Science.gov

Sample records for soil water interactions

  1. 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.

  2. 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.

  3. 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.

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

    E-print Network

    Goldsmith, Greg

    Oxygen isotope fractionation effects in soil water via interaction with cations (Mg, Ca, K, Na: Smectite Isotope hydrology Isotopic partitioning Soil-atmosphere interaction Pedogenic carbonate Vertisols s u m m a r y In isotope-enabled hydrology, soil and vadose zone sediments have been generally

  5. 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.; Šim?nek, 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.

  6. Low-field NMR relaxometry: a study of interactions of water with water-repellant soils.

    PubMed

    Todoruk, Tiona R; Litvina, Marina; Kantzas, Apostolos; Langford, Cooper H

    2003-07-01

    Petroleum-induced water repellency in soils is a problem that has been thought to develop randomly following contamination and then remediation of a site with petroleum. The emergence of the phenomenon can occur within months or years of original contamination and with seemingly no warning. Low-field NMR has been used to study these soils and, specifically, the processes of water uptake that occur in them. Critical aspects in the development of this phenomenon have been identified as well--specifically, a dependence on climatic events in the area and contamination levels that contribute are suggested. PMID:12875389

  7. Digital Soil Mapping: Interactions with

    E-print Network

    Grunwald, Sabine

    Chapter 21 Digital Soil Mapping: Interactions with and Applications for Hydropedology J.A. Thompson,1, * S. Roecker,2 S. Grunwald3 and P.R. Owens4 ABSTRACT Spatial information on soils, particularly hydrologic and hydromorphic soil properties, is used to understand and assess soil water retention, flooding

  8. 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.

  9. 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.

  10. Premelted liquid water in frozen soils and its interaction with bio-molecules

    NASA Astrophysics Data System (ADS)

    Hansen-Goos, H.; Wettlaufer, J. S.

    2011-12-01

    While liquid water in bulk is unstable on the surface of Mars, there is a possibility for the persistence of thin films of liquid water in the Martian regolith as a result of interfacial forces between the interstitial ice and the soil grains even below the bulk melting temperature. This is referred to as premelting. We present a calculation of the liquid fraction of frozen soils which takes into account premelting in combination with the effect of ionic impurities and the curvature induced freezing point depression (Gibbs-Thomson effect). We introduce a revised density functional theory which accurately treats a simple model for confined liquid water. We use the theory to study how biological matter (antifreeze proteins in particular) inside a narrow liquid cavity in ice interacts with the surrounding ice-water interface. Because in this case the interface is concave and hence the Gibbs-Thomson effect is antagonistic to the liquid phase, the protein-ice interaction is responsible for the persistence of liquid water.

  11. Characteristic of Soils and Behavior of Hexavalent Chromium in Soil-Water Interaction

    NASA Astrophysics Data System (ADS)

    Otomo, K.; Shikazono, N.

    2008-02-01

    Chromium exists in two forms mainly Cr3+ and Cr6+, and out of the two forms the later one is highly toxic and is documented as high priority pollutant. In order to investigate the extent and degree of heavy metal contamination in soils and sediments influenced by past mining activities, and to estimate the effects of the various soils on Cr speciation were examined. Experimental results on the kinesics of chromate reduction indicate that residual amounts of ferrous iron in weathering minerals can act as reductions for oxidized aqueous species. Chromium reduction by ferrous ion is used an oxidation-reduction reaction. The ferrous uses in particular that it become ferric after having reduced Cr6+ element in Cr3+. In this study, we examined relations with pH-Eh of the solution while examining the iron contents and removal rate in the soils of Cr6+.

  12. 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 and broadleaves). Furthermore, water uptake depth of beech was already influenced at this young development stage by interspecific interactions whereas no clear niche differentiation occurred for the other species. This finding does not preclude that plasticity-mediated responses to species interactions could increase as the plantation ages, leading to the coexistence of these species in adult forest stands.

  13. 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...

  14. 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...

  15. 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.

  16. Plant interactions with changes in coverage of biological soil crusts and water regime in Mu Us Sandland, China.

    PubMed

    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

  17. A two-layer soil moisture conceptual framework for exploring land surface-atmosphere interactions in water-limited ecosystem

    NASA Astrophysics Data System (ADS)

    Papuga, S. A.

    2014-12-01

    The exchange of water, energy, and carbon between the land surface and the atmosphere is largely influenced by vegetation. In turn, vegetation is strongly influenced by the partitioning of precipitation into evapotranspiration, soil moisture, and runoff. Ultimately, the hydrologic cycle exerts a strong control on the climate system. In fact, positive feedbacks between vegetation and the hydrologic cycle at small scales may have the ability to elicit non-linear responses with important large scale consequences. Therefore, capturing the synergies between hydrologic processes at different space and time scales is necessary for appropriately modeling the influence of vegetation and the hydrologic cycle on the climate system. Understanding the controls on land-atmosphere interactions and how they influence larger scale feedbacks will become increasingly important as climatic and other global changes continue to alter the water availability of our ecosystems. Water-limited ecosystems are especially sensitive to precipitation changes, and therefore insights concerning how their functioning responds to possible changes in precipitation patterns are important in understanding future climate scenarios. Over a decade of field work from my research group has highlighted the importance of deep soil moisture (from large storms) in the healthy functioning of water-limited ecosystems. This has led to the development of a two-layer soil moisture conceptual framework for exploring land surface-atmosphere interactions in water-limited ecosystems. Here I demonstrate how this framework can been used to link small scale processes investigated in field with large scale processes for water-limited ecosystems.

  18. 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...

  19. SOIL WATER HYSTERESIS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Since at least the early work of Haines, it has been recognized that volumetric soil water content, W, and hydraulic conductivity, K, are not singular functions of soil water pressure head, h, but rather exhibit considerable variation depending on the wetting and drying history of the soil. The non-...

  20. Environmental interactions of hydrazine fuels in soil/water systems. Final report, March 1985-September 1987

    SciTech Connect

    Street, J.; Johnston, C.; Mansell, R.; Bloom, S.

    1988-10-01

    Because the Air Force is the primary user of the rocket fuels, hydrazine (Hz), monomethylhydrazine (MMH), and 1,1-dimethylhydrazine (UDMH), it is responsible for the environmental implications associated with the transport, storage, and handling of these fuels. During handling, hydrazine fuels could inadvertently be released to the atmosphere and the surrounding aqueous and terrestrial environments. The studies are divided into the following five areas: aqueous and soil suspension studies, surface interaction studies, biological interaction studies, soil column studies, and soil transport modeling. The objective of this work is to determine the fate of hydrazine fuel released into an aqueous or soil environment. Aqueous degradation studies reveal that the extent of hydrazine degradation and the products formed are highly dependent upon several variables. Among these include the type of container used in the studies, the presence of certain metal ions, the ionic strength, the presence and type of pH buffer, the temperature, the presence of bacteria, and the amount of dissolved oxygen. Aqueous hydrazine degradation is particularly rapid in quartz vessels with copper ions ions and oxygen present. Degradation also increases with increasing ionic strength, pH buffer concentration, temperature, and bacteria content.

  1. Vegetation Dynamics and Soil Water Balance Interactions in a Water-limited Mediterranean Ecosystem on Sardinia Under Climate Change Scenarios

    NASA Astrophysics Data System (ADS)

    Montaldo, N.; Albertson, J. D.

    2009-12-01

    Mediterranean ecosystems are commonly heterogeneous savanna-like ecosystems, with contrasting plant functional types (PFT) competing for the water use. At the same time the structure and function of the vegetation regulates the exchange of mass, energy and momentum across the biosphere-atmosphere interface, influencing strongly the soil water budget. Mediterranean regions suffer water scarcity produced in part by natural (e.g., climate variations) influences. For instance, in the Flumendosa basin water reservoir system, which plays a primary role in the water supply for much of southern Sardinia, the average annual input from stream discharge in the latter part of the 20th century was less than half the historic average rate. The precipitation over the Flumendosa basin has decreased, but not at such a drastic rate as the discharge, suggesting a marked non-linear response of discharge to precipitation changes. Indeed, precipitation decreased in winter months, which are crucial for reservoirs recharge through runoff. The IPCC models predicts a further increase of drought in the Mediterranean region, increasing the uncertainty on the future of the water resources system of these regions. Hence, there is the need to investigate the role of the PFT vegetation dynamics on the soil water budget of these ecosystems in the context of the climate change, and predict hydrologic variables for climate change scenarios. The case study is in the Flumendosa basin. The site landscape is a mixture of Mediterranean patchy vegetation types: trees, including wild olives and cork oaks, different shrubs and herbaceous species. An extensive field campaign started in May 2003. Six years of data are available now. Land-surface fluxes and CO2 fluxes are estimated by an eddy correlation technique based micrometeorological tower. Soil moisture profiles were also continuously estimated using water content reflectometers and gravimetric method, and periodically leaf area index (LAI) PFTs are estimated. An ecohydrologic model is successfully tested to the case study. It couples a vegetation dynamic model (VDM), which computes the change in biomass over time for the PFTs, and a 3-component (bare soil, grass and woody vegetation) land surface model (LSM). Hydrometeorological change scenarios are then generated using a stochastic weather generator. It simulates hydrometeorological variables from historical time series (available from 1922 for this basin) altered by IPCC meteorological change predictions. The calibrated VDM-LSM predicts soil water balance and vegetation dynamics for the generated hydrometeorological scenarios. Results demonstrate that vegetation dynamics are strongly influenced by the variability of atmospheric forcing, with vegetation density changing significantly according to seasonal rainfall amount. At the same time the vegetation dynamics affect the soil water balance, and the runoff. Water resources predictions are worrying, with further decrease of runoff.

  2. 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.

  3. 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...

  4. 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...

  5. 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.

  6. 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...

  7. 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...

  8. 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.

  9. How Soil Organic Matter Composition Controls Hexachlorobenzene-Soil-Interactions: Adsorption Isotherms and Quantum Chemical Modelling

    E-print Network

    Ahmed, Ashour; Kühn, Oliver

    2013-01-01

    Hazardous persistent organic pollutants (POPs) interact in soil with the soil organic matter (SOM) but this interaction is insufficiently understood at the molecular level. We investigated the adsorption of hexachlorobenzene (HCB) on soil samples with systematically modified SOM. These samples included the original soil, the soil modified by adding a hot water extract (HWE) fraction (soil+3 HWE and soil+6 HWE), and the pyrolyzed soil. The SOM contents increased in the order pyrolyzed soil soil soil+3 HWE soil+6 HWE. For the latter three samples this order was also valid for the HCB adsorption. The pyrolyzed soil adsorbed more HCB than the other samples at low initial concentrations, but at higher concentrations the HCB adsorption became weaker than in the samples with HWE addition. This adsorption behaviour combined with the differences in the chemical composition between the soil samples suggested that alkylated aromatic, phenol, and lignin monomer compounds contributed most to the HC...

  10. Abiotic: water !, Soil, Sunlight, wind, air, weather,

    E-print Network

    Lawrence, Deborah

    ·Chemical ·Habitat ·Solar ·Water ·Nutrients ·Soil ·Geology ·Topography ·Atmosphere ·Climate ·Weather Climate/WeatherAbiotic: water !, Soil, Sunlight, wind, air, weather, climate Biotic: soil, organisms (flora Abiotic Components Air Water Sun Soil matrix Weather (Wind Temp) Climate geology Topography Nutrients

  11. 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.

  12. 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)

  13. 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. Most areas dealt with water table rise and gypsum aggradation from extremely sulfur- and calcium-rich water sources. Thus far we have evidence for Archaic to Classic aggradation (5000 BP to the present) and Classic period fields and canals as mostly piecemeal attempts by the Maya to adapt to these and other environmental changes. Wetland fields were mainly Classic period systems (1500 to 1000 BP) but varied from long- to short-lived. We found one example of a very Late/Terminal Classic (c. 1200 BP), preplanned reclamation project on a floodplain. One system had some reoccupation in the Postclassic about 800 BP. These findings and a recent discovery in Campeche, MX display the burgeoning evidence for intricate Maya connections with tropical wetland soils.

  14. 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

  15. WATER MOVEMENT IN FROZEN SOIL

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Water movement in freezing and thawing soils is dominated by two key features the steep drop in water potential that accompanies freezing (1.2 Mpa degrees C-1) and the sharp decrease in permeability of frozen versus unfrozen soils. The former is unavoidable and is expressed by the Clausius-Clapeyro...

  16. 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)

  17. 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...

  18. 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.

  19. 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.

  20. 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 of both soil and landscape. For example, the soil hydrological regime helps to contrast soils that accumulate more and less soluble constituents of the parent material.

  1. 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

  2. Can the soil properties affect the O and H isotopic composition of the soil water?

    NASA Astrophysics Data System (ADS)

    Hissler, Christophe; Legout, Arnaud; Barnich, François; Stoll, Martine; Klaus, Julian

    2014-05-01

    Understanding the dynamic of the soil water content is of primary importance since it is the vector of the matter exchange between soil and the other compartments of watersheds. The soil water is the phase, which is best suited to characterize the current dynamics in the soil and to provide information on mid- to long-term soil processes. Oxygen and Hydrogen stable isotopes of water are now currently used in hydrological studies to inform on water mixing and residence time in the soil and greatly contribute to improve our understanding of soil-water interactions. However, as of today the influence of biogeochemical processes on the spatio-temporal variability of ?18O and ?D of the soil solutions was rarely quantified. The Oxygen and Hydrogen exchanges between the soil water and the other soil compartments (living organisms, mineral, exchange capacity, organic matter) are still poorly studied and require deeper investigations. For instance, the weathering of silicate minerals produces O2+ in the soil solution, exchange capacity in acidic soils releases quantity of H+ in the soil solution and the degradation of the organic matter could also impact the Oxygen and Hydrogen isotope ratios of the soil water. But, are we able to quantify the contribution of these different processes to the Oxygen and Hydrogen isotopic composition of the soil water? In order to address this question, we set up a laboratory experiment with one liter soil columns of a 2mm-sieved and air-dried soil. The goal of the experiment was to observe the variation of the water Oxygen and Hydrogen isotopic composition at two different depths of these soil columns starting from the field capacity to the complete drying of the soil. Water with a known isotopic composition was used to saturate the soil matrix and we observed the deviation from this initial composition at the different depths during the drying of the soil using ceramic cup lysimeters. Three steps of saturation were applied during the entire experiment. The deviation from the initial isotopic composition becomes significant in the soil waters at the different depths after two weeks of experiment and increases until reaching a threshold at the end of the experiment. After each new saturation step, the isotopic composition of the input water is not conserved anymore in the collected solutions and increases instantaneously. This observation may illustrate the potential for the soil bio-physico-chemical activities to contribute to the O and H composition of the soil water. These preliminary results allowed us to evaluate the contribution of the evaporation process in the Oxygen and Hydrogen isotopic fractionation and to deduce the potential contribution of soil compartments.

  3. 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...

  4. Field Devices for Monitoring Soil Water Content

    E-print Network

    . Professor, Soil and Water Science Dept. Univ. of Florida for The Irrigation Water Management Program Team Devices for Monitoring Soil Water Content" by Rafael Muñoz-Carpena, Univ. of Florida, Bulletin 343SR-IWM-2 Field Devices for Monitoring Soil Water Content by Rafael Muñoz-Carpena1 , Sanjay Shukla1

  5. Analytical solution for soil water redistribution during evaporation process.

    PubMed

    Teng, Jidong; Yasufuku, Noriyuki; Liu, Qiang; Liu, Shiyu

    2013-01-01

    Simulating the dynamics of soil water content and modeling soil water evaporation are critical for many environmental and agricultural strategies. The present study aims to develop an analytical solution to simulate soil water redistribution during the evaporation process. This analytical solution was derived utilizing an exponential function to describe the relation of hydraulic conductivity and water content on pressure head. The solution was obtained based on the initial condition of saturation and an exponential function to model the change of surface water content. Also, the evaporation experiments were conducted under a climate control apparatus to validate the theoretical development. Comparisons between the proposed analytical solution and experimental result are presented from the aspects of soil water redistribution, evaporative rate and cumulative evaporation. Their good agreement indicates that this analytical solution provides a reliable way to investigate the interaction of evaporation and soil water profile. PMID:24355839

  6. Nature of water molecular bridging of the soil organic matter

    NASA Astrophysics Data System (ADS)

    Kucerik, Jiri; Siewert, Christian; Quilesfogel-Esparza, Claudia; Schaumann, Gabriele E.

    2014-05-01

    Soil is a complex anisotropic and porous system consisting of both inorganic and organic parts, air and water, inhabited and successively transformed by soil biota. Processes of soil formation are influenced by several factors. Among the most important factors belong the inorganic and organic input materials, which are mixed and transformed during soil formation. As a result, specific interactions and interrelationships develop between soil compartments. Although, they are important for soil function and its stability, they are still not well understood. This work deals with water molecule bridges (WaMB), as one of those interactions, and their relation to organic matter functioning. Differential scanning calorimetry (DSC) belongs to the family of methods of thermal analysis, i.e. it uses heat as a probe of the sample's nature. In soil science, the application of this common method is quite rare. In our previous works, DSC revealed a physical stabilization of organic matter segments in soils by development of WaMB. Results suggested the development of those bridges at ambient temperature accompanied with condensation of water into small nanodroplets. In another work, we found out that water, evaporating at the same temperature as WaMB transition occurs, correlates with the activity of soil microorganisms measured via CO2respiration. In this work, the enthalpy and kinetic parameters of water evaporation are studied in two kinds of soil: in clay-rich chernozem soils originating from Siberia and a histosol collected in Germany. We discuss the details of application of DSC, experimental arrangement and advantages and disadvantages of this approach. It is shown that enthalpy of evaporation can be used for understanding the nature of water binding in soils with well-developed aggregates. In contrast, the evaporation of water from histosol, without a typical soil texture, is more complicated because of diffusion processes. Further, the connection between enthalpy of evaporation and soil microbiological activity is discussed.

  7. 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 measurements of soil water potentials, water contents, and root distributions. The results showed that this modelling approach reproduced soil water dynamics well in the different plots and treatments. Root water uptake reduced when the effective soil water potential decreased to around -70 to -100 kPa in the root zone. Couvreur, V., Vanderborght, J., and Javaux, M.: A simple three dimensional macroscopic root water uptake model based on the hydraulic architecture approach, Hydrol. Earth Syst. Sci., 16, 2957-2971, doi:10.5194/hess-16-2957-2012, 2012.

  8. Water Infiltration in Layered Soils with Air Entrapment: Modified Green-Ampt

    E-print Network

    Zhan, Hongbin

    from the soil water retention curve equation. In MGAM, the actual water content and hydraulic subject headings: Infiltration; Layered soils; Air-water interactions; Irrigation; Hydrologic modelsWater Infiltration in Layered Soils with Air Entrapment: Modified Green-Ampt Model and Experimental

  9. 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...

  10. Transpiration as a Function of Soil Temperature and Soil Water Stress

    PubMed Central

    Cox, L. M.; Boersma, L.

    1967-01-01

    An apparatus was developed for the measurement of transpiration rates of Trifolium repens. The transpiration rates were measured under controlled conditions of soil water stress and soil temperature. Other environmental parameters such as air temperature, relative humidity, light intensity and air speed were held constant. Diffusive resistances were calculated and stomatal aperture changes were recorded for all treatment combinations. A significant interaction between soil water stress and soil temperature was observed for stomatal closures. Stomatal closure was observed even in the so-called wet range of soil water stress. An increase in mesophyll resistance or incipient drying was observed for several treatment combinations. The mesophyll resistance was shown to increase as soil water stress increased. Images PMID:16656536

  11. 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.

  12. University of Florida Soil and Water Science Department

    E-print Network

    Ma, Lena

    University of Florida Soil and Water Science Department Erosion Impacts on Soil and Environmental.........................................................................................................3 Soil erosion-Highlands: Its soils and land resources...........................................5 3. Vertisols

  13. 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...

  14. 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.

  15. The plant-soil interface: understanding dynamic interactions in the context of environmental change

    E-print Network

    The plant-soil interface: understanding dynamic interactions in the context of environmental change Department of Soil, Water, and Climate, University of Minnesota, 6 Medical Department, Brookhaven National and mitigate the negative impacts of climate change. #12;

  16. Soil Dynamics and Earthquake Engineering 26 (2006) 694707 Plain strain soilstructure interaction model for a building supported by

    E-print Network

    Southern California, University of

    2006-01-01

    Soil Dynamics and Earthquake Engineering 26 (2006) 694­707 Plain strain soil­structure interaction, CA 90089-2531, USA Accepted 3 January 2006 Abstract A simple theoretical model for soil­structure interaction in water saturated poroelastic soils is presented, developed to explore if the apparent building­foundation­soil

  17. 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.

  18. 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.

  19. 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 (...

  20. 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.

  1. The influence of water, land, energy and soil-nutrient resource interactions on the food system in Uganda

    E-print Network

    Mukuve, Feriha Mugisha; Fenner, Richard A.

    2014-12-31

    , p.11). 32.6% of the treated water is lost as non-revenue water comprising of 0.011 km3 of leaks & bursts, emergency use for firefighting (0.0053 km3) and illegal consumption (MoWE, 2012, p.89; NWSC, 2012, p.11). Seventy per cent and ninety per... components and the different outcomes of Food Security. The study scope is indicated in the dashed boundary. Figure 1: Food System and WLEN Nexus Interconnections; Scope of the study. 6 1...

  2. Summary Soil respiration is controlled by soil temperature, soil water, fine roots, microbial activity, and soil physical and

    E-print Network

    Cohen, Ronald C.

    Summary Soil respiration is controlled by soil temperature, soil water, fine roots, microbial content, and root density and activity, and thus changes soil respiration. We measured soil respiration (after thinning). Thinning increased the spatial homogeneity of soil temperature and respiration. We

  3. Comparison of soil water potential sensors

    NASA Astrophysics Data System (ADS)

    Degre, Aurore; van der Ploeg, Martine; Caldwell, Todd; Gooren, Harm

    2015-04-01

    Temporal and spatial monitoring of soil water potential and soil water content are necessary for quantifying water flow in the domains of hydrology, soil science and crop production as knowledge of the soil water retention curve is important for solving Richards' equation. Numerous measurement techniques exist nowadays that use various physical properties of the soil-water complex to record changes in soil water content or soil water potential. Laboratory techniques are very useful to determine static properties of the soil water retention curve, and have been used to show the impacts of hysteresis. Yet, other spatiotemporal dynamics resulting from for example growing root systems, biological activity, periodic tillage and their impact on the soil structure cannot satisfactory be quantified in static setups in the laboratory. ). To be able to quantify the influence of soil heterogeneity, and spatiotemporal dynamics on the soil water retention curve, an in situ approach combining soil moisture and soil water potential measurements could provide useful data. Such an in situ approach would require sensors that can measure a representative part of the soil water retention curve. The volumetric soil water content is often measured using time domain reflectometry, and has gained widespread acceptance as a standard electronic means of volumetric water content measurement. To measure the soil water potential, water filled tensiometers are used in most studies. Unfortunately, their range remains limited due to cavitation. Recently, several new sensors for use under in situ conditions have been proposed to cover a wider range of pressure head: Polymer tensiometers, MPS (Decagon) and pF-meter (ecoTech). In this study, we present the principles behind each measurement technique. Then we present the results of a fully controlled experiment where we compared two MPS sensors, two pF-meter sensors and two POT sensors in the same repacked soil. It allows us to discuss advantages and disadvantages of each method. A CS616 volumetric water content probe was installed to compare in situ measured retention curves with laboratory measured retention curves for each method.

  4. 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 ...

  5. SSI (soil-structure interactions) and structural benchmarks

    SciTech Connect

    Philippacopoulos, A.J.; Miller, C.A.; Costantino, C.J.; Graves, H.

    1986-01-01

    This paper presents the latest results of the ongoing program entitled, ''Standard Problems for Structural Computer Codes'', currently being worked on at BNL for the USNRC, Office of Nuclear Regulatory Research. During FY 1986, efforts were focussed on three tasks, namely, (1) an investigation of ground water effects on the response of Category I structures, (2) the Soil-Structure Interaction Workshop and (3) studies on structural benchmarks associated with Category I structures. The objective of the studies on ground water effects is to verify the applicability and the limitations of the SSI methods currently used by the industry in performing seismic evaluations of nuclear plants which are located at sites with high water tables. In a previous study by BNL (NUREG/CR-4588), it has been concluded that the pore water can influence significantly the soil-structure interaction process. This result, however, is based on the assumption of fully saturated soil profiles. Consequently, the work was further extended to include cases associated with variable water table depths. In this paper, results related to ''cut-off'' depths beyond which the pore water effects can be ignored in seismic calculations, are addressed. Comprehensive numerical data are given for soil configurations typical to those encountered in nuclear plant sites. These data were generated by using a modified version of the SLAM code which is capable of handling problems related to the dynamic response of saturated soils.

  6. Water Retention of Extremophiles and Martian Soil Simulants Under Close to Martian Environmental Conditions

    NASA Astrophysics Data System (ADS)

    Jänchen, J.; Bauermeister, A.; Feyh, N.; deVera, J.-P.

    2012-05-01

    We report data about interaction of moisture with soil simulants and extremophiles under Martian environmental conditions contributing on atmosphere/surface modelling and on effects determining the water inventory of the upper soil layer of Mars.

  7. Stochastic analysis of soil-structure interaction 

    E-print Network

    Chan, Charles Cheuk Lap

    1994-01-01

    This study investigates the effect of soil structure interaction on the response of a building subjected to an earthquake motion. Spectra consisting of the auto and cross spectral densities of three components of free-field ...

  8. SOIL, WATER, AND CLIMATE MS DEFENSE SEMINAR

    E-print Network

    Minnesota, University of

    studies on medium to high P soils, alfalfa, corn, and soybean yields were similar with TMA and fertilizer soil, P availability with TMA was significantly lower than with commercial P fertilizer and resultedSOIL, WATER, AND CLIMATE MS DEFENSE SEMINAR Turkey Manure Incinerator Ash a P and K Source for Crop

  9. Plant Water Uptake in Drying Soils1

    PubMed Central

    Lobet, Guillaume; Couvreur, Valentin; Meunier, Félicien; Javaux, Mathieu; Draye, Xavier

    2014-01-01

    Over the last decade, investigations on root water uptake have evolved toward a deeper integration of the soil and roots compartment properties, with the goal of improving our understanding of water acquisition from drying soils. This evolution parallels the increasing attention of agronomists to suboptimal crop production environments. Recent results have led to the description of root system architectures that might contribute to deep-water extraction or to water-saving strategies. In addition, the manipulation of root hydraulic properties would provide further opportunities to improve water uptake. However, modeling studies highlight the role of soil hydraulics in the control of water uptake in drying soil and call for integrative soil-plant system approaches. PMID:24515834

  10. 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

  11. Fractal processes in soil water retention

    SciTech Connect

    Tyler, S.W.; Wheatcraft, S.W. )

    1990-05-01

    The authors propose a physical conceptual model for soil texture and pore structure that is based on the concept of fractal geometry. The motivation for a fractal model of soil texture is that some particle size distributions in granular soils have already been shown to display self-similar scaling that is typical of fractal objects. Hence it is reasonable to expect that pore size distributions may also display fractal scaling properties. The paradigm that they used for the soil pore size distribution is the Sierpinski carpet, which is a fractal that contains self similar holes (or pores) over a wide range of scales. The authors evaluate the water retention properties of regular and random Sierpinski carpets and relate these properties directly to the Brooks and Corey (or Campbell) empirical water retention model. They relate the water retention curves directly to the fractal dimension of the Sierpinski carpet and show that the fractal dimension strongly controls the water retention properties of the Sierpinski carpet soil. Higher fractal dimensions are shown to mimic clay-type soils, with very slow dewatering characteristics and relatively low fractal dimensions are shown to mimic a sandy soil with relatively rapid dewatering characteristics. Their fractal model of soil water retention removes the empirical fitting parameters from the soil water retention models and provides paramters which are intrinsic to the nature of the fractal porous structure. The relative permeability functions of Burdine and Mualem are also shown to be fractal directly from fractal water retention results.

  12. 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.

  13. 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.

  14. Interactive computer code for dynamic and soil structure interaction analysis

    SciTech Connect

    Mulliken, J.S.

    1995-12-01

    A new interactive computer code is presented in this paper for dynamic and soil-structure interaction (SSI) analyses. The computer program FETA (Finite Element Transient Analysis) is a self contained interactive graphics environment for IBM-PC`s that is used for the development of structural and soil models as well as post-processing dynamic analysis output. Full 3-D isometric views of the soil-structure system, animation of displacements, frequency and time domain responses at nodes, and response spectra are all graphically available simply by pointing and clicking with a mouse. FETA`s finite element solver performs 2-D and 3-D frequency and time domain soil-structure interaction analyses. The solver can be directly accessed from the graphical interface on a PC, or run on a number of other computer platforms.

  15. 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.

  16. 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)…

  17. 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.

  18. Water wave interactions Walter Craig

    E-print Network

    Thomann, Laurent

    Water wave interactions Walter Craig Department of Mathematics & Statistics ´EquationsMaster University) Water wave interactions 25 janvier 2011 1 / 34 #12;Joint work with: Philippe Guyenne University, Killam Research Fellows Program, Fields Institute Walter Craig (McMaster University) Water wave

  19. 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 content increase and be less than that. Sorption interactions of herbicides with soils demonstrate a strong hysteresis (which is not expected to be related to a biodegradation). The data suggests that the OMWW - soil interaction seems to change the shape of the apparent sorption isotherms of organic sorbates, and, possibly, their sorption mechanisms: from a Langmuir-like sorption isotherm (describing the adsorptive interactions with a saturation of sorption sites) in the native soils to the sigmoidal or linear isotherms (expected for a partitioning into the bulk OM phases and their swelling) in the OMWW-amended soils. These results may have a significant impact on multiple agricultural and hydrological aspects, e.g., such as the application rate of herbicides in the field, and their possible release and the long term effect on groundwater. The authors acknowledge the support from the OLIVEOIL project (SCHA849/13) funded by DFG.

  20. 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...

  1. Water in the Soil http://www.alison-burke.com/jpgs-large/lifesciences/soil_waterflow.jpg

    E-print Network

    Nowak, Robert S.

    Recap Recap Recap #12;Water in the Soil http://www.alison-burke.com/jpgs-large/lifesciences/soil_waterflow.jpg Soil water potential More negative #12;Less water requires more force As the soil water content decreases, plants need to excerpt more pressure to take water Photosynthesis and Water A decreases

  2. 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.

  3. 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 K?ava 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 water content of the upper 1 meter soil layer up to 53 mm at the end of vegetation period in comparison to the afforested area. Finally, soil water content profiles of stony soil differ from homogeneous ones and contain less water comparing to soil without stones.

  4. 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 Darcy's law is no longer valid) was at a relatively high degree of saturation of 0.8. This finding is important as many water flow analyses in the literature assume that Darcy's law is valid over a much wider range of degrees of saturation, an error that potentially may lead to overestimates of water flow in unsaturated soil layers.

  5. ReproducedfromSoilScienceSocietyofAmericaJournal.PublishedbySoilScienceSocietyofAmerica.Allcopyrightsreserved. Post-fire Soil Water Repellency: Persistence and Soil Moisture Thresholds

    E-print Network

    MacDonald, Lee

    ScienceSocietyofAmerica.Allcopyrightsreserved. Post-fire Soil Water Repellency: Persistence and Soil Moisture Thresholds Lee H. MacDonald* and Edward on the persistence of soil water repellency and the soil moisture threshold at which water were the primary over time and identify on soil water repellency because of the large variability soil moisture

  6. 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.

  7. 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 ...

  8. 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...

  9. 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...

  10. 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 update data sets on soil moisture retention, especially during long periods of drought. As such, description of the soil cover water balance will be more elaborate as the soil moisture profile will be described in terms of temporal and spatial variability. Moreover, this field data set can lend support on the evaluation of the potential use of mine wastes as cover materials with respect to their hydrologic and geochemical properties.

  11. Stable or unstable wetting fronts in water repellent soils effect of antecedent soil moisture content

    E-print Network

    Stable or unstable wetting fronts in water repellent soils ± effect of antecedent soil moisture repellent soils are known to inhibit water in®ltration, ultimately forcing water to ¯ow via preferential paths through the vadose zone. To study water ¯ow and transport in a water repellent sandy soil

  12. 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.

  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. Impact of Soil Type and Compaction Conditions on Soil Water Characteristic

    E-print Network

    Yu, Sheng-Tao

    Impact of Soil Type and Compaction Conditions on Soil Water Characteristic C. J. Miller, M.ASCE1 the variation of water content and pore water suction for compacted clayey soils. The soils had varying amounts of clay fraction with plasticities ranging from low to high plasticity. The unsaturated soil behavior

  15. ESTIMATION OF GROUND WATER RECHARGE USING SOIL MOISTURE BALANCE APPROACH

    E-print Network

    Kumar, C.P.

    ESTIMATION OF GROUND WATER RECHARGE USING SOIL MOISTURE BALANCE APPROACH C. P. Kumar* ABSTRACT is the principal means for replenishment of moisture in the soil water system and recharge to ground water at the upper boundary, the antecedent soil moisture conditions, the water table depth and the soil type

  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. 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.

  18. 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 export with 95% less nematodes exported, compared with the control treatment. We observed wholesale non-selective transport of all nematode trophic groups present in the soil. The findings of this experiment are twofold. Firstly, we demonstrate that soil organisms are transported by erosion processes and confirm that tramlines are key hydrological pathways. Secondly, we highlight practical on-farm solutions that have potential to decrease soil organism losses. These results provide important baseline information to improve our understanding of soil erosion impacts to the wider soil ecosystem. The results help to inform soil and water conservation measures for sustainable agriculture.

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

    E-print Network

    2011-01-01

    Keywords: Boreal Carbon Climate change Water movement WaterWater and heat transport in boreal soils: Implications for soil response to climateclimate. Additionally, the convection of latent heat by water

  20. 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.

  1. 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.

  2. 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.

  3. Modeling, estimation, and control of robot-soil interactions

    E-print Network

    Hong, Won, 1971-

    2001-01-01

    This thesis presents the development of hardware, theory, and experimental methods to enable a robotic manipulator arm to interact with soils and estimate soil properties from interaction forces. Unlike the majority of ...

  4. Characterization of Soil Water Content Variability and Soil Texture using GPR Groundwave Techniques

    E-print Network

    Hubbard, Susan

    texture and water content were calculated, and co-kriging of water content estimates and soil textureCharacterization of Soil Water Content Variability and Soil Texture using GPR Groundwave Techniques@ce.berkeley.edu ABSTRACT Accurate characterization of near-surface soil water content is vital for guiding agricultural

  5. Interactive effects of plant species diversity and elevated CO2 on soil biota and nutrient cycling.

    PubMed

    Niklaus, P A; Alphei, J; Kampichler, C; Kandeler, E; Körner, C; Tscherko, D; Wohlfender, M

    2007-12-01

    Terrestrial ecosystems consist of mutually dependent producer and decomposer subsystems, but not much is known on how their interactions are modified by plant diversity and elevated atmospheric CO2 concentrations. Factorially manipulating grassland plant species diversity and atmospheric CO2 concentrations for five years, we tested whether high diversity or elevated CO2 sustain larger or more active soil communities, affect soil aggregation, water dynamics, or nutrient cycling, and whether plant diversity and elevated CO2 interact. Nitrogen (N) and phosphorus (P) pools, symbiotic N2 fixation, plant litter quality, soil moisture, soil physical structure, soil nematode, collembola and acari communities, soil microbial biomass and microflora community structure (phospholipid fatty acid [PLFA] profiles), soil enzyme activities, and rates of C fluxes to soils were measured. No increases in soil C fluxes or the biomass, number, or activity of soil organisms were detected at high plant diversity; soil H2O and aggregation remained unaltered. Elevated CO2 affected the ecosystem primarily by improving plant and soil water status by reducing leaf conductance, whereas changes in C cycling appeared to be of subordinate importance. Slowed-down soil drying cycles resulted in lower soil aggregation under elevated CO2. Collembola benefited from extra soil moisture under elevated CO2, whereas other faunal groups did not respond. Diversity effects and interactions with elevated CO2 may have been absent because soil responses were mainly driven by community-level processes such as rates of organic C input and water use; these drivers were not changed by plant diversity manipulations, possibly because our species diversity gradient did not extend below five species and because functional type composition remained unaltered. Our findings demonstrate that global change can affect soil aggregation, and we advocate that soil aggregation should be considered as a dynamic property that may respond to environmental changes and feed back on other ecosystem functions. PMID:18229849

  6. 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...

  7. Soil water partitioning contributes to species coexistence in tallgrass prairie

    E-print Network

    Nippert, Jesse

    differences in the source of water-use using the isotopic signature of xylem water, volumetric soil waterSoil water partitioning contributes to species coexistence in tallgrass prairie Jesse B. Nippert (0Á25 cm), but species differences exist in reliance on soil water at varying depths

  8. 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 ...

  9. Temperature and frequency dependent time-domain reflectometry water content calibrations in fine-textured soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    High frequency dielectric measurements of soil water content can exhibit temperature sensitivities inconsistent with that expected for bulk water. These sensitivities are significant in fine-textured soils and controlled by the interaction among the temperature dependencies of the static permittivit...

  10. Evaluating climatic and soil water controls on evapotranspiration at two Amazonian rainforest sites

    E-print Network

    Evaluating climatic and soil water controls on evapotranspiration at two Amazonian rainforest sites in revised form 28 November 2007 Accepted 3 December 2007 Keywords: Amazon Soil moisture Hydraulic­atmosphere interaction is the Amazon basin, which plays a key role in the global cycles of carbon, water and energy

  11. 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...

  12. Water conductivity of arctic zone soils (Spitsbergen)

    NASA Astrophysics Data System (ADS)

    Witkowska-Walczak, Barbara; S?awi?ski, Cezary; Bartmi?ski, Piotr; Melke, Jerzy; Cymerman, Jacek

    2014-10-01

    The water conductivity of arctic zone soils derived in different micro-relief forms was determined. The greatest water conductivity at the 0-5 cm depth for the higher values of water potentials (> -7 kJ m-3) was shown by tundra polygons (Brunic-Turbic Cryosol, Arenic) - 904-0.09 cm day-1, whereas the lowest were exhibited by Turbic Cryosols - 95-0.05 cm day-1. Between -16 and -100 kJ m-3, the water conductivity for tundra polygons rapidly decreased to 0.0001 cm day-1, whereas their decrease for the other forms was much lower and in consequence the values were 0.007, 0.04, and 0.01 cm day-1 for the mud boils (Turbic Cryosol (Siltic, Skeletic)), cell forms (Turbic Cryosol (Siltic, Skeletic)), and sorted circles (Turbic Cryosol (Skeletic)), respectively. In the 10-15 cm layer, the shape of water conductivity curves for the higher values of water potentials is nearly the same as for the upper layer. Similarly, the water conductivity is the highest - 0.2 cm day-1 for tundra polygons. For the lower water potentials, the differences in water conductivity increase to the decrease of soil water potential. At the lowest potential the water conductivity is the highest for sorted circles - 0.02 cm day-1 and the lowest in tundra polygons - 0.00002 cm day-1.

  13. 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

    The major role played by the hydrology in controlling biogeochemical fluxes at various scales has been highlighted in several studies (e.g. Van Gaelen et al., 2014; Jiang et al., 2010). Numerous studies have highlighted different factors controlling water fluxes at the hillslope or catchment scale, such as physico-chemical soil characteristics and structure (Uhlenbrook et al., 2008) and soil thickness (Buttle et al., 2004). Given the potential important impact of land use changes on water fluxes (Özturk et al., 2013), it is surprising that relatively few studies investigated the impacts of those changes. This does not only imply that the consequences of land use change on hydrological and biogeochemical pathways and fluxes are still difficult to predict but also that we lack critical information on how such changes may feed back to soil processes. Therefore, it remains impossible to assess to what extent land use conversions may affect biogeochemical processes in soils and/or soil production through weathering. The overall objective of this research project is therefore to investigate how land use change affects water and biogeochemical fluxes and how these changes may, on their turn, affect soil and landscape development on the long term. In order to achieve this objective it is necessary to not only assess the effect of land use on fluxes leaving the catchment, but also on how land use change affects water pathways and water chemistry within the catchment. This requires the combined use of a wide range of classical and novel techniques. Two catchments with contrasting land use (agriculture vs. natural forest) were selected in a subtropical region in the south of Brazil. Soil sampling, stream discharge monitoring and sampling, pore water sampling, groundwater monitoring and sampling, and geophysical techniques (Time Domain Reflectometry and Electro Magnetic Induction) are combined to yield information on water and solute movement at the plot, slope and catchment 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.

  14. 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 ...

  15. Modeling soil-root interactions: Effect of rhizosphere salinity on transpiration reduction

    E-print Network

    Cirpka, Olaf Arie

    Modeling soil-root interactions: Effect of rhizosphere salinity on transpiration reduction Natalie-dimensional water flow and solute transport in the soil [1]. We used the model to investigate transpiration = -K xAx Hxylem lseg + z lseg Boundary conditions: Transpiration rate or pressure head at root collar

  16. 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.

  17. 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…

  18. Mathematics: Food, Soil, Water, Air, Free Speech

    E-print Network

    Russo, Bernard

    Chapter 5 Mathematics: Food, Soil, Water, Air, Free Speech As I write there are reports of yet another outbreak of food borne disease with some hospitalizations and deaths. This time it is Escherichia.cdc.gov in 1999, more than 75 million Americans get sick each year from food, of which about 325,000 require

  19. 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...

  20. Estimating in situ soil-water retention and field water capacity measurements in two contrasting soil textures

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Knowledge of the in-situ field water capacity (FWC) and the soil-water retention curve for soils is important for effective irrigation management and scheduling. The primary objective of this study was to estimate the in-situ FWC from the soil-water retention curve developed from water content, ' an...

  1. A Scalable Lagrangian Approach to Model Soil Water Dynamics in Structured Soils

    NASA Astrophysics Data System (ADS)

    Jackisch, Conrad; Zehe, Erwin

    2013-04-01

    Many experiments and studies have shown, that soil water movement follows preferential paths - across scales, across flow domains and across conditions. At the same time different flow domains are widely noticed in several model abstractions (stochastic stream tubes, double domain approaches, explicit structure definitions, and others). Both aspects cumulate in the question of interaction of domains - again across scales and conditions. We propose a Lagrangian approach, treating water directly as particles, in an abstract unified representative macropore-matrix-domain. The model is driven exclusively by observable parameters. The approach is fully scalable from a single soil column to the lower mesoscale. The domain is a 1.5D representation of a macropore and adjoined matrix. Depth is explicitly resolved as first dimension. Relative distance from the macropore-edge forms the lateral dimension based on observations of macropore density and diameter distribution over depth. Soil matrix characteristics (data from standard physical soil analysis) are respected for diffusive water particle movement dissipating pressure gradients. Fluid properties and macropore configuration (data from sprinkler experiments) are treated explicitly as reference of advective transport. Through this we open up a link of porescale physics to preferential macroscale fingerprints without effective parameterisation or mixing assumptions. Moreover, solute transport, energy balance aspects and lateral heterogeneity in soil moisture distribution are intrinsically captured.

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

    SciTech Connect

    Marsh, H.E.

    1983-08-01

    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, brinesoil interactions, sealants, and others. With the Salton Sea solar pond investigation as an example, some methods under development are described.

  3. 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...

  4. SOIL, WATER, AND CLIMATE PhD DEFENSE SEMINAR ______ _

    E-print Network

    Minnesota, University of

    ____________________________________________________________________ SOIL, WATER, AND CLIMATE Ph² in the Minnesota River Basin and generates significant sediment and chemical pollution. The objective of my study. The Soil and Water Assessment Tool (SWAT) model was calibrated and validated against observed data from

  5. 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 ...

  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. 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...

  8. Use of remote sensing for upscaling soil water models

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water content controls, to a large degree, processes of plant growth, groundwater recharge and overland flow that are critical for the management of rangelands in the western USA. Direct measurement of soil water is constrained to very small scales and models that describe soil water content h...

  9. Indicators for Soil and Water Conservation on Rangelands INTRODUCTION

    E-print Network

    Wyoming, University of

    soils in terrestrial systems and water bodies in aquatic systems to support energy capture throughChapter II - 1 - CHAPTER II Indicators for Soil and Water Conservation on Rangelands INTRODUCTION Soil and water provide the media for ecosystem processes. Primary production of ecosystems requires

  10. Soil Water Sensing-Focus on Variable Rate Irrigation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Irrigation scheduling using soil water sensors is an exercise in maintaining the water content of the crop root zone soil above a lower limit defined by the management allowed depletion (MAD) for that soil and crop, but not so wet that too much water is lost to deep percolation. The management allow...

  11. Near-stream soil water groundwater coupling in the headwaters of the Afon Hafren, Wales: Implications for surface water quality

    NASA Astrophysics Data System (ADS)

    Haria, Atul H.; Shand, Paul

    2006-12-01

    SummaryHard-rock acid headwater catchments typically exhibit a rapid streamflow response and concomitant rapid mobilisation of soil-derived solutes, such as aluminium, into the aquatic environment during storm events. The rapid stream responses are paradoxically associated with pre-event water dominating the storm hydrograph, however the sources and mechanisms by which 'old' water enters the stream channel and interacts with the soil horizons are still poorly understood. To investigate these processes a detailed and novel field study was established in the riparian zone and lower hillslopes of the Hafren catchment at Plynlimon, mid-Wales. This study showed that shallow bedrock groundwaters discharge into the stream channel. Pressure wave propagation in response to recharge further upslope caused a rapid displacement of shallow groundwaters up into the soils in the near-stream hillslope. A lateral fast flow horizon transported water down slope as interflow at the soil-bedrock interface such that the upper soil horizons remained largely unsaturated. Only where there was a discontinuity in the lateral fast flow horizon was water forced up as an ephemeral spring discharge at the soil surface. At this site, the major zone of soil water-groundwater coupling was in a narrow (20-25 m) strip next to the stream channel. The zone of soil water-groundwater interaction next to the stream channel is likely to depend on the nature of the lateral flow pathways and the hillslope characteristic. This study has shown the importance of the near-stream environment as a locus for soil waters that are bedrock groundwater derived; these groundwaters dominate processes in the deepest soil horizons from where soil components such as aluminium are sourced. Understanding these physical processes is fundamental for understanding upland catchment functioning and has important implications for solute transport modelling and for the sustainable management of surface water systems and stream ecology in these headwater regions.

  12. College of Agricultural and Life Sciences Soil and Water Science Department

    E-print Network

    Hill, Jeffrey E.

    of Florida SOIL SCIENCE SPECIALIZATION soil and water science major undergraduate UNDERGRADUATE DEGREECollege of Agricultural and Life Sciences Soil and Water Science Department at the University OPTIONS IN SOIL & WATER SCIENCE Water Science Specialization Environmental Management in Agriculture

  13. 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.

  14. USE OF LIMITED SOIL PROPERTY DATA AND MODELING TO ESTIMATE ROOT ZONE SOIL WATER CONTENT.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Modeling root zone soil water content at watershed scales is important for both the strategic and tactical management of water resources, but detailed soil physical and hydraulic property data required by most physically-based soil water models are generally not available over large land areas. Wit...

  15. 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 measurements showed that geophysically-derived estimates of soil water content could be used to improve spatial estimation of soil texture.

  16. 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 break through at the base of the liner occurs. Estimated saturated hydraulic conductivities were 2.5 ?? 10-9, 4.0 ?? 10-8, and 5.0 ?? 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.

  17. Carbon dioxide and water vapor exchange in response to drought in the atmosphere and in the soil

    SciTech Connect

    Schulze, E.D.

    1986-01-01

    This review describes the current hypotheses of how humidity and plant and soil water status may interact and regulate stomatal conductance and photosynthesis. This review will focus on the effects of 1. humidity, 2. leaf water potential and leaf turgor, and of 3. soil water status on leaf conductance, transpiration, and CO/sub 2/ assimilation.

  18. 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.

  19. A mathematical model for the adsorption of water vapor by soils

    NASA Astrophysics Data System (ADS)

    Kharitonova, G. V.; Vityazev, V. G.; Lapekina, S. I.

    2010-02-01

    A two-parameter mathematical model based on some physical assumptions was developed for the adsorption of water vapor by soils: W = W mh[( p/ p 0) - ( p/ p 0)3 + ( p/ p 0)6] + W res. It was shown that one of the model’s parameters is close to a conventional soil-hydrological constant, namely, the maximum hygroscopic moisture, or maximum hygroscopicity W mh. The second parameter reflects the residual water content W res as the content of immobilized water, which is bound to the most active part of the adsorbing surface, is adsorbed at the initial stage of adsorption (0 ? p/ p 0 ? 0.05), and later does not participate in the adsorption processes. Methods were proposed for the differential calculation of singular points and parameters of the model corresponding to the characteristic physical phenomena of water vapor adsorption in soils. The model was tested for the quantitative assessment of the interaction between the soil solid phase and the water vapor in different soils (a soddy-strongly podzolic soil, an ordinary chernozem, a chestnut soil, and a medium-columnar solonetz). A method was proposed for calculating the integral adsorption energy E max of the soil solid phase-water vapor interaction. It was shown that the E max values are determined by the physicochemical properties of the soils and characterize the capacity of the separate soil horizons for adsorbing water vapor. The relationship of the integral adsorption energy of the soils with the relative pressure of the water vapor and the water content was studied.

  20. PLANT MICROBE INTERACTIONS Soil Fungal Communities Respond to Grassland Plant

    E-print Network

    Thomas, David D.

    PLANT MICROBE INTERACTIONS Soil Fungal Communities Respond to Grassland Plant Community Richness with the rhizosphere of four native perennial grassland plant species, two legumes and two grasses, grown with plant community dynamics and asso- ciated soil edaphic characteristics in these grassland soils

  1. 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

  2. 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...

  3. 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...

  4. Willie Harris Address: Soil and Water Science Department

    E-print Network

    Balser, Teri C.

    1 Willie Harris Address: Soil and Water Science Department 2169 McCarty Hall University of Florida Research Associate, Soil Mineralogy 1980-1984 University of Florida Assistant Professor, Soil Mineralogy 1984-1989 University of Florida Associate Professor, Soil Mineralogy 1989-1996 University of Florida

  5. 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.

  6. 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.

  7. 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 soil water pressure over an 8-year period in the opposing ecosystems. It is believed that these variations in water fluxes reinforce the development of CaCO3 horizons present in the soil profiles, leading to a feedback between vegetation establishment, soil water fluxes and geomorphic processes in the catchment. Our results also indicate that soil properties and water fluxes compensate for large differences in evaporative demand and lead to similar actual evapotranspiration (AET) in the opposing slopes.

  8. CROP MANAGEMENT EFFECTS ON WATER INFILTRATION FOR CLAYPAN SOILS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Plant water and nutrient use for claypan soils are restricted by an argillic horizon (clay content > 500 g/kg) that typically occurs 20 to 40 cm below the soil surface. Identifying water infiltration characteristics for claypan soils under different management provides crucial information needed to ...

  9. 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.

  10. 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, ?s eq; the root system equivalent conductance, Krs; and a threshold leaf water potential, ?leaf 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.

  11. 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.

  12. 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.

  13. Water retention of arctic zone soils (Spitsbergen)

    NASA Astrophysics Data System (ADS)

    Melke, J.; Witkowska-Walczak, B.; Bartmi?ski, P.

    2013-12-01

    The water retention characteristics of the arctic zone soils ((TurbicCryosol (Skeletic), TurbicCryosols (Siltic, Skeletic) and BrunicTurbicCryosol (Arenic)) derived in different micro-relief forms were determined. Water retention curves were similar in their course for the mud boils, cell forms, and sorted circles ie for TurbicCryosols. For these forms, the mud boils showed the highest water retention ability, whereas the sorted circles - the lowest one. Water retention curves for the tundra polygons (Brunic TurbicCryosol, Arenic) were substantially different from these mentioned above. The tundra polygons were characterized by the lowest bulk density of 1.26 g cm-3, whereas the sorted circles (TurbicCryosol, Skeletic) - the highest: 1.88 g cm-3. Total porosity was the highest for the tundra polygons (52.4 and 55.5%) and the lowest - for the sorted circles (28.8 and 26.2%). Pore size distribution of the investigated soils showed that independently of depths, the highest content of large and medium pores was noticed for the tundra polygons ie 21.2-24.2 and 19.9-18.7%, respectively. The lowest content of large pores was observed for the cell forms (6.4-5.9%) whereas the mud boils exhibited the lowest amount of medium sized pores (12.2-10.4%) (both TurbicCryosols Siltic, Skeletic). The highest content of small pores was detected in the mud boils - 20.4 and 19.0%.

  14. SEASONAL SOIL MOISTURE PREDICTION USING A CLIMATE-PLANT-SOIL COUPLED AGROECOSYSTEM WATER MANAGEMENT MODEL

    E-print Network

    Takle, Eugene S.

    3.13 SEASONAL SOIL MOISTURE PREDICTION USING A CLIMATE-PLANT-SOIL COUPLED AGROECOSYSTEM WATER of soil moisture is given at grid resolution that is too coarse to resolve prominent weather systems on a quasi real-time basis, forecasting soil moisture, precipitation, temperature, and other variables

  15. 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.

  16. 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.

  17. Water-entry value as an alternative indicator of soil water-repellency and wettability

    E-print Network

    Dundas, Robert G.

    Water-entry value as an alternative indicator of soil water-repellency and wettability Z. Wang*, L, 1969). Three drops of distilled water from a standard medicine dropper are placed on the smoothed as an alternative indicator of soil water-repellency. By first imposing a low hydraulic pressure at the soil surface

  18. 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 ...

  19. 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...

  20. 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,...

  1. 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

  2. Review of soil water models with respect to savanna hydrology 

    E-print Network

    Derry, Julian F; Russell, Graham; Liedloff, Adam C

    2006-07-21

    Effective management leading towards sustainable rangeland production in arid and semi-arid regions will stem from effective soil water management and comprehension of the hydrological properties of the soil in relation ...

  3. PERMEABILITY OF SOILS TO FOUR ORGANIC LIQUIDS AND WATER

    EPA Science Inventory

    Saturated hydraulic conductivities and intrinsic permeabilities were evaluated for eight contrasting soils with four organic liquids and water. The organic liquids were kerosene, ethylene glycol, isopropyl alcohol and xylene. Intrinsic permeability for any given soil varied inver...

  4. BEE Soil & Water Lab Fall 2012 Seminar Series

    E-print Network

    BEE Soil & Water Lab Fall 2012 Seminar Series Mondays at 3:30pm, Riley Robb Hall room 205 September, Angenent Lab, Cornell BEE dept. Developing and utilizing electrodes to monitor biological activity in soils

  5. 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.

  6. 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

  7. Response of Eucalyptus grandis trees to soil water deficits.

    PubMed

    Dye, P. J.

    1996-01-01

    The use of potential transpiration models to simulate transpiration rates in areas prone to soil water deficits leads to overestimates of water use as the soil dries. Therefore, I carried out studies on Eucalyptus grandis W. Hill ex Maiden trees subjected to soil drying at two field sites in the Mpumalanga province of South Africa to determine the relation between transpiration rate and soil water availability. I hypothesized that, with this relationship defined, simple modeling of the soil water balance could be used to predict what fraction of potential transpiration was taking place at a given time. Site 1 supported a stand of 3-year-old E. grandis trees, whereas 9-year-old trees were growing on Site 2, situated 2 km away. At each site, plastic sheeting was laid over the ground to prevent soil water recharge and thereby allow the roots in the soil to induce a continuous progressive depletion of soil water. Measurements of predawn xylem pressure potential, leaf area index, growth and sap flow rates revealed that prevention of soil water recharge resulted in only moderate drought stress. At Site 1, the trees abstracted water down to 8 m below the surface, whereas trees at Site 2 obtained most of their water from depths below 8 m. I found that modeling the water balance of deep rooting zones is impractical for the purpose of simulating nonpotential transpiration rates because of uncertainties about the depth of the root system, the soil water recharge mechanism and the water retention characteristics of the deep subsoil strata. I conclude that predicting the occurrence and severity of soil water deficits from the soil water balance is not feasible at these sites. PMID:14871767

  8. Outcomes of fungal interactions are determined by soil invertebrate grazers.

    PubMed

    Crowther, Thomas W; Boddy, Lynne; Jones, T Hefin

    2011-11-01

    Saprotrophic fungal community composition, determined by the outcome of competitive mycelial interactions, is one of the many key factors affecting soil nutrient mineralisation and decomposition rates. Fungal communities are not generally predicted to be regulated by top-down factors, such as predation, but rather by bottom-up factors, including resource availability. We show that invertebrate grazers can exert selective pressures on fungal decomposer communities in soil, reversing the outcomes of competitive interactions. By feeding selectively on the cord-forming fungus Resinicium bicolor, isopods prevented the competitive exclusion of Hypholoma fasciculare and Phanerochaete velutina in soil and wood. Nematode populations also reversed the outcomes of competitive interactions by stimulating growth of less competitive fungi. These represent two opposing mechanisms by which soil fauna may influence fungal community composition and diversity. Factors affecting soil invertebrate communities will have direct consequences for fungal-mediated nutrient cycling in woodland soils. PMID:21929699

  9. 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.

  10. Interaction of Escherichia coli and soil particles in runoff.

    PubMed

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

    2006-05-01

    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 microm). However, when unattached cells were inoculated into the system, the E. coli appeared to attach predominantly to small particles (< 2 microm) 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

  11. 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 bentonite systems. Also, sodium carbonate greatly reduces the possible reactor corrosion under hydrothermal conditions. Our results show that a water-to-sand ratio of at least 3:1 is required to efficiently remove PAH from soil under static conditions.

  12. Soil water and transpirable soil water fraction variability within vineyards of the Penedès DO (NE Spain) affected by management practices

    NASA Astrophysics Data System (ADS)

    Concepción Ramos, Maria

    2015-04-01

    This work investigated the variability in soil water recorded within the vineyard plots related to soil properties and management practices and its influence on the transpirable sol water fraction. The study was carried out in vineyards in the Penedès Designation of Origin, planted with Chardonnay, with different disturbance degree and with compost treated and untreated areas within the plots. The response in years with different rainfall distributions, included years with extreme situations were evaluated. The main soil types are Typic Xerorthent and Calcixerollic Xerorthent and soil is bare most of the time. Soil water content was measured at different depths using TDR probes. The transpirable soil water fraction was estimated as the ratio between available soil water (ASW) at a given date and the total transpirable soil water (TTSW). TTSW was estimated as the soil water reserve held between an upper and lower limit (respectively, the soil water content near field capacity and soil water content at the end of a dry summer) and integrated over the estimated effective rooting depth. Both minimum and maximum soil water values varied within the plot at all depths. On the surface the minimum values ranged between 4.45 to about 10%, while on deeper layers it ranged between 7.8 and 17.8%. Regarding the maximum value varied between 17.45 and 24.8%. The transpirable soil water fraction for a given year varied significantly within the plot, with differences greater than 20% between the treated and untreated areas. The results were more exacerbated in the driest years an in those with more irregular distribution. Water available has a significant effect on yield. The results indicate the need of using different strategies for water management within the plots.

  13. 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

  14. 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...

  15. 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...

  16. 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 soil water regimes between the IM and GP regions may be useful for understanding the potential influence of climate changes on soil water patterns and resulting dominant plant functional groups in both regions.

  17. Recharge in northern clime calcareous sandy soils: soil water chemical and carbon-14 evolution

    NASA Astrophysics Data System (ADS)

    Reardon, E. J.; Mozeto, A. A.; Fritz, P.

    1980-11-01

    Chemical analyses were performed on soil water extracted from two cores taken from a sandy calcareous soil near Delhi, Ontario. Calcite saturation is attained within the unsaturated zone over short distances and short periods of time, whereas dolomite undersaturation persists to the groundwater table. The progressive dissolution of dolomite by soil water, within the unsaturated zone, after calcite saturation is reached results in calcite supersaturation. Deposition of iron and manganese oxyhydroxide phases occurs at the carbonate leached/unleached zone boundary. This is a result of soil water neutralization due to carbonate dissolution during infiltration but may also reflect the increased rate of oxidation of dissolved ferrous and manganous ions at higher pH's. The role of bacteria in this process has not been investigated. The depth of the carbonate leached/unleached zone boundary in a calcareous soil has important implications for 14C groundwater dating. The depth of this interface at the study site (-2 m) does not appear to limit 14C diffusion from the root zone to the depth at which carbonate dissolution occurs. Thus, soil water achieves open system isotopic equilibrium with the soil CO 2 gas phase. It is calculated that in soils with similar physical properties to the study soil but with depths of leaching of 5 m or more, complete 14C isotopic equilibration of soil water with soil gas would not occur. Soil water, under these conditions would recharge to the groundwater exhibiting some degree of closed system 14C isotopic evolution.

  18. 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

  19. 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.

  20. 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 ...

  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. 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

  3. Soil water monitoring using heated distributed temperature sensing

    NASA Astrophysics Data System (ADS)

    Striegl, A. M.; Loheide, S. P.

    2010-12-01

    Traditionally, soil water measurements could only be obtained as point-in-time and point-in-space samples. These methods result in uncertainty in understanding the soil water dynamics of a site because of issues of scale, soil and vegetation spatial heterogeneity, and temporal variability of climatic conditions. Previous researchers have demonstrated the feasibility of obtaining distributed soil water content measurements using the heat pulse method with fiber optic temperature sensing. Numerical simulations of multiple proposed hybrid cable cross-sections guided the design and fabrication of a custom bundle of fiber optics, resistance heating conductors, and protective coatings for soil water monitoring. The conductors introduce a heat pulse to the surrounding soil, while temperature rise versus time is monitored with a Distributed Temperature Sensing (DTS) system using the fiber optics in the bundle. The temperature rise versus time response is related to the matric potential and water content of the soil surrounding the cable. In order to monitor the near-surface hydrology of a recently restored southwestern Wisconsin floodplain, the cable was buried at a depth of 20cm along a transect perpendicular to the Upper East Branch of the Pecatonica River near Barneveld, Wisconsin. Spatial variations of soil water can be readily observed with this technology as the cable spans various vegetation communities, soil types, and moisture conditions at this site. This new technology will help bridge the existing gaps of scale in soil water monitoring networks by providing high resolution, continuous measurements over large spatial scales.

  4. 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.

  5. 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.

  6. 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...

  7. 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 ...

  8. 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,…

  9. SORPTION OF A HYDROPHILIC PESTICIDE: EFFECTS OF SOIL WATER CONTENT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Transport of pesticide to groundwater is governed in part by sorption of the pesticide to soil particles. Sorption may be dependent on soil moisture conditions, but limited data are available from which to elucidate the effect. The objective of this research is to determine the effects of soil water...

  10. Linking soil and water quality in conservation agricultural systems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil and water resources are fundamental components of agriculture. Successful utilization of these resources for sustainable agricultural production is partly dependent upon how they are conserved. Soil quality is generally defined by how well soil functions under a given set of environmental con...

  11. 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.

  12. 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 conditions by the land management, but also due to the manipulation of the soil before and during the measurement. Direct "in situ" field evaluations have to be preferred in any case to 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, or through the use of stochastic models such as the SCS Curve Number Method, or of other models using empirical or physical approaches, which have demonstrated to be of limited value in most of the cases. References Philip, J. R., 1954., An infiltration equation with physical significance: Soil Sci..,v. 77, p. 153-157. Philip, J. R., 1958. The theory of infiltration, pt. 7: Soil Sci., v. 85, no. 6, p. 333-337. Pla, I.1981. Simuladores de lluvia para el estudio de relaciones suelo-agua bajo agricultura de secano en los trópicos. Rev. Fac. Agron. XII(1-2):81-93.Maracay (Venezuela) Pla, I. 1986. A routine laboratory index to predict the effects of soil sealing on soil and water conservation. En "Assesment of Soil Surface Sealing and Crusting". 154-162.State Univ. of Ghent.Gante (Bélgica Pla, I., 1997. A soil water balance model for monitoring soil erosion processes and effects on steep lands in the tropics. Soil Technology. 11(1):17-30. Elsevier Pla, I., M.C. Ramos, S. Nacci, F. Fonseca y X. Abreu. 2005. Soil moisture regime in dryland vineyards of Catalunya (Spain) as influenced by climate, soil and land management. "Integrated Soil and Water Management for Orchard Development". FAO Land and Water Bulletin 10. 41-49. Roma (Italia). Pla, I., 2006. Hydrological approach for assessing desertification processes in the Mediterranean region. In W.G. Kepner et al. (Editors), Desertification in the Mediterranean Region. A Security Issue. 579-600 Springer. Heidelberg (Germany) Pla, I. 2011. Evaluación y Modelización Hidrológica para el Diagnóstico y Prevención de "Desastres Naturales". Gestión y Ambiente 14 (3): 17-22. UN-Medellín (Colombia). ISSN 0124.177X

  13. 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.

  14. 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.

  15. 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.

  16. [Simulating soil water drainage and nitrogen leaching in Tianranwenyanqu Basin].

    PubMed

    Li, Xiao-Peng; Zhang, Jia-Bao; Liu, Jin-Tao; Zhu, An-Ning

    2009-03-15

    Soil water drainage and nitrogen leaching in Tianranwenyanqu Basin was simulated using DNDC model. The model was validated by data of the water and nitrogen controlling experiment in the basin. The correlation coefficients between simulated and measured values of daily 1 m soil water storage,lower boundary NO3(-) -N concentration, soil water drainage and nitrogen leaching were 0.94 (n = 40), 0.66 (n = 49), 0.89 (n =40), 0.94 (n = 39); and RMSEs were 15.66 mm, 2.66 mg x kg(-1), 9.00 mm, 0.94 kg x hm(-2), respectively. The validated model was then used to simulate soil water drainage and nitrogen leaching in the basin. The results show that, under multi-year average climate and conventional management condition, annual soil water drainage and nitrogen leaching of winter-wheat and summer-corn rotation fields in this basin were 220-327 mm and 73.1-100.6 kg x hm(-2), respectively. The distribution of water drainage and nitrogen leaching were uneven in time and space, leaching happened mainly after fertilization, irrigation or heavy rainfall, and sandy soil regions were the most serious nitrogen leaching area. Unreasonable irrigation, fertilization and poor water and fertilizer preserving capability of the soils,were the major causes of soil water drainage and nitrogen leaching. PMID:19432342

  17. Effects of Woody Vegetation Removal on Soil Water Dynamics in a South Texas Shrubland 

    E-print Network

    Mattox, April Marie

    2013-07-30

    m soil depth to drier shallow soils. Roller chopping in sandy soils is the vegetation removal treatment and soil type most likely to result in water moving beyond the root zone. Although treatments had significant effects on soil moisture dynamics...

  18. 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.

  19. 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...

  20. 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.

  1. 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...

  2. SOIL WATER USE AND SOIL RESIDUE COVERAGE BY SUNFLOWER COMPARED TO OTHER CROPS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Continuous crop rotations with a diversity of species are essential for improving soil health and decreasing the impact of disease, weeds and insects. Soil water content and soil surface coverage by crop residues were studied in a crop sequence study carried out using no-till management. The exper...

  3. Soil and Water Science Department University of Florida Arsenic background concentrations in Florida urban soils

    E-print Network

    Ma, Lena

    Soil and Water Science Department University of Florida Arsenic background concentrations in Florida urban soils Ma, L. Q., W. Harris, and A. Hornsby 1/2000-12/2002 OBJECTIVE Establish a robust and agricultural areas throughout Florida will be collected based on locations, soil types, and land uses

  4. Vegetation dynamics and soil water balance in a water-limited Mediterranean ecosystem on Sardinia, Italy

    NASA Astrophysics Data System (ADS)

    Montaldo, N.; Albertson, J. D.; Mancini, M.

    2008-01-01

    Mediterranean ecosystems are commonly heterogeneous savanna-like ecosystems, with contrasting plant functional types (PFTs, e.g., grass and woody vegetation) competing for the water use. Mediterranean ecosystems are also commonly characterized by strong inter-annual rainfall variability, which influences the distributions of PFTs that vary spatially and temporally. With the objective to investigate interactions between vegetation dynamics, soil water budget and land-surface fluxes in a water-limited ecosystem, an extensive field campaign in a Mediterranean setting was performed. Also a vegetation dynamic model (VDM) is coupled to a 3-component (bare soil, grass and woody vegetation) Land surface model (LSM). The case study is in Orroli, situated in the mid-west of Sardegna within the Flumendosa river basin. The landscape is a mixture of Mediterranean patchy vegetation types: trees, including wild olives and cork oaks, different shrubs and herbaceous species. Land surface fluxes, soil moisture and vegetation growth were monitored during the May 2003-June 2006 period. Interestingly, hydrometeorological conditions of the monitored years strongly differ, with dry and wet years in turn, such that a wide range of hydrometeorological conditions can be analyzed. The coupled VDM-LSM model is successfully tested for the case study, demonstrating high model performance for the wide range of eco-hydrologic conditions. The use of the VDM in the LSM is demonstrated to be essential when studying the climate-soil-vegetation interactions of these water-limited ecosystems. Results demonstrate also that vegetation dynamics are strongly influenced by the inter-annual variability of atmospheric forcing, with grass leaf area index changing significantly each spring season according to seasonal rainfall amount.

  5. 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, could induce stability (Resistance, Resilience) of soil microbial communities towards stresses, in particular severe drought. The knowledge of these interactions in the rhizosphere between local hydric soil properties and microbial behaviour facing drought, could allow a better understanding of the functioning of agro-ecosystems for their management in a changing climate.

  6. 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.

  7. 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 between the stable and fluctuating water table columns were detected.

  8. Soil and Water Assessment Tool Theoretical Documentation Version 2009 

    E-print Network

    Neitsch, S.L.; Arnold, J.G.; Kiniry, J.R.; Williams, J.R.

    2011-01-01

    Documentation.pdf.txt Content-Type text/plain; charset=ISO-8859-1 Theoretical Documentation Version 2009 Soil & Water Assessment Tool TR-406 COLLEGE OF AGRICULTURE AND LIFE SCIENCES TR-406 2011 Soil and Water Assessment Tool... BACTERIAL BIOMASS 395 FATE AND TRANSPORT OF BACTERIA BIOMASS 396 FIELD CAPACITY 397 CLOGGING EFFECT ON HYDRAULIC CONDUCTIVITY 398 SOIL MOISTURE AND PERCOLATION 398 NITROGEN, BOD, FECAL COLIFORM 399 PHOSPHORUS REMOVAL...

  9. ISSN 0378-4738 = Water SA Vol. 27 No. 1 January 2001 71Available on website http://www.wrc.org.za Plant-soil interactions of sludge-borne heavy metals and the

    E-print Network

    ://www.wrc.org.za Plant-soil interactions of sludge-borne heavy metals and the effect on maize (Zea mays L.) seedling and Plant Pathology, Forestry and Agricultural Biotechnology Institute, University of Pretoria, Pretoria types (clayey, loamy and sandy) on maize seedlings. Growth differences

  10. University of Florida Soil and Water Science Department

    E-print Network

    Ma, Lena

    1 University of Florida Soil and Water Science Department SWS 6209: Urban Soil and Water Systems Credit/Contact 3 Teaching Format Canvas elearning: https://ufl.instructure.com/ Pre-recorded lectures/Mac operating system; web browsing; Power Point; robust/high-speed Internet connection. Course Description

  11. University of Florida Soil and Water Science Department

    E-print Network

    Ma, Lena

    University of Florida Soil and Water Science Department SWS 4XXX: Urban Soil and Water Systems-38250-12014 Pre-recorded lectures Reading materials Lecture slides Multi-media materials Live chat sessions/Mac operating system; web browsing; Power Point; robust/high-speed Internet connection. Course Description

  12. University of Florida Soil and Water Science Department

    E-print Network

    Ma, Lena

    1 University of Florida Soil and Water Science Department SWS 4204: Urban Soil and Water Systems/Contact 3 Teaching Format Canvas elearning: https://ufl.instructure.com/courses/314330 Pre-recorded lectures/Mac operating system; web browsing; Power Point; robust/high-speed Internet connection. Course Description

  13. University of Florida Soil and Water Science Department

    E-print Network

    Ma, Lena

    University of Florida Soil and Water Science Department SWS 6XXX: Urban Soil and Water Systems.ufl.edu/portal/site/UFL-SWS6932-38252-12014 Pre-recorded lectures Reading materials Lecture slides Multi-media materials Live chat/Mac operating system; web browsing; Power Point; robust/high-speed Internet connection. Course Description

  14. 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 ...

  15. 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...

  16. Awards and Fellowships -Soil and Water Science Department

    E-print Network

    Ma, Lena

    Awards and Fellowships - Soil and Water Science Department Each year, the Soil and Water Science Skulnick Fellowships. Students are encouraged to apply for these Fellowships if they feel qualified. In order to apply, a student must submit 1) a letter outlining their qualifications for the Fellowship

  17. Simulating daily soil water under foothills fescue grazing with the soil and water assessment tool model (Alberta, Canada)

    NASA Astrophysics Data System (ADS)

    Mapfumo, Emmanuel; Chanasyk, David S.; Willms, Walter D.

    2004-10-01

    Grazing is common in the foothills fescue grasslands and may influence the seasonal soil-water patterns, which in turn determine range productivity. Hydrological modelling using the soil and water assessment tool (SWAT) is becoming widely adopted throughout North America especially for simulation of stream flow and runoff in small and large basins. Although applications of the SWAT model have been wide, little attention has been paid to the model's ability to simulate soil-water patterns in small watersheds. Thus a daily profile of soil water was simulated with SWAT using data collected from the Stavely Range Sub-station in the foothills of south-western Alberta, Canada. Three small watersheds were established using a combination of natural and artificial barriers in 1996-97. The watersheds were subjected to no grazing (control), heavy grazing (2.4 animal unit months (AUM) per hectare) or very heavy grazing (4.8 AUM ha-1). Soil-water measurements were conducted at four slope positions within each watershed (upper, middle, lower and 5 m close to the collector drain), every 2 weeks annually from 1998 to 2000 using a downhole CPN 503 neutron moisture meter. Calibration of the model was conducted using 1998 soil-water data and resulted in Nash-Sutcliffe coefficient (EF or R2) and regression coefficient of determination (r2) values of 0.77 and 0.85, respectively. Model graphical and statistical evaluation was conducted using the soil-water data collected in 1999 and 2000. During the evaluation period, soil water was simulated reasonably with an overall EF of 0.70, r2 of 0.72 and a root mean square error (RMSE) of 18.01. The model had a general tendency to overpredict soil water under relatively dry soil conditions, but to underpredict soil water under wet conditions. Sensitivity analysis indicated that absolute relative sensitivity indices of input parameters in soil-water simulation were in the following order; available water capacity > bulk density > runoff curve number > fraction of field capacity (FFCB) > saturated hydraulic conductivity. Thus these data were critical inputs to ensure reasonable simulation of soil-water patterns. Overall, the model performed satisfactorily in simulating soil-water patterns in all three watersheds with a daily time-step and indicates a great potential for monitoring soil-water resources in small watersheds.

  18. 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.

  19. 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.

  20. 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...

  1. 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

  2. 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...

  3. 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 (?), 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 ? 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. Automated weather stations for the continuous measurement of all relevant climatic factors were established at all grass-dominated sites. Based on the field data, soil water balances were simulated for all sites with the HYDRUS model. Potential ET for the grass-dominated sites was calculated using the Penman-Monteith equation. Results regarding the spatio-temporal variability of available soil water of the study sites will be shown and discussed in this contribution. Moreover, correlations between soil water availability and ETa will be presented.

  4. On the infiltration of rain water through the soil with runo# of the excess water

    E-print Network

    Fasano, Antonio

    On the infiltration of rain water through the soil with runo# of the excess water Iacopo Borsi '' Viale Morgagni 67/A, 50134 Firenze, Italy Abstract This paper deals with the modelling of the rain water infiltration through the soil above the aquifer in case of runo# of the excess water. The main feature

  5. 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.

  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. Effects of Frozen Soil on Snowmelt Runoff and Soil Water Storage at a Continental Scale

    E-print Network

    Yang, Zong-Liang

    by the University of New Hampshire­Global Runoff Data Center and a terrestrial water storage changeEffects of Frozen Soil on Snowmelt Runoff and Soil Water Storage at a Continental Scale GUO-YUE NIU of Texas at Austin, Austin, Texas (Manuscript received 20 September 2005, in final form 14 January 2006

  8. 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 ...

  9. Tillage effects on soil water redistribution and bare soil evaporation throughout a season

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Tillage-induced changes in soil properties are difficult to predict, yet can influence how water is redistributed within the profile after precipitation and subsequent evaporation rates. We evaluated the effects of sweep tillage (ST) on near surface soil water dynamics as compared with an untilled (...

  10. 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...

  11. 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.

  12. 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

  13. Hydraulic redistribution of soil water by roots affects whole-stand evapotranspiration and net ecosystem

    E-print Network

    Noormets, Asko

    Hydraulic redistribution of soil water by roots affects whole-stand evapotranspiration and net sap flow, soil water content, understory, water potential. Summary · Hydraulic redistribution (HR , respectively. · Hydraulic redistribution mitigated the effects of soil drying on understory and stand

  14. 26 CFR 1.175-2 - Definition of soil and water conservation expenditures.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...incurred for the purpose of soil or water conservation in respect...following are examples of soil and water conservation: (i) Constructing...the like, to detain or control the flow of water, to check soil erosion on...

  15. 26 CFR 1.175-2 - Definition of soil and water conservation expenditures.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...incurred for the purpose of soil or water conservation in respect...following are examples of soil and water conservation: (i) Constructing...the like, to detain or control the flow of water, to check soil erosion on...

  16. 26 CFR 1.175-2 - Definition of soil and water conservation expenditures.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...incurred for the purpose of soil or water conservation in respect...following are examples of soil and water conservation: (i) Constructing...the like, to detain or control the flow of water, to check soil erosion on...

  17. 26 CFR 1.175-2 - Definition of soil and water conservation expenditures.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...incurred for the purpose of soil or water conservation in respect...following are examples of soil and water conservation: (i) Constructing...the like, to detain or control the flow of water, to check soil erosion on...

  18. 26 CFR 1.175-2 - Definition of soil and water conservation expenditures.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...incurred for the purpose of soil or water conservation in respect...following are examples of soil and water conservation: (i) Constructing...the like, to detain or control the flow of water, to check soil erosion on...

  19. 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.

  20. Coupled Soil-Plant Water Dynamics During Drought-Rewetting Transitions

    NASA Astrophysics Data System (ADS)

    Volkmann, T. H.; Haberer, K.; Gessler, A.; Weiler, M.

    2013-12-01

    The predicted climate and land-use changes could have dramatic effects on the water balance of the soil-vegetation system, particularly under frequent drought and subsequent rewetting conditions. Yet, estimation of these effects and associated consequences for the structure and functioning of ecosystems, groundwater recharge, drinking water availability, and the water cycle is currently impeded by gaps in our understanding of the spatiotemporal dynamics of soil water in the rooted soil horizons, the dynamics and driving physiological processes of plant water acquisition, and the transpiration from plant leaves under changing environmental conditions. Combining approaches from the disciplines of plant ecophysiology and soil and isotope hydrology, this work aims to fill this gap by quantitatively characterizing the interaction between plant water use - as affected by rooting patterns and ecophysiology of different plant functional groups - and the water balance of variably complex ecosystems with emphasis on drought and rewetting phases. Results from artificial drought and subsequent rewetting in field experiments using isotopically and dye (Brilliant Blue FCF) labeled water conducted on plots of various surface cover (bare soil, grass, beech, oak, vine) established on luvisol on loess in southwestern Germany are presented. Detailed spatiotemporal insights into the coupled short-term (hours to days) dynamics of soil and plant water during the experiments is facilitated by the application of newly developed techniques for high-frequency in-situ monitoring of stable isotope signatures in both pore water and transpired water using commercial laser-based spectrometers in conjunction with plant ecophysiological, soil physical state, and dye staining observations. On the one hand, the spatiotemporal patterns of plant water uptake are assessed and related to morphological and physiological traits driving plant water uptake, functional adaptations of plants to changes of soil water availability, and intra- and interspecies competition for water resources access. On the other hand, the effects of vegetation cover on infiltration, preferential flow paths characteristics, and soil water storage in the rooted soil horizons are investigated. The results of the experiments and the developed methodology will contribute to an improved understanding of ecosystem response and adaptation to drought and short-term changes in environmental conditions.

  1. 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 data as a function of the wetting liquid surface tensions. These linear relationships were found to reflect the mechanisms underlying the surface energy parameter requirements for wetting. PMID:26319321

  2. 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 (??) of the soil water content (SWC) and mean spatial soil water content () formed combinations of concave and convex hyperbolas. However, it strongly depended on SWC state and season. Generally, ?? 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, ??() was either ascending or converging with decreasing . A concave shape was observed when approached to dry state. The majority of ??() hysteresis loops were observed in intermediate and intermediate/wet state of SWC. All hysteretic loops were clockwise oriented. Rainfall intensity and distribution were identified as main factors driving SWC variability at the regional scale.

  3. 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%). Soil WR was assessed in soil samples (0-10 cm) collected monthly during 6 monhts after burning. In the second case, a fire-affected forest soil from Calañas (Huelva, southweastern Spain) was studied. Soil plots under different fire severities (low, medium and high severity burning) and rock fragment cover classes (20-40 and 60-80%) were analyzed. Soil WR was assessed in the soil surface immediately under the vertical projection of randomly selected stones and in the middle point between these and the nearest stones. Unburned adjacent soils under similar rock fragment cover classes were used as control. All soil WR assessments were carried out using the WDPT method. RESULTS In both cases, soil WR was induced in the soil surface contacting rock fragments after burning. Severity of WR ranged between subcritical or slight (low severity burning) and strong (high severity burning). Soil WR was also found to increase with rock fragment cover, especially after moderate or high severity burning, both under and between rock fragments. It is suggested that high density of rock fragments on the soil surface create a continuous surface of high residence of temperature peaks (in agreement with García-Moreno et al., 2013). Combustion of plant residues in oxygen depletion conditions between adjacent nearby rock fragments contributes to heat transfer to the soil surface and consequent enhanced soil WR. REFERENCES García-Moreno, J., Gordillo-Rivero, A.J., Gil, J., Jiménez-Morillo, N.T., Mataix-Solera, J., González-Peñaloza, F.A., Granged, A.J.P., Bárcenas-Moreno, G., Jiménez-Pinilla, P., Lozano, E., Jordán, A., Zavala, L.M. 2013. Do stones modify the spatial distribution of fire-induced soil water repellency? Preliminary data. Flamma, 4:76-80.

  4. 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, but also improve the description of the rooting environment. Until now there have been no attempts to couple root architecture and pore network models. In our work we present a first attempt to join both types of models using the root architecture model of Leitner et al., (2010) and a pore network model presented by Raoof et al. (2010). The two main objectives of coupling both models are: (i) Representing the effect of root induced biopores on flow and transport processes: For this purpose a fixed root architecture created by the root model is superimposed as a secondary root induced pore network to the primary soil network, thus influencing the final pore topology in the network generation. (ii) Representing the influence of pre-existing pores on root branching: Using a given network of (rigid) pores, the root architecture model allocates its root axes into these preexisting pores as preferential growth paths with thereby shape the final root architecture. The main objective of our study is to reveal the potential of using a pore scale description of the plant growth medium for an improved representation of interaction processes at the interface of root and soil. References Raoof, A., Hassanizadeh, S.M. 2010. A New Method for Generating Pore-Network Models. Transp. Porous Med. 81, 391-407. Leitner, D, Klepsch, S., Bodner, G., Schnepf, S. 2010. A dynamic root system growth model based on L-Systems. Tropisms and coupling to nutrient uptake from soil. Plant Soil 332, 177-192.

  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 remained at the same stable level for both NP and DR over time. The chlorophyll content of the treatment samples was significantly lower than that of the controls. This supports our assumption that water extracts of F. fulgens may indeed cause a dieback of the host moss. In a next step of the project, the substances responsible for this detrimental effect on the moss will be identified. The accelerated dieback of the moss probably causes increased CO2 concentrations below the lichen thalli, improving their overall photosynthetic performance. Thus, both dead and living biomass in biocrusts increase upon this association, promoting microbial activity and the growth of vascular plant vegetation.

  6. Vegetation dynamics and soil water balance in a water-limited Mediterranean ecosystem on Sardinia, Italy

    NASA Astrophysics Data System (ADS)

    Montaldo, N.; Albertson, J. D.; Mancini, M.

    2008-11-01

    Mediterranean ecosystems are commonly heterogeneous savanna-like ecosystems, with contrasting plant functional types (PFTs, e.g. grass and woody vegetation) competing for water. Mediterranean ecosystems are also commonly characterized by strong inter-annual rainfall variability, which influences the distributions of PFTs that vary spatially and temporally. An extensive field campaign in a Mediterranean setting was performed with the objective to investigate interactions between vegetation dynamics, soil water budget and land-surface fluxes in a water-limited ecosystem. Also a vegetation dynamic model (VDM) is coupled to a 3-component (bare soil, grass and woody vegetation) Land surface model (LSM). The case study is in Orroli, situated in the mid-west of Sardegna within the Flumendosa river basin. The landscape is a mixture of Mediterranean patchy vegetation types: trees, including wild olives and cork oaks, different shrubs and herbaceous species. Land surface fluxes, soil moisture and vegetation growth were monitored during the May 2003 June 2006 period. Interestingly, hydrometeorological conditions of the monitored years strongly differ, with dry and wet years in turn, such that a wide range of hydrometeorological conditions can be analyzed. The coupled VDM-LSM model is successfully tested for the case study, demonstrating high model performance for the wide range of eco-hydrologic conditions. Results demonstrate also that vegetation dynamics are strongly influenced by the inter-annual variability of atmospheric forcing, with grass leaf area index changing significantly each spring season according to seasonal rainfall amount.

  7. 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.

  8. 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 could focus on a long time (e.g. from vegetation to maturity) effect under different soil water conditions, such as irrigated, sheltered and normal status. Langensiepen, M., Kupisch, M., Graf, A., Schmidt, M. and Ewert, F., 2014. Improving the stem heat balance method for determining sap-flow in wheat. Agricultural and Forest Meteorology, 186: 34-42.

  9. 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.

  10. 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 soil before and during the measurement. Due to the commonly found high variability, natural or induced by land management, of the soil surface and subsurface hydrological properties, and to the limitations imposed by the requirements of water for the measurements, there is proposed a simple and handy method, which do not use high volumes of water, adaptable to very different soil and land conditions, and that allow many repeated measurements with acceptable accuracy for most of the purposes. References Pla, I., 1997. A soil water balance model for monitoring soil erosion processes and effects on steep lands in the tropics. Soil Technology. 11(1):17-30. Elsevier Pla, I., 2006. Hydrological approach for assessing desertification processes in the Mediterranean region. In W.G. Kepner et al. (Editors), Desertification in the Mediterranean Region. A Security Issue. 579-600 Springer. Heidelberg (Germany) Reynolds W.D., B.T. Bowman, R.R. Brunke, C.F. Drury and C.S. Tan. 2000. Comparison of Tension Infiltrometer, Pressure Infiltrometer, and Soil Core Estimates of Saturated Hydraulic Conductivity . Soil Science Society of America Journal 64:478-484 Segal, E., S.A.Bradford, P. Shouse; N. Lazarovich, and D. Corwin. 2008. Integration of Hard and Soft Data to Characterize Field-Scale Hydraulic Properties for Flow and Transport Studies. Vadose Zone J 7:878-889 Young, E. 1991. Infiltration measurements, a review. Hydrological processes 5: 309-320.

  11. The history of soil erosion: Interpreting historical sources, buried soils and colluvial sediments as archives of past soil erosion and human-environment interactions in the Longue Durée

    NASA Astrophysics Data System (ADS)

    Dotterweich, Markus

    2015-04-01

    Soil erosion threatens the environment and the sustainability of agricultural practices since the earliest societies started modifying their natural environment in the Neolithic. Almost all farming-based cultures in the world, from large civilizations to peasant groups on little islands, have suffered from soil erosion by water. The amounts of soil erosion varied largely through time and space, and extreme events have left a wide variety of imprints on the landscape over millennia. Eroded hillslopes and gullies, deposited sediments in sinks like lakes, footslopes, valleys, floodplains, and river deltas are geomorphic legacies that have been linked to changes in land use and climate by many studies during the last decades. However, a standardized analysis and interpretation of these geomorphic legacies is problematic because of the variety of methodological approaches and the nonlinearity between soil erosion, climate, and land use. Cascading effects, land use structures, soil management, soil conservation strategies, and long-term system changes have produced different signals over time. Historical records are crucial and an invaluable source to provide alternative proxies about soil erosion in the past. Direct observations of individual soil erosion events may restrict the deposition of a distinct sediment package to a certain time span. They also expand the range of alternative interpretations, particularly with respect to the long-term effects of soil erosion to ecosystem services and socioeconomic processes. However, historical records also need critical analyses regarding their origin, intention, and quality. They were often created in the context of personal interests or political issues rather than being based on scientific facts; and it is often unclear if they represent certain events, narratives, or vague assumptions. This presentation will present and discuss examples of geomorphic evidences and historical records of past soil erosion for the deciphering of human-environment interactions in the Longue Durée.

  12. The role of waste thermal water in the soil degradation

    NASA Astrophysics Data System (ADS)

    Balog, Kitti; Farsang, Andrea

    2010-05-01

    Thermal water exploitation is widespread, because it is considered to a "green" renewable energy source, the transporter of the Earth crust's heat. It is suitable for very diverse purposes: balneology, heating, mineral water, municipal hot water supply, technological water, etc. After usage, large amount of thermal water becomes sewage water with high concentrations of salts, heavy metals, ammonia, nitrate, and high temperature. Besides that, most of these waters have an unfavourable ion composition. Na+ (and in some cases Mg+) is predominant among cations. A common way of treatment is to let off the waste thermal water in unlined ground channels to leak into the soil. This can cause physical and chemical soil degradation. Continouos Na+ supply occurs, that occupies the place of Ca2+ on the ion exchange surfaces. Thus, adverse effects of Na+ can appear, like formation of extreme moisture regime, peptization, liquefaction. Beside Na+, Mg2+ also helps the formation of physical degradation in the soil. High water retain and unfavourable structure evolves. Not only the physical features of the soil are touched, fertility of production sites as well. Namely sorrounding the unlined ground channels, agricultural areas are seated, so it is important to protect productivity of the soil to maintain yield. Because of the seepage of high salt concentration waters, salt accumulation can be observed near to the channel lines. The investigated sample sites are located in the Great Hungarian Plane. We determined the main pollutants of the thermal waters, and the effects to the sorrounding soils. On two selected investigation areas (Cserkesz?l?, Tiszakécske) salt profiles and Na+ adsorption isotherms are presented to characterize soil degradation. Genetic soil types are differ on the investigated areas, so the aspect of impact is different, as well.

  13. Availability of Fenamiphos and its Metabolites to Soil Water

    PubMed Central

    Davis, R. F.; Wauchope, R. D.; Johnson, A. W.

    1994-01-01

    Field and greenhouse experiments were conducted to determine the extent to which fenamiphos and its degradation products, fenamiphos sulfoxide and fenamiphos sulfone, are available to contact nematodes in the soil. Water extraction provided a relative measure of each chemical's availability to the soil water where the chemicals could contact nematodes, and methanol extraction provided a relative measure of the total amount of each chemical present in the soil. Only small amounts of fenamiphos and fenamiphos sulfone could be extracted by water, even when much larger amounts were present in the soil. In contrast, virtually all of the fenamiphos sulfoxide present in the soil was extractable by water several days after nematicide application. Three days after fenamiphos (3EC) was applied at 6.7 kg a.i./ha to field plots, 6.4% of the fenamiphos, 14.4% of the fenamiphos sulfone, and 100% of the fenamiphos sulfoxide present in the soil was extracted by water. In greenhouse experiments with soil from these field plots, a 15G formulation of fenamiphos containing 98.7% fenamiphos and 1.3% fenamiphos sulfoxide was added to the soil. After an initial period of 3-4 days, the sulfoxide which formed by oxidation of fenamiphos became completely available for water extraction, whereas fenamiphos remained relatively unextractable by water. Fenamiphos sulfoxide is much more available to soil water, thus available for contact with nematodes, than are fenamiphos or fenamiphos sulfone. Based on this availability in water, it seems likely that fenamiphos sulfoxide is the major component for controlling nematodes. PMID:19279923

  14. 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...

  15. 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 marked decrease in water permeability at 0.04, 0.20, or 0.40 m depth. Soil isotope profiles indicated that percolation beneath the root zone and groundwater recharge ranges from 21.7 mm/y to 29.7 mm/y. The recharge rate was positively related to mean annual rainfall and soil organic matter, and interestingly, increased with aridity and desertification. The difference between mean annual rainfall and percolation was positively related to plant cover and in inverse proportion to the aridity index. Our results highlight the importance of combining different methods of site characterization by soil physics, soil water isotopes and soil water chemistry (chloride) with vegetation data, providing a more specific analysis of ecohydrological conditions and their relation to ecosystem functioning and recovery potential. The field protocol applied can provide relevant information for guiding restoration strategies. Costantini, E. A. C., Urbano, F., Aramini, G., Barbetti, R., Bellino, F., Bocci, M., & Tascone, F. (2009). Rationale and methods for compiling an atlas of desertification in Italy. Land Degradation & Development, 20(3), 261-276. Garvelmann, J., Külls, C., & Weiler, M. (2012). A porewater-based stable isotope approach for the investigation of subsurface hydrological processes. Hydrology and Earth System Sciences, 16(2), 631-640.

  16. Settlement of soil due to water uptake by plant roots

    NASA Astrophysics Data System (ADS)

    Mathur, Shashi

    1999-10-01

    The settlement of soil occurs whenever there is an increase in effective confining stress. The withdrawal of water by plant roots results in a change in water pressure and moisture content in the soil. The variation in the moisture content leads to a change in the effective stress that causes a decrease in porosity which eventually results in the settlement of soil. The driving force for the uptake of water by the roots is the difference in the plant water and soil water potential existing between the soil solution adjacent to the roots and the root xylem. In case of transpiring plants, this driving force is mainly due to the tension (negative pressure) produced in the roots. A finite element solution of the governing equation yields the variation of moisture content with depth and the total settlement of the soil column due to the extraction of water by the plant roots. The simulated results indicate the damaging situation due to changes in the soil moisture content on account of transpiring trees and plants grown around the perimeter of structures.

  17. Vegetation Dynamics and Soil Water Balance in a Water-limited Mediterranean Ecosystem on Sardinia, Italy

    NASA Astrophysics Data System (ADS)

    Montaldo, N.; Albertson, J. D.; Mancini, M.

    2007-12-01

    Semi-arid regions, such as around the Mediterranean, suffer from broad desertification processes produced by both natural and human influences. Mediterranean ecosystems are commonly heterogeneous savanna-like ecosystems, with contrasting plant functional types (PFTs, e.g., grass and woody vegetation) competing for the water use. At the same time the structure and function of the vegetation regulates the exchange of mass, energy and momentum across the biosphere-atmosphere interface, influencing strongly the soil water budget. With the objective to investigate vegetation dynamics, soil water budget and land-surface fluxes interactions in a water-limited ecosystem, an extensive field campaign in a Mediterranean water-limited field is performed, and a parsimonious and robust vegetation dynamic model (VDM) is coupled to a 3-component (bare soil, grass and woody vegetation) LSM. The case study is in Orroli, situated in the mid-west of Sardegna within the Flumendosa river watershed. Sardinia is a region that suffers from water scarcity, and the Flumendosa basin plays a primary role in the water supply for much of southern Sardinia, including the island's biggest city, Cagliari. The site landscape is a mixture of Mediterranean patchy vegetation types: trees, including wild olives and cork oaks, different shrubs and herbaceous species. An extensive field campaign started in April 2003. More than three years of data are available. Interestingly, hydrometeorological conditions of the monitored years strongly differ, with dry and wet years in turn, and a wide range of hydrometeorological conditions can be analyzed. Land-surface fluxes and CO2 fluxes are estimated by an eddy correlation technique based micrometeorological tower. Soil moisture profiles were also continuously estimated using water content reflectometers and gravimetric method, and periodically leaf area index (LAI) estimates of both plant types are made using the Accupar LP-80 by Decagon Devices Inc. Furthermore, two high spatial resolution (2.8 m) Quickbird satellite images were acquired in August of 2003 and March 2004 for defining the spatial organization of the main land cover types around the tower for two contrasting seasons of the year (Summer and Spring). A parsimonious ecohydrologic model is developed. The VDM computes the change in biomass over time as difference between the rate of production (e.g., photosynthesis) and the rate of destruction (e.g., respiration and senescence). VDM incorporates two PFTs using basic rules regarding competition for a limiting resource. The VDM is then coupled to a 3-component LSM, with the VDM providing the green biomass and the LAI evolution through time, and the LSM using this information in the computation of the land surface fluxes and updating the soil water content in the root-zone. The coupled VDM-LSM model is successfully tested for the case study, demonstrating high model performance for the wide range of eco-hydrologic conditions. The inclusion of the VDM in the LSM is demonstrated to be essential when studying the climate-soil-vegetation interactions of these water-limited ecosystems. Results demonstrate also that vegetation dynamics are strongly influenced by the inter-annual variability of atmospheric forcing, with grass leaf area index changing significantly each spring season according to seasonal rainfall amount.

  18. Can soil surface sealing be a natural compensation mechanism for soil water loss under future dry conditions?

    NASA Astrophysics Data System (ADS)

    Sela, Shai; Svoray, Tal; Assouline, Shmuel

    2013-04-01

    Physical sealing of the soil is a widespread natural process in bare soil patches between shrubs, occurring frequently in dry environments. The seal layer has significantly lower hydraulic conductivity than the underlying undisturbed soil and thus it affects significantly hydrological fluxes. The presence of seal layer has been shown previously to be a negative feedback for vegetation water availability by reducing infiltration which leads to runoff initiation and consequently, propagation of desertification processes. The seal layer, however, has also shown a positive feedback, disregarded previously, resulting from suppressed evaporation fluxes from the soil which can have a much broader impact and affect water budget of dry areas at the regional scale. This positive feedback is studied in this research with model-based analysis of both measured local climatic records and synthetic climate change scenarios. The hillslope site (0.05 KM2) is located at the LTER Lehavim site, in the Negev desert at the south of Israel (31020' N, 34045' E). Annual rainfall is 290 mm and the soils are brown lithosols and arid brown loess, prone to surface sealing. The vegetation is characterized by scattered dwarf shrubs with dominant species Sarcopoterium spinosum. A previously published, high resolution physically-based model (aggregated Hydrus 1D runs) was used. The model (3X3 m2, 8240 cells) accounts explicitly for topographic and soil hydraulic parameters. Hydraulic properties of the seal layer at the soil surface were modeled following Mualem and Assouline (1989). Simulation of measured climate records reveals the seal layer to be a positive feedback for root zone water availability during dry and averaged rainfall seasons, while being a negative feedback during higher than average rainfall amounts (increasing the mean water content in the root zone, relatively to an unsealed profile, by 39%, 19% and -11% respectively). To study the seal layer role in future drier conditions, as projected by climate models for the Mediterranean region, the hydrological model was forced with a series of synthetic rainfall storms, systematically varying the drying intervals, evaporation intensity and soil initial water content conditions. Compared to an unsealed system, the presence of a seal layer was found to be an efficient water conservation mechanism, "buffering" the effect of climatic scenarios. For the drying intervals duration of 7 and 10 days (corresponding for the averages drying intervals during an average and dry seasons), water content at the root zone under the seal was found to be 17% and 20% higher, respectively. Furthermore, the seal layer effect on root zone water storage was found to be spatially heterogeneous, as the seal layer interacts differently with local topographic parameters.

  19. MODELING SPATIAL-TEMPORAL SOIL WATER AND OVERLAND FLOW IN A DRYLAND WHEAT-FALLOW FIELD USING MARIA-GIS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Crop production and environmental fluxes vary in space and time and over a range of scales in agricultural systems. Process interactions between soil hydrology, plant growth and development, nutrient cycling and chemical transport are tightly coupled such that the soil water dynamics reflect the cr...

  20. 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.

  1. 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...

  2. 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...

  3. 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...

  4. 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.

  5. 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.

  6. 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 at least 45% and soil loss by at least 59% in relation to an abandoned and degraded soil (bare soil) (Garcia-Estringana et al., 2010a). D. pentaphyllum, M. strasseri and C. arborescens were more effective in reducing runoff and soil loss (at least 83% and 97% respectively) than R. sphaerocarpa (45% and 59% respectively). Pisctacia Lentiscus L reduced the soil losses in 87% and the runoff rates (68%) meanwhile Quercus coccifera L reached a larger reduction (95% and 88 %) in comparison to herbicide treated agriculture soil. So, all shrub species protected the soil, but not in the same way. In relation to rainfall reaching the soil surface, great differences were observed among species, with interception losses varying between 10% for R. sphaerocarpa to greater than 36% for D. pentaphyllum and M. strasseri, and with stemflow percentages changing between less than 11% for D. pentaphyllum and M. strasseri and 20% for R. sphaerocarpa (Garcia-Estringana et al., 2010b). Rainfall interception on Pistacia Lentiscus and Quercus coccifera were 24% and 34% respectively for the two years of measurements. The integration of the effects of Mediterranean shrub vegetation on soil protection and rainfall partitioning fluxes facilitates understanding the effects of changes in vegetation type on soil and water resources. From this perspective, the interesting protective effect of D. pentpahyllum and M. strasseri, reducing intensely runoff and soil loss contrasts with the dangerous reduction in rainfall reaching the soil surface. Soil protection is essential in semiarid and arid environments, but a proper assessment of the effects on water availability is critical because of water is a scant resource in these kinds of environments. Pistacia Lentiscus and Quercus coccifera shown both a high capacity to intercept rainfall, increase infiltration and reduce the soil losses. We suggest to apply similar research programs into recently fire affected land as the role of vegetation after the fire is very dynamic (Cerdà 1998b). Acknowledgements The research projects 07 M/0077/1998, 07 M/0023/

  7. Survey of Microbial Enzymes in Soil, Water, and Plant Microenvironments

    PubMed Central

    Alves, Priscila Divina Diniz; Siqueira, Flávia de Faria; Facchin, Susanne; Horta, Carolina Campolina Rebello; Victória, Júnia Maria Netto; Kalapothakis, Evanguedes

    2014-01-01

    Detection of microbial enzymes in natural environments is important to understand biochemical activities and to verify the biotechnological potential of the microorganisms. In the present report, 346 isolates from soil, water, and plants were screened for enzyme production (caseinase, gelatinase, amylase, carboxymethyl cellulase, and esterase). Our results showed that 89.6% of isolates produced at least one tested enzyme. A predominance of amylase in soil samples, carboxymethyl cellulase in plants, as well as esterase and gelatinase in water was observed. Interesting enzymatic profiles were found in some microenvironments, suggesting specificity of available nutrients and/or natural selection. This study revealed the potential of microorganisms present in water, soil, and plant to produce important enzymes for biotechnological exploration. A predominance of certain enzymes was found, depending on the type of environmental sample. The distribution of microbial enzymes in soil, water and plants has been little exploited in previous reports. PMID:24847390

  8. Water and Solute Flow in a Highly-Structured Soil 

    E-print Network

    Hallmark, C. Tom; Wilding, Larry P.; McInnes, Kevin J.; Heuvelman, Willem J.

    1993-01-01

    Prevention of groundwater contamination by agricultural activities is a high priority in the United States. Water and contaminants often follow particular flow paths through the soil that lead to rapid movement of pesticides out of the rootzone...

  9. 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.

  10. 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.

  11. Simulation of the soil water balance of an undeveloped prairie in west-central Florida

    USGS Publications Warehouse

    Bidlake, W.R.; Boetcher, P.F.

    1996-01-01

    A one-dimensional numerical model was developed to simulate the soil water balance of a densely vegetated prairie site in west-central Florida. Transient simulations of the soil water balance were performed using field-measured soil and vegetation properties. Simulated and measured soil water content generally agreed to within 0.04; however, simulated water storage and recharge were sensitive to air-entry soil-water pressure potential and depth to the water table.

  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. Water Transfer from Soil to the Atmosphere as Related to Climate and Soil Properties 

    E-print Network

    Wendt, C. W.

    1970-01-01

    /sec. Conductivity Studies - The conductivity of the Olton loam soil is very low at fairly low soil water pressures corresponding to high contents. This is an asset in preventing evaporation losses, but may be detrimental to crop production in that the crops need...

  14. Measurement and modeling of soil-water dynamics and evapotranspiration of drained peatland soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Natural peat soils serve as important sinks for nutrients, organic components, and water. Peat soils can pose major environmental problems when they are drained for agricultural production, which may change their role in the landscape from a sink to a source. To successfully restore and conserve pea...

  15. 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 ?g 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

  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. 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 79.2µM 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 5214mg/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

  18. Impact of interspecific interactions on antimicrobial activity among soil bacteria

    PubMed Central

    Tyc, Olaf; van den Berg, Marlies; Gerards, Saskia; van Veen, Johannes A.; Raaijmakers, Jos M.; de Boer, Wietse; Garbeva, Paolina

    2014-01-01

    Certain bacterial species produce antimicrobial compounds only in the presence of a competing species. However, little is known on the frequency of interaction-mediated induction of antibiotic compound production in natural communities of soil bacteria. Here we developed a high-throughput method to screen for the production of antimicrobial activity by monocultures and pair-wise combinations of 146 phylogenetically different bacteria isolated from similar soil habitats. Growth responses of two human pathogenic model organisms, Escherichia coli WA321 and Staphylococcus aureus 533R4, were used to monitor antimicrobial activity. From all isolates, 33% showed antimicrobial activity only in monoculture and 42% showed activity only when tested in interactions. More bacterial isolates were active against S. aureus than against E. coli. The frequency of interaction-mediated induction of antimicrobial activity was 6% (154 interactions out of 2798) indicating that only a limited set of species combinations showed such activity. The screening revealed also interaction-mediated suppression of antimicrobial activity for 22% of all combinations tested. Whereas all patterns of antimicrobial activity (non-induced production, induced production and suppression) were seen for various bacterial classes, interaction-mediated induction of antimicrobial activity was more frequent for combinations of Flavobacteria and alpha- Proteobacteria. The results of our study give a first indication on the frequency of interference competitive interactions in natural soil bacterial communities which may forms a basis for selection of bacterial groups that are promising for the discovery of novel, cryptic antibiotics. PMID:25389421

  19. 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

  20. 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

  1. Stochastic estimation of plant-available soil water under fluctuating water table depths

    NASA Astrophysics Data System (ADS)

    Or, Dani; Groeneveld, David P.

    1994-12-01

    Preservation of native valley-floor phreatophytes while pumping groundwater for export from Owens Valley, California, requires reliable predictions of plant water use. These predictions are compared with stored soil water within well field regions and serve as a basis for managing groundwater resources. Soil water measurement errors, variable recharge, unpredictable climatic conditions affecting plant water use, and modeling errors make soil water predictions uncertain and error-prone. We developed and tested a scheme based on soil water balance coupled with implementation of Kalman filtering (KF) for (1) providing physically based soil water storage predictions with prediction errors projected from the statistics of the various inputs, and (2) reducing the overall uncertainty in both estimates and predictions. The proposed KF-based scheme was tested using experimental data collected at a location on the Owens Valley floor where the water table was artificially lowered by groundwater pumping and later allowed to recover. Vegetation composition and per cent cover, climatic data, and soil water information were collected and used for developing a soil water balance. Predictions and updates of soil water storage under different types of vegetation were obtained for a period of 5 years. The main results show that: (1) the proposed predictive model provides reliable and resilient soil water estimates under a wide range of external conditions; (2) the predicted soil water storage and the error bounds provided by the model offer a realistic and rational basis for decisions such as when to curtail well field operation to ensure plant survival. The predictive model offers a practical means for accommodating simple aspects of spatial variability by considering the additional source of uncertainty as part of modeling or measurement uncertainty.

  2. Comparing temporal and spatial change of pore water pressure and slope stability between wet soil condition and unsaturated soil condition

    NASA Astrophysics Data System (ADS)

    Kim, Dongyeob; Im, Sangjun; Lee, Eun Jai; Ahn, Byungkyu

    2013-04-01

    Intense rainfall event during short duration is the most significant reason of landslide in South Korea. Typically, it increases pore water pressure in soil and reduces soil effective stress, which cause landslide. In rainfall-induced landslide, saturation rate of soil at initial condition can affect whether landslide occurs. The objective of this study is to compare temporal and spatial pore water pressure and slope stability between in wet soil and in unsaturated soil under same rainfall condition. Two different infiltration models of TRIGRS 2 (Fortran Program for Transient Rainfall Infiltration and Grid-Based Regional Slope-Stability Analysis) were employed to analyze difference of pore water pressure and soil stability under different soil initial conditions. The study site was two small watersheds of Mt. Umyeon in South Korea, where several landslides occurred under an extreme rainfall event on July 27, 2011. Topographical data were generated based on 1 m x 1 m-LiDAR data, and parameters of soil and water characteristics were measured in-situ for TRIGRS 2 simulation. In addition, soil water characteristic curve of the site for the unsaturated soil condition was estimated by the pressure plate method and the filter paper method. The simulation results showed that pore water pressure differently responded between the different water conditions of soil. Ground water table rise appeared relatively faster and higher in the wet soil condition than in the unsaturated soil condition. Moreover, in the wet soil condition, pore water pressure increased with depth while in the unsaturated soil condition, vertical distribution of pore water pressure varied in time. In terms of slope stability, lower factor of safety (FS) were estimated in the wet soil condition than in the unsaturated soil condition. Comparing with landslide initiation positions in reality, FS were calculated more reasonably in the wet soil condition while FS were under-estimated in the unsaturated soil condition. These results indicate that estimating accurate initial water condition of landslide site is important for assessing landslide susceptibility.

  3. [Soil nitrogen and organic matter losses under water erosion].

    PubMed

    Zhang, X; Shao, M

    2000-04-01

    The results of artificial water-scoured experiment show that with the increase of water-scoured intensity, the losses of nitrate and ammonium in runoff, and those of organic matter and total N in sediment increased greatly, while the enrichment ratios of organic matter and total N in sediment reduced correspondingly. When the soils in gully-hilly loess region were fertilized with same amount of NH4NO3, the ammonium and nitrate loss in runoff was respectively 0.9-3.5% and 8.2-19.7% of the application amount. Nitrate mainly lossed in runoff, not in sediment. The correlation coefficient of soil erosion module, organic matter and total N loss with > 20 microns soil aggregates was -0.8935, -0.7928 and -0.8151, respectively. The content of > 20 microns soil aggregates could be used as an index to differentiate the soil organic matter and total N loss. PMID:11767602

  4. 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.

  5. Edward A. Hanlon Professor of Soil and Water Science (70% Extension, 30% Teaching)

    E-print Network

    Balser, Teri C.

    , Soil and Water Science Department, University of Florida 19841988, Assistant Professor, Soil and Water Science Department, University of Florida Expertise Soil and water issues, focusing on nutrientEdward A. Hanlon Professor of Soil and Water Science (70% Extension, 30% Teaching) Education B

  6. Soil water utilization by herbaceous species of the southern Great Plains: evidence from isotopically labeled water 

    E-print Network

    Yoder, Carolyn Kay

    1993-01-01

    Understanding spatial and temporal patterns of soil water utilization by plants has broad implications for physiological, ecological, and hydrological processes. Water labeled with the stable isotopes deuterium ('H) or oxygen-18 ("'O) was injected...

  7. Stochastic Dynamics of Plant-Water Interactions

    E-print Network

    Oren, Ram

    University, Durham, North Carolina 27708-0328; email: gaby@duke.edu Annu. Rev. Ecol. Evol. Syst. 2007. 38:767-water interactions. 767 Annu.Rev.Ecol.Evol.Syst.2007.38:767-791.Downloadedfromarjournals.annualreviews.org by

  8. Soil water nitrate and ammonium dynamics under a sewage effluent irrigated eucalypt plantation.

    PubMed

    Livesley, S J; Adams, M A; Grierson, P F

    2007-01-01

    Managed forests and plantations are appropriate ecosystems for land-based treatment of effluent, but concerns remain regarding nutrient contamination of ground- and surface waters. Monthly NO3-N and NH4-N concentrations in soil water, accumulated soil N, and gross ammonification and nitrification rates were measured in the second year of a second rotation of an effluent irrigated Eucalyptus globulus plantation in southern Western Australia to investigate the separate and interactive effects of drip and sprinkler irrigation, effluent and water irrigation, irrigation rate, and harvest residues retention. Nitrate concentrations of soil water were greater under effluent irrigation than water irrigation but remained <15 mg L(-1) when irrigated at the normal rate (1.5-2.0 mm d(-1)), and there was little evidence of downward movement. In contrast, NH4-N concentrations of soil water at 30 and 100 cm were generally greater under effluent irrigation than water irrigation when irrigated at the normal rate because of direct effluent NH4-N input and indirect ammonification of soil organic N. Drip irrigation of effluent approximately doubled peak NO3-N and NH4-N concentrations in soil water. Harvest residue retention reduced concentrations of soil water NO3-N at 30 cm during active sprinkler irrigation, but after 1 yr of irrigation there was no significant difference in the amount of N stored in the soil system, although harvest residue retention did enhance the "nitrate flush" in the following spring. Gross mineralization rates without irrigation increased with harvest residue retention and further increased with water irrigation. Irrigation with effluent further increased gross nitrification to 3.1 mg N kg(-1) d(-1) when harvest residues were retained but had no effect on gross ammonification, which suggested the importance of heterotrophic nitrification. The downward movement of N under effluent irrigation was dominated by NH4-N rather than NO3-N. Improving the capacity of forest soils to store and transform N inputs through organic matter management must consider the dynamic equilibrium between N input, uptake, and immobilization according to soil C status, and the effect changing microbial processes and environmental conditions can have on this equilibrium. PMID:17965391

  9. Soil-Earthquake Interactions in Buyukada/ Prinkipo (Istanbul)

    NASA Astrophysics Data System (ADS)

    Ozcep, Ferhat; Karabulut, Savas; Caglak, Faruk; Ozel, Oguz

    2014-05-01

    As the largest one of the nine islands comprising the Princes' Islands in the Marmara Sea, close to Istanbul, Buyukada ("Large Isle") consist of with an area of 5.46 km2. The main factor controlling the earthquake hazard for Istanbul is a complex fault system, i.e. the North Anatolian Fault zone, which in the Marmara Sea region. Recent geophysical studies have carried out that this hazard is mainly associated within two active seismogenic areas: the Central Marmara Basin and the Adalar Fault zone, located about 15-30 km south-west and south of Istanbul. Eartquake ground motion affects the structures via the state of the soils. There are several historical buildings on Büyükada, such as the Ayia Yorgi Church and Monastery dating back to the sixth century, the Ayios Dimitrios Church, and the Hamidiye Mosque built by Abdul Hamid II and Greek Orphanage, a huge wooden building etc. The soils and buildings with characteristics of earthquakes could be caused an earthquake damage / loss. One of the most important factors in reducing the earthquake risk in urban areas due to the earthquake ground motion is to estimate gound motion level with interaction of soils. When we look at the geological structure of Buyukada, Paleozoic unites and alluvial deposit are located. Site response of alluvial deposits in Buyukada is also important for the behavior during an earthquake. Geophysical study in the study area in order to estimate the behavior of soils is carried out to obtain the dominant period (microtremor measurements) and shear wave velocity ( MASW - MAM measurements) data. Soil geophysical results is input to earthquake motion for bedrock sites, and is important to the interaction with the ground movement and the soils to estimate Büyükaada's earthquake ground motion. In the earthquake-soil interaction, spectral acceleration is an important criterion. In this study, spectral acceleration are also estiamted for ground motion level in Princes' Islands by using several approaches.

  10. 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

  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, we conclude that elevated CO2, air warming, and changing soil water availability had both direct and indirect effects on soil respiration via changes in the three controlling factors: soil temperature, soil moisture, and C substrate. Our results demonstrate that the response of soil respiration to climatic warming should not be represented in models as a simple temperature response function. A more mechanistic understanding of the direct and indirect impacts of concurrent global change drivers on soil respiration is needed to facilitate the interpretation and projection of ecosystem and global C cycling in response to atmospheric and climate change.

  12. [Characteristics of soil water movement using stable isotopes in red soil hilly region of northwest Hunan].

    PubMed

    Tian, Ri-Chang; Chen, Hong-Song; Song, Xian-Fang; Wang, Ke-Lin; Yang, Qing-Qing; Meng, Wei

    2009-09-15

    Stable isotope techniques provide a new approach to study soil water movement. The process of water movement in soils under two kinds of plant types (oil tea and corn) were studied based on the observed values of hydrogen and oxygen isotopes of precipitation and soil water at different depths in red-soil sloping land. The results showed that stable isotopes of precipitation in this area had obvious seasonal effect and rainfall effect. The stable isotopes at 0-50 cm depth in oil tea forestland and at 0-40 cm depth in corn cropland increased with the increase in depth, respectively, but they had the opposite tendency after rainfall in arid time. The stable isotopes decreased with the increase in depth below 50 cm depth in oil tea forestland and below 40 cm depth in corn cropland where evaporation influence was weak. The infiltrate rate of soil in oil tea land was affected by precipitation obviously, and it was about 50-100 mm/d after 2-3 days in heavy rain, slowed sharply later, and soil water at 50 cm depth often became a barrier layer. The permeability of soil in corn land was poor and the infiltration rate was lower. The change of stable isotopes in soil water in red soil hilly region was mainly affected by the mixing water which was formed by the antecedent precipitation, and evaporation effect took the second place. The evaporation intensity in oil tea land was lower than that in corn land, but the evaporation depth was higher. PMID:19927835

  13. 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.

  14. 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.

  15. Salinity control in a clay soil beneath an orchard irrigated with treated waste water in the presence of a high water table: A numerical study

    NASA Astrophysics Data System (ADS)

    Russo, David; Laufer, Asher; Bardhan, Gopali; Levy, Guy J.

    2015-12-01

    A citrus orchard planted on a structured, clay soil associated with a high water table, irrigated by drip irrigation system using treated waste water (TWW) and local well water (LWW) was considered here. The scope of the present study was to analyze transport of mixed-ion, interacting salts in a combined vadose zone-groundwater flow system focusing on the following issues: (i) long-term effects of irrigation with TWW on the response of the flow system, identifying the main factors (e.g., soil salinity, soil sodicity) that control these effects, and (ii) salinity control aiming at improving both crop productivity and groundwater quality. To pursue this two-fold goal, 3-D numerical simulations of field-scale flow and transport were performed for an extended period of time, considering realistic features of the soil, water table, crop, weather and irrigation, and the coupling between the flow and the transport through the dependence of the soil hydraulic functions, K(?) and ?(?), on soil solution concentration C, and sodium adsorption ratio, SAR. Results of the analyses suggest that in the case studied, the long-term effect of irrigation with TWW on the response of the flow system is attributed to the enhanced salinity of the TWW, and not to the increase in soil sodicity. The latter findings are attributed to: (i) the negative effect of soil salinity on water uptake, and the tradeoff between water uptake and drainage flux, and, concurrently, solute discharge below the root zone; and, (ii) the tradeoff between the effects of C and SAR on K(?) and ?(?). Furthermore, it was demonstrated that a data-driven protocol for soil salinity control, based on alternating irrigation water quality between TWW and desalinized water, guided by the soil solution salinity at the centroid of the soil volume active in water uptake, may lead to a substantial increase in crop yield, and to a substantial decrease in the salinity load in the groundwater.

  16. Soil water retention curve of agrogray soils: Influence of anisotropy and the scaling factor

    NASA Astrophysics Data System (ADS)

    Umarova, A. B.; Shein, E. V.; Kukharuk, N. S.

    2014-12-01

    The soil water characteristic or soil water retention curve (WRC) of medium-loamy gray forest soil horizons was studied in cylinder-shaped samples of disturbed and undisturbed structure. The sample height varied within 2-4 cm and the diameter within 4.5-10 cm. The soil monoliths were sampled in three profiles: vertically, along the slope, and across the slope in accordance with the intrasoil paleorelief formed by the funnel-shaped surface of the second humus horizon. The experimental WRC were approximated with the van Genuchten equation. The statistical analysis of the WRc approximation parameters proved to differ significantly in filled soil samples and monoliths, and a number of parameters differ for samples of the maximal height and diameter. The reliable differences of the parameters were also noted for the different sampling directions, most often, for those across the paleorelief slope. The noted variation in the WRC approximation parameters may substantially influence the predictive estimation of the spring water reserve for example. This fact suggests the necessity to strictly indicate the sampling procedure, in particular, with respect to the soil profile, the asymmetry in the soil properties, and the sample sizes (scaling factor) used for analyzing the hydrological properties of structured soils.

  17. 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...

  18. Water Repellency, Infiltration and Water Retention Properties of Forest Soils Under Different Management Practices

    NASA Astrophysics Data System (ADS)

    Wahl, N. A.; Bens, O.; Schäfer, B.; Hüttl, R. F.

    For soils under both agricultural and forest use, management and tillage practice can have significant influence on the hydraulic properties. It is therefore supposed, that management practices are capable of altering surface runoff, water retention and flood- ing risk for river catchments. Soil water repellency (hydrophobicity) can adversely affect soil hydrological properties, e.g. reduce infiltration capacity and induce pref- erential flow, thus enhancing the overall risk of flooding in river catchment areas. Hydrophobic effects are especially pronounced in coniferous forest soils. Investigations were carried out on several study plots in the German Northeastern Lowlands, located app. 50 km NE of Berlin in Brandenburg. Soils found in the area are mainly of glacifluvial origin with a pronounced sandy texture (with medium sized sand dominating). The four stands investigated represent different stages of forest transfor- mation, in a sense of a SfalseT chronosequence and are made up of populations of & cedil;Pinus sylvestris and Fagus sylvatica of different ages. Infiltration was measured with hood infiltrometers, and single infiltration rings at soil surface. Water retention capacity and the influence of soil organic matter on water storage were evaluated with laboratory methods. Water repellency was quantified with the water drop penetration time (WDPT) test, for determining the persistence of water repellency, and the ethanol percentage (EP) test, for measuring the severity/degree of water repellency. Soil samples from the four forest plots and different soil depths (0U160 cm) were used for the measurements. SPotentialT water repellencies were & cedil;determined after 3-day oven-drying at 45 C. The results indicate that for sandy forest soils, the overall infiltration capacity of the plots is low due to the effects of water repellency. The inter-variability of the plots is mainly caused by changes in the textural composition of the soils. For all plots a significant proportion of severely and extremely hydrophobic samples in the upper 10 cm of the soil profile was revealed, whereas the persistence of repellency decreases with increasing soil depth. The EP exhibit for all plots a shallower depth distribution than the WDPT. During forest transformation, both humus type as well as humus distribution in the soil and the litter layers are altered. These changes influence above 1 all the water storage capacity of the soil which declines considerably during the first stage of forest transformation. The obtained results will be incorporated in a hydrologic catchment model in order to evaluate the possible impact on the runoff characteristics. Simulated runoff data for selected mesoscale catchments (e.g. of the Rhine area) will serve to evaluate different soil management practices in terms of minimizing surface runoff and preventing flood events. 2

  19. Numerical Simulation of Soil Water Content in the Unsaturated Zone Using Constraints Provided by Geophysical Measurements

    NASA Astrophysics Data System (ADS)

    Hou, Z.; Rubin, Y.; Hubbard, S. S.

    2002-12-01

    Soil moisture distribution and variation in the vadose zone is important for agricultural, engineering and contaminant studies. Conventional sampling techniques for estimating soil water moisture content are costly, time consuming, invasive, and typically recover information at a single point in space and time only. Geophysical techniques have the potential to provide dense and accurate information about subsurface soil moisture. However, these data still provide information about water content at the time of measurement only, and geophysical data acquisition is sometimes hindered by cultural or site conditions. For example, although both surface and crosshole GPR techniques have been successfully applied for providing soil moisture information over space and time, the penetration distance of the GPR signal is limited in soils having high electrical conductivity, sometimes inhibiting moisture profiling through the entire vadose zone. In this study, we investigate the potential of coupling geophysical measurements with numerical modeling to provide information about soil moisture variations in space and over time. Such an approach was undertaken to permit estimation of soil moisture throughout the root zone even under difficult GPR data acquisition conditions, and also to yield insight into the dynamics of soil water distribution, including both state variables and fluxes. In this study, surface and crosshole geophysical measurements provide initial and boundary soil moisture conditions to a numerical simulator (TOUGH2-EOS9) based on Richard­_s Equation. Simulations were run using information available from various geophysical techniques collected at a naturally heterogeneous agricultural field site, including surface GPR, crosshole GPR, neutron probe, and TDR measurements. Information about soil heterogeneity was obtained using borehole soil textural information, and meteorological water flux boundary conditions were obtained using rain gauges, sap flow meters and also from a nearby CIMIS weather station. Hydraulic conductivity, one of the most difficult field variables to measure, can be satisfactorily estimated using a stochastic inverse modeling approach. Comparison of soil moisture measurements (collected throughout a year at a field site near Napa, CA) with the various simulations suggested that the approach was able to capture the natural evolution of the vadose zone soil moisture profile at several locations throughout the heterogeneous site. These results illustrate that improvement in the understanding of water cycling and its interaction with ecosystems can be obtained by coupling hydrological theory and measurements available from geophysical and meteorological techniques.

  20. 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

    Studying the effects of polyacrylamide (PAM) on soil aggregate and structure stability is important in developing effective soil and water conservation practices and in sustaining soil and water quality. Five concentrations of an anionic PAM (0, 25, 50, 100 and 200 mg L-1) with a high molecular weight were tested on loam and clay soils having either a predominant smectitic or kaolinitic clay mineralogy. The effects of the PAM and of soil texture on soil water retention at near saturation and on aggregate and structure stability were investigated using the high energy moisture characteristic (HEMC) method. The S-shaped water retention curves obtained by the HEMC method were characterized by the modified van Genuchten (1980) model that provided: (i) the model parameters ? and n, which represent the location of the inflection point and the steepness of the water retention curve, respectively; and (ii) the soil structure index, SI =VDP/MS, where VDP is the volume of drainable pores, an indicator of the quantity of water released by a soil over the range of applied suctions (0-5 J kg-1), and MS is the modal suction representing the most frequent pore sizes (> 60 ?m). In general, the treatments tested (clay mineralogy, soil type and PAM concentration) resulted in: (i) a considerable modification of the shape of the water retention curves as indicated by the changes in the ? and n values; and; (ii) substantial effects on the stability indices and other model parameters. The contribution of PAM concentration to soil structure stability depended on the clay mineralogy, being more effective in the smectitic soils than in the kaolinitic ones. Although kaolinitic soils are usually more stable than smectitic soils, when the latter were treated with PAM (25-200 mg L-1) the opposite trend was observed. In the loam soils, increasing the PAM concentration notably decreased the differences between values of the stability indices of the smectitic and kaolinitic samples. The 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.

  1. 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 the prediction of the potential mechanical behaviour of soil crusts generated during soil drying, from initial saturated soil conditions (e.g. waterlogging conditions).

  2. Improving Estimates of Root-zone Soil Water Content Using Soil Hydrologic Properties and Remotely Sensed Soil Moisture

    NASA Astrophysics Data System (ADS)

    Baldwin, D. C.; Miller, D. A.; Singha, K.; Davis, K. J.; Smithwick, E. A.

    2013-12-01

    Newly defined relationships between remotely sensed soil moisture and soil hydraulic parameters were used to develop fine-scale (100 m) maps of root-zone soil moisture (RZSM) content at the regional scale on a daily time-step. There are several key outcomes from our research: (1) the first multi-layer regional dataset of soil hydraulic parameters developed from gSSURGO data for hydrologic modeling efforts in the Chequemegon Ecosystem Atmospheric Study (ChEAS) region, (2) the operation and calibration of a new model for estimating soil moisture flow through the root-zone at eddy covariance towers across the U.S. using remotely sensed active and passive soil moisture products, and (3) region-wide maps of estimated root-zone soil moisture content. The project links soil geophysical analytical approaches (pedotransfer functions) to new applications in remote sensing of soil moisture that detect surface moisture (~5 cm depth). We answer two key questions in soil moisture observation and prediction: (1) How do soil hydrologic properties of U.S. soil types quantitatively relate to surface-to-subsurface water loss? And (2) Does incorporation of fine-scale soil hydrologic parameters with remotely sensed soil moisture data provide improved hindcasts of in situ RZSM content? The project meets several critical research needs in estimation of soil moisture from remote sensing. First, soil moisture is known to vary spatially with soil texture and soil hydraulic properties that do not align well with the spatial resolution of current remote sensing products of soil moisture (~ 50 km2). To address this, we leveraged new advances in gridded soil parameter information (gSSURGO) together with existing remotely sensed estimates of surface soil moisture into a newly emerging semi-empirical modeling approach called SMAR (Soil Moisture Analytical Relationship). The SMAR model was calibrated and cross-validated using existing soil moisture data from a portion of AMERIFLUX tower sites and the NRCS Soil Climate Analysis Network (SCAN). Our preliminary results show good performance of the SMAR model for predicting RZSM at the site level (root mean square error = 0.04). Second, a calibrated SMAR parameter governing the surface to subsurface rate of water flow was related to soil hydraulic properties at the AMERIFLUX tower sites, and region-wide maps of SMAR parameters were developed for the ChEAS region using gSSURGO information. Finally, region-wide maps of RZSM were developed and validated for the ChEAS region. The RZSM products can be directly incorporated with regional CO2 flux modeling, and the results inform - but are not dependent on - efforts that integrate observed soil moisture data with planned NASA missions (e.g., SMAP).

  3. Prion protein interaction with soil humic substances: environmental implications.

    PubMed

    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

  4. 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

  5. Soil water content and green water estimations in a small farmed semiarid catchment

    NASA Astrophysics Data System (ADS)

    Mekki, I.; Voltz, M.; Ben Mechlia, N.; Albergel, J.

    2012-04-01

    The main objective of this work is to analyze the spatial and temporal variation of soil water content and green water production over a farmed water harvesting catchment, located in north-eastern Tunisia. The area has a typical Mediterranean climate with a hot dry summer and a cool season, extending from October to April, where rainfall normally meets the water requirements of the usually grown cereals and legumes (500mm). The catchment has an area of 2.6 km2 and comprises at its outlet a dam, which retains the runoff water in a reservoir. Soil water balance measurements were carried out, about weekly, over two successive cropping cycles (2000-2002) on a network of eleven plots of 2 m2 each, representing the main land use and soil types. Soil water store investigations targeted the different individual plots as well as the entire catchment. We used a simple water balance model, where the root zone is considered as a single reservoir, to simulate soil water content variations. Results show a fairly good agreement between the calculated and measured water store for all experimental sites. The model reproduces accurately the soil water content during the beginning of the rainy season but underestimates it during the season when heavy rains occur. On heavy soils, simulated soil moisture was lower than measured values, giving differences as high as 25% between simulated water store amounts and the neutron probe measurement values. For the cereals/legume/pasture based cropping systems, most of rainfall water is stored in the soil and returns to the atmosphere by evapotranspiration. The 0-0.3 m soil layer is most active for water uptake by crops and intermittent replenishment by rainfall during the growing period; whereas drying involves the entire soil profile over the summer season (May-Seeptmber). The available water holding capacity of the soil turned out to be about seven times the storage capacity of the reservoir, showing the order of magnitude of rainfall partitioning between green water and blue water for cropped catchments, under semiarid arid climates.

  6. 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...

  7. INFORMATION CONTENT AND COMPLEXITY OF SIMULATED SOIL WATER FLUXES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The accuracy-based performance measures may not suffice to discriminate among soil water flow models. The objective of this work was to attempt using information theory measures to discriminate between different models for the same site. The Richards equation-based model HYDRUS-1D and a water budget...

  8. 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…

  9. 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

  10. 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 following a controlled water application where the study areas were isolated from other water inputs and outputs. We will also report on the assessment of two soil water sensors (Decagon Devices 5TM capacitance probe and UMS T4 tensiometers) for the two soil textural classes in terms of consistency and replicability.

  11. 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 efficiency for water exhibits a concave upward relationship with initial water saturation in clay, whereas a positively-correlated relationship between the efficiency and initial water saturation is observed in silt, loam, and sand.

  12. Since Iceland was settled 1100 y ago, declines in vegetated land cover has been accompanied by severe wind and water erosion. Interaction of

    E-print Network

    Archer, Steven R.

    by severe wind and water erosion. Interaction of four reinforcing factors appears to have contributed to the erosion problem: soil (Andisol) properties, cold climate, vegetation poorly adapted to herbivory susceptible to erosion (Figure 1). The high soil water holding capacity causes them to expand when soils

  13. 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...

  14. Measuring and Modeling Interactions Between Groundwater, Soil Moisture, and Plant Transpiration in Natural and Agricultural Ecosystems

    E-print Network

    Rubin, Yoram

    Measuring and Modeling Interactions Between Groundwater, Soil Moisture, and Plant Transpiration Transpiration in Natural and Agricultural Ecosystems © 2009 by Gretchen Rose Miller #12;1 Abstract Measuring and Modeling Interactions Between Groundwater, Soil Moisture, and Plant Transpiration in Natural

  15. Surfactant-enhanced remediation of organic contaminated soil and water.

    PubMed

    Paria, Santanu

    2008-04-21

    Surfactant based remediation technologies for organic contaminated soil and water (groundwater or surface water) is of increasing importance recently. Surfactants are used to dramatically expedite the process, which in turn, may reduce the treatment time of a site compared to use of water alone. In fact, among the various available remediation technologies for organic contaminated sites, surfactant based process is one of the most innovative technologies. To enhance the application of surfactant based technologies for remediation of organic contaminated sites, it is very important to have a better understanding of the mechanisms involved in this process. This paper will provide an overview of the recent developments in the area of surfactant enhanced soil and groundwater remediation processes, focusing on (i) surfactant adsorption on soil, (ii) micellar solubilization of organic hydrocarbons, (iii) supersolubilization, (iv) density modified displacement, (v) degradation of organic hydrocarbon in presence surfactants, (vi) partitioning of surfactants onto soil and liquid organic phase, (vii) partitioning of contaminants onto soil, and (viii) removal of organics from soil in presence of surfactants. Surfactant adsorption on soil and/or sediment is an important step in this process as it results in surfactant loss reduced the availability of the surfactants for solubilization. At the same time, adsorbed surfactants will retained in the soil matrix, and may create other environmental problem. The biosurfactants are become promising in this application due to their environmentally friendly nature, nontoxic, low adsorption on to soil, and good solubilization efficiency. Effects of different parameters like the effect of electrolyte, pH, soil mineral and organic content, soil composition etc. on surfactant adsorption are discussed here. Micellar solubilization is also an important step for removal of organic contaminants from the soil matrix, especially for low aqueous solubility organic contaminants. Influences of different parameters such as single and mixed surfactant system, hydrophilic and hydrophobic chain length, HLB value, temperature, electrolyte, surfactant type that are very important in micellar solubilization are reviewed here. Microemulsion systems show higher capacity of organic hydrocarbons solubilization than the normal micellar system. In the case of biodegradation of organic hydrocarbons, the rate is very slow due to low water solubility and dissolution rate but the presence of surfactants may increase the bioavailability of hydrophobic compounds by solubilization and hence increases the degradation rate. In some cases the presence of it also reduces the rate. In addition to fundamental studies, some laboratory and field studies on removal of organics from contaminated soil are also reviewed to show the applicability of this technology. PMID:18154747

  16. Water distribution at the root-soil interface: is there more water next to roots?

    NASA Astrophysics Data System (ADS)

    Carminati, A.; Moradi, A.; Oswald, S.; Vetterlein, D.; Weller, U.; Vogel, H.-J.

    2009-04-01

    Plants are big water movers and have a significant impact on soil water dynamics as well as on the global water cycle. Despite the relevance of root water uptake in terrestrial ecology, the movement of water from soil to roots still presents important open questions, e.g the following two. Which are the properties of the soil near the roots? And what effect do these properties have on soil plant water relations? Most models are based on brute-force spatial averaging of soil properties and assume that the bulk soil has the same properties as the rhizosphere. However, there is evidence in the literature that the rhizosphere has specific properties that may affect water and nutrient uptake (Young 1995, Gregory 2007). In order to investigate the rhizosphere hydraulic properties and their effect on soil plant water relations, we used neutron radiography and neutron tomography to image the water content distribution in soils during plant transpiration. Rectangular (quasi-2D) and cylindrical containers were filled with sandy soil and planted with lupins (Lupinus albus). Three weeks after planting, the samples were equilibrated at water potentials of -10 and 30 hPa and have been imaged for 5 days at intervals of 6 hours. At day 5 the samples were irrigated again via capillary rise and the water distribution was monitored for 4 more days. During the first day of the drying period, regions of water depletion formed around the central part of the tap root where first order laterals were present. As the soil dried up, the picture changed: instead of less water around the roots, as commonly supposed by models, we observed that more water was present around the lateral roots. Interestingly, these regions during drying were retaining high water content, but after irrigation remained markedly drier than the bulk soil. Our hypothesis is that high water content near roots during drying and lower water content during rewetting are explained by the presence of bio-polymers exuded by roots forming a hydrogel that consists of up to 99% water at very negative water potentials (Read et al. 1999). Thanks to its high water holding capacity, this hydrogel maintains a continuous hydraulic pathway across soil and roots for an extended period of time during drying. During rewetting it adversely affects water redistribution, like a storage that needs time to fill up again. These data show for the first time in situ the potential role of mucilage in controlling water dynamics in the rhizosphere and consequences for plant water extraction. Gregory P J, Roots, rhizosphere and soil: the route to a better understanding of soil science? European Journal of Soil Science, 57: 2-12, 2006. Read D P, Gregory P J, and Bell A E. Physical properties of axenic maize root mucilage. Plant and Soil, 211: 87-91, 1999. Young I M. Variation in moisture contents between bulk soil and the rhizosheath of wheat. New Phytologist, 130: 135-139, 1995.

  17. Spatio-temporal variability of soil water content on the local scale in a Mediterranean mountain area (Vallcebre, North Eastern Spain). How different spatio-temporal scales reflect mean soil water content

    NASA Astrophysics Data System (ADS)

    Molina, Antonio J.; Latron, Jérôme; Rubio, Carles M.; Gallart, Francesc; Llorens, Pilar

    2014-08-01

    As a result of complex human-land interactions and topographic variability, many Mediterranean mountain catchments are covered by agricultural terraces that have locally modified the soil water content dynamic. Understanding these local-scale dynamics helps us grasp better how hydrology behaves on the catchment scale. Thus, this study examined soil water content variability in the upper 30 cm of the soil on a Mediterranean abandoned terrace in north-east Spain. Using a dataset of high spatial (regular grid of 128 automatic TDR probes at 2.5 m intervals) and temporal (20-min time step) resolution, gathered throughout a 84-day period, the spatio-temporal variability of soil water content at the local scale and the way that different spatio-temporal scales reflect the mean soil water content were investigated. Soil water content spatial variability and its relation to wetness conditions were examined, along with the spatial structuring of the soil water content within the terrace. Then, the ability of single probes and of different combinations of spatial measurements (transects and grids) to provide a good estimate of mean soil water content on the terrace scale was explored by means of temporal stability analyses. Finally, the effect of monitoring frequency on the magnitude of detectable daily soil water content variations was studied. Results showed that soil water content spatial variability followed a bimodal pattern of increasing absolute variability with increasing soil water content. In addition, a linear trend of decreasing soil water content as the distance from the inner part of the terrace increased was identified. Once this trend was subtracted, resulting semi-variograms suggested that the spatial resolution examined was too high to appreciate spatial structuring in the data. Thus, the spatial pattern should be considered as random. Of all the spatial designs tested, the 10 × 10 m mesh grid (9 probes) was considered the most suitable option for a good, time-stable estimate of mean soil water content, as no improvement was obtained with the 5 × 5 m mesh grid (30 probes). Finally, the results of temporal aggregation showed that decreasing the monitoring frequency down to 8 h during wetting-up periods and to 1 day during drying-down ones did not result in a loss of information on daily soil water content variations.

  18. Soil and Water Science Department soils.ifas.ufl.edu

    E-print Network

    Ma, Lena

    and agricul- tural produce.We will also discuss in detail the efficacy of water quality tests during routine and limitations of several culture-dependent methods to identify coliforms. Demonstration exercises will also test and recreation areas. Lectures, discussions and hands-on laboratory exercises will build on your expertise

  19. 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...

  20. 78 FR 56153 - National Environmental Policy Act: Categorical Exclusions for Soil and Water Restoration Activities

    Federal Register 2010, 2011, 2012, 2013, 2014

    2013-09-12

    ...Act: Categorical Exclusions for Soil and Water Restoration Activities AGENCY: Forest...that restore lands negatively impacted by water control structures, disturbance events...potential environmental effects of soil and water restoration projects that are...

  1. 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

  2. SCALING IN SOIL AGGREGATE DISTRIBUTION AS DEPENDENT ON AGGREGATE WATER CONTENT AND SOIL COMPACTION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fractal scaling has been documented in literature for mass of dry soil aggregates. Changes in water content are known to cause shrinking or swelling in aggregates. The objective of this work was to determine (a) whether the fractal scaling will hold for aggregates at various water contents, (b) how ...

  3. 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 lectures, real field visits and other learning activities on soil sciences. The development of these programmes has been sponsored by the Spanish Ministry of Science and Innovation (Fundación Española para la Ciencia y la Tecnología, FECYT) and it has won the "Félix de Azara" Award (2011). Çaliskan, O. (2011). Virtual field trips in education of earth and environmental sciences. Procedia Social and Behavioral Sciences, 15: 3229-3243. Churchman, G. J. (2010). The philosophical status of soil science. Geoderma 157, 214-221. European Commission (2006). Thematic strategy for soil protection. COM (2006) 231. Field D.J., A. J. Koppi, L. E. Jarrett, L. K. Abbott, S. R. Cattle, C. D. Grant, A. B. McBratney, N. W. Menzies, A. J. Weatherley (2011). Soil Science teaching principles. Geoderma, 167-168: 9-14. IUSS Working Group WRB (2007). World Reference Base for Soil Resources 2006, fist update 2007. World Soil Resources Reports n° 103. FAO. Rome.

  4. Name ___________________________________________ Soil, Water and Forage Testing Laboratory

    E-print Network

    to 40 acres. A separate sample should be taken for: Areas with different soil types Areas with different land uses or fertilizer uses Areas with different terrain Approximately 1 pint of the composite field depressions, terrace waterways, or unusual areas. When sampling fertilized fields, avoid sampling

  5. Name ___________________________________________ Soil, Water and Forage Testing Laboratory

    E-print Network

    .D. Represented fertilizer analyses used? 1 2 3 4 5 6 7 8 9 10 Grazing (G) G&H Hay (H) **Min. requirement for every 10 to 40 acres. A separate sample should be taken for: Areas with different soil types Areas with different land uses or fertilizer uses Areas with different terrain Approximately 1 pint of the composite

  6. ESTIMATING SOIL WATER CONTENT USING COKRIGING

    EPA Science Inventory

    Using cokriging, estimates and estimation variances of the gravimetric moisture content (GMC) were made using one and two additional random functions: the bare soil surface temperature and the percent sand content. Various measures of the differences and quality of the estimates ...

  7. SOIL, WATER, AND CLIMATE MS DEFENSE SEMINAR

    E-print Network

    Minnesota, University of

    site is located at the headwaters of a county ditch system established in 1908, but historical relative to groundwater depth and physical profiles of drained organic soils with moorsh characteristics. Maximum height of groundwater in the peatland is closely correlated to the maximum depth of moorsh

  8. 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 between pH and Zn (r = -0.61).

  9. College of Agricultural and Life Sciences UNDERGRADUATE DEGREE OPTIONS IN SOIL & WATER SCIENCE

    E-print Network

    Hill, Jeffrey E.

    major undergraduate Soil and Water Science Department at the University of Florida Visit us online atCollege of Agricultural and Life Sciences UNDERGRADUATE DEGREE OPTIONS IN SOIL & WATER SCIENCE Soil/MS 5-year Program Graduate Degrees: Masters, Doctoral, and Distance Programs soil and water science

  10. Modeling the effect of antecedent soil water storage on water and heat status in seasonally freezing and thawing agricultural soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Taking Hetao Irrigation District of Inner Mongolia's agricultural production as a background and based on field observation data and field measured meteorological data, the influence of antecedent soil water storage (ASWS) on water and heat conditions was simulated and analyzed using the SHAW model ...

  11. Using radium isotopes as tracers of transfers in the soil - water- -plant system

    NASA Astrophysics Data System (ADS)

    Rihs, S.; Pierret, M.-C.; Chabaux, F.

    2012-04-01

    Because soils form at the critical interface between the lithosphere and the atmosphere, characterization of the dynamics occurring through this compartment represents an important goal for several scientific fields and/or human activities. However, this issue remains a challenge because soils are complex systems, where a continuous evolution of minerals and organic soil constituents occurs in response to interactions with waters and vegetation. This study aims to investigate the relevance of short-lived nuclides of U- and Th-series to quantify the transfer times and scheme of radionuclides through a soil - water - plant ecosystem. Activities of (226Ra), (228Ra) as well as (228Th) were measured by TIMS and gamma-spectrometry in the major compartments of a forested soil section: solid soil fractions (exchangeable fraction, secondary phases and inherited primary minerals), waters (seepage soil waters and a spring further down the watershed) and vegetation (fine and coarse roots of beech trees, young and mature leaves). The matching of these nuclides half-live to bio-geochemical processes time-scale and the relatively good chemical analogy of radium with calcium make these isotopes especially suitable to investigate either time or mechanism of transfers within a soil-water-plant system. Indeed, the (228Ra/226Ra) isotopic ratios strongly differ in the range of samples, allowing quantifying the source and duration transfers. Analyses of the various solid soil fractions demonstrate a full redistribution of Ra isotopes between the inherited minerals and secondary soil phases. Moreover, the transfer of these isotopes to the seepage water or to the tree roots does not follow a simple and obvious scheme. The radium isotopic ratio in the trees roots does not match the soil exchangeable fraction, suggesting a mixed pool of radium for roots uptake. Decay of 228Ra within the various parts of the trees allows calculating a vegetation cycling duration of about 12 years for this nuclide. Finally an unexpected large amount of unsupported 228Th in the tree leaves can only be explained by a preferential migration of the 228Ac (228Th precursor). The very short life of this nuclide allows therefore assessing that such transport from roots and deposition within stem and leaves take place within 30 hours at the most.

  12. 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 modifies the natural conditions and the total natural system must be successfully blended with the unnatural stresses placed upon it. This can be accomplished by introducing new methods (such as ground-water zoning) in and by developing alternative strategies for ground-water management and protection. ?? 1983 D. Reidel Publishing Company.

  13. 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

  14. 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.

  15. Soil Moisture: The Hydrologic Interface Between Surface and Ground Waters

    NASA Technical Reports Server (NTRS)

    Engman, Edwin T.

    1997-01-01

    A hypothesis is presented that many hydrologic processes display a unique signature that is detectable with microwave remote sensing. These signatures are in the form of the spatial and temporal distributions of surface soil moisture. The specific hydrologic processes that may be detected include groundwater recharge and discharge zones, storm runoff contributing areas, regions of potential and less than potential evapotranspiration (ET), and information about the hydrologic properties of soils. In basin and hillslope hydrology, soil moisture is the interface between surface and ground waters.

  16. 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.

  17. Priming and substrate quality interactions in soil organic matter models

    NASA Astrophysics Data System (ADS)

    Wutzler, T.; Reichstein, M.

    2012-12-01

    Interactions between different qualities of soil organic matter (SOM) affecting their turnover are rarely represented in models. In this study we propose three mathematical strategies at different levels of abstraction for representing those interactions. Implementing these strategies into the Introductory Carbon Balance Model (ICBM) and applying them to several scenarios of litter input show that the different levels of abstraction are applicable on different time scales. We present a simple one-parameter equation of substrate limitation applicable at decadal time scale that is straightforward to implement into other models of SOM dynamics. We show how substrate quality interactions can explain priming effects, acceleration of turnover times in FACE experiments, and the slowdown of decomposition in long-term bare fallow experiments as an effect of energy limitation of microbial biomass. The mechanisms of those interactions need to be further scrutinized empirically for a more complete understanding. Overall, substrate quality interactions offer a valuable way of understanding and quantitatively modelling SOM dynamics.

  18. Priming and substrate quality interactions in soil organic matter models

    NASA Astrophysics Data System (ADS)

    Wutzler, T.; Reichstein, M.

    2013-03-01

    Interactions between different qualities of soil organic matter (SOM) affecting their turnover are rarely represented in models. In this study, we propose three mathematical strategies at different levels of abstraction to represent those interactions. By implementing these strategies into the Introductory Carbon Balance Model (ICBM) and applying them to several scenarios of litter input, we show that the different levels of abstraction are applicable at different timescales. We present a simple one-parameter equation of substrate limitation that can straightforwardly be implemented into other models of SOM dynamics at decadal timescale. The study demonstrates how substrate quality interactions can explain patterns of priming effects, accelerate turnover in FACE experiments, and the slowdown of decomposition in long-term bare fallow experiments as an effect of energy limitation of microbial biomass. The mechanisms of those interactions need to be further scrutinized empirically for a more complete understanding. Overall, substrate quality interactions contribute to both understanding and quantitatively modelling SOM dynamics.

  19. 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

  20. 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 measured within a month after the tillage operations (951.0 mm h-1). However, the positive effect of tillage was only temporary, since the lowest mean Kfs was obtained in the tilled plot, for the undisturbed soil conditions, namely when measurements were carried out long time after the execution of tillage operations (107.6 mm h-1). Significant differences between the hydraulic conductivity measured inside the track and outside the track positions were found both in the grass covered and in the tilled vineyard's inter-rows. The results of the investigation show that, in the specific area of study, the maintenance of grass cover in the vineyard inter-rows gives higher water infiltration than tillage throughout the year.

  1. 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-occurring feedbacks between the soil carbon and water cycles, and may enable agriculture biotechnology that enhances natural soil processes for improved resiliency of terrestrial ecosystems.

  2. Soil water retention dynamics in Luvisols at contrasting slope positions in lysimeter monoliths from an eroded soil landscape

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

    Modeling water flow and solute transport in variably saturated soils requires the proper description of the soil water retention curve. The problem is that under field conditions, water retention may be hysteretic or otherwise changing in time due to changing soil properties. In arable soil landscapes, these changes may depend on the erosion history which created spatial patterns of soil properties such as texture and organic matter content and differences in crop development. The objective of this study was to analyze the dynamics in field-measured water retention data for Luvisols in 10 cm, 30 cm and 50 cm soil depth (Ap, E, and Bt horizons) at two contrasting at slope positions characterized by different degrees of soil erosion under intensive agricultural cultivation. Drying and wetting water retention was obtained from tensiometer/MPS and TDR data in depths representing same soil horizons. For comparison, we used drying retention data obtained from soil cores using the evaporation method (Hyprop). Drying data were fitted to the unconstrained water retention function proposed by van Genuchten (1980) and the bimodal model of Durner (1994). For wetting data, hydraulic model parameters were determined by using the Pedroso-Williams model (2010). The water contents of wetting and drying branches were dynamically changing. These changes in water retention were different for several horizons of the more eroded Luvisol as compared to the less eroded one. Differences in water retention dynamics could be related to soil tillage and the erosion history at the different slope positions. The water differences in retention could be explained by hysteresis and temporal changes in soil water repellency. Field and lab retention data differed as reported earlier. The results suggest that estimation of soil water retention curves without resorting to time-consuming field measurements remains challenging. The results suggest that for erosion-affected arable soils of the hummocky landscape, the soil water retention dynamics is spatially distributed and depending on the erosion gradient.

  3. Sy estimation from paralel soil moisture and water table measurement

    NASA Astrophysics Data System (ADS)

    Gribovszki, Zoltán; Kalicz, Péter

    2015-04-01

    In growing season evapotranspiration induces diurnal signal of soil moisture, and also of water table in shallow water table environments. Diurnal signal of water table was widespreadly used for estimation of groundwater uptake by plants. The limitation of all groundwater signal based methods lies in the difficulty of specific yield (Sy) estimation. This is a soil water storage parameter that strongly depends on both, the unsaturated soil moisture fluxes (recharge and evapotranspiration) and water table elevation. Based on parallel soil moisture profile and water table measurements in a hydrophyte forest of Hidegvíz Valley experimental catchment at the eastern foothills of the Alps subdaily Sy values were calculated. Estimated Sy values are significantly changed along the day. If you want to get accurate Sy value for ET estimation a representative period has to be selected within the day. For analysis Sy values were calculated as a late night average and as a daily average as well. Estimated Sy values were compared to the results of some traditional Sy estimation techniques (particle distribution curve based, moisture characteristic curve based, etc.). Penman-Monteith reference evapotranspiration was used for evaluation of the ET values calculated from different Sy estimations. This research has been supported by the AGRARKLIMA.2 VKSZ_12-1-2013-0034 project.

  4. Interactive effects of vegetation, soil moisture and bulk density on depth of burning of thick organic soils

    E-print Network

    Turetsky, Merritt

    Interactive effects of vegetation, soil moisture and bulk density on depth of burning of thick consumption. We experimentally altered soil moisture profiles of peat monoliths collected from several (Johnstone and Chapin 2006; Benscoter and Vitt 2008; Johnstone et al. 2010), soil moisture and temperature

  5. Interactive effects of vegetation, soil moisture and bulk density on depth of burning of thick organic soils

    E-print Network

    Benscoter, Brian W.

    PROOF ONLY Interactive effects of vegetation, soil moisture and bulk density on depth of burning consumption. We experimentally altered soil moisture profiles of peat monoliths collected from several (Johnstone and Chapin 2006; Benscoter and Vitt 2008; Johnstone et al. 2010), soil moisture and temperature

  6. 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 study, while the Flumendosa basin is characterized by soils of different type and depth (more silty and deep nearly the river valley), such as typical in Mediterranean basins. A sensitivity analysis to the soil depth and soil type is performed for investigating their influences on the PFT dynamics and soil water balance. The influence of vegetation cover distribution of each plant type is also investigated. Results show that the plant compete differently according to site soil characteristics, and the impact of vegetation dynamics on the soil water balance terms is significant and cannot be neglected in current hydrological approaches.

  7. 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.

  8. Irrigation Monitoring with Soil Water Sensors 

    E-print Network

    Enciso, Juan; Porter, Dana; Peries, Xavier

    2007-01-19

    .6?8.0 Vegetables Carrots Cantaloupes and watermelons Lettuce Onions Potatoes Sweet Peppers Zucchini and cucumbers 35 40?45 30 30 65 30 50 1.5?3.3 2.6?5.0 1.0?1.6 2.0?3.0 1.0?2.0 1.6?3.2 2.0?4.0 *Root depths can be affected by soil and other conditions. Effective...

  9. Experiments and modeling of mobility and interaction of heavy metals in a natural soil

    NASA Astrophysics Data System (ADS)

    Sanchez-Vila, X.; Bianchi Janetti, E.; Dror, I.; Riva, M.; Guadagnini, A.; Berkowitz, B.

    2012-12-01

    Health and environmental impacts of heavy metals are associated mostly with dissolved ions. Understanding of ion partitioning between solid and aqueous phases is therefore critical. We study the mobility and interaction of copper (Cu2+) and zinc (Zn2+) ions in laboratory-scale, natural soil columns. The experiments focus on the analysis of breakthrough curves obtained after simultaneous injection of an aqueous solution containing the two metal ions into a column packed with water-saturated soil. The soil columns are tested under aerobic and anaerobic conditions to assess the effect of redox conditions on metal mobility. The measurements show that the two metals compete for the available adsorption sites. The weaker ion (Zn2+) has lower affinity with the soil and is replaced by the stronger one (Cu2+) after a preliminary adsorption. We interpret this observed behavior by means of different models based on a set of coupled partial differential and algebraic equations, involving both aqueous and adsorbed species. Depending on the model considered, the relationship between aqueous and adsorbed ion concentrations is described by an equilibrium Gaines-Thomas formulation, a competitive Sheindorf-Rebhun-Sheintuch (SRS) isotherm, or a competitive Extended Langmuir isotherm. The system of governing equations is solved numerically and model parameters are calibrated against experimental measurements. Results show that the redox conditions can alter the capacity of the soil to retain cations migrating within the tested saturated natural soils. The Gaines-Thomas formulation best reproduces the observed behavior.

  10. 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.

  11. Separating Water Content Changes and Soil Texture Using Electromagnetic Induction Soil Imaging

    NASA Astrophysics Data System (ADS)

    Abdu, H.; Robinson, D. A.; Jones, S. B.

    2007-12-01

    The spatial distribution of soil texture is important for determining soil moisture storage and soil hydraulic transport properties. Electromagnetic induction (EMI) surveys of the soil apparent electrical conductivity (ECa) are being used to infer soil spatial heterogeneity at the field scale, due to their non-destructive nature, rapid response and ease of integration onto mobile platforms. The purpose of this study is to develop a procedure to non- invasively map field-scale soil texture patterns with minimal calibration and separate response due to water content change from static textural properties. Geo-referenced ECa measurements were taken using a DUALEM- 1S ground conductivity meter on multiple days with different field soil water contents on a 50 x 50 m field site at the Utah State University's Greenville Farm. Our results suggest that there are distinct zones with different textural properties and the lowest conductivity zone corresponds to observed gravelly area. Using temporal stability analysis these EMI maps reveal the spatial distribution of time-invariant subsurface properties and are informative for modeling and experimental design purposes in ecological, environmental and agricultural applications.

  12. Subsurface water flow simulated for hill slopes with spatially dependent soil hydraulic characteristics

    SciTech Connect

    Sharma, M.L.; Luxmoore, R.J.; DeAngelis, R.; Ward, R.C.; Yeh, G.T.

    1987-08-01

    Water flow through hill slopes consisting of five soil layers, with varying spatial dependence in hydraulic characteristics in the lateral plane was simulated by solving Richards' equation in three dimensions under varying rainfall intensities and for two complexities of terrain. By concepts of similar media the variability in soil hydraulic characteristics was expressed by a single dimensionless parameter, the scaling factor ..cap alpha... The moments of log normally distributed ..cap alpha.. were set as: Mean = 1.0 and standard deviation = 1.0. Four cases of spatial dependence of ..cap alpha.. in the lateral plane were selected for simulation, using exponential variogram functions ranging in spatial structure from random (no spatial dependence) to large dependence (large correlation lengths). The simulations showed that the rates of subsurface flow from the 30/sup 0/ hillslope, during and following rainfall, were significantly enhanced with an increase in spatial dependence. Subsurface drainage was also increased with increases in rainfall intensity and slop complexity. For hill slopes the relative effects of spatial dependence in soil hydraulic characteristics was smaller with 30/sup 0/ horizontal pitching than without pitching. Hill slopes with a random distribution of hydraulic characteristics provided greater opportunity for soil units with differing water capacities to interact than in cases with spatially correlated distributions. This greater interaction is associated with a greater lag in subsurface flow generation. These studies illustrate some of the expected effects of spatial dependence of soil hydraulic characteristics of the integrated hydrologic response of land areas.

  13. Grazing impacts on soil carbon fractions and soil water dynamics in subalpine ecosystems

    NASA Astrophysics Data System (ADS)

    Gill, R. A.

    2005-12-01

    The mountain lands of the intermountain west are vital to the wellbeing of human communities in the adjacent valleys, providing these communities with water, important summer forage for wildlife and domestic livestock, and possibly the sequestration of anthropogenic carbon. In this work, I build on a 90-year old grazing experiment in mountain meadows on the Wasatch Plateau in central Utah. Long-term grazing significantly reduced aboveground net primary production (ANPP) in all years compared with plots within grazing exclosures, even though these plots were not grazed during the study period. Livestock grazing had no impacts on total soil C or particulate organic matter stocks, although grazing did alter soil C chemistry and soil water dynamics. Grazing significantly increased the proportion of total soil C stocks that were potentially mineralizable in the laboratory. Volumetric soil moisture was consistently higher in ungrazed plots than grazed plots. In addition, there was a 0.5-1% increase in ^13C in grazed plots compared to paired ungrazed plots, supporting the conclusion that grazing significantly increases periods of water stress. Because grazing has resulted in an accumulation of easily decomposable organic material, if temperatures warm and summer precipitation increases as is anticipated, these soils may become net sources of carbon to the atmosphere creating a positive feedback between climate change and atmospheric CO2.

  14. Remote Sensing of Soil Surface Texture, Carbon and Water Contents using Bare Soil Imagery

    NASA Astrophysics Data System (ADS)

    Iqbal, J.; Owens, P. R.

    2005-12-01

    Knowledge of spatial soil diversity and landscape dynamics is fundamental to understanding of global biogeochemical cycles. Remote sensing data are increasingly being used for large-scale quantification of land-based measurements such as soil texture, carbon and water content. These regional estimates of surface soil properties through remote sensing can be used as input for global biogeochemical models. The objective of this study was to explore the relationship between bare soil reflectance and surface soil texture (sand, silt, and clay), organic matter, and soil moisture. High spatial (2 m) and spectral resolution (414-920 nm) hyperspectral /multispectral aerial imageries were collected over the Mississippi Delta and Mississippi Blackland Prairie Regions. Major soils included Commerce (fine-silty, mixed, superactive, nonacid, thermic Fluvaquentic Endoaquepts), Robinsonville (coarse-loamy, mixed, superactive, nonacid, thermic Typic Udifluvents), and Convent (coarse-silty, mixed, superactive, nonacid, thermic Fluvaquentic Endoaquepts) and Brooksville (Fine, smectitic, thermic Aquic Hapluderts). Over three hundred surface soil samples were collected within the study area and analyzed for particle size analysis, organic matter, moisture and hydraulic properties. ArcView GIS was used to generate sampling locations which included random, transect, and target soil sampling. Each soil sample represented a composite of six sub-samples collected within a two meter square area. These sample sites were selected to represent the range of aspect, slope, elevation, and parent materials within the site. To reduce the dimensionality of the hyperspectral data set, PCA analysis was applied. The selected bands were used in generating the statistical relationships between spectral reflectance and surface soil properties data. Stepwise (backward & forward) and partial least square statistical methods were used to generate surface maps of soil texture, organic matter, and surface soil moisture. The multivariate analysis including partial least squares and stepwise linear regression reveal that the near infrared band (NIR950 nm) was the best predictor of percent clay (R2 = 0.683) and silt (R2 = 0.634), while the combination of Red band (RED650 nm) and Green band (Green550 nm) were the best predictors of organic matter. Surface soil moisture dynamic was highly spatially correlated with soil texture maps. Once these relationships were established, ERDAS Imagine Spatial Module was used to generate surface maps for percent clay, percent silt and percent organic matter. These final products not only could be used for management purposes but also to quantify the spatial patterns and temporal dynamics of soils and their impact on climate change.

  15. 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

  16. 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.

  17. 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...

  18. 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.

  19. 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 ...

  20. 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.

  1. 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...

  2. 26 CFR 1.175-2 - Definition of soil and water conservation expenditures.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... of soil or water conservation in respect of land used in farming, or for the prevention of erosion of... of water, to check soil erosion on sloping land, to intercept runoff, and to divert excess water to... produce vegetation primarily to conserve soil or water or to prevent erosion. Thus, for example,...

  3. 40 CFR 280.65 - Investigations for soil and ground-water cleanup.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 26 2010-07-01 2010-07-01 false Investigations for soil and ground... Containing Petroleum or Hazardous Substances § 280.65 Investigations for soil and ground-water cleanup. (a... soil or ground water on nearby surface water and ground-water resources. (b) Owners and operators...

  4. Morphology of rain water channelization in systematically varied model sandy soils

    E-print Network

    Y. Wei; C. M. Cejas; R. Barrois; R. Dreyfus; D. J. Durian

    2014-03-13

    We visualize the formation of fingered flow in dry model sandy soils under different raining conditions using a quasi-2d experimental set-up, and systematically determine the impact of soil grain diameter and surface wetting property on water channelization 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 into 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 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 water infiltration depth, water channel width, and water channel separation. At a fixed raining condition, we combine the effects of grain diameter and surface hydrophobicity into a single parameter and determine its influence on water infiltration depth, water channel width, and water channel separation. We also demonstrate the efficiency of several soil water improvement methods that relate to rain water channelization phenomenon, including pre-wetting sandy soils at different level before rainfall, modifying soil surface flatness, and applying superabsorbent hydrogel particles as soil modifiers.

  5. 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.

  6. 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.

  7. 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

  8. 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...

  9. 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 produced ash has significant and not always constructive pedological, ecological, hydrological and geomorphological effects and impacts (Shakesby, 2011). Abundant scientific information is assembled either from control fires by collecting samples before and after wildfire event, or conducting laboratory experiments exanimating data under truly isolated conditions (Lugassi et al., 2013). However, an integration and synthesis of the knowledge about ash including deeper understanding of inter-correlation between chemical, physical and morphological compounds in open post-burn environment and its possible interactions in soil formation or impact on soil composition are highly needed. The main aim of the presented study was to advance the science of soil-fire relationship by recognizing the remains ash as a new soil-forming factor, on par with the traditionally recognized factors: parent material, topography, time, climate, organisms, and recently recognized human activity as the sixth factor. This research was conducted to develop new methods to assess impacts and quantify the contributions/influences of post-fire products, mainly ash, on soil composition and soil properties in post-burned environment. We conducted several controlled experiments using 40 soil samples (typical Mediterranean Rendzina soil, pH 6.84, a grayish-brown, humus- and free calcium carbonate- rich, intra-zonal). The samples include bare soils and different types and loads of forest litter, were exposed to different temperatures (200° C, 400° C and 600° C) in a muffle furnace for 2 hours (Pereira et al. 2011) as fire temperature plays a key role in determining ash properties. The ash produced at a low temperatures (50% carbon and retains many of the structural characteristics of the parent material. At higher temperatures, the residue ash is greyish, consisted of very fine particles that preserve almost none of the original structural characteristics of the fuel (Woods and Balfour, 2008) creating gradient of layered ash with diverse physicochemical properties. The obtained post-burned soils we

  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 ?13C (‰). Differences between individual ?13CPLFA and ?13CSOM 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. USING ENSEMBLES OF PEDOTRANSFER FUNCTIONS FOR SOIL WATER RETENTION IN FIELD-SCALE WATER FLOW SIMULATIONS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Using pedotransfer functions (PTF) to estimate soil hydraulic properties may be necessary in soil water flow simulations for large-scale projects or in pilot studies. The accuracy of a PTF outside of its development dataset is generally unknown. The existence of multiple models that are developed an...

  12. 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.

  13. 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 fluctuations in water content changes, with both root water uptake and root water excretion. The magnitude of the water content change was in the same order for all treatments, thus suggesting compensatory uptake. References Bakker G, Van der Ploeg MJ, de Rooij GH, Hoogendam CW, Gooren HPA, Huiskes C, Koopal LK and Kruidhof H. New polymer tensiometers: Measuring matric pressures down to the wilting point. Vadose Zone J. 6: 196-202, 2007. Blackman PG and Davies WJ. Root to shoot communication in maize plants of the effects of soil drying. J. Exp. Bot. 36: 39-48, 1985. Davies WJ and Zhang J. Root signals and the regulation of growth and development of plants in drying soil. Annu. Rev. Plant Physiol. Plant Mol. Biol. 42: 55-76, 1991. Gollan T, Passioura JB and Munns R. Soil water status affects the stomatal conductance of fully turgid wheat and sunflower leafs. Aust. J. Plant Physiol. 13: 459-464, 1986. Gowing DJG, Davies WJ and Jones HG. A Positive Root-sourced Signal as an Indicator of Soil Drying in Apple, Malus x domestica Borkh. J. Exp. Bot. 41: 1535-1540, 1990. Grace J. Environmental controls of gas exchange in tropical rain forests. In: Press, M.C, J.D. Scholes and M.G. Barker (ed.). Physiological plant ecology: the 39th Symposium of the British Ecological Society. Blackwell Science, United Kingdom, 1999. Kool D, Agam N, Lazarovitch N, Heitman JL, Sauer TJ, Ben-Gal A. A review of approaches for evapotranspiration partitioning. Agricultural and Forest Meteorology 184: 56- 70, 2014. Mansfield TA and De Silva DLR. Sensory systems in the roots of plants and their role in controlling stomatal function in the leaves. Physiol. Chem. Phys. & Med. 26: 89-99, 1994. Sadras VO and Milroy SP. Soil-water thresholds for the responses of leaf expansion and gas exchange: a review. Field Crops Res. 47: 253-266, 1996. Schröder N, Lazarovitch N, Vanderborcht J, Vereecken H, Javaux M. Linking transpiration reduction to rhizosphere salinity using a 3D coupled soil-plant model. Plant Soil 2013, doi: 10.1007/s11104-013-1990-8 Van der Ploeg MJ, Gooren HPA, Bakker G and de Rooij GH.

  14. 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 sequestration efficiency for Atrazine and Diuron while BC sorbed on the soils with lower CECs showed much higher Atrazine and Diuron sequestration efficiency than the other surfactants, suggesting that the sorbed BC on these soils with less CEC forms bulk-like partitioning media more easily than the soils with higher CECs. These results significantly improve our understanding of partitioning of pesticides within soil-water-surfactant systems. These findings can serve to improve the pesticide removal efficiency of soil washing systems. Also, our results show that by studying the effect of surfactants on pesticide sorption can serve as a new method to study pesticide sorption mechanisms.

  15. Root Water Uptake and Soil Water Dynamics in a Karst Savanna on the Edwards Plateau, TX 

    E-print Network

    Tokumoto, Ieyasu

    2013-05-09

    Woody plants are encroaching into a karst savanna on the Edwards Plateau in central Texas, but their impact on hydrology is unclear because of high variability in soil depth and uncertainties about shallow and deep root contributions to water uptake...

  16. 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) ?w=2?d, (2) nw=nd, and (3) ?ws=?ds, where ?, n, and ?s 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 ?w/?d for the data set was 2.24±1.25. Nominally cohesive soils had a lower ?w/?d 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 (?ws) was consistently less than during drying (?ds) owing to air entrapment. The ?ws/?ds 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.

  17. Coupled simulation of soil energy and water content to compare dielectric behaviour with TDR measurements in frozen soil

    NASA Astrophysics Data System (ADS)

    Muerth, Markus; Schlenz, Florian; Loew, Alexander; Mauser, Wolfram

    2010-05-01

    In the field of soil moisture monitoring both, on-site time domain reflectometry (TDR) methods and microwave remote sensing, measure the actual soil water content via the dielectric behavior of the soil-water-air mixture. Basically, the dielectric behavior is not only influenced by soil water content, but also by temperature, soil ice content, soil texture and porosity. However, many TDR and microwave techniques relate soil water content directly to soil dielectric behavior, because they lack the ability to determine the other relevant soil properties directly. The advantage of the combination of modeling and monitoring techniques for soil moisture monitoring is the ability to understand and compare spatial and temporal patterns, especially if other land surface properties influence the retrieved soil moisture signal. In this case, the hydrological land surface model PROMET (Processes of Mass, Energy and Radiation Transfer) is combined with TDR probe measurements taken at multiple sites and multiple depths during the winter 2008/2009 in south-eastern Germany. The harsh conditions, especially during January and February 2009 led to low measured liquid water contents in the upper 20 cm of the investigated soils, although the total water content remained nearly constant over time. Additionally, soil temperature and meteorological drivers were measured at nearby agrometeorological stations. Because PROMET has shown to simulate moisture content of non-frozen soils well, compared to TDR probe and remote sensing data, we investigate its ability to simulate frozen soil water content, when enhanced with an energy balance driven soil temperature module. Furthermore, a semi-empirical dielectric mixing model is implemented to directly compare the simulated soil dielectric behavior with the available TDR probe time series. It is shown that the explicit computation of the soil surface energy balance coupled with a physically based soil temperature model is able to simulate the freeze-thaw cycles within the top soil layers and may significantly enhance the prediction of the liquid soil water content compared to the available measurements. However, our study also shows, that the calculated dielectric behavior derived from simulated temperature and moisture with the dielectric mixing model does not compare well with the dielectricity values of the TDR time series. In fact, the range of potential dielectricity values of the two mixing models used for moisture calculation from TDR data and for the computation of dielectric behavior from model outputs respectively strongly differs. This indicates that the dielectric properties measured with TDR probes may not be adequate to validate a land surface model that computes soil dielectric behavior from temperature and moisture, although such models could be useful for inter-comparison with or assimilation of remote sensing data to better predict spatially explicit soil moisture fields.

  18. UF/IFAS Soil and Water Science 2181 McCarty Hall

    E-print Network

    Hill, Jeffrey E.

    Contact UF/IFAS Soil and Water Science 2181 McCarty Hall PO Box 110290 Gainesville, FL 32611 Phone: 352.294.3152 E-mail: mjsisk@ufl.edu soils.ifas.ufl.edu soil and water science major SOIL SCIENCE u n d e r g r a d u a t e SPECIALIZATION An Equal Opportunity Institution. UF/IFAS Soil and Water Science

  19. 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...

  20. DRIP FUMIGATION: WATER AND FUMIGANT DISTRIBUTION IN SOIL.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Drip fumigation with alternative fumigants to methyl bromide [1,3- dichloropropene (1,3-D), chloropicrin (Pic), methyl isothiocyanate (MITC), iodomethane (IM), and propargyl bromide (PrBr)] may provide a more uniform distribution of chemicals in the soil than shank injection. Water distribution and...

  1. 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...

  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. Speciation of ionic alkyllead in potable water and soil.

    PubMed

    Chakraborti, D; Dirkx, W; van Cleuvenbergen, R; Adams, F

    1989-08-01

    Various potable water and soil samples have been analyzed for tri- and dialkyllead compounds using a sensitive speciation procedure based on diethyldithiocarbamate extraction, Grignard derivatization and gas chromatography-atomic absorption spectrometry. The species are generally present as ultra-trace contaminants, and their abundance is critically discussed. In addition, a degradation study of ionic alkyllead in ambient matrices is presented. PMID:2772620

  4. 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...

  5. Soil and Water Conservation Advances in the Northern Great Plains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Advances in soil and water conservation techniques and practices in the northern Great Plains over the last century have altered present day crop production and agriculture. Homesteaders began settling the land in the late 1800’s and early 1900’s and brought with them implements they had used in hi...

  6. Soil and Water Conservation Advances in the Northern Great Plains

    Technology Transfer Automated Retrieval System (TEKTRAN)

    “Great American Desert” is what many maps often call the Great Plains of North America. This is where dryland agriculture practices for North America have their roots. The purpose of this part of the book was to determine the advances in soil and water conservation technology over the past century a...

  7. Estimation of soil water balance components using an iterative procedure

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Quantification of the hydrologic balance at high temporal resolution is necessary to evaluate field scale management effects on infiltration and soil water storage. Our objective was to develop and evaluate a hybrid procedure to estimate drainage, infiltration, and evaporation based on changes in pl...

  8. 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.

  9. FIELD CAPACITY OF WATER IN SOILS: CONCEPTS, MEASUREMENT, AND APPROXIMATION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    We propose to use field capacity as an operational concept for root zone water management, and avoid treating it as an intrinsic soil property. Field capacity is reached when downward drainage flux is negligibly small (while recognizing that drainage may not cease completely) so that evaporation and...

  10. Interaction effects of climate and land use/land cover change on soil organic carbon sequestration

    E-print Network

    Grunwald, Sabine

    Interaction effects of climate and land use/land cover change on soil organic carbon sequestration carbon sequestration Climate change Soil carbon change Historically, Florida soils stored the largest use/land cover impacted soil C sequestration. · Land use/land cover in FL changed significantly over

  11. 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.

  12. Particulate Organic Matter and Water Stable Aggregation of Soil Under Contrasting Management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil organic matter (SOM) is important to soil function. Objectives of our work were to determine effect of cropping rotation and soil management on SOM, components of SOM, and water stable aggregation (WSA) of soil near the surface. Measurements were made on soil collected from seven sites that rep...

  13. A new soil water and bulk eletrical conductivity sensor technology for irrigation and salinity management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Many soil water sensors, especially those based on electromagnetic (EM) properties of soils, have been shown to be unsuitable in salt-affected or clayey soils. Most available soil water content sensors are of this EM type, particularly the so-called capacitance sensors. They often over estimate and ...

  14. A Manual on Conservation of Soil and Water. Appropriate Technologies for Development. R-38.

    ERIC Educational Resources Information Center

    Peace Corps, Washington, DC. Information Collection and Exchange Div.

    In order to keep the land productive, a good conservation program is imperative. The primary purpose of soil and water conservation is to prevent soil erosion and heal its scars. This handbook explains the causes, processes, and consequences of soil erosion and depletion, and describes major soil- and water-conservation measures. This book was…

  15. Sensible Heat Measurements Indicating Depth and Magnitude of Subsurface Soil Water Evaporation

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water evaporation is typically determined by techniques that assume the latent heat flux originates from the soil surface. Here, we describe a new technique for determining in situ soil water evaporation dynamics from fine-scale measurements of soil temperature and thermal properties with heat ...

  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. Mapping soil resistance under different soil water content conditions using indicator kriging

    NASA Astrophysics Data System (ADS)

    Miras-Avalos, J. M.; Bonnin-Acosta, J.; Sande-Fouz, P.; Pereira-Lanças, K.; Paz-Gonzalez, A.

    2009-04-01

    In many agricultural problems, it is of interest to map the zones where the variable under study shows the probability of being greater than a threshold value. Soil resistances higher than 2 MPa might difficult the establishment of cultures; therefore, further management or tillage techniques should be undertaken. The aim of this work was to map soil resistance using geostatistical techniques, therefore, an analysis of the spatial distribution of soil compaction and the influence of soil water content on the resistance to penetration was carried out. The studied clay-textured soil was managed under no-tillage practices. Soil resistance was described by the cone index which was obtained using a penetrometer. This attribute was assessed at 5 different depths, i.e. 0-10 cm, 10-20 cm, 20-30 cm, 30-40 cm and deeper than 40 cm, whereas soil water content was described at 0-20 cm and 20-40 cm. In the end, 73 data points were surveyed. Soil water conditions varied during the five different samplings. Statistical analysis showed that datasets followed a normal distribution, therefore, no transformation was required. Studied attributes showed low and non-significant correlation coefficients which impeded the application of cross-variogram and cokriging techniques. Because of the limited number of measured data, only the omnidirectional semivariogram was computed, and hence the spatial variability is assumed to be identical in all directions. Spatial dependence was observed in 33 out of 35 data series, both for cone index and soil water content. Fitted theoretical structures corresponded to exponential models in 20 cases, 10 Gaussian models and 3 spherical models. Nugget effect varied from 0 to 44.4 depending on the dataset and spatial dependence maximum range was 90 m. A strong spatial dependence was observed in 18 of the data sets whereas only 2 showed a weak autocorrelation. Taking into account the 2 MPa threshold, indicator kriging was used to map the soil resistance distribution allowing the identification of site-specific management zones which permit the adoption of precision agriculture techniques, specifically, tillage practices. The application of these methodologies is discussed regarding the results of this analysis.

  18. Infiltration into cropped soils: effect of rain and sodium adsorption ratio-impacted irrigation water.

    PubMed

    Suarez, Donald L; Wood, James D; Lesch, Scott M

    2008-01-01

    The sodium adsorption ratio (SAR) and salinity criteria for water suitability for irrigation have been developed for conditions where irrigation water is the only water source. It is not clear that these criteria are applicable to environments where there is a combination of rain and irrigation during the growing season. The interaction of rainfall with irrigation water is expected to result in increased sodicity hazard because of the low electrical conductivity of rain. In this study we examined the effects of irrigation waters of SAR 2, 4, 6, 8, and 10 mmol(1/2) L(-1/2) and electrical conductivities of 1 and 2 dS m(-1) on the infiltration rate of two soils with alternating cycles of rain (simulated with a rainfall sprinkler) and irrigation water, separated by drying cycles. The infiltration rate of surface samples from two soils, Kobase silty clay (fine, smectitic, frigid, Torrertic Haplustept) and Glendive very fine sandy loam (coarse-loamy, mixed superactive, calcareous, frigid Aridic Ustifluvent) were evaluated under alfalfa (Medicago sativa) cropped conditions for over 140 d and under full canopy cover. Reductions in infiltration were observed for both soils for SAR above 2, and the reductions became more severe with increasing SAR. Saturated hydraulic conductivity measurements taken from undisturbed cores at the end of the experiment were highly variable, suggesting that in situ infiltration measurements may be preferred when evaluating SAR effects. PMID:18765763

  19. Subcritical Water Extraction of Amino Acids from Atacama Desert Soils

    NASA Technical Reports Server (NTRS)

    Amashukeli, Xenia; Pelletier, Christine C.; Kirby, James P.; Grunthaner, Frank J.

    2007-01-01

    Amino acids are considered organic molecular indicators in the search for extant and extinct life in the Solar System. Extraction of these molecules from a particulate solid matrix, such as Martian regolith, will be critical to their in situ detection and analysis. The goals of this study were to optimize a laboratory amino acid extraction protocol by quantitatively measuring the yields of extracted amino acids as a function of liquid water temperature and sample extraction time and to compare the results to the standard HCl vapor- phase hydrolysis yields for the same soil samples. Soil samples from the Yungay region of the Atacama Desert ( Martian regolith analog) were collected during a field study in the summer of 2005. The amino acids ( alanine, aspartic acid, glutamic acid, glycine, serine, and valine) chosen for analysis were present in the samples at concentrations of 1 - 70 parts- per- billion. Subcritical water extraction efficiency was examined over the temperature range of 30 - 325 degrees C, at pressures of 17.2 or 20.0 MPa, and for water- sample contact equilibration times of 0 - 30 min. None of the amino acids were extracted in detectable amounts at 30 degrees C ( at 17.2 MPa), suggesting that amino acids are too strongly bound by the soil matrix to be extracted at such a low temperature. Between 150 degrees C and 250 degrees C ( at 17.2 MPa), the extraction efficiencies of glycine, alanine, and valine were observed to increase with increasing water temperature, consistent with higher solubility at higher temperatures, perhaps due to the decreasing dielectric constant of water. Amino acids were not detected in extracts collected at 325 degrees C ( at 20.0 MPa), probably due to amino acid decomposition at this temperature. The optimal subcritical water extraction conditions for these amino acids from Atacama Desert soils were achieved at 200 degrees C, 17.2 MPa, and a water- sample contact equilibration time of 10 min.

  20. Water Infiltration and Permeability of Selected Urban Soils as Affected by Salinity and Sodicity 

    E-print Network

    Miyamoto, S.

    2012-10-05

    into two alluvial soils (Torrifluvents), and two upland soils (Paleorthid and Calciorthid, Aridisols) placed in greenhouse pots. For the first experiment, irrigation solutions simulating the Rio Grande water, city potable water, and two sources of reclaimed...

  1. 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.

  2. 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 down from saturation to complete water stress were performed and is analyzed as far how ABL respond to soil moisture changes. This provides informations about ABL behavior on the transition states. Future studies will look on how this behavior will change with the new vegetation covers.

  3. Factors controlling soil water and stream water aluminum concentrations after a clearcut in a forested watershed with calcium-poor soils

    USGS Publications Warehouse

    McHale, M.R.; Burns, D.A.; Lawrence, G.B.; Murdoch, P.S.

    2007-01-01

    The 24 ha Dry Creek watershed in the Catskill Mountains of southeastern New York State USA was clearcut during the winter of 1996-1997. The interactions among acidity, nitrate (NO3- ), aluminum (Al), and calcium (Ca2+) in streamwater, soil water, and groundwater were evaluated to determine how they affected the speciation, solubility, and concentrations of Al after the harvest. Watershed soils were characterized by low base saturation, high exchangeable Al concentrations, and low exchangeable base cation concentrations prior to the harvest. Mean streamwater NO3- concentration was about 20 ??mol l-1 for the 3 years before the harvest, increased sharply after the harvest, and peaked at 1,309 ??mol l -1 about 5 months after the harvest. Nitrate and inorganic monomeric aluminum (Alim) export increased by 4-fold during the first year after the harvest. Alim mobilization is of concern because it is toxic to some fish species and can inhibit the uptake of Ca2+ by tree roots. Organic complexation appeared to control Al solubility in the O horizon while ion exchange and possibly equilibrium with imogolite appeared to control Al solubility in the B horizon. Alim and NO3- concentrations were strongly correlated in B-horizon soil water after the clearcut (r2 = 0.96), especially at NO3- concentrations greater than 100 ??mol l-1. Groundwater entering the stream from perennial springs contained high concentrations of base cations and low concentrations of NO3- which mixed with acidic, high Alim soil water and decreased the concentration of Alim in streamwater after the harvest. Five years after the harvest soil water NO 3- concentrations had dropped below preharvest levels as the demand for nitrogen by regenerating vegetation increased, but groundwater NO3- concentrations remained elevated because groundwater has a longer residence time. As a result streamwater NO3- concentrations had not fallen below preharvest levels, even during the growing season, 5 years after the harvest because of the contribution of groundwater to the stream. Streamwater NO3- and Alim concentrations increased more than reported in previous forest harvesting studies and the recovery was slower likely because the watershed has experienced several decades of acid deposition that has depleted initially base-poor soils of exchangeable base cations and caused long-term acidification of the soil. ?? 2007 Springer Science+Business Media B.V.

  4. Effects of a layer of vegetative ash layer on wettable and water repellent soil hydrology

    NASA Astrophysics Data System (ADS)

    Bodí, Merche B.; Doerr, Stefan H.; Cerdà, Artemi; Mataix-Solera, Jorge

    2010-05-01

    Following a wildfire, a layer of vegetative ash often covers the ground until it is dissolved or redistributed by wind and water erosion. Much of the existing literature suggests that the ash layer temporally reduces infiltration by clogging soil pores or by forming a surface crust (Mallik et al., 1984; Onda et al., 2008). However, an increasing number of field-based studies have found that, at least in the short term, ash increases infiltration by storing rainfall and protecting the underlying soil from sealing (Cerdà and Doerr, 2008; Woods and Balfour, 2008). On the other hand, after a fire the soil may have produced, enhanced or reduced its water repellency (Doerr et al., 2000). Very few studies have been taken into account the interaction of the ash and the repellent soil. The layer of ash may have similar role as a litter layer in delaying runoff and reducing erosion by storing water. In order to examine this interaction, it was been made a series of experiments using a laboratory rainfall simulation. It has been assessed the effects of an ash layer i) on a wettable and water repellent soil (WDPT > 7200s), ii) with different ash thicknesses (bare soil and 5 mm, 15 mm and 30 mm of ash), iii) preceding and following the first rain after a fire when the ground is still wetted and after being partially dried. Three replicates were done, being a total of 40 simulations. The ash used was collected from a Wildfire in Teruel (Spain) during summer of 2009. The simulations were conducted in metal boxes of 30x30 cm and filled with 3 cm of soil. The slope of the box was set at 10° (17%) and the intensity applied was 78-84 mm h-1during 40 minutes. The splash detachment was determined also using four splash cups. Overland flow and subsurface drainage was collected at 1-minute intervals and the former stored every 5 min to allow determination of sediment concentrations, yield and erosion rates. Each sample was examined at the end in terms of water repellency, infiltration pattern and ash incorporation into the soil. The results show that when ash covers the wettable soil, runoff occur for a short period of time in the middle of the event. It occurred latter on time but larger in quantity as the ash thickness increases (from 0% to 2% of runoff coefficient) and at the same time drainage is reduced (from 57 to 24%). This suggests that the ash layer became saturated and produce runoff until the water is able to drain into the soil. Oppositely, in water repellent soil as ash thickness increases both runoff is reduced (from 78% to 26%) and drainage is increased (from 0 to 16%). That fact indicates a modification in the hydraulic conductivity of the repellent soil due to the pressure of the ash layer. Splash and erosion rates are bigger in water repellent soils yet erosion rates never exceed 2.5 g m-2 h-1. The fact of wetting increases the runoff and drainage rates in wettable but reduce them in the water repellent soil. An irregular infiltration pattern is observed afterwards. After drying the soil, the increase in runoff indicates a crust formation. Moreover, in water repellent soils part of the repellency is reestablished. These findings demonstrate that the interaction of the soil-ash layer should be considered and better studied in the immediate hydrological response after wildfire due to its particular behavior. References Cerdà, A. and Doerr, S.H., 2008. The effect of ash and needle cover on surface runoff and erosion in the immediate post-fire period. Catena, 74: 256-263. Doerr, S.H., Shakesby, R.A. and Walsh, R.P.D., 2000. Soil Water repellency: Its causes, characteristics and hydro-geomorphological significance. Earth Science Reviews, 51: 33-65. Mallik, A.U., Gimingham, C.H. and Rahman, A.A., 1984. Ecological effects of heater burning. I. Water infiltration, moisture retention and porosity of surface soil. Journal of Ecology, 72: 767-776. Onda, Y., Dietrich, W.E. and Booker, F., 2008. Evolution of overland flow after a severe forest fire, Point Reyes, California. Catena, 72: 13-20. Woods, S.W. and Balfour, V., 2008. The

  5. Soil water repellency and infiltration in coarse-textured soils of burned and unburned sagebrush ecosystems

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Millions of dollars are spent each year in the United States to mitigate the effects of wildfires and reduce the risk of flash floods and debris flows. Research from forested, chaparral, and rangeland communities indicate severe wildfires can cause significant increases in soil water repellency res...

  6. ASSIMILATION OF SURFACE SOIL MOISTURE TO ESTIMATE PROFILE SOIL WATER CONTENT: A FIELD AND MODELING EXPERIMENT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Data assimilation is a relatively new area of research as related to the integration of remote sensing data and soil water modeling. Most of the related studies reported in the literature have largely been theoretical in nature since field data needed to verify the modeling results were often not a...

  7. Role of soil adsorption and microbial degradation on dissipation of mesotrione in plant available soil water

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mesotrione is a carotenoid biosynthesis-inhibiting herbicide labeled for pre-emergence and post emergent weed control in corn production. Understanding the factors that influence the dissipation of mesotrione in soil and in the plant available water (PAW) is important for both the environmental fat...

  8. Tillage depth and timing effects on soil water profiles in two semiarid soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The two-year winter wheat--fallow rotation continues to be the most profitable and productive cropping system in much of the Pacific Northwest, USA. Sustainability of soils in the region depends on our ability to halt or greatly reduce wind and water erosion. An incomplete understanding of how tille...

  9. In-Soil and Down-Hole Soil Water Sensors: Characteristics for Irrigation Management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    The past use of soil water sensors for irrigation management was variously hampered by high cost, onerous regulations in the case of the neutron probe (NP), difficulty of installation or maintenance, and poor accuracy. Although many sensors are now available, questions of their utility still abound....

  10. Mapping soil water retention curves via spatial Bayesian hierarchical models

    NASA Astrophysics Data System (ADS)

    Yang, Wen-Hsi; Clifford, David; Minasny, Budiman

    2015-05-01

    Soil water retention curves are an important parameter in soil hydrological modeling. These curves are usually represented by the van Genuchten model. Two approaches have previously been taken to predict curves across a field - interpolation of field measurements followed by estimation of the van Genuchten model parameters, or estimation of the parameters according to field measurements followed by interpolation of the estimated parameters. Neither approach is ideal as, due to their two-stage nature, they fail to properly track uncertainty from one stage to the next. In this paper we address this shortcoming through a spatial Bayesian hierarchical model that fits the van Genuchten model and predicts the fields of hydraulic parameters of the van Genuchten model as well as fields of the corresponding soil water retention curves. This approach expands the van Genuchten model to a hierarchical modeling framework. In this framework, soil properties and physical or environmental factors can be treated as covariates to add into the van Genuchten model hierarchically. Consequently, the effects of covariates on the hydraulic parameters of the van Genuchten model can be identified. In addition, our approach takes advantage of Bayesian analysis to account for uncertainty and overcome the shortcomings of other existing methods. The code used to fit these models are available as an appendix to this paper. We apply this approach to data surveyed from part of the alluvial plain of the river Rhône near Yenne in Savoie, France. In this data analysis, we demonstrate how the inclusion of soil type or spatial effects can improve the van Genuchten model's predictions of soil water retention curves.

  11. 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 real priming effects that mobilised N from organic matter. The results from this experiment indicate that rhizosphere processes play an important role in mediating rates of C and N mineralisation and should be accounted for in estimating soil N-supply capacities. Velthof, G.L., Oudendag, D., Witzke, H.P., Asman, W.A.H., Klimont, Z., Oenema, O., 2009. Integrated assessment of nitrogen losses from agriculture in EU-27 using MITERRA-EUROPE. Journal of Environmental Quality 38, 402-417.

  12. Wildfire impacts on soil-water retention in the Colorado Front Range, United States

    NASA Astrophysics Data System (ADS)

    Ebel, Brian A.

    2012-12-01

    This work examined the plot-scale differences in soil-water retention caused by wildfire in the area of the 2010 Fourmile Canyon Fire in the Colorado Front Range, United States. We measured soil-water retention curves on intact cores and repacked samples, soil particle-size distributions, and organic matter content. Estimates were also made of plant-available water based on the soil-water retention curves. Parameters for use in soil-hydraulic property models were estimated; these parameters can be used in unsaturated flow modeling for comparing burned and unburned watersheds. The primary driver for measured differences in soil-water retention in burned and unburned soils was organic matter content and not soil-particle size distribution. The tendency for unburned south-facing soils to have greater organic matter content than unburned north-facing soils in this field area may explain why unburned south-facing soils had greater soil-water retention than unburned north-facing soils. Our results suggest that high-severity wildfire can "homogenize" soil-water retention across the landscape by erasing soil-water retention differences resulting from organic matter content, which for this site may be affected by slope aspect. This homogenization could have important implications for ecohydrology and plant succession/recovery in burned areas, which could be a factor in dictating the window of vulnerability of the landscape to flash floods and erosion that are a common consequence of wildfire.

  13. 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. A ratio of MSS channels 5 and 7 (5/7) and 5 to 6 (5/6) signals resulted in a correct recognition of 86.9% of the members of representative crop and soil conditions, compared with recognitions of 60.0, 64.1, 74.1, and 81.4% for channels 4, 5, 6, and 7 taken individually. Based on this result a satellite channel ratio procedure has been developed that enhances line printer gray maps for more efficient experimental test site location in the CCT data. Because independent estimates are not available to judge acreage estmates derived from ERTS-1 data against, except for a few crops, an interpenetrating sample constituting 3.5% of the county is ground truthed periodically. The crop of land uses and their acreages, respectively, as estimated from the interpenetrating samples, are: cotton, 129, 714; sorghum, 182,783; mixed citrus, 53,954; oranges, 16,929; grapefruit, 13,863; rangeland, 137,845; and, improved pastures, 57.169.

  14. Reflectance of vegetation, soil, and water

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L.; Gausman, H. W.; Leamer, R. W.; Richardson, A. J.; Gerbermann, A. H. (principal investigators)

    1974-01-01

    The author has identified the following significant results. Iron deficient and normal grain sorghum plants were sufficiently different spectrally in ERTS-1 band 5 CCT data to detect chlorotic sorghum areas 2.8 acres (1.1 hectares) or larger in size in computer printouts of the MSS data. The ratio of band 5 to band 7 or band 7 minus band 5 relates to vegetation ground cover conditions and helps to select training samples representative of differing vegetation maturity or vigor classes and to estimate ground cover or green vegetation density in the absence of ground information. The four plant parameters; leaf area index, plant population, plant cover, and plant height explained 87 to 93% of the variability in band 6 digital counts and from 59 to 90% of the variation in bands 4 and 5. A ground area 2244 acres in size was classified on a pixel by pixel basis using simultaneously acquired aircraft support and ERTS-1 data. Overall recognition for vegetables, immature crops and mixed shrubs, and bare soil categories was 64.5% for aircraft and 59.6% for spacecraft data, respectively. Overall recognition results on a per field basis were 61.8% for aircraft and 62.8% for ERTS-1 data.

  15. Reflectance of vegetation, soil, and water

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L. (principal investigator)

    1974-01-01

    The author has identified the following significant results. The Kubelka-Munk model, a regression model, and a combination of these models were used to extract plant, soil, and shadow reflectance components of vegetated surfaces. The combination model was superior to the others; it explained 86% of the variation in band 5 reflectance of corn and sorghum, and 90% of the variation in band 6 reflectance of cotton. A fractional shadow term substantially increased the proportion of the digital count sum of squares explained when plant parameters alone explained 85% or less of the variation. Overall recognition of 94 agricultural fields using simultaneously acquired aircraft and spacecraft MSS data was 61.8 and 62.8%, respectively; recognition of vegetable fields larger than 10 acres and taller than 25 cm, rose to 88.9 and 100% for aircraft and spacecraft, respectively. Agriculture and rangeland, were well discriminated for the entire county but level 2 categories of vegetables, citrus, and idle cropland, except for citrus, were not.

  16. Hugoniot Measurements on Dry and Water-Saturated Soils

    NASA Astrophysics Data System (ADS)

    Newman, Matthew; Stewart, Sarah; Kraus, Richard

    2015-06-01

    To better understand the shock properties of granular materials, we present a series of shock Hugoniot experiments on three types of soil in both dry and water-saturated states. We measured the shock states induced via planar impact experiments on the Harvard 40-mm gas gun. Shock wave velocities in the soils were measured using both VISAR and piezo-pins. The soils were composed primarily of quartz with different mass fractions of phyllosilicates and amorphous material. Using initial particle sizes ranging from 150 to 300 microns, the samples were pressed to densities ranging from 1.89 to 1.93 g cm-3 (about 25% porous). Water-sat samples had densities ranging from 2.2 to 2.6 g cm-3. We find that the dry soils have a linear Us -up relation that is similar to dry quartz sand with the same initial density. The water-sat samples are less compressible and have much greater scatter in shock velocities. The VISAR measurement records the dispersion around the mean shock state that arises from reflections between grains, and we compare the VISAR data to meso-scale hydrocode simulations. These data will be used to generate more accurate rheological models for hydrocode simulations of the shock response of heterogeneous granular materials in the low-pressure regime (< 10 GPa). We acknowledge support from Army Research Office Grant #W911NF-10-1-037.

  17. 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 the contact angles were similar for intact cells and cell envelope fragments, whereas they were even more pronounced if the minerals interacted with the cytosol. Based on these results we conclude that bacterial cells and their residues play an important role in controlling soil particle surface properties, in particular wettability. This process can explain the development of water repellency in soils, which has a major impact on the distribution and availability of water in soils at the microscale.

  18. 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 interventions to ensure the long-term sustainability of the restored ecosystems.

  19. Soil and Water Science Department University of Florida Background concentrations of trace metals in Florida surface soils

    E-print Network

    Ma, Lena

    Soil and Water Science Department University of Florida Background concentrations of trace metals in Florida surface soils Ma, L. Q., W. Harris, and A. Hornsby 3/1996-2/1999 Objectives: · Determine elemental Florida surface soil samples; · Analyze elemental concentrations statistically to understand

  20. Soil and Water Science Department University of Florida Developing retention indices and modeling transport of CCA in Florida soils at

    E-print Network

    Ma, Lena

    Soil and Water Science Department University of Florida Developing retention indices and modeling transport of CCA in Florida soils at unlined landfills Clark, C.J., T. Chirenje, L. Q. Ma, J. W. Jawitz, M are connected by and related to CCA mobility in Florida soils especially at unlined landfill disposal sites

  1. Relation of soil-, surface-, and ground-water distributions of inorganic nitrogen with

    E-print Network

    Macdonald, Ellen

    Relation of soil-, surface-, and ground-water distributions of inorganic nitrogen with topographic nitrate (NO3 - ) and ammonium (NH4 + ) concentrations were related to surface- and ground-water NO3 was not apparent for surface soils. Soil NO3 - and NH4 + availability and surface- and ground-water NO3 - and NH4

  2. Soil Water Sensor Needs for the Evaluation of Hydraulic Lift in Crop Plants

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Hydraulic lift (HL) in plants is defined as the process by which water is redistributed from wet soil zones to drier soil zones through the plant root system in response to gradients in water potential. Water is released into the dry soil when plant transpiration is low (night) and reabsorbed by th...

  3. ESTIMATION OF SOIL WATER CONTENT AND EVAPOTRANSPIRATION OF DRYLAND CROPS USING NEUTRON MOISTURE METER

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In semi-arid regions, crop yield is often more correlated with soil water availability than any other soil or meteorological factor. Thus, quantification of soil water depletion by crops is important in estimating seasonal water use and evaluating alternative dryland cropping strategies, crop specie...

  4. COMPARISON OF PLOT SCALE AVERAGE GRAVIMETRIC SOIL WATER CONTENTS WITH DATA FROM CALIBRATED MULTISENSOR CAPACITANCE PROBES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Multisensor capacitance probes (MCPs) provide unparalleled spatial and temporal resolution to soil water content measurements. They are utilized in many applications where soil water availability needs monitoring. The objective of this work was to assess errors in plot scale soil volumetric water co...

  5. 26 CFR 1.175-1 - Soil and water conservation expenditures; in general.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 2012-04-01 false Soil and water conservation expenditures; in...Corporations (continued) § 1.175-1 Soil and water conservation expenditures; in...Under section 175, a farmer may deduct his soil or water conservation...

  6. 26 CFR 1.175-1 - Soil and water conservation expenditures; in general.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 2013-04-01 false Soil and water conservation expenditures; in...Corporations (continued) § 1.175-1 Soil and water conservation expenditures; in...Under section 175, a farmer may deduct his soil or water conservation...

  7. 26 CFR 1.175-1 - Soil and water conservation expenditures; in general.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 2014-04-01 false Soil and water conservation expenditures; in...Corporations (continued) § 1.175-1 Soil and water conservation expenditures; in...Under section 175, a farmer may deduct his soil or water conservation...

  8. COSMOS soil water sensor compared with EM sensor network & weighing lysimeter

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water sensing methods are widely used to characterize the root zone and below, but only a few are capable of delivering water content data with accuracy for the entire soil profile such that evapotranspiration (ET) can be determined by soil water balance and irrigations can be scheduled with mi...

  9. Water flux and drainage from soil measured with automated passive capillary wick samplers

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Various soil water samplers are used to monitor measure and estimate drainage water, fluxes and solute transport in the soil vadose zone. Passive capillary samplers (PCAPs) have shown potential to provide better measurements and estimates of soil water drainage and fluxes than other lysimeters.Twelv...

  10. Soil water sensing: Implications of sensor capabilities for variable rate irrigation management

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Irrigation scheduling using soil water sensors aims at maintaining the soil water content in the crop root zone above a lower limit defined by the management allowed depletion (MAD) for that soil and crop, but not so wet that too much water is lost to deep percolation, evaporation and runoff or that...

  11. 26 CFR 1.175-1 - Soil and water conservation expenditures; in general.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 2011-04-01 false Soil and water conservation expenditures; in...Corporations (continued) § 1.175-1 Soil and water conservation expenditures; in...Under section 175, a farmer may deduct his soil or water conservation...

  12. Soil water content dependent wetting front characteristics in sands T.W.J. Bautersa

    E-print Network

    that the finger- like pattern in water repellent soil had many similarities with unstable wetting fronts in airSoil water content dependent wetting front characteristics in sands T.W.J. Bautersa , D.A. Di 94305, USA Received 2 April 1999; accepted 13 August 1999 Abstract The initial soil water content

  13. 26 CFR 1.175-1 - Soil and water conservation expenditures; in general.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 26 Internal Revenue 3 2012-04-01 2012-04-01 false Soil and water conservation expenditures; in... Corporations (continued) § 1.175-1 Soil and water conservation expenditures; in general. Under section 175, a farmer may deduct his soil or water conservation expenditures which do not give rise to a deduction...

  14. 26 CFR 1.175-1 - Soil and water conservation expenditures; in general.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 26 Internal Revenue 3 2010-04-01 2010-04-01 false Soil and water conservation expenditures; in... (continued) § 1.175-1 Soil and water conservation expenditures; in general. Under section 175, a farmer may deduct his soil or water conservation expenditures which do not give rise to a deduction for...

  15. 26 CFR 1.175-1 - Soil and water conservation expenditures; in general.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 26 Internal Revenue 3 2011-04-01 2011-04-01 false Soil and water conservation expenditures; in... Corporations (continued) § 1.175-1 Soil and water conservation expenditures; in general. Under section 175, a farmer may deduct his soil or water conservation expenditures which do not give rise to a deduction...

  16. 26 CFR 1.175-1 - Soil and water conservation expenditures; in general.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 26 Internal Revenue 3 2014-04-01 2014-04-01 false Soil and water conservation expenditures; in... Corporations (continued) § 1.175-1 Soil and water conservation expenditures; in general. Under section 175, a farmer may deduct his soil or water conservation expenditures which do not give rise to a deduction...

  17. HYDRAULIC REDISTRIBUTION OF SOIL WATER DURING SUMMER DROUGHT IN TWO CONTRASTING PACIFIC NORTHWEST CONIFEROUS FORESTS

    EPA Science Inventory

    The magnitude of hydraulic redistribution of soil water by roots and its impact on soil water balance were estimated by monitoring time courses of soil water status at multiple depths and root sap flow during droughted conditions in a dry ponderosa pine ecosystem and a moist Doug...

  18. ESTIMATION OF SOIL WATER CONTENT AND EVAPOTRANSPIRATION OF DRYLAND CROPS USING THE NEUTRON MOISTURE METER

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In semi-arid regions, soil water availability is often more correlated with crop yields than any other soil or meteorological factor. Thus, quantification of soil water depletion by crops is important in estimating seasonal water use and evaluating alternative dryland cropping strategies, crop speci...

  19. 26 CFR 1.175-1 - Soil and water conservation expenditures; in general.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 2010-04-01 false Soil and water conservation expenditures; in...Corporations (continued) § 1.175-1 Soil and water conservation expenditures; in...Under section 175, a farmer may deduct his soil or water conservation...

  20. Identification and correction of spectral contamination in 2 O measured in leaf, stem, and soil water

    E-print Network

    Minnesota, University of

    - ancies between the isotope ratios of plant and soil water measured with IRIS and IRMS.[10, stem, and soil water Natalie M. Schultz1 *, Timothy J. Griffis1 , Xuhui Lee2 and John M. Baker1,3 1 Department of Soil, Water, and Climate, University of Minnesota, St. Paul, MN, USA 2 School of Forestry

  1. CONVERGING PATTERNS OF UPTAKE AND HYDRAULIC REDISTRIBUTION OF SOIL WATER IN CONTRASTING WOODY VEGETATION TYPES

    EPA Science Inventory

    We used concurrent measurements of soil water content and soil water potential (Ysoil) to assess the effects of Ysoil on uptake and hydraulic redistribution (HR) of soil water by roots during seasonal drought cycles in six sites characterized by different types and amounts of woo...

  2. Field estimation of soil water content: A practical guide to methods, instrumentation and sensor technology

    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, resulting in this guide to field estimation of soil water content. The book gives an overview of soil water co...

  3. Monitoring Changes in Soil Water Content Using Subsurface Displacement

    NASA Astrophysics Data System (ADS)

    Thrash, C. J.; Miller, S.; Murdoch, L. C.; Germanovich, L. N.; Gates, J. B.; Volkmer, A.; Weinburg, A.

    2013-12-01

    Closing the water balance is important in many research and water resource applications, but it can be difficult to accomplish due to a variety of factors. A new technique that measures vertical displacement of soil in order to estimate the change in mass of water stored in overlying material is being developed. The measurement technique uses an extensometer that functions as a lysimeter, and we refer to the technique as Displacement Extensometry for Lysimetric Terrain Analysis (DELTA). DELTA extensometers are 2-m-long devices deployed by creating a friction fit with intact soil below a cased borehole. The instrument measures small displacements (better than 10 nm resolution) in response to changes of mass in the overlying soil, or other factors. The instrument averages over a region that scales with the depth of installation (the radius of influence is approximately 2x the depth). The spatial averaging of this instrument extends over regions representative of agricultural fields, hydrologic model grid blocks, and small watersheds. Five DELTA extensometers have been deployed at a field site near Clemson, SC at depths of 3, 6, and 9 m within saprolite derived from biotite gneiss. Barometric pressure, precipitation, and soil moisture are being measured along with displacement. Signals from the co-located extensometers are remarkably similar, demonstrating reproducibility of the technique. Rainfall causes soil compression, and at 6 m depth there is approximately 200 nm of compression per 1 mm of rainfall. There is gradual expansion, which ranges from 0.15 to 1.75 ?m/day, following rainfall. The gradual unloading of the soil is interpreted as water loss due to evapotranspiration. Superimposed on the signal are diurnal fluctuations of 0.5 to 1 ?m, which correlate to changes in barometric pressure. Four DELTA extensometers were recently deployed in hard, clayey sediments at two field locations south of Amarillo, TX. The instruments will compliment current research on groundwater recharge in playas. Two other extensometers were deployed in loess at a field site near Holdredge, NE, where they will be used to help characterize water cycling beneath irrigated agriculture. Calibration data has been obtained and the instruments appear to be functioning properly. The preliminary data suggest that the DELTA technique should be applicable in a variety of soil types.

  4. The water-soluble argentivorous molecule: Ag(+)-? interactions in water.

    PubMed

    Habata, Yoichi; Okeda, Yoko; Ikeda, Mari; Kuwahara, Shunsuke

    2013-07-01

    Ag(+)-? interactions between Ag(+) ions and a water-soluble tetra-armed cyclen bearing aromatic side-arms (tetracesium 4,4',4'',4'''-((1,4,7,10-tetraazacyclododecane-1,4,7,10-tetrayl)tetrakis(methylene))tetrabenzoate, Cs4) are reported. The structure of the Ag(+) complex with Cs4 was examined using cold ESI-MS, and (1)H NMR and UV spectroscopies. It is found that when it forms Ag(+) complexes in water, Cs4 behaves like an insectivorous plant (Venus flytrap). PMID:23685790

  5. Contact angles of wetting and water stability of soil structure

    NASA Astrophysics Data System (ADS)

    Kholodov, V. A.; Yaroslavtseva, N. V.; Yashin, M. A.; Frid, A. S.; Lazarev, V. I.; Tyugai, Z. N.; Milanovskiy, E. Yu.

    2015-06-01

    From the soddy-podzolic soils and typical chernozems of different texture and land use, dry 3-1 mm aggregates were isolated and sieved in water. As a result, water-stable aggregates and water-unstable particles composing dry 3-1 mm aggregates were obtained. These preparations were ground, and contact angles of wetting were determined by the static sessile drop method. The angles varied from 11° to 85°. In most cases, the values of the angles for the water-stable aggregates significantly exceeded those for the water-unstable components. In terms of carbon content in structural units, there was no correlation between these parameters. When analyzing the soil varieties separately, the significant positive correlation between the carbon content and contact angle of aggregates was revealed only for the loamy-clayey typical chernozem. Based on the multivariate analysis of variance, the value of contact wetting angle was shown to be determined by the structural units belonging to water-stable or water-unstable components of macroaggregates and by the land use type. In addition, along with these parameters, the texture has an indirect effect.

  6. Horizontal soil water potential heterogeneity: simplifying approaches for crop water dynamics models

    NASA Astrophysics Data System (ADS)

    Couvreur, V.; Vanderborght, J.; Beff, L.; Javaux, M.

    2014-05-01

    Soil water potential (SWP) is known to affect plant water status, and even though observations demonstrate that SWP distribution around roots may limit plant water availability, its horizontal heterogeneity within the root zone is often neglected in hydrological models. As motive, using a horizontal discretisation significantly larger than one centimetre is often essential for computing time considerations, especially for large-scale hydrodynamics models. In this paper, we simulate soil and root system hydrodynamics at the centimetre scale and evaluate approaches to upscale variables and parameters related to root water uptake (RWU) for two crop systems: a densely seeded crop with an average uniform distribution of roots in the horizontal direction (winter wheat) and a wide-row crop with lateral variations in root density (maize). In a first approach, the upscaled water potential at soil-root interfaces was assumed to equal the bulk SWP of the upscaled soil element. Using this assumption, the 3-D high-resolution model could be accurately upscaled to a 2-D model for maize and a 1-D model for wheat. The accuracy of the upscaled models generally increased with soil hydraulic conductivity, lateral homogeneity of root distribution, and low transpiration rate. The link between horizontal upscaling and an implicit assumption on soil water redistribution was demonstrated in quantitative terms, and explained upscaling accuracy. In a second approach, the soil-root interface water potential was estimated by using a constant rate analytical solution of the axisymmetric soil water flow towards individual roots. In addition to the theoretical model properties, effective properties were tested in order to account for unfulfilled assumptions of the analytical solution: non-uniform lateral root distributions and transient RWU rates. Significant improvements were however only noticed for winter wheat, for which the first approach was already satisfying. This study confirms that the use of 1-D spatial discretisation to represent soil-plant water dynamics is a worthy choice for densely seeded crops. For wide-row crops, e.g. maize, further theoretical developments that better account for horizontal SWP heterogeneity might be needed in order to properly predict soil-plant hydrodynamics in 1-D.

  7. Influence of soil surface characteristics and water repellence on soil infiltration and soil loss of Andisols (Canary Islands, Spain)

    NASA Astrophysics Data System (ADS)

    Concepción, Jiménez; Jonay, Neris; Josué, Fuentes; Marisa, Tejedor

    2010-05-01

    Infiltration is a crucial process in the hydrological cycle, since it controls - among other things - the generation of run-off, erosion and aquifer recharge. Undisturbed Andisols are considered resistant to water erosion; a characteristic closely associated with their high porosity that permits a rapid rainfall infiltration and high structural stability. In spite of that, the high content of organic C on this type of soils, and the positive relation between this property and water repellence, could allow the presence of some soil surface characteristics that may change this behaviour. The aim of this work was to study the influence of these hydrophobic layers on water infiltration and soil loss on Andisols of Tenerife. Twelve sites were chosen, all of which are located on the northern side of the island of Tenerife (Canary Islands, Spain), between 825-1400 m.a.s.l. The soils are allophanic Andisols (Typic/Lithic Hapludands and Typic Haplustands) and vitric Andisols (Typic Udivitrands) under pine forest. In each site, soil surface features with potential hydrological implications were described. To determine infiltration, a rainfall simulator with the following characteristics was used: 35 x 25 x 30 cm metal box with nozzles in the bottom, 2.5 cm apart (diameter of drops = 2-3 mm). The 4 box adjustable legs were set at 2 m height. Prior to installing the rainfall simulator, study zones were marked out using 30 cm-tall metal sheets. Each area measured approximately 875 cm2 and measurements were taken for slopes of 10 and 30% when it was possible. At the end of the slope a 25 cm-wide collector was semi-buried to collect runoff and sediment. Rainfall of variable intensity between 50-70 mmh-1 was simulated for periods of 30-45 minutes. Time to runoff (TR), volume to runoff (VR), steady-state infiltration rate (IR), runoff/rainfall ratio (RR), soil loss rate (SED) and sediment concentration (CSED) were measured. For some of the studied soils, the formation of horizons made up with pine needles embedded with fungi mycelia was observed. These layers were highly water-repellent and could be easily detached from the underlying soil. When comparing the soils in which these are present with those devoid of them, the former showed an average decrease of 40% in TR and VR for both slopes. The IR suffered a decrease of nearly 40% and 30%, and the RR an increase of 40% and 20% for slopes of 10 and 30% respectively. Contradictory, soil loss showed a decrease in sites where this layer was present, 20% and 40% in SED, and 15% and 50% in CSED for slopes of 10% and 30% respectively. As a conclusion, despite the reduction in IR and the increase in RR, the presence of this layer in soils seems to provide them with a high resistance to drop impact, and a modification of water dynamics leading to a decrease of soil loss.

  8. WATER RESOURCES RESEARCH, VOL. ???, XXXX, DOI:10.1029/, The soil water characteristic as new class of1

    E-print Network

    Vrugt, Jasper A.

    curve.15 These soil water retention functions are relatively simple to use, contain be-16 tween twoWATER RESOURCES RESEARCH, VOL. ???, XXXX, DOI:10.1029/, The soil water characteristic as new class, University of California, Irvine, CA, USA. 3 Department of Hydrology and Water Resources, University

  9. Interactions Between Wind Erosion, Vegetation Structure, and Soil Stability in Groundwater Dependent Plant Communities

    NASA Astrophysics Data System (ADS)

    Vest, K. R.; Elmore, A. J.; Okin, G. S.

    2009-12-01

    Desertification is a human induced global phenomenon causing a loss of biodiversity and ecosystem productivity. Semi-arid grasslands are vulnerable to anthropogenic impacts (i.e., groundwater pumping and surface water diversion) that decrease vegetation cover and increase bare soil area leading to a greater probability of soil erosion, potentially enhancing feedback processes associated with desertification. To enhance our understanding of interactions between anthropogenic, physical, and biological factors causing desertification, this study used a combination of modeling and field observations to examine the relationship between chronic groundwater pumping and vegetation cover change and its effects on soil erosion and stability. The work was conducted in Owens Valley California, where a long history of groundwater pumping and surface water diversion has lead to documented vegetation changes. The work examined hydrological, ecological and biogeochemical factors across thirteen sites in Owens Valley. We analyzed soil stability, vegetation and gap size, soil organic carbon, and we also installed Big Spring Number Eight (BSNE) catchers to calculate mass transport of aeolian sediment across sites. Mass transport calculations were used to validate a new wind erosion model that represents the effect of porous vegetation on surface windshear velocity. Results across two field seasons show that the model can be used to predict mass transport, and areas with increased groundwater pumping show a greater susceptibility to erosion. Sediment collected in BSNE catchers was positively correlated with site gap size. Additionally, areas with larger gap sizes have a greater threshold shear velocity and soil stability, yet mass transport was greater at these sites than at sites with smaller gap sizes. Although modeling is complicated by spatial variation in multiple model parameters (e.g., gap size, threshold shear velocity in gaps), our results support the hypothesis that soils with high organic matter are being eroded following the loss of vegetation cover due to groundwater decline leaving behind bare soil surfaces with less fertility hampering vegetation reestablishment. Desertification in this system is apparently easily initiated through groundwater decline due to the high friability of these meadow soils.

  10. Spatial regression between soil surface elevation, water storage in root zone and biomass productivity of alfalfa within an irrigated field

    NASA Astrophysics Data System (ADS)

    Zeyliger, Anatoly; Ermolaeva, Olga

    2014-05-01

    Efficiency of water use for the irrigation purposes is connected to the variety of circumstances, factors and processes appearing along the transportation path of water from its sources to the root zone of the plant. Water efficiency of agricultural irrigation is connected with variety of circumstances, the impacts and the processes occurring during the transportation of water from water sources to plant root zone. Agrohydrological processes occur directly at the irrigated field, these processes linked to the infiltration of the applied water subsequent redistribution of the infiltrated water within the root zone. One of them are agrohydrological processes occurring directly on an irrigated field, connected with infiltration of water applied for irrigation to the soil, and the subsequent redistribution of infiltrated water in the root zone. These processes have the strongly pronounced spatial character depending on the one hand from a spatial variation of some hydrological characteristics of soils, and from other hand with distribution of volume of irrigation water on a surface of the area of an irrigated field closely linked with irrigation technology used. The combination of water application parameters with agrohydrological characteristics of soils and agricultural vegetation in each point at the surface of an irrigated field leads to formation of a vector field of intensity of irrigation water. In an ideal situation, such velocity field on a soil surface should represent uniform set of vertically directed collinear vectors. Thus values of these vectors should be equal to infiltration intensities of water inflows on a soil surface. In soil profile the field of formed intensities of a water flow should lead to formation in it of a water storage accessible to root system of irrigated crops. In practice this ideal scheme undergoes a lot of changes. These changes have the different nature, the reasons of occurrence and degree of influence on the processes connected with formation of water flow and water storage. The major changes are formed as a result of imposing of the intensity fields on a soil surface and its field capillary infiltration rate. Excess of the first intensity over the second in each point of soil surface leads to formation of a layer of intensity of water not infiltrated in soil. Thus generate the new field of vectors of intensity which can consist of vertically directed vector of speed of evaporation, a quasi horizontal vector of intensity of a surface water flow and quasi vertical vector of intensity of a preferential flow directed downwards. Principal cause of excess of irrigation water application intensity over capillary infiltration rate can be on the one hand spatial non-uniformity of irrigation water application, and with other spatial variability of capillary infiltration rate, connected with spatial variability of water storage in the top layers of soil. As a result the spatial redistribution of irrigation water over irrigated filed forms distortions of ideal model of irrigation water storage in root zone of soil profile. The major differences consist in increasing of water storage in the depressions of a relief of an irrigated field and accordingly in their reduction on elevated zones of a relief, as well as losses of irrigation water outside of boundaries of a root zone of an irrigated field, in vertical, and horizontal directions. One of key parameters characterizing interaction between irrigation technology and soil state an irrigated field are intensity of water application, intensity and volume of a capillary infiltration, the water storage in root zone at the moment of infiltration starting and a topography of an irrigated field. Fnalyzing of spatial links between these characteristics a special research had been carried out on irrigated by sprinkler machine called Fregate at alfalfa field during the summer of 2012. This research carried out at experimental farm of the research institute VolgNIIGiM situated at a left bank of Volga River of Saratov Region of Russia (N51.384650°, E46.0558

  11. Effects of rainfall seasonality and soil moisture capacity on mean annual water balance for Australian catchments

    USGS Publications Warehouse

    Potter, N.J.; Zhang, L.; Milly, P.C.D.; McMahon, T.A.; Jakeman, A.J.

    2005-01-01

    An important factor controlling catchment-scale water balance is the seasonal variation of climate. The aim of this study is to investigate the effect of the seasonal distributions of water and energy, and their interactions with the soil moisture store, on mean annual water balance in Australia at catchment scales using a stochastic model of soil moisture balance with seasonally varying forcing. The rainfall regime at 262 catchments around Australia was modeled as a Poisson process with the mean storm arrival rate and the mean storm depth varying throughout the year as cosine curves with annual periods. The soil moisture dynamics were represented by use of a single, finite water store having infinite infiltration capacity, and the potential evapotranspiration rate was modeled as an annual cosine curve. The mean annual water budget was calculated numerically using a Monte Carlo simulation. The model predicted that for a given level of climatic aridity the ratio of mean annual evapotranspiration to rainfall was larger where the potential evapotranspiration and rainfall were in phase, that is, in summer-dominant rainfall catchments, than where they were out of phase. The observed mean annual evapotranspiration ratios have opposite results. As a result, estimates of mean annual evapotranspiration from the model compared poorly with observational data. Because the inclusion of seasonally varying forcing alone was not sufficient to explain variability in the mean annual water balance, other catchment properties may play a role. Further analysis showed that the water balance was highly sensitive to the catchment-scale soil moisture capacity. Calibrations of this parameter indicated that infiltration-excess runoff might be an important process, especially for the summer-dominant rainfall catchments; most similar studies have shown that modeling of infiltration-excess runoff is not required at the mean annual timescale. Copyright 2005 by the American Geophysical Union.

  12. Soil, water, and vegetation conditions in south Texas

    NASA Technical Reports Server (NTRS)

    Wiegand, C. L.; Gausman, H. W.; Leamer, R. W.; Richardson, A. J.; Everitt, J. H.; Gerbermann, A. H. (principal investigators)

    1976-01-01

    The author has identified the following significant results. Software development for a computer-aided crop and soil survey system is nearing completion. Computer-aided variety classification accuracies using LANDSAT-1 MSS data for a 600 hectare citrus farm were 83% for Redblush grapefruit and 91% for oranges. These accuracies indicate that there is good potential for computer-aided inventories of grapefruit and orange citrus orchards with LANDSAT-type MSS data. Mean digital values of clouds differed statistically from those for crop, soil, and water entities, and those for cloud shadows were enough lower than sunlit crop and soil to be distinguishable. The standard errors of estimate for the calibration of computer compatible tape coordinate system (pixel and record) to earth coordinate system (longitude and latitude) for 6 LANDSAT scenes ranged from 0.72 to 1.50 pixels and from 0.58 to 1.75 records.

  13. Soil water depletion by oak trees and the influence of root water uptake on the moisture content spatial statistics

    E-print Network

    Oren, Ram

    Soil water depletion by oak trees and the influence of root water uptake on the moisture content-diameter closed top chamber using a three-dimensional measurement grid of soil moisture and pressure and moisture content spatial perturbations, is comparable to the contribution from soil hydraulic properties

  14. System for high throughput water extraction from soil material for stable isotope analysis of water

    Technology Transfer Automated Retrieval System (TEKTRAN)

    A major limitation in the use of stable isotope of water in ecological studies is the time that is required to extract water from soil and plant samples. Using vacuum distillation the extraction time can be less than one hour per sample. Therefore, assembling a distillation system that can process m...

  15. In situ estimation of soil hydraulic functions using a multistep soil-water extraction technique

    NASA Astrophysics Data System (ADS)

    Inoue, M.; Å Imunek, J.; Hopmans, J. W.; Clausnitzer, V.

    1998-05-01

    Estimation of the retention and unsaturated hydraulic conductivity functions is essential to effectively provide input for water flow and transport simulation and prediction. A parameter optimization procedure is shown as a promising tool to estimate inversely these hydraulic function parameters from transient soil matric potential and cumulative soil solution extraction measurements. Sensitivity analyses from synthetic data generated from forward numerical model simulations showed that optimum tensiometer locations will depend on soil type. Experiments were carried out in both a laboratory column (Columbia sandy loam) and in the field (Yolo silt loam). In both cases a series of vacuum extraction pressures was applied to a ceramic soil solution sampler, and cumulative soil solution extraction volume and matric potentials at various positions near the extraction device were monitored as the soil solution was extracted. In the laboratory a zero-flux boundary condition was maintained at the bottom of the column, whereas matric potential measurements were used in the field to define the lower boundary. In both the field and laboratory experiments, flow at the upper boundary was zero. Cumulative extraction volume and matric potential data were included in the objective function to be minimized to estimate the hydraulic function parameters. We determined that the optimized solution was sensitive to the contact between the ceramic ring and the surrounding soil. By also optimizing the hydraulic resistance of the ceramic ring of the extraction device, optimization improved the fit between measured and optimized flow variables. Comparison of the optimized with the independently measured hydraulic functions indicated that the in situ estimation using a multistep extraction procedure can provide accurate soil hydraulic data.

  16. Bayesian Inversion of Soil-Plant-Atmosphere Interactions for an Oak-Savanna Ecosystem Using Markov Chain Monte Carlo Method

    NASA Astrophysics Data System (ADS)

    Chen, X.; Rubin, Y.; Baldocchi, D. D.

    2005-12-01

    Understanding the interactions between soil, plant, and the atmosphere under water-stressed conditions is important for ecosystems where water availability is limited. In such ecosystems, the amount of water transferred from the soil to the atmosphere is controlled not only by weather conditions and vegetation type but also by soil water availability. Although researchers have proposed different approaches to model the impact of soil moisture on plant activities, the parameters involved are difficult to measure. However, using measurements of observed latent heat and carbon fluxes, as well as soil moisture data, Bayesian inversion methods can be employed to estimate the various model parameters. In our study, actual Evapotranspiration (ET) of an ecosystem is approximated by the Priestley-Taylor relationship, with the Priestley-Taylor coefficient modeled as a function of soil moisture content. Soil moisture limitation on root uptake is characterized in a similar manner as the Feddes' model. The inference of Bayesian inversion is processed within the framework of graphical theories. Due to the difficulty of obtaining exact inference, the Markov chain Monte Carlo (MCMC) method is implemented using a free software package, BUGS (Bayesian inference Using Gibbs Sampling). The proposed methodology is applied to a Mediterranean Oak-Savanna FLUXNET site in California, where continuous measurements of actual ET are obtained from eddy-covariance technique and soil moisture contents are monitored by several time domain reflectometry probes located within the footprint of the flux tower. After the implementation of Bayesian inversion, the posterior distributions of all the parameters exhibit enhancement in information compared to the prior distributions. The generated samples based on data in year 2003 are used to predict the actual ET in year 2004 and the prediction uncertainties are assessed in terms of confidence intervals. Our tests also reveal the usefulness of various types of soil moisture data in parameter estimation, which could be used to guide analyses of available data and planning of field data collection activities.

  17. Understanding plant-to-plant interactions for soil resources in multilayered Iberian dehesas

    NASA Astrophysics Data System (ADS)

    Moreno, G.; Rolo, V.; Cubera, E.; López-Díaz, L.

    2009-04-01

    Iberian dehesa is usually defined as two-layered silvopastoral system, where native grasses cohabit with a scattered widely-space tree layer. In the last two decades, an intense debate has been developed on the sustainability of this simplified type of dehesa. While some authors argue that that the forest cycle has been disrupted in most dehesas, where the lack of regeneration is an inherent problem to their exploitation, other authors have showed that dehesa degradation is easily reversible if certain abandonment is periodically exerted. The coexistence of two-layered plots with multilayered plots (encroached open woodlands) and mono-layered plots (either closed forest or mono-pasture/monocrops) has been a common feature of dehesas, as result of a systematic combination of agricultural, pastoral, and forestry uses. Different structures of vegetation depend on land use, giving a mosaic at both estate and landscape scales. These mosaic-type systems allow finding several scenarios of plant-to-plant interactions, mostly at belowground level. A key issue for sustainable management of oak woodland is to understand the complexity of the plant-to-plant relationships and their consequences in the ecosystem functioning in terms of productivity and stability. The competitive abilities of component systems are modified by the environment conditions. Dehesas, as most savanna systems, exhibit a low rainfall with high variability within and between years as well as a high evaporative demand during the summer. Indeed, water availability is one of the major ecological factors influencing either natural savannas or man-made open woodlands. Although most of the available studies have focused different aspects of the mature tree-grass interactions, we also present here some recent results on tree-tree, tree-shrub, shrub-seedling and seedling-grass interactions, explained mostly in terms of competition for soil water and nutrients. Trees can modify the soil and microclimate environment much more than understorey usually can, but tree characteristics often confer them a clear competitive advantage and they can strongly out-compete understorey. The net balance of positive-negative interactions varies with the age of trees: while the balance can favor grasses face to seedlings, the contrary can be expected when tree grows. Similarly, while shrubs could favor seedling recruitment, shrubs could affect negatively tree growth and productivity. These changes should be taken into account for defining dehesa structure and determining management practices in order to optimize the use of physical and chemical resources that are spatially and temporally patchy. From our results, it is described how generally holm-oak trees favor understorey forage production through a direct positive effect of shade and improved soil fertility (facilitation). The rooting system together the slow-growing attitude of many oak species could determine a low competitive potential of oaks with herbaceous layer. Its low competitiveness together with its capacity to thrive in poor soils make oaks genre very suitable for long-term agroforestry systems in Iberian Peninsula. However, although a certain complementary uses of soil resources seems occur for trees and native grasses (very distinct root system profile), the potential benefit of trees has a small actual facilitative effect because the competitive use of soil water by trees overrides its positive effects, especially under semi-arid conditions. As consequence, the net balance of trees on pasture yield is very variably with situations where pasture yield is widely increased in the vicinity of the trees and others where the contrary is found. Tree clearance practiced in dehesas affects positively the development of the understory pasture, but also the single tree functions which take advantage of the low tree density characteristic of dehesas. Tree roots access water through a large volume of soil resources (especially water) unused by pasture layer. As a consequence, lower stand density is, better tree water status, grow a

  18. Amend soils with residues from water-treatment processes

    SciTech Connect

    Makansi, J.

    1993-09-01

    This article reports that land application is emerging as a viable disposal/reuse method for water-treatment-process residues. In many cases, these residues actually enhance soil quality and arrest fertilizer loss. Water treatment usually generates solid residues requiring disposal. These include sludges from lime softening and related pretreatment processes and spent ion-exchange resins and adsorbents used for softening, dealkalization, and deionization of surface and well water. Although it may not appear so at first glance, according to consultant Dr. Robert Kunin, these materials have properties that can benefit the soil for agricultural and horticultural needs. Treating water with lime is popular and effective for removing hardness, phosphates, and some silica. Small amounts of alum, chlorine, and/or organic flocculants may also be added in lime-softening processes. Resulting sludge consists of calcium carbonate (CaCO[sub 3]), magnesium hydroxide, and calcium/magnesium/phosphate compounds, along with humic matter and related organic compounds that originate in the raw water. If softening is conducted at high temperatures, large, dense CaCO[sub 3] particles form as the compound crystallizes around sand particles. Disposal of this sludge is often considered a major disadvantage of lime softening. But if the water being treated meets EPA regulations for heavy metals, especially arsenic, then chemical analysis suggests benefits for soils. This has been well-described in texts addressing water treatment. For example, the sludge serves as a mild liming agent and may even supply various plant nutrients. Note that this application is different from municipal wastewater treatment plant sludge, which is difficult to land apply.

  19. Soil water content inverse profiling from single TDR waveforms

    NASA Astrophysics Data System (ADS)

    Greco, R.

    2006-02-01

    An inverse procedure for the estimation of soil water content profiles along TDR probes is presented. A TDR metallic probe is considered as a transmission line, for which relevant partial derivatives equations apply. The direct problem consists in the integration of transmission line equations, providing V( x, t) along the line. To this aim, the unit length parameters of the transmission line must be known. In particular, unit length capacitance C( x) and transverse conductance G( x) depend on water content distribution along the probe ?( x) through relative permittivity ?r( x) and bulk soil electrical conductivity ?( x), respectively. The inverse procedure consists in finding the water content distribution, and the relevant unit length parameters, giving rise to the best fit between the numerically simulated voltage V(x¯,t) at the beginning of the line and the experimental voltage trace V(x¯,t) measured by a cable tester. In order to reduce the ill-posedness of the inverse problem, unknown water content profiles are expressed by means of a four parameters functional form. The search for the best fitting parameters vector is carried out with a genetic algorithm. The proposed inverse procedure is successfully applied to the determination of vertical water content profiles along a soil sample in the laboratory by means of a single three rods metallic TDR probe. Water content profiles estimated either in steady flow conditions, or during controlled infiltration-evaporation transients are compared with independent water content measurements carried out by means of horizontal TDR probes at various depths, showing in all cases good agreement.

  20. Influence of Microsprinkler Irrigation Amount on Water, Soil, and pH Profiles in a Coastal Saline Soil

    PubMed Central

    Chu, Linlin; Kang, Yaohu; Wan, Shuqin

    2014-01-01

    Microsprinkler irrigation is a potential method to alleviate soil salinization. After conducting a homogeneous, highly saline, clayey, and coastal soil from the Bohai Gulf in northern China in a column experiment, the results show that the depth of the wetting front increased as the water amount applied increased, low-salinity and low-SAR enlarged after irrigation and water redistribution, and the soil pH increased with an increase in irrigation amount. We concluded that a water amount of 207?mm could be used to reclaim the coastal saline soil in northern China. PMID:25147843

  1. Modifying soil water status and improving stand establishment in a water repellent soil using surfactant coated seed.

    NASA Astrophysics Data System (ADS)

    Kostka, Stanley; Lampe, Mark; van Mondfrans, Jan; Madsen, Matthew; McMillan, Mica

    2015-04-01

    Surfactant seed coating (SSC) is a technology being developed cooperatively by scientists at the USDA, Agricultural Research Service and Aquatrols to improve stand establishment in water repellent soils, particularly under arid conditions. Early SSC studies have demonstrated that surfactant coatings can dramatically increase soil water content, turfgrass density, cover, and biomass for Kentucky bluegrass, tall fescue and perennial ryegrass sown in water repellent soils under greenhouse conditions. However, in these studies, surfactant loads were excessive (? 40 wt% of seed mass). The objective of the current study was to ascertain if a lower surfactant treatment level (10 wt%) would improve emergence and stand establishment in a severely water repellent sandy soil under field conditions. Research was conducted on a golf course near Utrecht, NL. At the time of planting water drop penetration time (WDPT) of the soil was approximately 300 s, indicating severe water repellency. Chewings fescue (Festuca rubra subsp. commutata) seed was treated with ASET-4001 surfactant at a loading rate of 10 wt% using two different proprietary coating procedures (US Patent Application 20100267554). The two different ASET-4001 coatings were compared against untreated seed in a randomized complete block design with four replicates. In order to maximize abiotic stresses, the only applied water came from rainfall. Assessments of stand establishment were made every 7-14 days for three months using a subjective visual assessment of percent grass cover and sward quality based on a 1-10 scale (where 10 is best). At six months post-sowing, 20 mm x 300 mm soil cores were randomly removed from each plot and soil wetting front depth measured. Improved emergence of the surfactant coated seeds over the untreated seeds began to appear 7 days after sowing. However, there were no differences between the two SSC treatments. Establishment was influenced by weather conditions. From mid-June to early July, ratings were similar between all treatments. However, with the onset of warmer more stressful growing conditions in mid-July, stand establishment ratings for the SSC treatments were higher than for the untreated control. From 16 July to 18 August, stand establishment ratings for the SSC treatments were between 9.1 and 9.8. In the untreated control plots, 16 July ratings were at 7.1 and dropped precipitously to 5.3 by 18 August. The visual differences between treatments suggested that rootzone water may be greater in the SSC treatments. Mean wetting front depths in cores collected from the SSC plots were at minimum 2x greater than untreated controls (200 mm vs 100 mm) confirming that SSC resulted in greater rootzone water distribution. SSC improved emergence and stand establishment of Chewings fescue and modified the soil wetting pattern in severely water repellent sand for at least six months. SSC may provide a sustainable strategy to improve turfgrass establishment under water stress conditions or when irrigation is limited.

  2. Studies of soil-structure and fluid-structure interaction

    SciTech Connect

    Prasad, A.M.

    1989-01-01

    This dissertation deals with two distinct topics: (1) The effects of soil-structure interaction, both kinematic and inertial, on the dynamic response of a variety of base-excited foundations and of simple structures supported on such foundations; and (2) the effects of fluid-structure interaction for relatively simple structural systems subjected to forces induced by waves and currents. A fundamental step in the analysis of a base-excited structure foundation system is the evaluation of the transfer functions of its foundation motion. Defined for harmonically excited massless foundations, these functions relate the amplitudes of the components of foundation motion to those of the free-field ground motion at some reference or control point. These functions are evaluated for surface supported circular and rectangular rigid foundations and for embedded square foundations considering a spatially varying, horizontal free-field ground motion. Consideration is also given to more complex ground motions defined stochastically by a local power spectral density function and a spatial incoherence function. An approximate analyses based on the Iguchi-Scanlan averaging technique is employed. The structures examined are considered to have one lateral and one torsional degree of freedom in their fixed-base condition. The response quantities examined include the ensemble means of the peak values of the lateral and torsional components of the foundation input motion and of the associated structural de formations. These responses are evaluated over wide ranges of the parameters involved and are compared with those obtained for no soil structure interaction and for kinematic interaction only. Simple, physically motivated interpretations are given for the observed differences.

  3. Water distribution measurement in soil using sound vibration

    NASA Astrophysics Data System (ADS)

    Sugimoto, Tsuneyoshi; Nakagawa, Yutaka; Shirakawa, Takashi; Sano, Motoaki; Ohaba, Motoyoshi; Shibusawa, Sakae

    2012-05-01

    Now in agriculture, it tends to save the agricultural water as much as possible. Therefore, the irrigation method using the minus pressure difference of soil water attracts attention. This method has the nature keeping the water content inside the ground. In other words, when there are crops, it is the mechanism which supplies the water content which is same quantity with the water content that it absorbed. However, effective saving water is not able to be performed, because the water distribution in soil is difficult to grasp. Therefore, we propose a method of monitoring and imaging of the water content in the rooting zone using a sound vibration and the scanning laser Doppler vibrometer (SLDV). The plastic container (40×50×30 cm) which is made from acrylic in the laboratory that had been filled with sand of uniform particle size (200 to 300 ?m) was used for this experiment. In this experiment, it measures the status of the water distribution by the change of the vibration propagation. The making method of the moisture distribution is shown below. First, the plastic container is filled with the sand into the plastic container. The water of the fixed quantity is pour into the container. A plastic container is removed after having put it in the sand tank upside down. The size of the water distribution is 14×11×10 cm. This time, the water-content of the reviewed water distribution is 200 ml, 250 ml, and 300 ml. Experiment method is shown as follows. First, there are nine holes to set up the sound source which was covered with the rubber in the sand tank base. It sends vibration with the giant magnetostriction vibrator to have installed in the hole of the sand tank base. SLDV measures the vibration of ground surface excited by sound wave caused from vibratory source. The output waveform uses the burst wave of doing 2 kHz of sine wave, 300 mVpp, 3 cycles. The scan area of SLDV is 17×23 points, the point interval is about 1.8cm. As a result, we can confirm that the distribution of the propagation velocity was a very effective method to the water distribution which is in the shallow position near the ground surface. Also, we can see that the difference of the propagation velocity distribution reflected the difference of the water distribution. We plan to measure when changing the depth of the water distribution position and the implication water ratio in the future.

  4. Closing the water balance with cosmic-ray soil moisture measurements and assessing their spatial variability within two semiarid watersheds

    NASA Astrophysics Data System (ADS)

    Schreiner-McGraw, A. P.; Vivoni, E. R.; Mascaro, G.; Franz, T. E.

    2015-06-01

    Soil moisture dynamics reflect the complex interactions of meteorological conditions with soil, vegetation and terrain properties. In this study, intermediate scale soil moisture estimates from the cosmic-ray sensing (CRS) method are evaluated for two semiarid ecosystems in the southwestern United States: a mesquite savanna at the Santa Rita Experimental Range (SRER) and a mixed shrubland at the Jornada Experimental Range (JER). Evaluations of the CRS method are performed for small watersheds instrumented with a distributed sensor network consisting of soil moisture sensor profiles, an eddy covariance tower and runoff flumes used to close the water balance. We found an excellent agreement between the CRS method and the distributed sensor network (RMSE of 0.009 and 0.013 m3 m-3 at SRER and JER) at the hourly time scale over the 19-month study period, primarily due to the inclusion of 5 cm observations of shallow soil moisture. Good agreement was obtained in soil moisture changes estimated from the CRS and watershed water balance methods (RMSE = 0.001 and 0.038 m3 m-3 at SRER and JER), with deviations due to bypassing of the CRS measurement depth during large rainfall events. This limitation, however, was used to show that drier-than-average conditions at SRER promoted plant water uptake from deeper layers, while the wetter-than-average period at JER resulted in leakage towards deeper soils. Using the distributed sensor network, we quantified the spatial variability of soil moisture in the CRS footprint and the relation between evapotranspiration and soil moisture, in both cases finding similar predictive relations at both sites that are applicable to other semiarid ecosystems in the southwestern US. Furthermore, soil moisture spatial variability was related to evapotranspiration in a manner consistent with analytical relations derived using the CRS method, opening up new possibilities for understanding land-atmosphere interactions.

  5. Water And Solute Transport In A Cracking Soil Irrigated With Saline Water In Sicily

    NASA Astrophysics Data System (ADS)

    Crescimanno, G.; Garofalo, P.

    2003-04-01

    Irrigation with saline/sodic waters, which is a current practice in many arid and semi-arid environments, involves a risk of soil degradation and desertification due to salinization and sodification. Sustainable land management practices are urgently needed to preserve the production potential of agricultural land while safeguarding environmental quality Long-term field experiments are one way to develop suitable irrigation strategies, but these are expensive, site specific and time consuming. An alternative solution is application of simulation models to be used to examine possible different combinations of existing field-conditions (soil, climate and water) and to provide an accurate and quick estimate of crop growth, water and salt-balance. Swelling/shrinking clay soils change volume with changes in water content, and during dry periods extensive cracks will form in the field. Soil cracks alter the pore-size distribution through intermittent wetting, acting as significant pathways for water and solutes and determining the occurrence of bypass flow, i.e. the rapid transport of water and solutes via shrinkage-cracks to subsoil and to groundwater through an unsaturated soil matrix. This paper provides the results of simulating water and solute transport in some clay profiles located in a Sicilian irrigated area characterized by swelling/shrinking soils susceptible to cracking and bypass flow phenomena. Simulations were performed by using the SWAP model (van Dam et al., 1997), which accounts for cracking and bypass flow. Measurement of water content and of electrical conductivity of the pore solution, carried out from 14/07/1998 to 31/12/2000, were used to validate and calibrate the model. Management scenarios were developed by using the model in order to provide suggestions for preventing salinization in the irrigated area.

  6. Fluorescent probes for understanding soil water repellency: the novel application of a chemist's tool to soil science

    NASA Astrophysics Data System (ADS)

    Balshaw, Helen M.; Davies, Matthew L.; Doerr, Stefan H.; Douglas, Peter

    2015-04-01

    Food security and production is one of the key global issues faced by society. It has become essential to work the land efficiently, through better soil management and agronomy whilst protecting the environment from air and water pollution. The failure of soil to absorb water - soil water repellency can lead to major environmental problems such as increased overland flow and soil erosion, poor uptake of agricultural chemicals, and increased risk of groundwater pollution due to the rapid transfer of contaminants and nutrient leaching through uneven wetting and preferential flow pathways. Understanding the causes of soil hydrophobicity is essential for the development of effective methods for its amelioration, supporting environmental stability and food security. Organic compounds deposited on soil mineral or aggregate surfaces have long been recognised as a major factor in causing soil water repellency. It is widely accepted that the main groups of compounds responsible are long-chain acids, alkanes and other organic compounds with hydrophobic properties. However, when reapplied to sands and soils, the degree of water repellency induced by these compounds and mixtures varied widely with compound type, amount, and mixture, in a seemingly unpredictable way. Fluorescent and phosphorescent probes are widely used in chemistry and biochemistry due to their sensitive response to their physical and chemical environment, such as polarity, and viscosity. However, they have to-date not been used to study soil water repellency. Here we present preliminary work on the evaluation of fluorescent probes as tools to study two poorly understood features that determine the degree of wettability for water repellent soils: (i) the distribution of organics on soils; (ii) the changes in polarity at soil surfaces required for water drops to infiltrate. In our initial work we have examined probes adsorbed onto model soils, prepared by adsorption of specific organics onto acid washed sand. Studies using steady-state and ?s time-resolved emission spectroscopy, together with fluorescence microscopy and image analysis, of probe lifetime, spectra, and spatial distribution have been used to 'map' the emission characteristics of probes when adsorbed, and also to examine how the distribution of hydrophobic compounds changes during contact with materials used for treating hydrophobic soils (e.g. clays, biochar). Furthermore, while it has been suggested that during soil wetting the water droplet induces changes in conformation, orientation and arrangement of a hydrophobic layer of organics adsorbed to the soil surfaces, there is little direct evidence for this, and so we are also exploring the use of fluorescent/phosphorescent probes adsorbed on the soil surface to determine any changes in environment polarity, viscosity or hydrophobicity at the soil surface during the wetting process.

  7. Groundwater-surface water interactions in fractured Mediterranean mountain environments

    NASA Astrophysics Data System (ADS)

    Eliades, Marinos; Bruggeman, Adriana; Lange, Manfred A.

    2014-05-01

    Groundwater and surface-water systems interact in a variety of geological, morphological, and climatic settings. Vegetation also plays a key role in these interactions as it transfers water from the subsurface and groundwater table towards the surface, where it is redistributed by plants and trees in different soil depths. Cyprus is at the drier end of the precipitation spectrum of the Mediterranean region and has intense seasonal variations in precipitation with frequent droughts. In order to confront water scarcity issues and improve water management plans in the future, we need to obtain a better understanding of the groundwater and surface-water interactions and quantify the hydrological processes in this complex fractured Mediterranean mountain environment. The upstream and midstream of Peristerona watershed was selected as the study area (77 km2). It is a forested mountain watershed with steep slopes (mean 22o) and elevation varying from 417 to 1543 m. The main formations in the area are lower and upper pillow lavas, basalt, diabase and gabbro. From a hydrogeological point of view the upstream area consists mainly of heavily fractured intrusive formations that can hold groundwater inside the fractured zones and in some areas it consists of plutonic rocks with springs. The midstream area is dominated by volcanics with submarine pillow lavas. To assess the surface and groundwater interactions a nested watershed approach will be followed with the synthesis and collation of hydrometric data through a dense monitoring network. Continuous measurements of rainfall, runoff and groundwater levels will be taken. Watershed characteristics will be processed in GIS environment. Also measurements of environmental stable isotopes (O18and H2) will be taken. In addition sap flow instruments will be installed in Pinus brutia species among with soil moisture sensors. Results will quantify the water uptake by trees (Pinus Brutia sp.) and the hydraulic redistribution back to the different soil depths. It will enable an assessment of the contribution of trees to the natural water cycle in situations similar to this environment. Hydrometric analysis for each nested watershed will be applied and results are expected to show threshold values of rainfall for runoff generation and the contribution of groundwater (baseflow) to the river flow and vice versa. Relations between geology, morphology and climate will also be revealed. Rainfall and runoff data are currently available from two stations, Panagia bridge (438 m) and Platanistasa (780 m). Results show a linear relation between the daily runoff of the two stations. The relatively higher runoff in Platanistasa, as compared to Panagia bridge, is probably due to the steep slopes and the higher rainfall rates. Baseflow occurring at the end of the rain season indicate that the fractures in the geologic formations fill up during the rainy season and discharge during the end of the season. During the summer period, even when rainfall events occur, there is very little or no runoff generation.

  8. Aggregating available soil water holding capacity data for crop yield models

    NASA Technical Reports Server (NTRS)

    Seubert, C. E.; Daughtry, C. S. T.; Holt, D. A.; Baumgardner, M. F.

    1984-01-01

    The total amount of water available to plants that is held against gravity in a soil is usually estimated as the amount present at -0.03 MPa average water potential minus the amount present at -1.5 MPa water potential. This value, designated available water-holding capacity (AWHC), is a very important soil characteristic that is strongly and positively correlated to the inherent productivity of soils. In various applications, including assessing soil moisture status over large areas, it is necessary to group soil types or series as to their productivity. Current methods to classify AWHC of soils consider only total capacity of soil profiles and thus may group together soils which differ greatly in AWHC as a function of depth in the profile. A general approach for evaluating quantitatively the multidimensional nature of AWHC in soils is described. Data for 902 soil profiles, representing 184 soil series, in Indiana were obtained from the Soil Characterization Laboratory at Purdue University. The AWHC for each of ten 150-mm layers in each soil was established, based on soil texture and parent material. A multivariate clustering procedure was used to classify each soil profile into one of 4, 8, or 12 classes based upon ten-dimensional AWHC values. The optimum number of classes depends on the range of AWHC in the population of oil profiles analyzed and on the sensitivity of a crop to differences in distribution of water within the soil profile.

  9. Monitoring of soil water storage along elevation transech on morphological diverse study-sites affected by soil erosion

    NASA Astrophysics Data System (ADS)

    Jaksik, Ondrej; Kodesova, Radka; Nikodem, Antonin; Fer, Miroslav; Klement, Ales; Kratina, Josef

    2015-04-01

    Soil water availability is one of the key factors determining plant growth. Spatial distribution of soil water content is influenced by many factors. For the field-scale, one of the most important factors is terrain and its shape. The goal of our study was to characterize soil water storage within the soil profile with respect to terrain attributes. Two morphologically diverse study sites were chosen, in order to monitor soil water storage during vegetation season. The first site Brumovice in located in the Southern Moravian Region. The original soil unit was Haplic Chernozem developed on loess, which was gradually degraded by soil erosion. In the steepest parts, due to substantial loss of soil material, soil is transformed to Regosol. As a result of consequently sedimentation of previously eroded material in toe slopes and terrain depressions colluvial soils are formed. The second site Vidim is placed in the Central Bohemia. Dominant soil unit in wider area is Haplic Luvisol on loess loam. Similar process of progressive soil transformation was identified. On each study site, two elevation transects were delimited, where each consists of 5 monitoring spots. Access tubes were installed in order to measure soil moisture in six different depths (10, 20, 30 40, 60 a 100 cm) using Profile Probe PR2. The monitoring was conducted during vegetation season: April - July 2012 in Brumovice and May - July 2013 in Vidim. The average soil water contents were calculated for following three layers: topsoil A (0-20 cm), subsoil B (20-40cm), and substrate (40-100cm). The soil water storage within the soil profile was also expressed. Sensors TMS3 were also used for continual soil water content monitoring in the depth of 0-15 cm. In addition undisturbed soil samples were taken from topsoil to measure soil hydraulic properties using the multistep outflow experiment. Data were used to assess retention ability of erosion affected soils. The soil water storage and particularly average soil water content of the topsoil layers were dominantly affected by evapotranspiration (which apparently depended on aspect of the slope) and secondary by soil properties change due to soil erosion especially on steep slopes. Both transects in Brumovice a one transect in Vidim were located on north-facing slopes, while one transect in Vidim was located on south-facing slope. As result higher soil water contents were observed at the steepest part of all 3 transects (north aspects). We found strong significant relationship between slope and average soil moisture for both transects in Brumovice. In the case of the south-facing transect no apparent trend of soil water content with respect to terrain position was observed. Acknowledgment: Authors acknowledge the financial support of the Ministry of Agriculture of the Czech Republic (grant No. QJ1230319).

  10. Interactions of hydrazine and of hydrazine derivatives with soil constituents and with soils. Annual report 1 dec 80-1 dec 81

    SciTech Connect

    Hayes, M.H.B.; Isaacson, P.J.; Chia, K.Y.; Lees, A.M.

    1982-01-31

    Studies have demonstrated that at high pH, in the solution phase, colloids catalyse hydrazine degradation. This catalysis is particuarly dependent upon the exchangeable metal cations held by the colloids, and exceeds that of equivalent solutions of the metal cations alone. Hydrazines can be strongly or weakly sorbed by soil colloids in essentially unchanged forms, or can be irreversibly chemisorbed. Reversible ion-exchange is the main mechanism of hydrazine/clay interaction at low pH. Insoluble iron-and aluminium-hydrous oxides form on the surfaces of suitably exchanged clays at high pH, and these bind large amounts of hydrazines by strong hydrogen-bonding forces and by hydrazination of cationic species. Such binding partially destabilises hydrazine towards thermal degradation. Hydrazines interact with humic colloids by chemisorption, by ion-exchange, and by hydrazination of strongly polarizing cations. The reactivity of humates is determined by their exchangeable metal cations, and by the pH, which both affect their penetrability and solubility. Clay colloids and goethite react strongly with hydrazines from the vapour phase. Results show that the hydrazines can compete well with water for interaction sites. Preliminary results from whole soil/hydrazine experiments show the large capacity of different soil types for interaction with hydrazines. A copper(II)-treated, aerated clay soil is highly effective in degrading applied hydrazine.

  11. Interaction between soil mineralogy and the application of crop residues on aggregate stability and hydraulic conductivity of the soil

    NASA Astrophysics Data System (ADS)

    Lado, M.; Kiptoon, R.; Bar-Tal, A.; Wakindiki, I. I. C.; Ben-Hur, M.

    2012-04-01

    One of the main goals of modern agriculture is to achieve sustainability by maintaining crop productivity while avoiding soil degradation. Intensive cultivation could lead to a reduction in soil organic matter that could affect the structure stability and hydraulic conductivity of the soil. Moreover, crops extract nutrients from the soil that are taken away from the field when harvested, and as a consequence, the addition of fertilizers to the soil is necessary to maintain crop productivity. One way to deal with these problems is to incorporate crop residues into the soil after harvest. Crop residues are a source of organic matter that could improve soil physical properties, such as aggregate stability and soil hydraulic conductivity. However, this effect could vary according to other soil properties, such as clay content, clay mineralogy, and the presence of other cementing materials in the soil (mainly carbonates and aluminum and iron oxides). In the present work, the interaction between the addition of chickpea crop residues to the soil and clay mineralogy on aggregate stability and saturated hydraulic conductivity were studied. Chickpea plant residues were added at a rate of 0.5% (w/w) to smectitic, kaolinitic, illitic and non-phyllosilicate soils from different regions. The soils without (control) and with chickpea residues were incubated for 0, 3, 7 and 30 days, and the saturated hydraulic conductivity of the soils was measured in columns after each incubation time. The response of hydraulic conductivity to the addition of residues and incubation time was different in the soils with various mineralogies, although in general, the addition of chickpea residues increased the saturated hydraulic conductivity as compared with the control soils. This positive effect of crop residues on hydraulic conductivity was mainly a result of improved aggregate stability and resistance to slaking during wetting.

  12. Analytic technique measures aromatics in soil and water

    SciTech Connect

    Roy, K.A.

    1990-12-01

    This paper reports on a technique for detecting aromatic compounds in soil and water. The technique traces its roots to a chemical reaction discovered in 1877. The reaction is an organic synthesis process that has been harnessed for the production of high-octane gasoline, synthetic rubber, plastics and synthetic detergents. More than a century later the same chemistry is used as the basis for an analytical technique that quantifies contamination caused by products.

  13. Soil, Water and Forage Testing Laboratory Potassium recommendations applicable for

    E-print Network

    80 75 70 65 60 50 40 GRAIN SORGHUM (1000 LBS/A) 20 15 15 15 10 10 10 10 10 5 5 GRAIN SORGHUM (10000 LBS/A) 150 140 130 120 110 105 100 95 90 80 70 GRAIN SORGHUM (1500 LBS/A) 20 15 15 15 10 10 10 10 10 5 5GRAIN SORGHUM (1500 LBS/A) 20 15 15 15 10 10 10 10 10 5 5 #12;Soil, Water and Forage Testing

  14. Soil-, water-, and energy-conserving tillage - Southern Plains

    SciTech Connect

    Allen, R.R.; Musick, J.T.; Unger, P.W.; Wiese, A.F.

    1981-01-01

    This paper summarizes some conservation cropping systems that have been developed through research. The cropping systems were: dryland wheat-fallow with stubble mulch, dryland wheat-chemical fallow-sorghum, irrigated wheat-chemical fallow-sorghum, irrigated sorghum double-cropped after winter wheat, and irrigated annual sorghum. For these cropping systems, the affect of tillage method upon soil water storage, crop yield, and energy use is discussed. 15 refs.

  15. Access tube devices to monitor soil water content

    NASA Astrophysics Data System (ADS)

    Cepuder, P.

    2003-04-01

    The Neutron Probe is considered to be one of the best indirect measurement-systems to obtain the soil water content. However, due to health problems and new measuring-techniques, other measurement systems have been developed and placed on the market. The IAEA in special tried hard to find alternatives to the radioactive measurement-techniques. Consequently, the IAEA in co-operation with institutes from Australia, France, Austria, and the USA compared the TDR (Time Domain Reflectometry) and the FDR (Frequency Domain Reflectometry) to the radioactive Neutron Probe. During the period from June 2000 to May 2002 those three measurement-systems were tested in practice at three locations in Lower Austria (sandy, loamy, and clay soil conditions) by the Institute of Hydraulics and Rural Water-Management (University of Agricultural Sciences, Vienna). The used equipment consisted of access tube devices TRIME (TDR), DIVINER 2000 (FDR), and SOLO 40 (radioactive). Once a week, measurements of soil water content were taken every 10 cm down to a depth of 1 m with three replications each. In the course of this experiment, all systems were field-calibrated and compared to standard-calibration. Concerning the practical utilisation the Diviner by Sentek is best to handle. After comparing those three systems for more than two years, the FDR-method has proved to be better in results and handling than TDR. The availability of appropriate measurement systems to determine the soil water content is a basic prerequisite for further descriptions of subsurface flow and solute transport process as well as for agricultural aspects.

  16. Influence of development stage and disturbance of physical and biological soil crusts on soil water erosion

    NASA Astrophysics Data System (ADS)

    Chamizo, S.; Cantón, Y.; Lázaro, R.; Solé-Benet, A.; Calvo-Cases, A.; Miralles, I.; Domingo, F.

    2009-04-01

    Most soils exposed to rainfall are prone to sealing and crusting processes causing physical soil crusts (PSCs). When climate and soil stability conditions are suitable, PSCs can be consolidated by a complex community consisting of cyanobacteria, bacteria, green algae, microfungi, lichens and bryophytes, which are collectively known as biological soil crust (BSC). The influence of soil crusts on erosion processes is complex: crusts may reduce detachment, increasing soil stability and protecting soil against raindrop impact, although that protection will depend on the type of soil crust and the stage of development; they can also build up runoff, suggesting that downstream erosion may actually be increased or favoured water harvesting to vegetated areas. On the other hand, BSCs have been demonstrated to be very vulnerable to disturbance which in turn can lead to accelerate soil erosion and other forms of land degradation. Incorporation of the response of different type of soil crusts and the effects of their disturbance is highly likely to improve the prediction of runoff and water erosion models in arid and semi-arid catchments. The objective of this work is to analyse the erosional response of PSCs and BSCs in different stages of their development and subject to distinct disturbances when extreme rainfalls intensities are applied at plot scale in semiarid environments. Small plots on the most representative crust types, corresponding to different stages of crust development, in two semiarid ecosystems in SE Spain, El Cautivo (in the Tabernas Desert) and Amoladeras (in the Natural Park Cabo de Gata-Níjar), were selected and three disturbance treatments were applied on each crust type: a) no disturbance (control), b) trampling, stepping 100 times over the crust and c) scraping. Two consecutive rainfall simulation experiments (50 mm/h rainfall intensity) were carried out on each plot: the first on dry soil and the second, 30 minutes later, on wet soil conditions. Samples of runoff were collected regularly during the rainfall simulation and sediments in runoff extracted later in laboratory. Erosion rates were significantly different at both sites, being lower in Amoladeras than in El Cautivo due to a flatter topography and a higher infiltration capacity of the sandy soils with higher organic matter content. There were not significant differences on total erosion rates between the first and the second rainfall event, as consequence of the increase of runoff under wet conditions. In El Cautivo, the erosion rates significantly decreased as crust development stage increased. However, in Amoladeras, the erosion was low in all crust types and there were not significant differences on erosion rates among the crust development stages. Among treatments, in El Cautivo, scraping and trampling promoted significant higher erosion rates than undisturbed crust, but no significant differences were found between both treatments, except for the lichen-dominated crust. In Amoladeras, no significant differences on erosion rates between the undisturbed and the trampled crust were found since in this area trampling did not have an important effect. Although the removal of the crust in semiarid environments, at local scale, always increased erosion, the effects of crust disturbance on erosion varied depending on the ecosystem, with stronger erosional effects in badland areas with a silty substrate and steep topography than in areas with a flat topography and a coarser soil texture.

  17. Polyamines and ethylene interact in rice grains in response to soil drying during grain filling.

    PubMed

    Chen, Tingting; Xu, Yunji; Wang, Jingchao; Wang, Zhiqin; Yang, Jianchang; Zhang, Jianhua

    2013-05-01

    This study tested the hypothesis that the interaction between polyamines and ethylene may mediate the effects of soil drying on grain filling of rice (Oryza sativa L.). Two rice cultivars were pot grown. Three treatments, well-watered, moderate soil drying (MD), and severe soil drying (SD), were imposed from 8 d post-anthesis until maturity. The endosperm cell division rate, grain-filling rate, and grain weight of earlier flowering superior spikelets showed no significant differences among the three treatments. However, those of the later flowering inferior spikelets were significantly increased under MD and significantly reduced under SD when compared with those which were well watered. The two cultivars showed the same tendencies. MD increased the contents of free spermidine (Spd) and free spermine (Spm), the activities of S-adenosyl-L-methionine decarboxylase and Spd synthase, and expression levels of polyamine synthesis genes, and decreased the ethylene evolution rate, the contents of 1-aminocylopropane-1-carboxylic acid (ACC) and hydrogen peroxide, the activities of ACC synthase, ACC oxidase, and polyamine oxidase, and the expression levels of ethylene synthesis genes in inferior spikelets. SD exhibited the opposite effects. Application of Spd, Spm, or an inhibitor of ethylene synthesis to rice panicles significantly reduced ethylene and ACC levels, but significantly increased Spd and Spm contents, grain-filling rate, and grain weight of inferior spikelets. The results were reversed when ACC or an inhibitor of Spd and Spm synthesis was applied. The results suggest that a potential metabolic interaction between polyamines and ethylene biosynthesis responds to soil drying and mediates the grain filling of inferior spikelets in rice. PMID:23606413

  18. Spatial variability in the soil water content of a Mediterranean agroforestry system with high soil heterogeneity

    NASA Astrophysics Data System (ADS)

    Molina, Antonio Jaime; Llorens, Pilar; Aranda, Xavier; Savé, Robert; Biel, Carmen

    2013-04-01

    Variability of soil water content is known to increase with the size of spatial domain in which measurements are taken. At field scale, heterogeneity in soil, vegetation, topography, water input volume and management affects, among other factors, hydrologic plot behaviour under different mean soil water contents. The present work studies how the spatial variability of soil water content (SWC) is affected by soil type (texture, percentage of stones and the combination of them) in a timber-orientated plantation of cherry tree (Prunus avium) under Mediterranean climatic conditions. The experimental design is a randomized block one with 3 blocks * 4 treatments, based on two factors: irrigation (6 plots irrigated versus 6 plots not irrigated) and soil management (6 plots tillaged versus 6 plots not tillaged). SWC is continuously measured at 25, 50 and 100 cm depth with FDR sensors, located at two positions in each treatment: under tree influence and 2.5 m apart. This study presents the results of the monitoring during 2012 of the 24 sensors located at the 25 cm depth. In each of the measurement point, texture and percentage of stones were measured. Sandy-loam, sandy-clay-loam and loam textures were found together with a percentage of stones ranging from 20 to 70 %. The results indicated that the relationship between the daily mean SWC and its standard deviation, a common procedure used to study spatial variability, changed with texture, percentage of stones and the estimation of field capacity from the combination of both. Temporal stability analysis of SWC showed a clear pattern related to field capacity, with the measurement points of the sandy-loam texture and the high percentage of stones showing the maximun negative diference with the global mean. The high range in the mean relative difference observed (± 75 %), could indicate that the studied plot may be considered as a good field-laboratory to extrapolate results at higher spatial scales. Furthermore, the pattern in the temporal stability of tree growth was clearly related to that one in SWC. Nevertheless, the treatments that represent the mean conditions in growth were not exactly the same than those in SWC, which could be attributable to other characteristics than soil.

  19. Soil-water fluxes modelling in a green roof

    NASA Astrophysics Data System (ADS)

    Lamera, Carlotta; Rulli, Maria Cristina; Becciu, Gianfranco; Rosso, Renzo

    2014-05-01

    Green roofs differ from a natural environment as they are on top of a building and are not connected to the natural ground; therefore it is critical that soils can drain and retain water simultaneously and that they work even in very shallow systems. The soil or growing medium used for green roofs is specifically engineered to provide the vegetation with nutrients, discharging any excess water into the drainage layer, and releasing stored water back into the substrate. In this way, medium depth and porosity plays an important role in stormwater retention and plant growth in a green roof. Due to the lack of a good understanding about the hydraulic efficiency of each green roof's layer in rainwater management, a detailed analysis of the hydrological dynamics, connected with the green roof technical design is essential in order to obtain a full characterization of the hydrologic behavior of a green roof system and its effects on the urban water cycle components. The purpose of this research is analyzing the soil-water dynamics through the different components of a green roof and modeling these processes though a detailed but clear subsurface hydrology module, based on green roof vertical soil water movement reproduction, in relation to climate forcing, basic technology components and geometric characteristics of green roof systems (thickness of the stratigraphy, soil layers and materials, vegetation typology and density). A multi-layer bucket model has been applied to examine the hydrological response of the green roof system under a temperate maritime climate, by varying the physical and geometric parameters that characterize the different components of the vegetated cover. Following a stage of validation and calibration, results confirm the suitability of the model to describe the hydrologic response of the green roof during the observed rainfall events: the discharge hydrograph profile, volume and timing, predicted by the model, matched experimental measurements rather good, as demonstrated by the limited Nash-Sutcliffe model efficiency coefficient obtained both for the total discharged volume and the peak flow. The relative percentage deviations, obtained for the total discharged volume and the peak flow at event scale, shows that the model slightly tends to overestimate the effluent volume and underestimates the peak flow rate.

  20. Determination of antibiotic residues in manure, soil, and surface waters

    USGS Publications Warehouse

    Christian, T.; Schneider, R.J.; Farber, H.A.; Skutlarek, D.; Meyer, M.T.; Goldbach, H.E.

    2003-01-01

    In the last years more and more often detections of antimicrobially active compounds ("antibiotics") in surface waters have been reported. As a possible input pathway in most cases municipal sewage has been discussed. But as an input from the realm of agriculture is conceivable as well, in this study it should be investigated if an input can occur via the pathway application of liquid manure on fields with the subsequent mechanisms surface run-off/interflow, leaching, and drift. For this purpose a series of surface waters, soils, and liquid manures from North Rhine-Westphalia (Northwestern Germany) were sampled and analyzed for up to 29 compounds by HPLC-MS/MS. In each of the surface waters antibiotics could be detected. The highest concentrations were found in samples from spring (300 ng/L of erythromycin). Some of the substances detected (e.g., tylosin), as well as characteristics in the landscape suggest an input from agriculture in some particular cases. In the investigation of different liquid manure samples by a fast immunoassay method sulfadimidine could be detected in the range of 1...2 mg/kg. Soil that had been fertilized with this liquid manure showed a content of sulfadimidine extractable by accelerated solvent extraction (ASE) of 15 ??g/kg dry weight even 7 months after the application. This indicates the high stability of some antibiotics in manure and soil.

  1. Model development for prediction of soil water dynamics in plant production.

    PubMed

    Hu, Zhengfeng; Jin, Huixia; Zhang, Kefeng

    2015-09-01

    Optimizing water use in agriculture and medicinal plants is crucially important worldwide. Soil sensor-controlled irrigation systems are increasingly becoming available. However it is questionable whether irrigation scheduling based on soil measurements in the top soil could make best use of water for deep-rooted crops. In this study a mechanistic model was employed to investigate water extraction by a deep-rooted cabbage crop from the soil profile throughout crop growth. The model accounts all key processes governing water dynamics in the soil-plant-atmosphere system. Results show that the subsoil provides a significant proportion of the seasonal transpiration, about a third of water transpired over the whole growing season. This suggests that soil water in the entire root zone should be taken into consideration in irrigation scheduling, and for sensor-controlled irrigation systems sensors in the subsoil are essential for detecting soil water status for deep-rooted crops. PMID:26525032

  2. HPx - a tool for simulating interactive biohydrogeochemical processes in soil systems

    NASA Astrophysics Data System (ADS)

    Jacques, Diederik; Simunek, Jirka

    2014-05-01

    During the last two decades, different numerical codes have been developed capable of simulating interactive physical, hydrological, biological, and geochemical processes in porous media. The simulator HPx, which couples the HYDRUS codes with PHREEQC, is one of the state-of-the-art models, which specializes in variably-saturated soil systems and explicitly accounts for atmospheric boundary conditions (precipitation and potential evapotranspiration) and root water uptake. It combines most of the advanced features of the two individual codes (Jacques et al., 2008). The versatility of the HPx code is illustrated in this presentation using several examples. An overview of different physical and geochemical conceptual models is also provided. The first example shows the results of a benchmark test, in which combined effects of mineral dissolution and precipitation on changes in physical properties during both porosity increase and clogging were simulated. The second example illustrates the flexibility of the model to include a soil organic matter submodel when simultaneously simulating organic matter degradation and CO2 diffusion in a variably-saturated soil. Since the HPx codes also simulate heat transport in the soil, they can account for fluctuations of kinetic parameters throughout the year due to their temperature dependency. Global seasonal variations in soil pCO2 and soil organic pools followed expected behavior, whereas daily values of soil pCO2 clearly exhibited the effects of daily and spatially variable temperatures and water contents on the biologically-controlled kinetic parameters. The last example illustrates the inclusion of various conceptual models for root solute uptake into the HPx modeling framework. Due to close link with the chemistry of pore water, parameters needed in the uptake equations may depend, in addition to their dependency on root system and ion uptake characteristics, also on the geochemistry of the system, resulting in time-dependency of solute uptake. Jacques, D., Šim?nek, J., Mallants, D., van Genuchten, M.T., 2008. Modeling Coupled Hydrologic and Chemical Processes: Long-Term Uranium Transport following Phosphorus Fertilization. Vadose Zone Journal 7, 698-711.

  3. 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 data indicate shallow low resistivity layers on the western side of the stream. All these findings indicate a catchment with at least two different hydrogeological settings. To further investigate the spatial variation along the stream we plan to finish the hydrogeological interpretation and build a model and on this basis choose appropriate locations for further monitoring of discharge at different spatial scales (gaging stations), monitoring hydraulic head variations and quantifying hydraulic parameters (piezometers), mapping the shallow subsurface more detailed (DC/IP) and qualifying flow components at representative stream sections through temperature methods (temperature loggers and distributed temperature sensing). We will present an overview of the initial investigations in a poster.

  4. [Characteristics of Hydrogen and Oxygen Isotopes of Soil Water in the Water Source Area of Yuanyang Terrace].

    PubMed

    Zhang, Xiao-juan; Song, Wei-feng; Wu, Jin-kui; Wang, Zhuo-juan

    2015-06-01

    Stable isotope techniques provide a new approach to study soil water movement. The precipitation and the soil water from 0 to 100 cm soil layer in 4 kinds of typical vegetation types (forest, shrub forest, grassland and non-forest land) over the water source area of Yuanyang terrace were sampled, and their isotope compositions were analyzed, aimed to understand the characteristics of stable isotopes in different depth of the soil water. The results showed that the meteoric water line in the water source area of Yuanyang terrace was ?D = 6.838 4?(18)O-5.6921 (R2 = 0.8787, n = 20), the slope and intercept were less than the global atmospheric precipitation. The hydrogen and oxygen stable isotopes in the soil water of the 4 kinds of typical types was lower than the local meteoric water line side and the fluctuation of isotope value on surface soil profile was greater. With the increasing soil depth, the fluctuation of delta 18O value was smaller and smaller, especially in the 80-100 cm soil layer which was the most obvious. The delta 18O values of the deep soil water in forest and grassland were higher than that in the surface soil. while it was on the contrary in shrub forest and non-forest land. PMID:26387313

  5. The effect of soil water repellency on water and chemicals distribution in the soil profile for effluent and fresh water irrigation

    NASA Astrophysics Data System (ADS)

    Wallach, Rony; Rahav, Matan; Brindt, Naaran; Furman, Alex

    2015-04-01

    Water repellency (WR) has been reported for many vegetation types and soils and for effluent irrigation. Citrus trees have been found in a previous and in the current study to render sandy soils hydrophobic. The presented study focuses on the synergistic effect of the uneven wetting patterns and preferential flow pathways, known to occur in WR soils, and irrigation water quality on the spatial distribution of salinity and nutrients in the citrus trees' root zone. The study was performed in a commercial grapefruit orchard that is located at the coastal plain of Israel. The soil is sandy (80 % sand, 9 % silt and 11% clay). An experimental orchard area of 1500 m2 was divided into ten plots - five are irrigated with fresh water and five with secondary treated sewage water (effluent) using a drip irrigation system. Each plot contains 12 trees with spacing of 2x6 m. Soil texture, water repellency persistence (WDPT), and OM were measured for all 10 plots. The spatial and temporal water content distribution in the trees' root zone during and between subsequent irrigation events was measured undisturbedly by the electrical resistivity tomography (ERT) method. Soil water content within the root zone was indeed found highly heterogeneous in space and in time. Using ERT scans, two sites with relatively wet soil underneath and two with relatively dry soil underneath were chosen in each plot for further investigation. Disturbed soil samples from two depths, 0-20 and 20-40 cm, were taken from each site and tested in the laboratory for weight-based saturation, current water content, pH, EC, Cl, Na, Mg, NO3, P, K, and OM. The overall finding was that the uneven distribution of water content in the water repellent soil has a substantial effect on the salinity and nutrients distribution in the soil profile. Higher salinity and nutrients concentrations were found in the effluent irrigated plots compared to the fresh water plots. In particular, salinity was higher in the dry spots and the shallow layer compared to the wet spots and the deeper layer, respectively, for both effluent and fresh water plots. The SAR was substantially higher in the effluent irrigated plots. Compared to the effluent plots where there were no differences between the wet and dry sites, the SAR in the fresh water plots was significantly higher in the dry sites. Na and Cl were higher in the effluent irrigated plots, and higher in the drier sites in all plots. The nitrate was substantially higher in the effluent plots at all depths and water contents. In addition, nitrate concentration was higher in drier sites and in the shallow layer for both effluent- and freshwater-irrigated plots. Phosphorus concentration was substantially higher in the effluent than in fresh water irrigated plots. However, as opposed to the commonly known P distribution in soil profiles, its concentration in the current study was similar at both depths. Mg and K had not distinct differences among all plots. The OM concentration was higher