directly imprinted on the soil, but affected by interactions with what is growing in, or laying on the soil.

  5. Soil/Structure Interactions in Earthquakes

    NASA Technical Reports Server (NTRS)

    Ramey, G. W.; Moore, R. K.; Yoo, C. H.; Bush, Thomas D., Jr.; Stallings, J. M.

    1986-01-01

    In effort to improve design of Earthquake-resistant structures, mathematical study undertaken to simulate interactions among soil, foundation, and superstructure during various kinds of vibrational excitation. System modeled as three lumped masses connected vertically by springs, with lowest mass connected to horizontal vibrator (representing ground) through springs and dashpot. Behavior of springs described by elastic or elastoplastic force/deformation relationships. Relationships used to approximate nonlinear system behavior and soil/foundation-interface behavior.

  6. Pesticide interactions with soils affected by olive oil mill wastewater

    NASA Astrophysics Data System (ADS)

    Keren, Yonatan; Bukhanovsky, Nadezhda; Borisover, Mikhail

    2013-04-01

    Soil pesticide sorption is well known to affect the fate of pesticides, their bioavailability and the potential to contaminate air and water. Soil - pesticide interactions may be strongly influenced by soil organic matter (SOM) and organic matter (OM)-rich soil amendments. One special OM source in soils is related to olive oil production residues that may include both solid and liquid wastes. In the Mediterranean area, the olive oil production is considered as an important field in the agricultural sector. Due to the significant rise in olive oil production, the amount of wastes is growing respectively. Olive oil mill waste water (OMWW) is the liquid byproduct in the so-called "three phase" technological process. Features of OMWW include the high content of fatty aliphatic components and polyphenols and their often-considered toxicity. One way of OMWW disposal is the land spreading, e.g., in olive orchards. The land application of OMWW (either controlled or not) is supposed to affect the multiple soil properties, including hydrophobicity and the potential of soils to interact with pesticides. Therefore, there is both basic and applied interest in elucidating the interactions between organic compounds and soils affected by OMWW. However, little is known about the impact of OMWW - soil interactions on sorption of organic compounds, and specifically, on sorption of agrochemicals. This paper reports an experimental study of sorption interactions of a series of organic compounds including widely used herbicides such as diuron and simazine, in a range of soils that were affected by OMWW (i) historically or (ii) in the controlled land disposal experiments. It is demonstrated that there is a distinct increase in apparent sorption of organic chemicals in soils affected by OMWW. In selected systems, this increase may be explained by increase in SOM content. However, the SOM quality places a role: the rise in organic compound - soil interactions may both exceed the SOM

  7. Hydrology: The diversified economics of soil water

    NASA Astrophysics Data System (ADS)

    Bowen, Gabriel

    2015-09-01

    Soil water that evaporates or is tapped by plants is largely separate from that which runs into streams and recharges groundwater. This finding has big implications for our understanding of water cycling. See Letter p.91

  8. Modeling abiotic processes of aniline in water-saturated soils

    SciTech Connect

    Fabrega-Duque, J.R.; Jafvert, C.T.; Li, H.; Lee, L.S.

    2000-05-01

    The long-term interactions of aromatic amines with soils are important in defining the fate and transport of these compounds in the environment. Abiotic loss of aniline from the aqueous phase to the soil phase occurs with an initial rapid loss due to reversible mass transfer processes, followed by a slow loss due to irreversible reactions. A kinetic model describing these processes in water-saturated soils was developed and evaluated. The model assumes that instantaneous equilibrium occurs for the following reversible processes: (1) acid dissociation of the protonated organic base (BH+) in the aqueous phase; (2) ion exchange between inorganic divalent cations (D{sup 2+} = Ca{sup 2+} + Mg{sup 2+}) on the soil and the protonated organic base; and (3) partitioning of the nonionic species of aniline (B{sub aq}) to soil organic carbon. The model assumes that irreversible loss of aniline occurs through reaction of B{sub aq} with irreversible sites (C{sub ir}) on the soil. A kinetic rate constant, k{sub ir}, and the total concentration of irreversible sites, C{sub T}, were employed as adjustable model parameters. The model was evaluated as adjustable model parameters. The model was evaluated with measured mass distributions of aniline between water and five soils ranging in pH (4.4--7.3), at contact times ranging from 2 to 1,600 h. Some experiments were performed at different soil mass to water volume ratios. A good fit was obtained with a single value of k{sub ir} for all soils, pH values, and soil-water ratios. To accurately predict soil-water distributions at contact times <24 h, mass transfer of the neutral species to the soil was modeled as a kinetic process, again, assuming that ion exchange processes are instantaneous.

  9. Soil Water and Shallow Groundwater Relations in an Agricultural Hillslope

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Shallow water tables contribute to soil water variations under rolling topography, and soil properties contribute to shallow water table fluctutations. Preferential flow through large soil pores can cause a rise in the water table with little increase in soil water except near the soil surface. Late...

  10. Water as a Reagent for Soil Remediation

    SciTech Connect

    Jayaweera, Indira S.; Marti-Perez, Montserrat; Diaz-Ferrero, Jordi; Sanjurjo, Angel

    2003-03-06

    SRI International conducted experiments in a two-year, two-phase process to develop and evaluate hydrothermal extraction technology, also known as hot water extraction (HWE) technology, for remediating petroleum-contaminated soils. The bench-scale demonstration of the process has shown great promise, and the implementation of this technology will revolutionize the conventional use of water in soil remediation technologies and provide a standalone technology for removal of both volatile and heavy components from contaminated soil.

  11. America's Soil and Water: Condition and Trends.

    ERIC Educational Resources Information Center

    1981

    A review of conditions and trends regarding soil and water resources of rural nonfederal lands of the United States is presented in this publication. Maps, charts, and graphs illustrate the data collected on various aspects of soil and water use and practice. Topic areas considered include: (1) land use patterns; (2) classes of land; (3)…

  12. Characteristics of water infiltration in layered water repellent soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hydrophobic soil can influence soil water infiltration, but information regarding the impacts of different levels of hydrophobicity within a layered soil profile is limited. An infiltration study was conducted to determine the effects of different levels of hydrophobicity and the position of the hyd...

  13. Acid-base characteristics of the Grass Pond watershed in the Adirondack Mountains of New York State, USA: interactions among soil, vegetation and surface waters

    NASA Astrophysics Data System (ADS)

    McEathron, K. M.; Mitchell, M. J.; Zhang, L.

    2013-07-01

    Grass Pond watershed is located within the southwestern Adirondack Mountain region of New York State, USA. This region receives some of the highest rates of acidic deposition in North America and is particularly sensitive to acidic inputs due to many of its soils having shallow depths and being generally base poor. Differences in soil chemistry and tree species between seven subwatersheds were examined in relation to acid-base characteristics of the seven major streams that drain into Grass Pond. Mineral soil pH, stream water BCS (base-cation surplus) and pH exhibited a positive correlation with sugar maple basal area (p = 0.055; 0.48 and 0.39, respectively). Black cherry basal area was inversely correlated with stream water BCS, ANC (acid neutralizing capacity)c and NO3- (p = 0.23; 0.24 and 0.20, respectively). Sugar maple basal areas were positively associated with watershed characteristics associated with the neutralization of atmospheric acidic inputs while in contrast, black cherry basal areas showed opposite relationships to these same watershed characteristics. Canonical correspondence analysis indicated that black cherry had a distinctive relationship with forest floor chemistry apart from the other tree species, specifically a strong positive association with forest floor NH4, while sugar maple had a distinctive relationship with stream chemistry variables, specifically a strong positive association with stream water ANCc, BCS and pH. Our results provide evidence that sugar maple is acid-intolerant or calciphilic tree species and also demonstrate that black cherry is likely an acid-tolerant tree species.

  14. Acid-base characteristics of the Grass Pond watershed in the Adirondack Mountains of New York State, USA: interactions between soil, vegetation and surface waters

    NASA Astrophysics Data System (ADS)

    McEathron, K. M.; Mitchell, M. J.; Zhang, L.

    2012-09-01

    Grass Pond watershed is located within the Southwestern Adirondack Mountain region of New York State, USA. This region receives some of the highest rates of acidic deposition in North America and is particularly sensitive to acidic inputs due to many of its soils having shallow depths and being generally base-poor. Differences in soil chemistry and tree species between seven subwatersheds were examined in relation to acid-base characteristics of the seven major streams that drain into Grass Pond. Mineral soil pH, stream water BCS and pH exhibited a positive correlation with sugar maple basal area (p = 0.055; 0.48 and 0.39, respectively). Black cherry basal area was inversely correlated with stream water BCS, ANCc and NO3- (p = 0.23; 0.24 and 0.20, respectively). Sugar maple basal areas were positively correlated with watershed characteristics associated with the neutralization of atmospheric acidic inputs while in contrast, black cherry basal areas showed opposite relationships to these same watershed characteristics. Canonical Correspondence Analysis indicated that black cherry had a distinctive relationship with forest floor chemistry apart from the other tree species, specifically a strong positive association with forest floor NH4 while sugar maple had a distinctive relationship with stream chemistry variables, specifically a strong positive association with stream water ANCc, BCS and pH. Our results provide evidence that sugar maple is acid-intolerant or calciphilic tree species and also demonstrate that black cherry is likely an acid-tolerant tree species.

  15. Increasing Efficiency of Water Use in Agriculture through Management of Soil Water Repellency to Optimize Soil and Water Productivity

    NASA Astrophysics Data System (ADS)

    Moore, Demie; Kostka, Stan; McMillan, Mica; Gadd, Nick

    2010-05-01

    Water's ability to infiltrate and disperse in soils, and soil's ability to receive, transport, retain, filter and release water are important factors in the efficient use of water in agriculture. Deteriorating soil conditions, including development of soil water repellency, negatively impact hydrological processes and, consequently, the efficiency of rainfall and irrigation. Soil water repellency is increasingly being identified in diverse soils and cropping systems. Recently research has been conducted on the use of novel soil surfactants (co-formulations of alkyl polyglycoside and block copolymer surfactants) to avoid or overcome soil water repellency and enhance water distribution in soils. Results indicate that this is an effective and affordable approach to maintaining or restoring soil and water productivity in irrigated cropping systems. Results from studies conducted in Australia and the United States to determine how this technology modifies soil hydrological behavior and crop yields will be presented. A range of soils and various crops, including potatoes, corn, apples and grapes, were included. Several rates were compared to controls for effect on soil moisture levels, soil water distribution, and crop yield. An economic analysis was also conducted in some trials. Treatments improved rootzone water status, significantly increased crop yield and quality, and in some cases allowed significant reductions in water requirements. Where assessed, a positive economic return was generated. This technology holds promise as a strategy for increasing efficiency of water use in agriculture.

  16. Interaction of fecal coliforms with soil aggregates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Land-applied manures may contain various contaminants that cause water pollution and concomitant health problems. Some of these pollutants are bacteria, and fecal coliforms (FC) have been widely used as an indicator of bacterial contamination. Experiments on bacteria attachment to soil are tradition...

  17. Performance evaluation of TDT soil water content and watermark soil water potential sensors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This study evaluated the performance of digitized Time Domain Transmissometry (TDT) soil water content sensors (Acclima, Inc., Meridian, ID) and resistance-based soil water potential sensors (Watermark 200, Irrometer Company, Inc., Riverside, CA) in two soils. The evaluation was performed by compar...

  18. Water movement in stony soils: The influence of stoniness on soil water content profiles

    NASA Astrophysics Data System (ADS)

    Novak, Viliam; Knava, Karol

    2010-05-01

    WATER MOVEMENT IN STONY SOILS: THE INFLUENCE OF STONINESS ON SOIL WATER CONTENT PROFILES Viliam Novák, Karol Kňava Institute of Hydrology, Slovak Academy of Sciences, Racianska 75, 831 02 Bratislava 3, Slovakia, e-mail: novak@uh.savba.sk Soils containing rock fragments are widespread over the world, on Europe such soil account for 30%, 60% in Mediterranean region. In comparison to fine earth soils (soil particles are less then 2 mm) stony soils contain rock fragments characterized by the low retention capacity and hydraulic conductivity. So, for stony soils -in comparison to the fine-earth soils - is typical lower hydraulic conductivity and retention capacity, which lead to the decrease decrease of infiltration rate and low water retention. So, water movement and its modeling in stony soil would differ from fine earth (usually agricultural) soil. The aim of this contribution is to demonstrate the differences in water movement in homogeneous soil (fine earth) and stony soil. The influence of different stoniness on soil water content and soil water dynamics was studied too. Windthrow at High Tatra mountains in Slovakia (November 2004) cleared nearly 12 000 ha of 80 year conifers and this event initiated complex research of windthrow impact on the ecosystem. The important part of this study was water movement in impacted area. Specific feature of the soil in this area was moraine soil consisting of fine earth, characterized as silty sand, with the relative stone content up to 0.49, increasing with depth. Associated phenomenon to the forest clearing is the decrease of rain interception and higher undercanopy precipitation. Conifers interception capacity can be three times higher than low canopy interception, and can reach up to 40% of annual precipitation in Central Europe. Stones in the soil are decreasing infiltration rate, but paradoxically increased understorey precipitation and followingly the increased cumulative infiltration led to the increase of the soil

  19. mySoil: Crowd-Sourcing Soil Water Repellency Data to Create a Global Assessment

    NASA Astrophysics Data System (ADS)

    Hallin, Ingrid; Robinson, David A.; Doerr, Stefan H.; Douglas, Peter; Lawley, Russell; Shelley, Wayne; Urbanek, Emilia

    2014-05-01

    Soil water repellency (SWR) alters the way water interacts with soil by impacting hydrological and biogeochemical cycling to an extent which is not yet fully understood. Most studies have focused on SWR in specific environments and habitats, mostly in Mediterranean climates, but SWR has been increasingly observed in a range of habitats from the tropics to the northern latitudes. To better assess the distribution of this phenomenon, we propose using citizen science to create a means of crowd-sourcing SWR data from around the globe using the mySoil app. The water drop penetration time (WDPT) test, in which the length of time a drop of water remains on the soil surface is measured and a corresponding qualitative water repellency class is assigned to the soil, provides useful data and is easy to use. We propose adding a simple, standardised WDPT protocol to the mySoil app and web portal so both academics and non-scientists can contribute to the collection of SWR data from around the world. The protocol would include guidelines on drop size and the number of drops to apply, and would encourage inclusion of details such as vegetation cover, soil moisture conditions, last rainfall, and broad habitat. By initially engaging with researchers to create a back bone of respondents, we believe we can develop a global assessment that will reveal the distribution of the SWR phenomenon.

  20. The soil water balance in a mosaic of clumped vegetation

    NASA Astrophysics Data System (ADS)

    Pizzolla, Teresa; Manfreda, Salvatore; Caylor, Kelly; Gioia, Andrea; Iacobellis, Vito

    2014-05-01

    The spatio-temporal distribution of soil moisture influences the plant growth and the distribution of terrestrial vegetation. This effect is more evident in arid and semiarid ecosystems where the interaction between individuals and the water limited conditions play a fundamental role, providing environmental conditions which drive a variety of non-linear ecohydrological response functions (such as transpiration, photosynthesis, leakage). In this context, modeling vegetation patterns at multiple spatial aggregation scales is important to understand how different vegetation structures can modify the soil water distribution and the exchanged fluxes between soil and atmosphere. In the present paper, the effect of different spatial vegetation patterns, under different climatic scenarios, is investigated in a patchy vegetation mosaic generated by a random process of individual tree canopies and their accompanying root system. Vegetation pattern are generated using the mathematical framework proposed by Caylor et al. (2006) characterized by a three dimensional stochastic vegetation structure, based on the density, dispersion, size distribution, and allometry of individuals within a landscape. A Poisson distribution is applied to generate different distribution of individuals paying particular attention on the role of clumping on water distribution dynamics. The soil water balance is evaluated using the analytical expression proposed by Laio et al. (2001) to explore the influence of climate and vegetation patterns on soil water balance steady-state components (such as the average rates of evaporation, the root water uptake and leakage) and on the stress-weighted plant water uptake. Results of numerical simulations show that clumping may be beneficial for water use efficiency at the landscape scale. References Caylor, Kelly K., P. D'Odorico and I. Rodriguez Iturbe: On the ecohydrology of structurally heterogeneous semiarid landscape. Water Resour. Res., 28, W07424, 2006

  1. Water Drainage from Unsaturated Soils in a Centrifuge Permeameter

    NASA Astrophysics Data System (ADS)

    Ornelas, G.; McCartney, J.; Zhang, M.

    2013-12-01

    This study involves an analysis of water drainage from an initially saturated silt layer in a centrifuge permeameter to evaluate the hydraulic properties of the soil layer in unsaturated conditions up to the point where the water phase becomes discontinuous. These properties include the soil water retention curve (SWRC) and the hydraulic conductivity function (HCF). The hydraulic properties of unsaturated silt are used in soil-atmosphere interaction models that take into account the role of infiltration and evaporation of water from soils due to atmospheric interaction. These models are often applied in slope stability analyses, landfill cover design, aquifer recharge analyses, and agricultural engineering. The hydraulic properties are also relevant to recent research concerning geothermal heating and cooling, as they can be used to assess the insulating effects of soil around underground heat exchangers. This study employs a high-speed geotechnical centrifuge to increase the self-weight of a compacted silt specimen atop a filter plate. Under a centrifuge acceleration of N times earth's gravity, the concept of geometric similitude indicates that the water flow process in a small-scale soil layer will be similar to those in a soil layer in the field that is N times thicker. The centrifuge acceleration also results in an increase in the hydraulic gradient across the silt specimen, which causes water to flow out of the pores following Darcy's law. The drainage test was performed until the rate of liquid water flow out of the soil layer slowed to a negligible level, which corresponds to the transition point at which further water flow can only occur due to water vapor diffusion following Fick's law. The data from the drainage test in the centrifuge were used to determine the SWRC and HCF at different depths in the silt specimen, which compared well with similar properties defined using other laboratory tests. The transition point at which liquid water flow stopped (and

  2. New soil water sensors for irrigation management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Effective irrigation management is key to obtaining the most crop production per unit of water applied and increasing production in the face of competing demands on water resources. Management methods have included calculating crop water needs based on weather station measurements, calculating soil ...

  3. Soil water evaporation and crop residues

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crop residues have value when left in the field and also when removed from the field and sold as a commodity. Reducing soil water evaporation (E) is one of the benefits of leaving crop residues in place. E was measured beneath a corn canopy at the soil suface with nearly full coverage by corn stover...

  4. Water retention of biochar amended soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We analyzed the water holding capacities of soils amended with biochars made from switchgrass, pecan shells, peanut hulls, poultry litter, and hardwood sawdust. Soils were amended with 20 g/kg (44 tonnes/ha) of each biochar produced at both high (>500 degrees C) and low (<400 degrees C) temperatures...

  5. Intrusion of Soil Water through Pipe Cracks

    EPA Science Inventory

    This report describes a series of experiments conducted at U.S. EPA’s Test and Evaluation Facility in 2013-2014 to study the intrusion of contaminated soil water into a pipe crack during simulated backflow events. A test rig was used consisting of a 3’ x 3’ x 3’ acrylic soil bo...

  6. The interaction between soil erosion and soil organisms in temperate agroecosystems: nematode redistribution in tramlines

    NASA Astrophysics Data System (ADS)

    Baxter, Craig; Rowan, John S.; McKenzie, Blair M.; Neilson, Roy

    2014-05-01

    Arable agriculture presents a unique set of challenges, and one of the most important is soil erosion. Whilst policy and practice look towards sustainable intensification of production to ensure food security, fundamental gaps in our understanding still exist. The physical processes involved in the detachment, transport and deposition of soil are well characterised but further research considering chemical and nutrient transport, fertiliser and pesticide losses, and environmental impacts to downstream environments is still required. Furthermore the interaction between soil erosion and soil organisms have largely been ignored, even though soil organisms serve a myriad of functions essential in the provision of soil ecosystem goods and services. Here we present the findings of a field-scale experiment into soil biotic redistribution undertaken at the James Hutton Institute's Balruddery Farm, Scotland (Link Tramlines Project XDW8001). Farm vehicle-tyre wheelings left in arable fields (tramlines) to enable crop spraying during the crop growth cycle have been identified as key transport pathways for sediment and associated nutrients. We tested the hypothesis that soil organisms were also transported by tramline erosion. During the winter of 2012/13 an experiment was undertaken to measure soil organism export from unbound hillslope plots subject to four different tramline treatments set out in a randomised block design. We used soil nematodes as a model organism as they are ubiquitous and sensitive to disturbance and an established indicator taxa of biological and physico-chemical changes in soil. Tramline treatments included a control tyre (conventional tractor tyre), a control tyre with a sown tramline, a low pressure tyre with sown tramline, and a control tyre with a spiked harrow. Post-event sampling of rainfall events was undertaken, and a range of variables measured in the laboratory. The spiked harrow treatment produced the greatest overall reductions in nematode

  7. Closing the loop of the soil water retention curve

    USGS Publications Warehouse

    Lu, Ning; Alsherif, N; Wayllace, Alexandra; Godt, Jonathan W.

    2015-01-01

    The authors, to their knowledge for the first time, produced two complete principal soil water retention curves (SWRCs) under both positive and negative matric suction regimes. An innovative testing technique combining the transient water release and imbibition method (TRIM) and constant flow method (CFM) was used to identify the principal paths of SWRC in the positive pore-water pressure regime under unsaturated conditions. A negative matric suction of 9.8 kPa is needed to reach full saturation or close the loop of the SWRC for a silty soil. This work pushes the understanding of the interaction of soil and water into new territory by quantifying the boundaries of the SWRC over the entire suction domain, including both wetting and drying conditions that are relevant to field conditions such as slope wetting under heavy rainfall or rapid groundwater table rise in earthen dams or levees.

  8. Transient soil moisture profile of a water-shedding soil cover in north Queensland, Australia

    NASA Astrophysics Data System (ADS)

    Gonzales, Christopher; Baumgartl, Thomas; Scheuermann, Alexander

    2014-05-01

    In current agricultural and industrial applications, soil moisture determination is limited to point-wise measurements and remote sensing technologies. The former has limitations on spatial resolution while the latter, although has greater coverage in three dimensions, but may not be representative of real-time hydrologic conditions of the substrate. This conference paper discusses the use of elongated soil moisture probes to describe the transient soil moisture profile of water-shedding soil cover trial plots in north Queensland, Australia. Three-metre long flat ribbon cables were installed at designed depths across a soil cover with substrate materials from mining activities comprising of waste rocks and blended tailings. The soil moisture measurement is analysed using spatial time domain reflectometry (STDR) (Scheuermann et al., 2009) Calibration of the flat ribbon cable's soil moisture measurement in waste rocks is undertaken in a glasshouse setting. Soil moisture retention and outflows are monitored at specific time interval by mass balance and water potential measurements. These data sets together with the soil hydrologic properties derived from laboratory and field measurements are used as input in the numerical code on unsaturated flow, Hydrus2D. The soil moisture calculations of the glasshouse calibration using this numerical method are compared with results from the STDR soil moisture data sets. In context, the purpose of the soil cover is to isolate sulphide-rich mine wastes from atmospheric interaction as oxidation and leaching of these materials may result to acid and metalliferous drainage. The long term performance of a soil cover will be described in terms of the quantities and physico-chemical characteristics of its outflows. With the soil moisture probes set at automated and pre-determined measurement time intervals, it is expected to distinguish between macropore and soil moisture flows during high intensity rainfall events and, also continuously

  9. WATER AS A REAGENT FOR SOIL REMEDIATION

    SciTech Connect

    Indira S. Jayaweera; Montserrat Marti-Perez; Jordi Diaz-Ferrero; Angel Sanjurjo

    2001-11-12

    SRI International conducted experiments in a two-year, two-phase process to develop and evaluate hydrothermal extraction technology, also known as hot water extraction (HWE) technology, to separate petroleum-related contaminants and other hazardous pollutants from soil and sediments. In this process, water with added electrolytes (inexpensive and environmentally friendly) is used as the extracting solvent under subcritical conditions (150-300 C). The use of electrolytes allows us to operate reactors under mild conditions and to obtain high separation efficiencies that were hitherto impossible. Unlike common organic solvents, water under subcritical conditions dissolves both organics and inorganics, thus allowing opportunities for separation of both organic and inorganic material from soil. In developing this technology, our systematic approach was to (1) establish fundamental solubility data, (2) conduct treatability studies with industrial soils, and (3) perform a bench-scale demonstration using a highly contaminated soil. The bench-scale demonstration of the process has shown great promise. The next step of the development process is the successful pilot demonstration of this technology. Once pilot tested, this technology can be implemented quite easily, since most of the basic components are readily available from mature technologies (e.g., steam stripping, soil washing, thermal desorption). The implementation of this technology will revolutionize the conventional use of water in soil remediation technologies and will provide a stand-alone technology for removal of both volatile and heavy components from contaminated soil.

  10. Passive Microwave Observation of Soil Water Infiltration

    NASA Technical Reports Server (NTRS)

    Jackson, Thomas J.; Schmugge, Thomas J.; Rawls, Walter J.; ONeill, Peggy E.; Parlange, Marc B.

    1997-01-01

    Infiltration is a time varying process of water entry into soil. Experiments were conducted here using truck based microwave radiometers to observe small plots during and following sprinkler irrigation. Experiments were conducted on a sandy loam soil in 1994 and a silt loam in 1995. Sandy loam soils typically have higher infiltration capabilities than clays. For the sandy loam the observed brightness temperature (TB) quickly reached a nominally constant value during irrigation. When the irrigation was stopped the TB began to increase as drainage took place. The irrigation rates in 1995 with the silt loam soil exceeded the saturated conductivity of the soil. During irrigation the TB values exhibited a pattern that suggests the occurrence of coherent reflection, a rarely observed phenomena under natural conditions. These results suggested the existence of a sharp dielectric boundary (wet over dry soil) that was increasing in depth with time.

  11. Simulating the fate of water in field soil crop environment

    NASA Astrophysics Data System (ADS)

    Cameira, M. R.; Fernando, R. M.; Ahuja, L.; Pereira, L.

    2005-12-01

    grain and forage corn, respectively. Soil water was predicted with an efficiency ranging from 50 to 95% for the silty loam soil and between 56 and 72% for the sandy soil. The purposed calibration procedure allowed the model to predict crop development, yield and the water balance terms, with accuracy that is acceptable in practical applications for complex and spatially variable field conditions. An iterative method was required to account for the strong interaction between the different model components, based upon detailed experimental data on soils and crops.

  12. Geophysical Imaging of Root Architecture and Root-soil Interaction

    NASA Astrophysics Data System (ADS)

    Wu, Y.; Dafflon, B.; Hubbard, S. S.

    2015-12-01

    Roots play a critical role in controlling water and nutrient uptake, soil biogeochemical processes, as well as the physical anchorage for plants. While important processes, such as root hydraulic redistribution for optimal growth and survival have been recognized, representation of roots in climate models, e.g. its carbon storage, carbon resilience, root biomass, and role in regulating water and carbon fluxes across the rhizosphere and atmosphere interface is still challenging. Such a challenge is exacerbated because of the large variations of root architecture and function across species and locations due to both genetic and environmental controls and the lack of methods for quantifying root mass, distribution, dynamics and interaction with soils at field scales. The scale, complexity and the dynamic nature of plant roots call for minimally invasive methods capable of providing quantitative estimation of root architecture, dynamics over time and interactions with the soils. We present a study on root architecture and root-soil interactions using geophysical methods. Parameters and processes of interests include (1) moisture dynamics around root zone and its interaction with plant transpiration and environmental controls and (2) estimation of root structure and properties based on geophysical signals. Both pot and field scale studies were conducted. The pot scale experiments were conducted under controlled conditions and were monitored with cross-well electrical resistivity tomography (ERT), TDR moisture sensors and temperature probes. Pots with and without a tree were compared and the moisture conditions were controlled via a self regulated pumping system. Geophysical monitoring revealed interactions between roots and soils under dynamic soil moisture conditions and the role of roots in regulating the response of the soil system to changes of environmental conditions, e.g. drought and precipitation events. Field scale studies were conducted on natural trees using

  13. Investigation of indigenous water, salt and soil for solar ponds

    NASA Technical Reports Server (NTRS)

    Marsh, H. E.

    1983-01-01

    The existence of salt-gradient solar ponds in nature is a strong indication that the successful exploitation of this phenomenon must account adequately for the influences of the local setting. Sun, weather and other general factors are treated elsewhere. This paper deals with water, salt, and soil. A general methodology for evaluating and, where feasible, adjusting the effects of these elements is under development. Eight essential solar pond characteristics have been identified, along with a variety of their dependencies upon properties of water, salt and soil. The comprehensive methodology, when fully developed, will include laboratory investigation in such diverse areas as brine physical chemistry, light transmission, water treatment, brine-soil interactions, sealants, and others. With the Salton Sea solar pond investigation as an example, some methods under development will be described.

  14. Influence of soil pH on properties of the soil-water interface

    NASA Astrophysics Data System (ADS)

    Diehl, Doerte

    2010-05-01

    of SWR. Sessile drop and Wilhelmy plate contact angles (CAsess and CAwpm resp.) were measured on the four samples from Germany and the data correlated with those of WDPT. The titratable surface charge of these four soils was measured at selected pH values using a particle charge detector (PCD). Changes in SWR with soil pH were found to be influenced by the density and type of sites able to interact with protons at the available surfaces of organic and mineral materials in soil. The maximum SWR occurred for soil at natural pH and where the charge density was minimal. As pH increased, negative surface charge increased due to deprotonation of sites and WDPT decreased. Two types of behaviour were observed: Those in which (i) WDPT shortened with decreasing pH and ii) WDPT was sensibly constant with decreasing pH. The data suggest that the availability and relative abundance of proton active sites at mineral surfaces, and those at organic functional groups influence the behaviour. Bayer, J. V. and G. E. Schaumann (2007). Hydrological processes 21(17): 2266 - 2275. Cerdà, A. and S. H. Doerr (2007). Hydrological Processes 21(17): 2325-2336. Dekker, L. W. and P. D. Jungerius (1990). Dunes of the European coasts, Catena-Verlag. 18: 173-183. Holzhey, C. S. (1968). Symposium on water repellent soils, Riverside, California. Karnok, K. A., E. J. Rowland, et al. (1993). Agronomy Journal 85(5): 983-986. Mataix-Solera, J., V. Arcenegui, et al. (2007). Hydrological Processes 21(17): 2300-2309. Mataix-Solera, J. and S. H. Doerr (2004). Geoderma 118(1-2): 77-88. Roper, M. M. (2005). Australian Journal of Soil research 43: 803-810.

  15. Soil-water dynamics and tree water uptake in the Sacramento Mountains of New Mexico (USA): a stable isotope study

    NASA Astrophysics Data System (ADS)

    Gierke, Casey; Newton, B. Talon; Phillips, Fred M.

    2016-06-01

    In the southwestern United States, precipitation in the high mountains is a primary source of groundwater recharge. Precipitation patterns, soil properties and vegetation largely control the rate and timing of groundwater recharge. The interactions between climate, soil and mountain vegetation thus have important implications for the groundwater supply. This study took place in the Sacramento Mountains, which is the recharge area for multiple regional aquifers in southern New Mexico. The stable isotopes of oxygen and hydrogen were used to determine whether infiltration of precipitation is homogeneously distributed in the soil or whether it is partitioned among soil-water `compartments', from which trees extract water for transpiration as a function of the season. The results indicate that "immobile" or "slow" soil water, which is derived primarily from snowmelt, infiltrates soils in a relatively uniform fashion, filling small pores in the shallow soils. "Mobile" or "fast" soil water, which is mostly associated with summer thunderstorms, infiltrates very quickly through macropores and along preferential flow paths, evading evaporative loss. It was found that throughout the entire year, trees principally use immobile water derived from snowmelt mixed to differing degrees with seasonally available mobile-water sources. The replenishment of these different water pools in soils appears to depend on initial soil-water content, the manner in which the water was introduced to the soil (snowmelt versus intense thunderstorms), and the seasonal variability of the precipitation and evapotranspiration. These results have important implications for the effect of climate change on recharge mechanisms in the Sacramento Mountains.

  16. Soil-water dynamics and tree water uptake in the Sacramento Mountains of New Mexico (USA): a stable isotope study

    NASA Astrophysics Data System (ADS)

    Gierke, Casey; Newton, B. Talon; Phillips, Fred M.

    2016-04-01

    In the southwestern United States, precipitation in the high mountains is a primary source of groundwater recharge. Precipitation patterns, soil properties and vegetation largely control the rate and timing of groundwater recharge. The interactions between climate, soil and mountain vegetation thus have important implications for the groundwater supply. This study took place in the Sacramento Mountains, which is the recharge area for multiple regional aquifers in southern New Mexico. The stable isotopes of oxygen and hydrogen were used to determine whether infiltration of precipitation is homogeneously distributed in the soil or whether it is partitioned among soil-water `compartments', from which trees extract water for transpiration as a function of the season. The results indicate that "immobile" or "slow" soil water, which is derived primarily from snowmelt, infiltrates soils in a relatively uniform fashion, filling small pores in the shallow soils. "Mobile" or "fast" soil water, which is mostly associated with summer thunderstorms, infiltrates very quickly through macropores and along preferential flow paths, evading evaporative loss. It was found that throughout the entire year, trees principally use immobile water derived from snowmelt mixed to differing degrees with seasonally available mobile-water sources. The replenishment of these different water pools in soils appears to depend on initial soil-water content, the manner in which the water was introduced to the soil (snowmelt versus intense thunderstorms), and the seasonal variability of the precipitation and evapotranspiration. These results have important implications for the effect of climate change on recharge mechanisms in the Sacramento Mountains.

  17. Soil water monitoring equipment for irrigation scheduling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Equipment for monitoring soil water content and sometimes bulk electrical conductivity can be used for scheduling irrigations if the accuracy of the equipment is sufficient to avoid damanging plants and wasting water and fertilizer. Irrigation scheduling is the process of deciding when to irrigate a...

  18. Visualisation and quantification of water in bulk and rhizosphere soils using X-ray Computed Tomography

    NASA Astrophysics Data System (ADS)

    Tracy, Saoirse; Daly, Keith; Crout, Neil; Bennett, Malcolm; Pridmore, Tony; Foulkes, John; Roose, Tiina; Mooney, Sacha

    2015-04-01

    Understanding how water is distributed in soil and how it changes during the redistribution process or from root uptake is crucial for enhancing our understanding for managing soil and water resources. The application of X-ray Computed Tomography (CT) to soil science research is now well established; however few studies have utilised the technique for visualising water in pore spaces due to several inherent difficulties. Here we present a new method to visualise the water content of a soil in situ and in three-dimensions at successive drying matric potentials. A water release curve was obtained for different soil types using measurements from their real pore geometries. The water, soil, air and root phases from the images were segmented using image analysis techniques and quantified. These measurements allowed us to characterise pore size, shape and connectivity for both air filled pores and water. The non-destructive technique enabled water to be visualised in situ and repeated scanning allowed wetting patterns to be analysed. The experimental results were validated against conventional laboratory derived water release curves and specifically developed mechanistic models of soil-water-root interactions. Micro-scale revelations of the water-soil-root interfaces enabled us to make macro-scale predictions on water movement in soil. The information and insights obtained on the hydraulic properties of rhizosphere and bulk soil will enhance our understanding of rhizosphere biophysics and improve current water uptake models.

  19. Measured and simulated soil water evaporation from four Great Plains soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The amount of soil water lost during stage one and stage two soil water evaporation is of interest to crop water use modelers. The ratio of measured soil surface temperature (Ts) to air temperature (Ta) was tested as a signal for the transition in soil water evaporation from stage one to stage two d...

  20. Temperature dependence of soil water potential

    SciTech Connect

    Mohamed, A.M.O.; Yong, R.N. ); Cheung, S.C.H. )

    1992-12-01

    To understand the process of coupled heat and water transport, the relationship between temperature and soil water potential must be known. Two clays, Avonlea bentonite and Lake Agassiz clay, are being considered as the clay-based sealing materials for the Canadian nuclear fuel waste disposal vault. Avonlea bentonite is distinguished from Lake Agassiz clay by its high sealing potential in water. A series of experiments was performed in which the two clays were mixed with equal amounts of sand and were compacted to a dry density of 1.67 Mg/m[sup 3] under various moisture contents and temperatures. A psychrometer was placed within the compacted clay-sand to measure the soil water potential based on the electromotive force measured by the psychrometer. The results indicate that the soil water potential at a particular temperature is higher for both clay-sand mixtures than predicted by the change in the surface tension of water; this effect is much more prominent in the Avonlea bentonite and at low moisture contents. The paper presents empirical equations relating the soil water potential with the moisture content and temperature of the two clay-sand mixtures. 24 refs., 8 figs., 2 tabs.

  1. Spatio-temporal soil moisture distribution and subsurface water flow in the Shale Hills Catchment

    NASA Astrophysics Data System (ADS)

    Zhou, X.; Lin, H.; Zhu, Q.

    2006-12-01

    Systematic and dynamic soil moisture monitoring is needed to characterize areal soil moisture distribution and model subsurface water flow at various scales. Further understanding of soil-water interactions is the key to explore subsurface water flow and its pathways. Hydropedologic approaches integrating soils information with hydrological processes were used to investigate subsurface water flow (vertical and lateral) and possible flow pathways in the 7.9-ha Shale Hills Catchment in central Pennsylvania. Automatic monitoring systems were installed at seven sites using an array of soil matric potential probes (Campbell Scientific 229 and Decagon matric potential probes) and water content probes (Decagon ECH2O-5). These sites are distributed at different landforms (hilltop, hillslope, and valley floor), representing five soil series (Berks, Blairton, Ernest, Rushtown, Weikert). Probes were inserted at different soil depths as well as their interfaces. The positions of probe installation were designed based on site-specific soil morphology and soil properties from laboratory analysis (e.g., soil texture, bulk density, hydraulic conductivity, water retention). A rain gauge was also installed at each monitoring site. The results showed that different soil types, even different soil layers of the same soil type, displayed different hydrological behaviors. There were evidences that lateral flow contributes to the water flow in the Shale Hills Catchment.

  2. Using soil water sensors to improve irrigation management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Irrigation water management has to do with the appropriate application of water to soils, in terms of amounts, rates, and timing to satisfy crop water demands while protecting the soil and water resources from degradation. In this regard, sensors can be used to monitor the soil water status; and som...

  3. Effect of corn or soybean row position on soil water

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crop plants can funnel water to the soil and increase water content more in the row relative to the interrow. Because the row intercepts more soil water after rains and higher root density, the soil may also dry out more between rains than does soil in the interrow. The purpose of this study was to ...

  4. Soil water repellency affects production and transport of CO2 and CH4 in soil

    NASA Astrophysics Data System (ADS)

    Urbanek, Emilia; Qassem, Khalid

    2016-04-01

    Soil moisture is known to be vital in controlling both the production and transport of C gases in soil. Water availability regulates the decomposition rates of soil organic matter by the microorganisms, while the proportion of water/air filled pores controls the transport of gases within the soil and at the soil-atmosphere interface. Many experimental studies and process models looking at soil C gas fluxes assume that soil water is uniformly distributed and soil is easily wettable. Most soils, however, exhibit some degree of soil water repellency (i.e. hydrophobicity) and do not wet spontaneously when dry or moderately moist. They have restricted infiltration and conductivity of water, which also results in extremely heterogeneous soil water distribution. This is a world-wide occurring phenomenon which is particularly common under permanent vegetation e.g. forest, grass and shrub vegetation. This study investigates the effect of soil water repellency on microbial respiration, CO2 transport within the soil and C gas fluxes between the soil and the atmosphere. The results from the field monitoring and laboratory experiments show that soil water repellency results in non-uniform water distribution in the soil which affects the CO2 and CH4 gas fluxes. The main conclusion from the study is that water repellency not only affects the water relations in the soil, but has also a great impact on greenhouse gas production and transport and therefore should be included as an important parameter during the sites monitoring and modelling of gas fluxes.

  5. Estimating In-situ Soil-Water Retention and Field Water Capacity in Two Contrasting Soil Textures

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A priori knowledge of the in-situ soil field water capacity (FWC) and the soil-water retention curve for soils is important for the effective irrigation management and scheduling of many crops. The primary objective of this study was to estimate the in-situ FWC using the soil-water retention curve d...

  6. Soil Water: Advanced Crop and Soil Science. A Course of Study.

    ERIC Educational Resources Information Center

    Miller, Larry E.

    The course of study represents the fourth of six modules in advanced crop and soil science and introduces the agriculture student to the topic of soil water. Upon completing the three day module, the student will be able to classify water as to its presence in the soil, outline the hydrological cycle, list the ways water is lost from the soil,…

  7. Interactions between soil thermal and hydrological dynamics in the response of Alaska ecosystems to fire disturbance

    USGS Publications Warehouse

    Yi, Shuhua; McGuire, Anthony; Harden, Jennifer; Kasischke, Eric; Manies, Kristen L.; Hinzman, Larry; Liljedahl, Anna K.; Randerson, J.; Liu, Heping; Romanovsky, V.adimir E; Marchenko, Sergey S.; Kim, Yongwon

    2009-01-01

    Soil temperature and moisture are important factors that control many ecosystem processes. However, interactions between soil thermal and hydrological processes are not adequately understood in cold regions, where the frozen soil, fire disturbance, and soil drainage play important roles in controlling interactions among these processes. These interactions were investigated with a new ecosystem model framework, the dynamic organic soil version of the Terrestrial Ecosystem Model, that incorporates an efficient and stable numerical scheme for simulating soil thermal and hydrological dynamics within soil profiles that contain a live moss horizon, fibrous and amorphous organic horizons, and mineral soil horizons. The performance of the model was evaluated for a tundra burn site that had both preburn and postburn measurements, two black spruce fire chronosequences (representing space-for-time substitutions in well and intermediately drained conditions), and a poorly drained black spruce site. Although space-for-time substitutions present challenges in model-data comparison, the model demonstrates substantial ability in simulating the dynamics of evapotranspiration, soil temperature, active layer depth, soil moisture, and water table depth in response to both climate variability and fire disturbance. Several differences between model simulations and field measurements identified key challenges for evaluating/improving model performance that include (1) proper representation of discrepancies between air temperature and ground surface temperature; (2) minimization of precipitation biases in the driving data sets; (3) improvement of the measurement accuracy of soil moisture in surface organic horizons; and (4) proper specification of organic horizon depth/properties, and soil thermal conductivity.

  8. An overview of soil water sensors for salinity & irrigation management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Irrigation water management has to do with the appropriate application of water to soils, in terms of amounts, rates, and timing to satisfy crop water demands while protecting the soil and water resources from degradation. Accurate irrigation management is even more important in salt affected soils ...

  9. The impact of land use changes on water pathways, soil formation and soil functioning

    NASA Astrophysics Data System (ADS)

    Robinet, Jérémy; Ameijeiras-Mariño, Yolanda; Minella, Jean P. G.; Vanderborght, Jan; Govers, Gerard

    2015-04-01

    scale. The combined interpretation of these information sources will improve our understanding of the interactions between the water fluxes and the soil system under different land use systems. Combining these data with detailed studies of clay mineralogy and weathering will allow to gain first insights on how land use changes may affect biogeochemical processes and soil weathering at the landscape scale.

  10. Soil and Water Conservation Activities for Scouts.

    ERIC Educational Resources Information Center

    Soil Conservation Service (USDA), Washington, DC.

    The purpose of the learning activities outlined in this booklet is to help Scouts understand some conservation principles which hopefully will lead to the development of an attitude of concern for the environment and a commitment to help with the task of using and managing soil, water, and other natural resources for long range needs as well as…

  11. SOIL AND WATER ASSESSMENT TOOL (SWAT)

    EPA Science Inventory

    Soil and Water Assessment Tool (SWAT) is the continuation of a long-term effort of nonpoint source pollution modeling with the US Department of Agriculture -Agricultural Research Service (ARS). SWAT is a continuous time model that operates on a daily time step. The objective in ...

  12. Selenium in Oklahoma ground water and soil

    SciTech Connect

    Atalay, A.; Vir Maggon, D.

    1991-03-30

    Selenium with a consumption of 2 liters per day (5). The objectives of this study are: (1) to determine the concentrations of Se in Oklahoma ground water and soil samples. (2) to map the geographical distribution of Se species in Oklahoma. (3) to relate groundwater depth, pH and geology with concentration of Se.

  13. Displacement of soil pore water by trichloroethylene

    USGS Publications Warehouse

    Wershaw, R. L.; Aiken, G.R.; Imbrigiotta, T.E.; Goldberg, M.C.

    1994-01-01

    Dense nonaqueous phase liquids (DNAPLS) are important pollutants because of their widespread use as chemical and industrial solvents. An example of the pollution caused by the discharge of DNAPLs is found at the Picatinny Arsenal, New Jersey, where trichloroethylene (TCE) has been discharged directly into the unsaturated zone. This discharge has resulted in the formation of a plume of TCE-contaminated water in the aquifer downgradient of the discharge. A zone of dark-colored groundwater containing a high dissolved organic C content has been found near the point of discharge of the TCE. The colored-water plume extends from the point of discharge at least 30 m (100 feet) downgradient. Fulvic acids isolated from the colored-waters plume, from water from a background well that has not been affected by the discharge of chlorinated solvents, and from soil pore water collected in a lysimeter installed at an uncontaminated site upgradient of the study area have been compared. Nuclear magnetic resonance spectra of the fulvic acids from the colored waters and from the lysimeter are very similar, but are markedly different from the nuclear magnetic resonance spectrum of the fulvic acid from the background well. The three-dimensional fluorescence spectrum and the DOC fractionation profile of the colored groundwater and the soil pore water are very similar to each other, but quite different from those of the background water. It is proposed from these observations that this colored water is soil pore water that has been displaced by a separate DNAPL liquid phase downward to the saturated zone.

  14. Soil Texture and Cultivar Effects on Rice (Oryza sativa, L.) Grain Yield, Yield Components and Water Productivity in Three Water Regimes

    PubMed Central

    Dou, Fugen; Soriano, Junel; Tabien, Rodante E.; Chen, Kun

    2016-01-01

    The objective of this study was to determine the effects of water regime/soil condition (continuous flooding, saturated, and aerobic), cultivar (‘Cocodrie’ and ‘Rondo’), and soil texture (clay and sandy loam) on rice grain yield, yield components and water productivity using a greenhouse trial. Rice grain yield was significantly affected by soil texture and the interaction between water regime and cultivar. Significantly higher yield was obtained in continuous flooding than in aerobic and saturated soil conditions but the latter treatments were comparable to each other. For Rondo, its grain yield has decreased with soil water regimes in the order of continuous flooding, saturated and aerobic treatments. The rice grain yield in clay soil was 46% higher than in sandy loam soil averaged across cultivar and water regime. Compared to aerobic condition, saturated and continuous flooding treatments had greater panicle numbers. In addition, panicle number in clay soil was 25% higher than in sandy loam soil. The spikelet number of Cocodrie was 29% greater than that of Rondo, indicating that rice cultivar had greater effect on spikelet number than soil type and water management. Water productivity was significantly affected by the interaction of water regime and cultivar. Compared to sandy loam soil, clay soil was 25% higher in water productivity. Our results indicated that cultivar selection and soil texture are important factors in deciding what water management option to practice. PMID:26978525

  15. Capacitive Soil Moisture Sensor for Plant Watering

    NASA Astrophysics Data System (ADS)

    Maier, Thomas; Kamm, Lukas

    2016-04-01

    How can you realize a water saving and demand-driven plant watering device? To achieve this you need a sensor, which precisely detects the soil moisture. Designing such a sensor is the topic of this poster. We approached this subject with comparing several physical properties of water, e.g. the conductivity, permittivity, heat capacity and the soil water potential, which are suitable to detect the soil moisture via an electronic device. For our project we have developed a sensor device, which measures the soil moisture and provides the measured values for a plant watering system via a wireless bluetooth 4.0 network. Different sensor setups have been analyzed and the final sensor is the result of many iterative steps of improvement. In the end we tested the precision of our sensor and compared the results with theoretical values. The sensor is currently being used in the Botanical Garden of the Friedrich-Alexander-University in a long-term test. This will show how good the usability in the real field is. On the basis of these findings a marketable sensor will soon be available. Furthermore a more specific type of this sensor has been designed for the EU:CROPIS Space Project, where tomato plants will grow at different gravitational forces. Due to a very small (15mm x 85mm x 1.5mm) and light (5 gramm) realisation, our sensor has been selected for the space program. Now the scientists can monitor the water content of the substrate of the tomato plants in outer space and water the plants on demand.

  16. CHEMFLO: ONE-DIMENSIONAL WATER AND CHEMICAL MOVEMENT IN UNSATURATED SOILS

    EPA Science Inventory

    An interactive software system was developed to enable decision-makers, regulators, policy-makers, scientists, consultants, and students to simulate the movement of waterand chemicals in unsaturated soils. Water movement is modeled using Richards (1931) - equation. Chemical trans...

  17. Effects of Estimating Soil Hydraulic Properties and Root Growth Factor on Soil Water Balance and Crop Production

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Increasing water use efficiency (WUE) is one of the oldest goals in agricultural sciences, yet it is still not fully understood and achieved due to the complexity of soil-weather-management interactions. System models that quantify these interactions are increasingly used for optimizing crop WUE, es...

  18. Stochastic Modeling of Soil Water and Plant Water Stress Using Cumulant Expansion Theory and Its Application to Climate Change Scenarios

    NASA Astrophysics Data System (ADS)

    Kim, S.; Lee, A.; Keem, M.; Shin, H.

    2009-12-01

    For better understanding of soil water and plant water stress dynamics, a stochastic soil water and plant water stress model will be proposed and applied to climate change impact assessment. The proposed model is derived by using cumulant expansion theory from a stochastic differential equation with stochastic rainfall forcings. This model has the advantage of providing the probabilistic solution in the form of a probability distribution function, from which the ensemble average behavior of the system can be obtained easily. Also, since this model uses only the statistics of rainfall time series, the effect of different climate conditions on the soil water and plant water stress dynamics can be incorporated effectively. The simulation result of soil water confirms that the proposed model can reproduce the observation properly and shows that the soil water behaves with consistent cycle based on the precipitation pattern. In order to understand the impact of climate change on soil water and plant water stress behaviors, the RCM data developed by Korean Meteorological Administration (KMA RCM) and the third GCM by Canadian Centre for Climate Modeling and Analysis(CGCM3) are used with two time periods of 2051~2060 and 2091~2100. With all the simulation results, it can be conclude that the simulation results will be different with what climate change scenario is selected since different climate change model predicts different soil water and plant water stress behaviors. This analysis can be expected as a starting point for better understanding of the effect of soil water on ecosystem dynamics such as climate-soil-vegetation interaction. Figure 1. The evolution of the soil water PDF. The soil water PDFs have two different patterns according to wet season from June to September and dry season from October to May. From such result, it can be inferred that the mechanisms which influence the soil water behavior are different in wet and dry seasons. That is to say, in wet

  19. A Coupled Modeling Approach for Root-Soil Interaction Processes Using DuMuX

    NASA Astrophysics Data System (ADS)

    Schröder, N.; Helmig, R.; Flemisch, B.; Koch, T.

    2015-12-01

    The water and nutrient uptake of plant roots in soils have a crucial influence on soil physical processes. The interacting processes between plant roots and soil are important for several agricultural problems, for example water management or leaching of pesticides. However, the coupled mechanisms of local soil and root water flow, transport of dissolved substances, root growth, and root uptake are difficult to measure and thus experimental data are rare. Numerical models can be used to understand these complex soil-root systems and help to analyze and interpret experimental measurements. The model approach presented here couples a root system and a soil model. Crucial for this approach is the 1D-3D grid coupling which combines a 1D network grid (root system) with the 3D soil grid. Based on that grid coupling, local processes are defined, for instance the local water uptake of a single root segment. Here, the interface conditions between roots and soil play a major role and we use local grid refinement strategies to better resolve these interface processes. This grid refinement of the 3D soil grid is based on the root network (1D grid) and adapts if root growth occurs. It offers the possibility to describe processes in the soil-plant continuum in a more physical manner avoiding empirical descriptions of root water uptake as a function of bulk matric potential, osmotic potential, root length density, and transpiration rate. Our coupling approach is included into the framework of DuMux, an open-source simulator for flow and transport processes in porous media. This implementation combines biological, chemical and physical processes in soil, inside roots, and at root-soil interfaces, and is contained in a sustainable and consistent framework for the implementation. We will show example simulations describing water flow, solute transport and root growth in a soil-root system.

  20. Seasonal and long-term effects of CO2 and O3 on water loss in ponderosa pine and their interaction with climate and soil moisture

    EPA Science Inventory

    Evapotranspiration (ET) is driven by evaporative demand, available solar energy and soil moisture (SM) as well as by plant physiological activity which may be substantially affected by elevated CO2 and O3. A multi-year study was conducted in outdoor sunlit-controlled environment ...

  1. Seasonal and long-term effects of CO2 and O3 and their interaction with climate and soil moisture on water loss in ponderosa pine

    EPA Science Inventory

    Evapotranspiration (ET) is driven by evaporative demand, available solar energy and soil moisture as well as by physiological plant activity which may be substantially affected by elevated CO2 and O3. A multi-year study was conducted in outdoor sun-lit controlled-environment cha...

  2. Numerical Modeling of Coupled Water, Vapor and Energy in Soils and at the Soil-Atmosphere Interface

    NASA Astrophysics Data System (ADS)

    Simunek, J.; Bristow, K. L.; Saito, H.

    2015-12-01

    It is broadly accepted that mass and energy fluxes in the subsurface in general, and in arid and semi-arid regions in particular, are closely coupled and cannot be evaluated without considering their mutual interactions. However, only a few numerical models (if any) consider coupled water, vapor and energy transport in both the subsurface and at the soil-atmosphere interface. While the subsurface is commonly implemented in existing models, which often consider both isothermal and thermally induced water and vapor flow, the effects of slope inclination, slope azimuth, variable surface albedo and plant shading on incoming radiation and spatially variable surface mass and energy balance, and consequently soil moisture distribution, is rarely considered. In this presentation we discuss these missing elements and our attempts to implement them into the HYDRUS model. We demonstrate implications of some of their interactions, their impact on the spatial distributions of soil temperature and water content, and their effect on soil evaporation.

  3. Surface water and groundwater interactions in coastal wetlands

    NASA Astrophysics Data System (ADS)

    Li, Ling; Xin, Pei; Shen, Chengji

    2014-05-01

    Salt marshes are an important wetland system in the upper intertidal zone, interfacing the land and coastal water. Dominated by salt-tolerant plants, these wetlands provide essential eco-environmental services for maintaining coastal biodiversity. They also act as sediment traps and help stabilize the coastline. While they play an active role in moderating greenhouse gas emissions, these wetlands have become increasingly vulnerable to the impact of global climate change. Salt marshes are a complex hydrological system characterized by strong, dynamic interactions between surface water and groundwater, which underpin the wetland's eco-functionality. Bordered with coastal water, the marsh system undergoes cycles of inundation and exposure driven by the tide. This leads to dynamic, complex pore-water flow and solute transport in the marsh soil. Pore-water circulations occur at different spatial and temporal scales with strong link to the marsh topography. These circulations control solute transport between the marsh soil and the tidal creek, and ultimately affect the overall nutrient exchange between the marsh and coastal water. The pore-water flows also dictate the soil aeration conditions, which in turn affect marsh plant growth. This talk presents results and findings from recent numerical and experimental studies, focusing on the pore-water flow behaviour in the marsh soil under the influence of tides and density-gradients.

  4. Stem-root flow effect on soil-atmosphere interactions and uncertainty assessments

    NASA Astrophysics Data System (ADS)

    Kuo, T.-H.; Chen, J.-P.; Xue, Y.

    2015-11-01

    Soil water can rapidly enter deeper layers via vertical redistribution of soil water through the stem-root flow mechanism. This study develops the stem-root flow parameterization scheme and coupled this scheme with the Simplified Simple Biosphere model (SSiB) to analyze its effects on land-atmospheric interactions. The SSiB model was tested in a single column mode using the Lien Hua Chih (LHC) measurements conducted in Taiwan and HAPEX-Mobilhy (HAPEX) measurements in France. The results show that stem-root flow generally caused a decrease in the moisture content at the top soil layer and moistened the deeper soil layers. Such soil moisture redistribution results in significant changes in heat flux exchange between land and atmosphere. In the humid environment at LHC, the stem-root flow effect on transpiration was minimal, and the main influence on energy flux was through reduced soil evaporation that led to higher soil temperature and greater sensible heat flux. In the Mediterranean environment of HAPEX, the stem-root flow significantly affected plant transpiration and soil evaporation, as well as associated changes in canopy and soil temperatures. However, the effect on transpiration could either be positive or negative depending on the relative changes in the moisture content of the top soil vs. deeper soil layers due to stem-root flow and soil moisture diffusion processes.

  5. Response of three soil water sensors to variable solution electrical conductivity in different soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Commercial dielectric soil water sensors may improve management of irrigated agriculture by providing continuous field soil water information. Use of these sensors is partly limited by sensor sensitivity to variations in soil salinity and texture, which force expensive, time consuming, soil specific...

  6. In-situ Field Capacity and Soil Water Retention Measurements in Two Contrasting Soil Textures

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of the in-situ field capacity and soil-water retention curve for soils is important for effective irrigation management and scheduling. The primary objective of this study was to estimate in-situ field capacity and soil water retention curves in the field using continually monitoring soil ...

  7. Sensible heat observations reveal soil-water evaporation dynamics

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water evaporation is important at scales ranging from microbial ecology to large-scale climate. Yet, routine measurments are unable to capture rapidly shifting near-surface soil heat and water processes involved in soil-water evaporation. The objective of this study was to determine the depth a...

  8. Principles of water capture, evaporation, and soil water retention

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Successful dryland crop production in semiarid environments is dependent upon efficient storage of precipitation and use of stored soil water supplies. The objectives of this presentation are to: 1. Summarize information regarding the effects of time of year; environmental parameters; residue orient...

  9. Soil water content and soil disaggregation by disking affects PM10 emissions.

    PubMed

    Madden, Nicholaus M; Southard, Randal J; Mitchell, Jeff P

    2009-01-01

    Row crop agriculture in California's San Joaquin Valley is a major contributor of particulate matter <10 microm in aerodynamic diameter (PM10). The California Air Resources Board uses fixed PM10 emission values for various tillage operations to monitor and design attainment strategies. However, fixed emission values do not reflect emissions produced by a single implement operating under different soil conditions. This 2-yr study evaluated how PM10 mass concentrations (microg L(-1)) from disking change as a function of gravimetric soil water content (GWC), number of sequential diskings (D1, D2, D3), and the soil's weighted mean ped diameter (WMPD). Results showed PM10 increased logarithmically as the soil dried from a GWC of 14 to 4%. Average PM10 values at the lower GWCs were six to eight times greater than at the higher GWCs. Number of diskings also increased PM10, especially in drier soil. Below a GWC of 7%, PM10 for D3 was about twice that for D1. Despite strong correlations between more disking and lower WMPD, a lower WMPD did not always result in an increase in PM10. This underscored the role soil water plays in reducing PM10 at high GWCs despite low WMPDs from multiple diskings. Three-way interactions between GWC, disking, and PM10 showed, on average, that the magnitude of PM10 produced by D1 was 1.3 to 1.6 times lower than by D3, despite having insignificantly different GWC. Therefore, a disking operation can yield two different PM10 values under similar GWCs if the amount of soil disaggregation is different. Our results show that inclusion of soil parameters in PM10 emission estimates is essential to describing agriculture's role in air quality violations and to assess the value of proposed mitigation measures, such as conservation tillage. PMID:19141793

  10. Sorption interactions of organic compounds with soils affected by agricultural olive mill wastewater.

    PubMed

    Keren, Yonatan; Borisover, Mikhail; Bukhanovsky, Nadezhda

    2015-11-01

    The organic compound-soil interactions may be strongly influenced by changes in soil organic matter (OM) which affects the environmental fate of multiple organic pollutants. The soil OM changes may be caused by land disposal of various OM-containing wastes. One unique type of OM-rich waste is olive mill-related wastewater (OMW) characterized by high levels of OM, the presence of fatty aliphatics and polyphenolic aromatics. The systematic data on effects of the land-applied OMW on organic compound-soil interactions is lacking. Therefore, aqueous sorption of simazine and diuron, two herbicides, was examined in batch experiments onto three soils, including untreated and OMW-affected samples. Typically, the organic compound-soil interactions increased following the prior land application of OMW. This increase is associated with the changes in sorption mechanisms and cannot be attributed solely to the increase in soil organic carbon content. A novel observation is that the OMW application changes the soil-sorbent matrix in such a way that the solute uptake may become cooperative or the existing ability of a soil sorbent to cooperatively sorb organic molecules from water may become characterized by a larger affinity. The remarkable finding of this study was that in some cases a cooperative uptake of organic molecules by soils makes itself evident in distinct sigmoidal sorption isotherms rarely observed in soil sorption of non-ionized organic compounds; the cooperative herbicide-soil interactions may be characterized by the Hill model coefficients. However, no single trend was found for the effect of applied OMW on the mechanisms of organic compound-soil interactions. PMID:26183941

  11. Water movement through an experimental soil liner

    USGS Publications Warehouse

    Krapac, I.G.; Cartwright, K.; Panno, S.V.; Hensel, B.R.; Rehfeldt, K.R.; Herzog, B.L.

    1991-01-01

    A field-scale soil liner was constructed to test whether compacted soil barriers in cover and liner systems could be built to meet the U.S. EPA saturated hydraulic conductivity requirement (???1 x 10-7 cm s-1). The 8 x 15 x 0.9m liner was constructed in 15 cm compacted lifts using a 20,037 kg pad-foot compactor and standard engineering practices. Water infiltration into the liner has been monitored for one year. Monitoring will continue until water break through at the base of the liner occurs. Estimated saturated hydraulic conductivities were 2.5 x 10-9, 4.0 x 10-8, and 5.0 x 10-8 cm s-1 based on measurements of water infiltration into the liner by large- and small-ring infiltrometers and a water balance analysis, respectively. Also investigated in this research was the variability of the liner's hydraulic properties and estimates of the transit times for water and tracers. Small variances exhibited by small-ring flux data suggested that the liner was homogeneous with respect to infiltration fluxes. The predictions of water and tracer breakthrough at the base of the liner ranged from 2.4-12.6 y, depending on the method of calculation and assumptions made. The liner appeared to be saturated to a depth between 18 and 33 cm at the end of the first year of monitoring. Transit time calculations cannot be verified yet, since breakthrough has not occurred. The work conducted so far indicates that compacted soil barriers can be constructed to meet the saturated hydraulic conductivity requirement established by the U.S. EPA.A field-scale soil liner was constructed to test whether compacted soil barriers in cover and liner systems could be built to meet the U.S. EPA saturated hydraulic conductivity requirement (??? 1 ?? 10-7 cm s-1). The 8 ?? 15 ?? 0.9 m liner was constructed in 15 cm compacted lifts using a 20.037 kg pad-foot compactor and standard engineering practices. Water infiltration into the liner has been monitored for one year. Monitoring will continue until water

  12. Temporal patterns of infiltration into a water repellent soil under field conditions

    NASA Astrophysics Data System (ADS)

    Ward, Phil; Roper, Margaret; Micin, Shayne; Jongepier, Ramona

    2014-05-01

    Water repellency causes substantial economic losses for farmers in southern Australia through impacts on crop growth and weed germination. However, recent research has demonstrated that laboratory measurements of water repellency may not be a reliable indicator of the severity of symptoms experienced in the field. In particular, crop residue retention and minimal soil disturbance led to increased water repellency, but was also associated with higher soil water contents measured at strategic times of the year. Little is known about the temporal patterns of soil water storage close to the soil surface in a water repellent sand. In this research we measured soil water content at a depth of 0.05 m at 15-minute intervals from June 2011 to October 2012, under various treatment combinations of residue retention and soil disturbance. Measurements were made in both 'crop row' and 'crop inter-row' positions. For a rainfall event (9.2 mm) in March 2012, prior to crop seeding, plots previously established with no-till absorbed significantly more water (increase in soil water content of 0.074 v/v) than plots conventionally cultivated (0.038 v/v). In June 2012 (12.6 mm), 4 weeks after crop seeding, tillage was again significant, and there was a significant interaction between tillage and 'row' or 'inter-row' position. These results demonstrate the importance of crop management in modifying the response of water repellent soils to rainfall in the field.

  13. Combining Neutron and Magnetic Resonance Imaging to Study the Interaction of Plant Rootsand Soil

    NASA Astrophysics Data System (ADS)

    Oswald, Sascha E.; Tötzke, Christian; Haber-Pohlmeier, Sabina; Pohlmeier, Andreas; Kaestner, Anders P.; Lehmann, Eberhard

    The soil in direct vicinity of the roots, the root-soil interface or so called rhizosphere, is heavily modified by the activity of roots, compared to bulk soil, e.g. in respect to microbiology and soil chemistry. It has turned out that the root-soil interface, though small in size, also plays a decisive role in the hydraulics controlling the water flow from bulk soil into the roots. A promising approach for the non-invasive investigation of water dynamics, water flow and solute transport is the combination of the two imaging techniques magnetic resonance imaging (MRI) and neutron imaging (NI). Both methods are complementary, because NI maps the total proton density, possibly amplified by NI tracers, which usually corresponds to total water content, and is able to detect changes and spatial patterns with high resolution. On the other side, nuclear magnetic resonance relaxation times reflect the interaction between fluid and matrix, while also a mapping of proton spin density and thus water content is possible. Therefore MRI is able to classify different water pools via their relaxation times additionally to the water distribution inside soil as a porous medium. We have started such combined measurements with the approach to use the same samples and perform tomography with each imaging method at different location and short-term sample transfer.

  14. Interaction of methyl bromide with soil.

    PubMed

    Tao, Ting; Maciel, Gary E

    2002-02-15

    Because methyl bromide (CH3Br) is a widely used agricultural fumigant for soil disinfection, it is important to know the chemical behavior and fate of CH3Br as a result of its use for soil treatment. A solid-state 13C NMR study of 13CH3Br-treated soil and soil-component samples shows that methylation of soil organic matter may be the major pathway for degradation of CH3Br in soils. Adsorption of CH3Br on a dried clay like Ca-montmorillonite or kaolinite does not contribute directly to the degradation of CH3Br. The results are interpreted in terms of the chemical structures of separated soil fractions and the nature of the separation procedure. PMID:11878373

  15. Micelles as Soil and Water Decontamination Agents.

    PubMed

    Shah, Afzal; Shahzad, Suniya; Munir, Azeema; Nadagouda, Mallikarjuna N; Khan, Gul Shahzada; Shams, Dilawar Farhan; Dionysiou, Dionysios D; Rana, Usman Ali

    2016-05-25

    Contaminated soil and water pose a serious threat to human health and ecosystem. For the treatment of industrial effluents or minimizing their detrimental effects, preventive and remedial approaches must be adopted prior to the occurrence of any severe environmental, health, or safety hazard. Conventional treatment methods of wastewater are insufficient, complicated, and expensive. Therefore, a method that could use environmentally friendly surfactants for the simultaneous removal of both organic and inorganic contaminants from wastewater is deemed a smart approach. Surfactants containing potential donor ligands can coordinate with metal ions, and thus such compounds can be used for the removal of toxic metals and organometallic compounds from aqueous systems. Surfactants form host-guest complexes with the hydrophobic contaminants of water and soil by a mechanism involving the encapsulation of hydrophobes into the self-assembled aggregates (micelles) of surfactants. However, because undefined amounts of surfactants may be released into the aqueous systems, attention must be paid to their own environmental risks as well. Moreover, surfactant remediation methods must be carefully analyzed in the laboratory before field implementation. The use of biosurfactants is the best choice for the removal of water toxins as such surfactants are associated with the characteristics of biodegradability, versatility, recovery, and reuse. This Review is focused on the currently employed surfactant-based soil and wastewater treatment technologies owing to their critical role in the implementation of certain solutions for controlling pollution level, which is necessary to protect human health and ensure the quality standard of the aquatic environment. PMID:27136750

  16. Interaction of Escherichia coli and Soil Particles in Runoff

    PubMed Central

    Muirhead, Richard William; Collins, Robert Peter; Bremer, Philip James

    2006-01-01

    A laboratory-scale model system was developed to investigate the transport mechanisms involved in the horizontal movement of bacteria in overland flow across saturated soils. A suspension of Escherichia coli and bromide tracer was added to the model system, and the bromide concentration and number of attached and unattached E. coli cells in the overland flow were measured over time. Analysis of the breakthrough curves indicated that the E. coli and bromide were transported together, presumably by the same mechanism. This implied that the E. coli was transported by advection with the flowing water. Overland-flow transport of E. coli could be significantly reduced if the cells were preattached to large soil particles (>45 μm). However, when unattached cells were inoculated into the system, the E. coli appeared to attach predominantly to small particles (<2 μm) and hence remained unattenuated during transport. These results imply that in runoff generated by saturation-excess conditions, bacteria are rapidly transported across the surface and have little opportunity to interact with the soil matrix. PMID:16672484

  17. Soil-Plant Nutrient Interactions on Manure-Enriched Calcareous Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Nutrient accumulations on heavily manured soils can trigger soil and plant nutrient interactions. The goal of the study was to determine the current impact of dairy manure applications on nutrient concentrations in soil and tissue for irrigated corn silage crops grown in Southern Idaho. At harvest,...

  18. Characterization of soil water content variability and soil texture using GPR groundwave techniques

    SciTech Connect

    Grote, K.; Anger, C.; Kelly, B.; Hubbard, S.; Rubin, Y.

    2010-08-15

    Accurate characterization of near-surface soil water content is vital for guiding agricultural management decisions and for reducing the potential negative environmental impacts of agriculture. Characterizing the near-surface soil water content can be difficult, as this parameter is often both spatially and temporally variable, and obtaining sufficient measurements to describe the heterogeneity can be prohibitively expensive. Understanding the spatial correlation of near-surface soil water content can help optimize data acquisition and improve understanding of the processes controlling soil water content at the field scale. In this study, ground penetrating radar (GPR) methods were used to characterize the spatial correlation of water content in a three acre field as a function of sampling depth, season, vegetation, and soil texture. GPR data were acquired with 450 MHz and 900 MHz antennas, and measurements of the GPR groundwave were used to estimate soil water content at four different times. Additional water content estimates were obtained using time domain reflectometry measurements, and soil texture measurements were also acquired. Variograms were calculated for each set of measurements, and comparison of these variograms showed that the horizontal spatial correlation was greater for deeper water content measurements than for shallower measurements. Precipitation and irrigation were both shown to increase the spatial variability of water content, while shallowly-rooted vegetation decreased the variability. Comparison of the variograms of water content and soil texture showed that soil texture generally had greater small-scale spatial correlation than water content, and that the variability of water content in deeper soil layers was more closely correlated to soil texture than were shallower water content measurements. Lastly, cross-variograms of soil texture and water content were calculated, and co-kriging of water content estimates and soil texture

  19. Evaluation and Targeting of Soil and Water Conservation Practices in the Goodwater Creek Watershed

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The objective of our research was to identify how conservation practices, their biophysical settings, and the socio/economic constraints interact to affect water quality in the Goodwater Creek Experimental Watershed. Analysis of fifteen years of flow and water quality data showed that soil and water...

  20. Experimental Test on Control Points Materialization for the Study of Vertical Movements of Soil and its Interactions with Ground Water Contents

    NASA Astrophysics Data System (ADS)

    Vittuari, L.; Gottardi, G.; Tini, M. A.

    2013-01-01

    In the study of soil vertical movements, one of the techniques most commonly used is the spirit levelling, now flanked by satellite SAR interferometry and by the analysis of time series acquired through permanent GNSS stations. The reliability of control points monuments varies depending both on the geological context and on the structure being representative of the investigated phenomenon. Often due to the high number of desired points or to the need of maintaining a specific areal distribution, they are fixed on existing structures (as in the common case of spirit levelling networks). This aspect is even more evident in the case of SAR interferometric analysis, where the permanent scatterers are identified on the basis of consistency in the radar response, but the points display movements measured by structures with different foundations at different depths. Starting from repeated precision levelling measurements, we verified which is the order of magnitude of movements of control points characterized by shallow foundations in cohesive soils, observing their behaviours at different depths, under simple and very common conditions such as the presence of periods of drought or rainfall. The results point-out movements in the order of 3-7 mm in the first meter of depth occurred in a week, during the transition between the period of summer drought and the first rains.

  1. Quantifying nonisothermal subsurface soil water evaporation

    NASA Astrophysics Data System (ADS)

    Deol, Pukhraj; Heitman, Josh; Amoozegar, Aziz; Ren, Tusheng; Horton, Robert

    2012-11-01

    Accurate quantification of energy and mass transfer during soil water evaporation is critical for improving understanding of the hydrologic cycle and for many environmental, agricultural, and engineering applications. Drying of soil under radiation boundary conditions results in formation of a dry surface layer (DSL), which is accompanied by a shift in the position of the latent heat sink from the surface to the subsurface. Detailed investigation of evaporative dynamics within this active near-surface zone has mostly been limited to modeling, with few measurements available to test models. Soil column studies were conducted to quantify nonisothermal subsurface evaporation profiles using a sensible heat balance (SHB) approach. Eleven-needle heat pulse probes were used to measure soil temperature and thermal property distributions at the millimeter scale in the near-surface soil. Depth-integrated SHB evaporation rates were compared with mass balance evaporation estimates under controlled laboratory conditions. The results show that the SHB method effectively measured total subsurface evaporation rates with only 0.01-0.03 mm h-1difference from mass balance estimates. The SHB approach also quantified millimeter-scale nonisothermal subsurface evaporation profiles over a drying event, which has not been previously possible. Thickness of the DSL was also examined using measured soil thermal conductivity distributions near the drying surface. Estimates of the DSL thickness were consistent with observed evaporation profile distributions from SHB. Estimated thickness of the DSL was further used to compute diffusive vapor flux. The diffusive vapor flux also closely matched both mass balance evaporation rates and subsurface evaporation rates estimated from SHB.

  2. Soil erosion by water - model concepts and application

    NASA Astrophysics Data System (ADS)

    Schmidt, Juergen

    2010-05-01

    Soil erosion is not a continuous process but the result of isolated surface runoff events, whose erosional effects are determined by numerous temporally and spatially varying variables. Thus the monitoring of soil loss by direct observation is extremely limited with respect to space and time. Usually observation plots cover an area of less than 100 m2 and the observation period is less than 10 years. In order to estimate soil losses by water erosion for others than empirically observable conditions, mathematical models are needed, which are able to describe the interaction of the different physical mechanisms involved either statistically or on the basis of physical algorithms. Such models are absolutely essential for risk prognoses on catchment and regional scale. Besides the aspect of soil conservation the delivery of sediments and sediment bound pollutants into surface water bodies are of increasing relevance in this context. Based on an exemplary selection of existing water erosion models this contribution aims to give an overview over different mathematical approaches used for the description of particle detachment, transport and deposition of soil particles. According to the chronology in the development of soil erosion models empirical algorithms will be presented first based on the USLE approach. However, since purely empirical models like USLE are limited to the estimation of annual soil loss further attempts in soil erosion modelling are focussed on event based estimations considering the fact that soil erosion is not a continuous process but the result of isolated runoff events. One of the first models of this type was CREAMS using physically based algorithms in combination with empirical ones in order to describe the basic erosion processes. Today there are diverse soil erosion models available following in principle the CREAMS concept but using different algorithms in detail. Concerning particle detachment, transport and deposition alternative

  3. Plant-soil interactions and soil carbon dynamics under climate extremes

    NASA Astrophysics Data System (ADS)

    Bahn, Michael

    2016-04-01

    Climate extremes have been suggested to increase significantly in intensity and frequency in the coming decades, and may influence ecosystem processes and the carbon cycle more profoundly than gradual climate warming. While there is a growing understanding of plant-soil interactions in extreme environments and from lab experiments, we still know very little about how such interactions affect soil carbon dynamics in real-world ecosystems exposed to climate extremes. In this talk I will give a brief overview of the topic and will present evidence from in-situ experiments on plant-soil interactions and their consequences for soil carbon dynamics under severe drought.

  4. Climate change impacts on soil and water conservation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A 2003 report of the Soil and Water Conservation Society concluded that changes in long-term precipitation may substantial impact runoff and soil erosion. These findings call for a review of current approaches to estimating runoff and soil erosion from agricultural lands, enhancements to soil and wa...

  5. Managing pine straw harvests to minimize soil and water losses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Pine straw is a valuable landscape mulch because it conserves soil moisture, moderates soil temperature, inhibits weed growth, and protects the soil surface against erosion, while retaining a loose structure that allows water, air, and fertilizer to easily reach the soil surface. As a result, marke...

  6. EFFECT OF SOIL AGGREGATE SIZE DISTRIBUTION ON WATER RETENTION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Quantitative information on soil water retention is in demand in hydrology, agrometeorology, agronomy, contaminant transport, and other soil-related disciplines of earth and environmental sciences. Soil aggregate composition is an important characteristic of soil structure and, as such, has been exp...

  7. Phosphorus dynamics in soils irrigated with reclaimed waste water or fresh water - A study using oxygen isotopic composition of phosphate

    USGS Publications Warehouse

    Zohar, I.; Shaviv, A.; Young, M.; Kendall, C.; Silva, S.; Paytan, A.

    2010-01-01

    Transformations of phosphate (Pi) in different soil fractions were tracked using the stable isotopic composition of oxygen in phosphate (??18Op) and Pi concentrations. Clay soil from Israel was treated with either reclaimed waste water (secondary, low grade) or with fresh water amended with a chemical fertilizer of a known isotopic signature. Changes of ??18Op and Pi within different soil fractions, during a month of incubation, elucidate biogeochemical processes in the soil, revealing the biological and the chemical transformation impacting the various P pools. P in the soil solution is affected primarily by enzymatic activity that yields isotopic equilibrium with the water molecules in the soil solution. The dissolved P interacts rapidly with the loosely bound P (extracted by bicarbonate). The oxides and mineral P fractions (extracted by NaOH and HCl, respectively), which are considered as relatively stable pools of P, also exhibited isotopic alterations in the first two weeks after P application, likely related to the activity of microbial populations associated with soil surfaces. Specifically, isotopic depletion which could result from organic P mineralization was followed by isotopic enrichment which could result from preferential biological uptake of depleted P from the mineralized pool. Similar transformations were observed in both soils although transformations related to biological activity were more pronounced in the soil treated with reclaimed waste water compared to the fertilizer treated soil. ?? 2010 Elsevier B.V.

  8. Seasonal changes in soil water repellency and their effect on soil CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Urbanek, Emilia; Qassem, Khalid

    2016-04-01

    Soil water repellency (SWR) is a seasonally variable phenomenon controlled by moisture content and at the same time a regulator of the distribution and conductivity of water in the soil. The distribution and availability of water in soil is also an important factor for microbial activity, decomposition of soil organic matter and exchange of gases like CO2 and CH4 between the soil and the atmosphere. It has been therefore hypothesised that SWR by restricting water availability in soil can affect the production and the transport of CO2 in the soil and between the soil and the atmosphere. This study investigates the effect of seasonal changes in soil moisture and water repellency on CO2 fluxes from soil. The study was conducted for 3 year at four grassland and pine forest sites in the UK with contrasting precipitation. The results show the temporal changes in soil moisture content and SWR are affected by rainfall intensity and the length of dry periods between the storms. Soils exposed to very high annual rainfall (>1200mm) can still exhibit high levels of SWR for relatively long periods of time. The spatial variation in soil moisture resulting from SWR affects soil CO2 fluxes, but the most profound effect is visible during and immediately after the rainfall events. Keywords: soil water repellency, CO2 flux, hydrophobicity, preferential flow, gas exchange, rainfall

  9. Non-destructive measurement of carbonic anhydrase activity and the oxygen isotope composition of soil water

    NASA Astrophysics Data System (ADS)

    Jones, Sam; Sauze, Joana; Ogée, Jérôme; Wohl, Steven; Bosc, Alexandre; Wingate, Lisa

    2016-04-01

    Carbonic anhydrases are a group of metalloenzymes that catalyse the hydration of aqueous carbon dioxide (CO2). The expression of carbonic anhydrase by bacteria, archaea and eukarya has been linked to a variety of important biological processes including pH regulation, substrate supply and biomineralisation. As oxygen isotopes are exchanged between CO2 and water during hydration, the presence of carbonic anhydrase in plants and soil organisms also influences the oxygen isotope budget of atmospheric CO2. Leaf and soil water pools have distinct oxygen isotope compositions, owing to differences in pool sizes and evaporation rates, which are imparted on CO2during hydration. These differences in the isotopic signature of CO2 interacting with leaves and soil can be used to partition the contribution of photosynthesis and soil respiration to net terrestrial CO2 exchange. However, this relies on our knowledge of soil carbonic anhydrase activity and currently, the prevalence and function of these enzymes in soils is poorly understood. Isotopic approaches used to estimate soil carbonic anhydrase activity typically involve the inversion of models describing the oxygen isotope composition of CO2 fluxes to solve for the apparent, potentially catalysed, rate of oxygen exchange during hydration. This requires information about the composition of CO2 in isotopic equilibrium with soil water obtained from destructive, depth-resolved soil water sampling. This can represent a significant challenge in data collection given the considerable potential for spatial and temporal variability in the isotopic composition of soil water and limited a priori information with respect to the appropriate sampling resolution and depth. We investigated whether we could circumvent this requirement by constraining carbonic anhydrase activity and the composition of soil water in isotopic equilibrium with CO2 by solving simultaneously the mass balance for two soil CO2 steady states differing only in the

  10. Subsurface And Surface Water Flow Interactions

    EPA Science Inventory

    In this chapter we present basic concepts and principles underlying the phenomena of groundwater and surface water interactions. Fundamental equations and analytical and numerical solutions describing stream-aquifer interactions are presented in hillslope and riparian aquifer en...

  11. Mucilage exudation facilitates root water uptake in dry soils

    NASA Astrophysics Data System (ADS)

    Ahmed, Mutez; Kroener, Eva; Holz, Maire; Zarebanadkouki, Mohsen; Carminati, Andrea

    2014-05-01

    As plant roots take up water and the soil dries, water depletion is expected to occur in the rhizosphere. However, recent experiments showed that the rhizosphere of lupines was wetter than the bulk soil during root water uptake. On the other hand, after irrigation the rhizosphere remained markedly dry and it rewetted only after one-two days. We hypothesize that: 1) drying/wetting rates of the rhizosphere are controlled by mucilage exuded by roots; 2) mucilage alters the soil hydraulic conductivity: in particular, wet mucilage increases the soil hydraulic conductivity and dry mucilage makes the soil water repellent; 3) mucilage exudation favors root water uptake in dry soil; and 4) dry mucilage limits water loss from roots to dry soils. We used a root pressure probe to measure the hydraulic conductance of artificial roots sitting in soils. As an artificial root we employed a suction cup with a diameter of 2 mm and a length of 45 mm. The root pressure probe gave the hydraulic conductance of the soil-root continuum during pulse experiments in which water was injected into or sucked from the soil. First, we performed experiments with roots in a relatively dry soil with a volumetric water content of 0.03. Then, we repeated the experiment with artificial roots covered with mucilage and then placed into the soil. As a model for mucilage, we collected mucilage from Chia seeds. The water contents (including that of mucilage) in the experiments with and without mucilage were equal. The pressure curves were fitted with a model of root water that includes rhizosphere dynamics. We found that the artificial roots covered with wet mucilage took up water more easily. In a second experimental set-up we measured the outflow of water from the artificial roots into dry soils. We compared two soils: 1) a sandy soil and 2) the same soil wetted with mucilage from Chia seeds and then let dry. The latter soil became water repellent. Due to the water repellency, the outflow of water from

  12. Determining the least limiting water range using limited soil data

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The Least Limiting Water Range (LLWR) is a useful tool to evaluate changes in soil physical condition caused by changing soil management. It incorporates limitations to plant growth based on limiting aeration, water holding capacity and soil strength. A disadvantage of the LLWR is the need to determ...

  13. Soil Water Trends During the 2005 - 2006 Drought in Oklahoma

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water depletion is an early consequence of a meteorological drought, with the latter defined as a precipitation deficit lasting a few months to several years. Soil water in the upper soil profile (approximately first meter) is limited and highly variable because of its rapid response to precipi...

  14. Ecohydrology of root zone water fluxes and soil development in complex semiarid rangelands

    NASA Astrophysics Data System (ADS)

    Gutiérrez-Jurado, Hugo A.; Vivoni, Enrique R.; Harrison, J. Bruce J.; Guan, Huade

    2006-10-01

    In semiarid complex terrain, the landscape creates spatial niches for different types of vegetation through the effects of aspect, slope and curvature on the water and energy balance at the soil surface. The ecohydrology of rangelands is defined by the interaction of soils, plants and climate occurring on a topographic surface. While these interactions have been studied for subtle terrain, little is known about the controls exerted by terrain position, in particular terrain aspect, on ecosystem processes. Furthermore, differential plant establishment can lead to measurable differences in rates of soil development, which in turn can affect soil hydraulic properties and the surface water balance. In this study, we outline the physical mechanisms affecting plant establishment, soil development and hydrologic fluxes in semiarid complex terrain. We illustrate the interactions between vegetation, root zone water fluxes and soil development using, as an example, a small drainage basin in the Sevilleta National Wildlife Refuge (SNWR), New Mexico. In the study basin, opposing hillslopes are characterized by marked differences in ecosystem composition and soil profile properties, with the north-facing hillslope dominated by one seed juniper (Juniperus monosperma) and the south-facing slope consisting of creosote bush (Larrea tridentata). We assess the effect of terrain aspect on root zone hydrologic fluxes and soil development in the two ecosystems by using soil observations, hydraulic properties from pedotransfer functions (PTFs), and numerical modelling of vadose zone fluxes. Modelling results show marked differences in root zone fluxes in the north-facing juniper and south-facing creosote ecosystems. Differences in the amplitude and frequency of soil water content and pressure correspond to changes in soil profile and vegetation characteristics. For example, soil properties of the calcium carbonate (CaCO3) horizons and differential plant water uptake impact the simulated

  15. Measuring and modelling water related soil-vegetation feedbacks in a fallow plot

    NASA Astrophysics Data System (ADS)

    Ursino, N.; Cassiani, G.; Deiana, R.; Vignoli, G.; Boaga, J.

    2013-08-01

    Land fallowing is one possible response to shortage of water for irrigation. Leaving the soil unseeded implies a change of the soil functioning that has an impact on the water cycle. The development of a soil crust in the open spaces between the patterns of grass weed affects the soil properties and the field scale water balance. The objectives of this study are to test the potential of integrated non invasive geophysical methods and ground-image analysis and to quantify the effect of the soil vegetation interaction on the water balance of a fallow land at the local and plot scale. We measured repeatedly in space and time local soil saturation and vegetation cover over two small plots located in southern Sardinia, Italy, during a controlled irrigation experiment. One plot was left unseeded and the other was cultivated. The comparative analysis of ERT maps of soil moisture evidenced a considerably different hydrologic response to irrigation of the two plots. Local measurements of soil saturation and vegetation cover were repeated in space to evidence a positive feedback between weed growth and infiltration at the fallow plot. A simple bucket model captured the different soil moisture dynamics at the two plots during the infiltration experiment and was used to estimate the impact of the soil vegetation feedback on the yearly water balance at the fallow site.

  16. Diurnal fluctuations of water and heat flows in a bare soil

    NASA Astrophysics Data System (ADS)

    Schelde, K.; Thomsen, A.; Heidmann, T.; SchjøNning, P.; Jansson, P.-E.

    1998-11-01

    The complexity of coupled transport of heat and moisture at the soil surface necessitates a combination of field and numerical experiments to evaluate the interactions between liquid and vapor phase flow. The near-surface moisture and temperature conditions of a bare soil were investigated experimentally and by using the SOIL model to assess the importance of water vapor flow. During a 1-month period in early fall, intensive measurements of water content, water tension, and temperature were made in a bare soil plot. Soil thermal conductivity, measured on soil cores extracted for laboratory analysis, was found to agree with estimates based on the Kersten equation. Simulated water content and soil temperature agreed well with observations. Modeled soil vapor flow was significant compared to liquid flow only during the initial dry days when the inclusion of vapor flow improved the predicted diurnal variation in water tension. Model predictions were sensitive to an accurate representation of the soil surface energy balance, including the consideration of steep gradients in tension near the soil surface, and to the enhancement of vapor flow.

  17. Measuring and modeling water-related soil-vegetation feedbacks in a fallow plot

    NASA Astrophysics Data System (ADS)

    Ursino, N.; Cassiani, G.; Deiana, R.; Vignoli, G.; Boaga, J.

    2014-03-01

    Land fallowing is one possible response to shortage of water for irrigation. Leaving the soil unseeded implies a change of the soil functioning that has an impact on the water cycle. The development of a soil crust in the open spaces between the patterns of grass weed affects the soil properties and the field-scale water balance. The objectives of this study are to test the potential of integrated non-invasive geophysical methods and ground-image analysis and to quantify the effect of the soil-vegetation interaction on the water balance of fallow land at the local- and plot scale. We measured repeatedly in space and time local soil saturation and vegetation cover over two small plots located in southern Sardinia, Italy, during a controlled irrigation experiment. One plot was left unseeded and the other was cultivated. The comparative analysis of ERT maps of soil moisture evidenced a considerably different hydrologic response to irrigation of the two plots. Local measurements of soil saturation and vegetation cover were repeated in space to evidence a positive feedback between weed growth and infiltration at the fallow plot. A simple bucket model captured the different soil moisture dynamics at the two plots during the infiltration experiment and was used to estimate the impact of the soil vegetation feedback on the yearly water balance at the fallow site.

  18. Determination of Martian soil mineralogy and water content using the Thermal Analyzer for Planetary Soils (TAPS)

    NASA Technical Reports Server (NTRS)

    Gooding, James L.; Ming, Douglas W.; Allton, Judith H.; Byers, Terry B.; Dunn, Robert P.; Gibbons, Frank L.; Pate, Daniel B.; Polette, Thomas M.

    1992-01-01

    Physical and chemical interactions between the surface and atmosphere of Mars can be expected to embody a strong cause-and-effect relationship with the minerals comprising the martian regolith. Many of the minerals in soils and sediments are probably products of chemical weathering (involving surface/atmosphere or surface/hydrosphere reactions) that could be expected to subsequently influence the sorption of atmospheric gases and water vapor. Therefore, identification of the minerals in martian surface soils and sediments is essential for understanding both past and present interactions between the Mars surface and atmosphere. Clearly, the most definitive mineral analyses would be achieved with well-preserved samples returned to Earth-based laboratories. In advance of a Mars sample return mission, however, significant progress could be made with in situ experiments that fill current voids in knowledge about the presence or abundance of key soil minerals such as clays (layered-structured silicates), zeolites, and various salts, including carbonates. TAPS is intended to answer that challenge by providing first-order identification of soil and sediment minerals.

  19. Soil Water Thermodynamic to Unify Water Retention Curve by Pressure Plates and Tensiometer

    NASA Astrophysics Data System (ADS)

    Braudeau, Erik; Hovhannissian, Gaghik; Assi, Amjad; Mohtar, Rabi

    2014-10-01

    The pressure plate method is a standard method for measuring the pF curves, also called soil water retention curves, in a large soil moisture range from saturation to a dry state corresponding to a tension pressure of near 1500 kPa. However, the pressure plate can only provide discrete water retention curves represented by a dozen measured points. In contrast, the measurement of the soil water retention curves by tensiometer is direct and continuous, but limited to the range of the tensiometer reading: from saturation to near 70-80 kPa. The two methods stem from two very different concepts of measurement and the compatibility of both methods has never been demonstrated. The recently established thermodynamic formulation of the pedostructure water retention curve, will allow the compatibility of the two curves to be studied, both theoretically and experimentally. This constitutes the object of the present article. We found that the pressure plate method provides accurate measurement points of the pedostructure water retention curve h(W), conceptually the same as that accurately measured by the tensiometer. However, contrarily to what is usually thought, h is not equal to the applied air pressure on the sample, but rather, is proportional to its logarithm, in agreement with the thermodynamic theory developed in the article. The pF curve and soil water retention curve, as well as their methods of measurement are unified in a same physical theory. It is the theory of the soil medium organization (pedostructure) and its interaction with water. We show also how the hydrostructural parameters of the theoretical curve equation can be estimated from any measured curve, whatever the method of measurement. An application example using published pF curves is given.

  20. Soil management systems to improve water availability for plants

    NASA Astrophysics Data System (ADS)

    Klik, A.; Rosner, J.

    2009-04-01

    Due to climate change it is expected that the air temperature will increase and the amount as well as the variability of rainfall will change drastically within this century. Higher temperatures and fewer rainy days with more extreme events will increase the risk of surface runoff and erosion. This will lead to reduced soil water storage and therefore to a lower water use efficiency of plants. Soil and land management systems need to be applied and adapted to improve the amount of water stored in the soil and to ensure crop productivity functions of soils under changing climatic conditions. In a 14-yr. long field experiment, the effects of three soil management systems have been studied at three sites in Austria with respect to surface runoff, soil erosion, losses of nutrients and pesticides. Eight years after beginning of the project soil samples have been taken from different depth throughout the root zone to investigate the effects on soil properties. The results show that soil management systems with reduced tillage intensity are able to improve infiltration and soil water storage. More soil water enables plant development during longer dry periods and decreases amounts of irrigation. Overall, the higher water retention in the landscape improves the regional water balance and reduces environmental problems like soil erosion and nutrient and pesticide losses

  1. Importance of soil-water relation in assessment endpoint in bioremediated soils: Plant growth and soil physical properties

    SciTech Connect

    Li, X.; Sawatsky, N.

    1995-12-31

    Much effort has been focused on defining the end-point of bioremediated soils by chemical analysis (Alberta Tier 1 or CCME Guideline for Contaminated Soils) or toxicity tests. However, these tests do not completely assess the soil quality, or the capability of soil to support plant growth after bioremediation. This study compared barley (Hordeum vulgare) growth on: (i) non-contaminated, agricultural topsoil, (2) oil-contaminated soil (4% total extractable hydrocarbons, or TEH), and (3) oil-contaminated soil treated by bioremediation (< 2% TEH). Soil physical properties including water retention, water uptake, and water repellence were measured. The results indicated that the growth of barley was significantly reduced by oil-contamination of agricultural topsoil. Furthermore, bioremediation did not improve the barley yield. The lack of effects from bioremediation was attributed to development of water repellence in hydrocarbon contaminated soils. There seemed to be a critical water content around 18% to 20% in contaminated soils. Above this value the water uptake by contaminated soil was near that of the agricultural topsoil. For lower water contents, there was a strong divergence in sorptivity between contaminated and agricultural topsoil. For these soils, water availability was likely the single most important parameter controlling plant growth. This parameter should be considered in assessing endpoint of bioremediation for hydrocarbon contaminated soils.

  2. REGIONAL SOIL WATER RETENTION IN THE CONTIGUOUS US: SOURCES OF VARIABILITY AND VOLCANIC SOIL EFFECTS

    EPA Science Inventory

    Water retention of mineral soil is often well predicted using algorithms (pedotransfer functions) with basic soil properties but the spatial variability of these properties has not been well characterized. A further source of uncertainty is that water retention by volcanic soils...

  3. Improving Soil-Vegetation Dynamics in the Soil and Water Assessment Tool (SWAT)

    NASA Astrophysics Data System (ADS)

    Ou, G.; Munoz-Arriola, F.; Chen, X.; Kilic, A.

    2014-12-01

    A non-iterative 1D Richard's equation model is developed and implemented in the Soil and Water Assessment Tool (SWAT) to improve the physical representation of soil-water-vegetation dynamics. SWAT's improved version (UN-SWAT) explicitly represents infiltration, soil evaporation, unsaturated water flow, root water update, and lateral drainage. Water-exchanges across the surface-subsurface and unsaturated-saturated zone interfaces are defined as the system's dependent top and bottom boundaries of the soil profile, respectively. In the continuum from the land surface to the aquifer, the top boundary of the soil profile accounts for non-ponding or ponding infiltration, as well as atmosphere-controlled or soil-controlled evaporation. Vegetation's root water update and lateral drainage are represented as sink terms in each soil layer. The soil profile is discretized by a variable number of computational nodes of the soil profile, whose bottom position is determined based on the groundwater table. UN-SWAT validation is performed by a single-HRU and a multi-HRU simulations in the Little Washita River Experimental Watershed in Oklahoma. Results prove that UN-SWAT's performance simulating the soil water movement in both space and time under complex conditions agree observed soil moisture and stream discharge data. UN-SWAT represents an improvement over other hydrologic models by providing a more accurate solution to the soil-water-vegetation model and accounting for the dynamics of climate and groundwater conditions.

  4. Interactive biotic and abiotic regulators of soil carbon cycling: evidence from controlled climate experiments on peatland and boreal soils.

    PubMed

    Briones, María Jesús I; McNamara, Niall P; Poskitt, Jan; Crow, Susan E; Ostle, Nicholas J

    2014-09-01

    Partially decomposed plant and animal remains have been accumulating in organic soils (i.e. >40% C content) for millennia, making them the largest terrestrial carbon store. There is growing concern that, in a warming world, soil biotic processing will accelerate and release greenhouse gases that further exacerbate climate change. However, the magnitude of this response remains uncertain as the constraints are abiotic, biotic and interactive. Here, we examined the influence of resource quality and biological activity on the temperature sensitivity of soil respiration under different soil moisture regimes. Organic soils were sampled from 13 boreal and peatland ecosystems located in the United Kingdom, Ireland, Spain, Finland and Sweden, representing a natural resource quality range of C, N and P. They were incubated at four temperatures (4, 10, 15 and 20 °C) at either 60% or 100% water holding capacity (WHC). Our results showed that chemical and biological properties play an important role in determining soil respiration responses to temperature and moisture changes. High soil C : P and C : N ratios were symptomatic of slow C turnover and long-term C accumulation. In boreal soils, low bacterial to fungal ratios were related to greater temperature sensitivity of respiration, which was amplified in drier conditions. This contrasted with peatland soils which were dominated by bacterial communities and enchytraeid grazing, resulting in a more rapid C turnover under warmer and wetter conditions. The unexpected acceleration of C mineralization under high moisture contents was possibly linked to the primarily role of fermented organic matter, instead of oxygen, in mediating microbial decomposition. We conclude that to improve C model simulations of soil respiration, a better resolution of the interactions occurring between climate, resource quality and the decomposer community will be required. PMID:24687903

  5. WATER AS A REAGENT FOR SOIL REMEDIATION

    SciTech Connect

    Indira S. Jayaweera; Montserrat Marti-Perez; Jordi Diaz-Ferrero; Angel Sanjurjo

    2001-03-29

    SRI International is conducting experiments to develop and evaluate hydrothermal extraction technology or hot water extraction (HWE) technology for remediating petroleum-contaminated soils. Most current remediation practices either fail to remove the polycyclic aromatic hydrocarbons (PAHs) found in petroleum-contaminated sites, are too costly, or require the use of organic solvents at the expense of additional contamination and with the added cost of recycling solvents. Hydrothermal extraction offers the promise of efficiently extracting PAHs and other kinds of organics from contaminated soils at moderate temperatures and pressures, using only water and inorganic salts such as carbonate. SRI has conducted experiments to measure the solubility and rate of solubilization of selected PAHs (fluoranthene, pyrene, chrysene, 9,10-dimethylanthracene) in water using SRI's hydrothermal optical cell with the addition of varying amounts of sodium carbonate to evaluate the efficiency of the technology for removing PAHs from the soil. SRI data shows a very rapid increase in solubility of PAHs with increase in temperature in the range 25-275 C. SRI also measured the rate of solubilization, which is a key factor in determining the reactor parameters. SRI results for fluoranthene, pyrene, chrysene, and 9,10-dimethylanthracene show a linear relationship between rate of solubilization and equilibrium solubility. Also, we have found the rate of solubilization of pyrene at 275 C to be 6.5 ppm/s, indicating that the equilibrium solubilization will be reached in less than 3 min at 275 C; equilibrium solubility of pyrene at 275 C is 1000 ppm. Also, pyrene and fluoranthene appear to have higher solubilities in the presence of sodium carbonate. In addition to this study, SRI studied the rate of removal of selected PAHs from spiked samples under varying conditions (temperature, pore sizes, and pH). We have found a higher removal of PAHs in the presence of sodium carbonate in both sand and

  6. Global distribution of plant-extractable water capacity of soil

    USGS Publications Warehouse

    Dunne, K.A.; Willmott, C.J.

    1996-01-01

    Plant-extractable water capacity of soil is the amount of water that can be extracted from the soil to fulfill evapotranspiration demands. It is often assumed to be spatially invariant in large-scale computations of the soil-water balance. Empirical evidence, however, suggests that this assumption is incorrect. In this paper, we estimate the global distribution of the plant-extractable water capacity of soil. A representative soil profile, characterized by horizon (layer) particle size data and thickness, was created for each soil unit mapped by FAO (Food and Agriculture Organization of the United Nations)/Unesco. Soil organic matter was estimated empirically from climate data. Plant rooting depths and ground coverages were obtained from a vegetation characteristic data set. At each 0.5?? ?? 0.5?? grid cell where vegetation is present, unit available water capacity (cm water per cm soil) was estimated from the sand, clay, and organic content of each profile horizon, and integrated over horizon thickness. Summation of the integrated values over the lesser of profile depth and root depth produced an estimate of the plant-extractable water capacity of soil. The global average of the estimated plant-extractable water capacities of soil is 8??6 cm (Greenland, Antarctica and bare soil areas excluded). Estimates are less than 5, 10 and 15 cm - over approximately 30, 60, and 89 per cent of the area, respectively. Estimates reflect the combined effects of soil texture, soil organic content, and plant root depth or profile depth. The most influential and uncertain parameter is the depth over which the plant-extractable water capacity of soil is computed, which is usually limited by root depth. Soil texture exerts a lesser, but still substantial, influence. Organic content, except where concentrations are very high, has relatively little effect.

  7. Root anatomical phenes associated with water acquisition from drying soil: targets for crop improvement.

    PubMed

    Lynch, Jonathan P; Chimungu, Joseph G; Brown, Kathleen M

    2014-11-01

    Several root anatomical phenes affect water acquisition from drying soil, and may therefore have utility in breeding more drought-tolerant crops. Anatomical phenes that reduce the metabolic cost of the root cortex ('cortical burden') improve soil exploration and therefore water acquisition from drying soil. The best evidence for this is for root cortical aerenchyma; cortical cell file number and cortical senescence may also be useful in this context. Variation in the number and diameter of xylem vessels strongly affects axial water conductance. Reduced axial conductance may be useful in conserving soil water so that a crop may complete its life cycle under terminal drought. Variation in the suberization and lignification of the endodermis and exodermis affects radial water conductance, and may therefore be important in reducing water loss from mature roots into dry soil. Rhizosheaths may protect the water status of young root tissue. Root hairs and larger diameter root tips improve root penetration of hard, drying soil. Many of these phenes show substantial genotypic variation. The utility of these phenes for water acquisition has only rarely been validated, and may have strong interactions with the spatiotemporal dynamics of soil water availability, and with root architecture and other aspects of the root phenotype. This complexity calls for structural-functional plant modelling and 3D imaging methods. Root anatomical phenes represent a promising yet underexplored and untapped source of crop breeding targets. PMID:24759880

  8. Soil formation in post mining sites: the role of vegatation soil microflora and fauna interactions

    NASA Astrophysics Data System (ADS)

    Frouz, J.

    2009-04-01

    The role of vegetation and soil micro flora and fauna interaction during soil formation was studied in post mining sites in Czech Republic, Germany and USA. Vegetation and character of substrate substantially effect, micro flora, namely fungal bacterial ration, fauna composition and resulting microstructure of soil. Plants that bring more nitrogen in to the system support larger biomass of soil fauna and namely occurrence of earthworms which yield in larger bioturbation and associated faster production of A horizon in newly developing soil. Manipulation experiment show that presence of fauna have crucial effect of soil formation in these soil and positive effect of many plant species which are assumed to beneficial for reclamation is in fact indirect and caused by its positive effect on soil fauna development.

  9. Interactions between soil thermal and hydrological dynamics in the response of Alaska ecosystems to fire disturbance

    USGS Publications Warehouse

    Yi, S.; McGuire, A.D.; Harden, J.; Kasischke, E.; Manies, K.; Hinzman, L.; Liljedahl, A.; Randerson, J.; Liu, H.; Romanovsky, V.; Marchenko, S.; Kim, Y.

    2009-01-01

    Soil temperature and moisture are important factors that control many ecosystem processes. However, interactions between soil thermal and hydrological processes are not adequately understood in cold regions, where the frozen soil, fire disturbance, and soil drainage play important roles in controlling interactions among these processes. These interactions were investigated with a new ecosystem model framework, the dynamic organic soil version of the Terrestrial Ecosystem Model, that incorporates an efficient and stable numerical scheme for simulating soil thermal and hydrological dynamics within soil profiles that contain a live moss horizon, fibrous and amorphous organic horizons, and mineral soil horizons. The performance of the model was evaluated for a tundra burn site that had both preburn and postbura measurements, two black spruce fire chronosequences (representing space-for-time substitutions in well and intermediately drained conditions), and a poorly drained black spruce site. Although space-for-time substitutions present challenges in modeldata comparison, the model demonstrates substantial ability in simulating the dynamics of ??vapotranspiration, soil temperature, active layer depth, soil moisture, and water table depth in response to both climate variability and fire disturbance. Several differences between model simulations and field measurements identified key challenges for evaluating/improving model performance that include (1) proper representation of discrepancies between air temperature and ground surface temperature; (2) minimization of precipitation biases in the driving data sets; (3) improvement of the measurement accuracy of soil moisture in surface organic horizons; and (4) proper specification of organic horizon depth/properties, and soil thermal conductivity. Copyright 2009 by the American Geophysical Union.

  10. Hydrologic modeling of soil water storage in landfill cover systems

    SciTech Connect

    Barnes, F.J.; Rodgers, J.C.

    1987-01-01

    The accuracy of modeling soil water storage by two hydrologic models, CREAMS and HELP, was tested by comparing simulation results with field measurements of soil moisture in eight experimental landfill cover systems having a range of well-defined soil profiles and vegetative covers. Regression analysis showed that CREAMS generally represented soil moisture more accurately than HELP simulations. Soil profiles that more closely resembled natural agricultural soils were more accurately modeled than highly artificial layered soil profiles. Precautions for determining parameter values for model input and for interpreting simulation results are discussed.

  11. Monitoring soil-vegetation interactions using non-invasive geophysical techniques

    NASA Astrophysics Data System (ADS)

    Perri, M.; Cassiani, G.; Boaga, J.; Rossi, M.; Vignoli, G.; Deiana, R.; Ursino, N.; Putti, M.; Majone, B.; Bellin, A.; Blaschek, M.; Duttmann, R.; Meyer, S.; Ludwig, R.; Soddu, A.; Dietrich, P.; Werban, U.

    2012-12-01

    The understanding of soil-vegetation-atmosphere interactions is of utmost importance in the solution of a number of hydrological questions and practical issues, including flood control, agricultural best practice, slope stability and impacts of climatic changes. Geophysical time-lapse monitoring can greatly contribute to the understanding of these interactions particularly for its capability to map in space and time the effects of vegetation on soil moisture content. In this work we present the results of two case studies showing the potential of hydro-geophysics in this context. The first example refers to the long term monitoring of the soil static and dynamic characteristics in an experimental site located in Sardinia (Italy). The main objective of this study is to understand the effects of soil - water - plants interactions on soil water balance. A combination of time-lapse electromagnetic induction (EMI) monitoring over wide areas and localized irrigation tests monitored by electrical resistivity tomography (ERT) and TDR soil moisture measurements is here used, in order to achieve quantitative field-scale estimates of moisture content from topsoil layer. Natural gamma-ray emission mapping, texture analysis and laboratory calibration of an electrical constitutive relationship on soil samples complete the dataset. We therefore observed that the growth of vegetation, with the associated below ground allocation of biomass, has a significant impact on the soil moisture dynamics. In particular vegetation extracts a large amount of water from the soil in the hot season, but it also reduces evaporation by shadowing the soil surface. In addition, vegetation enhances the soil wetting process as the root system facilitates water infiltration, thus creating a positive feedback system. The second example regards the time-lapse monitoring of soil moisture content in an apple orchard located in the Alpine region of Northern Italy (Trento). A three-dimensional cross-hole ERT

  12. Semiempirical model of soil water hysteresis

    USGS Publications Warehouse

    Nimmo, J.R.

    1992-01-01

    In order to represent hysteretic soil water retention curves accurately using as few measurements as possible, a new semiempirical model has been developed. It has two postulates related to physical characteristics of the medium, and two parameters, each with a definite physical interpretation, whose values are determined empirically for a given porous medium. Tests of the model show that it provides high-quality optimized fits to measured water content vs. matric pressure wetting curves for a wide variety of media. A practical use of this model is to provide a complete simulated main wetting curve for a medium where only a main drying curve and two points on the wetting curve have been measured. -from Author

  13. STABLE ISOTOPES AS INDICATORS OF SOIL WATER DYNAMICS IN WATERSHEDS

    EPA Science Inventory

    Stream water quality and quantity depend on discharge rates of water and nutrients from soils. However, soil-water storage is very dynamic and strongly influenced by plants. We analyzed stable isotopes of oxygen and hydrogen to quantify spatial and temporal changes in evaporati...

  14. Can surfactants affect management of non-water repellent soils?

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surfactants affect the water relations of water repellent soils but may or may not affect those of wettable soils. We studied the effects of three surfactants, Aquatrols IrrigAid Gold®, an ethylene oxide/propylene oxide block copolymer, and an alkyl polyglycoside, along with untreated tap water as ...

  15. Soil water sensor response to bulk electrical conductivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water monitoring using electromagnetic (EM) sensors can facilitate observations of water content at high temporal and spatial resolutions. These sensors measure soil dielectric permittivity (Ka) which is largely a function of volumetric water content. However, bulk electrical conductivity BEC c...

  16. Interaction of water with epoxy.

    SciTech Connect

    Powers, Dana Auburn

    2009-07-01

    The chemistries of reactants, plasticizers, solvents and additives in an epoxy paint are discussed. Polyamide additives may play an important role in the absorption of molecular iodine by epoxy paints. It is recommended that the unsaturation of the polyamide additive in the epoxy cure be determined. Experimental studies of water absorption by epoxy resins are discussed. These studies show that absorption can disrupt hydrogen bonds among segments of the polymers and cause swelling of the polymer. The water absorption increases the diffusion coefficient of water within the polymer. Permanent damage to the polymer can result if water causes hydrolysis of ether linkages. Water desorption studies are recommended to ascertain how water absorption affects epoxy paint.

  17. Reflectance of vegetation, soil, and water

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L. (Principal Investigator)

    1973-01-01

    The author has identified the following significant results. The ability to read the 24-channel MSS CCT tapes, select specified agricultural land use areas from the CCT, and perform multivariate statistical and pattern recognition analyses has been demonstrated. The 5 optimum channels chosen for classifying an agricultural scene were, in the order of their selection the far red visible, short reflective IR, visible blue, thermal infrared, and ultraviolet portions of the electromagnetic spectrum, respectively. Although chosen by a training set containing only vegetal categories, the optimum 4 channels discriminated pavement, water, bare soil, and building roofs, as well as the vegetal categories. Among the vegetal categories, sugar cane and cotton had distinctive signatures that distinguished them from grass and citrus. Acreages estimated spectrally by the computer for the test scene were acceptably close to acreages estimated from aerial photographs for cotton, sugar cane, and water. Many nonfarmable land resolution elements representing drainage ditch, field road, and highway right-of-way as well as farm headquarters area fell into the grass, bare soil plus weeds, and citrus categories and lessened the accuracy of the farmable acreage estimates in these categories. The expertise developed using the 24-channel data will be applied to the ERTS-1 data.

  18. Soil CO₂ dynamics in a tree island soil of the Pantanal: the role of soil water potential.

    PubMed

    Johnson, Mark S; Couto, Eduardo Guimarães; Pinto, Osvaldo B; Milesi, Juliana; Santos Amorim, Ricardo S; Messias, Indira A M; Biudes, Marcelo Sacardi

    2013-01-01

    The Pantanal is a biodiversity hotspot comprised of a mosaic of landforms that differ in vegetative assemblages and flooding dynamics. Tree islands provide refuge for terrestrial fauna during the flooding period and are particularly important to the regional ecosystem structure. Little soil CO₂ research has been conducted in this region. We evaluated soil CO₂ dynamics in relation to primary controlling environmental parameters (soil temperature and soil water). Soil respiration was computed using the gradient method using in situ infrared gas analyzers to directly measure CO₂ concentration within the soil profile. Due to the cost of the sensors and associated equipment, this study was unreplicated. Rather, we focus on the temporal relationships between soil CO₂ efflux and related environmental parameters. Soil CO₂ efflux during the study averaged 3.53 µmol CO₂ m⁻² s⁻¹, and was equivalent to an annual soil respiration of 1220 g C m⁻² y⁻¹. This efflux value, integrated over a year, is comparable to soil C stocks for 0-20 cm. Soil water potential was the measured parameter most strongly associated with soil CO₂ concentrations, with high CO₂ values observed only once soil water potential at the 10 cm depth approached zero. This relationship was exhibited across a spectrum of timescales and was found to be significant at a daily timescale across all seasons using conditional nonparametric spectral Granger causality analysis. Hydrology plays a significant role in controlling CO₂ efflux from the tree island soil, with soil CO₂ dynamics differing by wetting mechanism. During the wet-up period, direct precipitation infiltrates soil from above and results in pulses of CO₂ efflux from soil. The annual flood arrives later, and saturates soil from below. While CO₂ concentrations in soil grew very high under both wetting mechanisms, the change in soil CO₂ efflux was only significant when soils were wet from above. PMID:23762259

  19. Soil CO2 Dynamics in a Tree Island Soil of the Pantanal: The Role of Soil Water Potential

    PubMed Central

    Johnson, Mark S.; Couto, Eduardo Guimarães; Pinto Jr, Osvaldo B.; Milesi, Juliana; Santos Amorim, Ricardo S.; Messias, Indira A. M.; Biudes, Marcelo Sacardi

    2013-01-01

    The Pantanal is a biodiversity hotspot comprised of a mosaic of landforms that differ in vegetative assemblages and flooding dynamics. Tree islands provide refuge for terrestrial fauna during the flooding period and are particularly important to the regional ecosystem structure. Little soil CO2 research has been conducted in this region. We evaluated soil CO2 dynamics in relation to primary controlling environmental parameters (soil temperature and soil water). Soil respiration was computed using the gradient method using in situ infrared gas analyzers to directly measure CO2 concentration within the soil profile. Due to the cost of the sensors and associated equipment, this study was unreplicated. Rather, we focus on the temporal relationships between soil CO2 efflux and related environmental parameters. Soil CO2 efflux during the study averaged 3.53 µmol CO2 m−2 s−1, and was equivalent to an annual soil respiration of 1220 g C m−2 y−1. This efflux value, integrated over a year, is comparable to soil C stocks for 0–20 cm. Soil water potential was the measured parameter most strongly associated with soil CO2 concentrations, with high CO2 values observed only once soil water potential at the 10 cm depth approached zero. This relationship was exhibited across a spectrum of timescales and was found to be significant at a daily timescale across all seasons using conditional nonparametric spectral Granger causality analysis. Hydrology plays a significant role in controlling CO2 efflux from the tree island soil, with soil CO2 dynamics differing by wetting mechanism. During the wet-up period, direct precipitation infiltrates soil from above and results in pulses of CO2 efflux from soil. The annual flood arrives later, and saturates soil from below. While CO2 concentrations in soil grew very high under both wetting mechanisms, the change in soil CO2 efflux was only significant when soils were wet from above. PMID:23762259

  20. Interaction of potassium phosphonate fungicide in laterite soil.

    PubMed

    Kumar, R Anil; Velayudhan, K T; Vasu, K; Ramachandran, V; Bhai, R Susheela; Unnikrishnan, G

    2005-10-01

    Potassium phosphonate is a fungicide widely used to control Phytophthora fungi species in many crops all over the world. In this paper, an attempt has been made to study the interaction of potassium phosphonate with soil under varying pH and calcium level. Several reports available in literature indicate that the phosphonate in organic form adsorb strongly on almost all mineral surfaces and natural materials like soil and sediments. The present study conducted on laterite soil of Kerala using 2 mm sieved sample indicated that phosphonate obeys Freundlich adsorption isotherm. Though at lower concentrations, Langmuir model equally fits well, deviation was observed at higher concentrations. pH and calcium content of the soil had striking influence on the interaction of the chemical with the soil. The calcium source also appeared to influence the adsorption phenomenon. Since potassium phosphonate is extensively used to control Phytophthora fungi species in black pepper (Piper nigrum) plantations in India and liming is a standard practice followed as soil amendment in acid soils to increase the soil pH, this study may help to maintain good soil quality. PMID:17051913

  1. [Impact of biological soil crusts on soil water repellence in the hilly Loess Plateau region, China].

    PubMed

    Zhang, Pei-Pei; Zhao, Yun-Ge; Wang, Yuan; Yao, Chun-Zhu

    2014-03-01

    By using water drop penetration time (WDPT) and molarity of ethanol droplet (MED) methods, the soil water repellence of undisturbed biological soil crusts (biocrusts) in five successional stages, from the hilly Loess Plateau region of China was tested. The five stages of biocrusts were light cyanobacterial crust, dark cyanobacterial crust, cyanobacterial with sparse moss crust, moss and tiny cyanobacteria patches crust and moss dominated crust. The results showed that 1) the soil water repellence was markedly increased both in the intensity and persistence since the formation of biocrusts. 2) The soil water repellence showed a decrease trend along with the successional stages of biocrusts. The soil water repellence of the biocrusts with the moss coverage above 20% was significantly lower than that of the cyanobacterial crusts. 3) The soil water repellence of the biocrusts was closely related to soil moisture and the dominant organism. The soil water repellence increased with the decrease of soil water content for the moss dominated biocrusts, while changed in a bimodal curve with the decrease of soil water content for the cyanobacterial biocrusts. PMID:24984480

  2. A fragrant neighborhood: volatile mediated bacterial interactions in soil

    PubMed Central

    Schulz-Bohm, Kristin; Zweers, Hans; de Boer, Wietse; Garbeva, Paolina

    2015-01-01

    There is increasing evidence that volatile organic compounds (VOCs) play essential roles in communication and competition between soil microorganisms. Here we assessed volatile-mediated interactions of a synthetic microbial community in a model system that mimics the natural conditions in the heterogeneous soil environment along the rhizosphere. Phylogenetic different soil bacterial isolates (Burkholderia sp., Dyella sp., Janthinobacterium sp., Pseudomonas sp., and Paenibacillus sp.) were inoculated as mixtures or monoculture in organic-poor, sandy soil containing artificial root exudates (ARE) and the volatile profile and growth were analyzed. Additionally, a two-compartment system was used to test if volatiles produced by inter-specific interactions in the rhizosphere can stimulate the activity of starving bacteria in the surrounding, nutrient-depleted soil. The obtained results revealed that both microbial interactions and shifts in microbial community composition had a strong effect on the volatile emission. Interestingly, the presence of a slow-growing, low abundant Paenibacillus strain significantly affected the volatile production by the other abundant members of the bacterial community as well as the growth of the interacting strains. Furthermore, volatiles released by mixtures of root-exudates consuming bacteria stimulated the activity and growth of starved bacteria. Besides growth stimulation, also an inhibition in growth was observed for starving bacteria exposed to microbial volatiles. The current work suggests that volatiles produced during microbial interactions in the rhizosphere have a significant long distance effect on microorganisms in the surrounding, nutrient-depleted soil. PMID:26579111

  3. A fragrant neighborhood: volatile mediated bacterial interactions in soil.

    PubMed

    Schulz-Bohm, Kristin; Zweers, Hans; de Boer, Wietse; Garbeva, Paolina

    2015-01-01

    There is increasing evidence that volatile organic compounds (VOCs) play essential roles in communication and competition between soil microorganisms. Here we assessed volatile-mediated interactions of a synthetic microbial community in a model system that mimics the natural conditions in the heterogeneous soil environment along the rhizosphere. Phylogenetic different soil bacterial isolates (Burkholderia sp., Dyella sp., Janthinobacterium sp., Pseudomonas sp., and Paenibacillus sp.) were inoculated as mixtures or monoculture in organic-poor, sandy soil containing artificial root exudates (ARE) and the volatile profile and growth were analyzed. Additionally, a two-compartment system was used to test if volatiles produced by inter-specific interactions in the rhizosphere can stimulate the activity of starving bacteria in the surrounding, nutrient-depleted soil. The obtained results revealed that both microbial interactions and shifts in microbial community composition had a strong effect on the volatile emission. Interestingly, the presence of a slow-growing, low abundant Paenibacillus strain significantly affected the volatile production by the other abundant members of the bacterial community as well as the growth of the interacting strains. Furthermore, volatiles released by mixtures of root-exudates consuming bacteria stimulated the activity and growth of starved bacteria. Besides growth stimulation, also an inhibition in growth was observed for starving bacteria exposed to microbial volatiles. The current work suggests that volatiles produced during microbial interactions in the rhizosphere have a significant long distance effect on microorganisms in the surrounding, nutrient-depleted soil. PMID:26579111

  4. Interaction between soil moisture memory and different climate variables

    NASA Astrophysics Data System (ADS)

    Stacke, Tobias; Hagemann, Stefan

    2015-04-01

    A large number of modelling studies show a potential impact of the soil moisture state on regional climate on different time scales. Especially for short prediction periods, perturbations of the soil moisture state may result in significant alteration of surface temperature in the following season. The physical reasoning for such effects are usually attributed to the soil moisture - temperature as well as the soil moisture - precipitation feedbacks. We designed a model experiment to investigate the time scale until the effect of arbitrary soil moisture initialization is forgotten by the model. This time period is called soil moisture memory and computed for different seasons based on an ensemble of nine, 3 year long, simulations per season. These simulations are done using the coupled land-atmosphere model ECHAM6-JSBACH, which is part of the Max Planck Institute for Meteorology's Earth System Model (MPI-ESM). Soil moisture memory was found to range between few days up to several months. While the longest memory often coincides with either snow-covered conditions or follows on monsoon periods, short memory is computed prior to snow-melt and rainy seasons. Additionally, the correlations between soil moisture memory and a number of surface variables was investigated. We found that the magnitude of the initial soil moisture perturbations explains at most 50% of the spatial variation in soil moisture memory while the remaining variance is associated with soil properties and - even stronger - with dynamical variables like surface temperature, evapotranspiration and runoff. This effect differs for different seasons and soil moisture regimes which demonstrates the complexity of soil moisture - climate interactions. Further analysis will be focused on the re-occurrence of soil moisture memory after periods of insignificant memory and the possibility of memory transfer between different land surface state variables.

  5. Ecohydrology of dry regions: storage versus pulse soil water dynamics

    USGS Publications Warehouse

    Lauenroth, William K.; Schlaepfer, Daniel R.; Bradford, John B.

    2014-01-01

    Although arid and semiarid regions are defined by low precipitation, the seasonal timing of temperature and precipitation can influence net primary production and plant functional type composition. The importance of precipitation seasonality is evident in semiarid areas of the western U.S., which comprise the Intermountain (IM) zone, a region that receives important winter precipitation and is dominated by woody plants and the Great Plains (GP), a region that receives primarily summer precipitation and is dominated by perennial grasses. Although these general relationships are well recognized, specific differences in water cycling between these regions have not been well characterized. We used a daily time step soil water simulation model and twenty sites from each region to analyze differences in soil water dynamics and ecosystem water balance. IM soil water patterns are characterized by storage of water during fall, winter, and spring resulting in relatively reliable available water during spring and early summer, particularly in deep soil layers. By contrast, GP soil water patterns are driven by pulse precipitation events during the warm season, resulting in fluctuating water availability in all soil layers. These contrasting patterns of soil water—storage versus pulse dynamics—explain important differences between the two regions. Notably, the storage dynamics of the IN sites increases water availability in deep soil layers, favoring the deeper rooted woody plants in that region, whereas the pulse dynamics of the Great Plains sites provide water primarily in surface layers, favoring the shallow-rooted grasses in that region. In addition, because water received when plants are either not active or only partially so is more vulnerable to evaporation and sublimation than water delivered during the growing season, IM ecosystems use a smaller fraction of precipitation for transpiration (47%) than GP ecosystems (49%). Recognizing the pulse-storage dichotomy in

  6. Predicting and mapping soil available water capacity in Korea.

    PubMed

    Hong, Suk Young; Minasny, Budiman; Han, Kyung Hwa; Kim, Yihyun; Lee, Kyungdo

    2013-01-01

    The knowledge on the spatial distribution of soil available water capacity at a regional or national extent is essential, as soil water capacity is a component of the water and energy balances in the terrestrial ecosystem. It controls the evapotranspiration rate, and has a major impact on climate. This paper demonstrates a protocol for mapping soil available water capacity in South Korea at a fine scale using data available from surveys. The procedures combined digital soil mapping technology with the available soil map of 1:25,000. We used the modal profile data from the Taxonomical Classification of Korean Soils. The data consist of profile description along with physical and chemical analysis for the modal profiles of the 380 soil series. However not all soil samples have measured bulk density and water content at -10 and -1500 kPa. Thus they need to be predicted using pedotransfer functions. Furthermore, water content at -10 kPa was measured using ground samples. Thus a correction factor is derived to take into account the effect of bulk density. Results showed that Andisols has the highest mean water storage capacity, followed by Entisols and Inceptisols which have loamy texture. The lowest water retention is Entisols which are dominated by sandy materials. Profile available water capacity to a depth of 1 m was calculated and mapped for Korea. The western part of the country shows higher available water capacity than the eastern part which is mountainous and has shallower soils. The highest water storage capacity soils are the Ultisols and Alfisols (mean of 206 and 205 mm, respectively). Validation of the maps showed promising results. The map produced can be used as an indication of soil physical quality of Korean soils. PMID:23646290

  7. Predicting and mapping soil available water capacity in Korea

    PubMed Central

    Hong, Suk Young; Han, Kyung Hwa; Kim, Yihyun; Lee, Kyungdo

    2013-01-01

    The knowledge on the spatial distribution of soil available water capacity at a regional or national extent is essential, as soil water capacity is a component of the water and energy balances in the terrestrial ecosystem. It controls the evapotranspiration rate, and has a major impact on climate. This paper demonstrates a protocol for mapping soil available water capacity in South Korea at a fine scale using data available from surveys. The procedures combined digital soil mapping technology with the available soil map of 1:25,000. We used the modal profile data from the Taxonomical Classification of Korean Soils. The data consist of profile description along with physical and chemical analysis for the modal profiles of the 380 soil series. However not all soil samples have measured bulk density and water content at −10 and −1500 kPa. Thus they need to be predicted using pedotransfer functions. Furthermore, water content at −10 kPa was measured using ground samples. Thus a correction factor is derived to take into account the effect of bulk density. Results showed that Andisols has the highest mean water storage capacity, followed by Entisols and Inceptisols which have loamy texture. The lowest water retention is Entisols which are dominated by sandy materials. Profile available water capacity to a depth of 1 m was calculated and mapped for Korea. The western part of the country shows higher available water capacity than the eastern part which is mountainous and has shallower soils. The highest water storage capacity soils are the Ultisols and Alfisols (mean of 206 and 205 mm, respectively). Validation of the maps showed promising results. The map produced can be used as an indication of soil physical quality of Korean soils. PMID:23646290

  8. Soil-plant-biochar interactions and effects on soil C and N cycling in a wheat greenhouse pot experiment.

    NASA Astrophysics Data System (ADS)

    Michie, E.; Panzacchi, P.; Davies, C. A.; Toet, S.; Ineson, P.

    2012-04-01

    Biochar is carbon rich material, able to modify soil qualities and increase soil carbon sequestration. We investigated the benefits, interactions and mechanisms observed when adding biochar (from Miscanthus feedstock) to soil. In a greenhouse experiment with wheat grown in pots under simulated natural conditions, biochars pyrolysed at 360° C and 450° C were applied at 10, 25, and 50 tha-1, with or without nitrogen (urea). These pots were subjected to different water regimes (400 and 800 mm per year) according to a randomised block design. Growth rate, grain yield and total biomass will be related to the biochar production temperature and application rate. The effect of biochar on water availability and C and N cycling will be tested by direct measurements of CO2, CH4 and N2O fluxes from soil using closed dynamic and static chamber methods. Different natural 13C abundance in biochar (Δ13C≈-13) and soil organic matter (SOM; (Δ13C ≈-27) will be used to calculate the relative contribution of biochar to total soil respiration and the potential priming effect of the biochar on SOM. In addition a labelling experiment with 13CO2 will be used to trace C from the atmosphere through the plant, revealing how biochar affects C allocation in plant biomass, rhizodeposition and root respiration. Preliminary results will be presented.

  9. Use of a Cropping System Model for Soil-Specific Optimization of Limited Water

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In the arena of modern agriculture, system models capable of simulating the complex interactions of all the relevant processes in the soil-water-plant-atmosphere continuum are widely accepted as potential tools for decision support to optimize crop inputs of water to achieve location specific yield ...

  10. Soil carbon storage controlled by interactions between geochemistry and climate

    NASA Astrophysics Data System (ADS)

    Doetterl, Sebastian; Stevens, Antoine; Six, Johan; Merckx, Roel; van Oost, Kristof; Casanova Pinto, Manuel; Casanova-Katny, Angélica; Muñoz, Cristina; Boudin, Mathieu; Zagal Venegas, Erick; Boeckx, Pascal

    2015-10-01

    Soils are an important site of carbon storage. Climate is generally regarded as one of the primary controls over soil organic carbon, but there is still uncertainty about the direction and magnitude of carbon responses to climate change. Here we show that geochemistry, too, is an important controlling factor for soil carbon storage. We measured a range of soil and climate variables at 24 sites along a 4,000-km-long north-south transect of natural grassland and shrubland in Chile and the Antarctic Peninsula, which spans a broad range of climatic and geochemical conditions. We find that soils with high carbon content are characterized by substantial adsorption of carbon compounds onto mineral soil and low rates of respiration per unit of soil carbon; and vice versa for soils with low carbon content. Precipitation and temperature were only secondary predictors for carbon storage, respiration, residence time and stabilization mechanisms. Correlations between climatic variables and carbon variables decreased significantly after removing relationships with geochemical predictors. We conclude that the interactions of climatic and geochemical factors control soil organic carbon storage and turnover, and must be considered for robust prediction of current and future soil carbon storage.

  11. Physical and chemical effects of biochar on natural and artificial water repellent soils

    NASA Astrophysics Data System (ADS)

    Hallin, Ingrid; Douglas, Peter; Doerr, Stefan H.; Bryant, Rob; Matthews, Ian; Charbonneau, Cecile

    2014-05-01

    Water repellency (WR) affects soils worldwide. Hydrophobic compounds accumulate in soil through organic matter decomposition, microbial activity, condensation of organic compounds during vegetation fires, or through anthropogenic impacts such as oil spills. WR hinders vegetation establishment, which can lead to soil erosion and increased runoff. Biochar is currently being evaluated for its potential to increase soil carbon and as a soil amendment. To date, the effect of biochar on water repellent soils has remained largely undetermined. This study considered the potential of biochar as both a physical and chemical amendment for water repellent soils by asking two questions: does adding biochar reduce the observed degree of soil water repellency; and does biochar remove hydrophobic compounds from soil? The potential of biochar as a physical amendment to water repellent soils was evaluated by mixing 5, 10, 25 and 40% (by weight) each of coarse and fine ground biochar with two naturally water repellent soils and measuring the water drop penetration time (WDPT) for each mixture. Biochar particles beyond the range of existing soil particle diameters increased WDPT variability, which could be explained by increased surface roughness and the resulting enhancement of water repellency effects through Cassie-Baxter interactions. Overall, fine biochar was more effective at reducing water repellency: 25% w/w rendered both soils studied wettable. Removal of hydrophobic compounds by biochar was tested by mixing 1, 5, 10, 25 and 40% biochar with acid washed sand (AWS) coated with 1.2x10-5 mol octadecane and octadecanoic acid (per gram AWS, which corresponds to approximately 50 monolayers hydrophobic compound per gram AWS). Each mix stood for 1 to 30 days in a solution of pH 3, 6 or 9 before the AWS was extracted and the quantity of hydrophobic compound remaining determined by infrared spectroscopy and/or gas chromatography. Biochar successfully removed the hydrophobic compounds

  12. The use of soil electrical resistivity to monitor plant and soil water relationships in vineyards

    NASA Astrophysics Data System (ADS)

    Brillante, L.; Mathieu, O.; Bois, B.; van Leeuwen, C.; Lévêque, J.

    2015-03-01

    Soil water availability deeply affects plant physiology. In viticulture it is considered a major contributor to the "terroir" effect. The assessment of soil water in field conditions is a difficult task, especially over large surfaces. New techniques are therefore required in order to better explore variations of soil water content in space and time with low disturbance and with great precision. Electrical resistivity tomography (ERT) meets these requirements for applications in plant sciences, agriculture and ecology. In this paper, possible techniques to develop models that allow the use of ERT to spatialise soil water available to plants are reviewed. An application of soil water monitoring using ERT in a grapevine plot in Burgundy (north-east France) during the vintage 2013 is presented. We observed the lateral heterogeneity of ERT-derived fraction of transpirable soil water (FTSW) variations, and differences in water uptake depend on grapevine water status (leaf water potentials measured both at predawn and at solar noon and contemporary to ERT monitoring). Active zones in soils for water movements were identified. The use of ERT in ecophysiological studies, with parallel monitoring of plant water status, is still rare. These methods are promising because they have the potential to reveal a hidden part of a major function of plant development: the capacity to extract water from the soil.

  13. Quantifying crop water stress factors from soil water measurements in a limited irrigation experiment

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Quantifying crop water stress factors from soil water measurements in a limited irrigation experiment. A correct simulation of crop responses to water stress is essential for a system model. In this study, we investigated three methods of quantifying water deficit stresses based on soil water meas...

  14. Quantification of the inevitable: the influence of soil macrofauna on soil water movement in rehabilitated open-cut mined lands

    NASA Astrophysics Data System (ADS)

    Arnold, S.; Williams, E. R.

    2016-01-01

    Recolonisation of soil by macrofauna (especially ants, termites and earthworms) in rehabilitated open-cut mine sites is inevitable and, in terms of habitat restoration and function, typically of great value. In these highly disturbed landscapes, soil invertebrates play a major role in soil development (macropore configuration, nutrient cycling, bioturbation, etc.) and can influence hydrological processes such as infiltration, seepage, runoff generation and soil erosion. Understanding and quantifying these ecosystem processes is important in rehabilitation design, establishment and subsequent management to ensure progress to the desired end goal, especially in waste cover systems designed to prevent water reaching and transporting underlying hazardous waste materials. However, the soil macrofauna is typically overlooked during hydrological modelling, possibly due to uncertainties on the extent of their influence, which can lead to failure of waste cover systems or rehabilitation activities. We propose that scientific experiments under controlled conditions and field trials on post-mining lands are required to quantify (i) macrofauna-soil structure interactions, (ii) functional dynamics of macrofauna taxa, and (iii) their effects on macrofauna and soil development over time. Such knowledge would provide crucial information for soil water models, which would increase confidence in mine waste cover design recommendations and eventually lead to higher likelihood of rehabilitation success of open-cut mining land.

  15. Effects of soil management techniques on soil water erosion in apricot orchards.

    PubMed

    Keesstra, Saskia; Pereira, Paulo; Novara, Agata; Brevik, Eric C; Azorin-Molina, Cesar; Parras-Alcántara, Luis; Jordán, Antonio; Cerdà, Artemi

    2016-05-01

    Soil erosion is extreme in Mediterranean orchards due to management impact, high rainfall intensities, steep slopes and erodible parent material. Vall d'Albaida is a traditional fruit production area which, due to the Mediterranean climate and marly soils, produces sweet fruits. However, these highly productive soils are left bare under the prevailing land management and marly soils are vulnerable to soil water erosion when left bare. In this paper we study the impact of different agricultural land management strategies on soil properties (bulk density, soil organic matter, soil moisture), soil water erosion and runoff, by means of simulated rainfall experiments and soil analyses. Three representative land managements (tillage/herbicide/covered with vegetation) were selected, where 20 paired plots (60 plots) were established to determine soil losses and runoff. The simulated rainfall was carried out at 55mmh(-1) in the summer of 2013 (<8% soil moisture) for one hour on 0.25m(2) circular plots. The results showed that vegetation cover, soil moisture and organic matter were significantly higher in covered plots than in tilled and herbicide treated plots. However, runoff coefficient, total runoff, sediment yield and soil erosion were significantly higher in herbicide treated plots compared to the others. Runoff sediment concentration was significantly higher in tilled plots. The lowest values were identified in covered plots. Overall, tillage, but especially herbicide treatment, decreased vegetation cover, soil moisture, soil organic matter, and increased bulk density, runoff coefficient, total runoff, sediment yield and soil erosion. Soil erosion was extremely high in herbicide plots with 0.91Mgha(-1)h(-1) of soil lost; in the tilled fields erosion rates were lower with 0.51Mgha(-1)h(-1). Covered soil showed an erosion rate of 0.02Mgha(-1)h(-1). These results showed that agricultural management influenced water and sediment dynamics and that tillage and herbicide

  16. Soil water balance in an unsaturated pyroclastic slope for evaluation of soil hydraulic behaviour and boundary conditions

    NASA Astrophysics Data System (ADS)

    Pirone, Marianna; Papa, Raffaele; Nicotera, Marco Valerio; Urciuoli, Gianfranco

    2015-09-01

    Flowslides in granular soils pose a major threat to life and the environment. Their initiation in unsaturated soils is regulated by rainfall infiltration which reduces the matric suction and hence shear strength. Analysis of such phenomena is of strategic importance especially when it aims to mitigate landslide risk by means of early warning systems (EWSs). In this framework, physically-based models need to reproduce the hydro-mechanical behaviour of the slopes through numerical analyses, whose main uncertainty concerns the hydraulic conditions at the boundaries of the studied domain and hydraulic conductivity functions of unsaturated soils. Hence consummate knowledge of both these factors is absolutely necessary for efficient predictions. In this paper hydraulic boundary conditions and hydraulic conductivity functions are investigated at the scale of the slope through an application of soil water balance based on in-situ monitoring at the test site of Monteforte Irpino (southern Italy). Meteorological data, matric suction and soil water content measurements were collected over four years at the test site. The soil water balance was analysed on a seasonal time scale with regard to the whole pyroclastic cover resting on the steep limestone substratum. Infiltration and runoff are estimated, interaction between the soil cover and the substratum is investigated, and the hydraulic conductivity functions operative at the site scale are defined.

  17. Soil management system for water conservation and mitigation of global change effect

    NASA Astrophysics Data System (ADS)

    Ospina, A.; Florentino, A.; Lorenzo, V.

    2012-04-01

    One of the main constraints in rained agriculture is the water availability for plant growth which depends largely on the ability of the soil to allow water flow, infiltration and its storage. In Venezuela, the interaction between aggressive climatic conditions, highly susceptible soils and inadequate management systems have caused soil degradation which together with global change threatened the food production sustainability. To address this problem, we need to implement conservationist management strategies that improve infiltration rate, permeability and water holding capacity in soil and reduce water loss by protecting the soil surface. In order to study the impact of different management systems on soil water balance in a Fluventic Haplustept, the effects of 11 years of tillage and crops rotation management were evaluated in a long term field experiment located in Turén (Portuguesa state). The evaluated tillage systems were no tillage (NT) and conventional tillage (CT) and crop rotation treatments were maize (Zea mays)-cotton (Gossypium hirsutum) and maize-bean (Vigna unguiculata). Treatments were established in plots arranged in a randomized block design with three replicates. The gravimetric moisture content was determined in the upper 20 cm of soil, at eight different sampling dates. Results showed increased in time of the water availability with the use of tillage and corn-cotton rotation and, better protection of the soil against raindrop impact with crop residues. Water retention capacity also increased and improved structural condition on soil surface such as infiltration, storage and water flow distribution in the rooting zone. We conclude that these strategies of land use and management would contribute to mitigate the climate change effects on food production in this region of Venezuela. Key words: Soil quality; rained agriculture; plant water availability

  18. Predicting sub-grid variability of soil water content from basic soil information

    NASA Astrophysics Data System (ADS)

    Qu, Wei; Bogena, Heye; Huisman, Johan Alexander; Vanderborght, Jan; Schuh, Max; Priesack, Eckart; Vereecken, Harry

    2015-04-01

    Knowledge of unresolved soil water content variability within model grid cells (i.e. sub-grid variability) is important for accurate predictions of land-surface energy and hydrologic fluxes. Here, we derived a closed-form expression to describe how soil water content variability depends on mean soil water content using stochastic analysis of 1D unsaturated gravitational flow based on the van Genuchten-Mualem (VGM) model. A sensitivity analysis of this closed-form expression showed that the n parameter strongly influenced both the shape and magnitude of the maximum of this relationship. In a next step, the closed-form expression was used to predict soil water content variability for eight datasets with varying soil texture using VGM parameters obtained from pedotransfer functions that rely on readily available soil information. Generally, there was good agreement between observed and predicted soil water content variability despite the obvious simplifications that were used to derive the closed-form expression (e.g. gravity flow in dry soils). A simplified closed-form expression that neglected the effect of pressure head fluctuations showed that the good performance in the dry soil range is related to the dominant role of the variability in MVG parameters determining water retention as compared to the effect of water flow. Furthermore, the novel closed-form expression was successfully used to inversely estimate the variability of hydraulic properties from observed data on soil water content variability from several test sites in Germany, China and Australia.

  19. MODELING TOOLS FOR GROUND WATER-SURFACE WATER INTERACTIONS

    EPA Science Inventory

    This project develops algorithms for simulating the dynamic interactions between surface water and ground water in rivers and riparian streams. The algorithms rely on physically based linear response functions which describe the exchange rates and volumes of water between the str...

  20. Effect of Thickness of a Water Repellent Soil Layer on Soil Evaporation Rate

    NASA Astrophysics Data System (ADS)

    Ahn, S.; Im, S.; Doerr, S.

    2012-04-01

    A water repellent soil layer overlying wettable soil is known to affect soil evaporation. This effect can be beneficial for water conservation in areas where water is scarce. Little is known, however, about the effect of the thickness of the water repellent layer. The thickness of this layer can vary widely, and particularly after wildfire, with the soil temperature reached and the duration of the fire. This study was conducted to investigate the effect of thickness of a top layer of water repellent soil on soil evaporation rate. In order to isolate the thickness from other possible factors, fully wettable standard sand (300~600 microns) was used. Extreme water repellency (WDPT > 24 hours) was generated by 'baking' the sand mixed with oven-dried pine needles (fresh needles of Pinus densiflora) at the mass ratio of 1:13 (needle:soil) at 185°C for 18 hours. The thicknesses of water repellent layers were 1, 2, 3 and 7 cm on top of wettable soil. Fully wettable soil columns were prepared as a control. Soil columns (8 cm diameter, 10 cm height) were covered with nylon mesh. Tap water (50 ml, saturating 3 cm of a soil column) was injected with hypoderm syringes from three different directions at the bottom level. The injection holes were sealed with hot-melt adhesive immediately after injection. The rate of soil evaporation through the soil surface was measured by weight change under isothermal condition of 40°C. Five replications were made for each. A trend of negative correlation between the thickness of water repellent top layer and soil evaporation rate is discussed in this contribution.

  1. Modeling as a tool for management of saline soils and irrigation waters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Optimal management of saline soils and irrigation waters requires consideration of many interrelated factors including, climate, water applications and timing, water flow, plant water uptake, soil chemical reactions, plant response to salinity and solution composition, soil hydraulic properties and ...

  2. Teaching Soil and Water Conservation: A Classroom and Field Guide.

    ERIC Educational Resources Information Center

    Foster, Albert B.; Fox, Adrian C.

    Compiled in this booklet are 22 activities designed to develop awareness of the importance of conservation and the wise use of soil and moisture on croplands, grasslands, and woodlands. They have been selected by Soil Conservation Service (SCS) personnel and consultants to show that the way we manage our basic natural resources, soil and water,…

  3. Soil water retention within an eroded and restored landscape

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Significant changes in soil properties and productivity have occurred as a result of intensive row crop production. Many of these changes are related to soil loss from water, wind, and tillage erosion. Soil is lost from convex and steeper landscape positions and deposited in concave lower landscape ...

  4. Soil Water and Shallow Groundwater Relations in an Agricultural Hillslope

    NASA Astrophysics Data System (ADS)

    Logsdon, S. D.; Schilling, K. E.

    2007-12-01

    Shallow water tables contribute to soil water variations under rolling topography, and soil properties contribute to shallow water table fluctutations. Preferential flow through large soil pores can cause a rise in the water table with little increase in soil water except near the soil surface. Lateral groundwater flow can cause a large rise in water table at toeslope and depressional landscape positions. As plants transpire, water can move up into the root zone from the water table and wet soil below the root zone. Roots can utilize water in the capillary fringe. The purpose of this study was to interface automated measurements of soil water content and water table depth for determining the importance of drainage and upward movement. In 2006 soil water and water table depth were monitored at three positions: shoulder, backslope, and toeslope. Neutron access tubes were manually monitored to 2.3 m depth, and automated soil moisture was measured using CS616 probes installed at 0.3, 0.5, 0.7, and 0.9 m depth. Water table depths were monitored manually and automated, but the automated measurements failed during the season at two sites. In 2007, similar measurements were made at one toeslope position, but the CS616 probes were installed at nine depths and better quality automated well depth equipment was used. The 2006 data revealed little landscape position effect on daytime soil water loss on a wetter date; however, on a dry day just before a rain, daytime water loss was greatest for the toeslope positon and least for the shoulder position. After a period of intense rain, a rapid and significant water table rise occurred at the toeslope position but little water table rise occurred at the other landscape positions. The rapid toeslope water table rise was likely caused by lateral groundwater flow whereas minor water table rise at the other positions was likely due to preferential flow since the soil had not wet up below 0.6 m. Use of automated equipment has improved

  5. Lichen-moss interactions within biological soil crusts

    NASA Astrophysics Data System (ADS)

    Ruckteschler, Nina; Williams, Laura; Büdel, Burkhard; Weber, Bettina

    2015-04-01

    Biological soil crusts (biocrusts) create well-known hotspots of microbial activity, being important components of hot and cold arid terrestrial regions. They colonize the uppermost millimeters of the soil, being composed of fungi, (cyano-) bacteria, algae, lichens, bryophytes and archaea in varying proportions. Biocrusts protect the (semi-) arid landscape from wind and water erosion, and also increase water holding capacity and nutrient content. Depending on location and developmental stage, composition and species abundance vary within biocrusts. As species live in close contact, they are expected to influence each other, but only a few interactions between different organisms have so far been explored. In the present study, we investigated the effects of the lichen Fulgensia fulgens whilst growing on the moss Trichostomum crispulum. While 77% of Fulgensia fulgens thalli were found growing associated with mosses in a German biocrust, up to 95% of Fulgensia bracteata thalli were moss-associated in a Swedish biocrust. In 49% (Germany) and in 78% (Sweden) of cases, thalli were observed on the moss T. crispulum and less frequently on four and three different moss species. Beneath F. fulgens and F. bracteata thalli, the mosses were dead and in close vicinity to the lichens the mosses appeared frail, bringing us to the assumption that the lichens may release substances harming the moss. We prepared a water extract from the lichen F. fulgens and used this to water the moss thalli (n = 6) on a daily basis over a time-span of three weeks. In a control setup, artificial rainwater was applied to the moss thalli (n = 6). Once a week, maximum CO2 gas exchange rates of the thalli were measured under constant conditions and at the end of the experiment the chlorophyll content of the moss samples was determined. In the course of the experiment net photosynthesis (NP) of the treatment samples decreased concurrently with an increase in dark respiration (DR). The control samples

  6. Genetic by environment interactions affect plant–soil linkages

    PubMed Central

    Pregitzer, Clara C; Bailey, Joseph K; Schweitzer, Jennifer A

    2013-01-01

    The role of plant intraspecific variation in plant–soil linkages is poorly understood, especially in the context of natural environmental variation, but has important implications in evolutionary ecology. We utilized three 18- to 21-year-old common gardens across an elevational gradient, planted with replicates of five Populus angustifolia genotypes each, to address the hypothesis that tree genotype (G), environment (E), and G × E interactions would affect soil carbon and nitrogen dynamics beneath individual trees. We found that soil nitrogen and carbon varied by over 50% and 62%, respectively, across all common garden environments. We found that plant leaf litter (but not root) traits vary by genotype and environment while soil nutrient pools demonstrated genotype, environment, and sometimes G × E interactions, while process rates (net N mineralization and net nitrification) demonstrated G × E interactions. Plasticity in tree growth and litter chemistry was significantly related to the variation in soil nutrient pools and processes across environments, reflecting tight plant–soil linkages. These data overall suggest that plant genetic variation can have differential affects on carbon storage and nitrogen cycling, with implications for understanding the role of genetic variation in plant–soil feedback as well as management plans for conservation and restoration of forest habitats with a changing climate. PMID:23919173

  7. Assessing the contribution of nonhydraulic forces to the destruction of bonds between soil particles during water erosion

    NASA Astrophysics Data System (ADS)

    Larionov, G. A.; Bushueva, O. G.; Dobrovol'skaya, N. G.; Kiryukhina, Z. P.; Litvin, L. F.; Krasnov, S. F.

    2016-05-01

    It has been experimentally shown with monoaggregate model samples of chernozemic soil as an example that the weakening of cohesion between soil particles is due to the molecular interaction of soil particles with water as a dipole substance rather than to the hydraulic forces of the flow. Therefore, soil erosion should be considered as a two-stage process. First, the bonds between particles are weakened due to the interaction of soil particles with water; then, the particles that lost bonds with neighboring ones are entrapped by the flow. Thus, the erosion rate of a consolidated soil is determined by the destruction of bonds between particles during their interaction with water, rather than the flow velocity, although this factor also affects the erosion rate.

  8. Experimental and mathematical modeling of soil water and heat regime in selected soils

    NASA Astrophysics Data System (ADS)

    Kodesova, Radka; Fer, Miroslav; Klement, Ales; Nikodem, Antonin; Vlasakova, Mirka; Tepla, Daniela; Jaksik, Ondrej

    2013-04-01

    Knowledge of soil thermal (heat) properties is essential when assessing heat transport in soils. Heat regime in soils associates with many other soil processes (like water evaporation and diffusion, plant transpiration, contaminants behavior etc.). Thermal properties are needed when assessing affectivity of energy gathering from soil profiles using horizontal ground heat exchangers, which is a main goal of this study. Study is focused on measuring of thermal properties (heat capacity and heat conductivity) in representative soils of the Czech Republic. Measurements were performed on soil samples taken from the surface horizons of 11 representative soil types and from 2 soil substrates (sand and loess). The measured relationships between the heat conductivity and volumetric soil-water content were described by non-linear equations (Chung and Horton, 1987). The measured relationships between the heat capacity and volumetric soil-water content were expressed using the linear equations. The greatest values of the heat conductivity were measured in sandy soils (sandy and gravely sand substrates). The average values were obtained in soils on loess substrates. Lower values were obtained for all Cambisols (variable substrates). The lowest values were measured in Stagnic Chernozem Siltic on marlite. Opposite trend was observed for the maximal heat capacity, which was mostly impacted by water content. A soil water and heat regime within the soil profile was monitored at one location. In addition the impact of various soil cover at the soil top on soil water content and temperature was measured. Soil hydraulic properties were measured using the multistep-outflow technique. The saturated hydraulic conductivities were also measured using the Guelph permeameter. Programs HYDRUS-1D and 2D/3D were used for a mathematical interpretation of the observed soil water and heat regime. Acknowledgment: Authors acknowledge the financial support of the Technology Agency of the Czech

  9. Microbial enhancement of hydrazine degradation in soil and water

    SciTech Connect

    Ou, L.T.; Street, J.J.

    1987-09-01

    In an early study, the authors reported that hydrazine was rapidly degraded in Arredondo fine sand. By comparing the degradation results in sterile and nonsterile soils, it was concluded that biological degradation was responsible for about 20% of hydrazine disappearance from soils. They isolated a heterotrophic bacterium, Achromobacter sp., from the Arredondo soil and found that the organism had a high capacity to degrade hydrazine to the nontoxic product dinitrogen gas. In the present study, the authors attempted to enhance hydrazine degradation in water and soil samples by inoculating with a hydrazine-degrading bacterium, Achromobacter sp. Factors that influence hydrazine degradation in water and soil are discussed.

  10. Nonequilibrium water dynamics in the rhizosphere: How mucilage affects water flow in soils

    NASA Astrophysics Data System (ADS)

    Kroener, Eva; Zarebanadkouki, Mohsen; Kaestner, Anders; Carminati, Andrea

    2014-08-01

    The flow of water from soil to plant roots is controlled by the properties of the narrow region of soil close to the roots, the rhizosphere. In particular, the hydraulic properties of the rhizosphere are altered by mucilage, a polymeric gel exuded by the roots. In this paper we present experimental results and a conceptual model of water flow in unsaturated soils mixed with mucilage. A central hypothesis of the model is that the different drying/wetting rate of mucilage compared to the bulk soil results in nonequilibrium relations between water content and water potential in the rhizosphere. We coupled this nonequilibrium relation with the Richards equation and obtained a constitutive equation for water flow in soil and mucilage. To test the model assumptions, we measured the water retention curve and the saturated hydraulic conductivity of sandy soil mixed with mucilage from chia seeds. Additionally, we used neutron radiography to image water content in a layer of soil mixed with mucilage during drying and wetting cycles. The radiographs demonstrated the occurrence of nonequilibrium water dynamics in the soil-mucilage mixture. The experiments were simulated by numerically solving the nonequilibrium model. Our study provides conceptual and experimental evidences that mucilage has a strong impact on soil water dynamics. During drying, mucilage maintains a greater soil water content for an extended time, while during irrigation it delays the soil rewetting. We postulate that mucilage exudation by roots attenuates plant water stress by modulating water content dynamics in the rhizosphere.

  11. Water dynamics and interactions in water-polyether binary mixtures.

    PubMed

    Fenn, Emily E; Moilanen, David E; Levinger, Nancy E; Fayer, Michael D

    2009-04-22

    Poly(ethylene) oxide (PEO) is a technologically important polymer with a wide range of applications including ion-exchange membranes, protein crystallization, and medical devices. PEO's versatility arises from its special interactions with water. Water molecules may form hydrogen-bond bridges between the ether oxygens of the backbone. While steady-state measurements and theoretical studies of PEO's interactions with water abound, experiments measuring dynamic observables are quite sparse. A major question is the nature of the interactions of water with the ether oxygens as opposed to the highly hydrophilic PEO terminal hydroxyls. Here, we examine a wide range of mixtures of water and tetraethylene glycol dimethyl ether (TEGDE), a methyl-terminated derivative of PEO with 4 repeat units (5 ether oxygens), using ultrafast infrared polarization selective pump-probe measurements on water's hydroxyl stretching mode to determine vibrational relaxation and orientational relaxation dynamics. The experiments focus on the dynamical interactions of water with the ether backbone because TEGDE does not have the PEO terminal hydroxyls. The experiments observe two distinct subensembles of water molecules: those that are hydrogen bonded to other waters and those that are associated with TEGDE molecules. The water orientational relaxation has a fast component of a few picoseconds (water-like) followed by much slower decay of approximately 20 ps (TEGDE associated). The two decay times vary only mildly with the water concentration. The two subensembles are evident even in very low water content samples, indicating pooling of water molecules. Structural change as water content is lowered through either conformational changes in the backbone or increasing hydrophobic interactions is discussed. PMID:19323522

  12. Critical water contents of hydrophobic soils in New Zealand

    NASA Astrophysics Data System (ADS)

    Landl, Magdalena; Holzinger, Ursula; Singh, Ranvir; Klik, Andreas

    2013-04-01

    Soil water repellency is an important problem for pasture farming in New Zealand which causes low infiltration rates and increased surface runoff. However, the real extent of this issue is not yet evaluated. Water repellency is thought to appear on dry soils, when the water content falls below a critical limit. The main objectives of this study was 1) to investigate the effects of different amounts of infiltration water on hydrophobicity of three selected soils under grassland in the North island of New Zealand, and 2) to determine the critical water content for ten sites with five different soil types. In April 2011 undisturbed and disturbed soil samples from a brown, gley and organic soil have been taken from sites around Mount Taranaki. Soil water repellency was determined using the Water Droplet Penetration Time Test (WDPT) and the Molarity of Ethanol Droplet Test (MED). During the lab experiment four amounts of water were applied to the 270 cm³ samples: 400, 800, 1600 and 2400 mL . One test was performed with cold and one with hot (80 °C) water. Each test was replicated four times. In the leachate the amount of dissolved organic carbon was analyzed. The experiments showed that only for the brown soil water repellency decreased significantly with increasing amount of infiltration water whereas for gley soils no correlation was found. Gley soil had initially a lower degree of hydrophobicity compared to the other soils. Possibly due to the higher bulk density of these soils, the carbon compounds directly surrounding the soil particles wre rearranged rather than leached. No clear pattern could be obtained for organic soils. This may be explained by the high initial carbon content of more than 20%. It may take a much greater amount of infiltration to affect hydrophobicity. The critical contact angle of investigated soils above which water repellency is moderately persistent, was 93.8°. In May 2012 ten more sites were sampled and five soil types were investigated

  13. Percolation behavior of tritiated water into a soil packed bed

    SciTech Connect

    Honda, T.; Katayama, K.; Uehara, K.; Fukada, S.; Takeishi, T.

    2015-03-15

    A large amount of cooling water is used in a D-T fusion reactor. The cooling water will contain tritium with high concentration because tritium can permeate metal walls at high temperature easily. A development of tritium handling technology for confining tritiated water in the fusion facility is an important issue. In addition, it is also important to understand tritium behavior in environment assuming severe accidents. In this study, percolation experiments of tritiated water in soil packed bed were carried out and tritium behavior in soil was discussed. Six soil samples were collected in Hakozaki campus of Kyushu University. These particle densities were of the same degree as that of general soils and moisture contents were related to BET surface area. For two soil samples used in the percolation experiment of tritiated water, saturated hydraulic conductivity agreed well with the estimating value by Creager. Tritium retention ratio in the soil packed bed was larger than water retention. This is considered to be due to an effect of tritium sorption on the surface of soil particles. The isotope exchange capacity estimated by assuming that H/T ratio of supplied tritiated water and H/T ratio of surface water of soil particle was equal was comparable to that on cement paste and mortar which were obtained by exposure of tritiated water vapor. (authors)

  14. EFFECTIVENESS OF SOIL AND WATER CONSERVATION PRACTICES FOR POLLUTION CONTROL

    EPA Science Inventory

    The potential water quality effects and economic implications of soil and water conservation practices (SWCPs) are identified. Method for estimating the effects of SWCPs on pollutant losses from croplands are presented. Mathematical simulation and linear programming models were u...

  15. Measuring and Modelling water related soil - vegetation feedbacks in a fallow plot

    NASA Astrophysics Data System (ADS)

    Ursino, Nadia; Cassiani, Giorgio; Deiana, Rita; Vignoli, Giulio; Boaga, Jacopo

    2013-04-01

    Land fallowing is one possible response to shortage of water for irrigation. Leaving the soil unseeded implies a change of the soil functioning that has an impact on the water cycle. The development of a soil crust in the open spaces between the patterns of grass weed affects the soil properties and the field scale water balance. The objective of this study was to test the potential of integrated non invasive geophysics and ground-image analysis and to quantify the effect of the soil vegetation interaction on the water balance of a fallow land at the local and plot scale. We measured repeatedly in space and time local soil saturation and vegetation cover over two small plots located in southern Sardinia, Italy, during an infiltration experiment. One plot was left unseeded and the other was cultivated. The comparative analysis of the experimental data evidenced a positive feedback between weed growth and infiltration at the fallow plot. A simple bucket model captured the different soil moisture dynamics at the two plots during the infiltration experiment and was used to estimate the impact of the soil vegetation feedback on the yearly water balance at the site.

  16. Principles of Water Flow in Real-World Soils and Related Imbalances

    NASA Astrophysics Data System (ADS)

    Lin, H.

    2012-12-01

    Heterogeneities, structures, interfaces, roughness, and organisms in multiphase soil systems make the real-world soil deviated significantly from the continuum assumption. The first principle of water flow in porous media came to light in the 19th century, known as the Darcy's law, which was later modified by E. Buckingham to describe unsaturated water flow in soils. This principle is essentially a macroscopic view of steady-state water flux being linearly proportional to hydraulic gradient and hydraulic conductivity. The second principle was proposed by L.A. Richards in the 20th century, which describes the minimum pressure gradient needed to initiate water flow through the soil-air interface. This principle can be extended to provide a more cohesive explanation to a number of soil hydrologic phenomena related to various interfaces and microscopic features (such as hysteresis, hydrophobicity, and flow through layered soils). The third principle is emerging in the 21st century, where a combined macroscopic and microscopic view portrays mosaic-like complex flow regimes in heterogeneous soils in which imbalance seems to be common leading to widespread preferential flow. The dynamic interaction between preferential flow and matrix flow under changing conditions results in complex, evolving flow networks that are embedded in the matrix of land surface and subsurface. Quantification and integration of these flow principles can lead to improved prediction of water flow in real-world soils and landscapes.

  17. Soil warming, carbon–nitrogen interactions, and forest carbon budgets

    PubMed Central

    Melillo, Jerry M.; Butler, Sarah; Johnson, Jennifer; Mohan, Jacqueline; Steudler, Paul; Lux, Heidi; Burrows, Elizabeth; Bowles, Francis; Smith, Rose; Scott, Lindsay; Vario, Chelsea; Hill, Troy; Burton, Andrew; Zhou, Yu-Mei; Tang, Jim

    2011-01-01

    Soil warming has the potential to alter both soil and plant processes that affect carbon storage in forest ecosystems. We have quantified these effects in a large, long-term (7-y) soil-warming study in a deciduous forest in New England. Soil warming has resulted in carbon losses from the soil and stimulated carbon gains in the woody tissue of trees. The warming-enhanced decay of soil organic matter also released enough additional inorganic nitrogen into the soil solution to support the observed increases in plant carbon storage. Although soil warming has resulted in a cumulative net loss of carbon from a New England forest relative to a control area over the 7-y study, the annual net losses generally decreased over time as plant carbon storage increased. In the seventh year, warming-induced soil carbon losses were almost totally compensated for by plant carbon gains in response to warming. We attribute the plant gains primarily to warming-induced increases in nitrogen availability. This study underscores the importance of incorporating carbon–nitrogen interactions in atmosphere–ocean–land earth system models to accurately simulate land feedbacks to the climate system. PMID:21606374

  18. Soil warming, carbon-nitrogen interactions, and forest carbon budgets.

    PubMed

    Melillo, Jerry M; Butler, Sarah; Johnson, Jennifer; Mohan, Jacqueline; Steudler, Paul; Lux, Heidi; Burrows, Elizabeth; Bowles, Francis; Smith, Rose; Scott, Lindsay; Vario, Chelsea; Hill, Troy; Burton, Andrew; Zhou, Yu-Mei; Tang, Jim

    2011-06-01

    Soil warming has the potential to alter both soil and plant processes that affect carbon storage in forest ecosystems. We have quantified these effects in a large, long-term (7-y) soil-warming study in a deciduous forest in New England. Soil warming has resulted in carbon losses from the soil and stimulated carbon gains in the woody tissue of trees. The warming-enhanced decay of soil organic matter also released enough additional inorganic nitrogen into the soil solution to support the observed increases in plant carbon storage. Although soil warming has resulted in a cumulative net loss of carbon from a New England forest relative to a control area over the 7-y study, the annual net losses generally decreased over time as plant carbon storage increased. In the seventh year, warming-induced soil carbon losses were almost totally compensated for by plant carbon gains in response to warming. We attribute the plant gains primarily to warming-induced increases in nitrogen availability. This study underscores the importance of incorporating carbon-nitrogen interactions in atmosphere-ocean-land earth system models to accurately simulate land feedbacks to the climate system. PMID:21606374

  19. The interactive effects of soil transplant into colder regions and cropping on soil microbiology and biogeochemistry.

    PubMed

    Liu, Shanshan; Wang, Feng; Xue, Kai; Sun, Bo; Zhang, Yuguang; He, Zhili; Van Nostrand, Joy D; Zhou, Jizhong; Yang, Yunfeng

    2015-03-01

    Soil transplant into warmer regions has been shown to alter soil microbiology. In contrast, little is known about the effects of soil transplant into colder regions, albeit that climate cooling has solicited attention in recent years. To address this question, we transplanted bare fallow soil over large transects from southern China (subtropical climate zone) to central (warm temperate climate zone) and northern China (cold temperate climate zone). After an adaptation period of 4 years, soil nitrogen components, microbial biomass and community structures were altered. However, the effects of soil transplant on microbial communities were dampened by maize cropping, unveiling a negative interaction between cropping and transplant. Further statistical analyses with Canonical correspondence analysis and Mantel tests unveiled annual average temperature, relative humidity, aboveground biomass, soil pH and NH4 (+) -N content as environmental attributes closely correlated with microbial functional structures. In addition, average abundances of amoA-AOA (ammonia-oxidizing archaea) and amoA-AOB (ammonia-oxidizing bacteria) genes were significantly (P < 0.05) correlated with soil nitrification capacity, hence both AOA and AOB contributed to the soil functional process of nitrification. These results suggested that the soil nitrogen cycle was intimately linked with microbial community structure, and both were subjected to disturbance by soil transplant to colder regions and plant cropping. PMID:24548455

  20. Coupling root architecture and pore network modeling - an attempt towards better understanding root-soil interactions

    NASA Astrophysics Data System (ADS)

    Leitner, Daniel; Bodner, Gernot; Raoof, Amir

    2013-04-01

    Understanding root-soil interactions is of high importance for environmental and agricultural management. Root uptake is an essential component in water and solute transport modeling. The amount of groundwater recharge and solute leaching significantly depends on the demand based plant extraction via its root system. Plant uptake however not only responds to the potential demand, but in most situations is limited by supply form the soil. The ability of the plant to access water and solutes in the soil is governed mainly by root distribution. Particularly under conditions of heterogeneous distribution of water and solutes in the soil, it is essential to capture the interaction between soil and roots. Root architecture models allow studying plant uptake from soil by describing growth and branching of root axes in the soil. Currently root architecture models are able to respond dynamically to water and nutrient distribution in the soil by directed growth (tropism), modified branching and enhanced exudation. The porous soil medium as rooting environment in these models is generally described by classical macroscopic water retention and sorption models, average over the pore scale. In our opinion this simplified description of the root growth medium implies several shortcomings for better understanding root-soil interactions: (i) It is well known that roots grow preferentially in preexisting pores, particularly in more rigid/dry soil. Thus the pore network contributes to the architectural form of the root system; (ii) roots themselves can influence the pore network by creating preferential flow paths (biopores) which are an essential element of structural porosity with strong impact on transport processes; (iii) plant uptake depend on both the spatial location of water/solutes in the pore network as well as the spatial distribution of roots. We therefore consider that for advancing our understanding in root-soil interactions, we need not only to extend our root models

  1. Moditored unsaturated soil transport processes as a support for large scale soil and water management

    NASA Astrophysics Data System (ADS)

    Vanclooster, Marnik

    2010-05-01

    The current societal demand for sustainable soil and water management is very large. The drivers of global and climate change exert many pressures on the soil and water ecosystems, endangering appropriate ecosystem functioning. The unsaturated soil transport processes play a key role in soil-water system functioning as it controls the fluxes of water and nutrients from the soil to plants (the pedo-biosphere link), the infiltration flux of precipitated water to groundwater and the evaporative flux, and hence the feed back from the soil to the climate system. Yet, unsaturated soil transport processes are difficult to quantify since they are affected by huge variability of the governing properties at different space-time scales and the intrinsic non-linearity of the transport processes. The incompatibility of the scales between the scale at which processes reasonably can be characterized, the scale at which the theoretical process correctly can be described and the scale at which the soil and water system need to be managed, calls for further development of scaling procedures in unsaturated zone science. It also calls for a better integration of theoretical and modelling approaches to elucidate transport processes at the appropriate scales, compatible with the sustainable soil and water management objective. Moditoring science, i.e the interdisciplinary research domain where modelling and monitoring science are linked, is currently evolving significantly in the unsaturated zone hydrology area. In this presentation, a review of current moditoring strategies/techniques will be given and illustrated for solving large scale soil and water management problems. This will also allow identifying research needs in the interdisciplinary domain of modelling and monitoring and to improve the integration of unsaturated zone science in solving soil and water management issues. A focus will be given on examples of large scale soil and water management problems in Europe.

  2. EFFICIENCY OF SOIL CORE AND SOIL-PORE WATER SAMPLING SYSTEMS

    EPA Science Inventory

    A laboratory column and field lysimeter study were conducted to evaluate the efficiency of soil core and soil-pore water samples to detect the migration of the organic components of land treated wastes through soil. In the laboratory, column leaching studies were performed by pac...

  3. Erosion effects on water and DOC/DIC fluxes in soils from a hummocky ground moraine landscape

    NASA Astrophysics Data System (ADS)

    Herbrich, Marcus; Gerke, Horst H.; Sommer, Michael

    2015-04-01

    In the arable hummocky ground moraine soil landscape, an erosion-induced spatial differentiation of soil types can be observed. Unknown is how the water flow and solute transport is affected by soil-crop interactions depending on properties of differently-developed soil horizons. The objective was to analyze these interactions and by comparing lysimeter-based measured water and solute balances for Luvisol soil monoliths extracted from differently-eroded slope locations. For a 3-years measurement period, differences in cumulative seepage water drainage of more than 76 % were observed between most and least eroded Luvisol. Although the soil types were identical, these data indicated characteristic erosion-induced spatial differentiation in the water balance of the landscape. Because the concentrations of dissolved organic carbon (DOC) and of dissolved inorganic carbon (DIC) were relatively similar for all lysimeters at the bottom (1.4 m soil depth), the DOC/DIC leaching was dominated by differences in water fluxes in this observation period (04/2011-04/2014). Results suggest that water and solute balances are depending on the degree of erosion-induced soil profile modifications. Hence for the landscape scale analysis of the landscape water and solute balances, not only the distributed soil types but also erosion-induced modifications with a single soil type should be considered.

  4. Automated soil water balance sensing: From layers to control volumes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Continuous sensing of soil water status has been possible in some ways since the advent of chart recorders, but the widespread adoption of soil water sensing systems did not occur until relatively inexpensive dataloggers became available in the late 1970s and early 1980s. Early systems relied on pre...

  5. Comparison of corn transpiration, eddy covariance, and soil water loss

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Stem flow gages are used to estimate plant transpiration, but only a few studies compare transpiration with other measures of soil water loss. The purpose of this study was to compare transpiration from stem flow measurements with soil water changes estimated by daily neutron probe readings. Monitor...

  6. Soil and Water Challenges for Pacific Northwest Agriculture

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil and water conservation has been a major concern in the Inland Pacific Northwest since the onset of farming 125 years ago. Some of the highest historic water erosion rates in the USA have occurred on steep slopes in the Palouse region where soil loss averaged 45 Mg ha-1 yr-1 and could reach 450 ...

  7. Coupled Oxygen and Hydrogen Isotope Analysis of Water Along the Soil-Plant- Atmosphere Continuum

    NASA Astrophysics Data System (ADS)

    Huang, Z.; Webb, E. A.; Longstaffe, F. J.

    2008-12-01

    The oxygen and hydrogen isotope compositions of water within a plant vary with transpiration rates and the isotopic composition of soil water. Both of these parameters are affected by temperature and relative humidity. A controlled-temperature, growth-chamber experiment was conducted to determine the relationships among temperature, relative humidity, soil water evaporation and plant-water isotope composition in cattails and horsetails. Typha, a cattail species that grows in wetland conditions, and Equisetum, a horsetail species that prefers dry soils, were each grown in four chambers at 15, 20, 25 and 30 degrees Celsius. The oxygen and hydrogen isotope compositions of watering water, soil water, vapour in the growth chambers and plant water from the leaves and stems were analyzed throughout the eight-month long artificial growing season. Although the oxygen isotope composition of the watering water remained constant, the soil water, atmospheric vapour and plant water were progressively enriched in oxygen-18 and deuterium in each of the four chambers from low to high temperatures as a result of increasing evaporation. The oxygen isotope composition of plant water along the length of a single stem or leaf was increasingly enriched in the heavier isotopes towards the apex. There was no significant difference in the magnitude of this trend between species. These results indicate that the isotopic composition of plant water is primarily controlled by environmental conditions. The oxygen isotope composition of the water vapour in the growing chamber increased with temperature, consistent with equilibration between the vapour and the oxygen-18 enriched soil and plant water reservoirs. The magnitude and interaction of these variables, as measured for these modern samples of cattails and horsetails, should be useful in calibrating paleoclimate proxies based on fossilized plant materials (e.g., cellulose, phytoliths).

  8. Improving Water Quality and Conserving Soil Using Soil Amendments.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Conservation tillage such a no-tillage has widely been shown to control soil erosion compared to other forms of management that involved some extent of tillage. However, in no-tillage most if not all the chemicals are placed near or on the soil surface which makes their movement more likely to occu...

  9. Rhizosphere: a leverage for tolerance to water deficits of soil microflora ?

    NASA Astrophysics Data System (ADS)

    Bérard, Annette; Ruy, Stéphane; Coronel, Anaïs; Toussaint, Bruce; Czarnes, Sonia; Legendre, Laurent; Doussan, Claude

    2015-04-01

    Microbial soil communities play a fundamental role in soil organic matter mineralization, which is a key process for plant nutrition, growth and production in agro-ecosystems. A number of these microbial processes take place in the rhizosphere: the soil zone influenced by plant roots activity, which is a "hotspot " of biological and physico-chemical activity, transfers and biomass production. The knowledge of rhizosphere processes is however still scanty, especially regarding the interactions between physico-chemical processes occurring there and soil microorganisms. The rhizosphere is a place where soil aggregates are more stable, and where bulk density, porosity, water and nutrients transfer are modified with respect to the bulk soil (e.g. because of production of mucilage, of which exo-polysaccharides (EPS) produced by roots and microorganisms. During a maize field experiment, rhizospheric soil (i.e. soil strongly adhering to maize roots) and bulk soil were sampled twice in spring and summer. These soil samples were characterized for physicochemical parameters (water retention curves and analysis of exopolysaccarides) and microflora (microbial biomass, catabolic capacities of the microbial communities assessed with the MicroRespTM technique, stability of soil microbial respiration faced to a heat-drought disturbance). We observed differences between rhizospheric and bulk soils for all parameters studied: Rhizospheric soils showed higher microbial biomasses, higher quantities of exopolysaccarides and a higher water retention capacity compared to bulk soil measurements. Moreover, microbial soil respiration showed a higher stability confronted to heat-drought stress in the rhizospheric soils compared to bulk soils. Results were more pronounced during summer compared to spring. Globally these data obtained from field suggest that in a changing climate conditions, the specific physico-biological conditions in the rhizosphere partially linked to exopolysaccarides

  10. Iron clad wetlands: Soil iron-sulfur buffering determines coastal wetland response to salt water incursion

    NASA Astrophysics Data System (ADS)

    Schoepfer, Valerie A.; Bernhardt, Emily S.; Burgin, Amy J.

    2014-12-01

    Coastal freshwater wetland chemistry is rapidly changing due to increased frequency of salt water incursion, a consequence of global change. Seasonal salt water incursion introduces sulfate, which microbially reduces to sulfide. Sulfide binds with reduced iron, producing iron sulfide (FeS), recognizable in wetland soils by its characteristic black color. The objective of this study is to document iron and sulfate reduction rates, as well as product formation (acid volatile sulfide (AVS) and chromium reducible sulfide (CRS)) in a coastal freshwater wetland undergoing seasonal salt water incursion. Understanding iron and sulfur cycling, as well as their reduction products, allows us to calculate the degree of sulfidization (DOS), from which we can estimate how long soil iron will buffer against chemical effects of sea level rise. We show that soil chloride, a direct indicator of the degree of incursion, best predicted iron and sulfate reduction rates. Correlations between soil chloride and iron or sulfur reduction rates were strongest in the surface layer (0-3 cm), indicative of surface water incursion, rather than groundwater intrusion at our site. The interaction between soil moisture and extractable chloride was significantly related to increased AVS, whereas increased soil chloride was a stronger predictor of CRS. The current DOS in this coastal plains wetland is very low, resulting from high soil iron content and relatively small degree of salt water incursion. However, with time and continuous salt water exposure, iron will bind with incoming sulfur, creating FeS complexes, and DOS will increase.

  11. Using Ethanol to Investigate Dynamic Soil Water Repellency

    NASA Astrophysics Data System (ADS)

    Smith, James E.; Beatty, Sarah M.

    2016-04-01

    Large gaps remain in our fundamental understanding of the behaviour of water in dynamically repellent soils. By investigating these systems using other miscible fluids that minimize or eliminate repellency, e.g. ethanol, we seek to better understand and quantify soil water repellency. The advantages of the enhanced wettability of water repellent soils to other miscible fluids, however, come with complications including shifts in effective pore water pressures induced through variable interfacial tensions as well as differences in fluid mobility due to variable fluid viscosities and densities. With these considerations in mind, we compare and contrast the observed behaviours of fluid infiltration and retention in dynamically hydrophobic soils and hydrophilic soils. We conducted field and laboratory studies using tension disc infiltrometers along with water and ethanol solutions to investigate dynamic repellency in post-wildfire soils from Northern Ontario, Canada. Tension infiltrometers maintain a constant negative liquid pressure at the surface which proved to be useful for isolating wettable behaviours sensitive to dynamic changes in wettability. We present the data and system conceptualised and explained through contact angle dynamics and variable fractional wettability of the soil. The limitations of extending hydrophilic concepts and hydraulic functions to hydrophobic soils are discussed along with persistent challenges to advance our ability to simulate and predict system behaviours in naturally occurring water repellent soils.

  12. Exploring functional relationships between post-fire soil water repellency, soil structure and physico-chemical properties

    NASA Astrophysics Data System (ADS)

    Quarfeld, Jamie; Brook, Anna; Keestra, Saskia; Wittenberg, Lea

    2016-04-01

    Soil water repellency (WR) and aggregate stability (AS) are two soil properties that are typically modified after burning and impose significant influence on subsequent hydrological and geomorphological dynamics. The response of AS and soil WR to fire depends upon how fire has influenced other key soil properties (e.g. soil OM, mineralogy). Meanwhile, routine thinning of trees and woody vegetation may alter soil properties (e.g. structure and porosity, wettability) by use of heavy machinery and species selection. The study area is situated along a north-facing slope of Mount Carmel national park (Israel). The selected sites are presented as a continuum of management intensity and fire histories. To date, the natural baseline of soil WR has yet to be thoroughly assessed and must be investigated alongside associated soil aggregating parameters in order to understand its overall impact. This study examines (i) the natural baseline of soil WR and physical properties compared to those of disturbed sites in the immediate (controlled burn) and long-term (10-years), and (ii) the interactions of soil properties with different control factors (management, surface cover, seasonal-temporal, burn temperature, soil organic carbon (OC) and mineralogy) in Mediterranean calcareous soils. Analysis of surface soil samples before and after destruction of WR by heating (200-600°C) was implemented using a combination of traditional methods and infrared (IR) spectroscopy. Management and surface cover type conditioned the wettability, soil structure and porosity of soils in the field, although this largely did not affect the heat-induced changes observed in the lab. A positive correlation was observed along an increasing temperature gradient, with relative maxima of MWD and BD reached by most soils at the threshold of 400-500°C. Preliminary analyses of soil OC (MIR) and mineralogical composition (VIS-NIR) support existing research regarding: (i) the importance of soil OC quality and

  13. Soil permeability as a function of vegetation type and soil water content

    SciTech Connect

    Morris, R.C.; Fraley, L. Jr.

    1994-06-01

    Soil permeability is important for estimating the rate of mass transport of {sup 222}Rn through soils and into basements. We measured permeability and soil water content on a set of nine plots consisting of three plots vegetated with common barley (Hordeum vulgare), three plots vegetated with Russian thistle (Salsola kali), and three bare plots. Soil moisture was consistently highest on the bare plots and lowest on the Russian thistle plots. Plots with vegetation had lower soil water content during the growing season. Permeability was consistently higher on Russian thistle plots. ANOVA showed that both soil water content and presence of Russian thistle had a significant impact on permeability but that presence of barley did not. The effect of vegetation and moisture on permeability may have significant effects on {sup 222}Rn transport in soils. 18 refs., 8 figs., 1 tab.

  14. Water-module interaction studies

    NASA Technical Reports Server (NTRS)

    Mon, G.; Wen, L.; Ross, R., Jr.

    1988-01-01

    Mechanisms by which moisture enters photovoltaic modules and techniques for reducing such interactions are reported. Results from a study of the effectiveness of various module sealants are given. Techniques for measuring the rate and quantity of moisture ingress are discussed. It is shown that scribe lines and porous frit bridging conductors provide preferential paths for moisture ingress and that moisture diffusion by surface/interfacial paths is considerably more rapid than diffusion by bulk paths, which implies that thin-film substrate and supersubstrate modules are much more vulnerable to moist environments than are bulk-encapsulated crystalline-silicon modules. Design approaches that reduce moisture entry are discussed.

  15. Water-module interaction studies

    NASA Astrophysics Data System (ADS)

    Mon, G.; Wen, L.; Ross, R., Jr.

    Mechanisms by which moisture enters photovoltaic modules and techniques for reducing such interactions are reported. Results from a study of the effectiveness of various module sealants are given. Techniques for measuring the rate and quantity of moisture ingress are discussed. It is shown that scribe lines and porous frit bridging conductors provide preferential paths for moisture ingress and that moisture diffusion by surface/interfacial paths is considerably more rapid than diffusion by bulk paths, which implies that thin-film substrate and supersubstrate modules are much more vulnerable to moist environments than are bulk-encapsulated crystalline-silicon modules. Design approaches that reduce moisture entry are discussed.

  16. Beyond extreme temperatures: soil water supply and yield variability

    NASA Astrophysics Data System (ADS)

    Urban, D.; Lobell, D. B.

    2014-12-01

    Extreme weather events have profound consequences for both the mean and interannual variability of agricultural production, but while the role of extreme heat has been convincingly demonstrated, soil water supply has received less attention. In particular, there is debate over the extent to which damages attributed to extreme heat are confounded with drought conditions. In a pair of studies, we examine the effect of extreme moisture conditions, both wet and dry, on maize and soybean yields in the U.S. We find significant effects of waterlogging during the planting season, when crops are most vulnerable to excess moisture, as well as evidence for a strong interaction between high temperatures and low moisture during during the critical stages of the summer growing season. Using both precipitation and model-derived soil moisture data, our results suggest that considering temperature and moisture independently will underestimate yield damages during hot, dry conditions. Many warming scenarios project increases in both extreme summer temperatures and soil dryness, and considering these effects jointly can be important in estimating future yield variability.

  17. Quantification of the inevitable: the influence of soil macrofauna on soil water movement in rehabilitated open-cut mine land

    NASA Astrophysics Data System (ADS)

    Arnold, S.; Williams, E. R.

    2015-08-01

    Recolonisation of soil by macrofauna (especially ants and termites) in rehabilitated open-cut mine sites is inevitable. In these highly disturbed landscapes, soil invertebrates play a major role in soil development (macropore configuration, nutrient cycling, bioturbation, etc.) and can influence hydrological processes such as infiltration and seepage. Understanding and quantifying these ecosystem processes is important in rehabilitation design, establishment and subsequent management to ensure progress to the desired end-goal, especially in waste cover systems designed to prevent water reaching and transporting underlying hazardous waste materials. However, soil macrofauna are typically overlooked during hydrological modelling, possibly due to uncertainties on the extent of their influence, which can lead to failure of waste cover systems or rehabilitation activities. We propose that scientific experiments under controlled conditions are required to quantify (i) macrofauna - soil structure interactions, (ii) functional dynamics of macrofauna taxa, and (iii) their effects on macrofauna and soil development over time. Such knowledge would provide crucial information for soil water models, which would increase confidence in mine waste cover design recommendations and eventually lead to higher likelihood of rehabilitation success of open-cut mining land.

  18. Crop water stress indices correlated with soil water storage: Implications for variable rate irrigation management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water sensing methods are now coming to be used for irrigation scheduling of whole fields. However, newly introduced variable rate irrigation (VRI) systems require information about soil water content in many areas of a field, each called an irrigation management zone. Commonly available soil w...

  19. Fate and transport of the β-adrenergic agonist ractopamine hydrochloride in soil-water systems.

    PubMed

    Hakk, Heldur; Shelver, Weilin L; Casey, Francis X M

    2016-07-01

    The feed additive ractopamine hydrochloride was fortified at four concentrations into batch vials containing soils that differed in both biological activity and organic matter (OM). Sampling of the liquid layer for 14days demonstrated that ractopamine rapidly dissipated from the liquid layer. Less than 20% of the fortified dose remained in the liquid layer after 4hr, and recoveries of dosed ractopamine ranged from 8 to 18% in the liquid layer at 336hr. Sorption to soil was the major fate for ractopamine in soil:water systems, i.e., 42%-51% of the dose at 14days. The major portion of the sorbed fraction was comprised of non-extractables; a smaller fraction of the sorbed dose was extracted into water and acetone, portions which would be potentially mobile in the environment. Partitioning coefficients for all soils suggested strong sorption of ractopamine to soil which is governed by hydrophobic interactions and cation exchange complexes within the soil OM. Ractopamine degradation was observed, but to mostly non-polar compounds which had a higher potential than ractopamine to sorb to soil. The formation of volatiles was also suggested. Therefore, despite rapid and extensive soil sorption, these studies indicated a portion of ractopamine, present in manures used to fertilize soils, may be mobile in the environment via water-borne events. PMID:27372117

  20. Soil water availability as controlling factor for actual evapotranspiration in urban soil-vegetation-systems

    NASA Astrophysics Data System (ADS)

    Thomsen, Simon; Reisdorff, Christoph; Gröngröft, Alexander; Jensen, Kai; Eschenbach, Annette

    2015-04-01

    The City of Hamburg is characterized by a large number of greens, parks and roadside trees: 600.000 trees cover about 14% of the city area, and moreover, 245.000 roadside trees can be found here. Urban vegetation is generally known to positively contribute to the urban micro-climate via cooling by evapotranspiration (ET). The water for ET is predominantly stored in the urban soils. Hence, the actual evapotranspiration (ETa) is - beside atmospheric drivers - determined by soil water availability at the soil surface and in the rooting zones of the respective vegetation. The overall aim of this study is to characterize soil water availability as a regulative factor for ETa in urban soil-vegetation systems. The specific questions addressed are: i) What is the spatio-temporal variation in soil water availability at the study sites? ii) Which soil depths are predominantly used for water uptake by the vegetation forms investigated? and iii) Which are the threshold values of soil water tension and soil water content (Θ), respectively, that limit ETa under dry conditions on both grass-dominated and tree-dominated sites? Three study areas were established in the urban region of Hamburg, Germany. We selected areas featuring both single tree stands and grass-dominated sites, both representing typical vegetation forms in Hamburg. The areas are characterized by relatively dry soil conditions. However, they differ in regard to soil water availability. At each area we selected one site dominated by Common Oak (Quercus ruber L.) with ages from 40 to 120 years, and paired each oak tree site with a neighboring grass-dominated site. All field measurements were performed during the years 2013 and 2014. At each site, we continuously measured soil water tension and Θ up to 160 cm depth, and xylem sap flux of each of three oak trees per site in a 15 min-resolution. Furthermore, we measured soil hydraulic properties as pF-curve, saturated and unsaturated conductivity at all sites

  1. The soil water regime of stony soils in a mountain catchment

    NASA Astrophysics Data System (ADS)

    Hlaváčiková, Hana; Danko, Michal; Holko, Ladislav; Hlavčo, Jozef; Novák, Viliam

    2016-04-01

    Investigation of processes related to runoff generation is an important topic in catchment hydrology. Observations are usually carried out in small catchments or on hillslopes. Many of such catchments are located in mountain or forested areas. From many studies it is evident that soil conditions and soil characteristics are one of the crucial factors in runoff generation. Mountainous or forest soils have usually high rock fragments content. Nevertheless, the influence of soil stoniness on water flow was not sufficiently studied up to now at catchment and hillslope scales due to flow formation complexity or problems with stony soil properties measurement (installing measuring devices, interpretation of measured data). Results of this work can be divided in two groups: (1) hydrophysical properties of stony soils measurements, and (2) water flow dynamic modelling in stony soils. Properties of stony soils were measured in the Jalovecky creek catchment, the Western Tatra Mts., Slovakia. Altitude of particular study sites varies from 780 to1500 m a.s.l. We measured and analyzed the stoniness of reference soil profiles, as well as retention properties of stony soils (fine soil fraction and rock fragments separately) and hydraulic conductivities of surface and subsurface soil layers. The methodology for determination of the effective hydrophysical properties of a stony soil (later used in modelling) was proposed using results from measurements, calculation, and numerical Darcy experiments. Modelling results show that the presence of rock fragments with low water retention in a stony soil with moderate or high stoniness can cause the soil water storage decrease by 16-31% in compared to the soil without rock fragments. In addition, decreased stony soil retention capacity resulted in faster outflow increase at the bottom of the soil profile during non-ponding infiltration. Furthermore, the presence of rock fragments can increase maximum outflow value. It is not possible to

  2. The "Teflon basin" myth: Snow-soil interactions in mountain catchments in the western US

    NASA Astrophysics Data System (ADS)

    Williams, M. W.; Cowie, R. M.

    2015-12-01

    In much of western North America, snow and snowmelt provide the primary means for storage of winter precipitation, effectively transferring water from the relatively wet winter season to the typically dry summers. A common assumption is that high-elevation catchments in the western United States behave like "Teflon basins" and that water released from seasonal storage in snow packs flows directly into streams with little or no interaction with underlying soils. Here I present information from a variety of catchments in the Colorado Front Range on snowmelt/soil interactions using isotopic, geochemical, nutrient and hydrometric data in 2- and 3- component hydrograph separations, along with end-member mixing analysis (EMMA). For most catchments we measured these parameters in weekly precipitation, the seasonal snowpack, snowmelt before contact with the ground, discharge, springs, soil solution, and groundwater. We ran EMMA at the catchment scale for catchments that represent the rain-snow transition zone in the montane forest, the seasonally snow covered sub-alpine to alpine transition zone, and a high-elevation alpine zone near the continental divide. In all catchments three end-members were the source waters for about 95% of discharge. Two end-members were the same in all catchments, snow and groundwater. For the alpine catchment talus springs was the third water source, while rain was the third water source in the two lower-elevation catchments. For all three catchments, soil solution plotted with stream waters along or near a line connecting the snow and groundwater end-members. Thus, for seasonally snow-covered catchments from montane to alpine ecosystems, snowmelt infiltrates underlying soils before snowmelt recharges groundwater reservoirs and contributes to surface flows. Seasonally snow-covered catchments are not Teflon basins. Rather, snowmelt infiltrates soils where solute concentrations are changed by biological and geochemical processes.

  3. Impact of particle nanotopology on water transport through hydrophobic soils.

    PubMed

    Truong, Vi Khanh; Owuor, Elizabeth A; Murugaraj, Pandiyan; Crawford, Russell J; Mainwaring, David E

    2015-12-15

    The impact of non- and poorly wetting soils has become increasingly important, due to its direct influence on the water-limited potential yield of rain-fed grain crops at a time of enhanced global competition for fresh water. This study investigates the physical and compositional mechanisms underlying the influence of soil organic matter (SOM) on the wetting processes of model systems. These model systems are directly related to two sandy wheat-producing soils that have contrasting hydrophobicities. Atomic force microscopy (AFM), contact angle and Raman micro-spectroscopy measurements on model planar and particulate SOM-containing surfaces demonstrated the role of the hierarchical surface structure on the wetting dynamics of packed particulate beds. It was found that a nanoscale surface topology is superimposed over the microscale roughness of the packed particles, and this controls the extent of water ingress into particulate packed beds of these particles. Using two of the dominant component organic species found in the SOM of the two soils used in this study, it was found that the specific interactions taking place between the SOM components, rather than their absolute quantities, dictated the formation of highly hydrophobic surface nanotopologies. This hydrophobicity was demonstrated, using micro-Raman imaging, to arise from the surface being in a composite Cassie-Baxter wetting state. Raman imaging demonstrated that the particle surface nanotopography influenced the degree of air entrapment in the interstices within the particle bed. The influence of a conventional surfactant on the wetting kinetics of both the model planar surfaces and packed particulate beds was quantified in terms of their respective advancing contact angles and the capillary wetting force vector. The information obtained for all of the planar and particulate surfaces, together with that obtained for the two soils, allowed linear relationships to be obtained in plots of the contact angle

  4. Seasonal variation of water level, water and soil temperature, chemistry, and stable isotopes in hyporheic zone of Korea

    NASA Astrophysics Data System (ADS)

    Jeon, W. H.; Lee, J. Y.

    2015-12-01

    The purpose of study was to evaluate interaction between groundwater and stream water in hyporheic zone using water level, water temperature, soil temperature, chemistry, and stable isotopes. We installed seven piezometers (IYHW1 to 7) in the streambed that across stream in every 10 m and in depth of 0.85 to 1.54 m, a device that measure stage level nearby IYHW1, and devices that measure soil temperature in every 10 cm down to 50 cm nearby each piezometer was installed. We monitored water level and water temperature every hour from automatic transducers at the piezometers and the stage level, and soil temperatures were monitored every two hours. We took samples from the hyporheic water, stream water, and nearby groundwater to analysis chemical and isotopic compositions. The water level difference between stream water and hyporheic waters indicated that groundwater was downwelling in wet season and upwelling in dry season. The groundwater temperature remained steady in different seasons, but the stream water represented a frequent fluctuation with large amplitude. The hyporheic waters and soil temperature represented intermediate variation characteristics. The chemical compositions were not able to indicate in interaction of groundwater and stream water because no distinctive difference in seasonal variation in waters. The quantity of isotopic compositions of oxygen and hydrogen determined from using mixing ratio indicated that downwelling in wet season and upwelling in dry season. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education (NRF-2011-0007232).

  5. The relationship between water content and swelling parameters of soils

    NASA Astrophysics Data System (ADS)

    Samet Öngen, Ali; Abiddin Ergüler, Zeynal

    2016-04-01

    The level of swelling dependent damages of low-rising engineering structures constructed on and/or in unsaturated zone of soil deposits is generally controlled by mineralogical compositions and water content of soils. It is well known that seasonal or even daily variations in water content causes volumetric changes within unsaturated zone of a soil composed mainly of swelling type clay minerals. In this regard, in addition to mineralogical composition of soils, water content should be considered as another major factor for understanding swelling behavior of soils. It can be concluded from literature review that swelling parameters of soils were determined by performing experimental studies on dry samples or samples having natural water content without incorporating seasonal continuous variations in water content. Thus, the effect of variation in water content on swelling mechanism of soils is not yet sufficiently studied in previous studies. For achieving accurate understanding of swelling behavior at field conditions, a new approach is required to identify swelling parameter at different initial water content. For this purpose, a comprehensive study was performed to investigate the effect of water content on swelling behavior of soils and to find a new parameter for assessing swelling parameters of samples prepared at different initial water content conditions. Based on main objectives of this study, soil samples having wide range in terms of grain size distributions, mineralogical compositions and Atterberg limits were collected from different locations in Turkey. To minimize the effect of dry unit weight on swelling behavior of soils, samples were prepared at the same dry unit weight (14.6 kN/m3) and different initial water contents. It was determined that there is a linear relationship between initial water content and swelling parameters, and swelling parameters decrease with increasing initial water content conditions. By utilizing this relationship, a new

  6. Volatilization of lindance from water in soil-free and flooded soil systems.

    PubMed

    Siddaramppa, R; Sethunathan, N

    1976-01-01

    Volatilization of 14C-lindane from water in planchets and under flooded soil ecosystem was investigated. Lindane disappeared faster than parathion from planchets. More rapid loss of both insecticides occurred from water than from chloroform. Loss of lindane and parathion was related to measured losses of water by evaporation. During 5-day incubation under flooded soil conditions, disappearance of lindane was faster from open vials than from sealed vials, whereas in nonflooded soil, no volatile loss of the insecticide was evident despite water evaporation. Over 5 day incubation under flooded conditions, greater volatile loss of lindane occurred in sandy soil than in alluvial soil apparanetly due to greater adsorption to the soil colloids decreasing the insecticide concentration in the standing water on the laterite soil. Under identical conditions of water evaporation, lindane loss was directly proportional to its initial concentration in the water. These results suggest that considerable loss of soil applied pesticides can occur by volatilization from the standing water in flooded rice fields, particularly under tropical conditions. PMID:57974

  7. EVALUATION OF SOIL WATER RETENTION MODELS BASED ON BASIC SOIL PHYSICAL PROPERTIES

    EPA Science Inventory

    Algorithms to model soil water retention are needed to study the response of vegetation and hydrologic systems to climate change. he objective of this study was to evaluate some soil water retention models to identify minimum input data requirements. ix models that function with ...

  8. Wood chip mulch thickness effects on soil water, soil temperature, weed growth, and landscape plant growth

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Wood chip mulches are used in landscapes to reduce soil water evaporation and competition from weeds. A study was conducted over a three-year period to determine soil water content at various depths under four wood chip mulch treatments and to evaluate the effects of wood chip thickness on growth of...

  9. Soil surfactant products for improving hydrologic function in post-fire water repellent soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    There are a wide range of soil surfactant chemistries on the market today that are primarily designed for the treatment of water repellent soils in cropping and turfgrass systems. These chemicals may also have potential in treating the deleterious effects associated with post-fire water repellent so...

  10. How can climate, soil, and monitoring schedule affect temporal stability of soil water contents

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Temporal stability (TS) of soil water content (SWC) reflects the spatio-temporal organization of soil water. The TS SWC was originally recognized as a phenomenon that can be used to provide temporal average SWC of an area of interest from observations at a representative location(s). Currently appli...

  11. Genotypic Diversity of Escherichia coli in the Water and Soil of Tropical Watersheds in Hawaii ▿

    PubMed Central

    Goto, Dustin K.; Yan, Tao

    2011-01-01

    High levels of Escherichia coli were frequently detected in tropical soils in Hawaii, which present important environmental sources of E. coli to water bodies. This study systematically examined E. coli isolates from water and soil of several watersheds in Hawaii and observed high overall genotypic diversity (35.5% unique genotypes). In the Manoa watershed, fewer than 9.3% of the observed E. coli genotypes in water and 6.6% in soil were shared between different sampling sites, suggesting the lack of dominant fecal sources in the watershed. High temporal variability of E. coli genotypes in soil was also observed, which suggests a dynamic E. coli population corresponding with the frequently observed high concentrations in tropical soils. When E. coli genotypes detected from the same sampling events were compared, limited sharing between the soil and water samples was observed in the majority of comparisons (73.5%). However, several comparisons reported up to 33.3% overlap of E. coli genotypes between soil and water, illustrating the potential for soil-water interactions under favorable environmental conditions. In addition, genotype accumulation curves for E. coli from water and soil indicated that the sampling efforts in the Manoa watershed could not exhaust the overall genotypic diversity. Comparisons of E. coli genotypes from other watersheds on Oahu, Hawaii, identified no apparent grouping according to sampling locations. The results of the present study demonstrate the complexity of using E. coli as a fecal indicator bacterium in tropical watersheds and highlight the need to differentiate environmental sources of E. coli from fecal sources in water quality monitoring. PMID:21515724

  12. Soil water characteristics of two soil catenas in Illinois: Implications for irrigation

    SciTech Connect

    Schaetzl, R.J. ); Kirsch, S.W. ); Hendrie, L.K.

    1989-10-01

    Soil water was monitored by neutron scattering in six soils, three each within two drainage catenas in east-central Illinois, over a 15-month time span. The prairie soils have formed in: (1) 76-152 cm of silt loam, eolian sediments (loess) over glacial till (Catlin-Flanagan-Drummer catena), and (2) loess greater than 152 cm in thickness (Tama-Ipava-Sable catena). The authors characterized the water content of these soils over the total time span and for wet and dry climatic subsets, as an aid to potential irrigation decisions. Soils of the thin loess, C-F-D catena dried out to lower water contents and had greater soil water variability than did the thick loess soils. Under wet conditions, soil water contents in the two catenas were quite similar. Alleviation of surface and subsurface drying via irrigation would thus be more advantageous to yields on the C-F-D soils than on the T-I-S soils.

  13. Cooperative water-SOM interactions derived from the organic compound effect on SOM hydration

    NASA Astrophysics Data System (ADS)

    Borisover, Mikhail

    2014-05-01

    Interactions of water molecules with soil organic matter (SOM) may affect the ability of SOM to participate in multiple physical, chemical and biological processes. Specifically, water-SOM interactions may have a profound effect on interactions of organic compounds with SOM which is often considered as a major natural sorbent controlling the environmental fate of organic pollutants in the soil environment. Quantification of water - SOM interactions may be carried out by using water vapor sorption isotherms. However, water sorption isotherms providing macroscopic thermodynamic data do not allow examining water-SOM interactions on a microenvironment scale. The examination of water-SOM interactions in a local SOM environment may be carried out by determining the response of the SOM hydration to sorption of probe organic compounds. Recently, the model-free approach was proposed which allows quantifying effects of sorbing organic molecules on water - SOM interactions, by using relatively more available data on the effect of water activity on organic compound - SOM interactions. Therefore, this thermodynamic approach was applied to the experimental data describing sorption of organic compounds by SOM, both from the vapor and liquid phases, at various water activities. Hence, the response of water interactions with the model SOM materials such as a humic acid and an organic matter-rich peat soil to the presence of various organic sorbates was evaluated. Depending on a molecular structure of organic sorbates probing various molecular environments in SOM, the SOM-bound water may be driven in or out of the SOM sorbents. Organic compounds containing the atoms of oxygen, nitrogen or sulfur and preferring a relatively "polar" SOM microenvironment demonstrate the distinct enhancing effect on water-SOM interactions. In contrast, the "low-polarity" organic compounds, e.g., hydrocarbons or their halogen-substituted derivatives, produce a weakening effect on water-SOM interactions

  14. Modelling and simulation of explosions in soil interacting with deformable structures

    NASA Astrophysics Data System (ADS)

    Zakrisson, Björn; Häggblad, Hans-Áke; Jonsén, Pär

    2012-12-01

    A detonating explosive interacting with a deformable structure is a highly transient and non-linear event. In field blast trials of military vehicles, a standard procedure is often followed in order to reduce the uncertainties and increase the quality of the test. If the explosive is buried in the ground, the state of the soil must meet specific demands. In the present work, laboratory experiments have been performed to characterize the behaviour of a soil material. Soil may be considered a three-phase medium, consisting of solid grains, water and air. Variations between the amounts of these phases affect the mechanical properties of the soil. The experimental outcome has formed input data to represent the soil behaviour included in a three-phase elastic-plastic cap model. This unified constitutive model for soil has been used for numerical simulations representing field blast trials, where the explosive load is interacting with a deformable structure. The blast trials included explosive buried at different depths in wet or dry sand. A dependence of the soil initial conditions can be shown, both in the past field trials along with the numerical simulations. Even though some deviations exist, the simulations showed in general acceptable agreement with the experimental results.

  15. Fractal behavior of soil water storage at multiple depths

    NASA Astrophysics Data System (ADS)

    Ji, Wenjun; Lin, Mi; Biswas, Asim; Si, Bing C.; Chau, Henry W.; Cresswell, Hamish P.

    2016-08-01

    Spatiotemporal behavior of soil water is essential to understand the science of hydrodynamics. Data intensive measurement of surface soil water using remote sensing has established that the spatial variability of soil water can be described using the principle of self-similarity (scaling properties) or fractal theory. This information can be used in determining land management practices provided the surface scaling properties are kept at deep layers. The current study examined the scaling properties of sub-surface soil water and their relationship to surface soil water, thereby serving as supporting information for plant root and vadose zone models. Soil water storage (SWS) down to 1.4 m depth at seven equal intervals was measured along a transect of 576 m for 5 years in Saskatchewan. The surface SWS showed multifractal nature only during the wet period (from snowmelt until mid- to late June) indicating the need for multiple scaling indices in transferring soil water variability information over multiple scales. However, with increasing depth, the SWS became monofractal in nature indicating the need for a single scaling index to upscale/downscale soil water variability information. In contrast, all soil layers during the dry period (from late June to the end of the growing season in early November) were monofractal in nature, probably resulting from the high evapotranspirative demand of the growing vegetation that surpassed other effects. This strong similarity between the scaling properties at the surface layer and deep layers provides the possibility of inferring about the whole profile soil water dynamics using the scaling properties of the easy-to-measure surface SWS data.

  16. Citrus orchards management and soil water repellency in Eastern Spain

    NASA Astrophysics Data System (ADS)

    Cerdà, A.; González Peñaloza, F. A.; Jordán, A.; Zavala, L. M.

    2012-04-01

    Water repellent soils are found around the world, although originally was found on fire affected soil (DeBano, 1981). However, for decades, water repellency was found to be a rare soil property. One of the pioneer research that shown that water repellency was a common soil property is the Wander (1949) publication in Science. Wander researched the water repellency on citrus groves, and since then, no information is available about the water repellency on citrus plantations. The Mediterranean soils are prone to water repellency due to the summer dry conditions (Cerdà and Doerr, 2007). And Land Use and Land Management are key factors (Harper et al., 2000; Urbanek et al., 2007) to understand the water repellency behaviour of agriculture soils. Valencia region (Eastern Spain) is the largest exporter in the world and citrus plantations located in the alluvial plains and fluvial terraces are moving to alluvial fans and slopes where the surface wash is very active (Cerdà et al., 2009). This research aims to show the water repellency on citrus orchards located on the sloping terrain (< 15 % angle slope). Measurement were conducted in four experimental plots located in the Canyoles River watershed to assess the soil water repellency in citrus orchards under different managements: annual addition of plant residues and manure with no tilling and no fertilizer (MNT), annual addition of plant residues with no tillage (NT), application of conventional herbicides and no tilling (HNT) and conventional tillage in June (CT). The period for each type of management ranged from 2 and 27 (MNT), 1 and 25 (NT), 2 and 27 (HNT) and 3 and 29 years (CT). At each plot, a ten points were selected every 10 cm along inter-rows and water drop penetration time test (WDTP; DeBano, 1981) was performed. The results show that the MNT treatment induced slight water repellency in citrus-cropped soils compared to other treatments. Small but significant soil water repellency was observed under NT and HNT

  17. Estimation of water saturated permeability of soils, using 3D soil tomographic images and pore-level transport phenomena modelling

    NASA Astrophysics Data System (ADS)

    Lamorski, Krzysztof; Sławiński, Cezary; Barna, Gyöngyi

    2014-05-01

    There are some important macroscopic properties of the soil porous media such as: saturated permeability and water retention characteristics. These soil characteristics are very important as they determine soil transport processes and are commonly used as a parameters of general models of soil transport processes used extensively for scientific developments and engineering practise. These characteristics are usually measured or estimated using some statistical or phenomenological modelling, i.e. pedotransfer functions. On the physical basis, saturated soil permeability arises from physical transport processes occurring at the pore level. Current progress in modelling techniques, computational methods and X-ray micro-tomographic technology gives opportunity to use direct methods of physical modelling for pore level transport processes. Physically valid description of transport processes at micro-scale based on Navier-Stokes type modelling approach gives chance to recover macroscopic porous medium characteristics from micro-flow modelling. Water microflow transport processes occurring at the pore level are dependent on the microstructure of porous body and interactions between the fluid and the medium. In case of soils, i.e. the medium there exist relatively big pores in which water can move easily but also finer pores are present in which water transport processes are dominated by strong interactions between the medium and the fluid - full physical description of these phenomena is a challenge. Ten samples of different soils were scanned using X-ray computational microtomograph. The diameter of samples was 5 mm. The voxel resolution of CT scan was 2.5 µm. Resulting 3D soil samples images were used for reconstruction of the pore space for further modelling. 3D image threshholding was made to determine the soil grain surface. This surface was triangulated and used for computational mesh construction for the pore space. Numerical modelling of water flow through the

  18. Water content and matric potential of soil under different soil frost conditions

    NASA Astrophysics Data System (ADS)

    Suzuki, S.; Iwata, Y.; Hiirota, T.; Hasegawa, S.; Arima, J.

    2006-12-01

    Eastern Hokkaido, where is one of the largest agricultural production regions in Japan, is characterized by low air temperature and relatively thin snow covers resulting in soil frost over the winter. However, the soil frost depth has been significantly decreasing since late 1980's due to an insulation from the cold air by a thick snow cover developing in early winter. In the current study, soil water movement under different soil frost conditions were monitored to obtain a knowledge of changes in hydraulic-regime of the agricultural production systems in the Eastern Hokkaido associated with the decreasing soil frost depth in the region. A paired soil plot experiment was conducted from Nov. 2005 to May 2006, where the frost depth was artificially enhanced by removing snow in the treatment plot and the natural condition was maintained in the control plot. The soil in the experimental field was classified as Andisol with much porosity and high drainability. In each plot, water content and matric potential were measured by TDR and thermally-insulated tensiometer, respectively. Changes in snow water equivalent volume (SWE) and soil-frost depth were manually recorded. The maximum soil-frost depth in the treatment and control plots resulted in 47 and 19 cm, respectively. In both plots, soil water content and matric potential in underlying unfrozen soil decreased with the progress of freezing front, and the direction of soil water flow between 90 and 100 cm changed from downward to upward after the onset of the soil freezing. It is of note that the matric potential at 90 cm in the treatment plot decreased down to -480 cm, while the matric potential at the same depth in the control plot was -200 cm at minimum. When the underlying unfrozen soil was most driest the soil water volume stored in a depth interval from 50 to 100 cm for the treatment and control plots was 189 and 212 mm, respectively. Further, the magnitude of upward hydraulic gradient between 90 and 100 cm in the

  19. Perchlorate levels in soil and waters from the Atacama Desert.

    PubMed

    Calderón, R; Palma, P; Parker, D; Molina, M; Godoy, F A; Escudey, M

    2014-02-01

    Perchlorate is an anion that originates as a contaminant in ground and surface waters. The presence of perchlorate in soil and water samples from northern Chile (Atacama Desert) was investigated by ion chromatography-electrospray mass spectrometry. Results indicated that perchlorate was found in five of seven soils (cultivated and uncultivated) ranging from 290 ± 1 to 2,565 ± 2 μg/kg. The greatest concentration of perchlorate was detected in Humberstone soil (2,565 ± 2 μg/kg) associated with nitrate deposits. Perchlorate levels in Chilean soils are greater than those reported for uncultivated soils in the United States. Perchlorate was also found in superficial running water ranging from 744 ± 0.01 to 1,480 ± 0.02 μg/L. Perchlorate water concentration is 30-60 times greater than levels established by the United States Environmental Protection Agency (24.5 μg/L) for drinking. PMID:24165784

  20. Effects of soil water availability on water fluxes in winter wheat

    NASA Astrophysics Data System (ADS)

    Cai, G.; Vanderborght, J.; Langensiepen, M.; Vereecken, H.

    2014-12-01

    Quantifying soil water availability in water-limited ecosystems on plant water use continues to be a practical problem in agronomy. Transpiration which represents plant water demand is closely in relation to root water uptake in the root zone and sap flow in plant stems. However, few studies have been concentrated on influences of soil moisture on root water uptake and sap flow in crops. This study was undertaken to investigate (i) whether root water uptake and sap flow correlate with the transpiration estimated by the Penman-Monteith model for winter wheat(Triticum aestivum), and (ii) for which soil water potentials in the root zone, the root water uptake and sap flow rates in crop stems would be reduced. Therefore, we measured sap flow velocities by an improved heat-balance approach (Langensiepen et al., 2014), calculated crop transpiration by Penman-Monteith model, and simulated root water uptake by HYDRUS-1D on an hourly scale for different soil water status in winter wheat. In order to assess the effects of soil water potential on root water uptake and sap flow, an average soil water potential was calculated by weighting the soil water potential at a certain depth with the root length density. The temporal evolution of root length density was measured using horizontal rhizotubes that were installed at different depths.The results showed that root water uptake and sap flow matched well with the computed transpiration by Penman-Monteith model in winter wheat when the soil water potential was not limiting root water uptake. However, low soil water content restrained root water uptake, especially when soil water potential was lower than -90 kPa in the top soil. Sap flow in wheat was not affected by the observed soil water conditions, suggesting that stomatal conductance was not sensitive to soil water potentials. The effect of drought stress on root water uptake and sap flow in winter wheat was only investigated in a short time (after anthesis). Further research

  1. Rock fragments induce patchy distribution of soil water repellency in burned soils

    NASA Astrophysics Data System (ADS)

    Gordillo-Rivero, Ángel; García-Moreno, Jorge; Bárcenas-Moreno, Gema; Jiménez-Morillo, Nicasio T.; Mataix-Solera, Jorge; Jordán, Antonio; Zavala, Lorena M.

    2013-04-01

    Forest fires are recurrent phenomena in the Mediterranean area and are one of the main causes of changes in the Mediterranean ecosystems, increasing the risk of soil erosion and desertification. Fire is an important agent which can induce important changes in the chemical and physical characteristics of soils. During wildfires, only a small part of the heat generated is transmitted to the first centimetres of the soil profile. The intensity of the changes produced in the physical and chemical characteristics of the soil depends on the temperatures reached at different soil depths, the time of residence of temperature peaks, and the stability of the different soil components. One of the soil physical properties strongly affected by fire is soil water repellency (WR). Depending on temperature, time of heating, type of soil and fuel, fire can induce, enhance or destroy soil WR. Soil WR is a key factor in controlling soil hydrology and water availability in burnt soils together with other factors as texture or aggregation. Although the occurrence and consequences of fire-induced soil WR have been deeply studied, some gaps still exist, as the influence of rock fragment cover during burning. During combustion of litter and aerial biomass, the soil surface under rock fragments is heated and reachs temperature peaks after a certain delay respect to exposed areas. In contrast, temperature peaks are longer, increasing the time of residence of high temperature. In consequence, rock fragments may change the expected spatial distribution of soil WR. Up to date, very scarce research concerns the effect of rock fragments at the soil surface on the fire-induced pattern of soil water repellency. METHODS Two experiments were carried out in this research. In the first case, an experiment was conducted in an experimental farm in Sevilla (southern Spain). The effect of a low severity prescribed fire was studied in soil plots under different rock fragment covers (0, 15, 30, 45 and 60

  2. Measuring Low Concentrations of Liquid Water in Soil

    NASA Technical Reports Server (NTRS)

    Buehler, Martin

    2009-01-01

    An apparatus has been developed for measuring the low concentrations of liquid water and ice in relatively dry soil samples. Designed as a prototype of instruments for measuring the liquidwater and ice contents of Lunar and Martian soils, the apparatus could also be applied similarly to terrestrial desert soils and sands. The apparatus is a special-purpose impedance spectrometer: Its design is based on the fact that the electrical behavior of a typical soil sample is well approximated by a network of resistors and capacitors in which resistances decrease and capacitances increase (and, hence, the magnitude of impedance decreases) with increasing water content.

  3. Spatial and temporal soil water variability in the plowing horizon of agriculturally used soils in two regions of Southwest Germany

    NASA Astrophysics Data System (ADS)

    Poltoradnev, Maxim; Ingwersen, Joachim; Streck, Thilo

    2015-04-01

    Soil water dynamics plays an important role in soil-plant-atmosphere interactions. There is a lack of long-term continuous measurements of topsoil water content at the regional scale. The objective of the present study was to quantify and elucidate the seasonal dynamics of spatial soil water content variability in the plowing horizon (Ap) of agricultural soils at the regional scale. The study was conducted in the central part of the Kraichgau and the Mid Swabian Alb in Southwest Germany. In each region a soil water network embracing 21 stations was set up. All stations were installed on cropped agricultural sites and distributed across three spatial domains: an inner domain 3 km × 3 km (5 stations), a middle 9 km × 9 km (8 stations), and an outer domain 27 km × 27 km (8 stations). Each station consists of a TDT sensor (SI.99 Aquaflex Soil Moisture Sensor, Streat Instruments Ltd, New Zealand), which senses both soil water content and soil temperature, a rain gauge, and a remote transfer unit (RTU, datalogger + GSM modem), which stores and transfers data via GPRS modem to the central data server (Adcon Telemetry GmbH, Austria) located at the University of Hohenheim. The TDT sensors were installed at 0.15 m depth. A sensor consists of a three meter long and three centimeter wide flat transmission line. The relationship between the standard deviation (σθ) of the soil water content (SWC) and mean spatial soil water content (<θ>) formed combinations of concave and convex hyperbolas. However, it strongly depended on SWC state and season. Generally, σθ was found to be changing along a convex trend during dry out and rewetting phases with a maximum in the intermediate SWC range. At the rain event scale, σθ(<θ>) was either ascending or converging with decreasing <θ>. A concave shape was observed when <θ> approached to dry state. The majority of σθ(<θ>) hysteresis loops were observed in intermediate and intermediate/wet state of SWC. All hysteretic loops were

  4. Biotic interactions mediate soil microbial feedbacks to climate change.

    PubMed

    Crowther, Thomas W; Thomas, Stephen M; Maynard, Daniel S; Baldrian, Petr; Covey, Kristofer; Frey, Serita D; van Diepen, Linda T A; Bradford, Mark A

    2015-06-01

    Decomposition of organic material by soil microbes generates an annual global release of 50-75 Pg carbon to the atmosphere, ∼7.5-9 times that of anthropogenic emissions worldwide. This process is sensitive to global change factors, which can drive carbon cycle-climate feedbacks with the potential to enhance atmospheric warming. Although the effects of interacting global change factors on soil microbial activity have been a widespread ecological focus, the regulatory effects of interspecific interactions are rarely considered in climate feedback studies. We explore the potential of soil animals to mediate microbial responses to warming and nitrogen enrichment within a long-term, field-based global change study. The combination of global change factors alleviated the bottom-up limitations on fungal growth, stimulating enzyme production and decomposition rates in the absence of soil animals. However, increased fungal biomass also stimulated consumption rates by soil invertebrates, restoring microbial process rates to levels observed under ambient conditions. Our results support the contemporary theory that top-down control in soil food webs is apparent only in the absence of bottom-up limitation. As such, when global change factors alleviate the bottom-up limitations on microbial activity, top-down control becomes an increasingly important regulatory force with the capacity to dampen the strength of positive carbon cycle-climate feedbacks. PMID:26038557

  5. Biotic interactions mediate soil microbial feedbacks to climate change

    PubMed Central

    Crowther, Thomas W.; Thomas, Stephen M.; Maynard, Daniel S.; Baldrian, Petr; Covey, Kristofer; Frey, Serita D.; van Diepen, Linda T. A.; Bradford, Mark A.

    2015-01-01

    Decomposition of organic material by soil microbes generates an annual global release of 50–75 Pg carbon to the atmosphere, ∼7.5–9 times that of anthropogenic emissions worldwide. This process is sensitive to global change factors, which can drive carbon cycle–climate feedbacks with the potential to enhance atmospheric warming. Although the effects of interacting global change factors on soil microbial activity have been a widespread ecological focus, the regulatory effects of interspecific interactions are rarely considered in climate feedback studies. We explore the potential of soil animals to mediate microbial responses to warming and nitrogen enrichment within a long-term, field-based global change study. The combination of global change factors alleviated the bottom-up limitations on fungal growth, stimulating enzyme production and decomposition rates in the absence of soil animals. However, increased fungal biomass also stimulated consumption rates by soil invertebrates, restoring microbial process rates to levels observed under ambient conditions. Our results support the contemporary theory that top-down control in soil food webs is apparent only in the absence of bottom-up limitation. As such, when global change factors alleviate the bottom-up limitations on microbial activity, top-down control becomes an increasingly important regulatory force with the capacity to dampen the strength of positive carbon cycle–climate feedbacks. PMID:26038557

  6. Evaluation of FEMA-440 for including soil-structure interaction

    NASA Astrophysics Data System (ADS)

    Khoshnoudian, F.; Behmanesh, I.

    2010-09-01

    Replacing the entire soil-structure system with a fixed base oscillator to consider the effect of soil-structure interaction (SSI) is a common analysis method in seismic design. This technique has been included in design procedures such as NEHRP, ASCE, etc. by defining an equivalent fundamental period and damping ratio that can modify the response of the structure. However, recent studies indicate that the effects of SSI should be reconsidered when a structure undergoes a nonlinear displacement demand. In recent documents on Nonlinear Static Procedures (NSPs), FEMA-440 (2005), a modified damping ratio of the replacement oscillator was proposed by introducing the ductility of the soil-structure system obtained from pushover analysis. In this paper, the damping defined in FEMA-440 to include the soil-structure interaction effect is evaluated, and the accuracy of the Coefficient Method given in FEMA-440 and the Equivalent Linearization Method is studied. Although the improvements for Nonlinear Static Procedures (NSPs) in FEMA-440 are achieved for a fixed base SDOF structure, the soil effects are not perfectly obtained. Furthermore, the damping definition of a soil-structure system is extended to structures to consider bilinear behavior.

  7. Evaluation of different field methods for measuring soil water infiltration

    NASA Astrophysics Data System (ADS)

    Pla-Sentís, Ildefonso; Fonseca, Francisco

    2010-05-01

    Soil infiltrability, together with rainfall characteristics, is the most important hydrological parameter for the evaluation and diagnosis of the soil water balance and soil moisture regime. Those balances and regimes are the main regulating factors of the on site water supply to plants and other soil organisms and of other important processes like runoff, surface and mass erosion, drainage, etc, affecting sedimentation, flooding, soil and water pollution, water supply for different purposes (population, agriculture, industries, hydroelectricity), etc. Therefore the direct measurement of water infiltration rates or its indirect deduction from other soil characteristics or properties has become indispensable for the evaluation and modelling of the previously mentioned processes. Indirect deductions from other soil characteristics measured under laboratory conditions in the same soils, or in other soils, through the so called "pedo-transfer" functions, have demonstrated to be of limited value in most of the cases. Direct "in situ" field evaluations have to be preferred in any case. In this contribution we present the results of past experiences in the measurement of soil water infiltration rates in many different soils and land conditions, and their use for deducing soil water balances under variable climates. There are also presented and discussed recent results obtained in comparing different methods, using double and single ring infiltrometers, rainfall simulators, and disc permeameters, of different sizes, in soils with very contrasting surface and profile characteristics and conditions, including stony soils and very sloping lands. It is concluded that there are not methods universally applicable to any soil and land condition, and that in many cases the results are significantly influenced by the way we use a particular method or instrument, and by the alterations in the soil conditions by the land management, but also due to the manipulation of the surface

  8. COMPARISON AND EVALUATION OF FIELD METHODS (DIRECT AND INDIRECT) TO ESTIMATE SOIL WATER FLUXES.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of soil water fluxes is critical for evaluating efficiency and environmental effects of soil and crop management. Indirect methods commonly used to estimate soil water fluxes estimates are currently based on (a) soil water balance, (b) soil water potential measurements with the Darcy-Bucki...

  9. Human interactions with ground-water

    USGS Publications Warehouse

    Zaporozec, A.

    1983-01-01

    Ground-Water could be considered as an immense reservoir, from which only a certain amount of water can be withdrawn without affecting the quantity and quality of water. This amount is determined by the characteristics of the environment in which ground-water occurs and by the interactions of ground-water with precipitation, surface water, and people. It should be recognized that quantity and quality of ground-water are intimately related and should be considered accordingly. Quantity refers to usable water and water is usable for any specific purpose only so long as its quality has not deteriorated beyond acceptable limits. Thus an overall quantitative and qualitative management of ground water is inevitable, and its should also involve the uses of ground-water reservoirs for purposes other than water supply. The main objective of ground-water management is to ensure that ground-water resources will be available in appropriate time and in appropriate quantity and quality to meet the most important demands of our society. Traditional, and obvious uses of ground-water are the extraction of water for water supplies (domestic, municipal, agricultural, and industrial) and the natural discharge feeding lakes and maintaining base flow of streams. Not so obvious are the uses of ground-water reservoirs, the very framework within which ground-water occurs and moves, and in which other fluids or materials can be stored. In the last two decades, ground-water reservoirs have been intensively considered for many other purposes than water supplies. Diversified and very often conflicting uses need to be evaluated and dealt with in the most efficient way in order to determine the importance of each possible use, and to assign priorities of these uses. With rising competition for the use of ground-water reservoirs, we will also need to increase the potential for effective planning of ground-water development and protection. Man's development and use of ground-water necessarily

  10. Cosmic Ray Neutron Probe Soil Water Measurements over Complex Terrain in Austria

    NASA Astrophysics Data System (ADS)

    Vreugdenhil, Mariette; Weltin, Georg; Kheng Heng, Lee; Wahbi, Ammar; Oismueller, Markus; Dercon, Gerd

    2014-05-01

    The importance of surface soil water (rooting zone) has become evident with climate change affecting rainfall patterns and crop production. The use of Cosmic Ray Neutron Probe (CRNP) for measuring surface soil water has become increasingly popular. The advantage of CRNP is that it is a non-invasive technique for measuring soil water content at an area-wide scale, in contrast to more conventional, techniques which measure mainly at field scale (point level). The CRNP integrates over a circular area of ca. 600 meters in diameter, to a depth of 70 cm, giving an average value for soil water content. Cosmic radiation interacting with the Earth's atmosphere continuously generates neutrons. At Earth's surface, these neutrons interact with surface water, and are slowed down. At sub-micrometer geometrics, these neutrons affect semiconductor devices, so they can be counted, slow and fast ones separately. From the difference in numbers between fast and slow neutrons, soil water content is calculated. As first in Austria, a CRNP (CRS 1000/B model) consisting of two neutron counters (one tuned for slow, the other one for fast neutrons), data logger and an Iridium modem, has been installed at Petzenkirchen research station of the Doctoral Programme for Water Resource Systems (TU Vienna) at 48.14 latitude and 15.17 longitude, 100 km west of Vienna, in late autumn 2013. The research station is located in an undulating agricultural landscape, characterized by heavy Cambisols and Planosols, and winter wheat and barley as main crops in winter, and maize and sunflower in summer. In addition, an in-situ soil moisture network consisting of 32 stations of Time Domain Transmissivity (TDT) sensors measuring soil water at 4 depths (0.05, 0.10,0.20 and 0.50 m) over an area of 64 ha has been established. This TDT network is currently being used to validate the use of the innovative CRNP technique. First results will be shown at the EGU 2014.

  11. Numerical analysis of kinematic soil-pile interaction

    SciTech Connect

    Castelli, Francesco; Maugeri, Michele; Mylonakis, George

    2008-07-08

    In the present study, the response of singles pile to kinematic seismic loading is investigated using the computer program SAP2000. The objectives of the study are: (1) to develop a numerical model that can realistically simulate kinematic soil-structure interaction for piles accounting for discontinuity conditions at the pile-soil interface, energy dissipation and wave propagation; (2) to use the model for evaluating kinematic interaction effects on pile response as function of input ground motion; and (3) to present a case study in which theoretical predictions are compared with results obtained from other formulations. To evaluate the effects of kinematic loading, the responses of both the free-field soil (with no piles) and the pile were compared. Time history and static pushover analyses were conducted to estimate the displacement and kinematic pile bending under seismic loadings.

  12. Ant interactions with soil organisms and associated semiochemicals.

    PubMed

    Vander Meer, Robert

    2012-06-01

    This review focuses on the semiochemical interactions between ants and their soil environment. Ants occupy virtually every ecological niche and have evolved mechanisms to not just cope with, but also manipulate soil organisms. The metapleural gland, specific to ants was thought to be the major source of semiochemical antimicrobial compounds targeting general or specific deleterious microbes. The extremely diverse variety of semiochemicals and their sources with antimicrobial activity or potential activity is highlighted. The leaf-cutting ants and fire ant provide the most researched species, in part because they cause significant economic damage. The leaf-cutting ant is particularly interesting because researchers have uncovered unexpected interactions between leaf-cutting ant fungal farm, parasitic fungi, bacteria, yeasts, and ant defensive semiochemicals. These complex relationships highlight the multidimensional aspects of ants and the soil environment in which they live. PMID:22653568

  13. The role of Soil Water Retention Curve in slope stability analysis in unsaturated and heterogeneous soils.

    NASA Astrophysics Data System (ADS)

    Antinoro, Chiara; Arnone, Elisa; Noto, Leonardo V.

    2015-04-01

    The mechanisms of rainwater infiltration causing slope instability had been analyzed and reviewed in many scientific works. Rainwater infiltration into unsaturated soil increases the degree of saturation, hence affecting the shear strength properties and thus the probability of slope failure. It has been widely proved that the shear strength properties change with the soil water suction in unsaturated soils; therefore, the accuracy to predict the relationship between soil water content and soil water suction, parameterized by the soil-water characteristic curve, has significant effects on the slope stability analysis. The aim of this study is to investigate how the characterization of SWRC of differently structured unsaturated soils affects the slope stability on a simple infinite slope. In particular, the unimodal and bimodal distributions of the soil pore size were compared. Samples of 40 soils, highly different in terms of structure and texture, were collected and used to calibrate two bimodal SWRCs, i.e. Ross and Smettem (1993) and Dexter et al., (2008). The traditional unimodal van Genuchten (1980) model was also applied for comparison. Slope stability analysis was conducted in terms of Factor of Safety (FS) by applying the infinite slope model for unsaturated soils. In the used formulation, the contribution of the suction effect is tuned by a parameter 'chi' in a rate proportional to the saturation conditions. Different parameterizations of this term were also compared and analyzed. Results indicated that all three SWRC models showed good overall performance in fitting the sperimental SWRCs. Both the RS and DE models described adequately the water retention data for soils with a bimodal behavior confirmed from the analysis of pore size distribution, but the best performance was obtained by DE model confirmed. In terms of FS, the tree models showed very similar results as soil moisture approached to the saturated condition; however, within the residual zone

  14. Evolution of Soil Moisture-Convection Interactions against the Backdrop of Global Oscillations

    NASA Astrophysics Data System (ADS)

    Tawfik, A. B.; Dirmeyer, P.

    2014-12-01

    Interannual changes in how soil moisture can trigger convection are explored within the context of known global-scale oscillations, such as ENSO. Because soil moisture-convection interactions are a local phenomenon that require a sufficiently moist and unstable atmosphere to initiate convection, any systematic changes to water vapor produced by these global circulation changes may manifest in disrupting or promoting the soil moisture-precipitation feedback chain. Using a new framework, the Heated Condensation Framework (HCF; Tawfik and Dirmeyer 2014), local land-atmosphere coupling can be examined by separating the atmospheric background state from the land surface state in terms of convective initiation. The current work explores how the soil moisture-convection relationship changes from year-to-year and during influential El Nino and La Nina events. This is done using several global and regional reanalysis products, as well as observations where available.

  15. SEISMIC RESPONSE OF DAM WITH SOIL-STRUCTURE INTERACTION.

    USGS Publications Warehouse

    Bycroft, G.N.; Mork, P.N.

    1987-01-01

    An analytical solution to the response of a long trapezoidal-section dam on a foundation consisting of an elastic half-space and subjected to simulated earthquake motion is developed. An optimum seismic design is achieved when the cross section of the dam is triangular. The effect of soil structure interaction is to lower the strain occurring in the dam.

  16. Modeling root water uptake in soils: opportunities and challenges

    NASA Astrophysics Data System (ADS)

    Javaux, Mathieu; Couvreur, Valentin; Huber, Katrin; Meunier, Félicien; Vanderborght, Jan; Vereecken, Harry

    2016-04-01

    Root water uptake modeling concepts have evolved over time. On one hand, mesoscopic models have been developed, which explicitly represent the fluxes at the soil root interfaces. On the other hand macroscopic approaches were proposed, which embedded root water uptake into a sink term in the macroscopic mass balance equation. Today, new techniques for imaging root architecture, water fluxes and soil properties open new possibilities to the understanding of water depletion in planted soils. Amongst others, architectural hydraulic root and soil models can be used to bridge the scale gap between single root and plant scales. In this talk, several new promising experimental approaches will be presented together with new models and upscaling procedures, possibly paving the way for the future models of root water uptake. Furthermore, open challenges will also be presented.

  17. Predicting saturated and unsaturated hydraulic conductivity in undisturbed soils from soil water characteristics

    SciTech Connect

    Poulsen, T.G.; Loldrup, P.; Yamaguchi, Toshiko; Jacobsen, O.H.

    1999-12-01

    Hydraulic conductivity is likely the most important soil property controlling water and solute movement in soils. It is also one of the most variable and uncertain soil properties. Models for predicting soil hydraulic conductivity from other soil characteristics are, therefore, useful in both deterministic and stochastic transport studies. A new model for predicting saturated hydraulic conductivity (K{sub s}) in undisturbed soils from macroporosity ({epsilon}{sub 100}), defined as the air-filled porosity at a soil-water potential of {Psi} = {minus}100 cm H{sub 2}O, was developed using data for 23 undisturbed soils. The new K{sub s} model compared well with measurements when tested against independent data sets for 73 undisturbed soils from the UNSODA database and gave improved predictions compared with existing K{sub s} models. Two new models for predicting relative hydraulic conductivity (K/K{sub s}) in relatively moist, ({Psi} > {minus}350 cm H{sub 2}O) undisturbed soils from soil-water content ({theta}) and the Campbell soil-water retention parameter, b, were developed using conductivity and water retention data for the 73 soils from UNSODA. The new K/K{sub s} models represent modifications of the recently presented DLC and SLC models for predicting K/K{sub s} in sieved, repacked soils. The modified DLC and SLC models were combined with the new K{sub s} model, yielding new two-parameter ({epsilon}{sub 100}, b) models for unsaturated hydraulic conductivity (K({theta})) in undisturbed soil. The two new K({theta}) models were successfully tested against independent K({theta}) data. Also, the classical Campbell K/K{sub s} model, combined with the new, more accurate K{sub s} model, gave K({theta}) prediction accuracy almost as good as the modified DLC and SLC K({theta}) models. The suggested two-parameter K({theta}) models require knowledge of only the soil-water retention curve, including a measurement at {Psi} = {minus}100 cm H{sub 2}O, and seem promising for use

  18. Numerical and Experimental Quantification of coupled water and water vapor fluxes in very dry soils.

    NASA Astrophysics Data System (ADS)

    Madi, Raneem; de Rooij, Gerrit

    2015-04-01

    In arid and semi-arid regions with deep groundwater and very dry soils, vapor movement in the vadose zone may be a major component in the total water flux. Therefore, the coupled movement of liquid water, water vapor and heat transport in the unsaturated zone should be explicitly considered to quantify subsurface water fluxes in such regions. Only few studies focused on the importance of vapor water diffusion in dry soils and in many water flow studies in soil it was neglected. We are interested in the importance of water vapor diffusion and condensation in very dry sand. A version of Hydrus-1D capable of solving the coupled water vapor and heat transport equations will be used to do the numerical modeling. The soil hydraulic properties will be experimentally determined. A soil column experiment was developed with negligible liquid flow in order to isolate vapor flux for testing. We have used different values of initial water contents trying to generate different scenarios to assess the role of the water vapor transport in arid and semi-arid soils and how it changes the soil water content using different soil hydraulic parametrization functions. In the session a preliminary experimental and modelling results of vapor and water fluxes will be presented.

  19. Simulation of large-scale soil water systems using groundwater data and satellite based soil moisture

    NASA Astrophysics Data System (ADS)

    Kreye, Phillip; Meon, Günter

    2016-04-01

    Complex concepts for the physically correct depiction of dominant processes in the hydrosphere are increasingly at the forefront of hydrological modelling. Many scientific issues in hydrological modelling demand for additional system variables besides a simulation of runoff only, such as groundwater recharge or soil moisture conditions. Models that include soil water simulations are either very simplified or require a high number of parameters. Against this backdrop there is a heightened demand of observations to be used to calibrate the model. A reasonable integration of groundwater data or remote sensing data in calibration procedures as well as the identifiability of physically plausible sets of parameters is subject to research in the field of hydrology. Since this data is often combined with conceptual models, the given interfaces are not suitable for such demands. Furthermore, the application of automated optimisation procedures is generally associated with conceptual models, whose (fast) computing times allow many iterations of the optimisation in an acceptable time frame. One of the main aims of this study is to reduce the discrepancy between scientific and practical applications in the field of hydrological modelling. Therefore, the soil model DYVESOM (DYnamic VEgetation SOil Model) was developed as one of the primary components of the hydrological modelling system PANTA RHEI. DYVESOMs structure provides the required interfaces for the calibrations made at runoff, satellite based soil moisture and groundwater level. The model considers spatial and temporal differentiated feedback of the development of the vegetation on the soil system. In addition, small scale heterogeneities of soil properties (subgrid-variability) are parameterized by variation of van Genuchten parameters depending on distribution functions. Different sets of parameters are operated simultaneously while interacting with each other. The developed soil model is innovative regarding concept

  20. Dynamic aspects of soil water availability for isohydric plants: Focus on root hydraulic resistances

    NASA Astrophysics Data System (ADS)

    Couvreur, V.; Vanderborght, J.; Draye, X.; Javaux, M.

    2014-11-01

    Soil water availability for plant transpiration is a key concept in agronomy. The objective of this study is to revisit this concept and discuss how it may be affected by processes locally influencing root hydraulic properties. A physical limitation to soil water availability in terms of maximal flow rate available to plant leaves (Qavail) is defined. It is expressed for isohydric plants, in terms of plant-centered variables and properties (the equivalent soil water potential sensed by the plant, ψs eq; the root system equivalent conductance, Krs; and a threshold leaf water potential, ψleaf lim). The resulting limitation to plant transpiration is compared to commonly used empirical stress functions. Similarities suggest that the slope of empirical functions might correspond to the ratio of Krs to the plant potential transpiration rate. The sensitivity of Qavail to local changes of root hydraulic conductances in response to soil matric potential is investigated using model simulations. A decrease of radial conductances when the soil dries induces earlier water stress, but allows maintaining higher night plant water potentials and higher Qavail during the last week of a simulated 1 month drought. In opposition, an increase of radial conductances during soil drying provokes an increase of hydraulic redistribution and Qavail at short term. This study offers a first insight on the effect of dynamic local root hydraulic properties on soil water availability. By better understanding complex interactions between hydraulic processes involved in soil-plant hydrodynamics, better prospects on how root hydraulic traits mitigate plant water stress might be achieved.

  1. Soil-structure interaction analysis of jack-up platforms subjected to monochrome and irregular waves

    NASA Astrophysics Data System (ADS)

    Korzani, Maziar Gholami; Aghakouchak, Ali Akbar

    2015-03-01

    As jack-up platforms have recently been used in deeper and harsher waters, there has been an increasing demand to understand their behaviour more accurately to develop more sophisticated analysis techniques. One of the areas of significant development has been the modelling of spudcan performance, where the load-displacement behaviour of the foundation is required to be included in any numerical model of the structure. In this study, beam on nonlinear winkler foundation (BNWF) modeling—which is based on using nonlinear springs and dampers instead of a continuum soil media—is employed for this purpose. A regular monochrome design wave and an irregular wave representing a design sea state are applied to the platform as lateral loading. By using the BNWF model and assuming a granular soil under spudcans, properties such as soil nonlinear behaviour near the structure, contact phenomena at the interface of soil and spudcan (such as uplifting and rocking), and geometrical nonlinear behaviour of the structure are studied. Results of this study show that inelastic behaviour of the soil causes an increase in the lateral displacement at the hull elevation and permanent unequal settlement in soil below the spudcans, which are increased by decreasing the friction angle of the sandy soil. In fact, spudcans and the underlying soil cause a relative fixity at the platform support, which changes the dynamic response of the structure compared with the case where the structure is assumed to have a fixed support or pinned support. For simulating this behaviour without explicit modelling of soil-structure interaction (SSI), moment-rotation curves at the end of platform legs, which are dependent on foundation dimensions and soil characteristics, are obtained. These curves can be used in a simplified model of the platform for considering the relative fixity at the soil-foundation interface.

  2. Field-measured, hourly soil water evaporation stages in relation to reference evapotranspiration rate and soil to air temperature ratio

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water evaporation takes critical water supplies away from crops, especially in areas where both rainfall and irrigation water are limited. This study measured bare soil water evaporation from clay loam, silt loam, sandy loam, and fine sand soils. It found that on average almost half of the ir...

  3. Soil Water Retention as Indicator for Soil Physical Quality - Examples from Two SoilTrEC European Critical Zone Observatories

    NASA Astrophysics Data System (ADS)

    Rousseva, Svetla; Kercheva, Milena; Shishkov, Toma; Dimitrov, Emil; Nenov, Martin; Lair, Georg J.; Moraetis, Daniel

    2014-05-01

    Soil water retention is of primary importance for majority of soil functions. The characteristics derived from Soil Water Retention Curve (SWRC) are directly related to soil structure and soil water regime and can be used as indicators for soil physical quality. The aim of this study is to present some parameters and relationships based on the SWRC data from the soil profiles characterising the European SoilTrEC Critical Zone Observatories Fuchsenbigl and Koiliaris. The studied soils are representative for highly productive soils managed as arable land in the frame of soil formation chronosequence at "Marchfeld" (Fuchsenbigl CZO), Austria and heavily impacted soils during centuries through intensive grazing and farming, under severe risk of desertification in context of climatic and lithological gradient at Koiliaris, Crete, Greece. Soil water retention at pF ≤ 2.52 was determined using the undisturbed soil cores (100 cm3 and 50 cm3) by a suction plate method. Water retention at pF = 4.2 was determined by a membrane press method and at pF ≥ 5.6 - by adsorption of water vapour at controlled relative humidity, both using ground soil samples. The soil physical quality parameter (S-parameter) was defined as the slope of the water retention curve at its inflection point (Dexter, 2006), determined with the obtained parameters of van Genuhten (1980) water retention equation. The S-parameter values were categorised to assess soil physical quality as follows: S < 0.020 very poor, 0.020 ≤ S < 0.035 poor, 0.035 ≤ S < 0.050 good, S ≥ 0.050 very good (Dexter, 2004). The results showed that most of the studied topsoil horizons have good physical quality according to both the S-parameter and the Plant-Available Water content (PAW), with the exception of the soils from croplands at CZO Fuxenbigl (F4, F5) which are with poor soil structure. The link between the S-parameter and the indicator of soil structure stability (water stable soil aggregates with size 1-3 mm) is not

  4. Integrated use of soil physical and water isotope methods for ecohydrological characterization of desertified areas

    NASA Astrophysics Data System (ADS)

    Külls, Christoph; Nunes, Alice; Köbel-Batista, Melanie; Branquinho, Cristina; Bianconi, Nadja; Costantini, Eduardo

    2014-05-01

    Measures for monitoring desertification and soil degradation require a thorough understanding of soil physical properties and of the water balance in order to guide restoration efforts (Costantini et al. 2009). It is hypothesized that long term restoration success on degraded land depends on a series of interacting factors such as exposition, soil type, soil hydrology including lateral flow on hill-slope catenae. Recently, new soil water isotope measurement techniques have been developed (Garvelmann et al. 2012) that provide much faster and reliable stable water isotope profiles in soils. This technique yield information on groundwater recharge, soil water balance and on the origin of water available for plants, which in combination with conservative chemical tracers (chloride) can be validated. A multidisciplinary study including ecologists, soil physicists and hydrologists of the COST Action Desert Restoration Hub was carried out on four semi-arid sites in Portugal. A comparative characterization of soil physical parameters, soil water isotope and chloride profiles was performed in order to estimate pedoclimate, soil aridity, soil water balance and groundwater recharge. In combination with soil physical data a comprehensive and cross-validated characterization of pedoclimate and soil aridity was obtained. These indicators were then integrated and related to plant cover. The long-term rainfall of the four sites ranges from 512 to 638 mm, whereas air temperature is from 15.8 to 17.0°C. The De Martonne index of aridity spans from 19.3 to 24.6, pointing to semiarid to moderately arid climatic conditions. The long-term average number of days when the first 0.50 m of soil is dry ranges from 110 to 134, while the mean annual soil temperature at 0.50 m spans from 15.8 and 19.1°C. The studied profiles show different hydrological characteristics, in particular, the estimated hydraulic conductivity ranges from 0.1-1 to 10-100 µm/s. Three out of four profiles show a

  5. Volatile-mediated interactions between phylogenetically different soil bacteria

    PubMed Central

    Garbeva, Paolina; Hordijk, Cornelis; Gerards, Saskia; de Boer, Wietse

    2014-01-01

    There is increasing evidence that organic volatiles play an important role in interactions between micro-organisms in the porous soil matrix. Here we report that volatile compounds emitted by different soil bacteria can affect the growth, antibiotic production and gene expression of the soil bacterium Pseudomonas fluorescens Pf0–1. We applied a novel cultivation approach that mimics the natural nutritional heterogeneity in soil in which P. fluorescens grown on nutrient-limited agar was exposed to volatiles produced by 4 phylogenetically different bacterial isolates (Collimonas pratensis, Serratia plymuthica, Paenibacillus sp., and Pedobacter sp.) growing in sand containing artificial root exudates. Contrary to our expectation, the produced volatiles stimulated rather than inhibited the growth of P. fluorescens. A genome-wide, microarray-based analysis revealed that volatiles of all four bacterial strains affected gene expression of P. fluorescens, but with a different pattern of gene expression for each strain. Based on the annotation of the differently expressed genes, bacterial volatiles appear to induce a chemotactic motility response in P. fluorescens, but also an oxidative stress response. A more detailed study revealed that volatiles produced by C. pratensis triggered, antimicrobial secondary metabolite production in P. fluorescens. Our results indicate that bacterial volatiles can have an important role in communication, trophic - and antagonistic interactions within the soil bacterial community. PMID:24966854

  6. Prion Protein Interaction with Soil Humic Substances: Environmental Implications

    PubMed Central

    Giachin, Gabriele; Narkiewicz, Joanna; Scaini, Denis; Ngoc, Ai Tran; Margon, Alja; Sequi, Paolo; Leita, Liviana; Legname, Giuseppe

    2014-01-01

    Transmissible spongiform encephalopathies (TSE) are fatal neurodegenerative disorders caused by prions. Animal TSE include scrapie in sheep and goats, and chronic wasting disease (CWD) in cervids. Effective management of scrapie in many parts of the world, and of CWD in North American deer population is complicated by the persistence of prions in the environment. After shedding from diseased animals, prions persist in soil, withstanding biotic and abiotic degradation. As soil is a complex, multi-component system of both mineral and organic components, it is important to understand which soil compounds may interact with prions and thus contribute to disease transmission. Several studies have investigated the role of different soil minerals in prion adsorption and infectivity; we focused our attention on the interaction of soil organic components, the humic substances (HS), with recombinant prion protein (recPrP) material. We evaluated the kinetics of recPrP adsorption, providing a structural and biochemical characterization of chemical adducts using different experimental approaches. Here we show that HS act as potent anti-prion agents in prion infected neuronal cells and in the amyloid seeding assays: HS adsorb both recPrP and prions, thus sequestering them from the prion replication process. We interpreted our findings as highly relevant from an environmental point of view, as the adsorption of prions in HS may affect their availability and consequently hinder the environmental transmission of prion diseases in ruminants. PMID:24937266

  7. Corn yield response to nitrogen and soil water content variability along a hillslope

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A better understanding of the interaction of corn response to N fertilizer and soil water availability should improve N fertilizer use efficiency in corn (Zea mays L.) through spatially variable N applications. The objective of this study was to determine whether the within-field spatial variability...

  8. Furrow Diking and Conservation Tillage to Conserve Soil and Water

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crop production in Georgia is limited. Increased water capture would improve natural water use and reduce supplemental irrigation amounts. We quantified water capturing and erosional characteristics of furrow dike tillage (DT) by comparing infiltration, runoff, and soil loss from a Tifton loamy sand...

  9. Toward improving global estimates of field soil water capacity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Field capacity or field water capacity (FC) is defined as the water content of a soil after having been wetted with water and after free drainage is negligible. Different recommendations exist world-wide on which, if any, pressure head should be used in laboratory measurements to approximate the FC ...

  10. Conservation laws for a class of soil water equations

    NASA Astrophysics Data System (ADS)

    Yaşar, Emrullah

    2010-10-01

    In this paper, we consider a class of nonlinear partial differential equations which model soil water infiltration, redistribution and extraction in a bedded soil profile irrigated by a line source drip irrigation system. By using the nonlocal conservation theorem method and the partial Lagrangian approach, conservation laws are presented. It is observed that both approaches lead to the nontrivial and infinite conservation laws.

  11. Measurement of soil water content with dielectric dispersion frequency

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Frequency domain reflectometry (FDR) is an inexpensive and attractive methodology for repeated measurements of soil water content (SWC). Although there are some known measurement limitations for dry soil and sand, a fixed-frequency method is commonly employed using commercially available FDR probes....

  12. As Leaching into Fresh Water from Highly Contaminated Hawaiian Soils

    NASA Astrophysics Data System (ADS)

    Niklis, N. J.; Rubin, K. H.; El-Kadi, A. I.

    2009-12-01

    Arsenic contamination of current and former agricultural soils in Hawaii is an unfortunate legacy of plantation era agricultural practices. Here, we report an investigation of As mobility in fresh water from highly contaminated (0.8 % As) A-zone Hawaiian andisols from the Hamakua Coast of the Island of Hawai’i. Aliquots of the same acidic soil (pH= 5.0) were exposed to fresh water for varying lengths of time and analyzed to quantify the fraction of As and other elements leached from the soil relative to concentrations determined by total digestion. A maximum of 0.04% of As and 0.05% of Fe were removed from the soils in initial rinses and multi-day leaches using 18 megaohm Millipore water, in experiments lasting up to 35 days. Arsenic concentrations were highest in initial soil rinses, indicating that a small fraction of the total As in the soil is either loosely bound or present as a fine-grained, soluble As-bearing phase. During subsequent leaching experiments, arsenic and most other inorganic ions that we analyzed for reached equilibrium after 3 days; Fe reached equilibrium concentrations after 10 days. All soil solutions contained As levels that exceeded the EPA acceptable drinking water limit of 0.01 ppm. However, contaminant transport modeling suggests that As contaminated leachates would not migrate substantially from this site, so that local isolation and storage of contaminated soils would likely be an acceptable containment method.

  13. Augmenting soil water storage using uncharred switchgrass and pyrolyzed biochars

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Biochar is an amendment that can augment soil water storage; however, its projected cost per ton could be financially limiting at field application scales. It may be more monetarily convenient if an alternate amendment were available that could deliver similar soil enhancements. We compared two swi...

  14. Infiltration characteristics of bare soil under sequential water application events

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The marked reduction in infiltration rate caused by formation of a soil surface seal is a well known phenomenon but often ignored in infiltration models. The effect sequential water application events have on infiltration rate and soil surface seal formation has rarely been investigated. The objecti...

  15. The chemistry of salt-affected soils and waters

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of the chemistry of salt affected soils and waters is necessary for management of irrigation in arid and semi-arid regions. In this chapter we review the origin of salts in the landscape, the major chemical reactions necessary for prediction of the soil solution composition, and the use of...

  16. Macrofauna assemblage composition and soil moisture interact to affect soil ecosystem functions

    NASA Astrophysics Data System (ADS)

    Collison, E. J.; Riutta, T.; Slade, E. M.

    2013-02-01

    Changing climatic conditions and habitat fragmentation are predicted to alter the soil moisture conditions of temperate forests. It is not well understood how the soil macrofauna community will respond to changes in soil moisture, and how changes to species diversity and community composition may affect ecosystem functions, such as litter decomposition and soil fluxes. Moreover, few studies have considered the interactions between the abiotic and biotic factors that regulate soil processes. Here we attempt to disentangle the interactive effects of two of the main factors that regulate soil processes at small scales - moisture and macrofauna assemblage composition. The response of assemblages of three common temperate soil invertebrates (Glomeris marginata Villers, Porcellio scaber Latreille and Philoscia muscorum Scopoli) to two contrasting soil moisture levels was examined in a series of laboratory mesocosm experiments. The contribution of the invertebrates to the leaf litter mass loss of two common temperate tree species of contrasting litter quality (easily decomposing Fraxinus excelsior L. and recalcitrant Quercus robur L.) and to soil CO2 fluxes were measured. Both moisture conditions and litter type influenced the functioning of the invertebrate assemblages, which was greater in high moisture conditions compared with low moisture conditions and on good quality vs. recalcitrant litter. In high moisture conditions, all macrofauna assemblages functioned at equal rates, whereas in low moisture conditions there were pronounced differences in litter mass loss among the assemblages. This indicates that species identity and assemblage composition are more important when moisture is limited. We suggest that complementarity between macrofauna species may mitigate the reduced functioning of some species, highlighting the importance of maintaining macrofauna species richness.

  17. Estimating water and nitrate leaching in tree crops using inverse modelled plant and soil hydraulic properties

    NASA Astrophysics Data System (ADS)

    Couvreur, Valentin; Kandelous, Maziar; Mairesse, Harmony; Baram, Shahar; Moradi, Ahmad; Pope, Katrin; Hopmans, Jan

    2015-04-01

    Groundwater quality is specifically vulnerable in irrigated agricultural lands in California and many other (semi-)arid regions of the world. The routine application of nitrogen fertilizers with irrigation water in California is likely responsible for the high nitrate concentrations in groundwater, underlying much of its main agricultural areas. To optimize irrigation/fertigation practices, it is essential that irrigation and fertilizers are applied at the optimal concentration, place, and time to ensure maximum root uptake and minimize leaching losses to the groundwater. The applied irrigation water and dissolved fertilizer, root nitrate and water uptake interact with soil and root properties in a complex manner that cannot easily be resolved. It is therefore that coupled experimental-modelling studies are required to allow for unravelling of the relevant complexities that result from typical variations of crop properties, soil texture and layering across farmer-managed fields. A combined field monitoring and modelling approach was developed to quantify from simple measurements the leaching of water and nitrate below the root zone. The monitored state variables are soil water content within the root zone, soil matric potential below the root zone, and nitrate concentration in the soil solution. Plant and soil properties of incremented complexity are optimized with the software HYDRUS in an inverse modelling scheme, which allows estimating leaching under constraint of hydraulic principles. Questions of optimal irrigation and fertilization timing can then be addressed using predictive results and global optimization algorithms.

  18. Effect of water content and soil texture on consolidation in unsaturated soils

    NASA Astrophysics Data System (ADS)

    Lo, Wei-Cheng; Lee, Jhe-Wei

    2015-08-01

    Soil consolidation, involving time-dependent coupling between deformation of a porous medium and interstitial fluid flows within it, is of relevance to many subsurface engineering problems. A comprehensive model of poroelasticity for consolidation in unsaturated soils has been recently developed by Lo et al. (2014), but it still remains elusive how variations in soil texture and water content affect consolidation behavior, and the underlying parameters deriving this behavior. In the current study, a boundary-value problem is first setup corresponding to two symmetric semi-permeable drainage conditions, and then solved analytically for describing the excess pore air and water pressures along with the total settlement in response to time-invariant external loading using the Laplace transform. These solutions are numerically calculated for unsaturated soils with eleven texture classes as a function of three initial water saturations as representative examples. Our results reveal that the excess pore water pressure and time-dependent total settlement are indeed significantly sensitive to both soil texture and initial water saturation. We demonstrate that the coefficient of consolidation for water and its loading efficiency are two important physical parameters controlling consolidation behavior. With respect to the same soil texture, the coefficient of consolidation for water increases with an increase in initial water saturation, taking a value approximately four to five orders of magnitude greater in saturated soils than that in unsaturated ones. For a given initial water saturation, the rate of dissipation of excess pore water pressure is smallest in clay, followed by silty clay, silty clay loam, sandy clay, clay loam, silt loam, loam, sandy clay loam, sandy loam, loamy sand, and sand. A comparative study shows that in the early stage of consolidation, unsaturated soils bear smaller excess pore water pressure, but its dissipation is completed faster in saturated

  19. Mediterranean shrub vegetation: soil protection vs. water availability

    NASA Astrophysics Data System (ADS)

    García Estringana, Pablo; Nieves Alonso-Blázquez, M.; Alegre, Alegre; Cerdà, Artemi

    2014-05-01

    Soil Erosion and Land Degradation are closely related to the changes in the vegetation cover (Zhao et al., 2013). Although other factors such as rainfall intensiy or slope (Ziadat and Taimeh, 2013) the plant covers is the main factor that controls the soil erosion (Haregeweyn, 2013). Plant cover is the main factor of soil erosion processes as the vegetation control the infiltration and runoff generation (Cerdà, 1998a; Kargar Chigani et al., 2012). Vegetation cover acts in a complex way in influencing on the one hand on runoff and soil loss and on the other hand on the amount and the way that rainfall reaches the soil surface. In arid and semiarid regions, where erosion is one of the main degradation processes and water is a scant resource, a minimum percentage of vegetation coverage is necessary to protect the soil from erosion, but without compromising the availability of water (Belmonte Serrato and Romero Diaz, 1998). This is mainly controlled by the vegetation distribution (Cerdà, 1997a; Cammeraat et al., 2010; Kakembo et al., 2012). Land abandonment is common in Mediterranean region under extensive land use (Cerdà, 1997b; García-Ruiz, 2010). Abandoned lands typically have a rolling landscape with steep slopes, and are dominated by herbaceous communities that grow on pasture land interspersed by shrubs. Land abandonment use to trigger an increase in soil erosion, but the vegetation recovery reduces the impact of the vegetation. The goal of this work is to assess the effects of different Mediterranean shrub species (Dorycnium pentaphyllum Scop., Medicago strasseri, Colutea arborescens L., Retama sphaerocarpa, L., Pistacia Lentiscus L. and Quercus coccifera L.) on soil protection (runoff and soil losses) and on rainfall reaching soil surface (rainfall partitioning fluxes). To characterize the effects of shrub vegetation and to evaluate their effects on soil protection, two field experiments were carried out. The presence of shrub vegetation reduced runoff by

  20. Effect of gypsum content on soil water retention

    NASA Astrophysics Data System (ADS)

    Moret-Fernández, D.; Herrero, J.

    2015-09-01

    Many gypsiferous soils occur in arid lands, where the water retention capacity of the soil is vital to plant life and crop production. This study investigated the effect of gypsum content on the gravimetric soil water retention curve (WRC). We analyzed calcium carbonate equivalent (CCE), equivalent gypsum content (EG), soil organic carbon content (SOC), and electrical conductivity of 43 samples collected from various horizons in soils in the Ebro Valley, NE Spain. The WRC of the fine earth was determined using the pressure-plate method (pressure heads = 0, -33, -100, -200, -500, and -1500 kPa), and the gravimetric water retention curves were fitted to the unimodal van Genuchten function. Soil gypsum content had a significant effect on water retention. Soils that had high gypsum content made WRC with higher water retention at near saturation conditions, and steeper WRC slopes. The EG threshold at which gypsum content had an effect on WRC was about 40%, and EG was positively and negatively correlated with the α and n parameters of the WRC, respectively.

  1. Microbial interaction networks in soil and in silico

    NASA Astrophysics Data System (ADS)

    Vetsigian, Kalin

    2012-02-01

    Soil harbors a huge number of microbial species interacting through secretion of antibiotics and other chemicals. What patterns of species interactions allow for this astonishing biodiversity to be sustained, and how do these interactions evolve? I used a combined experimental-theoretical approach to tackle these questions. Focusing on bacteria from the genus Steptomyces, known for their diverse secondary metabolism, I isolated 64 natural strains from several individual grains of soil and systematically measured all pairwise interactions among them. Quantitative measurements on such scale were enabled by a novel experimental platform based on robotic handling, a custom scanner array and automatic image analysis. This unique platform allowed the simultaneous capturing of ˜15,000 time-lapse movies of growing colonies of each isolate on media conditioned by each of the other isolates. The data revealed a rich network of strong negative (inhibitory) and positive (stimulating) interactions. Analysis of this network and the phylogeny of the isolates, together with mathematical modeling of microbial communities, revealed that: 1) The network of interactions has three special properties: ``balance'', ``bi- modality'' and ``reciprocity''; 2) The interaction network is fast evolving; 3) Mathematical modeling explains how rapid evolution can give rise to the three special properties through an interplay between ecology and evolution. These properties are not a result of stable co-existence, but rather of continuous evolutionary turnover of strains with different production and resistance capabilities.

  2. Response of forest seedling/soil microcosms to elevated CO{sub 2} and soil temperature, water, and light: Carbon and nitrogen mineralization and allocation

    SciTech Connect

    Gillham, M.L.; Perry, D.A.

    1995-09-01

    Soils from 500-year-old old-growth Douglas-fir forests in the western Oregon Cascade Mtns. (945m and 1325m sites) were {open_quotes}incubated{close_quotes} for 32 weeks in controlled-environment chambers. Objectives were (1) to determine the interacting effects of soil temperature and atmospheric CO{sub 2} on N availability in soils, growth of Douglas-fir seedlings, and resulting C & N fluxes among trees, soils, and the atmosphere, and (2) to model these interactions with a version of Fregro linked with the GEM soil-decomposition model. The experiment was a split-plot with a factorial treatment combination containing two leves each of atmospheric CO{sub 2} (350/700 ppm), soil temperature (13.8/17.7{degrees}C), soil C & N (1325m soils had 2.3x more C and 1.25x more N than 945m soils), and vegetation (+/-seedlings). Each wholeplot (chamber) treatment (CO{sub 2} x temperature) was replicated three times. Photosynthetic photon flux density, soil temperature, and volume of added water were determined for each pot and analyzed as covariates. Responses measured include differences in soil C & N mineralization and total soil C & N in the presence/absence of seedlings, the extent to which subsequent seedling growth offsets potential {open_quote}system{close_quote} losses of C & N, and allocation of C & N to foliage and fine roots. Previously reported early results (ESA, 1994) suggest that (1) as hypothesized, soil temperatures is the main driver of changes in both N mineralization and biomass production in seedling microcosms, (2) allocation is primarily influenced by atmospheric CO{sub 2} concentration, and (3) a soil type x soil temperature x CO{sub 2} interaction influences seedling growth.

  3. Soil Management Plan For The Potable Water System Upgrades Project

    SciTech Connect

    Field, S. M.

    2007-04-01

    This plan describes and applies to the handling and management of soils excavated in support of the Y-12 Potable Water Systems Upgrades (PWSU) Project. The plan is specific to the PWSU Project and is intended as a working document that provides guidance consistent with the 'Soil Management Plan for the Oak Ridge Y-12 National Security Complex' (Y/SUB/92-28B99923C-Y05) and the 'Record of Decision for Phase II Interim Remedial Actions for Contaminated Soils and Scrapyard in Upper East Fork Popular Creek, Oak Ridge, Tennessee' (DOE/OR/01-2229&D2). The purpose of this plan is to prevent and/or limit the spread of contamination when moving soil within the Y-12 complex. The major feature of the soil management plan is the decision tree. The intent of the decision tree is to provide step-by-step guidance for the handling and management of soil from excavation of soil through final disposition. The decision tree provides a framework of decisions and actions to facilitate Y-12 or subcontractor decisions on the reuse of excavated soil on site and whether excavated soil can be reused on site or managed as waste. Soil characterization results from soil sampling in support of the project are also presented.

  4. Soil water samplers in ion balance studies on acidic forest soils

    SciTech Connect

    Rasmussen, L.; Joergensen, P.; Kruse, S.

    1986-04-01

    During the last years an increasing consciousness has appeared of the injurious effects of acid rain on the forest ecosystems both in Europe and North America. At several localities ion balance studies have been implemented in order to evaluate the impact of the atmospheric deposition of acidic substances and heavy metals on the forest ecosystem. In many localities the leaching of material to the ground water or output from the ecosystem has to be determined by means of tensiometer measurements and soil water sampling. Many different soil water samplers are available on the market and they show useful applicability under the given circumstances. But in many cases soil water samples taken with different equipment give incommensurable results leading to differing explanations of the effects of acid precipitation on elements and their cycling in the ecosystem. The purpose of the present study is twofold. Firstly, the sorption characteristics of different types of soil water samplers are examined under acidic soil conditions both by installation in the field and by laboratory experiments. Secondly, a new method is introduced for current and constant soil water sampling under varying soil suctions in the unsaturated zone.

  5. Soil Surface Structure: A key factor for the degree of soil water repellency

    NASA Astrophysics Data System (ADS)

    Ahn, S.; Doerr, S. H.; Douglas, P.; Bryant, R.; Hamlett, C.; McHale, G.; Newton, M.; Shirtcliffe, N.

    2012-04-01

    Despite of considerable efforts, the degree of water repellency has not always been fully explained by chemical property of soil (termed hydrophobicity). That might be because the structure of a soil surface was not considered properly, which is another main factor determining the severity of soil water repellency. Surface structure has only recently been considered in soil science, whilst it has been paid attention for several decades in materials science due to its relevance to industrial applications. In this contribution, comparison of critical contact angles measured on different surface structures (made with glass beads, glass shards and beach sands) is presented and the effect of surface structure on manifestation of soil water repellency is discussed in terms of several different variables such as the individual particles shape, and areal and structural factors of the actual surface.

  6. Difficulties in the evaluation and measuring of soil water infiltration

    NASA Astrophysics Data System (ADS)

    Pla-Sentís, Ildefonso

    2013-04-01

    Soil water infiltration is the most important hydrological parameter for the evaluation and diagnosis of the soil water balance and soil moisture regime. Those balances and regimes are the main regulating factors of the on site water supply to plants and other soil organisms and of other important processes like runoff, surface and mass erosion, drainage, etc, affecting sedimentation, flooding, soil and water pollution, water supply for different purposes (population, agriculture, industries, hydroelectricity), etc. Therefore the evaluation and measurement of water infiltration rates has become indispensable for the evaluation and modeling of the previously mentioned processes. Infiltration is one of the most difficult hydrological parameters to evaluate or measure accurately. Although the theoretical aspects of the process of soil water infiltration are well known since the middle of the past century, when several methods and models were already proposed for the evaluation of infiltration, still nowadays such evaluation is not frequently enough accurate for the purposes being used. This is partially due to deficiencies in the methodology being used for measuring infiltration, including some newly proposed methods and equipments, and in the use of non appropriate empirical models and approaches. In this contribution we present an analysis and discussion about the main difficulties found in the evaluation and measurement of soil water infiltration rates, and the more commonly committed errors, based on the past experiences of the author in the evaluation of soil water infiltration in many different soils and land conditions, and in their use for deducing soil water balances under variable and changing climates. It is concluded that there are not models or methods universally applicable to any soil and land condition, and that in many cases the results are significantly influenced by the way we use a particular method or instrument, and by the alterations in the soil

  7. A multimedia and interactive approach to teach soil science

    NASA Astrophysics Data System (ADS)

    Badía-Villas, D.; Martí-Dalmau, C.; Iñiguez-Remón, E.

    2012-04-01

    Soil Science is a discipline concerned with a material that has unique features and behaviours (Churchman, 2010). Thus, teachers of Soil Science need to be experienced with Soil Science practices and must appreciate the complexities and relationships inherent within the discipline (Field et al, 2011). But when soil science had to be taught not by specialists, for instance in the introductory courses of earth and environmental sciences Degrees or in Secondary School, adequate material cannot be found. For this reason, multimedia and interactive programmes have been developed and showed here. EDAFOS is an e-learning resource that provides a comprehensive review of the fundamental concepts on soil science and reveals it as the living skin of planet Earth (European Commission, 2006). This programme is available via website (www.cienciadelsuelo.es) both in Spanish and, more recently, also in English. Edafos is a programme with different modules, which after outlining the study of soil components goes on to examine the main factors and processes of soil genesis explaining the mechanisms of soil processes. By the use of animations, the vital functions of soil are explained. The program ends with a section of multiple-choice exercises with self-assessment. To complement this program, virtual visits to the field are showed in the program iARASOL (www.suelosdearagon.es), in a time when field trips are gradually diminishing due to insufficiency in time and budget, as well as safety concerns (Çaliskan, 2011). In this case, the objective of iARASOL is to set out that soil vary from place to place not randomly, but in a systematic way, according to landscape units; therefore, graduates can classify the soils using the WRB system (IUSS, 2007). It presents diverse types of data and images instantly, from a variety of viewpoints, at many different scales and display non-visual information in the field. Both programs provide an additional source of information to supplement

  8. Pore-water chemistry explains zinc phytotoxicity in soil.

    PubMed

    Kader, Mohammed; Lamb, Dane T; Correll, Ray; Megharaj, Mallavarapu; Naidu, Ravi

    2015-12-01

    Zinc (Zn) is a widespread soil contaminant arising from a numerous anthropogenic sources. However, adequately predicting toxicity of Zn to ecological receptors remains difficult due to the complexity of soil characteristics. In this study, we examined solid-solution partitioning using pore-water data and toxicity of Zn to cucumber (Cucumis sativus L.) in spiked soils. Pore-water effective concentration (ECx, x=10%, 20% and 50% reduction) values were negatively related to pH, indicating lower Zn pore water concentration were needed to cause phytotoxicity at high pH soils. Total dissolved zinc (Znpw) and free zinc (Zn(2+)) in soil-pore water successfully described 78% and 80.3% of the variation in relative growth (%) in the full dataset. When the complete data set was used (10 soils), the estimated EC50pw was 450 and 79.2 µM for Znpw and Zn(2+), respectively. Total added Zn, soil pore water pH (pHpw) and dissolve organic carbon (DOC) were the best predictors of Znpw and Zn(2+) in pore-water. The EC10 (total loading) values ranged from 179 to 5214 mg/kg, depending on soil type. Only pH measurements in soil were related to ECx total Zn data. The strongest relationship to ECx overall was pHca, although pHw and pHpw were in general related to Zn ECx. Similarly, when a solution-only model was used to predict Zn in shoot, DOC was negatively related to Zn in shoot, indicating a reduction in uptake/ translocation of Zn from solution with increasing DOC. PMID:26283289

  9. Hexagonal boron nitride and water interaction parameters

    NASA Astrophysics Data System (ADS)

    Wu, Yanbin; Wagner, Lucas K.; Aluru, Narayana R.

    2016-04-01

    The study of hexagonal boron nitride (hBN) in microfluidic and nanofluidic applications at the atomic level requires accurate force field parameters to describe the water-hBN interaction. In this work, we begin with benchmark quality first principles quantum Monte Carlo calculations on the interaction energy between water and hBN, which are used to validate random phase approximation (RPA) calculations. We then proceed with RPA to derive force field parameters, which are used to simulate water contact angle on bulk hBN, attaining a value within the experimental uncertainties. This paper demonstrates that end-to-end multiscale modeling, starting at detailed many-body quantum mechanics and ending with macroscopic properties, with the approximations controlled along the way, is feasible for these systems.

  10. Hexagonal boron nitride and water interaction parameters.

    PubMed

    Wu, Yanbin; Wagner, Lucas K; Aluru, Narayana R

    2016-04-28

    The study of hexagonal boron nitride (hBN) in microfluidic and nanofluidic applications at the atomic level requires accurate force field parameters to describe the water-hBN interaction. In this work, we begin with benchmark quality first principles quantum Monte Carlo calculations on the interaction energy between water and hBN, which are used to validate random phase approximation (RPA) calculations. We then proceed with RPA to derive force field parameters, which are used to simulate water contact angle on bulk hBN, attaining a value within the experimental uncertainties. This paper demonstrates that end-to-end multiscale modeling, starting at detailed many-body quantum mechanics and ending with macroscopic properties, with the approximations controlled along the way, is feasible for these systems. PMID:27131542

  11. Soil water repellency characteristic curves for soil profiles with natural organic carbon gradients

    NASA Astrophysics Data System (ADS)

    Kawamoto, Ken; Müller, Karin; Moldrup, Per; de Jonge, Lis; Clothier, Brent; Hiradate, Syuntaro; Komatsu, Toshiko

    2014-05-01

    Soil water repellency (SWR) is a phenomenon that influences many soil hydrologic processes such as reduction of infiltration, increase in overland flow, and enhanced preferential flow. SWR has been observed in various soil types and textures, and the degree of SWR is greatly controlled by soil moisture content and levels of organic matter and clay. One of the key topics in SWR research is how to describe accurately the seasonal and temporal variation of SWR with the controlling factors such as soil moisture, organic matter, and clay contents for soil profiles with natural organic carbon gradients. In the present study, we summarize measured SWR data for soil profiles under different land uses and vegetation in Japan and New Zealand, and compared these with literature data. We introduce the contact angle-based evaluation of SWR and predictive models for soil water repellency characteristic curves, in which the contact angle is a function of the moisture content. We also discuss a number of novel concepts, including i) the reduction in the contact angle with soil-water contact time to describe the time dependence of SWR, ii) the relationship between the contact angles from the measured scanning curves under controlled wetting and drying cycles, and iii) the initial contact angles measured by the sessile drop method.

  12. Soil permittivity response to bulk electrical conductivity for selected soil water sensors

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Bulk electrical conductivity can dominate the low frequency dielectric loss spectrum in soils, masking changes in the real permittivity and causing errors in estimated water content. We examined the dependence of measured apparent permittivity (Ka) on bulk electrical conductivity in contrasting soil...

  13. Molecular Indicators of Soil Humification and Interaction with Heavy Metals

    SciTech Connect

    Fan, Teresa W.-M.; Higashi, Richard M.; Cassel, Teresa; Green, Peter; Lane, Andrew N.

    2003-03-26

    For stabilization of heavy metals at contaminated sites, interaction of soil organic matter (SOM) with heavy metal ions is critically important for long-term sustainability, a factor that is poorly understood at the molecular level. Using 13C- and 15N-labeled soil humates (HS), we investigated the turnover of five organic amendments (celluose, wheat straw, pine shavings, chitin and bone meal) in relation to heavy metal ion leaching in soil column experiments. The labeled molecular substructures in HS were examined by multinuclear 2-D NMR and pyrolysis GC-MS while the element profile in the leachates was analyzed by ICP-MS. Preliminary analysis revealed that peptidic and polysaccharidic structures were highly enriched, which suggests their microbial origin. Cd(II) leaching was significantly attenuated with humification of lignocellulosic materials. Correlation of 13C and 15N turnovers of HS substructures to metal leaching is underway.

  14. An index for plant water deficit based on root-weighted soil water content

    NASA Astrophysics Data System (ADS)

    Shi, Jianchu; Li, Sen; Zuo, Qiang; Ben-Gal, Alon

    2015-03-01

    Governed by atmospheric demand, soil water conditions and plant characteristics, plant water status is dynamic, complex, and fundamental to efficient agricultural water management. To explore a centralized signal for the evaluation of plant water status based on soil water status, two greenhouse experiments investigating the effect of the relative distribution between soil water and roots on wheat and rice were conducted. Due to the significant offset between the distributions of soil water and roots, wheat receiving subsurface irrigation suffered more from drought than wheat under surface irrigation, even when the arithmetic averaged soil water content (SWC) in the root zone was higher. A significant relationship was found between the plant water deficit index (PWDI) and the root-weighted (rather than the arithmetic) average SWC over root zone. The traditional soil-based approach for the estimation of PWDI was improved by replacing the arithmetic averaged SWC with the root-weighted SWC to take the effect of the relative distribution between soil water and roots into consideration. These results should be beneficial for scheduling irrigation, as well as for evaluating plant water consumption and root density profile.

  15. Soil water content plays an important role in soil-atmosphere exchange of carbonyl sulfide (OCS)

    NASA Astrophysics Data System (ADS)

    Yi, Zhigang; Behrendt, Thomas; Bunk, Rüdiger; Wu, Dianming; Kesselmeier, Jürgen

    2016-04-01

    Carbonyl sulfide (OCS) is a quite stable gas in the troposphere and is transported up to the stratosphere, where it contributes to the sulfate aerosol layer (Crutzen 1976). The tropospheric concentration seems to be quite constant, indicating a balance between sinks and sources. Recent work by Sandoval-Soto et al. (2005) demonstrated the enormous strength of the vegetation sink and the urgent needs to understand the sinks and sources. The role of soils is a matter of discussion (Kesselmeier et al., 1999; Van Diest and Kesselmeier, 2008; Maseyk et al., 2014; Whelan et al., 2015). To better understand the influence of soil water content and OCS mixing ratio on OCS fluxes, we used an OCS analyzer (LGR COS/CO Analyzer 907-0028, Los Gatos, CA, USA) coupled with automated soil chamber system (Behrendt et al., 2014) to measure the OCS fluxes with a slow drying of four different types of soil (arable wheat soil in Mainz, blueberry soil in Waldstein, spruce soil in Waldstein and needle forest soil in Finland). Results showed that OCS fluxes as well as the optimum soil water content for OCS uptake varied significantly for different soils. The net production rates changed significantly with the soil drying out from 100% to about 5% water holding capacity (WHC), implying that soil water content play an important role in the uptake processes. The production and uptake processes were distinguished by the regression of OCS fluxes under different OCS mixing ratios. OCS compensation points (CP) were found to differ significantly for different soil types and water content, with the lowest CP at about 20% WHC, implying that when estimating the global budgets of OCS, especially for soils fluxes, soil water content should be taken into serious consideration. References Crutzen, P. J. 1976, Geophys. Res. Lett., 3, 73-76. Sandoval-Soto, L. et al., 2005, Biogeosciences, 2, 125-132. Kesselmeier, J. et al., 1999, J. Geophys. Res., 104, 11577-11584. Van Diest, H. and Kesselmeier, J. 2008

  16. Presence and distribution of wastewater-derived pharmaceuticals in soil irrigated with reclaimed water

    USGS Publications Warehouse

    Kinney, C.A.; Furlong, E.T.; Werner, S.L.; Cahill, J.D.

    2006-01-01

    Three sites in the Front Range of Colorado, USA, were monitored from May through September 2003 to assess the presence and distribution of pharmaceuticals in soil irrigated with reclaimed water derived from urban wastewater. Soil cores were collected monthly, and 19 pharmaceuticals, all of which were detected during the present study, were measured in 5-cm increments of the 30-cm cores. Samples of reclaimed water were analyzed three times during the study to assess the input of pharmaceuticals. Samples collected before the onset of irrigation in 2003 contained numerous pharmaceuticals, likely resulting from the previous year's irrigation. Several of the selected pharmaceuticals increased in total soil concentration at one or more of the sites. The four most commonly detected pharmaceuticals were erythromycin, carbamazepine, fluoxetine, and diphenhydramine. Typical concentrations of the individual pharmaceuticals observed were low (0.02-15 ??g/kg dry soil). The existence of subsurface maximum concentrations and detectable concentrations at the lowest sampled soil depth might indicate interactions of soil components with pharmaceuticals during leaching through the vadose zone. Nevertheless, the present study demonstrates that reclaimed-water irrigation results in soil pharmaceutical concentrations that vary through the irrigation season and that some compounds persist for months after irrigation. ?? 2006 SETAC.

  17. Fates and transport of PPCPs in soil receiving reclaimed water irrigation.

    PubMed

    Chen, Weiping; Xu, Jian; Lu, Sidan; Jiao, Wentao; Wu, Laosheng; Chang, Andrew C

    2013-11-01

    Fates and transport of 9 commonly found PPCPs of the reclaimed water were simulated based on the HYDRUS-1D software that was validated with data generated from field experiments. Under the default scenario in which the model parameters and input data represented the typical conditions of turf grass irrigation in southern California, the adsorption, degradation, and volatilization of clofibric acid, ibuprofen, 4-tert-octylphenol, 4-n-nonylphenol, naproxen, triclosan, diclofenac sodium, bisphenol A and estrone in the receiving soils were tracked for 10 years. At the end, their accumulations in the 90 cm soil profile varied from less than 1 ng g(-1) to about 140 ng g(-1) and their concentrations in the drainage water in the 90 cm soil depth varied from nil to μg L(-1) levels. The adsorption and microbial degradation processes interacted to contain the PPCPs entirely within surface 40 cm of the soil profiles. Leaching and volatilization were not significant processes governing the PPCPs in the soils. The extent of accumulations in the soils did not appear to produce undue ecological risks to the soil biota. PPCPs did not represent any potential environmental harm in reclaimed water irrigation. PMID:24148973

  18. A process-based evapotranspiration model incorporating coupled soil water-atmospheric controls

    NASA Astrophysics Data System (ADS)

    Haghighi, Erfan; Kirchner, James

    2016-04-01

    Despite many efforts to develop evapotranspiration models (in the framework of the Penman-Monteith equation) with improved parametrizations of various resistance terms to water vapor transfer into the atmosphere, evidence suggests that estimates of evapotranspiration and its partitioning are prone to bias. Much of this bias could arise from the exclusion of surface hydro-thermal properties and of physical interactions close to the surface where heat and water vapor fluxes originate. Recent progress has been made in mechanistic modeling of surface-turbulence interactions, accounting for localized heat and mass exchange rates from bare soil surfaces covered by protruding obstacles. We seek to extend these results partially vegetated surfaces, to improve predictive capabilities and accuracy of remote sensing techniques quantifying evapotranspiration fluxes. The governing equations of liquid water, water vapor, and energy transport dynamics in the soil-plant-atmosphere system are coupled to resolve diffusive vapor fluxes from isolated pores (plant stomata and soil pores) across a near-surface viscous sublayer, explicitly accounting for pore-scale transport mechanisms and environmental forcing. Preliminary results suggest that this approach offers unique opportunities for directly linking transport properties in plants and adjacent bare soil with resulting plant transpiration and localized bare soil evaporation rates. It thus provides an essential building block for interpreting and upscaling results to field and landscape scales for a range of vegetation cover and atmospheric conditions.

  19. Water table fluctuations and soil biogeochemistry: An experimental approach using an automated soil column system

    NASA Astrophysics Data System (ADS)

    Rezanezhad, F.; Couture, R.-M.; Kovac, R.; O'Connell, D.; Van Cappellen, P.

    2014-02-01

    Water table fluctuations significantly affect the biological and geochemical functioning of soils. Here, we introduce an automated soil column system in which the water table regime is imposed using a computer-controlled, multi-channel pump connected to a hydrostatic equilibrium reservoir and a water storage reservoir. The potential of this new system is illustrated by comparing results from two columns filled with 45 cm of the same homogenized riparian soil. In one soil column the water table remained constant at -20 cm below the soil surface, while in the other the water table oscillated between the soil surface and the bottom of the column, at a rate of 4.8 cm d-1. The experiment ran for 75 days at room temperature (25 ± 2 °C). Micro-sensors installed at -10 and -30 cm below the soil surface in the stable water table column recorded constant redox potentials on the order of 600 and -200 mV, respectively. In the fluctuating water table column, redox potentials at the same depths oscillated between oxidizing (∼700 mV) and reducing (∼-100 mV) conditions. Pore waters collected periodically and solid-phase analyses on core material obtained at the end of the experiment highlighted striking geochemical differences between the two columns, especially in the time series and depth distributions of Fe, Mn, K, P and S. Soil CO2 emissions derived from headspace gas analysis exhibited periodic variations in the fluctuating water table column, with peak values during water table drawdown. Transient redox conditions caused by the water table fluctuations enhanced microbial oxidation of soil organic matter, resulting in a pronounced depletion of particulate organic carbon in the midsection of the fluctuating water table column. Denaturing Gradient Gel Electrophoresis (DGGE) revealed the onset of differentiation of the bacterial communities in the upper (oxidizing) and lower (reducing) soil sections, although no systematic differences in microbial community structure

  20. Water, solute and heat transport in the soil: the Australian connection

    NASA Astrophysics Data System (ADS)

    Knight, John

    2016-04-01

    The interest of Peter Raats in water, solute and heat transport in the soil has led to scientific and/or personal interactions with several Australian scientists such as John Philip, David Smiles, Greg Davis and John Knight. Along with John Philip and Robin Wooding, Peter was an early user of the Gardner (1958) linearised model of soil water flow, which brought him into competition with John Philip. I will discuss some of Peter's solutions relevant to infiltration from line and point sources, cavities and basins. A visit to Canberra, Australia in the early 1980s led to joint work on soil water flow, and on combined water and solute movement with David Smiles and others. In 1983 Peter was on the PhD committee for Greg Davis at the University of Wollongong, and some of the methods in his thesis 'Mathematical modelling of rate-limiting mechanisms of pyritic oxidation in overburden dumps' were later used by Peter's student Sjoerd van der Zee. David Smiles and Peter wrote a survey article 'Hydrology of swelling clay soils' in 2005. In the last decade Peter has been investigating the history of groundwater and vadose zone hydrology, and recently he and I have been bringing to light the largely forgotten work of Lewis Fry Richardson on finite difference solution of the heat equation, drainage theory, soil physics, and the soil-plant-atmosphere continuum.

  1. COSMOS soil water sensing affected by crop biomass and water status

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water sensing methods are widely used to characterize water content in the root zone and below, but only a few are capable of sensing soil volumes larger than a few hundred liters. Scientists with the USDA-ARS Conservation & Production Research Laboratory, Bushland, Texas, evaluated: a) the Cos...

  2. Multiple interactive pollutants in water quality trading.

    PubMed

    Sarang, Amin; Lence, Barbara J; Shamsai, Abolfazl

    2008-10-01

    Efficient environmental management calls for the consideration of multiple pollutants, for which two main types of transferable discharge permit (TDP) program have been described: separate permits that manage each pollutant individually in separate markets, with each permit based on the quantity of the pollutant or its environmental effects, and weighted-sum permits that aggregate several pollutants as a single commodity to be traded in a single market. In this paper, we perform a mathematical analysis of TDP programs for multiple pollutants that jointly affect the environment (i.e., interactive pollutants) and demonstrate the practicality of this approach for cost-efficient maintenance of river water quality. For interactive pollutants, the relative weighting factors are functions of the water quality impacts, marginal damage function, and marginal treatment costs at optimality. We derive the optimal set of weighting factors required by this approach for important scenarios for multiple interactive pollutants and propose using an analytical elasticity of substitution function to estimate damage functions for these scenarios. We evaluate the applicability of this approach using a hypothetical example that considers two interactive pollutants. We compare the weighted-sum permit approach for interactive pollutants with individual permit systems and TDP programs for multiple additive pollutants. We conclude by discussing practical considerations and implementation issues that result from the application of weighted-sum permit programs. PMID:18584238

  3. Multiple Interactive Pollutants in Water Quality Trading

    NASA Astrophysics Data System (ADS)

    Sarang, Amin; Lence, Barbara J.; Shamsai, Abolfazl

    2008-10-01

    Efficient environmental management calls for the consideration of multiple pollutants, for which two main types of transferable discharge permit (TDP) program have been described: separate permits that manage each pollutant individually in separate markets, with each permit based on the quantity of the pollutant or its environmental effects, and weighted-sum permits that aggregate several pollutants as a single commodity to be traded in a single market. In this paper, we perform a mathematical analysis of TDP programs for multiple pollutants that jointly affect the environment (i.e., interactive pollutants) and demonstrate the practicality of this approach for cost-efficient maintenance of river water quality. For interactive pollutants, the relative weighting factors are functions of the water quality impacts, marginal damage function, and marginal treatment costs at optimality. We derive the optimal set of weighting factors required by this approach for important scenarios for multiple interactive pollutants and propose using an analytical elasticity of substitution function to estimate damage functions for these scenarios. We evaluate the applicability of this approach using a hypothetical example that considers two interactive pollutants. We compare the weighted-sum permit approach for interactive pollutants with individual permit systems and TDP programs for multiple additive pollutants. We conclude by discussing practical considerations and implementation issues that result from the application of weighted-sum permit programs.

  4. Implementation of Automated Infiltration Soil Water Sampler: Application to Unsaturated Soil in Dune Fields

    NASA Astrophysics Data System (ADS)

    Higashi, N.; Inoue, M.; Mori, Y.

    2003-12-01

    Accurate measurement and sampling of infiltration water from root zone are necessary to understand soil and groundwater contamination processes. The traditional instruments for sampling water leaching below the root zone cause divergence or bypass of the water flow around the instrument itself. That results in undesired soil water profile and inaccurate sampling. A suction controlled lysimeter, which consists of porous plate connected to an automated vacuum system and tensiometers has developed. Soil matric pressure heads are measured just above the porous plate that installed horizontally and at the same depth in the natural soil profile. The vacuum system is automatically controlled so that the readings of the matric pressure heads match each other. This instrument does not disturb the water flow and the water sampling flux (qe) is almost similar to that of natural infiltration flux (qd). However, for sandy soils, porous plate would show some resistance to flow and soil water could easily accumulate above the porous plate. We improved the existing automated water sampler in order to measure the unsaturated zone in dune fields. High flow rate glass filters with different pore size; 0.02 to 0.03 mm (G3), 0.005 to 0.01 mm (G4), and 0.002 to 0.005 mm (G5) were studied in laboratory instead of the traditionally used porous plate. In the unsaturated steady-state water flow experiment, the value of vacuum pressure was set manually in reference to retention curve of dune sand. The water sampling flux measured by these samplers corresponded well with the irrigation flux (qi) when a suction of 60 cm H2O was applied to G4 and G5 filters. Four different irrigation fluxes were studied. The average water collecting efficiency (WCE = qe divided by qi) was 118 percent for G4 and 147 percent for G5. We concluded that glass filter, especially, G4 filter was suitable as soil water sampler in dune fields. Finally, the improved sampler using G4 filter was buried into a lysimeter (120

  5. Water and heat transport in boreal soils: Implications for soil response to climate change

    USGS Publications Warehouse

    Fan, Z.; Neff, J.C.; Harden, J.W.; Zhang, T.; Veldhuis, H.; Czimczik, C.I.; Winston, G.C.; O'Donnell, J. A.

    2011-01-01

    Soil water content strongly affects permafrost dynamics by changing the soil thermal properties. However, the movement of liquid water, which plays an important role in the heat transport of temperate soils, has been under-represented in boreal studies. Two different heat transport models with and without convective heat transport were compared to measurements of soil temperatures in four boreal sites with different stand ages and drainage classes. Overall, soil temperatures during the growing season tended to be over-estimated by 2-4??C when movement of liquid water and water vapor was not represented in the model. The role of heat transport in water has broad implications for site responses to warming and suggests reduced vulnerability of permafrost to thaw at drier sites. This result is consistent with field observations of faster thaw in response to warming in wet sites compared to drier sites over the past 30. years in Canadian boreal forests. These results highlight that representation of water flow in heat transport models is important to simulate future soil thermal or permafrost dynamics under a changing climate. ?? 2011 Elsevier B.V.

  6. Interactions between soil biota and the effects on geomorphological features

    NASA Astrophysics Data System (ADS)

    Zaitlin, Beryl; Hayashi, Masaki

    2012-07-01

    The interaction of animals with abiotic features of their environment has long been known to cause alterations to geomorphic features, and these interactions may cause feedback loops that further alter geomorphic features and animal communities. This paper samples the literature on selected burrowing animals in western North America, and discusses the interactions of animals with abiotic features of the environment and with each other, and the resulting impacts on geomorphic features and each other. As expected, burrowing characteristics of animals influence geomorphological processes. For example, pocket gophers and certain ground squirrels that burrow horizontal tunnels on sloping grounds seem to have significant impacts on horizontal movement of soils, whereas prairie dogs and harvester ants have more impact on vertical movement of soils. Burrowing animals, in general, increase the patchiness of the environment, which creates localized patch habitat for other plants and animals, thereby increasing biodiversity at the landscape scale. Burrowing animals influence and are influenced by microbes: sylvatic plague wiped out large populations of prairie dogs, earthworms cause major changes in soil microflora, pocket gophers and harvester ants cause changes in mycorrhizal communities, which in turn impact plant communities.

  7. Water use, productivity and interactions among desert plants

    SciTech Connect

    Ehleringer, J.R.

    1992-11-17

    Water plays a central role affecting all aspects of the dynamics in aridland ecosystems. Productivity, stability, and competitive interactions among ecosystem components within aridlands are key processes related directly to water in deserts. The ecological studies in this project revolve around one fundamental premise: that integrated aspects of plant metabolism provide insight into the structure and function of plant communities and ecosystems. While it is difficult to extrapolate from instantaneous physiological observations to higher scales, such as whole plant performance or to interactions between plants as components of ecosystems, several key aspects of plant metabolism are scalable. Analyses of stable isotopic composition in plant tissues at natural abundance levels provide a useful tool that can provide insight into the consequences of physiological processes over temporal and spatial scales. Some plant processes continuously fractionate among light and heavy stable isotopic forms of an element; over time this results in integrated measures of plant metabolism. For example, carbon isotope fractionation during photosynthesis results in leaf carbon isotopic composition that is a measure of the set-point for photosynthetic metabolism and of water-use efficiency. Thus it provides information on the temporal scaling of a key physiological process. In contrast, hydrogen is not fractionated during water uptake through the root. Soil water availability in shallow, deep, and/or groundwater layers vary spatially; therefore hydrogen isotope ratios of xylem sap provide a direct measure of the water source currently used by a plant. The longer-term record of carbon and hydrogen isotope ratios is recorded annually in xylem tissues (tree rings). The research in this project addresses variation in stable isotopic composition of aridland plants and its consequences for plant performance and community-level interactions.

  8. Difficulties in the evaluation and measuring of soil water infiltration

    NASA Astrophysics Data System (ADS)

    Pla-Sentís, Ildefonso

    2013-04-01

    Soil water infiltration is the most important hydrological parameter for the evaluation and diagnosis of the soil water balance and soil moisture regime. Those balances and regimes are the main regulating factors of the on site water supply to plants and other soil organisms and of other important processes like runoff, surface and mass erosion, drainage, etc, affecting sedimentation, flooding, soil and water pollution, water supply for different purposes (population, agriculture, industries, hydroelectricity), etc. Therefore the evaluation and measurement of water infiltration rates has become indispensable for the evaluation and modeling of the previously mentioned processes. Infiltration is one of the most difficult hydrological parameters to evaluate or measure accurately. Although the theoretical aspects of the process of soil water infiltration are well known since the middle of the past century, when several methods and models were already proposed for the evaluation of infiltration, still nowadays such evaluation is not frequently enough accurate for the purposes being used. This is partially due to deficiencies in the methodology being used for measuring infiltration, including some newly proposed methods and equipments, and in the use of non appropriate empirical models and approaches. In this contribution we present an analysis and discussion about the main difficulties found in the evaluation and measurement of soil water infiltration rates, and the more commonly committed errors, based on the past experiences of the author in the evaluation of soil water infiltration in many different soils and land conditions, and in their use for deducing soil water balances under variable and changing climates. It is concluded that there are not models or methods universally applicable to any soil and land condition, and that in many cases the results are significantly influenced by the way we use a particular method or instrument, and by the alterations in the soil

  9. Water repellency in highly managed soils and turfgrass - How our understanding has changed in the past 20 years.

    NASA Astrophysics Data System (ADS)

    Kostka, Stan; McMillan, Mica; Oostindie, Klaas; Dekker, Louis; Cisar, John; Leinauer, Bernd; Fidanza, Michael; Bigelow, Cale; Ritsema, Coen

    2014-05-01

    Over the past 20 years, a major shift has occurred in how turfgrass managers deal with soil water repellency. Initially, water management strategies focused solely on remediating localized dry spots, the visible effects of hydrophobic soils. Nearly a decade ago at this conference, a group of turfgrass scientists participated in this session on soil water repellency interacting with a broad group of soil physicists setting in motion research, collaborations and discoveries that have resulted in not only a better understanding of the implications of this phenomenon on soil hydraulic properties and plant productivity, but also, development of new strategies, particularly surfactants, to improve water capture, reduce preferential flow, increase irrigation and water use efficiency, improve performance of soil directed pesticides, reduce leaching of nitrogen, increase mineralization of organically bound nitrogen, and enhance plant tolerance to abiotic stress. It also resulted in research utilizing soil moisture measurement tools, specifically, TDR and capacitance probes, which were introduced to and accepted by soil and crop scientists working in amenity turfgrass. Within the past five years, these technologies and strategies for their effective utilization have transitioned from the research community to become accepted by turfgrass managers globally. It is the objective of this presentation to illustrate key discoveries, implications to improved water and resource utilization, and the resulting acceptance of them as new, more sustainable soil management practices.

  10. The impact of the soil surface properties in water erosion seen through LandSoil model sensitivity analysis

    NASA Astrophysics Data System (ADS)

    Ciampalini, Rossano; Follain, Stéphane; Cheviron, Bruno; Le Bissonnais, Yves; Couturier, Alain; Walter, Christian

    2014-05-01

    Quantitative models of soil redistribution at the landscape scale are the current tools for understanding space-time processes in soil and landscape evolution. But models use larger and larger numbers of variables and sometimes it becomes difficult to understand their relative importance and model behaviours in critical conditions. Sensitivity analysis (SA) is widely used to clarify models behaviours, their structure giving fundamental information to ameliorate models their selves. We tested the LandSoil model (LANDscape design for SOIL conservation under soil use and climate change) a model designed for the analysis of agricultural landscape evolution at a fine spatial resolution scale [1-10 meters] and a mid-term temporal scale [10-100 years]. LandSoil is suitable for simulations from parcel to catchment scale. It is spatially distributed, event-based, and considers water and tillage erosion processes that use a dynamic representation of the agricultural landscape through parameters such as a monthly representation of soil surface properties. Our aim was to identify most significant parameters driving the model and to highlight potential particular/singular behaviours of parameter combinations and relationships. The approach was to use local sensitivity analysis, also termed 'one-factor-at-time' (OAT) which consists of a deterministic, derivative method, inquiring the local response O to a particular input factor Pi at a specified point P0 within the full input parameter space of the model expressed as: δO/δP = (O2-O1) / (P2-P1) The local sensitivity represents the partial derivatives of O with respect to Pi at the point P0. In the SA procedure the topographical entity is represented by a virtual hillslope on which soil loss and sensitivity are calculated. Virtual hillslope is inspired from the virtual catchment framework proposed by Cheviron at al. (2011): a fixed topology consisting of a 3X3 square pixel structure having 150 m length allowing to test

  11. Responses of soil respiration to elevated CO2, air warming, and changing soil water availability in an old-field grassland

    SciTech Connect

    Wan, Shiqiang; Norby, Richard J; Childs, Joanne; Weltzin, Jake

    2007-01-01

    Responses of soil respiration to atmospheric and climatic change will have profound impacts on ecosystem and global C cycling in the future. This study was conducted to examine effects on soil respiration of the concurrent driving factors of elevated atmospheric CO2 concentration, rising temperature, and changing precipitation in a constructed old-field grassland in eastern Tennessee, USA. Model ecosystems of seven old-field species in 12 open-top chambers (4 m in diameter) were treated with two CO2 (ambient and ambient plus 300 ppm) and two temperature (ambient and ambient plus 3 C) levels. Two split plots with each chamber were assigned with high and low soil moisture levels. During the 19-month experimental period from June 2003 to December 2004, higher CO2 concentration and soil water availability significantly increased mean soil respiration by 35.8% and 15.7%, respectively. The effects of air warming on soil respiration varied seasonally from small reductions to significant increases to no response, and there was no significant main effect. In the wet side of elevated CO2 chambers, air warming consistently caused increases in soil respiration, whereas in other three combinations of CO2 and water treatments, warming tended to decrease soil respiration over the growing season but increase it over the winter. There were no interactive effects on soil respiration among any two or three treatment factors irrespective of testing time period. Temperature sensitivity of soil respiration was reduced by air warming, lower in the wet than the dry side, and not affected by CO2 treatment. Variations of soil respiration responses with soil temperature and soil moisture ranges could be primarily attributable to the seasonal dynamics of plant growth and its responses to the three treatments. Using a conceptual model to interpret the significant relationships of treatment-induced changes in soil respiration with changes in soil temperature and moisture observed in this study

  12. Mechanical impedance of soil crusts and water content in loamy soils

    NASA Astrophysics Data System (ADS)

    Josa March, Ramon; Verdú, Antoni M. C.; Mas, Maria Teresa

    2013-04-01

    Soil crust development affects soil water dynamics and soil aeration. Soil crusts act as mechanical barriers to fluid flow and, as their mechanical impedance increases with drying, they also become obstacles to seedling emergence. As a consequence, the emergence of seedling cohorts (sensitive seeds) might be reduced. However, this may be of interest to be used as an effective system of weed control. Soil crusting is determined by several factors: soil texture, rain intensity, sedimentation processes, etc. There are different ways to characterize the crusts. One of them is to measure their mechanical impedance (MI), which is linked to their moisture level. In this study, we measured the evolution of the mechanical impedance of crusts formed by three loamy soil types (clay loam, loam and sandy clay loam, USDA) with different soil water contents. The aim of this communication was to establish a mathematical relationship between the crust water content and its MI. A saturated soil paste was prepared and placed in PVC cylinders (50 mm diameter and 10 mm height) arranged on a plastic tray. Previously the plastic tray was sprayed with a hydrophobic liquid to prevent the adherence of samples. The samples on the plastic tray were left to air-dry under laboratory conditions until their IM was measured. To measure IM, a food texture analyzer was used. The equipment incorporates a mobile arm, a load cell to apply force and a probe. The arm moves down vertically at a constant rate and the cylindrical steel probe (4 mm diameter) penetrates the soil sample vertically at a constant rate. The equipment is provided with software to store data (time, vertical distance and force values) at a rate of up to 500 points per second. Water content in crust soil samples was determined as the loss of weight after oven-drying (105°C). From the results, an exponential regression between MI and the water content was obtained (determination coefficient very close to 1). This methodology allows

  13. Earthworm effects on movement of water and solutes in soil

    SciTech Connect

    Trojan, M.D.

    1993-01-01

    The objectives of this study were to determine and model the effects of earthworms on water and solute movement in soil. Microrelief and rainfall effects on water and solute movement were determined in packed buckets inoculated with earthworms (Aporrectodea tuberculata). A solution of Br[sup [minus

  14. Water Intake by Soil, Experiments for High School Students.

    ERIC Educational Resources Information Center

    1969

    Presented are a variety of surface run-off experiments for high school students. The experiments are analogies to basic concepts about water intake, as related to water delivery, soil properties and management, floods, and conservation measures. The materials needed to perform the experiments are easily obtainable. The experiments are followed by…

  15. NEWLY DEVELOPED TECHNOLOGIES FOR SOIL AND WATER CONSERVATION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Recent discoveries and technological innovations in the field of soil and water conservation can be traced to the works of our predecessors. In this paper, conservation is defined broadly, to include the quality of water lower in watersheds, and is discussed according to contaminants. Within-field s...

  16. Evaluation of the Interactions between Water Extractable Soil Organic Matter and Metal Cations (Cu(II), Eu(III)) Using Excitation-Emission Matrix Combined with Parallel Factor Analysis

    PubMed Central

    Wei, Jing; Han, Lu; Song, Jing; Chen, Mengfang

    2015-01-01

    The objectives of this study were to evaluate the binding behavior of Cu(II) and Eu(III) with water extractable organic matter (WEOM) in soil, and assess the competitive effect of the cations. Excitation-emission matrix (EEM) fluorescence spectrometry was used in combination with parallel factor analysis (PARAFAC) to obtain four WEOM components: fulvic-like, humic-like, microbial degraded humic-like, and protein-like substances. Fluorescence titration experiments were performed to obtain the binding parameters of PARAFAC-derived components with Cu(II) and Eu(III). The conditional complexation stability constants (logKM) of Cu(II) with the four components ranged from 5.49 to 5.94, and the Eu(III) logKM values were between 5.26 to 5.81. The component-specific binding parameters obtained from competitive binding experiments revealed that Cu(II) and Eu(III) competed for the same binding sites on the WEOM components. These results would help understand the molecular binding mechanisms of Cu(II) and Eu(III) with WEOM in soil environment. PMID:26121300

  17. Effect of Ionic Soil Stabilizers on Soil-Water Characteristic of Special Clay

    NASA Astrophysics Data System (ADS)

    Cui, D.; Xiang, W.

    2011-12-01

    The engineering properties of special clay are conventionally improved through the use of chemical additive such as ionic soil stabilizer (ISS). Such special clays are often referred to as stabilized or treated clays. The soil-water characteristic curves (SWCC) of special clays from Henan province and Hubei province were measured both in natural and stabilized conditions using the pressure plate apparatus in the suction range of 0-500 kPa. The SWCC results are used to interpret the special clays behavior due to stabilizer treatment. In addition, relationships were developed between the basic clay and stabilized properties such as specific surface area and pore size distribution. The analysis showed that specific surface area decreases, cumulative pore volume and average pore size diameter decrease, dehydration rate slows and the thickness of water film thins after treatment with Ionic Soil Stabilizer. The research data and interpretation analysis presented here can be extended to understand the water film change behaviors influencing the mechanical and physical properties of stabilized special clay soils. KEY WORDS: ionic soil stabilizer, special clay, pore size diameter, specific surface area, soil water characteristic curve, water film

  18. Gas Transport Parameters for Landfill Cover Soils: Effects of Soil Compaction and Water Blockages

    NASA Astrophysics Data System (ADS)

    Wickramarachchi, P. N.; Hamamoto, S.; Kawamoto, K.; Nawagamuwa, U.; Komatsu, T.; Moldrup, P.

    2009-12-01

    Recently, landfill sites have been emerging in greenhouse warming scenarios as a significant source of atmospheric CH4. landfill management strategies have mainly addressed the problem of preventing groundwater contamination and reduction of leachate generation. Being one of the largest source of anthropogenic CH4 emission , the final cover system should also be designed for minimizing the biogas migration into the atmosphere or the areas surrounding the landfill. Compared to the intensive research efforts on hydraulic performances of landfill final cover soil , there are few studies about gas transport characteristics of landfill cover soils. Therefore, the effects of soil physical properties such as bulk density (i.e., compaction level), soil particle size and water blockage effects on the gas exchange in t highly compacted final cover soil are largely unknown. The gas exchange through the final cover soils is controlled by advective and diffusive gas transport. Air permeability (ka) governs the advective gas transport while the soil-gas diffusion coefficient (Dp) governs diffusive gas transport . In this study, the effects of compaction level and water blockage effects on ka and Dp for two landfill final cover soils were investigated. The disturbed soil samples were taken from landfill final covers in Japan and Sri Lanka. A compaction tests were performed for the soil samples with two different size fractions (< 35 mm and < 2.0 mm). In the compaction tests at field water content , the soil samples were repacked into soil cores (i.d. 15-cm, length 12-cm) at two different compaction levels (2700 kN/m2 and 600 kN/m2). After the compaction tests, ka and Dp were measured and then samples were saturated and subsequently drained at different soil-water matric potential (pF; pF equals to log(-ɛ) where ɛ is soil-water matric potential in cm H2O) of 1.5, 2.0, 3.0, 4.1, and with air-dried (pF 6.0) and oven-dried (pF 6.9) conditions. Results showed that measured Dp values

  19. Effect of Water Content and Soil Texture on Consolidation in Unsaturated Soils

    NASA Astrophysics Data System (ADS)

    Lee, J. W.; Lo, W. C.; Yeh, C. L.

    2014-12-01

    Soil consolidation, involving time-dependent coupling between deformation of a porous medium and interstitial fluid flows within it, is of relevance to many subsurface engineering problems. In the current study, we apply the consolidation theory of poroelasticity developed by Lo et al.(2014) to investigate the effect of soil texture and initial water saturation on one-dimensional consolidation in unsaturated soils. Our model constitutes two coupled diffusion equations, where coupling occurs only in the time-derivative terms with symmetric coefficients. As simplifying to water-saturated soils, these equations exactly reduce to those in the classic Biot (1941) model of consolidation. Closed-form analytical solutions describing the excess pore air and water pressures along with the total settlement in response to external loading are obtained for both permeable and semi-permeable boundary drainage conditions by the application of the Laplace transform. Numerical calculations are then implemented for unsaturated sand, loam, silt, and clay with respect to three initial water saturations (0.7, 0.8, and 0.9) as representative examples. Our results reveal that the excess pore water pressure and total settlement are significantly sensitive to both soil texture and initial water saturation. For a given initial water saturation, the rate of dissipation of excess pore water pressure is smallest in clay, with the highest total settlement being induced, followed by silt, loam, and sand. In the early stage of consolidation, unsaturated soils bear smaller excess pore water pressure, but its dissipation is completed faster in saturated soils. Two important parameters for characterizing consolidation processes are quantitatively examined. The coefficient of consolidation for water is shown to increase with an increase in initial water saturation, taking a value in saturated soils approximately four to five orders of magnitude greater than that in unsaturated ones. The loading

  20. Mulch tillage for conserving soil water

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mulching is the practice of maintaining organic or inorganic materials on or applying them to the soil surface. It is an ancient practice, but through the years clean tillage that incorporated crop residues and also controlled weeds became the norm. Frequent and deep tillage often was promoted to co...

  1. Water Retention and Structure Stability in Smectitic or Kaolinitic Loam and Clay Soils Affected by Polyacrylamide Addition

    NASA Astrophysics Data System (ADS)

    Mamedov, Amirakh; Levy, Guy

    2015-04-01

    results suggest that determining the efficacy of different PAM applications in the field in improving water retention and soil structure is complex. Therefore soil properties (clay mineralogy, soil texture) and field conditions (moisture content) should be considered when determining the optimal rate of PAM application. The mechanisms responsible for PAM-soil interaction impacts on soil structure, stability indices and model parameters are discussed in the paper.

  2. Relating soil pore geometry to soil water content dynamics decomposed at multiple frequencies

    NASA Astrophysics Data System (ADS)

    Qin, Mingming; Gimenez, Daniel; Cooper, Miguel

    2016-04-01

    Soil structure is a critical factor determining the response of soil water content to meteorological inputs such as precipitation. Wavelet analysis can be used to filter a signal into several wavelet components, each characterizing a given frequency. The purpose of this research was to investigate relationships between the geometry of soil pore systems and the various wavelet components derived from soil water content dynamics. The two study sites investigated were located in the state of São Paulo, Brazil. Each site was comprised of five soil profiles, the first site was situated along a 300-meter transect with about 10% slope in a tropical semi-deciduous forest, while the second one spanned 230-meter over a Brazilian savanna with a slope of about 6%. For each profile, between two to four Water Content Reflectometer CS615 (Campbell Scientific, Inc.) probes were installed according to horizonation at depths varying between 0.1 m and 2.3 m. Bulk soil, three soil cores, and one undisturbed soil block were sampled from selected horizons for determining particle size distributions, water retention curves, and pore geometry, respectively. Pore shape and size were determined from binary images obtained from resin-impregnated blocks and used to characterize pore geometry. Soil water contents were recorded at a 20-minute interval over a 4-month period. The Mexican hat wavelet was used to decompose soil water content measurements into wavelet components. The responses of wavelet components to wetting and drying cycles were characterized by the median height of the peaks in each wavelet component and were correlated with particular pore shapes and sizes. For instance, large elongated and irregular pores, largely responsible for the transmission of water, were significantly correlated with wavelet components at high frequencies (40 minutes to 48 hours) while rounded pores, typically associated to water retention, were only significantly correlated to lower frequency ranges

  3. Water quality and surfactant effects on the water repellency of a sandy soil

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Differences in irrigation water quality may affect the water repellency of soils treated or untreated with surfactants. Using simulated irrigations, we evaluated water quality and surfactant application rate effects upon the water repellency of a Quincy sand (Xeric Torripsamment). We used a split ...

  4. Farm water budgets for semiarid irrigated floodplains of northern New Mexico: characterizing the surface water-groundwater interactions

    NASA Astrophysics Data System (ADS)

    Gutierrez, K. Y.; Fernald, A.; Ochoa, C. G.; Guldan, S. J.

    2013-12-01

    KEY WORDS - Hydrology, Water budget, Deep percolation, Surface water-Groundwater interactions. With the recent projections for water scarcity, water balances have become an indispensable water management tool. In irrigated floodplains, deep percolation from irrigation can represent one of the main aquifer recharge sources. A better understanding of surface water and groundwater interactions in irrigated valleys is needed for properly assessing the water balances in these systems and estimating potential aquifer recharge. We conducted a study to quantify the parameters and calculate the water budgets in three flood irrigated hay fields with relatively low, intermediate and, high water availability in northern New Mexico. We monitored different hydrologic parameters including total amount of water applied, change in soil moisture, drainage below the effective root zone, and shallow water level fluctuations in response to irrigation. Evapotranspiration was calculated from weather station data collected in-situ using the Samani-Hargreaves. Previous studies in the region have estimated deep percolation as a residual parameter of the water balance equation. In this study, we used both, the water balance method and actual measurements of deep percolation using passive lysimeters. Preliminary analyses for the three fields show a relatively rapid movement of water through the upper 50 cm of the vadose zone and a quick response of the shallow aquifer under flood irrigation. Further results from this study will provide a better understanding of surface water-groundwater interactions in flood irrigated valleys in northern New Mexico.

  5. Water-depth dependent infiltration into burnt forest soils

    NASA Astrophysics Data System (ADS)

    Langhans, Christoph; Sheridan, Gary; Noske, Phil; Metzen, Daniel; Lane, Patrick

    2014-05-01

    Infiltration into severely burnt forest soils in South Eastern Australia exhibits a behaviour that is at odds with traditional infiltration theories that assumes a coherent soil matrix, which has important implications for upscaling from plot to hillslope. Infiltration patterns were studied at three severely burnt sites with different soils by applying a blue dye solution during rainfall and runon experiments, and subsequent profile excavation. Rainfall and runon rates were varied on each plot, runoff measured, and orthogonal photos taken during quasi-steady states. From transects on these photos average inundation fractions of the surface were measured, and 1.5 mm horizontal resolution DEMs were generated with image-based software. This information was combined in a DEM inundation algorithm that calculated water depth maps for each plot and rainfall and runon rate. At all three sites, nearly 100% of infiltration occurred through macropores that bypass the matrix of a water repellent layer. Average fractions of subsoil dye staining were 3% in shallow soils with a northerly aspect and low trees, 60% in deep soils with southerly aspects and high trees, and 20% in an intermediate soil. This was consistent with runoff coefficients of 0.94 for the shallow soil, 0.08 for the deep soil, and 0.71 for the intermediate soil. Irrespective of the runoff coefficient or dyed fraction there was a positive relationship between average water depth and infiltration rates on a given plot. Functions of water depth vs. bypass infiltration were derived inversely for each plot by matching average infiltration rates with the rates derived from sampling the water depth distributions. Additionally, characteristic bypass infiltration rates for all sites as function of runon and rainfall intensity were derived, normalized by the maximum infiltration rate at full inundation. These infiltration functions represent the water depth-dependent dynamics of runoff generation in bypass infiltration

  6. Rooting Dynamics and Soil Water Variation of Native Shrubs

    NASA Astrophysics Data System (ADS)

    Kizito, A.; Dragila, M. I.; Sene, M.; Dick, R.

    2003-12-01

    Understanding the relationships that exist in the soil-plant-atmosphere continuum in semi-arid areas presents particular challenges, requiring accurate quantification of soil water with depth, a highly variable and limiting parameter in these vulnerable ecosystems. Two sites in the Peanut Basin of Senegal were selected to study rooting patterns of native shrubs and the corresponding variation of water distribution within the soil profile in both the dry and wet season. During dry periods or dry spells in the wet season, soil moisture content (θ v) surrounding the shrub's shallow roots is substantially moister than the adjacent soil matrix. It is therefore hypothesized, that nearing a condition of water stress, shrubs may participate in redistribution of soil water, effectively changing their own environment and enhancing their survival as well as that of neighboring annual crops. A possible region of water redistribution is interpreted to be between 15-75 cm depth, with the upper 0-15 cm remaining typically dry (θ v < 1 m3m-3) and forming a self mulching mechanism protecting lower horizons from the intense evaporation, and the lower 75 to 105 cm depth acting as a "moist reservoir" (θ v ˜ 6 m3m-3). We investigated shrub root depths, distribution, size, density and gravimetric soil water variation at 15 cm depth increments to 110 cm, and at 10 cm lateral spread increments to 200 cm from each shrub trunk. Shrubs exhibited a complex heterogeneous rooting system with approximately 50% of the root biomass occurring in the upper 30 cm and 95% in the upper 110 cm. Root study and soil moisture results are used to select optimal sensor placement in relation to shrub root depth and lateral spread extent. Monitoring is continuing for soil water and tension variation with sensors concentrated between 15 and 75 cm. Accurate quantitative data on the vertical and horizontal distribution of roots permits us to estimate how shrubs may alter water use by annual crops and modify

  7. Effects of Water Seal on Reducing 1,3-Dichloropropene Emissions from Different Textured Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil physical conditions can affect diffusion, environmental fate, and pest-control efficacy of fumigants in soil disinfestation treatments. Water seal (applying water using sprinklers to soil following fumigation) has shown effectiveness to reduce fumigant emissions from sandy loam soils. Soil colu...

  8. Soil water repellency: the knowledge base, advances and challenges

    NASA Astrophysics Data System (ADS)

    Doerr, S. H.

    2012-04-01

    The topic of soil water repellency (SWR or soil hydrophobicity) has moved from being perhaps a little known curiosity a few decades ago to a well established sub-discipline of soil physics and soil hydrology. In terms of the number of journal publications, SWR is comparable with other physical soil properties or processes such as crusting, aggregation or preferential flow. SWR refers to a condition when soil does not wet readily when in contact with water. This may be evident at the soil surface, when SWR leads to prolonged ponding on soils despite the presence of sufficient pore openings, or in the soil matrix, as manifest by enhanced uneven wetting and preferential flow that is not caused by structural in homogeneity. Amongst major milestones advancing the knowledge base of SWR have been the recognition that: (1) many, if not most, soils can exhibit SWR when the soil moisture content falls below a critical threshold, (2) it can be induced (and destroyed) during vegetation fires, but many soils exhibit SWR irrespective of burning, (3) it can be caused, in principle, by a large variety of naturally-abundant chemical compounds, (4) it is typically highly variable in space, time and its degree (severity and persistence), and (5) its impacts on, for example, soil hydrology, erosion and plant growth have the potential to be very substantial, but also that impacts are often minor for naturally vegetated and undisturbed soils. Amongst the key challenges that remain are: (a) predicting accurately the conditions when soils prone to SWR actually develop this property, (b) unravelling, for fire effected environments, to what degree any presence of absence of SWR is due to fire and post-fire recovery, (c) the exact nature and origin the material causing SWR at the molecular level in different environments, (d) understanding the implications of the spatial and temporal variability at different scales, (e) the capability to model and predict under which environmental conditions

  9. Collimated neutron probe for soil water content measurements

    USGS Publications Warehouse

    Klenke, J.M.; Flint, A.L.

    1991-01-01

    A collimated neutron probe was designed to enable mesurements in specific directions from the access tube. To determine the size and shape of soil volume affecting the neutron counts, experiments were conducted to evaluate: 1) the vertical distance of soil above and below the probe that influences neutron counts; 2) the horizontal distance away from the probe into the soil that influences neutron counts; 3) the angle of soil viewed by the probe from the collimator; and 4) the three-dimensional thermal-neutron density field. The vertical distance was ~0.5m, the horizontal distance was ~0.2m, and the angle of soil viewed by the probe from the collimator was ~120??. Thermal neutrons detected from distances or angles larger than these values influence the determination of relative water content by 5% or less. -from Authors

  10. Saturated hydraulic conductivity and soil water retention properties across a soil-slope transition

    NASA Astrophysics Data System (ADS)

    Mohanty, Binayak P.; Mousli, Zak

    2000-11-01

    The hydraulic properties of soil and their spatial structures are important for understanding soil moisture dynamics, land surface and subsurface hydrology, and contaminant transport. We investigated whether landscape features, including relative position on a slope, contribute to the variability of soil hydraulic properties in a complex terrain of a glacial till material. Using 396 undisturbed soil cores collected along two orthogonal transects, we measured saturated hydraulic conductivity (Ksat) and soil water retention functions at two (15 and 30 cm) depths across a glacial till landscape in central Iowa that encompassed two soil types (Nicollet loam with 1-3% slope on the hilltop position and Clarion loam with 2-5% slope on the shoulder position). The van Genuchten-Mualem model was fitted to the experimental data using the RETC optimization computer code. At the 15 cm depth a statistical comparison indicated significant differences in Ksat, saturated water content (θs), water content at permanent wilting point (θ15,000) and van Genuchten fitting parameters (α and n) between soil types and landscape positions. At the 30 cm depth, θs, θ15,000, and residual water content (θr) were found to be significantly different across the soil-slope transition. Available water content (θ333-15,000) did not show any significant difference across the soil-slope transition for either depth. No clear directional trend was observed, with some exceptions for Ksat, θs, and α on specific transect limbs and depths. Drifts in the soil hydraulic parameters due to soil-slope transition were removed using a mean-polishing approach. Geostatistical analyses of these parameters showed several important characteristics including the following: (1) The spatial correlation lengths and semivariogram patterns of the independently measured (or estimated) loge Ksat and θs at 30-cm depth matched extremely well; (2) better spatial structures with large correlation lengths were observed for

  11. Upscaled soil-water retention using van Genuchten's function

    USGS Publications Warehouse

    Green, T.R.; Constantz, J.E.; Freyberg, D.L.

    1996-01-01

    Soils are often layered at scales smaller than the block size used in numerical and conceptual models of variably saturated flow. Consequently, the small-scale variability in water content within each block must be homogenized (upscaled). Laboratory results have shown that a linear volume average (LVA) of water content at a uniform suction is a good approximation to measured water contents in heterogeneous cores. Here, we upscale water contents using van Genuchten's function for both the local and upscaled soil-water-retention characteristics. The van Genuchten (vG) function compares favorably with LVA results, laboratory experiments under hydrostatic conditions in 3-cm cores, and numerical simulations of large-scale gravity drainage. Our method yields upscaled vG parameter values by fitting the vG curve to the LVA of water contents at various suction values. In practice, it is more efficient to compute direct averages of the local vG parameter values. Nonlinear power averages quantify a feasible range of values for each upscaled vG shape parameter; upscaled values of N are consistently less than the harmonic means, reflecting broad pore-size distributions of the upscaled soils. The vG function is useful for modeling soil-water retention at large scales, and these results provide guidance for its application.

  12. Modelling of cutting tool - soil interaction - part I: contact behaviour

    NASA Astrophysics Data System (ADS)

    Nardin, A.; Zavarise, G.; Schrefler, B. A.

    The unknown interaction of the cutting tools with geological settings represents an interesting problem for the excavation machinery industry. To simplify the non-linear aspects involved in the numerical analysis of such phenomena a strategy for an accurate soil modelling has to be defined. A possible approach is the discrete one, by considering the soil as an assembly of rigid spheres. In this work this strategy is adopted. The basic idea is to concentrate at the contact level between the spheres the real mechanical behaviour of the soil. For this purpose suitable contact models have been developed, where specific elasto-plastic laws have been implemented in the node-to-segment contact formulation. The framework for the plastic behaviour consists of a failure criterion, a one-dimensional, rate-independent elasto-plastic flow rule for the normal and the tangential force and a non-linear yield criterion. The final aim of this paper is to develop mechanical models to study the behaviour of stiff soils and rocks under different loading conditions.

  13. Effect of Plant-derived Hydrophobic Compounds on Soil Water Repellency in Dutch Sandy Soils

    NASA Astrophysics Data System (ADS)

    Mao, Jiefei; Dekker, Stefan C.; Nierop, Klaas G. J.

    2013-04-01

    Soil water repellency or hydrophobicity is a common and important soil property, which may diminish plant growth and promotes soil erosion leading to environmentally undesired situations. Hydrophobic organic compounds in the soil are derived from vegetation (leaves, roots, mosses) or microorganisms (fungi, bacteria), and these compounds induce soil water repellency (SWR) and can be called SWR-biomarkers. As common hydrophobic constituents of organic matter, plant lipids are mainly from wax layers of leaves and roots, whereas cutins and suberins as aliphatic biopolyesters occur in leaves and roots, respectively. Their unique compositions in soil can indicate the original vegetation sources. To investigate the individual or combined effects of the hydrophobic compounds on SWR and their possible associations with each other, we conducted experiments to analyse the organic composition of Dutch coastal dune sandy soils in relation to SWR. DCM/MeOH solvent is used to remove solvent soluble lipids. BF3-methanol is utilized to depolymerize cutins and suberins from isopropanol/NH3 extractable organic matter. Total organic carbon (TOC) has a positive linear relation with SWR only for those soils containing low TOC (

  14. Soil-Water Characteristic Curves of Red Clay treated by Ionic Soil Stabilizer

    NASA Astrophysics Data System (ADS)

    Cui, D.; Xiang, W.

    2009-12-01

    The relationship of red clay particle with water is an important factor to produce geological disaster and environmental damage. In order to reduce the role of adsorbed water of red clay in WuHan, Ionic Soil Stabilizer (ISS) was used to treat the red clay. Soil Moisture Equipment made in U.S.A was used to measure soil-water characteristic curve of red clay both in natural and stabilized conditions in the suction range of 0-500kPa. The SWCC results were used to interpret the red clay behavior due to stabilizer treatment. In addition, relationship were compared between the basic soil and stabilizer properties such as water content, dry density, liquid limit, plastic limit, moisture absorption rate and stabilizer dosages. The analysis showed that the particle density and specific surface area increase, the dehydration rate slows and the thickness of water film thins after treatment with Ionic Soil Stabilizer. After treatment with the ISS, the geological disasters caused by the adsorbed water of red clay can be effectively inhibited.

  15. Evaluation of Two Soil Water Redistribution Models (Finite Difference and Hourly Cascade Approach) Through The Comparison of Continuous field Sensor-Based Measurements

    NASA Astrophysics Data System (ADS)

    Ferreyra, R.; Stockle, C. O.; Huggins, D. R.

    2014-12-01

    Soil water storage and dynamics are of critical importance for a variety of processes in terrestrial ecosystems, including agriculture. Many of those systems are under significant pressure in terms of water availability and use. Therefore, assessing alternative scenarios through hydrological models is an increasingly valuable exercise. Soil water holding capacity is defined by the concepts of soil field capacity and plant available water, which are directly related to soil physical properties. Both concepts define the energy status of water in the root system and closely interact with plant physiological processes. Furthermore, these concepts play a key role in the environmental transport of nutrients and pollutants. Soil physical parameters (e.g. saturated hydraulic conductivity, total porosity and water release curve) are required as input for field-scale soil water redistribution models. These parameters are normally not easy to measure or monitor, and estimation through pedotransfer functions is often inadequate. Our objectives are to improve field-scale hydrological modeling by: (1) assessing new undisturbed methodologies for determining important soil physical parameters necessary for model inputs; and (2) evaluating model outputs, making a detailed specification of soil parameters and the particular boundary condition that are driving water movement under two contrasting environments. Soil physical properties (saturated hydraulic conductivity and determination of water release curves) were quantified using undisturbed laboratory methodologies for two different soil textural classes (silt loam and sandy loam) and used to evaluate two soil water redistribution models (finite difference solution and hourly cascade approach). We will report on model corroboration results performed using in situ, continuous, field measurements with soil water content capacitance probes and digital tensiometers. Here, natural drainage and water redistribution were monitored

  16. High Resolution Soil Water from Regional Databases and Satellite Images

    NASA Technical Reports Server (NTRS)

    Morris, Robin D.; Smelyanskly, Vadim N.; Coughlin, Joseph; Dungan, Jennifer; Clancy, Daniel (Technical Monitor)

    2002-01-01

    This viewgraph presentation provides information on the ways in which plant growth can be inferred from satellite data and can then be used to infer soil water. There are several steps in this process, the first of which is the acquisition of data from satellite observations and relevant information databases such as the State Soil Geographic Database (STATSGO). Then probabilistic analysis and inversion with the Bayes' theorem reveals sources of uncertainty. The Markov chain Monte Carlo method is also used.

  17. STRAFI-NMR studies of water transport in soil.

    PubMed

    Preston, A R; Bird, N R; Kinchesh, P; Randall, E W; Whalley, W R

    2001-01-01

    1-D STRAFI (STRAy FIeld) imaging is used to study water distribution in a sandy loam. The matric potential of the soil can be varied during acquisition of 1-D profiles. Results at a range of potentials are presented showing both the equilibrium distribution and the evolution of the profile following an abrupt change in matric potential. The air breakthrough point and variations in draining behaviour due to differences in soil compaction are identified. PMID:11445357

  18. Interactions in Natural Colloid Systems "Biosolids" - Soil and Plant

    NASA Astrophysics Data System (ADS)

    Kalinichenko, Kira V.; Nikovskaya, Galina N.; Ulberg, Zoya R.

    2016-04-01

    The "biosolids" are complex biocolloid system arising in huge amounts (mln tons per year) from biological municipal wastewater treatment. These contain clusters of nanoparticles of heavy metal compounds (in slightly soluble or unsoluble forms, such as phosphates, sulphates, carbonates, hydroxides, and etc.), cells, humic substances and so on, involved in exopolysaccharides (EPS) net matrix. One may consider that biosolids are the natural nanocomposite. Due to the presence of nitrogen, phosphorus, potassium and other macro- and microelements (heavy metals), vitamins, aminoacids, etc., the biosolids are a depot of bioelements for plant nutrition. Thus, it is generally recognized that most rationally to utilize them for land application. For this purpose the biocolloid process was developed in biosolids system by initiation of microbial vital ability followed by the synthesis of EPS, propagation of ecologically important microorganisms, loosening of the structure and weakening of the coagulation contacts between biosolids colloids, but the structure integrity maintaining [1,2]. It was demonstrated that the applying of biosolids with metabolizing microorganisms to soil provided the improving soil structure, namely the increasing of waterstable aggregates content (70% vs. 20%). It occurs due to flocculation ability of biosolids EPS. The experimental modelling of mutual interactions in systems of soils - biosolids (with metabolizing microorganisms) were realized and their colloid and chemical mechanisms were formulated [3]. As it is known, the most harmonious plant growth comes at a prolonged entering of nutrients under the action of plant roots exudates which include pool of organic acids and polysaccharides [4]. Special investigations showed that under the influence of exudates excreted by growing plants, the biosolids microelements can release gradually from immobilized state into environment and are able to absorb by plants. Thus, the biosolids can serve as an active

  19. Association of water spectral indices with plant and soil water relations in contrasting wheat genotypes

    PubMed Central

    Gutierrez, Mario; Reynolds, Matthew P.; Klatt, Arthur R.

    2010-01-01

    Spectral reflectance indices can be used to estimate the water status of plants in a rapid, non-destructive manner. Water spectral indices were measured on wheat under a range of water-deficit conditions in field-based yield trials to establish their relationship with water relations parameters as well as available volumetric soil water (AVSW) to indicate soil water extraction patterns. Three types of wheat germplasm were studied which showed a range of drought adaptation; near-isomorphic sister lines from an elite/elite cross, advanced breeding lines, and lines derived from interspecific hybridization with wild relatives (synthetic derivative lines). Five water spectral indices (one water index and four normalized water indices) based on near infrared wavelengths were determined under field conditions between the booting and grain-filling stages of crop development. Among all water spectral indices, one in particular, which was denominated as NWI-3, showed the most consistent associations with water relations parameters and demonstrated the strongest associations in all three germplasm sets. NWI-3 showed a strong linear relationship (r2 >0.6–0.8) with leaf water potential (ψleaf) across a broad range of values (–2.0 to –4.0 MPa) that were determined by natural variation in the environment associated with intra- and inter-seasonal affects. Association observed between NWI-3 and canopy temperature (CT) was consistent with the idea that genotypes with a better hydration status have a larger water flux (increased stomatal conductance) during the day. NWI-3 was also related to soil water potential (ψsoil) and AVSW, indicating that drought-adapted lines could extract more water from deeper soil profiles to maintain favourable water relations. NWI-3 was sufficiently sensitive to detect genotypic differences (indicated by phenotypic and genetic correlations) in water status at the canopy and soil levels indicating its potential application in precision phenotyping

  20. Modelling of dynamic soil-structure-ice interaction

    NASA Astrophysics Data System (ADS)

    Karna, Tuomo

    A computer model was developed for evaluating the dynamic ice-structure interaction. The effects of soil structure interaction are included in the model. The program can be used in the analysis of events, where an offshore structure is subjected to the action of drifting ice sheets or massive ice features like an iceberg. The new approach is based on a generalized modeling of the ice crushing process which takes into account the dependence of ice load on relative displacement and relative velocity between the ice edge and the structure. A substructure technique, where separate equations are set up for each of the interacting medium, is considered. A zonal approach is applied while modeling the ice failure processes. The effects of nonsimultaneous crushing are considered.

  1. Wildfire Ash: Chemical Composition, Ash-Soil Interactions and Environmental Impacts

    NASA Astrophysics Data System (ADS)

    Brook, Anna; Hamzi, Seham; Wittenberg, Lea

    2015-04-01

    Of the five classical factors of soil formation, climate, parent material, topography, time, organisms, and recently recognized human activity, it is the latter factor which discretely includes fire and post-burn impact. However, it is considered that soil undergoing fire just experience a temporary removal of the top organic horizon, thus slightly modified and often labeled as 'temporarily disturbed' soil or soil 'under restoration/rehabilitation'. In fact the suggested seventh factor, post-burned produced ash, can act both dependently and independently of the other soil forming factors (Levin et al., 2013; Certini 2013). They are interdependent in cases where ash influences occur on time scales similar to 'natural' soil formation (Keesstra et ai., 2014) such as changes in vegetation. On the other hand, in post-fire areas a strong dependency is expected between soil-water retention mechanism, climate and topography. Wild-land fires exert many changes on the physical, chemical, mineralogical, biological, and morphological properties of soil that, in turn, affect the soil's hydrology and nutrient flux, modifying its ability to support vegetation and resist erosion. The ash produced by forest fires is a complex mixture composed of organic and inorganic particles characterized by vary physical-chemical and morphological properties. The importance of this study is straightforwardly related to the frequency and large-scales wildfires in Mediterranean region. In fact, wildfires are major environmental and land management concern in the world, where the number and severity of wildfires has increased during the past decades (Bodi, 2013). Certini (2013) assumed that cumulatively all of the vegetated land is burned in about 31 years annually affecting 330-430 Mha (over 3% of the Earth's surface) and wide range of land cover types worldwide including forests, peatlands, shrublands and grasslands. Whereas, the fire is identified as an important factor in soil formation, the

  2. Reflectance of vegetation, soil, and water

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L. (Principal Investigator); Gausman, H. W.; Leamer, R. W.; Richardson, A. J.; Gerbermann, A. H.; Torline, R. J.; Gautreaux, M. R.; Everitt, J. H.; Guellar, J. A.; Rodriguez, R. R.

    1974-01-01

    The author has identified the following significant results. Bands 4, 5, and 7 and 5, 6, and 7 were best for distinguishing among crop and soil categories in ERTS-1 SCENES 1182-16322 (1-21-73) and 1308-16323 (5-21-73) respectively. Chlorotic sorghum areas 2.8 acres or larger in size were identified on a computer printout of band 5 data. Reflectance of crop residues was more often different from bare soil in band 4 than in bands 5, 6, and 7. Simultaneously acquired aircraft and spacecraft MSS data indicated that spacecraft surveys are as reliable as aircraft surveys. ERTS-1 data were successfully used to estimate acreage of citrus, cotton, and sorghum as well as idle crop land.

  3. Soil water sensors:Problems, advances and potential for irrigation scheduling

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Irrigation water management has to do with the appropriate application of water to soils, in terms of amounts, rates, and timing to satisfy crop water demands, while protecting the soil and water resources from degradation. In this regard, sensors can be used to monitor the soil water status; and so...

  4. Observing plants dealing with soil water stress: Daily soil moisture fluctuations derived from polymer tensiometers

    NASA Astrophysics Data System (ADS)

    van der Ploeg, Martine; de Rooij, Gerrit

    2014-05-01

    Periods of soil water deficit often occur within a plant's life cycle, even in temperate deciduous and rain forests (Wilson et al. 2001, Grace 1999). Various experiments have shown that roots are able to sense the distribution of water in the soil, and produce signals that trigger changes in leaf expansion rate and stomatal conductance (Blackman and Davies 1985, Gollan et al. 1986, Gowing et al. 1990 Davies and Zhang 1991, Mansfield and De Silva 1994, Sadras and Milroy 1996). Partitioning of water and air in the soil, solute distribution in soil water, water flow through the soil, and water availability for plants can be determined according to the distribution of the soil water potential (e.g. Schröder et al. 2013, Kool et al. 2014). Understanding plant water uptake under dry conditions has been compromised by hydrological instrumentation with low accuracy in dry soils due to signal attenuation, or a compromised measurement range (Whalley et al. 2013). Development of polymer tensiometers makes it possible to study the soil water potential over a range meaningful for studying plant responses to water stress (Bakker et al. 2007, Van der Ploeg et al. 2008, 2010). Polymer tensiometer data obtained from a lysimeter experiment (Van der Ploeg et al. 2008) were used to analyse day-night fluctuations of soil moisture in the vicinity of maize roots. To do so, three polymer tensiometers placed in the middle of the lysimeter from a control, dry and very dry treatment (one lysimeter per treatment) were used to calculate water content changes over 12 hours. These 12 hours corresponded with the operation of the growing light. Soil water potential measurements in the hour before the growing light was turned on or off were averaged. The averaged value was used as input for the van Genuchten (1980) model. Parameters for the model were obtained from laboratory determination of water retention, with a separate model parameterization for each lysimeter setup. Results show daily

  5. Effect of the soil water content on Jatropha seedlings in a tropical climate

    NASA Astrophysics Data System (ADS)

    Pérez-Vázquez, A.; Hernández-Salinas, G.; Ávila-Reséndiz, C.; Valdés-Rodríguez, O. A.; Gallardo-López, F.; García-Pérez, E.; Ruiz-Rosado, O.

    2013-09-01

    The purpose of this study was to evaluate growth, chlorophyll content, and photosynthesis in Jatropha at different levels of soil moisture. Plants were cultivated in containers and the treatments of the soil water content evaluated were: 0% (without watering), 20, 40, 60, and 80% soil water content. Plant height was statistically similar for all treatments, but the number of leaves differed significantly. Total dry matter and chlorophyll at 40, 60, and 80% soil water content were statistically similar, but different from 0 and 20% soil water content. Leaf area at 40, 60, and 80% soil water content was statistically different from 0 and 20% soil water content. The photosynthetic rate, transpiration and stomatal conductance at 60 and 80% soil water content were statistically similar but different from 0 and 20% soil water content. Water stress affected growth, chlorophyll content, photosynthetic rate, transpiration, and stomatal conductance.

  6. Invariant soil water potential at zero microbial respiration explained by hydrological discontinuity in dry soils

    NASA Astrophysics Data System (ADS)

    Manzoni, S.; Katul, G.

    2014-10-01

    Soil microbial respiration rates decrease with soil drying, ceasing below water potentials around -15 MPa. A proposed mechanism for this pattern is that under dry conditions, microbes are substrate limited because solute diffusivity is halted due to breaking of water film continuity. However, pore connectivity estimated from hydraulic conductivity and solute diffusivity (at Darcy's scale) is typically interrupted at much less negative water potentials than microbial respiration (-0.1 to -1 MPa). It is hypothesized here that the more negative respiration thresholds than at the Darcy's scale emerge because microbial activity is restricted to microscale soil patches that retain some hydrological connectivity even when it is lost at the macroscale. This hypothesis is explored using results from percolation theory and meta-analyses of respiration-water potential curves and hydrological percolation points. When reducing the spatial scale from macroscale to microscale, hydrological and respiration thresholds become consistent, supporting the proposed hypothesis.

  7. Zinc movement in sewage-sludge-treated soils as influenced by soil properties, irrigation water quality, and soil moisture level

    USGS Publications Warehouse

    Welch, J.E.; Lund, L.J.

    1989-01-01

    A soil column study was conducted to assess the movement of Zn in sewage-sludge-amended soils. Varables investigated were soil properties, irrigation water quality, and soil moisture level. Bulk samples of the surface layer of six soil series were packed into columns, 10.2 cm in diameter and 110 cm in length. An anaerobically digested municipal sewage sludge was incorporated into the top 20 cm of each column at a rate of 300 mg ha-1. The columns were maintained at moisture levels of saturation and unsaturation and were leached with two waters of different quality. At the termination of leaching, the columns were cut open and the soil was sectioned and analyzed. Zinc movement was evaluated by mass balance accounting and correlation and regression analysis. Zinc movement in the unsaturated columns ranged from 3 to 30 cm, with a mean of 10 cm. The difference in irrigation water quality did not have an effect on Zn movement. Most of the Zn applied to the unsaturated columns remained in the sludge-amended soil layer (96.1 to 99.6%, with a mean of 98.1%). The major portion of Zn leached from the sludge-amended soil layer accumulated in the 0- to 3-cm depth (35.7 to 100%, with a mean of 73.6%). The mean final soil pH values decreased in the order: saturated columns = sludge-amended soil layer > untreated soils > unsaturated columns. Total Zn leached from the sludge-amended soil layer was correlated negatively at P = 0.001 with final pH (r = -0.85). Depth of Zn movement was correlated negatively at P = 0.001 with final pH (r = -0.91). Multiple linear regression analysis showed that the final pH accounted for 72% of the variation in the total amounts of Zn leached from the sludge-amended soil layer of the unsaturated columns and accounted for 82% of the variation in the depth of Zn movement among the unsaturated columns. A significant correlation was not found between Zn and organic carbon in soil solutions, but a negative correlation significant at P = 0.001 was found

  8. Interactions between carbon and water vapor fluxes in Panama

    NASA Astrophysics Data System (ADS)

    Wolf, S.; Buchmann, N.; Eugster, W.

    2009-04-01

    Tropical ecosystems are particularly sensitive to changes in environmental conditions and have a significant impact on the global climate due to biophysical and biogeochemical feedbacks. It is still unclear how precipitation variability and soil moisture will develop under future climatic conditions, with large implications on ecosystems in the tropics. Thus, an improved understanding of the interactions between carbon and water vapor fluxes in the tropics is needed. However, continuous measurements of these fluxes in tropical regions are sparse in general and only few localities exist in Central America. Our two eddy flux towers were established in Sardinilla, Central Panama (9.3° N, 79.6° W, 70 m a.s.l.) to measure carbon and water vapor fluxes continuously over an afforestation with native tree species and an adjacent, traditionally grazed pasture. Our objective is to understand the variability of carbon and water vapor fluxes, their environmental drivers and their interaction in these two ecosystems. First results from nearly two years of continuous operation will be presented and discussed, focusing particularly on seasonal transition periods and the effects of a prolonged dry season caused by a strong ENSO event (La Niña) in 2008.

  9. The Soil Stack: An Interactive Computer Program Describing Basic Soil Science and Soil Degradation.

    ERIC Educational Resources Information Center

    Cattle, S. R.; And Others

    1995-01-01

    A computer program dealing with numerous aspects of soil degradation has a target audience of high school and university students (16-20 year olds), and is presented in a series of cards grouped together as stacks. Describes use of the software in Australia. (LZ)

  10. Analysis of water application efficiency and emission uniformity of drip irrigation systems based on space-time analysis of soil moisture patterns in soils

    NASA Astrophysics Data System (ADS)

    Shabeeb, Ahmeed; Taha, Uday; dragonetti, giovanna; Lamaddalena, Nicola; Coppola, Antonio

    2016-04-01

    In order to evaluate how efficiently and uniformly drip irrigation systems can deliver water to emitters distributed around a field, we need some methods for measuring/calculating water application efficiency (WAE) and emission uniformity (EU). In general, the calculation of the WAE and of other efficiency indices requires the measurement of the water stored in the root zone. Measuring water storage in soils allows directly saying how much water a given location of the field retains having received a given amount of irrigation water. And yet, due to the difficulties of measuring water content variability under an irrigation system at field scale, it is quite common using EU as a proxy indicator of the irrigation performance. This implicitly means assuming that the uniformity of water application is immediately reflected in an uniformity of water stored in the root zone. In other words, that if a site receive more water it will store more water. Nevertheless, due to the heterogeneity of soil hydrological properties the same EU may correspond to very different distributions of water stored in the soil root zone. 1) In the case of isolated drippers, the storages measured in the soil root zone layer shortly after an irrigation event may be or not different from the water height applied at the surface depending on the vertical/horizontal development of the wetted bulbs. Specifically, in the case of dominant horizontal spreading the water storage is expected to reflect the distribution of water applied at the surface. To the contrary, in the case of relatively significant vertical spreading, deep percolation fluxes (fluxes leaving the root zone) may well induce water storages in the root zone significantly different from the water applied at the surface. 2) The drippers and laterals are close enough that the wetted bulbs below adjacent drippers may interact. In this case, lateral fluxes in the soil may well induce water storages in the root zone which may be

  11. Temporal and soil management effects on soil infiltration and water content in a hillslope vineyard

    NASA Astrophysics Data System (ADS)

    Biddoccu, Marcella; Ferraris, Stefano; Cavallo, Eugenio

    2015-04-01

    The maintenance of bare soil in the vineyard's inter-rows with tillage, as well as other mechanized operations which increase the vehicle traffic, expose the soil to degradation, favoring overland flow and further threats as compaction, reduction of soil water holding capacity and water infiltration. Water infiltration is strongly controlled by field-saturated hydraulic conductivity, which depends primarily on soil texture and structure, and it is characterized by high spatial and temporal variability. Beyond the currently adopted soil management, some major causes in variability of infiltration rates are the history of cultivation and the structure of the first centimeters of the vineyard's soil. A study was carried out in two experimental vineyard plots included in the 'Tenuta Cannona Experimental Vine and Wine Centre of Regione Piemonte', located in NW Italy. The study was addressed to evaluate the temporal variations of the field-saturated hydraulic conductivity, in relation to the soil management adopted in the inter-rows of a hillslope vineyard. The investigation was carried out in a vineyard comparing the adoption of two different soil managements in the inter-rows: 1) conventional tillage and 2) controlled grass cover. Several series of double-ring of infiltration tests were carried out during a 2-years period of observation, using the simplified falling head technique (SFH). In order to take into account the effect of tractor traffic, the tests were done both inside the the track, the portion of soil affected by the transit of tractor wheels or tracks, and outside the track. Before the execution of each test, bulk density and initial soil water content close to the investigated area were determined. Relations among infiltration behavior and these parameters were analyzed. Field-saturated hydraulic conductivity (Kfs) at different sampling dates showed high variability, especially in the vineyard with cultivated soil. Indeed, highest infiltration rates were

  12. Impact of reclaimed water irrigation on soil health in urban green areas.

    PubMed

    Chen, Weiping; Lu, Sidan; Pan, Neng; Wang, Yanchun; Wu, Laosheng

    2015-01-01

    Rapid increase of reclaimed water irrigation in urban green areas requires investigating its impact on soil health conditions. In this research, field study was conducted in 7 parks in Beijing with different histories of reclaimed water irrigation. Twenty soil attributes were analyzed to evaluate the effects of reclaimed water irrigation on the soil health conditions. Results showed that soil nutrient conditions were ameliorated by reclaimed water irrigation, as indicated by the increase of soil organic matter content (SOM), total nitrogen (TN), and available phosphorus (AP). No soil salinization but a slight soil alkalization was observed under reclaimed water irrigation. Accumulation of heavy metals in soil was insignificant. It was also observed that reclaimed water irrigation could significantly improve the soil microorganism activities. Overall, the soil health conditions were improved with reclaimed water irrigation, and the improvement increased when the reclaimed water irrigation period became longer. PMID:25150469

  13. Energy and water additions give rise to simple responses in plant canopy and soil microclimates of a high arctic ecosystem

    NASA Astrophysics Data System (ADS)

    Sullivan, Patrick F.; Welker, Jeffrey M.; Steltzer, Heidi; Sletten, Ronald S.; Hagedorn, Birgit; Arens, Seth J. T.; Horwath, Jennifer L.

    2008-09-01

    Energy and water inputs were increased during the snow-free season to test the sensitivity of a cold, dry ecosystem to climate change. Infrared radiators were used to provide two levels of supplemental radiation (T1 and T2) to prostrate dwarf-shrub, herb tundra in northwest Greenland. The higher radiation addition was combined with supplemental water in a factorial design. Radiation additions increased midday canopy temperatures by up to 4.0°C and 6.0°C and growing season mean shallow soil temperatures by 1.3°C and 2.4°C in T1 and T2 plots, respectively. Soil warming was measured at and probably exceeded 10 cm in depth. There was no evidence of soil drying in plots that received additional radiation, in contrast with other studies, nor was there evidence that supplemental water interacted with radiation additions to affect soil temperatures. Water additions were generally undetectable against a background of large seasonal changes in soil water content. We suggest that well-drained soils and strong seasonal controls on soil water contents (e.g., soil thaw and evapotranspiration) limit the system's sensitivity to changes in precipitation during the brief growing season. In general, multifactor changes in climate gave rise to simple changes in the vegetation microclimate of this cold, dry ecosystem.

  14. Stemflow-induced processes of soil water storage

    NASA Astrophysics Data System (ADS)

    Germer, Sonja

    2013-04-01

    Compared to stemflow production studies only few studies deal with the fate of stemflow at the near-stem soil. To investigate stemflow contribution to the root zone soil moisture by young and adult babassu palms (Attalea speciosa Mart.), I studied stemflow generation, subsequent soil water percolation and root distributions. Rainfall, stemflow and perched water tables were monitored on an event basis. Perched water tables were monitored next to adult palms at two depths and three stem distances. Dye tracer experiments monitored stemflow-induced preferential flow paths. Root distributions of fine and coarse roots were related to soil water redistribution. Average rainfall-collecting area per adult palm was 6.4 m², but variability between them was high. Funneling ratios ranged between 16-71 and 4-55 for adult and young palms, respectively. Nonetheless, even very small rainfall events of 1 mm can generate stemflow. On average, 9 liters of adult palm stemflow were intercepted and stemflow tended to decrease for-high intensity rainfall events. Young babassu palms funneled rainfall via their fronds, directly to their subterranean stems. The funneling of rainfall towards adult palm stems, in contrast, led to great stemflow fluxes down to the soil and induced initial horizontal water flows through the soil, leading to perched water tables next to palms, even after small rainfall events. The perched water tables extended, however, only a few decimeters from palm stems. After perched water tables became established, vertical percolation through the soil dominated. To my knowledge, this process has not been described before, and it can be seen as an addition to the two previously described stemflow-induced processes of Horton overland flow and fast, deep percolation along roots. This study has demonstrated that Babassu palms funnel water to their stems and subsequently store it in the soil next to their stems in areas where coarse root length density is very high. This might

  15. Complexation of silver and dissolved organic matter in soil water extracts.

    PubMed

    Settimio, Lara; McLaughlin, Mike J; Kirby, Jason K; Langdon, Kate A; Janik, Les; Smith, Scott

    2015-04-01

    An important aspect of the behaviour and fate of silver (Ag) in soils is the interaction with dissolved organic matter (DOM). The complexation and strength of binding of Ag(+) with DOM in soil water extracts was examined and modelled based on a range of chemical and quality DOM measurements. Silver ion binding measured by addition of the (110m)Ag radioisotope in addition to a cation exchange resin technique were used to determine strongly complexed Ag in solutions. Silver was found to be up to 70% strongly complexed. The variability in Ag(+) binding by DOM across different soils was closely related (R(2) = 0.8) to the mid-infrared spectra of these extracts. The affinity of Ag(+) for DOM was stronger in solutions containing a greater content of humic and aromatic structures. The ability of Ag(+) to complex with DOM could result in increased mobilisation of this metal in the soil environment. PMID:25660071

  16. Modeling plant competition for soil water balance in Water-limited Mediterranean Ecosystems

    NASA Astrophysics Data System (ADS)

    Cortis, C.; Montaldo, N.

    2009-12-01

    In heterogeneous ecosystems, such Mediterranean ecosystems, contrasting plant functional types (PFTs, e.g., grass and woody vegetation) compete for the water use. In these complex ecosystems current modeling approaches need to be improved due to a general lack of knowledge about the relationship between ET and the plant survival strategies for the different PFTs under water stress. Indeed, still unsolved questions are: how the PFTs (in particular the root systems) compete for the water use, the impact of this competition on the water balance terms, and the role of the soil type and soil depth in this competition. For this reasons an elaborated coupled Vegetation dynamic model (VDM) - land surface model (LSM) model able to also predict root distribution of competing plant systems is developed. The transport of vertical water flow in the unsaturated soil is modelled through a Richards’ equation based model. The water extraction (sink) term is considered as the root water uptake. Two VDMs predict vegetation dynamics, including spatial and temporal distribution/evolution of the root systems in the soil of two competing species (grass and woody vegetation). An innovative method for solving the unlinear system of predicting equations is proposed. The coupled model is able to predict soil and root water potential of the two competing plant species. The model is tested for the Orroli case study, situated in the mid-west of Sardinia within the Flumendosa river watershed. The site landscape is a mixture of Mediterranean patchy vegetation types: trees, including wild olives and coark oaks, different shrubs and herbaceous species. In particular two contrasting plant functional types (grass and woody vegetation) have been included. The model well predict the soil moisture and vegetation dynamics for the case study, and significantly different root potentials are predicted for the two PFTs, highlighting the root competition for the water use. The soil depth is low in the case

  17. Pore-Scale Effects of Soil Structure And Microbial EPS Production On Soil Water Retention

    NASA Astrophysics Data System (ADS)

    Orner, E.; Anderson, E.; Rubinstein, R. L.; Chau, J. F.; Shor, L. M.; Gage, D. J.

    2013-12-01

    Climate-induced changes to the hydrological cycle will increase the frequency of extreme weather events including powerful storms and prolonged droughts. Moving forward, one of the major factors limiting primary productivity in terrestrial ecosystems will be sub-optimal soil moisture. We focus here on the ability of soils to retain moisture under drying conditions. A soil's ability to retain moisture is influenced by many factors including its texture, its structure, and the activities of soil microbes. In soil microcosms, the addition of small amounts of microbially-produced extracellular polymeric substances (EPS) can dramatically shift moisture retention curves. The objective of this research is to better understand how soil structure and EPS may act together to retain moisture in unsaturated soils. Replicate micromodels with exactly-conserved 2-D physical geometry were initially filled with aqueous suspensions of one of two types of bacteria: one mutant was ultra- muccoid and the other was non-muccoid. Replicate micromodels were held at a fixed, external, relative humidity, and the position of the air-water interface was imaged over time as water evaporates. There was no forced convection of air or water inside the micromodels: drying was achieved by water evaporation and diffusion alone. We used a fully automated, inverted microscope to image replicate drying lanes each with dimensions of 1 mm x 10 mm. A complete set of images was collected every 30 minutes for 30 hours. The results show devices loaded with the highly muccoid strain remained >40% hydrated for 13 h, while devices loaded with the non-muccoid remained >40% hydrated for only 6 h, and were completely dry by 13 h. Current work is comparing interfacial water fluxes in structured and unstructured settings, and is attempting to model the synergistic effects of soil structure and EPS content on moisture retention in real soils. This research may allow more accurate description of naturally

  18. Modelling Soil Water Characteristic Curves for the Investigation of Hydrophobicity

    NASA Astrophysics Data System (ADS)

    Hallin, Ingrid; Matthews, Peter; Laudone, Maurizio; Van Keulen, Geertje; Doerr, Stefan; Francis, Lewis; Dudley, Ed; Gazze, Andrea; Quinn, Gerry; Whalley, Richard; Ashton, Rhys

    2016-04-01

    Soil hydrophobicity presents a major challenge for the future, as it reduces both plant-available water and irrigation efficiency, and can increase flooding hazards and erosion. A collaborative research project has been set up in the UK to study hydrophobicity over a wide range of length scales. At core scale, we are investigating the wetting behaviour of water repellent soils in order to model percolation through hydrophobic pore spaces. To that end, water retention measurements were carried out on both wettable and forcibly-wetted water-repellent soils collected from three locations in England and Wales. The data were then fitted with both the commonly used Van Genuchten model and an alternative model from PoreXpert, a software program that analyses and models porous materials. The Van Genuchten model fits a curve to the data using parameters related to air entry suction, irreducible water content and pore size distribution. By contrast, PoreXpert uses a Boltzmann-annealed simplex to find a best-fit curve based on parameters directly related to the void structure of the soil: the size of the voids, the shape of the void size distribution, and how the voids are connected to each other. Both Van Genuchten and PoreXpert fit the experimental data well, but where Van Genuchten forces an S-shaped curve that can mask small variations, PoreXpert gives a closer fit of no pre-defined shape that captures subtle differences between data points. This allows us to calculate differences in the effective pore and throat size distributions, and provides a mechanistic framework from which to model additional hydrologic behaviour in water repellent soil. Simulations of capillary induced wetting based on these mechanistic postulates are then compared to wicking experiments at the core scale, which can then be upscaled and applied to other soils.

  19. Mediterranean shrub vegetation: soil protection vs. water availability

    NASA Astrophysics Data System (ADS)

    García Estringana, Pablo; Nieves Alonso-Blázquez, M.; Alegre, Alegre; Cerdà, Artemi

    2014-05-01

    Soil Erosion and Land Degradation are closely related to the changes in the vegetation cover (Zhao et al., 2013). Although other factors such as rainfall intensiy or slope (Ziadat and Taimeh, 2013) the plant covers is the main factor that controls the soil erosion (Haregeweyn, 2013). Plant cover is the main factor of soil erosion processes as the vegetation control the infiltration and runoff generation (Cerdà, 1998a; Kargar Chigani et al., 2012). Vegetation cover acts in a complex way in influencing on the one hand on runoff and soil loss and on the other hand on the amount and the way that rainfall reaches the soil surface. In arid and semiarid regions, where erosion is one of the main degradation processes and water is a scant resource, a minimum percentage of vegetation coverage is necessary to protect the soil from erosion, but without compromising the availability of water (Belmonte Serrato and Romero Diaz, 1998). This is mainly controlled by the vegetation distribution (Cerdà, 1997a; Cammeraat et al., 2010; Kakembo et al., 2012). Land abandonment is common in Mediterranean region under extensive land use (Cerdà, 1997b; García-Ruiz, 2010). Abandoned lands typically have a rolling landscape with steep slopes, and are dominated by herbaceous communities that grow on pasture land interspersed by shrubs. Land abandonment use to trigger an increase in soil erosion, but the vegetation recovery reduces the impact of the vegetation. The goal of this work is to assess the effects of different Mediterranean shrub species (Dorycnium pentaphyllum Scop., Medicago strasseri, Colutea arborescens L., Retama sphaerocarpa, L., Pistacia Lentiscus L. and Quercus coccifera L.) on soil protection (runoff and soil losses) and on rainfall reaching soil surface (rainfall partitioning fluxes). To characterize the effects of shrub vegetation and to evaluate their effects on soil protection, two field experiments were carried out. The presence of shrub vegetation reduced runoff by

  20. Multiscale Bayesian neural networks for soil water content estimation

    NASA Astrophysics Data System (ADS)

    Jana, Raghavendra B.; Mohanty, Binayak P.; Springer, Everett P.

    2008-08-01

    Artificial neural networks (ANN) have been used for some time now to estimate soil hydraulic parameters from other available or more easily measurable soil properties. However, most such uses of ANNs as pedotransfer functions (PTFs) have been at matching spatial scales (1:1) of inputs and outputs. This approach assumes that the outputs are only required at the same scale as the input data. Unfortunately, this is rarely true. Different hydrologic, hydroclimatic, and contaminant transport models require soil hydraulic parameter data at different spatial scales, depending upon their grid sizes. While conventional (deterministic) ANNs have been traditionally used in these studies, the use of Bayesian training of ANNs is a more recent development. In this paper, we develop a Bayesian framework to derive soil water retention function including its uncertainty at the point or local scale using PTFs trained with coarser-scale Soil Survey Geographic (SSURGO)-based soil data. The approach includes an ANN trained with Bayesian techniques as a PTF tool with training and validation data collected across spatial extents (scales) in two different regions in the United States. The two study areas include the Las Cruces Trench site in the Rio Grande basin of New Mexico, and the Southern Great Plains 1997 (SGP97) hydrology experimental region in Oklahoma. Each region-specific Bayesian ANN is trained using soil texture and bulk density data from the SSURGO database (scale 1:24,000), and predictions of the soil water contents at different pressure heads with point scale data (1:1) inputs are made. The resulting outputs are corrected for bias using both linear and nonlinear correction techniques. The results show good agreement between the soil water content values measured at the point scale and those predicted by the Bayesian ANN-based PTFs for both the study sites. Overall, Bayesian ANNs coupled with nonlinear bias correction are found to be very suitable tools for deriving soil

  1. Organic compounds in hot-water-soluble fractions from water repellent soils

    NASA Astrophysics Data System (ADS)

    Atanassova, Irena; Doerr, Stefan

    2014-05-01

    Water repellency (WR) is a soil property providing hydrophobic protection and preventing rapid microbial decomposition of organic matter entering the soil with litter or plant residues. Global warming can cause changes in WR, thus influencing water storage and plant productivity. Here we assess two different approaches for analysis of organic compounds composition in hot water extracts from accelerated solvent extraction (ASE) of water repellent soils. Extracts were lyophilized, fractionated on SiO2 (sand) and SPE cartridge, and measured by GC/MS. Dominant compounds were aromatic acids, short chain dicarboxylic acids (C4-C9), sugars, short chain fatty acids (C8-C18), and esters of stearic and palmitic acids. Polar compounds (mainly sugars) were adsorbed on applying SPE clean-up procedure, while esters were highly abundant. In addition to the removal of polar compounds, hydrophobic esters and hydrocarbons (alkanes and alkenes < C20) were extracted through desorption of complex colloids stabilized as micelles in dissolved organic carbon (DOC). Water repellency was completely eliminated by hot water under high pressure. The molecular composition of HWSC can play a critical role in stabilization and destabilization of soil organic matter (SOM), particle wettability and C dynamics in soils. Key words: soil water repellency, hot water soluble carbon (HWSC), GC/MS, hydrophobic compounds

  2. Impact of regression methods on improved effects of soil structure on soil water retention estimates

    NASA Astrophysics Data System (ADS)

    Nguyen, Phuong Minh; De Pue, Jan; Le, Khoa Van; Cornelis, Wim

    2015-06-01

    Increasing the accuracy of pedotransfer functions (PTFs), an indirect method for predicting non-readily available soil features such as soil water retention characteristics (SWRC), is of crucial importance for large scale agro-hydrological modeling. Adding significant predictors (i.e., soil structure), and implementing more flexible regression algorithms are among the main strategies of PTFs improvement. The aim of this study was to investigate whether the improved effect of categorical soil structure information on estimating soil-water content at various matric potentials, which has been reported in literature, could be enduringly captured by regression techniques other than the usually applied linear regression. Two data mining techniques, i.e., Support Vector Machines (SVM), and k-Nearest Neighbors (kNN), which have been recently introduced as promising tools for PTF development, were utilized to test if the incorporation of soil structure will improve PTF's accuracy under a context of rather limited training data. The results show that incorporating descriptive soil structure information, i.e., massive, structured and structureless, as grouping criterion can improve the accuracy of PTFs derived by SVM approach in the range of matric potential of -6 to -33 kPa (average RMSE decreased up to 0.005 m3 m-3 after grouping, depending on matric potentials). The improvement was primarily attributed to the outperformance of SVM-PTFs calibrated on structureless soils. No improvement was obtained with kNN technique, at least not in our study in which the data set became limited in size after grouping. Since there is an impact of regression techniques on the improved effect of incorporating qualitative soil structure information, selecting a proper technique will help to maximize the combined influence of flexible regression algorithms and soil structure information on PTF accuracy.

  3. Monitoring of soil water content and quality inside and outside the water curtain cultivation facility

    NASA Astrophysics Data System (ADS)

    Ha, K.; Kim, Y.

    2014-12-01

    Water curtain cultivation system is an energy saving technique for winter season by splashing groundwater on the inner roof of green house. Artificial groundwater recharge application to the water curtain cultivation facilities was adopted and tested to use groundwater sustainably in a rural region of Korea. The groundwater level in the test site shows natural trend corresponding rainfall pattern except during mid-November to early April when groundwater levels decline sharply due to groundwater abstraction for water curtain cultivation. Groundwater levels are also affected by surface water such as stream, small dams in the stream and agricultural ditches. Infiltration data were collected from lysimeter installation and monitoring inside and outside water cultivation facility and compared with each other. The infiltration data were well correlated with rainfall outside the facility, but the data in the facility showed very different from the other. The missing infiltration data were attributed to groundwater level rise and level sensor location below water table. Soil water contents in the unsaturated zone indicated rainfall infiltration propagation at depth and with time outside the facility. According to rainfall amount and water condition at the initial stage of a rainfall event, the variation of soil water content was shown differently. Soil water contents and electrical conductivities were closely correlated with each other, and they reflected rainfall infiltration through the soil and water quality changes. The monitoring results are useful to reveal the hydrological processes from the infiltration to groundwater recharge, and water management planning in the water cultivation areas.

  4. Reflectance of vegetation, soil, and water

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L. (Principal Investigator)

    1973-01-01

    There are no author-identified significant results in this report. This report deals with the selection of the best channels from the 24-channel aircraft data to represent crop and soil conditions. A three-step procedure has been developed that involves using univariate statistics and an F-ratio test to indicate the best 14 channels. From the 14, the 10 best channels are selected by a multivariate stochastic process. The third step involves the pattern recognition procedures developed in the data analysis plan. Indications are that the procedures in use are satsifactory and will extract the desired information from the data.

  5. Improved Instrument for Detecting Water and Ice in Soil

    NASA Technical Reports Server (NTRS)

    Buehler, Martin; Chin, Keith; Keymeulen, Didler; McCann, Timothy; Seshadri, Suesh; Anderson, Robert

    2009-01-01

    An instrument measures electrical properties of relatively dry soils to determine their liquid water and/or ice contents. Designed as a prototype of instruments for measuring the liquid-water and ice contents of lunar and planetary soils, the apparatus could also be utilized for similar purposes in research and agriculture involving terrestrial desert soils and sands, and perhaps for measuring ice buildup on aircraft surfaces. This instrument is an improved version of the apparatus described in Measuring Low Concentrations of Liquid Water and Ice in Soil (NPO-41822), NASA Tech Briefs, Vol. 33, No. 2 (February 2009), page 22. The designs of both versions are based on the fact that the electrical behavior of a typical soil sample is well approximated by a network of resistors and capacitors in which resistances decrease and capacitances increase (and the magnitude and phase angle of impedance changes accordingly) with increasing water content. The previous version included an impedance spectrometer and a jar into which a sample of soil was placed. Four stainless-steel screws at the bottom of the jar were used as electrodes of a fourpoint impedance probe connected to the spectrometer. The present instrument does not include a sample jar and can be operated without acquiring or handling samples. Its impedance probe consists of a compact assembly of electrodes housed near the tip of a cylinder. The electrodes protrude slightly from the cylinder (see Figure 1). In preparation for measurements, the cylinder is simply pushed into the ground to bring the soil into contact with the electrodes.

  6. Groundwater surface water interactions and the role of phreatophytes in identifying recharge zones

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Groundwater and surface water interactions within riparian corridors impact the distribution of phreatophytes that tap into groundwater stores. The changes in canopy area of phreatophytes over time is related to changes in depth to groundwater, distance from a stream or river, and hydrologic soil gr...

  7. Interactions between soil moisture and Atmospheric Boundary Layer at the Brazilian savana-type vegetation Cerrado

    NASA Astrophysics Data System (ADS)

    Pinheiro, L. R.; Siqueira, M. B.

    2013-05-01

    Before the large people influx and development of the central part of Brazil in the sixties, due to new capital Brasília, Cerrado, a typical Brazilian savanna-type vegetation, used to occupy about 2 million km2, going all the way from the Amazon tropical forest, in the north of the country, to the edges of what used to be of the Atlantic forest in the southeast. Today, somewhat 50% of this area has given place to agriculture, pasture and managed forests. It is forecasted that, at the current rate of this vegetation displacement, Cerrado will be gone by 2030. Understanding how Cerrado interacts with the atmosphere and how this interaction will be modified with this land-use change is a crucial step towards improving predictions of future climate-change scenarios. Cerrado is a vegetation adapted to a climate characterized by two very distinct seasons, a wet season (Nov-Mar) and dry season (May-Ago), with April and October being transitions between seasons. Typically, based on measurements in a weather station located in Brasilia, 75% of precipitation happens in the wet-season months and only 5% during dry-season. Under these circumstances, it is clear that the vegetation will have to cope with long periods of water stress. In this work we studied using numerical simulations, the interactions between soil-moisture, responsible for the water stress, with the Atmospheric Boundary Layer (ABL). The numerical model comprises of a Soil-Vegetation-Atmosphere model where the biophysical processes are represented with a big-leaf approach. Soil water is estimated with a simple logistic model and with water-stress effects on stomatal conductance are parameterized from local measurements of simultaneous latent-heat fluxes and soil moisture. ABL evolution is calculate with a slab model that considers independently surface and entrainment fluxes of sensible- and latent- heat. Temperature tropospheric lapse-rate is taken from soundings at local airport. Simulations of 30-day dry

  8. Dynamic vertical interaction of a foundation-soil system generated by seismic waves

    NASA Astrophysics Data System (ADS)

    Wang, Peng; Wang, Jun; Cai, Yuanqiang; Gu, Chuan

    2014-05-01

    Based on Biot's dynamic poroelastic theory, a foundation-soil interaction model is established to investigate the vertical vibrations of a rigid circular foundation on poroelastic soil excited by incident plane waves, including the fast P waves and SV waves. Scattering waves caused by the foundation and fluid-solid coupling due to the pore water in the soil are also considered in the model. The solution of the vertical vibrations of the foundation subjected to seismic waves are obtained by solving two sets of dual integral equations derived from the mixed boundary-value conditions. The different vertical vibrations of foundation rest on elastic and saturated half-space are compared. The influences of incident angle, permeability of soil and foundation mass on the vertical vibrations of the foundation are then discussed. The results show that resonant phenomenon of the foundation is observed at certain excitation frequencies; the effects of the pore water on the foundation vertical vibrations are significant. In addition, significant differences are found when the foundation is excited by P waves and SV waves, respectively.

  9. Spatiotemporal Pattern of Root Water Uptake for Locally Differing Soil Water Availability

    NASA Astrophysics Data System (ADS)

    Dara, Abbas; Moradi, Ahmad B.; Oswald, Sascha

    2013-04-01

    One of the important but not well known questions is how the root system of a plant respond to water scarcity, especially if there is a locally heterogeneous distribution of soil moisture or accessibility of water. However, heterogeneous water availability is a typical characteristic of soils, for example by heterogeneity of soil properties, infiltration and evaporation or competition between plant roots. On top of that, water content in soil has a large temporal dynamics. Despite these intrinsic heterogeneities of soil-plant water relations, we know little about the ways how plants respond to local environmental properties. Recently imaging and tomography methods have become available, that facilitate the measurement of spatial and temporal distribution of water content and of the root system itself, which offers the possibility to investigate also the distribution of water uptake in a plant root system. To monitor root water uptake response to local soil water availability, we used neutron radiography especially suited to detect water distribution, to non-invasively image root growth and 2-D soil water distribution as time-lapsed images. We applied a method to hydraulically partition the soil to be able to actively control the level of water available locally and at the same time to locally quantify water uptake for these heterogeneous conditions. The key results for an imaging experiment running full three weeks show topological patterns of water uptake along the root system. Moreover, under water stress, compensatory root water uptake maximizes soil water utilization in response to transpiration demand. Lupin plants were grown in 40*35*1 cm³ aluminum containers. The root zone was partitioned into twenty compartments separated by capillary barriers and divides the root system into taproot and lateral roots, and into young and old later root segments at the top, middle and bottom profile positions. Three weeks after planting, four soil-water treatments in three

  10. Impact of alfalfa on soil and water quality

    SciTech Connect

    Sharma, P.; Moncrief, J.; Gupta, S.

    1997-10-30

    Dominance of row crop agriculture in rolling landscapes of western and Southwestern Minnesota is identified as a primary, non-point source of sediments and associated pollutants reaching the Minnesota River. Currently as a biomass energy project, alfalfa is being promoted in western Minnesota to harvest the leaves for animal feed and stems to generate electricity. As a perennial, leguminous crop grown with minimum inputs, introduction of alfalfa in row cropped lands has potential to improve both in-situ soil productivity and downstream water quality. A field study was initiated in 1996 to compare the volume of runoff and pollutants coming from alfalfa an com-soybean fields in western Minnesota. Two pair of alfalfa and corn-soybean watersheds were instrumented at Morris in the Fall of 1996 to measure rainfall, runoff, and sample water for sediment load, phosphorus, nitrogen, biochemical oxygen demand, and chemical oxygen demand. Simulated rainfall-runoff experiments were conducted on an existing crop rotation - input management study plots at Lamberton to evaluate soil quality effects of the inclusion of alfalfa in a corn-soybean rotation under manure and fertilization management schemes. Alfalfa soil water use as a function of frequency of harvest was also monitored at Morris to evaluate the effect of cutting schedule on soil water use. During the growing season of 1997, alfalfa under a two-cut management scheme used about 25-mm (an inch) more soil water than under a three-cut schedule. The mean differences between the treatments were not significant. The conclusions drawn in this report come from analysis of data collected during one winter-summer hydrologic and crop management cycle. Continued observations through a period of at least 3-5 years is recommended to improve the instrumentation robustness and discern the variability due to climate, soil, and crop management factors.

  11. Water percolation through the root-soil interface

    NASA Astrophysics Data System (ADS)

    Benard, Pascal; Kroener, Eva; Vontobel, Peter; Kaestner, Anders; Carminati, Andrea

    2016-04-01

    Plant roots exude a significant fraction of the carbon assimilated via photosynthesis into the soil. The mucilaginous fraction of root exudates affects the hydraulic properties of the soil near the roots, the so called rhizosphere, in a remarkable and dynamic way. After drying, mucilage becomes hydrophobic and limits the rewetting of the rhizosphere. Here, we aim to find a quantitative relation between rhizosphere rewetting, particle size, soil matric potential and mucilage concentration. We used a pore-network model in which mucilage was randomly distributed in a cubic lattice. The general idea was that the mucilage concentration per solid soil surface increases the contact angle between the liquid and solid phases consequently limiting the rewetting of pores covered with dry mucilage. We used the Young-Laplace equation to calculate the mucilage concentration at which pores are not wettable for varying particle sizes and matric potentials. Then, we simulated the percolation of water across a cubic lattice. Our simulations predicted that above a critical mucilage concentration water could not flow through the porous medium. The critical mucilage concentration decreased with increasing particle size and decreasing matric potential. The model was compared with experiments of capillary rise in soils of different particle size and mucilage concentration. The experiments confirmed the percolation behaviour of the rhizosphere rewetting. Mucilage turned hydrophobic at concentrations above 0.1 mg/cm². The critical mucilage concentration at matric potential of -2.5 hPa was ca. 1% [g/g] for fine sand and 0.1 % [g/g] for coarse sand. Our conceptual model is a first step towards a better understanding of the water dynamics in the rhizosphere during rewetting and it can be used to predict in what soil textures rhizosphere water repellency becomes a critical issue for root water uptake.

  12. Selenium status in soil, water and essential crops of Iran.

    PubMed

    Nazemi, Lyly; Nazmara, Shahrokh; Eshraghyan, Mohammad Reza; Nasseri, Simin; Djafarian, Kurosh; Yunesian, Masoud; Sereshti, Hassan; Moameni, Aziz; Shahtaheri, Seyed Jamaleddin

    2012-01-01

    As a contributing factor to health, the trace element selenium (Se) is an essential nutrient of special interest for humans and all animals. It is estimated that 0.5 to 1 billion people worldwide suffer from Se deficiency. In spite of the important role of Se, its concentrations in soil, water and essential crops have not been studied in Iran. Therefore, the main aim of the current study was to determine the Se content of soil, water, and essential crops (rice in North, wheat in Center, date, and pistachio in South) of different regions of Iran. Sampling was performed in the North, South, and Central regions of Iran. In each selected area in the three regions, 17 samples of surface soil were collected; samples of water and essential crops were also collected at the same sampling points. Upon preliminary preparation of all samples, the Se concentrations were measured by ICP-OES Model Varian Vista-MPX. The amount of soil-Se was found to be in the range between 0.04 and 0.45 ppm in the studied areas; the Se content of soil in the central region of Iran was the highest compared to other regions (p<0.0001). The average Se concentration in irrigation water of different areas was less than 0.01 mg/L, and the mean concentrations of Se in the rice, wheat, date, and pistachio samples were 0.95, 0.74, 0.46, and 0.40 ppm, respectively. Although Se-soil and water-Se level in different regions were low, the typical levels of Se in the essential crops were relatively high. PMID:23369199

  13. The impact of soil moisture variability on seasonal convective precipitation simulations via the soil-boundary layer interaction.

    NASA Astrophysics Data System (ADS)

    Khodayar, S.; Kalthoff, N.; Schädler, G.

    2012-04-01

    model validation, in combination with seasonal climate simulations with the Consortium for Small-Scale modelling (COSMO) model in his climate version (CCLM) were used to investigate the seasonal climatology of the investigation area, as well as the interactions between the soil and the atmosphere in the complex orographic region of western Germany and eastern France. The impact of realistic model initialization with SM measurements from COPS on convective precipitation will be discussed. Additionally, the impact of the prescribed soil type distribution on seasonal climate simulations will be demonstrated. The combination of dense observations with CCLM simulations permitted a rigorous analysis of the water transfer process chain from SM and fluxes to convective initiation and precipitation.

  14. Effect of Soil Water Potential on Survival of Meloidogyne javanica in Fallow Soil

    PubMed Central

    Towson, A. J.; Apt, W. J.

    1983-01-01

    A natural infestation of Meloidogyne javanica in an aggregated Oxisol declined at an exponential rate when aliquots of the soil were stored for 72 days in polyethylene bags at various soil water potentials (Ψ). Time periods required for reduction in soil infestations by 50% were 2.7, 4.9, 110, 10, and 2.6 days at Ψ of -0.16, -0.30, -1.1, -15, and -92 bars, respectively. In the wetter soils, at Ψ of -0.16, -0.30, and -1.1 bars, the predominant stage recovered was the second-stage larva. In the drier soils, at Ψ of -15 and -92 bars, both eggs and larvae were recovered with neither stage predominating. Incidence of coiled larvae was inversely related to the Ψ value of the soil, a greater incidence occurring in the drier soils. After 15-32 days, percentages of coiled larvae were 13, 27, 55, 65, and 88% in soil at Ψ of -0.17, -0.60, -1.9, -15, and -82 bars, respectively. PMID:19295774

  15. Subsurface drip irrigation emitter spacing effects on soil water redistribution, corn yield, and water productivity

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Emitter spacings of 0.3 to 0.6 m are commonly used for subsurface drip irrigation (SDI) of corn on the deep, silt loam soils of the United States Great Plains. Subsurface drip irrigation emitter spacings of 0.3, 0.6, 0.9 and 1.2 m were examined for the resulting differences in soil water redistribut...

  16. The importance of plant-soil interactions for N mineralisation in different soil types

    NASA Astrophysics Data System (ADS)

    Murphy, Conor; Paterson, Eric; Baggs, Elizabeth; Morley, Nicholas; Wall, David; Schulte, Rogier

    2013-04-01

    The last hundred years has seen major advancements in our knowledge of nitrogen mineralisation in soil, but key drivers and controls remain poorly understood. Due to an increase in the global population there is a higher demand on food production. To accommodate this demand agriculture has increased its use of N based fertilizers, but these pose risks for water quality and GHG emissions as N can be lost through nitrate leaching, ammonia volatilization, and denitrification processes (Velthof, et al., 2009). Therefore, understanding the underlying processes that determine the soils ability to supply N to the plant is vital for effective optimisation of N-fertilisation with crop demand. Carbon rich compounds exuded from plant roots to the rhizosphere, which are utilized by the microbial biomass and support activities including nutrient transformations, may be a key unaccounted for driver of N mineralisation. The main aim of this study was to study the impact of root exudates on turnover of C and N in soil, as mediated by the microbial community. Two soil types, known to contrast in N-mineralisation capacity, were used to determine relationships between C inputs, organic matter mineralisation (priming effects) and N fluxes. 15N and 13C stable isotope approaches were used to quantify the importance of rhizosphere processes on C and N mineralisation. Gross nitrogen mineralisation was measured using 15N pool dilution. Total soil CO2 efflux was measured and 13C isotope partitioning was applied to quantify SOM turnover and microbial biomass respiration. Also, 13C was traced through the microbial biomass (chloroform fumigation) to separate pool-substitution effects (apparent priming) from altered microbial utilisation of soil organic matter (real priming effects). Addition of labile carbon resulted in an increase in N-mineralisation from soil organic matter in both soils. Concurrent with this there was an increase in microbial biomass size, indicating that labile C elicited

  17. Interaction Effects of Selected Pesticides on Soil Enzymes

    PubMed Central

    Deborah, B. Vineela; Mohiddin, M. Jaffer; Madhuri, R. Jaya

    2013-01-01

    The laboratory studies were conducted to resolute the effects of imidacloprid (insecticide) and triadimefon (fungicide) singly and in combination on enzymatic activities of soil microorganisms in tomato cultivated soils at different concentrations of 0.2, 0.5 and 0.7 kg/ha. The rate of amylase activity was stimulated by the application of pesticides at field rate. High dosage decreased the activity of amylase. Decline in the activity of cellulase was observed at all concentrations than control. Imidacloprid had an improved activity of cellulase at 0.5 μg/g than tridimefon and combination. At higher concentration (0.7 μg/g), the combination of insecticide and fungicide showed an antagonistic interaction toward cellulase. After 24 h, maximum inhibition was observed in invertase enzyme rate at all examined dosages. After 48 h, the activity was revived to some extent and imidacloprid showed enhanced activity at 0.5 μg/g (field rate). However at 0.7 μg/g, imidacloprid has a noticeable effect on the invertase. The pesticide application in single and in combination (0.2-0.7 μg/g soil) triggered the dehydrogenase activity. At field rate triadimefon significantly quickened the activity. PMID:24403727

  18. USING ENSEMBLE PREDICTIONS TO SIMULATE FIELD-SCALE SOIL WATER TIME SERIES WITH UPSCALED AND DOWNSCALED SOIL HYDRAULIC PROPERTIES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Simulations of soil water flow require measurements of soil hydraulic properties which are particularly difficult at field scale. Laboratory measurements provide hydraulic properties at scales finer than the field scale, whereas pedotransfer functions (PTFs) integrate information on hydraulic prope...

  19. Mobility of organic solvents in water-saturated soil materials

    USGS Publications Warehouse

    Roy, W.R.; Griffin, R.A.

    1985-01-01

    This investigation presents an analysis of the mobility of 37 organic solvents in saturated soil-water systems, focusing on adsorption phenomena at the solid-liquid interface This analysis was made, in part, by applying predictive expressions that estimate the potential magnitude of adsorption by soil materials Of the 37 solvents considered, 19 were classified as either "very highly mobile" or "highly mobile" and, thus, would have little tendency to be retained by soils to a significant extent, 12 were considered to have medium mobility and 6 low mobility None of these solvents were in the immobile class The limited information available indicates that these predictive expressions yield satisfactory first approximations of the magnitude of adsorption of these solvents by soil materials ?? 1985 Springer-Verlag New York Inc.

  20. Internal water balance of barley under soil moisture stress.

    PubMed

    Millar, A A; Duysen, M E; Wilkinson, G E

    1968-06-01

    Leaf water potential, leaf relative water content, and relative transpiration of barley were determined daily under greenhouse conditions at 3 growth stages: tillering to boot, boot to heading, and heading to maturity. The leaf moisture characteristic curve (relative water content versus leaf water potential) was the same for leaves of the same age growing in the same environment for the first 2 stages of growth, but shifted at the heading to maturity stage to higher leaf relative water content for a given leaf water potential. Growth chamber experiments showed that the leaf moisture characteristic curve was not the same for plants growing in different environments.Relative transpiration data indicated that barley stomates closed at a water potential of about -22 bars at the 3 stages studied.The water potential was measured for all the leaves on barley to determine the variation of water potential with leaf position. Leaf water potential increased basipetally with plant leaf position. In soil with a moisture content near field capacity a difference of about 16.5 bars was observed between the top and bottom leaves on the same plant, while in soil with a moisture content near the permanent wilting point the difference was only 5.6 bars between the same leaf positions. PMID:16656869

  1. Bacteria-mineral interactions in soil and their effect on particle surface properties

    NASA Astrophysics Data System (ADS)

    Miltner, Anja; Achtenhagen, Jan; Goebel, Marc-Oliver; Bachmann, Jörg; Kästner, Matthias

    2015-04-01

    Interactions between bacteria or their residues and mineral surfaces play an important role for soil processes and properties. It is well known that bacteria tend to grow attached to surfaces and that they get more hydrophobic when grown under stress conditions. In addition, bacterial and fungal biomass residues have recently been shown to contribute to soil organic matter formation. The attachment of bacteria or their residues to soil minerals can be expected to modify the surface properties of these particles, in particular the wettability. We hypothesize that the extent of the effect depends on the surface properties of the bacteria, which change depending on environmental conditions. As the wettability of soil particles is crucial for the distribution and the availability of water, we investigated the effect of both living cells and bacterial residues (cell envelope fragments and cytosol) on the wettability of model mineral particles in a simplified laboratory system. We grew Pseudomonas putida cells in mineral medium either without (unstressed) or with additional 1.5 M NaCl (osmotically stressed). After 2 h of incubation, the cells were disintegrated by ultrasonic treatment. Different amounts of either intact cells, cell envelope fragments or cytosol (each corresponding to 108, 109, or 1010 cells per gram of mineral) were mixed with quartz sand, quartz silt or kaolinite. The bacteria-mineral associations were air-dried for 2 hours and analyzed for their contact angle. We found that the surfaces of osmotically stressed cells were more hydrophobic than the surfaces of unstressed cells and that the bacteria-mineral associations had higher contact angles than the pure minerals. A rather low surface coverage (~10%) of the mineral surfaces by bacteria was sufficient to increase the contact angle significantly, and the different wettabilities of stressed and unstressed cells were reflected in the contact angles of the bacteria-mineral associations. The increases in

  2. Surface water and groundwater interaction on a hill island

    NASA Astrophysics Data System (ADS)

    Rumph Frederiksen, Rasmus; Rømer Rasmussen, Keld; Christensen, Steen

    2014-05-01

    A number of recent studies have indicated that the hydrological system in stream valleys is often complex and exchange of water takes place through semi-permeable contacts and flow paths may be quite diverse. Yet, surface water and groundwater interaction in one of the major Danish landscapes - the hill islands - is relatively unknown. This study aims at providing new information about the rainfall-runoff processes in hill island landscapes where surface water and groundwater interaction is expected to have a dominant role and hill-slope processes not. Through stream flow measurements, field observations, and existing geological and geophysical data, we have investigated the surface water and groundwater interaction in the Abild Stream catchment (<70 km2) on Skovbjerg hill island in the western part of Denmark. Existing discharge data are limited but the hydrographs downstream Abild Stream appear to be strongly influenced by event flow indicating that shallow control by low permeable sediments is important. Nevertheless irrigation is intensive which indicates that the soil and shallow sediments are permeable. Since July 2014 we have measured stream flow during quarterly campaigns at 11 stations along the stream representing different spatial scales and using Acoustic Doppler techniques (ADCP) as well as current-meters. Furthermore we have mapped topography, soil types, geomorphology, ditches, drains and land use through field observations and digital maps. The shallow subsurface geology has been mapped using abundant well described geological data (boreholes) and geophysical data (airborne TEM). Our stream flow measurements show that the tributaries from west and north dry out during the summer period. Significant drained areas in the NW- and SW-part of the catchment have been observed from old topographical maps as well as in the field. The geological data indicate shallow low permeable sediments primarily on the western side of Abild stream, and the geophysical

  3. Soil water distribution and water use efficiency of forage and grain soybeans in the southern Great Plains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Growing legumes during summer fallow periods between wheat crops in the southern Great Plains (SGP) can reduce soil erosion and add nitrogen to the soil. However, information on water use by legumes and effects on water availability for subsequent wheat crops is limited. We described soil water patt...

  4. 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 ...

  5. A method to extract soil water for stable isotope analysis

    USGS Publications Warehouse

    Revesz, K.; Woods, P.H.

    1990-01-01

    A method has been developed to extract soil water for determination of deuterium (D) and 18O content. The principle of this method is based on the observation that water and toluene form an azeotropic mixture at 84.1??C, but are completely immiscible at ambient temperature. In a specially designed distillation apparatus, the soil water is distilled at 84.1??C with toluene and is separated quantitatively in the collecting funnel at ambient temperature. Traces of toluene are removed and the sample can be analyzed by mass spectrometry. Kerosene may be substituted for toluene. The accuracy of this technique is ?? 2 and ?? 0.2???, respectively, for ??D and ??18O. Reduced accuracy is obtained at low water contents. ?? 1990.

  6. Soil properties evolution after irrigation with reclaimed water

    NASA Astrophysics Data System (ADS)

    Leal, M.; González-Naranjo, V.; de Miguel, A.; Martínez-Hernández, V.; Lillo, J.

    2012-04-01

    Many arid and semi-arid countries are forced to look for new and alternative water sources. The availability of suitable quality water for agriculture in these regions often is threatened. In this context of water scarcity, the reuse of treated wastewater for crop irrigation could represent a feasible solution. Through rigorous planning and management, irrigation with reclaimed water presents some advantages such as saving freshwater, reducing wastewater discharges into freshwater bodies and decreasing the amount of added fertilizers due to the extra supply of nutrients by reclaimed water. The current study, which involves wastewater reuse in agriculture, has been carried out in the Experimental Plant of Carrión de los Céspedes (Sevile, Spain). Here, two survey parcels equally designed have been cultivated with Jatropha curcas L, a bioenergetic plant and a non-interfering food security crop. The only difference between the two parcels lies on the irrigation water quality: one is irrigated with groundwater and another one with reclaimed water. The main aim of this study focuses on analysing the outstanding differences in soil properties derived from irrigation with two water qualities, due to their implications for plant growth. To control and monitor the soil variables, soil samples were collected before and after irrigation in the two parcels. pH, electrical conductivity, cation exchange capacity, exchangeable cations (Ca2+, Mg2+, Na+ and K+), kjeldahl nitrogen, organic matter content and nutrients (boron, phosphorus, nitrogen, potassium) were measured. Data were statistically analyzed using the R package. To evaluate the variance ANOVA test was used and to obtain the relations between water quality and soil parameters, Pearson correlation coefficient was computed. According to other authors, a decrease in the organic matter content and an increase of parameters such as pH, electrical conductivity and some exchangeable cations were expected. To date and after

  7. Hysteresis and uncertainty in soil water-retention curve parameters

    USGS Publications Warehouse

    Likos, William J.; Lu, Ning; Godt, Jonathan W.

    2014-01-01

    Accurate estimates of soil hydraulic parameters representing wetting and drying paths are required for predicting hydraulic and mechanical responses in a large number of applications. A comprehensive suite of laboratory experiments was conducted to measure hysteretic soil-water characteristic curves (SWCCs) representing a wide range of soil types. Results were used to quantitatively assess differences and uncertainty in three simplifications frequently adopted to estimate wetting-path SWCC parameters from more easily measured drying curves. They are the following: (1) αw=2αd, (2) nw=nd, and (3) θws=θds, where α, n, and θs are fitting parameters entering van Genuchten’s commonly adopted SWCC model, and the superscripts w and d indicate wetting and drying paths, respectively. The average ratio αw/αd for the data set was 2.24±1.25. Nominally cohesive soils had a lower αw/αd ratio (1.73±0.94) than nominally cohesionless soils (3.14±1.27). The average nw/nd ratio was 1.01±0.11 with no significant dependency on soil type, thus confirming the nw=nd simplification for a wider range of soil types than previously available. Water content at zero suction during wetting (θws) was consistently less than during drying (θds) owing to air entrapment. The θws/θds ratio averaged 0.85±0.10 and was comparable for nominally cohesive (0.87±0.11) and cohesionless (0.81±0.08) soils. Regression statistics are provided to quantitatively account for uncertainty in estimating hysteretic retention curves. Practical consequences are demonstrated for two case studies.

  8. 77 FR 35323 - National Environmental Policy Act: Categorical Exclusions for Soil and Water Restoration Activities

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-06-13

    ... for Soil and Water Restoration Activities AGENCY: Forest Service, USDA. ACTION: Notice of proposed... effects of soil and water restoration projects that are intended to restore the flow of waters into... activities that achieve soil and water restoration objectives. The Forest Service's proposed...

  9. Sensible heat balance measurements of soil water evaporation beneath a maize canopy

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water evaporation is an important component of the water budget in a cropped field. Few methods are available for continuous and independent measurement of soil water evaporation. A sensible heat balance (SHB) approach has recently been demonstrated for continuously determining soil water evapo...

  10. The utility of surface temperature measurements for the remote sensing of surface soil water status

    NASA Technical Reports Server (NTRS)

    Idso, S. B.; Jackson, R. D.; Reginato, R. J.; Schmugge, T. J.

    1975-01-01

    Experiments carried out on an Avondale loam soil indicated that the thermal inertia concept of soil water content detection is reasonably sound. The volumetric water contents of surface soil layers between 2 and 4 cm thick were found to be linear functions of the amplitude of the diurnal surface soil temperature wave for clear day-night periods. They were also found to be linear functions of the daily maximum value of the surface soil-air-temperature differential. Tests on three additional soils ranging from sandy loam to clay indicated that the relations determined for Avondale loam could not be accurately applied to these other soil types. When the moisture characteristic curves of each soil were used to transform water contents into pressure potentials, however, it was found that soil water pressure potential could be determined without prior knowledge of soil type, and thus its value as a potential soil water status survey tool was significantly enhanced.

  11. Soil erosion-vegetation interactions in Mediterranean-dry reclaimed mining slopes

    NASA Astrophysics Data System (ADS)

    Moreno de las Heras, Mariano; Merino-Martín, Luis; Espigares, Tíscar; Nicolau, José M.

    2014-05-01

    Mining reclamation in Mediterranean-dry environments represents a complex task. Reclaimed mining slopes are particularly vulnerable to the effects of accelerated soil erosion processes, especially when these processes lead to the formation of rill networks. On the other hand, encouraging early vegetation establishment is perceived as indispensable to reduce the risk of degradation in these man-made ecosystems. This study shows a synthesis of soil erosion-vegetation research conducted in reclaimed mining slopes at El Moral field site (Teruel coalfield, central-east Spain). Our results highlight the role of rill erosion processes in the development of reclaimed ecosystems. Runoff routing is conditioned by the development of rill networks, maximizing the loss of water resources at the slope scale by surface runoff and altering the spatial distribution of soil moisture. As a result, the availability of water resources for plant growth is drastically reduced, affecting vegetation development. Conversely, vegetation exerts a strong effect on soil erosion: erosion rates rapidly decrease with vegetation cover and no significant rill erosion is usually observed after a particular cover threshold is reached. These interactive two-way vegetation-soil erosion relationships are further studied using a novel modeling approach that focuses on stability analysis of water-limited reclaimed slopes. Our framework reproduces two main groups of trends along the temporal evolution of reclaimed slopes: successful trends, characterized by widespread vegetation development and the effective control of rill erosion processes; and gullying trends, characterized by the progressive loss of vegetation and a sharp logistic increase in erosion rates. This stability-analysis also facilitates the determination of threshold values for both vegetation cover and rill erosion that drive the long-term reclamation results, assisting the identification of critical situations that require specific human

  12. Morphology of Rain Water Channeling in Systematically Varied Model Sandy Soils

    NASA Astrophysics Data System (ADS)

    Wei, Yuli; Cejas, Cesare M.; Barrois, Rémi; Dreyfus, Rémi; Durian, Douglas J.

    2014-10-01

    We visualize the formation of fingered flow in dry model sandy soils under different rain conditions using a quasi-2D experimental setup and systematically determine the impact of the soil grain diameter and surface wetting properties on the water channeling phenomenon. The model sandy soils we use are random closely packed glass beads with varied diameters and surface treatments. For hydrophilic sandy soils, our experiments show that rain water infiltrates a shallow top layer of soil and creates a horizontal water wetting front that grows downward homogeneously until instabilities occur to form fingered flows. For hydrophobic sandy soils, in contrast, we observe that rain water ponds on the top of the soil surface until the hydraulic pressure is strong enough to overcome the capillary repellency of soil and create narrow water channels that penetrate the soil packing. Varying the raindrop impinging speed has little influence on water channel formation. However, varying the rain rate causes significant changes in the water infiltration depth, water channel width, and water channel separation. At a fixed rain condition, we combine the effects of the grain diameter and surface hydrophobicity into a single parameter and determine its influence on the water infiltration depth, water channel width, and water channel separation. We also demonstrate the efficiency of several soil water improvement methods that relate to the rain water channeling phenomenon, including prewetting sandy soils at different levels before rainfall, modifying soil surface flatness, and applying superabsorbent hydrogel particles as soil modifiers.

  13. Influence of soil moisture-carbon cycle interactions on the terrestrial carbon cycle over Europe

    NASA Astrophysics Data System (ADS)

    Mystakidis, Stefanos; Davin, Edouard L.; Gruber, Nicolas; Seneviratne, Sonia I.

    2016-04-01

    Water availability is a crucial limiting factor for terrestrial ecosystems, but relatively few studies have quantitatively assessed the influence of soil moisture variability on the terrestrial carbon cycle. Here, we investigate the role of soil moisture variability and state in the contemporary terrestrial carbon cycle over Europe. For this we use a Regional Earth System Model (RESM) based on the COSMO-CLM Regional Climate Model, coupled to the Community Land Model version 4.0 (CLM4.0) and its carbon-nitrogen module. The simulation setup consists of a control simulation over the period 1979-2010 in which soil moisture is interactive and three sensitivity simulations in which soil moisture is prescribed to a mean, a very dry or a very wet seasonal cycle without inter-annual variability. The cumulative net biome productivity varies markedly between the different experiments ranging from a strong sink of up to 6PgC in the wet experiment to a source of up to 1.2PgC in the dry experiment. Changes in the land carbon uptake are driven by a combination of two factors: the direct impact of soil moisture on plant's carbon uptake (essentially in southern Europe) and an indirect effect through changes in temperature affecting ecosystem respiration (mainly in central and northern Europe). We find that removing temporal variations in soil moisture dampens interannual variations in terrestrial carbon fluxes (Gross Primary Productivity, respiration, Net Biome Productivity) by more than 50% over most of Europe. Moreover, the analysis reveals that on annual scale about two-thirds of central Europe and about 70% of southern Europe display statistically significant effect of drying and/or wetting on the terrestrial carbon budget and its components. Our findings confirm the crucial role of soil moisture in determining the magnitude and the inter-annual variability in land CO2 uptake which is a key contributor to the year-to-year variations in atmospheric CO2 concentration.

  14. SOIL-SOILN simulations of water drainage and nitrate nitrogen transport from soil core lysimeters.

    PubMed

    Jabro, J D; Stout, W L; Fales, S L; Fox, R H

    2001-01-01

    Water resources protection from nitrate nitrogen (NO3-N) contamination is an important public concern and a major national environmental issue. The abilities of the SOIL-SOILN model to simulate water drainage and nitrate N fluxes from orchardgrass (Dactylis glomerata L.) were evaluated using data from a 3-yr field experiment. The soil is classified as a Hagerstown silt loam soil (fine, mixed, semiactive, mesic Typic Hapludalf). Nitrate losses below the 1-m depth from N-fertilized grazed orchardgrass were measured with intact soil core lysimeters. Five N-fertilizer treatments consisted of a control, urine application in the spring, urine application in the summer, urine application in the fall, and feces application in the summer. The SOIL-SOILN models were evaluated using water drainage and nitrate flux data for 1993-1994, 1994-1995, and 1995-1996. The N rate constants from a similar experiment with inorganic fertilizer and manure treatments under corn (Zea mays L.) were used to evaluate the SOILN model under orchardgrass sod. Results indicated that the SOIL model accurately simulated water drainage for all three years. The SOILN model adequately predicted nitrate losses for three urine treatments in each year and a control treatment in 1994-1995. However, it failed to produce accurate simulations for two control treatments in 1993-1994 and 1995-1996, and feces treatments in all three years. The inaccuracy in the simulation results for the control and feces treatments seems to be related to an inadequate modeling of N transformation processes. In general, the results demonstrate the potential of the SOILN model to predict NO3-N fluxes under pasture conditions using N transformation rate constants determined through the calibration process from corn fields on similar soils. PMID:11285920

  15. Application of minidisk infiltrometer to estimate soil water repellency

    NASA Astrophysics Data System (ADS)

    Alagna, Vincenzo; Iovino, Massimo; Bagarello, Vincenzo; Mataix-Solera, Jorge; Lichner, Ľubomír

    2016-04-01

    Soil water repellency (SWR) reduces affinity of soils to water resulting in detrimental implication for plants growth as well as for hydrological processes. During the last decades, it has become clear that SWR is much more widespread than formerly thought, having been reported for a wide variety of soils, land uses and climatic conditions. The repellency index (RI), based on soil-water to soil-ethanol sorptivity ratio, was proposed to characterize subcritical SWR that is the situation where a low degree of repellency impedes infiltration but does not prevent it. The minidisk infiltrometer allows adequate field assessment of RI inherently scaled to account for soil physical properties other than hydrophobicity (e.g., the volume, connectivity and the geometry of pores) that directly influence the hydrological processes. There are however some issues that still need consideration. For example, use of a fixed time for both water and ethanol sorptivity estimation may lead to inaccurate RI values given that water infiltration could be negligible whereas ethanol sorptivity could be overestimated due to influence of gravity and lateral diffusion that rapidly come into play when the infiltration process is very fast. Moreover, water and ethanol sorptivity values need to be determined at different infiltration sites thus implying that a large number of replicated runs should be carried out to obtain a reliable estimate of RI for a given area. Minidisk infiltrometer tests, conducted under different initial soil moisture and management conditions in the experimental sites of Ciavolo, Trapani (Italy) and Javea, Alicante (East Spain), were used to investigate the best applicative procedure to estimate RI. In particular, different techniques to estimate the water, Sw, and ethanol, Se, sorptivities were compared including i) a fixed 1-min time interval, ii) the slope of early-time 1D infiltration equation and iii) the two-term transient 3D infiltration equation that explicitly

  16. Plant Response to Differential Soil Water Content and Salinity

    NASA Astrophysics Data System (ADS)

    Moradi, A. B.; Dara, A.; Kamai, T.; Ngo, A.; Walker, R.; Hopmans, J. W.

    2011-12-01

    Root-zone soil water content is extremely dynamic, governed by complex and coupled processes such as root uptake, irrigation, evaporation, and leaching. Root uptake of water and nutrients is influenced by these conditions and the processes involved. Plant roots are living and functioning in a dynamic environment that is subjected to extreme changes over relatively short time and small distances. In order to better manage our agricultural resources and cope with increasing constraints of water limitation, environmental concerns and climate change, it is vital to understand plants responses to these changes in their environment. We grew chick pea (Cicer arietinum) plants, in boxes of 30 x 25 x 1 cm dimensions filled with fine sand. Layers of coarse sand (1.5 cm thick) were embedded in the fine-sand media to divide the root growth environment into sections that were hydraulically disconnected from each other. This way, each section could be independently treated with differential levels of water and salinity. The root growth and distribution in the soil was monitored on daily bases using neutron radiography. Daily water uptake was measured by weighing the containers. Changes of soil water content in each section of the containers were calculated from the neutron radiographs. Plants that part of their root system was stressed with drought or salinity showed no change in their daily water uptake rate. The roots in the stressed sections stayed turgid during the stress period and looked healthy in the neutron images. However the uptake rate was severely affected when the soil in the non-stressed section started to dry. The plants were then fully irrigated with water and the water uptake rate recovered to its initial rate shortly after irrigation. The neutron radiographs clearly illustrated the shrinkage and recovery of the roots under stress and the subsequent relief. This cycle was repeated a few times and the same trend could be reproduced. Our results show that plants

  17. [Soil water resource use limit in semi-arid loess hilly area].

    PubMed

    Guo, Zhong-sheng

    2010-12-01

    Taking Caragana korshinskii as test object, and by using neutron probe, a long term observation was conducted on the soil water and plant growth during the process of vegetation restoration in semi-arid loess hilly area. The results showed that after seeding on waste land, the capability of plant community in conserving soil and water was promoted with time, with the depth of roots to absorb and use soil water increased and the soil water content reduced. Then, the dried soil layer appeared, and its deepness and thickness increased with increasing plant age. Therefore, the plant use of soil water had a limit, soil water resource use limit, i.e., the soil water storage when the deepness of dried soil layer was equal to the largest depth that rain could recharge. In the C. korshinskii woodland in semi-arid loess hilly area, the soil water resource use limit in 0-290 cm layer was 249.4 mm. When the soil water storage in woodland was close or equal to the soil water resource use limit, effective measures should be taken to decrease soil evapotranspiration or increase soil water supply to ensure the sustainable water use of plant roots. PMID:21442986

  18. Observing plants dealing with soil water stress: Daily soil moisture fluctuations derived from polymer tensiometers

    NASA Astrophysics Data System (ADS)

    van der Ploeg, Martine; de Rooij, Gerrit

    2014-05-01

    Periods of soil water deficit often occur within a plant's life cycle, even in temperate deciduous and rain forests (Wilson et al. 2001, Grace 1999). Various experiments have shown that roots are able to sense the distribution of water in the soil, and produce signals that trigger changes in leaf expansion rate and stomatal conductance (Blackman and Davies 1985, Gollan et al. 1986, Gowing et al. 1990 Davies and Zhang 1991, Mansfield and De Silva 1994, Sadras and Milroy 1996). Partitioning of water and air in the soil, solute distribution in soil water, water flow through the soil, and water availability for plants can be determined according to the distribution of the soil water potential (e.g. Schröder et al. 2013, Kool et al. 2014). Understanding plant water uptake under dry conditions has been compromised by hydrological instrumentation with low accuracy in dry soils due to signal attenuation, or a compromised measurement range (Whalley et al. 2013). Development of polymer tensiometers makes it possible to study the soil water potential over a range meaningful for studying plant responses to water stress (Bakker et al. 2007, Van der Ploeg et al. 2008, 2010). Polymer tensiometer data obtained from a lysimeter experiment (Van der Ploeg et al. 2008) were used to analyse day-night fluctuations of soil moisture in the vicinity of maize roots. To do so, three polymer tensiometers placed in the middle of the lysimeter from a control, dry and very dry treatment (one lysimeter per treatment) were used to calculate water content changes over 12 hours. These 12 hours corresponded with the operation of the growing light. Soil water potential measurements in the hour before the growing light was turned on or off were averaged. The averaged value was used as input for the van Genuchten (1980) model. Parameters for the model were obtained from laboratory determination of water retention, with a separate model parameterization for each lysimeter setup. Results show daily

  19. Plant root-driven hydraulic redistribution, root nutrient uptake and carbon exudation interact with soil properties to generate rhizosphere resource hotspots that vary in space and time

    NASA Astrophysics Data System (ADS)

    Espeleta, J. F.; Neumann, R. B.; Cardon, Z. G.; Mayer, K. U.; Rastetter, E. B.

    2014-12-01

    Hydraulic redistribution (HR) of soil water by plants occurs in seasonally dry ecosystems worldwide. During drought, water flows from deep moist soil, through plant roots, into dry (often litter-rich) upper soil layers. Using modeling, we explored how physical transport processes driven by transpiration and hydraulic redistribution interact with root physiology (nutrient uptake and carbon exudation) and soil properties (soil texture and cation exchange) to influence nitrogen and carbon concentrations in the rhizosphere. At the single root scale, we modeled a 10-cm radial soil domain, and simulated solute transport, soil cation exchange, and root exudation and nutrient uptake under two water flow patterns: daytime transpiration without nighttime HR, and daytime transpiration with nighttime HR. During HR, water efflux flushed solutes away from the root, diluting the concentrations of key nutrients like nitrate. The transport of cations by transpiration in the day and their accumulation near the root led to competitive desorption of ammonium from soil further from the root and generation of hotspots of ammonium availability at night. HR influenced the spatial and temporal patterns of these hotspots and their intensity. They were also influenced by soil properties of texture and cation exchange capacity. This dynamic resource landscape caused by diel cycling between transpiration and hydraulic redistribution presents a stage for greater complexity of microbial interactions. We are currently embedding a microbial community and small food web into this rhizosphere model in order to explore how organisms responsible for nutrient and soil carbon cycling respond to these fluctuating resource regimes.

  20. Quantification of soil water evaporation using TDR-microlysimetry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water evaporation is conventionally measured using microlysimeters by evaluating the daily change in mass. Daily removal is laborious and replacement immediately after irrigation events is impractical because of field wetness which leads to delays and an underestimation of evaporation. Irrigati...

  1. Electrical resistance sensors for soil water tension estimates

    Technology Transfer Automated Retrieval System (TEKTRAN)

    This chapter, in a book to be published by the International Atomic Energy Agency/FAO Joint Division, provides detailed information on how to sense soil water tension with electrical resistance sensors. It provides insight into problems commonly encountered in using these sensors. Guidance on data r...

  2. Using Gypsum to Affect Soil Erosion Processes and Water Quality

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A driving force in soil erosion is the low electrolyte content of rain water. Various electrolyte sources have proven useful in serving as electrolyte sources such as phosphogypsum, lime and various salts, however, each has other potential problems. We performed a number of studies on low cost gypsu...

  3. Midwest soil and water conservation: Past, present and future

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil and water conservation was, is, and will continue to provide the foundation for sustainable resource management in the U.S. Corn and Soybean Belt. This chapter briefly reviews the natural resource foundation, settlement patterns, and development of conservation programs in the U.S. Midwest. The...

  4. Direct and surrogate measures of soil water content

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An expert group from five nations and three continents did comparative trials of soil water sensing methods under laboratory and field conditions at the behest of the joint division of the International Atomic Energy Agency and the United Nations Food and Agricultural Organization (FAO), resulting i...

  5. 30 year soil water trends along an elevation gradient

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many of the issues associated with ongoing global climate change hinge on the impacts of the documented physical changes (e.g., rising temperature) on the ecological systems that sustain life. A primary interface between these two is the soil, where water and nutrients are stored for plant consumpti...

  6. External exposure to radionuclides in air, water, and soil

    SciTech Connect

    Eckerman, K.F.; Ryman, J.C.

    1996-05-01

    Federal Guidance Report No. 12 tabulates dose coefficients for external exposure to photons and electrons emitted by radionuclides distributed in air, water, and soil. The dose coefficients are intended for use by Federal Agencies in calculating the dose equivalent to organs and tissues of the body.

  7. Effect of soil pollution on water for mixing of concrete

    NASA Astrophysics Data System (ADS)

    Muñoz, M. Cecilia Soto; Tapia Alvarez, Carolina; Decinti Weiss, Alejandra; Zamorano Vargas, Macarena; Corail Sanchez, Camila; Hurtado Nuñez, Camilo; Guzman Hermosilla, Matías; Pardo Fabregat, Francisco; Vidal, Manuel Miguel Jordan; Borras, Jaume Bech; Roca, Nuria

    2016-04-01

    ISO 12439, in addition to chemical and physical requirements, establishes maximum levels for harmful substances that may be present in the mixing water of concrete, when they come from natural sources from contaminated soils. These harmful substances considered in the ISO are sugars, phosphates (P2O5), nitrate (NO3-), lead (P2+) and zinc (Zn2+). As an alternative to the maximum values, ISO verifies the effect of these substances in water from contaminated soils. This measurement is made on the effect on the mechanical strength of the concrete (compression at 7 and 28 days) and the setting times (start and end setting). This paper presents the results obtained on samples of concrete made with smaller, similar and more content to the maximum levels set by ISO 12439 are presented. The results establish that in the case of nitrate, a substance present in many contaminated soils margins resistance variation or setting times allowed by ISO 12439 are not met. Finally, it is concluded that in case of presence of these pollutants should be performed strength tests and setting times before authorizing the use of water. Keywords: Harmful substances, contaminated soils, water pollution.

  8. An overview of soil water sensing technologies and problems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    An expert group from five nations and three continents did comparative trials of soil water sensing methods under laboratory and field conditions for the International Atomic Energy Agency. Important conclusions of the expert group include: 1) The field-calibrated neutron moisture meter (NMM) remain...

  9. Atrazine and Diuron partitioning within a soil-water-surfactant system

    NASA Astrophysics Data System (ADS)

    Wang, P.; Keller, A.

    2006-12-01

    The interaction between pesticide and soil and water is even more complex in the presence of surfactants. In this study, batch equilibrium was employed to study the sorption of surfactants and the partitioning behaviors of Atrazine and Diuron within a soil-water-surfactant system. Five soils and four surfactants (nonionic Triton- 100, cationic Benzalkonium Chloride (BC), anionic Linear Alkylbenzenesulfonate (LAS), and anionic Sodium Dodecyl Sulfate (SDS)) were used. All surfactant sorption isotherms exhibited an initial linear increase at low surfactant concentrations but reached an asymptotic value as the surfactant concentrations increased. Among the surfactants, BC had the highest sorption onto all soils, followed by Triton-100 and then by LAS and SDS, implying that the nature of the charge significantly influences surfactant sorption. Sorption of either Triton-100 or BC was highly correlated with soil Cation Exchange Capacity (CEC) while that of LAS and SDS was complicated by the presence of Ca2+ and Mg2+ in the aqueous phase and the CEC sites. Both LAS and SDS formed complexes with Ca2+ and Mg2+, resulting in a significant decrease in the detergency of the surfactants. At high surfactant concentrations and with micelles present in the aqueous phase, the micelles formed a more competitive partitioning site for the pesticides, resulting in less pesticide sorbed to the soil. At low Triton-100 and BC concentration, the sorption of the surfactants first resulted in less Atrazine sorption but more Diuron sorption, implying competition between the surfactants and Atrazine, which serves as an indirect evidence that there is a different sorption mechanism for Atrazine. Atrazine is a weak base and it protonates and becomes positively charged near particle surfaces where the pH is much lower than in the bulk solution. The protonated Atrazine may then be held on the CEC sites via electrostatic attraction. Triton-100, LAS and SDS sorbed on the soil showed similar

  10. Soil water availability and microsite mediate fungal and bacterial phospholipid fatty acid biomarker abundances in Mojave Desert soils exposed to elevated atmospheric CO2

    NASA Astrophysics Data System (ADS)

    Jin, V. L.; Schaeffer, S. M.; Ziegler, S. E.; Evans, R. D.

    2011-06-01

    Changes in the rates of nitrogen (N) cycling, microbial carbon (C) substrate use, and extracellular enzyme activities in a Mojave Desert ecosystem exposed to elevated atmospheric CO2 suggest shifts in the size and/or functional characteristics of microbial assemblages in two dominant soil microsites: plant interspaces and under the dominant shrub Larrea tridentata. We used ester-linked phospholipid fatty acid (PLFA) biomarkers as a proxy for microbial biomass to quantify spatial and temporal differences in soil microbial communities from February 2003 to May 2005. Further, we used the 13C signature of the fossil CO2 source for elevated CO2 plots to trace recent plant C inputs into soil organic matter (SOM) and broad microbial groups using δ13C (‰). Differences between individual δ13CPLFA and δ13CSOM for fungal biomarkers indicated active metabolism of newer C in elevated CO2 soils. Total PLFA-C was greater in shrub microsites compared to plant interspaces, and CO2 treatment differences within microsites increased under higher soil water availability. Total, fungal, and bacterial PLFA-C increased with decreasing soil volumetric water content (VWC) in both microsites, suggesting general adaptations to xeric desert conditions. Increases in fungal-to-bacterial PLFA-C ratio with decreasing VWC reflected functional group-specific responses to changing soil water availability. While temporal and spatial extremes in resource availability in desert ecosystems contribute to the difficulty in identifying common trends or mechanisms driving microbial responses in less extreme environments, we found that soil water availability and soil microsite interacted with elevated CO2 to shift fungal and bacterial biomarker abundances in Mojave Desert soils.

  11. The influence of vegetation on soil water repellency-markers and soil hydrophobicity.

    PubMed

    Mao, Jiefei; Nierop, Klaas G J; Rietkerk, Max; Sinninghe Damsté, Jaap S; Dekker, Stefan C

    2016-10-01

    Soil water repellency (SWR) markers are defined as hydrophobic compounds in soil causing SWR and are mainly derived from plants. Previous studies have shown the types and abundance of SWR-markers in soils. However, how these SWR-markers are exactly related to SWR and their origin is poorly understood. This study aims to understand the relationship between SWR-markers, vegetation type and cover and SWR for a simple sandy soil ecosystem, consisting of oaks with sedge and six grass species. All the soil (at different depth) and vegetation samples were collected in the field along a 6m transect, starting from an oak tree. Further along the transect grasses and sedges became more abundant. Free and ester-bound lipids from soils and plant leaves/roots were obtained using a sequential extraction method and identified by gas chromatography-mass spectrometry. Significant linear correlations were found between the main soil characteristics, such as total organic carbon content, and SWR. Single long-chain (>C20) SWR-markers derived from both plant leaf waxes and roots positively related to SWR. Both ester-bound ω-hydroxy fatty acids and C22 and C24 α,ω-dicarboxylic acids were predominantly present in the grass roots, but to a lesser extent in the roots of oak and sedge. These suberin-derived ω-hydroxy fatty acids and α,ω-dicarboxylic acids characteristic of roots could well predict the SWR. Additionally, the SWR predictors abundantly present in the soils matched well with high concentrations of the corresponding biomarkers in the dominant vegetation species that covered the soils. Our analyses demonstrated that grass roots influenced SWR more due to their more substantial contribution of organic matter to the topsoils than oak roots. This led to a stronger SWR of the soils covered with grass than those covered with oak vegetation. PMID:27236626

  12. Laboratory-field scaling of soil hydraulic properties: numerical validation based on soil water content measurements

    NASA Astrophysics Data System (ADS)

    Bonfante, Antonello; Coppola, Antonio; Basile, Angelo

    2010-05-01

    Hydraulic properties should be determined at the scale of the process modeled. The methods to hydraulically characterize a soil in situ remain extremely difficult to implement, needing measurements of water content and pressure head with adequate time-depth resolution. The authors recently proposed a method of scaling, physically based, that allows to obtain the field soil hydraulic parameters from the laboratory hydraulic characterization and the maximum water content in field. The procedure is based on the hypothesis that the field retention curve represents a secondary internal curves of the hysteresis loop. Assuming the sample as the REV (Representative Elementary Volume) of the soil, the drying and wetting laboratory curve represent the primaries curves. The procedure, recently validated on different soil samples, has been applied in four case studies (Cerese, Lodi, Scafati and Eboli). In each site, the soil water content was monitored at different depths along the soil profile with Time Domain Reflectometry technique (TDR)(years 2002-2003 for Cerese and Lodi, and years 2005-2006 for Scafati and Eboli). The SWAP hydrological simulation model, based on the Richard's equation, was applied to test in a composite field water flow processes the goodness of the proposed procedure. In particular, we compared water content measured in field and estimated by SWAP in two different runs, applying the same boundary conditions and crop parameterization, using hydraulic parameters obtained from (i) trials and errors calibration procedure and (ii) proposed scaling procedure. The agreement between observed and predicted values was expressed by the indexes RMSE (root mean squared error) and r (Pearson correlation). In the preliminary analysis, the statistical indexes has shown that the results obtained from scaling procedure are very similar or better of those obtained from calibration procedure. The main advantage arising from such scaling procedure rely on the significant

  13. Physiological responses of radiata pine roots to soil strength and soil water deficit.

    PubMed

    Zou, Chris; Sands, Roger; Sun, Osbert

    2000-11-01

    We investigated physiological responses of radiata pine (Pinus radiata D. Don) roots to soil strength and soil water deficit by measuring the osmotic potential (Psi(pi)) and yield turgor (Y) in the elongation zone of root segments of seedlings growing (i) in polyethylene glycol 4000-containing rooting solution of different water potentials (Psi(s)) and (ii) in soil of different soil strengths (Q) at the same soil matric potential (Psi(m)). Root elongation rate (Deltal/Deltat) decreased progressively with decreasing Psi(s) and was associated with decreased Psi(pi) and decreased turgor pressure (P). Osmotic adjustment occurred at Psi(s) < -0.2 MPa. Over a range in Psi(s) of -0.01 to -1.0 MPa, Psi(pi) fell 0.3 MPa whereas P fell 0.7 MPa. Mean Psi in the solution experiment was 0.37 MPa and did not differ significantly with Psi(s) (P = 0.10). Root elongation rate decreased exponentially as Q increased from 0 to 3.0 MPa, and was associated with an increase in P of 0.11 MPa as a consequence of Psi(pi) decreasing by the same amount. Mean Y in the soil experiment was 0.49 MPa and did not change significantly with Q (P = 0.87). PMID:12651497

  14. Electrical properties of water in clay and silty soils

    NASA Astrophysics Data System (ADS)

    Saarenketo, Timo

    1998-10-01

    In order to better understand ground penetrating radar (GPR) results obtained in road surveys and site investigations, the dielectric properties and electrical conductivity of four silt and clay soils were measured at different densities and moisture contents ranging from oven dry material to the plastic state. The real parts K' and imaginary parts K″ of the relative dielectric permittivity values of the soils were measured with an HP Surface Network Analyzer over a frequency range from 30 MHz to 3.0 GHz. A dielectric and electrical conductivity meter produced by Adek was also used. The results suggest that water in soils can be classified according to its electrical properties as: (1) an adsorption water layer, also known as the hygroscopic water layer; (2) a viscous or capillary water layer; and (3) free water. The measurements also showed that the adsorption water layer can be divided into inner and outer layers in accordance with the electrical double layer theory. The imaginary part of the dielectric value of the material is formed mainly in the outer layer and partly in the viscous (capillary) water layer, which also has two layers with differing electrical properties. The measurements also clearly showed that if the Cation Exchange Capacity (CEC) of a material is low, the water molecules are orderly arranged around the soil particles and the dielectric values of the bound water layers remain almost independent of frequency. If the CEC increases, the molecular structure of the bound water layers is disturbed and the water molecules more easily follow the changing AC field so that the dielectric value is higher. These materials are also highly dielectrically dispersive, especially at GPR frequencies below 400 MHz. Increasing CEC correlates well with increasing imaginary part of the adsorption water layer. Measured ohmic electrical conductivities were low at low moisture content and increased as the outer viscous water layer developed with higher moisture

  15. Understanding the Hydrology of Soil-Crop Interactions via a Wireless Sensor Network

    NASA Astrophysics Data System (ADS)

    Dunne, K. M.

    2009-12-01

    For centuries humans have relied upon our observations and perceptions of water content to make agricultural decisions in any given type of agriculture or geographic region. As agriculture has progressed, the area of land managed by each individual has increased exponentially, greatly decreasing a farmer’s ability to adequately address the nuances of any given portion of their property. This study focuses on the research possibilities provided with a wireless sensor network which gives detailed, hour by hour, data on water content, electrical conductivity (EC) and temperature at several depths. The research site is a very well characterized 37 hectare (ha) research farm containing several crop varieties under regular maintenance by Washington State University. A series of sites containing installments of five sensors at regular depths, between 30 and 150 cm, were deployed according to their unique locations. Current technology allows for research to be done which has the potential to revolutionize the way agriculture is managed. By providing a baseline of data, we can better understand water distribution within any given topography, water usage dynamics, water availability and a frame of reference to better understand how to optimally utilize soil based on a variety of weather patterns and interactions of soil type.

  16. Effects of corn stalk orientation and water content on passive microwave sensing of soil moisture

    NASA Technical Reports Server (NTRS)

    Oneill, P. E.; Blanchard, B. J.; Wang, J. R.; Gould, W. I.; Jackson, T. J.

    1984-01-01

    A field experiment was conducted utilizing artificial arrangements of plant components during the summer of 1982 to examine the effects of corn canopy structure and plant water content on microwave emission. Truck-mounted microwave radiometers at C (5 GHz) and L (1.4 GHz) band sensed vertically and horizontally polarized radiation concurrent with ground observations of soil moisture and vegetation parameters. Results indicate that the orientation of cut stalks and the distribution of their dielectric properties through the canopy layer can influence the microwave emission measured from a vegetation/soil scene. The magnitude of this effect varies with polarization and frequency and with the amount of water in the plant, disappearing at low levels of vegetation water content. Although many of the canopy structures and orientations studied in this experiment are somewhat artificial, they serve to improve understanding of microwave energy interactions within a vegetation canopy and to aid in the development of appropriate physically based vegetation models.

  17. Predicting subgrid variability of soil water content from basic soil information

    NASA Astrophysics Data System (ADS)

    Qu, W.; Bogena, H. R.; Huisman, J. A.; Vanderborght, J.; Schuh, M.; Priesack, E.; Vereecken, H.

    2015-02-01

    Knowledge of unresolved soil water content variability within model grid cells (i.e., subgrid variability) is important for accurate predictions of land-surface energy and hydrologic fluxes. Here we derived a closed-form expression to describe how soil water content variability depends on mean soil water content (σθ(<θ>)) using stochastic analysis of 1-D unsaturated gravitational flow based on the van Genuchten-Mualem (VGM) model. A sensitivity analysis showed that the n parameter strongly influenced both the shape and magnitude of the maximum of σθ(<θ>). The closed-form expression was used to predict σθ(<θ>) for eight data sets with varying soil texture using VGM parameters obtained from pedotransfer functions that rely on available soil information. Generally, there was good agreement between observed and predicted σθ(<θ>) despite the obvious simplifications that were used to derive the closed-form expression. Furthermore, the novel closed-form expression was successfully used to inversely estimate the variability of hydraulic properties from observed σθ(<θ>) data.

  18. Aerobic degradation and photolysis of tylosin in water and soil.

    PubMed

    Hu, Dingfei; Coats, Joel R

    2007-05-01

    Veterinary antibiotics enter the environment through the application of organic fertilizers to cropland. In this study, the aerobic degradation of tylosin, a widely used antibiotic in the production of livestock and poultry, was conducted in water and in soil in an effort to further investigate its environmental fate. Tylosin is a macrolide antibiotic, which consists of four factors (A, B, C, D). Water and soil were sampled at selected times and analyzed for tylosin and its degradation products by high-performance liquid chromatography (HPLC), with product identification confirmed by HPLC-mass spectrometry. Tylosin A is degraded with a half-life of 200 d in the light in water, and the total loss of tylosin A in the dark is 6% of the initial spiked amount during the experimental period. Tylosin C and D are relatively stable except in ultrapure water in the light. Slight increases of tylosin B after two months and formation of two photoreaction isomers of tylosin A were observed under exposure to light. However, tylosin probably would degrade faster if the experimental containers did not prevent ultraviolet transmission. In soil, tylosin A has a dissipation half-life of 7 d, and tylosin D is slightly more stable, with a dissipation half-life of 8 d in unsterilized and sterilized soil. Sorption and abiotic degradation are the major factors influencing the loss of tylosin in the environment, and no biotic degradation was observed at the test concentration either in pond water or in an agronomic soil, as determined by comparing dissipation profiles in sterilized and unsterilized conditions. PMID:17521133

  19. Organic carbon, water repellency and soil stability to slaking at aggregate and intra-aggregate scales

    NASA Astrophysics Data System (ADS)

    Jordán López, Antonio; García-Moreno, Jorge; Gordillo-Rivero, Ángel J.; Zavala, Lorena M.; Cerdà, Artemi; Alanís, Nancy; Jiménez-Compán, Elizabeth

    2015-04-01

    Water repellency (WR) is a property of some soils that inhibits or delays water infiltration between a few seconds and days or weeks. Inhibited or delayed infiltration contributes to ponding and increases runoff flow generation, often increasing soil erosion risk. In water-repellent soils, water infiltrates preferentially through cracks or macropores, causing irregular soil wetting patterns, the development of preferential flow paths and accelerated leaching of nut