Sample records for soil water interactions

  1. Simulation of land use–soil interactive effects on water and sediment yields at watershed scale

    Microsoft Academic Search

    Xixi Wang; Shiyou Shang; Wanhong Yang; Calvin R. Clary; Dawen Yang

    2010-01-01

    Influences of vegetation management on soil erosion have been extensively studied. However, interactive effects between land use and soil are poorly documented in literature. Given the importance of understanding such effects for successful watershed management, the objective of this study was to examine the land use–soil interactive effects on water and sediment yields for the 117,845-ha drainage area upstream of

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  3. 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.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    SciTech Connect

    Waugh, W.J.; Link, S.O. (Pacific Northwest Lab., Richland, WA (USA))

    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.

  8. 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.

  9. Soil nutrients and water availability interact to influence willow growth and chemistry but not leaf beetle performance

    Microsoft Academic Search

    Steven S. Lower; Colin M. Orians

    2003-01-01

    We investigated the effects of soil nutrient and water availability on the growth and chemistry of the silky willow ( Salix sericea Marshall), and on the performance of the imported willow leaf beetle ( Plagiodera versicolora Laichartig). Our major aims were to determine whether there are nutrient-water interactions on plant traits and whether this leads to parallel interactions for herbivore

  10. Interaction with Soil Microorganisms

    Microsoft Academic Search

    R. Hampp; M. T. Tarkka

    \\u000a Plant roots form a part of a multitude of organismic interactions within the soil. Due to the release of organic compounds\\u000a they attract diversified microbiological populations where fungi and bacteria can form distinct communities. In this root\\u000a sphere (“rhizosphere”), fungi can be extremely helpful for the plant in facilitating the supply of water and nutrients (mycorrhiza),\\u000a but also detrimental, if

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

    PubMed Central

    Merdun, Hasan

    2012-01-01

    Surface-applied chemicals move through the unsaturated zone with complex flow and transport processes due to soil heterogeneity and reach the saturated zone, resulting in groundwater contamination. Such complex processes need to be studied by advanced measurement and modeling techniques to protect soil and water resources from contamination. In this study, the interactive effects of factors like soil structure, initial soil water content (SWC), and application rate on preferential flow and transport were studied in a sandy loam field soil using measurement (by time domain reflectometry (TDR)) and modeling (by MACRO and VS2DTI) techniques. In addition, statistical analyses were performed to compare the means of the measured and modeled SWC and EC, and solute transport parameters (pore water velocity and dispersion coefficient) in 12 treatments. Research results showed that even though the effects of soil structural conditions on water and solute transport were not so clear, the applied solution moved lower depths in the profiles of wet versus dry initial SWC and high application rate versus low application rates. The effects of soil structure and initial SWC on water and solute movement could be differentiated under the interactive conditions, but the effects of the application rates were difficult to differentiate under different soil structural and initial SWC conditions. Modeling results showed that MACRO had somewhat better performance than VS2DTI in the estimation of SWC and EC with space and time, but overall both models had relatively low performances. The means of SWC, EC, and solute transport parameters of the 12 treatments were divided into some groups based on the statistical analyses, indicating different flow and transport characteristics or a certain degree nonuniform or preferential flow and transport in the soil. Conducting field experiments with more interactive factors and applying the models with different approaches may allow better understanding of flow and transport processes in addition to the simulations of them in the unsaturated zone. PMID:23012568

  12. Ecohydrological feedbacks between soil salinity and vegetation dynamics as mediated by interactions with the water table

    NASA Astrophysics Data System (ADS)

    Runyan, C.; D'Odorico, P.

    2010-12-01

    In areas with relatively shallow water tables, changes in vegetation cover may affect local hydrologic conditions and favor the accumulation of salt within different parts of the soil profile. Because most plants are sensitive to saline soil water, a salt-vegetation feedback may exist, whereby vegetation cover maintains deeper water tables and slower rates of salt accumulation. As a result of this feedback, both a state with vegetation cover, deep water table, and low salinity, and a state with sparse or no vegetation, shallow water table and high salinity can be stable. Such dynamics may be present in the Murray Darling Basin, Australia, where widespread conversion from sclerophyll woodlands and forests to agricultural use has resulted in a decrease in the water table depth that has mobilized salts accumulated in the vadose zone and strongly increased the rate at which salts are transported within the system. To investigate these dynamics, we present a model to relate vegetation-soil salinity feedbacks - mediated by hydrologic conditions - to the emergence of multiple stable states in the underlying dynamics and apply this model to the Murray Darling Basin. Results for this case study show the presence of a strong feedback resulting in bistable dynamics for a wide range of environmental conditions (i.e., a range of precipitation regimes, soil textures, and salinities of irrigation and groundwater). This bistability increases the susceptibility of these systems to abrupt, highly irreversible shifts to stable bare soil, saline conditions and has important economic implications for dryland agricultural regimes worldwide as the presence of a shallow, saline water table is known to require costly remediation measures.

  13. 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.

  14. 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-...

  15. 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...

  16. 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.

  17. 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...

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

    SciTech Connect

    Hakim Boukhalfa

    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.

  19. Trench water-soil chemistry and interactions at the Maxey Flats Site

    SciTech Connect

    Weiss, A. J.; Czyscinski, K. S.

    1980-01-01

    This report is part of an overall program designed to provide an understanding of and to monitor the behavior of existing low-level sites. This investigation will provide source term data for radionuclides and other solutes in trench waters and will describe the physical, chemical, and biological properties of the geochemical system that controls radionuclide movement. General conclusions can be made from the data in terms of source term information to be used in modeling efforts, as well as processes which may affect radionuclide migration. Trench waters are complex anoxic chemical systems which require more extensive investigation to assess their role in radionuclide retention and mobilization. No overall systematic changes in the disposal site trenches were observed during the brief sampling interval. However, changes in some radionuclide and cation concentrations were observed in several trenches. Numerous organic compounds were identified in trench waters at Maxey Flats, some of which have the potential for chelation with radionuclides. The presence of radionuclides and organic compounds in wells UB1 and UB1-A and in nearby trenches indicates communication between the wells and trench water leachates by subsurface migration. Radionuclides were also measured in the new experimental trench dug parallel to trench 27. Aerobic, anaerobic, sulfate reducing, denitrifying, and methanogenic bacteria are present in the leachate samples, and are able to grow anaerobically in trench leachates. Experimental results indicate that the observed sorption K/sub d/ is a function of both solid and liquid phase compositional variations as well as contact time. The observation that e lowest K/sub d/ results are observed with anoxic trench waters and ultrasonicated soils points to the need to use site specific materials and experimental conditions which simulate in situ conditions as closely as possible.

  20. 7 Phosphorus Modeling in Soil and Water

    E-print Network

    163 7 Phosphorus Modeling in Soil and Water Assessment Tool (SWAT) Model Indrajeet Chaubey...........................................................................164 7.2 Phosphorus Modeling in SWAT: Soil Phosphorus Interactions..................167 7.2.1 Initialization of Soil Phosphorus Levels......................................... 168 7.2.2 Mineralization

  1. Coupled stochastic dynamics of water table and soil moisture in bare soil conditions

    Microsoft Academic Search

    L. Ridolfi; P. D'Odorico; F. Laio; S. Tamea; I. Rodriguez-Iturbe

    2008-01-01

    The soil water content plays a fundamental role in a number of important environmental processes, including those involved in the water cycle, vegetation dynamics, soil biogeochemical cycles, and land-atmosphere interactions. Despite the recent efforts spent in the analytical modeling of the stochastic soil moisture dynamics in dryland ecosystems, the probabilistic characterization of the soil water balance in groundwater dependent environments

  2. Boron in irrigation water and its interactions with soil and plants: an example of municpal landfill leachate reuse

    Microsoft Academic Search

    Maja ZUPAN?I? JUSTIN

    In several countries, leachate is successfully treated by recirculation to the vegetated landfill cover, as it contains several micro and macronutrients for plant growth. However, the proportion and concentration of some parameters can negatively affect the plant growth and soil quality in the case of high leachate input. The presented research discusses B in leachate and its interactions with soil

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

    EPA Science Inventory

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

  4. Exchange of greenhouse gases between soil and atmosphere: interactions of soil physical factors and biological processes

    Microsoft Academic Search

    K. A. S MITH; F. C ONEN; K. E. D OBBIE; A. R EY

    2003-01-01

    Summary This review examines the interactions between soil physical factors and the biological processes respon- sible for the production and consumption in soils of greenhouse gases. The release of CO2 by aerobic respiration is a non-linear function of temperature over a wide range of soil water contents, but becomes a function of water content as a soil dries out. Some

  5. Indicators of nitrate in wetland surface and soil-waters: interactions of vegetation and environmental factors Hydrology and Earth System Sciences, 8(4), 663672 (2004) EGU

    E-print Network

    Paris-Sud XI, Université de

    2004-01-01

    Indicators of nitrate in wetland surface and soil-waters: interactions of vegetation were found between nitrate concentrations and structural characteristics of the wetland vegetation and environmental factors 663 Hydrology and Earth System Sciences, 8(4), 663672 (2004) © EGU Indicators of nitrate

  6. Modelling effects of soil structure on the water balance of soil–crop systems: a review

    Microsoft Academic Search

    R. D Connolly

    1998-01-01

    Poor soil structure, i.e. aggregation and porosity, is widely acknowledged as a major limitation to infiltration, redistribution and storage of water in a soil profile, leading to more runoff and erosion, reduced available water for plants and reduced crop production. Models of soil–crop systems are useful tools for evaluating interactions between soil physical condition, climate, management and crop growth. An

  7. 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...

  8. CO2 and CH4 Exchange in Interior Alaska: Interactions Between Fire, Water, Soils and Vegetation.

    NASA Astrophysics Data System (ADS)

    Myers-Smith, I. H.; McGuire, A. D.; Chapin, F. S.; Harden, J. W.

    2004-12-01

    The Alaskan interior contains large carbon reserves stored in poorly drained ecosystems. With warming, these areas of the boreal forest may experience more frequent or extensive stand replacing fires, and thus change the primary factors controlling carbon emissions. In 2001, a low-lying area of the Tanana Flood Plain adjacent to the Bonanza Creek LTER burned. Historical changes in vegetation, hydrology and fire at this site were tracked through macrofossil, charcoal and diatom analysis of peat cores. Dating the charcoal layers in the peat cores indicate four fire events in the past 800 years. The paleoecological record reveals a pattern of expansion of the bog after fire. After the most recent fire, a 30m transect was established along a moisture gradient from the center of a sphagnum dominated collapse feature into the surrounding burn. Thermocarst and subsiding soils were observed on the margin of the sphagnum bog in the three years since the fire. This has increased the anaerobic fraction of the soil profile. CO2 flux data suggest that both the dry and wet ends of the moisture gradient are sinks for CO2, with a growing season average daytime NEE of -2 ? mol CO2 m-2 s^{-1}. The moat is a CH^{4} source with an average growing season flux of 30 mg CH^{4} m^{-2} d^{-1} in the abnormally dry summer of 2004. We hypothesize that, after fire, lowland areas become wetter. This leads to high NEP, greater inputs of labile carbon, and increased CH^{4}$ efflux. However, if interior Alaska experiences more abnormally warm and dry summers like that of 2004, future CH4 production may be suppressed by the changing climate.

  9. Vegetation pattern formation due to interactions between water availability and toxicity in plant-soil feedback.

    PubMed

    Marasco, Addolorata; Iuorio, Annalisa; Cartení, Fabrizio; Bonanomi, Giuliano; Tartakovsky, Daniel M; Mazzoleni, Stefano; Giannino, Francesco

    2014-11-01

    Development of a comprehensive theory of the formation of vegetation patterns is still in progress. A prevailing view is to treat water availability as the main causal factor for the emergence of vegetation patterns. While successful in capturing the occurrence of multiple vegetation patterns in arid and semiarid regions, this hypothesis fails to explain the presence of vegetation patterns in humid environments. We explore the rich structure of a toxicity-mediated model of the vegetation pattern formation. This model consists of three PDEs accounting for a dynamic balance between biomass, water, and toxic compounds. Different (ecologically feasible) regions of the model's parameter space give rise to stable spatial vegetation patterns in Turing and non-Turing regimes. Strong negative feedback gives rise to dynamic spatial patterns that continuously move in space while retaining their stable topology. PMID:25338554

  10. soils.ifas.ufl.edu Soil & Water Science Department

    E-print Network

    Watson, Craig A.

    soils.ifas.ufl.edu UF/IFAS Soil & Water Science Department DISTANCE EDUCATION GRADUATE PROGRAMS #12;SOIL AND WATER SCIENCE DEPARTMENT The Soil and Water Science Department at the University of Florida in agricultural science. #12;CERTIFICATE PROGRAMS The Soil and Water Science Department also offers several

  11. 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

    and agronomical challenges, rapid population growth, and the effects of adverse climate change. These causes however, are linked to complex interactions, constraints and dependencies amongst the key physical resources in food systems, namely – Water, Land, Energy...

  12. 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.

  13. 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

  14. 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.

  15. 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)

  16. 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...

  17. 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.

  18. Alkali Soils, Irrigation Waters.

    E-print Network

    Fraps, G. S. (George Stronach)

    1910-01-01

    ro~vth entirely. orclinary "al!;ali"salts are sulphate of soda, chloride of soda, and ~te of soda. The s~,lts first named, when crystallized in the suv- the soil: appear3 :IS ~cqhife substances, ancl generally form what ia as white n77cali.... Carbonate of soda has a corrosive action trpon receranle matter (usually found in the soil) produci~lg a black solution or substance, and for this reason is called b7nck a7kali. Carbonate of so~la is esp~ciallv injurious, for it causes the soil to become...

  19. The impact of water–rock interaction and vegetation on calcium isotope fractionation in soil- and stream waters of a small, forested catchment (the Strengbach case)

    Microsoft Academic Search

    B. Cenki-Tok; F. Chabaux; D. Lemarchand; A.-D. Schmitt; M.-C. Pierret; D. Viville; M.-L. Bagard; P. Stille

    2009-01-01

    This study aims to constrain the factors controlling the calcium isotopic compositions in surface waters, especially the respective role of vegetation and water–rock interactions on Ca isotope fractionation in a continental forested ecosystem. The approach is to follow changes in space and time of the isotopic composition and concentration of Ca along its pathway through the hydro-geochemical reservoirs from atmospheric

  20. 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.

  1. Soil and Water Conservation Spring 2014

    E-print Network

    Ma, Lena

    SWS 4233 Soil and Water Conservation Spring 2014 Instructor Susan Curry scurry@ufl.edu 352 equations and reduction practices, government conservation programs; water conservation, irrigation students with an understanding of the interconnectedness of soil and water conservation. The course

  2. 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...

  3. Soil and Water Conservation Spring 2014

    E-print Network

    Ma, Lena

    1 SWS 4233 Soil and Water Conservation 3 Credits Spring 2014 Instructor Susan Curry scurry, government conservation programs; water conservation, irrigation, drainage and salinity; stormwater of the interconnectedness of soil and water conservation. The course focusses on soil and water management as it relates

  4. The effect of soil water upon soil albedo 

    E-print Network

    Graser, Elizabeth Annette

    1981-01-01

    , and volumetric water content data with corresponding =enith angle, and sky cover characteristics for the Arenosa soil. 83 Albedo, water potential, and volumetric water content data with corresponding enith angle, and sky cover characteristics for the Lufkin... soil. 84 Page A. 7 Albedo, water potential, and volumetric water content data with corresponding =enith angle, and sky cover characteristics for the Norwood soil. 85 xa LIST OF FIGURES Figure Page Geometry of the sensor, the shield, and the view...

  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. The effect of soil water upon soil albedo

    E-print Network

    Graser, Elizabeth Annette

    1981-01-01

    Particle Size Distribution 5. 1. 3 Specific Surface . Water Characteristic Relations 5. 2. 1 Arenosa Soil 5. Z. 2 Lufkin Soil 5. Z. 3 Norwood Soil 35 35 35 37 37 37 40 42 5. 3 5. 4 Comparison of the LI-COR Pyranometer Sensor to a Standard... Pyranometer Shield Factor 45 5. 5 Relation Between Albedo and Water Potential 48 5. 5. 1 Arenosa Soil 5. 5. Z Lufkin Soil 5. 5. 3 Norwood Soil 5. 5. 4 Comparison of the Relations 51 53 55 5. 6 Relation Between Albedo and Water Content . 5. 7...

  7. WATER INFILTRATION THROUGH DIESEL-CONTAMINATED SOIL

    Microsoft Academic Search

    Jamal Abu-Ashour; Abul Basher Shahalam

    2002-01-01

    The water infiltration characteristics through soil contaminated by diesel was investigated. Columns were packed with soil containing 15, 10, 5, 1, and 0 percent diesel on mass basis. Two soil types were used, namely, clay loam and sand. The results showed that the water infiltration rate through clay loam soil containing 1 percent diesel was about 50 percent of its

  8. Soil Water Modeling and Remote Sensing

    Microsoft Academic Search

    THOMAS J. JACKSON

    1986-01-01

    Soil water modeling research conducted as part of the AgRISTARS Soil Moisture project was reviewed along with other relevant studies. Research was categorized as follows: reviews of models, development of simulation models, integrating remotely sensed data and models, surface versus profile soil moisture, and estimating soil water properties. This review and evaluation found that some of the major objectives of

  9. CROP & SOIL SCIENCES Water Policy and Management

    E-print Network

    Arnold, Jonathan

    CROP & SOIL SCIENCES Water Policy and Management Committee Membership Dr. David Radcliffe - committee chair Dr. George Vellidis Department of Crop & Soil Sciences Department of Crop & Soil Sciences & Soil Sciences Department of Crop & Soil Sciences University of Georgia University of Georgia Stripling

  10. Irrigation Monitoring with Soil Water Sensors 

    E-print Network

    Enciso, Juan; Porter, Dana; Peries, Xavier

    2007-01-19

    Monitoring soil water content is essential if growers want to optimize production, conserve water, reduce environmental impacts and save money. This publication illustrates how soil moisture monitoring can improve irrigation decisions and how...

  11. 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.

  12. Soil–geosynthetic interaction: Modelling and analysis

    Microsoft Academic Search

    Ennio Marques Palmeira

    2009-01-01

    Interaction between soils and geosynthetics is of utmost importance in applications of these materials as reinforcement in geotechnical engineering. That is also the case for some applications of geosynthetics in environmental protection works. The mechanisms of soil–geosynthetic interaction can be very complex, depending on the type and properties of the geosynthetic and the soil. This paper presents and discusses some

  13. On-Farm Soil Monitoring for Water

    E-print Network

    Holland, Jeffrey

    On-Farm Soil Monitoring for Water Resource Protection WQ-43 Purdue University Cooperative Extension. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 On-farm soil monitoring methods and what they indicate 1. Water infiltration rate forimproveddecisionmakingandfieldmanagementpractices. #12;2 On-Farm Soil Monitoring for Water Resource Protection Purdue University Cooperative

  14. Trees, soil and water : Journey to Forever

    NSDL National Science Digital Library

    Keith Addison

    2001-01-01

    Trees, soil and water: Journey to Forever - healthcare for mountains, trees for deserts, trees for people, forest, forestry, deforestation, erosion, soil conservation, water conservation, desertification This article discusses the interdependence between trees, soil, and water from a biological and conservationist standpoint.

  15. Distributed Hydrological Model with New Soil Water Parameterization for Integrating Remotely Sensed Soil Moisture at Watershed Scale

    Microsoft Academic Search

    Zhang Wanchang; Chen Jiongfeng

    2008-01-01

    Detailed vertical soil moisture profile is essential for hydrological modeling and is also often used as important diagnostic information for better understanding the surface-atmospheric interactions. This paper presents a modified ESSI distributed hydrological model that is suitable for comparing and assimilating the remotely sensed soil moisture by integrating a soil water parameterization scheme which is able to numerically calculates soil

  16. 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...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  19. Field Devices for Monitoring Soil Water Content

    E-print Network

    a soil sample, usually referred to as the gravimetric method. This method expresses gravimetric water Water Content Table of Contents 1. Introduction 2. Field Methods for Soil Moisture Measurement 2 present in a sample to the mass of the soil sample after it has been oven-dried at 100-110 C to a constant

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

    EPA Science Inventory

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

  1. 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.

  2. 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.

  3. Name ___________________________________________ Soil, Water and Forage Testing Laboratory

    E-print Network

    Name ___________________________________________ Soil, Water and Forage Testing Laboratory __________________________________________ City ____________________________State_____ Zip _____ County where sampled ___________________ Phone INFORMATION (Required) (See options listed below) Laboratory # Your Sample Sample Type and Usage: Livestock

  4. 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.

  5. SOIL WATER ESTIMATION USING ELECTROMAGNETIC INDUCTION

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Two published salinity models (designated the Rhoades and Mualem - Friedman models) were examined for application to real-time soil water estimation using apparent soil electrical conductivity. Field data were collected at two sites representing a range of soil types in Central Texas: high shrinkin...

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  7. Porosity and Water Flow in Soils

    NSDL National Science Digital Library

    Tej Gautam

    Three different types of sediments will be taken and the porosity and water flow rate for each type will be determined. From this activity, students will understand concepts of porosity and water flow through soil material.

  8. 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)…

  9. SOIL AND WATER ASSESSMENT TOOL 2000

    EPA Science Inventory

    The Soil and Water Assessment Tool (SWAT), is a river basin, or watershed, scale model developed to predict the impact of land management practices on water, sediment and agricultural chemical yields in large complex watersheds with varying soils, land use and management conditio...

  10. Water as a Reagent for Soil Remediation

    SciTech Connect

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

    2003-03-06

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

  11. IRRIGATION OPTIMIZATION BY MODELING OF PLANT-SOIL INTERACTION

    E-print Network

    Boyer, Edmond

    IRRIGATION OPTIMIZATION BY MODELING OF PLANT-SOIL INTERACTION Zhongping Li Laboratory of Applied UMR G-EAU Cemagref Montpellier, France ABSTRACT Irrigation scheduling is an important issue for crop agricultural productivity. Methods to optimize crop irrigation should take into ac- count the impact of water

  12. 66 FR 30402 - Soil and Water Conservation Assistance

    Federal Register 2010, 2011, 2012, 2013, 2014

    2001-06-06

    ...DEPARTMENT OF AGRICULTURE Commodity Credit...Corporation Soil and Water Conservation...Secretary of Agriculture to use the funds for soil, water, and related...Secretary of Agriculture (Secretary...threats to soil, water, and...

  13. 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.

  14. Irrigation Monitoring with Soil Water Sensors

    E-print Network

    Enciso, Juan; Porter, Dana; Peries, Xavier

    2007-01-19

    : Hanson 2000. Figure 1. Soil water parameters and classes of water. #24; Volumetric water content is commonly used to express the soil water content. As the following shows, it is obtained by multiplying the bulk density of the soil by the gravimetric...) 50?80 Deciduous tree 50?80 Grain Vegetative growth stage Ripening stage 40?50 70?80 Lettuce 40?60 Onion 45?65 Potato 30?50 Tomato 60?150 Source: Hanson et al. 2000. Figure 3. Watermark ? sensor before installation. Figure 4. Using handheld meter...

  15. 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...

  16. 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.

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

    Microsoft Academic Search

    Marnik Vanclooster

    2010-01-01

    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

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    The spatio-temporal distribution of soil moisture influences the plant growth and the distribution of terrestrial vegetation. This effect is more evident in arid and semiarid ecosystems where the interaction between individuals and the water limited conditions play a fundamental role, providing environmental conditions which drive a variety of non-linear ecohydrological response functions (such as transpiration, photosynthesis, leakage). In this context, modeling vegetation patterns at multiple spatial aggregation scales is important to understand how different vegetation structures can modify the soil water distribution and the exchanged fluxes between soil and atmosphere. In the present paper, the effect of different spatial vegetation patterns, under different climatic scenarios, is investigated in a patchy vegetation mosaic generated by a random process of individual tree canopies and their accompanying root system. Vegetation pattern are generated using the mathematical framework proposed by Caylor et al. (2006) characterized by a three dimensional stochastic vegetation structure, based on the density, dispersion, size distribution, and allometry of individuals within a landscape. A Poisson distribution is applied to generate different distribution of individuals paying particular attention on the role of clumping on water distribution dynamics. The soil water balance is evaluated using the analytical expression proposed by Laio et al. (2001) to explore the influence of climate and vegetation patterns on soil water balance steady-state components (such as the average rates of evaporation, the root water uptake and leakage) and on the stress-weighted plant water uptake. Results of numerical simulations show that clumping may be beneficial for water use efficiency at the landscape scale. References Caylor, Kelly K., P. D'Odorico and I. Rodriguez Iturbe: On the ecohydrology of structurally heterogeneous semiarid landscape. Water Resour. Res., 28, W07424, 2006. Laio, F., A. Porporato, L., Ridolfi and I. Rodriguez Iturbe: Plants in water controlled ecosystems: Active role in hydrological processes and response to water stress, II. Probabilistic soil moisture dynamics, Adv. Water Resour., 24(7), 707-723,2001.

  19. Spatial and Statistical Similarities of Local Soil Water Fluxes

    Microsoft Academic Search

    Bing Cheng Si

    2002-01-01

    at the soil surface beneath a constant-rate rainfall simu- lator to measure cumulative water storage with time. Understanding the spatial and statistical distribution of soil water These authors estimated the local water flux from the flux in a field is fundamental for stochastic modeling soil water flow and chemical transport in spatially variable soils. The objective of slope of water

  20. 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.

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

    E-print Network

    Jawitz, James W.

    of Florida Institute of Food and Agricultural Sciences Modern Methods for Detection of Water­ and Soilborne and emerging water- and soil- borne pathogens. Laboratory demon- strations will illustrate advantages. Course enrollment is limited to 20 people and a Certificate of Completion will be issued upon con

  2. Soil water content by Karl Fischer titration

    SciTech Connect

    Prunty, L.; Zellis, M.K.; Bell, J.S. [North Dakota State Univ., Fargo, ND (United States). Dept. of Soil Science

    1997-12-31

    Specific analytical determination of water content is often desirable in contaminated soils. Karl Fischer (KF) titration is useful for this purpose, since it consumes only H{sub 2}O, even in the presence of other volatile substances. Although widely used for water content determination in industrial and food products, KF has been virtually ignored in soil and environmental science. Oven drying (OD), conversely, is considered the standard method of soil water determination, but is an indiscriminate determiner of all volatiles. The authors examined KF titration for soil water content determination. Two soil types were mixed with varying amounts of water and octane or toluene. The prepared samples containing water only, water and octane, and water and toluene were analyzed for volatile/moisture content using OD/KF analysis. Soil moisture values determined by the calibrated KF method (w{sub c}) compared favorably to those determined by OD (w{sub 0}) in terms of regression slope, intercept, correlation coefficient, and Student`s t. Regression slopes ranged from 0.980 to 1.009 while intercepts ranged from {minus}0.6 to 7.8 g kg{sup {minus}1}. Plots of the data show essentially a 1:1 correspondence of w{sub c} to w{sub o}.

  3. 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...

  4. 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...

  5. 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.

  6. 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.

  7. 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.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Analysis of the response of soil water to climate change

    SciTech Connect

    Lauenroth, W.K.I.; Burke, K.I.C.; Coffin, D.P. (Colorado State Univ., Fort Collins, CO (United States))

    1994-06-01

    We used a daily time step soil water model to investigate the potential effects of changes in temperature and precipitation on soil water dynamics in the central grassland region of the U.S.. We collected 20-years of driving variable data from each of 300 USGS weather stations throughout the region. Simulations were run for each station and the results were entered into a GIS database for analysis and display. Soil water patterns under current climatic conditions reflected the large scale west-east precipitation and south-north temperature gradients. Bare soil evaporation accounted for a large proportion of water loss in the driest areas and was replaced by canopy interception in the wettest areas. Transpiration water loss reflected the regional pattern of net primary production, highest in the warm and wet areas and lowest in the warm and dry areas. Increased temperature affected both evaporation and transpiration losses largely by increasing the length of time when evaporative demand of the atmospheric was high. Increases and decreases in precipitation affected water supply directly. Interactions between changes in elevated temperature and increased or decreased precipitation depended upon the balance of changes in water supply and demand.

  13. 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.

  14. 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...

  15. Using soil water sensors to improve irrigation management

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  16. 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

  17. Analysis of Soil Water Retention Data Using Artificial Neural Networks

    Microsoft Academic Search

    Sharad K. Jain; Vijay P. Singh

    2004-01-01

    Many studies of water flow and solute transport in the vadose zone require estimates of the unsaturated soil hydraulic properties, including the soil water retention curve ~WRC! describing the relationship between soil suction and water content. An artificial neural network ~ANN! approach was developed to describe the WRC using observed data from several soils. The ANN approach was found to

  18. Soil and xylem water potential and soil water content in contrasting Pinus contorta ecosystems, Southeastern Wyoming, USA

    Microsoft Academic Search

    T. J. Fahey; D. R. Young

    1984-01-01

    The relationships between volumetric soil water content (?), in situ soil water potential (?soil) and predawn xylem pressure potential (?predawn) were quantified in four contrasting lodgepole pine ecosystems in Wyoming, USA. On three of the sites, changes in ?soil correlated closely with ?predawn, but on a porous soil derived from coarse granitic parent material, ?predawn declines occurred much sooner than

  19. Shor Lab "Soil Water" Project Undergraduate Research Opportunity

    E-print Network

    Shor, Leslie McCabe

    Shor Lab ­ "Soil Water" Project Undergraduate Research Opportunity Primary Graduate Student: Jinzi altering soil hydraulic conductivity. The Shor and Gage labs have received a USDA grant to investigate

  20. Predicting soil-water and soil-air transport properties and their effects on soil-vapor extraction efficiency

    Microsoft Academic Search

    Tjalfe G. Poulsen; Per Moldrup; Toshiko Yamaguchi; P. Schjoenning; Jens Aage Hansen

    1999-01-01

    Accurate prediction of water and air transport parameters in variably saturated soil is necessary for modeling of soil-vapor extraction (SVE) at soil sites contaminated with volatile organic chemicals (VOCs). An expression for predicting saturated water permeability (k{sub 1,s}) in undisturbed soils from the soil total porosity and the field capacity soil-water content was developed by fitting a tortuous-tube fluid flow

  1. Soil water repellency patterns following long-term irrigation with waste water in a sandy calcareous soil, SE Spain

    Microsoft Academic Search

    J. Mataix-Solera; L. García-Irles; A. Morugán; S. H. Doerr; F. García-Orenes; I. Atanassova; M. A. Navarro; H. Ayguadé

    2009-01-01

    One of the consequences of long-term irrigation with waste water can be the development of soil water repellency (WR). Its emergence can affect soil-water balance, irrigation efficiency and crop yield. Water repellency development has been suggested to be controlled by parameters such as organic matter quantity and type present in the waste water, soil properties (particularly the texture), and the

  2. 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...

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

    ERIC Educational Resources Information Center

    Miller, Larry E.

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

  4. Enhancing Green Water in Soils of South Asia

    Microsoft Academic Search

    M. S. Kahlon; R. Lal

    2011-01-01

    Enhancing green water (GW) in soils has vast significance with respect to depleting water resources, especially in South Asia (SA). The water stored in soil that's productively used for transpiration is called GW. The enhancement of GW includes all those techniques and approaches that lead to increased soil-water storage and infiltration, reduced runoff, and decreased evaporation, such as minimum tillage,

  5. SOIL MOISTURE AND ABSORPTION OF WATER BY TREE ROOTS1

    Microsoft Academic Search

    T. T. Kozlowski

    1987-01-01

    Shade trees undergo periodic dehydration because the rate of absorption of soil water lags behind the rate of transpirational water loss from tree crowns. The rate of absorption of water from wet, warm, and well-aerated soil is controlled largely by the rate of transpiration . However, ab- sorption of water often is impeded by low soil moisture con- tent, a

  6. 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.

  7. 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...

  8. Stochastic analysis of soil-structure interaction 

    E-print Network

    Chan, Charles Cheuk Lap

    1994-01-01

    . Subsequently, the power and cross spectral density functions of the rigid foundation are compared to the input power and cross spectral density functions to determine the significance of the kinematic interaction. The subsequent analysis of inertial...-structure interaction. The term Sn(r?r?i0) is taken to be in the form of &&( ? ~, ta)=S&&(M)f(rt, r~, ta) where Sr/ca) is the spectral density matrix for any one point on the surface of the soil, and f(r?rz, &a) is a term that describes the variations in motion from...

  9. 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 database on arsenic background concentrations in urban and agricultural soils where most soil contamination spectrophotometer for total-recoverable arsenic concentrations; SAS statistical program and GIS program

  10. 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

  11. Heat Exchange in Air, Water, and Soil

    NSDL National Science Digital Library

    John Eichinger

    2009-05-30

    The Earth is composed, at least at the surface, of soil/rock, water, and air. How do the heat exchange properties of these three very different substances compare, and what effect, if any, do they have on climate and weather? This activity represents a so

  12. SOIL AND WATER ASSESSMENT TOOL (SWAT)

    EPA Science Inventory

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

  13. University of Florida Soil and Water Science Department

    E-print Network

    Ma, Lena

    University of Florida Soil and Water Science Department SWS 6932: Environmental Soil and Water Monitoring Techniques Course Syllabus General Information Credit/Contact 3 Teaching Format Sakai sampling and analytical procedures; use of common instrumentation for sample collection; quality assurance

  14. University of Florida Soil and Water Science Department

    E-print Network

    Ma, Lena

    University of Florida Soil and Water Science Department SWS 4800: Environmental Soil and Water Monitoring Techniques Course Syllabus General Information Credit/Contact 3 Teaching Format Sakai sampling and analytical procedures; use of common instrumentation for sample collection; quality assurance

  15. 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

    was related to changes in structural definition with depth. Convergence of water and solute flow is expected to increase the pollution potential of the soil because of increased bypassing of soil matrix and increased pore water velocities. Solute travel time...

  16. 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...

  17. 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...

  18. 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 ...

  19. 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 ...

  20. Climate Change Impacts on Soil and Water Conservation

    Microsoft Academic Search

    Jurgen D. Garbrecht; Jean L. Steiner; Craig A. Cox

    2007-01-01

    Planning for Extremes: Addressing Climate Change Impacts on Soil and Water Conservation, Milwaukee, Wisconsin, 1-3 November 2006 Climate change and particularly precipitation changes will affect water runoff and soil erosion from agricultural cropland, but will the change be large enough to warrant modifications in U.S. conservation policy or practice? In a 2003 report by the Soil and Water Conservation Society

  1. University of Florida Soil and Water Science Department

    E-print Network

    Ma, Lena

    public health problems by applying basic concepts from the fields of soil/water science and public healthUniversity of Florida Soil and Water Science Department SWS 4550/5551: Soils, Water, and Public Snyder, PhD, MPH Assistant Professor of Public Health Department of Health Sciences University of Alaska

  2. Post-doctoral Fellow Soil and Water Conservation Position specification

    E-print Network

    Post-doctoral Fellow Soil and Water Conservation Position specification Internationally Recruited and soil and water conservation in the context of watershed management - Identify, verify and implement and evaluate soil and water conservation measures at farm and watershed levels in cooperation with various

  3. NEZ PERCE SOIL AND WATER CONSERVATION DISTRICT CULDESAC, IDAHO 83524

    E-print Network

    NEZ PERCE SOIL AND WATER CONSERVATION DISTRICT PO BOX 131 CULDESAC, IDAHO 83524 208-843-2931 PHONE AVENUE, SUITE 1100 PORTLAND, OREGON 97204-1348 FROM: NEZ PERCE SOIL AND WATER CONSERVATION DISTRICT PROJECTS DATE: 10/4/06 Dear Council Members: The Nez Perce Soil and Water Conservation District (District

  4. 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...

  5. [Soil water and its karst effect in epikarst dynamic system].

    PubMed

    Deng, Yan; Qin, Xing-Ming; Jiang, Zhong-Cheng; Luo, Wei-Qun; Qi, Xiao-Fan

    2009-07-01

    This paper studied the soil physical properties, soil CO2, soil water and spring water chemistry in a mature forest and a shrub in Nongla of Guangxi, China, as well as the relationships between the chemistry of soil water and spring water, aimed to understand the karst effect of the soil water in Nongla epikarst dynamic system. Significant differences were observed in the soil bulk density and non-capillary porosity under forest and shrub, which affected soil water content. The fixed CO2 in soil water had a significant negative correlation with soil CO2, and the free CO2 in soil water was 0 mg x m(-3) in the forest and 5.33 x 10(3) mg x m(-3) in the shrub. In soil water and spring water, there was a negative correlation between pH and Ca2+, Mg2+, and Cl- concentrations, and a positive correlation between K+, Na+, and HCO3- concentrations and organic C content. After the eluviation of rain water, the ion concentrations in leached soil water increased greatly, and accordingly, its corrosion ability enhanced greatly. The karst process in forest environment was stable and intensive, while that in shrub environment was active but weak. PMID:19899455

  6. 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...

  7. WATER AS A REAGENT FOR SOIL REMEDIATION

    SciTech Connect

    Indira S. Jayaweera; Jordi Diaz-Ferraro

    2000-02-28

    SRI International is conducting experiments to develop and evaluate hydrothermal extraction technology for remediating petroleum-contaminated soils. Most current remediation practices generally fail (or are cost prohibitive) to remove the polycyclic aromatic hydrocarbons (PAHs) found in petroleum-contaminated sites or they require the use of organic solvents to achieve removal, 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. Initial work is being conducted at SRI to measure the solubility and rate of solubilization of selected PAHs (anthracene, fluoranthene, pyrene, and chrysene) 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. Preliminary results with pyrene and fluoranthene in water clearly indicate a significant enhancement of solubility with increase in temperature. During this quarter, we conducted experiments with pyrene in the temperature range 200 to 300 C and observed a great enhancement in solubility with an increase in temperature. We also started experiments with real-world soil samples purchased from the subcontractor.

  8. SOIL WATER MODELING IN SOUTH GEORGIA USING WEPP HYDROLOGY

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water is a fundamental component of any field or watershed scale water balance. A basin scale soil water model is being assembled using the runoff and water redistribution functions within the WEPP model. The model uses the runoff, infiltration, plant uptake, and water redistribution function...

  9. 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.

  10. Soil organic carbon covariance with soil water content; a geostatistical analysis in cropland fields

    NASA Astrophysics Data System (ADS)

    Manns, H. R.; Berg, A. A.; von Bertoldi, P.

    2013-12-01

    Soil texture has traditionally represented the rate of soil water drainage influencing soil water content (WC) in the soil characteristic curves, hydrological models and remote sensing field studies. Although soil organic carbon (OC) has been shown to significantly increase the water holding capacity of soil in individual field studies, evidence is required to consider soil OC as a significant factor in soil WC variability at the scale of a remote sensing footprint (25 km2). The relationship of soil OC to soil WC was evaluated over 50 fields during the Soil Moisture Active Passive (SMAP) soil WC field sampling campaign over southern Manitoba, Canada. On each field, soil WC was measured at 16 sample points, at 100 m spacing to 5 cm depth with Stevens hydra probe sensors on 16 sampling dates from June 7 to July 19, 2012. Soil cores were also taken at sampling sites on each field, each sampling day, to determine gravimetric moisture, bulk density and particle size distribution. On 4 of the sampling dates, soil OC was also determined by loss on ignition on the dried soil samples from all fields. Semivariograms were created from the field mean soil OC and field mean surface soil WC sampled at midrow, over all cropland fields and averaged over all sampling dates. The semivariogram models explained a distinct relationship of both soil OC and WC within the soil over a range of 5 km with a Gaussian curve. The variance in soil that soil OC and WC have in common was a similar Gaussian curve in the cross variogram. Following spatial interpolation with Kriging, the spatial maps of soil OC and WC were also very similar with high covariance over the majority of the sampling area. The close correlation between soil OC and WC suggests they are structurally related in the soil. Soil carbon could thus assist in improving downscaling methods for remotely sensed soil WC and act as a surrogate for interpolation of soil WC.

  11. Investigation of Soil Moisture - Vegetation Interactions in Oklahoma

    E-print Network

    Ford, Trenton W.

    2013-03-06

    , but not well understood climate factor. This study examines soil moisture-vegetation health interactions using both in situ observations and land surface model simulations. For the observational study, soil moisture is taken from 20 in situ Oklahoma Mesonet...

  12. Mycelium of arbuscular mycorrhizal fungi increases soil water repellency and is sufficient to maintain water-stable soil aggregates

    Microsoft Academic Search

    Matthias C. Rillig; Noor F. Mardatin; Eva F. Leifheit; Pedro M. Antunes

    2010-01-01

    Using an in vitro bioreactor system in which the arbuscular mycorrhizal (AM) fungus Glomus intraradices was grown in a soil devoid of detectable living microbes, we could show that the mycelium of this fungus contributed to the maintenance of water-stable soil aggregates and increased soil water repellency, as measured by water drop penetration time. This is to our knowledge the

  13. 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...

  14. 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.

  15. Modeling soil–root water transport and competition for single and mixed crops

    Microsoft Academic Search

    F. Lafolie; L. Bruckler; H. Ozier-Lafontaine; R. Tournebize; A. Mollier

    1999-01-01

    A knowledge of above and below ground plant interactions for water is essential to understand the performance of intercropped systems. In this work, root water potential dynamics and water uptake partitioning were compared between single crops and intercrops, using a simulation model. Four root maps having 498, 364, 431 and 431 soil-root contacts were used. In the first and second

  16. Fire induced changes in aggregate stability: the interacting effects of soil heating and ash leachate

    NASA Astrophysics Data System (ADS)

    Balfour, V.; Hatley, D.; Woods, S.

    2011-12-01

    Increases in runoff and erosion after wildfires are typically attributed to the combined effects of the loss of ground cover, water repellency and surface sealing. Surface sealing in burned areas is caused by raindrop compaction of mineral soils (structural seal formation), the clogging of soil pores by fine soil and ash, or the formation of low conductivity ash crusts (depositional seal formation). Structural sealing is more likely to occur if the fire reduces the aggregate stability of the mineral soil. Soil heating tends to reduce aggregate stability by combusting soil organic matter. Effects due to soil heating may be amplified or reduced by interactions between soil clays and ash leachate, but these effects are poorly understood. We are investigating the interacting effects of soil heating and exposure to ash leachate on the stability of soil aggregates in burned areas. During the 2011 fire season in the Rocky Mountains we collected soil samples (~1000g) from unburned areas adjacent to three recent wildfires. Soils were obtained from areas with sharply contrasting parent materials, leading to differences in the soil mineralogy. High severity ash was collected from within the burned areas. Each soil sample was divided into 6 subsamples with the first subsample acting as a control. The remaining five subsamples were heated to 100, 200, 300, 500, and 700C respectively. After heating, each subsample was split in two. Ash leachate was added to one half and DI water was added to the other half. The ash leachate was prepared by mixing 10 g of ash with 1000 mL of water in accordance with previous studies. All samples were then air dried and analyzed for porosity, bulk density, aggregate size distribution, aggregate stability and water repellency. Initial results suggest that there is an interacting effect of soil heating and exposure to ash leachate on the stability of soil aggregates, but the effect varies depending on the mineralogy of soil clays and the type of cations in the leachate. Thus, in order to predict effects of fire on soil aggregate stability it is necessary to determine not only the intensity of soil heating but also the soil clay mineralogy and the ash cation chemistry.

  17. 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.

  18. Estimating soil water evaporation using radar measurements

    NASA Technical Reports Server (NTRS)

    Sadeghi, Ali M.; Scott, H. D.; Waite, W. P.; Asrar, G.

    1988-01-01

    Field studies were conducted to evaluate the application of radar reflectivity as compared with the shortwave reflectivity (albedo) used in the Idso-Jackson equation for the estimation of daily evaporation under overcast sky and subhumid climatic conditions. Soil water content, water potential, shortwave and radar reflectivity, and soil and air temperatures were monitored during three soil drying cycles. The data from each cycle were used to calculate daily evaporation from the Idso-Jackson equation and from two other standard methods, the modified Penman and plane of zero-flux. All three methods resulted in similar estimates of evaporation under clear sky conditions; however, under overcast sky conditions, evaporation fluxes computed from the Idso-Jackson equation were consistently lower than the other two methods. The shortwave albedo values in the Idso-Jackson equation were then replaced with radar reflectivities and a new set of total daily evaporation fluxes were calculated. This resulted in a significant improvement in computed soil evaporation fluxes from the Idso-Jackson equation, and a better agreement between the three methods under overcast sky conditions.

  19. Nitrogen in Desert Grasses as Affected by Biosolids, their Time of Application, and Soil Water Content

    Microsoft Academic Search

    RICARDO MATA-GONZÁLEZ; RONALD E. SOSEBEE; CHANGGUI WAN

    2004-01-01

    This study evaluated the interactive effect of biosolids, time of application, and soil water on plant N concentration and uptake by Bouteloua gracilis (blue grama) and Hilaria mutica (tobosagrass) grown in pots. Biosolids were surface-applied to the soil of the pots either in the spring or the summer at rates of 0, 7, 18, 34, and 90 dry Mg ha.

  20. Ad Hoc Modeling of Root Zone Soil Water with Landsat Imagery and Terrain and Soils Data

    PubMed Central

    Sankey, Joel B.; Lawrence, Rick L.; Wraith, Jon M.

    2008-01-01

    Agricultural producers require knowledge of soil water at plant rooting depths, while many remote sensing studies have focused on surface soil water or mechanistic models that are not easily parameterized. We developed site-specific empirical models to predict spring soil water content for two Montana ranches. Calibration data sample sizes were based on the estimated variability of soil water and the desired level of precision for the soil water estimates. Models used Landsat imagery, a digital elevation model, and a soil survey as predictor variables. Our objectives were to see whether soil water could be predicted accurately with easily obtainable calibration data and predictor variables and to consider the relative influence of the three sources of predictor variables. Independent validation showed that multiple regression models predicted soil water with average error (RMSD) within 0.04 mass water content. This was similar to the accuracy expected based on a statistical power test based on our sample size (n = 41 and n = 50). Improved prediction precision could be achieved with additional calibration samples, and range managers can readily balance the desired level of precision with the amount of effort to collect calibration data. Spring soil water prediction effectively utilized a combination of land surface imagery, terrain data, and subsurface soil characterization data. Ranchers could use accurate spring soil water content predictions to set stocking rates. Such management can help ensure that water, soil, and vegetation resources are used conservatively in irrigated and non-irrigated rangeland systems.

  1. The influence of soil texture on the soil water dynamics and vegetation structure of a shortgrass steppe ecosystem

    Microsoft Academic Search

    M. B. Dodd; W. K. Lauenroth

    1997-01-01

    We analyzed soil water data from three sites with different soil textures in the shortgrass steppe of northeastern Colorado, USA. Our objective was to evaluate the relationship between the occurrence of plant functional types and the effect of soil texture on soil water availability. Soil water availability was greatest in the upper soil layers at all three sites, but the

  2. 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.

  3. 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.

  4. Climate change impacts on soil and water conservation

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  5. Water status of soil and vegetation in a shortgrass steppe

    Microsoft Academic Search

    O. E. Sala; W. K. Lauenroth; W. J. Parton; M. J. Trlica

    1981-01-01

    In an attempt to describe some major relationships between soil and plant compartments in a shortgrass steppe, the process of water loss from the system and plant water relations throughout a drying cycle were studied. The water supply was manipulated and some soil and plant variables monitored throughout a drying cycle. Leaf conductance and leaf water potential of blue grama

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

    E-print Network

    Jawitz, James W.

    as well as the sciences such as Soil and Water Chemistry, Soil Physics, and Soil Microbial Ecology. Each 4231c Soil, Water, and Land Use 3 sws 4244 Wetlands 3 sws 4303c Soil Microbial Ecology 3 sws 4451 Soil Soil and Water Conservation 3 sws 4245 Water Resource Sustainability 3 sws 4307 Ecology of Waterborne

  7. Impacts of Evaporation from Saline Soils on Soil Hydraulic Properties and Water Fluxes

    NASA Astrophysics Data System (ADS)

    Fierro, V.; Hernandez, M. F.; Braud, I.; Cristi Matte, F.; Hausner, M. B.; Suarez, F. I.; Munoz, J.

    2013-12-01

    Saline soils are common in arid zones, where evaporation from shallow groundwater is generally the major component of the water balance. Thus, accurate quantification of soil water evaporation is crucial to improve water resource management in these regions. Evaporation from saline soils is a complex process that couples the movement of salts, heat, liquid water and water vapor. Precipitation/dissolution reactions can alter the soil structure and modify flow paths. The impact of evaporation from shallow groundwater on soil properties and water fluxes poses a major hydrologic challenge that remains to be answered. As a preliminary approach to consider these effects, we used the SiSPAT model (Simple Soil Plant Atmospheric Transfer) to represent the movement of liquid water and water vapor in a saline soil column subjected to two groundwater levels under nonisothermal conditions. To parameterize the model, we determined the hydraulic properties of the soil before performing the soil column experiments. When the SiSPAT model was run using uniform and constant hydraulic properties, it was unable to predict the moisture and thermal profiles, or the cumulative evaporation. This inability to reproduce the observed data is most likely due to alterations of the soil structure as a result of precipitation/dissolution reactions. When the soil hydraulic properties were allowed to vary in space, the model reproduced the experimental data successfully, suggesting that the structure of the initially homogeneous soil column was modified. It is thus necessary to incorporate salt precipitation to correctly simulate evaporation in saline soils.

  8. Simulation of Water Transport in the Soil-Plant - System.

    NASA Astrophysics Data System (ADS)

    Guo, Yimei

    1992-01-01

    The objective of this dissertation is to develop a mechanistic model of water transport in the soil-plant -atmosphere system that describes the plant's physical expression of water stress to study the effects of environmental factors, and plant hydraulic and physical properties on plant water transport. The model includes soil moisture uptake, soil heat and water transfer, evapotranspiration, and energy partitioning in the canopy and at the soil surface. The model inputs are: daily weather data (air temperature, dew point temperature, wind speed, and solar radiation); initial soil moisture and temperature profiles; plant characteristics; root density; and soil hydraulic properties. The model user may select from a number of outputs. Principal outputs include: leaf resistance, leaf temperature, soil moisture profile and evapotranspiration rate. The model describes a feedback mechanism by which transpiration controls leaf water potential, leaf water potential influences leaf resistance, and leaf resistance which, in turn, controls transpiration. The simulation runs represented the energy partitioning in the canopy and at the soil surface, and the diurnal variation of temperatures and vapor pressures of the leaf, the canopy air, and the soil surface. The relationships of leaf water potential to soil water potential, leaf resistance and transpiration were also presented. In addition, results show that root water extraction is related to the root length density profile and the soil moisture profile. The model mechanistically describes the water transport in the soil-plant-atmosphere system. The results of model validation indicated that the model is capable of simulating plant water transport under natural conditions with reasonable accuracy. Results show that the model simulates the basic features of the system including feedback processes. The sensitivity studies show that the model may be used to study plant water response to environmental factors and plant properties. The model is also useful for estimating evapotranspiration and the soil moisture profile and may provide information for irrigation and soil water management. (Abstract shortened with permission of author.).

  9. Willie Harris Address: Soil and Water Science Department

    E-print Network

    Jawitz, James W.

    1 Willie Harris Address: Soil and Water Science Department 2169 McCarty Hall University of Florida Fellow, Soil Science Society of America, 2005 UF College of Agriculture and Life Sciences (CALS) Graduate in Graduate Research, 2005 Soil and Water Science Department Outstanding Teacher/Advisor of the Year, 2003

  10. 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 ...

  11. 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.

  12. 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.

  13. Soil-Water Characteristic Curve Modeling at Low Water Content: Empirical and Semi-Empirical Approaches

    E-print Network

    Paris-Sud XI, Université de

    Soil-Water Characteristic Curve Modeling at Low Water Content: Empirical and Semi model, the Modified Kovacs (MK) model for the determination of soil-water characteristic curve at the low water contents of two horizons of a soil from Burkina Faso. Combining terms from capillary state

  14. Calibration of a water content reflectometer and soil water dynamics for an agroforestry practice

    Microsoft Academic Search

    Ranjith P. UdawattaStephen; Stephen H. Anderson; Peter P. Motavalli; Harold E. Garrett

    2011-01-01

    Water content reflectometers allow temporal and continuous assessment of spatial differences in soil water dynamics. We hypothesized\\u000a that volumetric soil water content estimated by the water content reflectometers (CS616 Campbell Sci. Inc., Logan, UT) is\\u000a influenced by clay content and temperature and therefore site- and or soil-specific equations are required for accurate estimations\\u000a of soil water. Objectives of the study

  15. 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%.

  16. Post-fire soil water repellency in highly repellent forest soils in Victoria, Australia

    Microsoft Academic Search

    Jane Cawson; Petter Nyman; Gary Sheridan; Hugh Smith

    2010-01-01

    In this study soil water repellency was monitored seasonally following prescribed burns to better understand the effects of fire severity on soil hydrological properties. The study sites consisted of dry eucalypt forest with clay loam soil. This forest type is common in south-eastern Australia and is frequently burnt by both wildfires and prescribed burns. A feature of the soil at

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

    SciTech Connect

    Li, X.; Sawatsky, N. [Alberta Environmental Centre, Vegreville, Alberta (Canada)

    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.

  18. The variation of soil temperature and water content of seasonal frozen soil with different vegetation coverage in the headwater region of the Yellow River, China

    NASA Astrophysics Data System (ADS)

    Cheng, Huiyan; Wang, Genxu; Hu, Hongchang; Wang, Yibo

    2008-06-01

    The variation and distribution of temperature and water moisture in the seasonal frozen soil is an important factor in the study of both the soil water cycle and heat balance within the source region of the Yellow River, especially under the different conditions of vegetation coverage. In this study, the impact of various degrees of vegetation coverage on soil water content and temperature was assessed. Soil moisture ( ? v) and soil temperature ( T s) were monitored on a daily basis. Measurements were made under different vegetation coverage (95, 70 80, 40 50 and 10%) and on both thawed and frozen soils. Contour charts of T s and ? v as well as a ? v T s coupling model were developed in order to account for the influence of vegetation cover and the interaction between T s and ? v. It was observed that soil water content affected both the overall range and trend in the soil temperature. The regression analysis of ? v versus T s plots indicated that the soil freezing and thawing processes were significantly affected by vegetation cover changes. Vegetation coverage changes also caused variations in the ? v T s interaction. The effect of soil water content on soil temperature during the freezing period was larger than during the thawing period. Moreover, the soil with higher vegetation coverage retained more water than that with lower coverage. In the process of freezing, the higher vegetation coverage reduced the rate of the reduction in the soil temperature because the thermal capacity of water is higher than that of soil. Areas with higher vegetation coverage also functioned better for the purpose of heat-insulating. This phenomenon may thus play an important role in the environmental protection and effective uses of frozen soil.

  19. 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.

  20. 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 ...

  1. DEVELOPING JOINT PROBABILITY DISTRIBUTIONS OF SOIL WATER RETENTION CHARACTERISTICS

    EPA Science Inventory

    A method is presented for developing probability density functions for parameters of soil moisture relationships of capillary head and hydraulic conductivity. These soil moisture parameters are required for the assessment of water flow and solute transport in unsaturated media. T...

  2. Running heading: Water retention properties of the clay in clayey soils Water retention properties of the clay in soils developed

    E-print Network

    Paris-Sud XI, Université de

    1 Running heading: Water retention properties of the clay in clayey soils Water retention properties of the clay in soils developed on clayey sediments: Significance of parent material and soil of clayey subsoils horizons according to the variation of clay characteristics. The horizons studied

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

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

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

    EPA Science Inventory

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

  5. Verification of Ground Penetrating Radar for Soil Water Content Measuring

    NASA Astrophysics Data System (ADS)

    Ermolaeva, O.; Zeiliguer, A.

    2009-04-01

    Spatially distributed water at the land surface is a vital natural resource for human being and ecosystems. Soil water content at vadose zone at regional scale controls exchange of moisture and energy between Earth surface and atmosphere, at the catchment scale - the separation of precipitation into infiltration, runoff and evapotranspiration, at the field scale - plant growing, at the small plot scale - pathway of water flow through soil profile. Hydrologist, agronomists, soil scientists and others looking for technology providing soil water content measurements across a range of spatial range. Ground penetrating radar is not destructive method of measurement for diverse application was tested in the field for mapping a spatial distribution of soil water content during infiltration event at chestnut soil of Saratov Region, Russia. A Common-MidPoint method was used to calibrate GPR OKO with a 400 MHz antenna. At experimental plot of 50x50 m a range of 36 boreholes equipped by vertical access tubes (10 distance between) for TDR PR2 with 4 predefined depths of soil moisture measurements was prepared. TDR PR2 equipment used for measurements was calibrated on special experimental setup with soil from plot. Data sets of parallel measurements of soil water content by TDR at 4 depths of borehole locations and GPR at trace lines along ranges of boreholes were used to produce soil water content maps with geo-statistical methods. Keywords: GPR, TDR, soil water content

  6. 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

  7. Surface soil water content regimes: opportunities in soil science

    Microsoft Academic Search

    Donald R. Nielsen; Miroslav Kutílek; Marc B. Parlange

    1996-01-01

    With the qualities and properties of soil not being uniformly distributed across continents, soils are classified according to their morphological features, genesis and soil-forming processes. Because properties of soils vary across the landscape, a relationship observed at one location may not be applicable for other locations. Hence, measured data and deduced relationships are location specific and should be interpreted with

  8. 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.

  9. CCA Training : Soil and Water Management

    E-print Network

    Balser, Teri C.

    clay sand Clay Sand Silt #12;Textural properties of mineral soils Soil class Properties of moist soil Physical Properties: Texture · Relative proportion of sand, silt, and clay that lends a distinct feel to the soil ­Relative size difference ­Clay particles have greatest effect on soil management ­Heavy soil

  10. Isotopic tracers for water and solute movement in desert soils

    SciTech Connect

    Phillips, F.M. [New Mexico Inst. of Mining and Technology, Socorro (United States)

    1993-06-01

    Most soil-physics investigations focus on agricultural soils and as a result the physics of soil-water processes in desert soils are comparatively poorly understood. Long-term tracer experiments provide valuable information. Among the most useful environmental tracers, from atmospheric nuclear weapons testing, are tritium and chlorine-36. Conclusions of studies of these tracers include the following: thermal vapor diffusions is important in water movement in desert soils; upward refluxing of the liquid phase during the summer separates volatile from non-volatile components; net infiltration rates over 30 years are a few millimeters or less in all soils investigated. 4 refs. 2 figs.

  11. 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.

  12. 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...

  13. 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.

  14. Leaf water potential in Pinus taeda L. as related to fluctuating soil water and atmospheric conditions 

    E-print Network

    Ellison, Stanley Lee

    1969-01-01

    is determined by plant factors such as stomatal control and by various atmospheric factors, e. g. , vapor pressure deficit of the atmosphere, temperature, and wind which affect the steepness of the vapor pressure gradient from leaf to atmosphere (Hodges 1967...). Water absorption is controlled by the rate of water loss, the extent and efficiency of the plant's root system, and soil factors such as soil structure, soil water content, and soil water tensior. (Kramer 1963). All plants are sub]ected to some...

  15. Distribution of soil and leaf water potentials of mature grapefruit trees under three soil moisture regimes

    E-print Network

    Prathapar, Sanmugam Ahembaranathan

    1982-01-01

    DISTRIBUTION OF SOIL AND LEAF WATER POTENTIALS OF MATURE GRAPEFRUIT TREES UNDER THREE SOIL MOISTURE REGIMES A Thesis by SANMUGAM AHEMBARANATHAN PRATHAPAP, Submitted to the Graduate College of Texas A&M University in partial fulfillment... of the requirement for the degree of MASTER OF SCIENCE May 1982 Major Subject; Agricultural Engineering DISTRIBUTION OF SOIL AND LEAF WATER POTENTIALS OF MATURE GRAPEFRUIT TREES UNDER THREE SOIL MOISTURE REGIMES A Thesis by SANMUGAM AHEMBARANATHAN PRATHAPAR...

  16. Effect of antecedent soil-water content on aggregate stability and erodibility of a loess soil

    NASA Astrophysics Data System (ADS)

    Vermang, J.; Demeyer, V.; Cornelis, W. M.; Gabriels, D.

    2009-04-01

    Soil erosion processes are affected by the erodibility of the soil and by the erosivity of the rain. Aggregate stability is commonly considered as the most significant soil physical property that determines soil erodibility. Both aggregate stability and soil erodibility are commonly considered to be constant properties, without taking into account the influence of time-dependent parameters, such as antecedent soil-water content (?), being the soil-water content prior to the rainfall. The effects of rain characteristics and invariant soil properties such as texture and organic matter content on soil erosion processes are well documented. However, the effect of antecedent soil-water content on aggregate breakdown, seal formation and subsequent soil erosion is much more disputable as opposing effects have been reported. The objectives were to determine the effect of ? on aggregate stability, seal formation, runoff and soil loss. Lab experiments were conducted on a Belgian silt loam soil. Air-dried soil aggregates were subjected to antecedent soil-water contents of 0.04 (air-dry aggregates), 0.12 and 0.19 m3 m-3. Aggregate stability was determined according to the 'dry and wet sieving' method of De Leenheer and De Boodt (1959). The method starts from fixed aggregate fractions obtained from dry sieving which subsequently are prewetted and undergo a wet sieving. Runoff and soil loss was determined by means of a laboratory rainfall simulator, consisting of a rotating circular water tank, which is located at 3.20 m height and which is supplied with 90 glass capillaries serving as drop formers. A positive relationship between antecedent soil-water content and aggregate stability was found. This can be attributed to a decrease in slaking forces. On the soils with highest antecedent soil-water content an increase in aggregate stability due to prewetting prevented aggregate breakdown. As such, no seal was formed and no runoff occurred. The highest total runoff values were observed for the intermediate ?, while intermediate amounts of total runoff were noticed for the air-dry aggregates. Soil loss, however, showed a different trend: highest values were found for the lowest ?, intermediate values for the intermediate ? and no soil loss for the highest ?. We further observed that ? had no influence on the final runoff rates and on the final infiltration rate through the soil surface. In using a water discharge and stream power equation to predict sediment transport, we found a decreasing erodibility with increasing ?. We therefore suggest including ? as an additional variable to assess soil erodibility in deterministic event-based water erosion models.

  17. 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 ...

  18. Responses of amphibian populations to water and soil factors in experimentally-treated aquatic macrocosms

    USGS Publications Warehouse

    Sparling, D.W.; Lowe, T.P.; Day, D.; Dolan, K.

    1995-01-01

    Survival of anuran embryos and tadpoles is reduced in acidic (pH < 5.0) waters under laboratory conditions. However, field data on the presence-absence of amphibian species and acidity are equivocal. This study attempts to reconcile some of this discrepancy by using macrocosms to examine the interaction of soil type and water acidification on free-ranging tadpole populations. Tadpoles were caught with activity traps in 24 aquatic macrocosms experimentally treated with H2SO4 and Al2(SO4)3 and lined with either comparatively high metal, Iow organic matter clay soils or lower metal, higher organic matter loams. Northern cricket frog (Acris crepitans) tadpole abundance was less in acidified macrocosms than in circumneutral ones (p < 0.05) and less in those with loam soils than in macrocosms with clay soils (p < 0.04). Gray treefrog (Hyla versicolor) abundance was affected by an interaction between soil and acidification (p < 0.07) in that treatment effects were only observed in macrocosms with clay soils (p < 0.01). No differences were observed among treatments for green frog (Rana clamitans) or southern leopard frog (R. utricularia) tadpoles. The study shows that soil type may interact with water conditions to affect amphibian populations in acidified waters

  19. Role of Soil Texture on Mesquite Water Relations and Response to Summer Precipitation

    Microsoft Academic Search

    Alessandra Fravolini; Kevin R. Hultine; Dan F. Koepke; David G. Williams

    In the arid Southwest United States, monsoon precipitation plays a key role in ecosystem water balance and productivity. The sensitivity of deeply rooted plants to pulses of summer precipitation is, in part, controlled by the interaction between soil texture, precipitation intensity, and plant rooting depth and activity. In this study we evaluated the water relations of a leguminous tree species

  20. Mucilage exudation facilitates root water uptake in dry soils

    NASA Astrophysics Data System (ADS)

    Ahmed, M. A.; Carminati, A.; Kroener, E.; Holz, M.; Zarebanadkouki, M.

    2014-12-01

    As plant roots take up water and the soil dries, water depletion is expected to occur in the rhizosphere. However, recent experiments showed that the rhizosphere was wetter than the bulk soil during root water uptake. We hypothesise that the increased water content in the rhizosphere was caused by mucilage exuded by roots. It is probably that the higher water content in the rhizosphere results in higher hydraulic conductivity of the root-soil interface. In this case, mucilage exudation would favour the uptake of water in dry soils. To test this hypothesis, we covered a suction cup, referred to as an artificial root, with mucilage. We placed it in soil with a water content of 0.03 cm3 cm-3, and used the root pressure probe technique to measure the hydraulic conductivity of the root-soil continuum. The results were compared with measurements with roots not covered with mucilage. The root pressure relaxation curves were fitted with a model of root water uptake including rhizosphere dynamics. The results demonstrated that when mucilage is added to the root surface, it keeps the soil near the roots wet and hydraulically well conductive, facilitating the water flow from dry soils towards the root surface. Mucilage exudation seems to be an optimal plant trait that favours the capture of water when water is scarce.

  1. 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

  2. Water and temperature relations of soil Actinobacteria.

    PubMed

    Stevenson, Andrew; Hallsworth, John E

    2014-12-01

    Actinobacteria perform essential functions within soils, and are dependent on available water to do so. We determined the water-activity (aw ) limits for cell division of Streptomyces albidoflavus, Streptomyces rectiviolaceus, Micromonospora grisea and Micromonospora (JCM 3050) over a range of temperatures, using culture media supplemented with a biologically permissive solute (glycerol). Each species grew optimally at 0.998 aw (control; no added glycerol) and growth rates were near-optimal in the range 0.971-0.974 (1?M glycerol) at permissive temperatures. Each was capable of cell division at 0.916-0.924 aw (2?M glycerol), but only S.?albidoflavus grew at 0.895 or 0.897 aw (3?M glycerol, at 30 and 37°C respectively). For S.?albidoflavus, however, no growth occurred on media at ??0.870 (4?M glycerol) during the 40-day assessment period, regardless of temperature, and a theoretical limit of 0.877 aw was derived by extrapolation of growth curves. This level of solute tolerance is high for non-halophilic bacteria, but is consistent with reported limits for the growth and metabolic activities of soil microbes. The limit, within the range 0.895-0.870 aw , is very much inferior to those for obligately halophilic bacteria and extremely halophilic or xerophilic fungi, and is inconsistent with earlier reports of cell division at 0.500 aw . These findings are discussed in relation to planetary protection policy for space exploration and the microbiology of arid soils. PMID:25132485

  3. 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.

  4. 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.

  5. Modeling soil carbon transported by water erosion processes

    Microsoft Academic Search

    G. C. Starr; R. Lal; R. Malone; D. Hothem; L. Owens; J. Kimble

    2000-01-01

    Long-term monitoring is needed for direct assessment of soil organic carbon (SOC), soil, and nutrient loss by water erosion on a watershed scale. However, labor and capital requirements preclude implementation of such monitoring at many locations representing principal soils and ecoregions. These considerations warrant the development of diagnostic models to assess erosional SOC loss from more readily obtained data. The

  6. 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,…

  7. Water-soluble organic matter in forest soils

    Microsoft Academic Search

    A. T. Kuiters; W. Mulder

    1993-01-01

    Soil culture experiments were conducted to examine the effects of water-soluble organic matter (WSOM), isolated from the Ah horizon of a forest soil on cation uptake by seedlings of Agrostis capillaris and Silene dioica. In contrast to the large effects on soil equilibria, cation uptake was only slightly affected by WSOM. Solubilized Al, Fe, Cu and Pb, were not found

  8. 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...

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    Knowledge of soil thermal (heat) properties is essential when assessing heat transport in soils. Heat regime in soils associates with many other soil processes (like water evaporation and diffusion, plant transpiration, contaminants behavior etc.). Thermal properties are needed when assessing affectivity of energy gathering from soil profiles using horizontal ground heat exchangers, which is a main goal of this study. Study is focused on measuring of thermal properties (heat capacity and heat conductivity) in representative soils of the Czech Republic. Measurements were performed on soil samples taken from the surface horizons of 11 representative soil types and from 2 soil substrates (sand and loess). The measured relationships between the heat conductivity and volumetric soil-water content were described by non-linear equations (Chung and Horton, 1987). The measured relationships between the heat capacity and volumetric soil-water content were expressed using the linear equations. The greatest values of the heat conductivity were measured in sandy soils (sandy and gravely sand substrates). The average values were obtained in soils on loess substrates. Lower values were obtained for all Cambisols (variable substrates). The lowest values were measured in Stagnic Chernozem Siltic on marlite. Opposite trend was observed for the maximal heat capacity, which was mostly impacted by water content. A soil water and heat regime within the soil profile was monitored at one location. In addition the impact of various soil cover at the soil top on soil water content and temperature was measured. Soil hydraulic properties were measured using the multistep-outflow technique. The saturated hydraulic conductivities were also measured using the Guelph permeameter. Programs HYDRUS-1D and 2D/3D were used for a mathematical interpretation of the observed soil water and heat regime. Acknowledgment: Authors acknowledge the financial support of the Technology Agency of the Czech Republic (TA02020991). Work was also partly supported by the Ministry of Agriculture of the Czech Republic (QJ1230319). Literature Chung, S.O., Horton, R. 1987. Soil heat and water flow with a partial surface mulch, Water Resour. Res., 23(12), 2175-2186, 1987.

  10. 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.

  11. 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.

  12. Critical water contents of hydrophobic soils in New Zealand

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    Soil water repellency is an important problem for pasture farming in New Zealand which causes low infiltration rates and increased surface runoff. However, the real extent of this issue is not yet evaluated. Water repellency is thought to appear on dry soils, when the water content falls below a critical limit. The main objectives of this study was 1) to investigate the effects of different amounts of infiltration water on hydrophobicity of three selected soils under grassland in the North island of New Zealand, and 2) to determine the critical water content for ten sites with five different soil types. In April 2011 undisturbed and disturbed soil samples from a brown, gley and organic soil have been taken from sites around Mount Taranaki. Soil water repellency was determined using the Water Droplet Penetration Time Test (WDPT) and the Molarity of Ethanol Droplet Test (MED). During the lab experiment four amounts of water were applied to the 270 cm³ samples: 400, 800, 1600 and 2400 mL . One test was performed with cold and one with hot (80 °C) water. Each test was replicated four times. In the leachate the amount of dissolved organic carbon was analyzed. The experiments showed that only for the brown soil water repellency decreased significantly with increasing amount of infiltration water whereas for gley soils no correlation was found. Gley soil had initially a lower degree of hydrophobicity compared to the other soils. Possibly due to the higher bulk density of these soils, the carbon compounds directly surrounding the soil particles wre rearranged rather than leached. No clear pattern could be obtained for organic soils. This may be explained by the high initial carbon content of more than 20%. It may take a much greater amount of infiltration to affect hydrophobicity. The critical contact angle of investigated soils above which water repellency is moderately persistent, was 93.8°. In May 2012 ten more sites were sampled and five soil types were investigated with respect to the critical water content. Soil hydrophobicity was again tested during 4 wetting and drying cycles on 3 replicates each of disturbed and undisturbed soil samples. The tests confirmed that water repellency does not exist at high water contents. It generally starts to appear at a certain limit, increases rapidly up to a peak value and finally decreases slowly when the water content approaches 0. Critical water contents were very high in the first wetting cycle and stabilized at a rather constant level during the 2nd, 3rd and 4th wetting cycle. This phenomenon may be due to inhomogeneous water distributions within the field moist soil samples in the 1st wetting cycle and it was thus chosen to take the critical moisture content from the 2nd wetting cycle for further purposes. We found relatively broad transition zones where soils were found to be both hydrophilic and hydrophobic. Critical water contents or rather transition zones were found to differ significantly between the various soil orders and showed values between 0.34 (m³/m³) for recent soil and 0.44(m³/m³) for organic soil.

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

    NASA Astrophysics Data System (ADS)

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

    2008-12-01

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

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

    EPA Science Inventory

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

  15. Analysis of soil and water for TATB content

    SciTech Connect

    Schaffer, C.L.

    1992-11-01

    A reverse-phase liquid chromatography (HPLC) method was developed for the analysis of TATB in soil samples. The soil samples were extracted with dimethylformamide (DMF). The extract was analyzed to determine the TATB content in the soil. The detection limit using this procedure was 2 parts/million (ppm) for TATB in the soil. An organic free sample of water was saturated with TATB. The water was filtered through a 0.2-{mu} filter, then injected into both a reverse-phase and normal-phase liquid chromatograph system. No peaks were detected. Therefore, the solubility of TATB in water is less than the detection limits of the chromatograph methods.

  16. The Initial Water Content Dependent Swelling Behavior of Clayey Soils

    NASA Astrophysics Data System (ADS)

    Samet Öngen, Ali; Abiddin Erguler, Zeynal

    2015-04-01

    The variation in water content is known as a main controlling parameter for many physical and mechanical behaviors of clayey soils, particularly soils found in arid and semi-arid regions. Expansive soils found in such regions are naturally subjected to many volume increase and decrease cycles within unsaturated zone during rainy and dry periods, and thus these soils constitute severe hazard to low-rise light buildings and infrastructures constructed in shallow unsaturated depths. Although the relationships between swelling parameters (swelling pressure and swelling percent) and soils' physical - index properties have been investigated in details in previous researches, the continuous effect of water content on swelling mechanisms of soils is not yet sufficiently studied. The water content of unsaturated zone naturally fluctuates with changes in both seasonal climatic conditions and increasing in depths, and therefore, swelling parameters of a soil within unsaturated soils should not be represented with only one single value. For achieving accurate understanding of swelling behavior at field condition, soils should be subjected to swelling tests by considering different initial water content conditions. Considering requirement for further understanding in water content dependent swelling behavior of soils, a research program was aimed to investigate the effect of initial water content on swelling behavior of soil materials. For this purpose, soils having wide range of physical properties such as grain size distributions, mineralogical composition and consistency limits were collected from different locations in Turkey. To minimize the effect of dry unit weight on swelling behavior of soils, samples prepared at same dry unit weight (14.6 kN/m3) with various initial water contents ranging from 0% to approximately 37% were subjected to swelling tests by using convenient odometer device. Beside these tests, grain size distribution, Atterberg limits and mineralogical composition of samples were also determined. The swelling pressure of selected samples reached up to 250 kPa at zero water content. In addition, swelling parameters of collected clayey soils considerably decrease with increasing initial water content to somewhere between 30% and 37%. For finding the most important physical, index and mineralogical properties to constitute predictive models for swelling parameters of soils and understand the effect of initial water content, simple and multiple regression analyses were performed among appropriate variables. As a result of all analyses, statistically significant linear relationships were obtained between swelling parameters and initial water content values. Furthermore, it can be concluded that initial water content is a crucial controlling parameter for understanding swelling behavior of soils.

  17. Soil water fluctuations: microbial community responses and CO2 production

    NASA Astrophysics Data System (ADS)

    Placella, S.; Brodie, E. L.; Firestone, M. K.; Lennon, J. T.

    2012-12-01

    Water availability is one of the primary controllers of microbial activity in soils. Likely even more important to microbial activity than static values of soil water potential are changes in soil water potential; changes in soil water potential may trigger pulses of or cross thresholds for microbial activity. How do increases and declines in soil water potential affect microbial activity and rates of carbon dioxide (CO2) production from soil? While extremely dry soils have very low rates of CO2 production, wetting of dry soil is known to initiate a large CO2 pulse known as the Birch effect. We studied this pulse in two California annual grassland soils while concurrently monitoring microbial resuscitation. We also examined the impacts of reduced rainfall in a successional grassland in Michigan, with a focus on changes in microbial activity during a dry down period. In both systems we used relative RNA quantity to identify when different microorganisms were relatively more active. Upon wetting of dry soil, we found that the large CO2 pulse occurred during the resuscitation of the microbial community. We identified three resuscitation strategies (rapid, intermediate and delayed responders) and found that they are phylogenetically conserved, with related organisms displaying the same strategy. During a soil dry down event, we found a decline in the rate of CO2 production from soils and examined the concurrent change in the microbial community during this 7-day period. We also investigated how a summer of greater water potential fluctuation, due to reduced rainfall, impacted the stability of the microbial community. Our results demonstrate that changes in water potential can drive changes in microbial activity, leading to serious implications for soil CO2 production.

  18. Correction of TDR-based soil water content measurements in conductive soils

    Microsoft Academic Search

    Marco Bittelli; Fiorenzo Salvatorelli; Paola Rossi Pisa

    2008-01-01

    Time Domain Reflectometry (TDR) is a widespread technique for measurement of soil water content (SWC). The main assumption behind the use of Time Domain Reflectometry (TDR) is of negligible losses, therefore assuming that only the real part determines the value of the TDR-measured apparent dielectric permittivity. This assumption does not hold for soils where surfaces are conductive (clay soils) or

  19. Soil-water and soil physical properties under contour hedgerow systems on sloping oxisols

    Microsoft Academic Search

    F. Agus; D. K. Cassel; D. P. Garrity

    1997-01-01

    Hedgerows planted along the contour on steep lands in the humid tropics reduce soil erosion and build terraces over time. The objectives of this study in two Hapludoxes in the Philippines were to evaluate changes after 4 years in soil properties and soil water relations on transects perpendicular to the cropped alleys between four grass and tree hedgerow systems and

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    The understanding of soil-vegetation-atmosphere interactions is of utmost importance in the solution of a number of hydrological questions and practical issues, including flood control, agricultural best practice, slope stability and impacts of climatic changes. Geophysical time-lapse monitoring can greatly contribute to the understanding of these interactions particularly for its capability to map in space and time the effects of vegetation on soil moisture content. In this work we present the results of two case studies showing the potential of hydro-geophysics in this context. The first example refers to the long term monitoring of the soil static and dynamic characteristics in an experimental site located in Sardinia (Italy). The main objective of this study is to understand the effects of soil - water - plants interactions on soil water balance. A combination of time-lapse electromagnetic induction (EMI) monitoring over wide areas and localized irrigation tests monitored by electrical resistivity tomography (ERT) and TDR soil moisture measurements is here used, in order to achieve quantitative field-scale estimates of moisture content from topsoil layer. Natural gamma-ray emission mapping, texture analysis and laboratory calibration of an electrical constitutive relationship on soil samples complete the dataset. We therefore observed that the growth of vegetation, with the associated below ground allocation of biomass, has a significant impact on the soil moisture dynamics. In particular vegetation extracts a large amount of water from the soil in the hot season, but it also reduces evaporation by shadowing the soil surface. In addition, vegetation enhances the soil wetting process as the root system facilitates water infiltration, thus creating a positive feedback system. The second example regards the time-lapse monitoring of soil moisture content in an apple orchard located in the Alpine region of Northern Italy (Trento). A three-dimensional cross-hole ERT setup was created using four small-scale boreholes and a 2D array of surface electrodes. The soil response to irrigation and evapo-transpiration evidences the location of tree roots, including the influence of irrigation patterns on the root growth, and their efficiency at removing soil moisture.

  2. 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.

  3. Use of limited soil property data and modeling to estimate root zone soil water content

    NASA Astrophysics Data System (ADS)

    Starks, Patrick J.; Heathman, Gary C.; Ahuja, Lajpat R.; Ma, Liwang

    2003-03-01

    Estimation of soil water content in the root zone with time in different parts of a watershed is important for both strategic and tactical management of water resources, as well as of agricultural production, water quality, and soil resources. This estimation requires detailed knowledge of rainfall intensities and meteorological variables over space and time, as well as the physical and hydraulic properties of the soil horizons and plant growth information. However, all this detailed spatial information is extremely expensive and time consuming to obtain. New technologies are helping to increase the spatial sampling of rainfall and other meteorological variables, but spatially detailed measurement of soil properties is still not practical. The best we can obtain from the existing soil survey database is the spatial distribution of soil textural class. We investigated the use of a hierarchy of limited soil input data, ranging from soil textural class of soil horizons alone, to measured soil texture and bulk densities of horizons, additional lab or field measurement of -33 kPa soil water content, to additional field measurement of average saturated hydraulic conductivity. These five modeling scenarios, along with meteorological and plant information, were input to the Root Zone Water Quality Model (RZWQM) to estimate 0-60 cm soil water content over a 30-day period in 1997 at the Little Washita River Experimental Watershed in Oklahoma. The estimated water contents were compared with time-domain reflectometry (TDR) profile measurements and gravimetric samplings of soil surface moisture. In addition to the five scenarios using limited input data, a more detailed set of data based on laboratory measured soil water retention curves and field measured saturated conductivity was supplied to the model for all Brooks-Corey function parameters (full description mode). Estimates of root zone soil water content using detailed input were compared to estimates obtained using minimum input data. Adjustments in specific hydraulic parameters were also made in an effort to calibrate the model to the soils in this region. Overall, reasonable agreement was found between TDR-measured and RZWQM-predicted average water contents for 0-60 cm depths. Surprisingly, the smallest errors in the predicted water contents were achieved using either the textural class only or the hydraulic properties determined in situ, with root mean square errors ranging from 0.012 to 0.018 m 3 m -3. Hence, the model provided adequate estimates of average profile soil water content based on textural class-name only which was considered the most limited input data condition.

  4. TILLAGE EFFECTS ON NEAR SURFACE SOIL WATER DYNAMICS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Tillage modifies the soil physical properties near the surface which in turn can influence evaporation rates and how water is redistributed within the profile during and after precipitation. The objective of this study was to evaluate the effects of sweep tillage on near surface soil water dynamics....

  5. Agricultural Grassland, Soil and Water Research Laboratory, Temple, TX

    E-print Network

    Agricultural Research Service Grassland, Soil and Water Research Laboratory, Temple, TX Monitoring, Modeling and Decision-Making Daren Harmel USDA-ARS, Temple, TX #12;Agricultural Research Service Grassland monitoring, modeling, and decision- making #12;Agricultural Research Service Grassland, Soil and Water

  6. 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...

  7. 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 ...

  8. Water and heat fluxes in desert soils: 1. Field studies

    Microsoft Academic Search

    Bridget R. Scanlon

    1994-01-01

    Soil physics parameters were monitored in a semiarid site in the Chihuahuan Desert of Texas to evaluate unsaturated flow processes under natural conditions. The bed of an ephemeral stream was instrumented with neutron probe access tubes to monitor water content for 3 years and with thermocouple psychrometers to monitor water potential and temperature for 2 years. Soil samples were collected

  9. Water and heat fluxes in desert soils 1. Field studies

    Microsoft Academic Search

    Bridget R. Scanlon

    1994-01-01

    Soil physics parameters were monitored in a semiarid site in the Chihuahuan Desert of Texas to evaluate unsaturated flow processes under natural conditions. The bed of an ephemeral stream was instrumented with neutron probe access tubes to monitor water content for 3 years and with thermocouple psychrometers to monitor water potential and temperature for 2 years. Soil samples were collected

  10. Ground-based measurements of soil water storage in Texas

    E-print Network

    Yang, Zong-Liang

    :956-963 SAND Soil Water Storage (NLDAS) #12;Sensor Technologies and Scale Spatial Support LSM operate at >km2Ground-based measurements of soil water storage in Texas Todd Caldwell Bridget Scanlon Di Long it? How do we modeling it? How can we measure it? · Current technologies · What's in Texas What

  11. Soil Water Use by Ceanothus velutinus and Two Grasses

    Microsoft Academic Search

    W. Lopushinsky; G. O. Klock

    Seasonal trends of soil water content in plots of snowbrush (Ceanothus velutinus Dougl.), orchard grass (Dactylis glomerata L), and pinegrass {Calamagrostis rubes- cens Buckl.) and in bare plots were measured on a burned-over forest watershed in north-central Washington. A comparison of soil water contents at depths of 12, 24, 36, and 48 inches indicated that the grasses and snowbrush generally

  12. 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.

  13. Effects of water addition on soil arthropods and soil characteristics in a precipitation-limited environment

    NASA Astrophysics Data System (ADS)

    Chikoski, Jennifer M.; Ferguson, Steven H.; Meyer, Lense

    2006-09-01

    We investigated the effect of water addition and season on soil arthropod abundance and soil characteristics (%C, %N, C:N, moisture, pH). The experimental design consisted of 24 groups of five boxes distributed within a small aspen stand in Saskatchewan, Canada. The boxes depressed the soil to create a habitat with suitable microclimate for soil arthropods, and by overturning boxes we counted soil arthropods during weekly surveys from April to September 1999. Soil samples were collected at two-month intervals and water was added once per week to half of the plots. Of the eleven recognizable taxonomic units identified, only mites (Acari) and springtails (Collembola) responded to water addition by increasing abundance, whereas ants decreased in abundance with water addition. During summer, springtail numbers increased with water addition, whereas pH was a stronger determinant of mite abundance. In autumn, springtails were positively correlated with water and negatively correlated with mites, whereas mite abundance was negatively correlated with increasing C:N ratio, positively correlated to water addition, and negatively correlated with springtail abundance. Although both mite and springtail numbers decreased in autumn with a decrease in soil moisture, mites became more abundant than springtails suggesting a predator-prey (mite-springtail) relationship. Water had a significant effect on both springtails and mites in summer and autumn supporting the assertion that prairie soil communities are water limited.

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

    SciTech Connect

    Morris, R.C.; Fraley, L. Jr. [Colorado State Univ., Fort Collins, CO (United States)

    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.

  15. 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

  16. Evaluating DEM results with FEM perspectives of load : soil interaction

    Microsoft Academic Search

    D. Tadesse

    2004-01-01

    Keywords<\\/span><\\/strong>: Load - soil interaction, soil structure, soil mechanical properties, FEM (Finite Element Method), Plaxis (Finite Element Code), granular particles, shear stress, DEM (Distinct Element Method), micromechanics of deformation, interparticle friction coefficient<\\/o:p><\\/span><\\/div>«

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  1. 26 CFR 1.175-2 - Definition of soil and water conservation expenditures.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...false Definition of soil and water conservation expenditures. 1.175-2...175-2 Definition of soil and water conservation expenditures. (a) Expenditures...for the purpose of soil or water conservation in respect of...

  2. 26 CFR 1.175-1 - Soil and water conservation expenditures; in general.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ...2011-04-01 false Soil and water conservation expenditures; in general... § 1.175-1 Soil and water conservation expenditures; in general...farmer may deduct his soil or water conservation expenditures which...

  3. 26 CFR 1.175-1 - Soil and water conservation expenditures; in general.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...2012-04-01 false Soil and water conservation expenditures; in general... § 1.175-1 Soil and water conservation expenditures; in general...farmer may deduct his soil or water conservation expenditures which...

  4. 26 CFR 1.175-1 - Soil and water conservation expenditures; in general.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ...2014-04-01 false Soil and water conservation expenditures; in general... § 1.175-1 Soil and water conservation expenditures; in general...farmer may deduct his soil or water conservation expenditures which...

  5. 26 CFR 1.175-2 - Definition of soil and water conservation expenditures.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...false Definition of soil and water conservation expenditures. 1.175-2...175-2 Definition of soil and water conservation expenditures. (a) Expenditures...for the purpose of soil or water conservation in respect of...

  6. 26 CFR 1.175-2 - Definition of soil and water conservation expenditures.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...false Definition of soil and water conservation expenditures. 1.175-2...175-2 Definition of soil and water conservation expenditures. (a) Expenditures...for the purpose of soil or water conservation in respect of...

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

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ...2013-04-01 false Soil and water conservation expenditures; in general... § 1.175-1 Soil and water conservation expenditures; in general...farmer may deduct his soil or water conservation expenditures which...

  8. 26 CFR 1.175-1 - Soil and water conservation expenditures; in general.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ...2010-04-01 false Soil and water conservation expenditures; in general... § 1.175-1 Soil and water conservation expenditures; in general...farmer may deduct his soil or water conservation expenditures which...

  9. 26 CFR 1.175-2 - Definition of soil and water conservation expenditures.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ...false Definition of soil and water conservation expenditures. 1.175-2...175-2 Definition of soil and water conservation expenditures. (a) Expenditures...for the purpose of soil or water conservation in respect of...

  10. Mutual interaction of soil moisture state and atmospheric processes

    Microsoft Academic Search

    Dara Entekhabi; Ignacio Rodriguez-Iturbe; Fabio Castelli

    1996-01-01

    The purpose of this paper is to outline the pathways through which soil moisture and meteorological phenomena mutually influence one another at local, regional and global scales. This constitutes two-way land-atmosphere interaction, as meteorological phenomena both act as the forcing and react to the forcing by the soil moisture state. Land surface modification of the atmospheric environment and the atmospheric

  11. 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

  12. 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...

  13. 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...

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

    SciTech Connect

    Schaetzl, R.J. (Michigan State Univ., East Lansing (United States)); Kirsch, S.W. (Memphis State Univ., TN (United States)); 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.

  15. Centrifuge modelling of lateral pipeline/soil interaction -- Phase 2

    SciTech Connect

    Paulin, M.J.; Phillips, R. [Memorial Univ. of Newfoundland, St. John`s, Newfoundland (Canada). Centre for Cold Ocean Resources Engineering; Boivin, R. [NOVA Corp., Calgary, Alberta (Canada). NOVA Gas Transmission Limited Division

    1995-12-31

    An ongoing research program is investigating the load transfer behavior of buried pipelines subjected to lateral soil movement in cohesive soil. Phase 1 of this study, reported to OMAE `92, demonstrated that the centrifuge technique was appropriate for this application in determining the interaction conditions for the lateral loading of pipelines. Limited control of the shear strength masked geometric effects (trench width and burial depth) on the interaction factors and desiccation affected the interpretation of some of the interaction factors. The Phase 2 study investigated the geometric effects of pipeline soil cover, ditch width and also displacement rate. The study included a ``modelling of models`` test to verify the reliability of the centrifuge modelling technique. This paper addresses two issues: (1) The Phase 1 soil strength profiles and interaction factors were reanalyzed based on an improved understanding of the soil conditions at the time of testing; (2) A selection of the Phase 2 results are presented for a 0.95m diameter pipeline subjected to lateral soil movement. The program results are discussed and compared with current pipeline/soil interaction analysis methods.

  16. 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

    -termbeneficial agricultural utilisation of sewage sludge concerning heavy metal contamination risk and the cultivation://www.wrc.org.za Plant-soil interactions of sludge-borne heavy metals and the effect on maize (Zea mays L.) seedling under South African conditions and the conservative nature of the heavy metal guidelines, when

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

    NASA Astrophysics Data System (ADS)

    Lamorski, Krzysztof; S?awi?ski, Cezary; Barna, Gyöngyi

    2014-05-01

    There are some important macroscopic properties of the soil porous media such as: saturated permeability and water retention characteristics. These soil characteristics are very important as they determine soil transport processes and are commonly used as a parameters of general models of soil transport processes used extensively for scientific developments and engineering practise. These characteristics are usually measured or estimated using some statistical or phenomenological modelling, i.e. pedotransfer functions. On the physical basis, saturated soil permeability arises from physical transport processes occurring at the pore level. Current progress in modelling techniques, computational methods and X-ray micro-tomographic technology gives opportunity to use direct methods of physical modelling for pore level transport processes. Physically valid description of transport processes at micro-scale based on Navier-Stokes type modelling approach gives chance to recover macroscopic porous medium characteristics from micro-flow modelling. Water microflow transport processes occurring at the pore level are dependent on the microstructure of porous body and interactions between the fluid and the medium. In case of soils, i.e. the medium there exist relatively big pores in which water can move easily but also finer pores are present in which water transport processes are dominated by strong interactions between the medium and the fluid - full physical description of these phenomena is a challenge. Ten samples of different soils were scanned using X-ray computational microtomograph. The diameter of samples was 5 mm. The voxel resolution of CT scan was 2.5 µm. Resulting 3D soil samples images were used for reconstruction of the pore space for further modelling. 3D image threshholding was made to determine the soil grain surface. This surface was triangulated and used for computational mesh construction for the pore space. Numerical modelling of water flow through the sample was performed. Steady-state Navier-Stokes equations for incompressible laminar flows were used for that purpose. Resulting from modelling values of the soil saturated permeabilities were compared with results from measurements, made using constant head permeameter. Differences in this results were discussed. The study was partially funded from the National Science Centre (Poland) upon the contract: UMO-2011/01/B/ST10/07544.

  18. 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.

  19. 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.

  20. 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.

  1. Parameter identification for planetary soil based on a decoupled analytical wheel-soil interaction terramechanics model

    Microsoft Academic Search

    Liang Ding; Kazuya Yoshida; Keiji Nagatani; Haibo Gao; Zongquan Deng

    2009-01-01

    Identifying planetary soil parameters is not only an important scientific goal, but also necessary for exploration rover to optimize its control strategy and realize high-fidelity simulation. An improved wheel-soil interaction mechanics model is introduced, and it is then simplified by linearizing the normal stress and shearing stress to derive closed-form analytical equations. Eight unknown soil parameters are divided into three

  2. 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

  3. An experimental investigation into lateral pipeline/soil interaction

    SciTech Connect

    Paulin, M.J.; Phillips, R. [Memorial Univ. of Newfoundland, St. John`s, Newfoundland (Canada). Centre for Cold Ocean Resources Engineering; Boivin, R. [Nova Gas Transmission Ltd., Calgary, Alberta (Canada)

    1996-12-01

    In 1991, Nova Gas Transmission Limited began an experimental research program using centrifuge modeling to study the load transfer behavior of buried pipelines subjected to lateral soil movement. Phase 2 of this research program continued to examine laterally displacing pipeline/soil interaction. The six main objectives of this phase were to investigate: (1) the effect of pipeline soil cover; (2) the effect of ditch width; (3) the effect of interaction rate; (4) a modeling of models to verify the centrifuge modeling technique; (5) the effect of preconsolidation stress of the soil; and (6) the effect of different backfills. The data and preliminary analysis of objectives 1--4 were presented at OMAE `95. This paper addresses two issues: (1) the authors present new experimental test results obtained since the last OMAE meeting for a prototype pipeline (0.95m diameter) subjected to lateral soil movement under a 0.8m pipeline cover depth. These test results were obtained for interaction rates ranging from approximately 0.35 to 275m/year, in soil subjected to one dimensional preconsolidation stresses of 160 and 400 kPa, and for pipelines with a variety of backfills; (2) the authors discuss the phase 2 results through comparison with current pipeline/soil interaction analysis methods, through comparison with conventional geotechnical analysis results, and through observed trends in the data.

  4. Measurements and modeling of soil water distribution around landmines in natural soil

    NASA Astrophysics Data System (ADS)

    Lensen, Henk A.; Schwering, Piet B. W.; Rodriguez Marin, Garciela; Hendrickx, Jan M. H.

    2001-10-01

    Soil water content, dielectric constant, electrical conductivity, thermal conductivity and heat capacity affect the performance of many sensors and therefore the detection of landmines. The most important of these is water content since it directly influences the other properties. We measure soil water distribution around an antitank and an antipersonnel mine buried in a sand soil under varying moisture levels. After a period of two days with 38 mm precipitation the water content below the AP-mine increased from 0.07 to 0.12. The water content above and below the AT- mine increased from 0.09 to 0.17 and 0.09 to 0.13, respectively. Below the AT-mine it was 0.02 to 0.04 dryer than above the mine. The dielectric constant of the soil was estimated from the soil water content. After a dry period of two weeks the dielectric contrast between the AT-mine was approximately 2 (F/m). After a period of 38 mm precipitation the contrast between AT-mine and background increased to 6 (F/m). Differences in soil water distribution around the AT- mine caused a maximum dielectric contrast 4.5 (F/m) between background and mine. This effect was less apparent around the AP-mine. Differences in measured and simulated soil water distribution around an AT-mine urge for further investigation.

  5. 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.

  6. Assimilation of surface soil moisture to estimate profile soil water content

    NASA Astrophysics Data System (ADS)

    Heathman, Gary C.; Starks, Patrick J.; Ahuja, Lajpat R.; Jackson, Thomas J.

    2003-08-01

    The use of surface soil water content data as additional input for the Root Zone Water Quality Model in modeling profile soil water content was investigated at four field sites in the Little Washita River Experimental Watershed in south central Oklahoma, coincident with the Southern Great Plains 1997 (SGP97) Hydrology Experiment. Modeled soil water profile estimates were compared to field measurements made periodically during the same time period using a field calibrated time-domain reflectometry (TDR) system. The model was first run in the normal mode with inputs of initial conditions and upper boundary conditions of measured rainfall intensities and daily mean meteorological variables that determined evapotranspiration (ET). Soil hydraulic properties used in the model were estimated from limited soils data information, since in practical terms this is usually the case. Moreover, in our earlier study even the complete description of hydraulic properties based on laboratory and field measurements did not improve the results over average profile estimates using only limited input data. The model runs were then repeated with the daily simulated soil water content in the surface 0-5 cm layer being replaced by 0-5 cm measured soil water content. This process of forcing measured surface water content as additional model input is called direct insertion data assimilation. The simulated profile soil water contents, with and without data assimilation, were compared with TDR-measured profiles to a depth of 60 cm. Gravimetric surface soil water content was measured during SGP97 from June 18 to July 16, 1997 and used as a surrogate for remotely sensed surface moisture data. Data assimilation of surface soil moisture improved model estimates to a depth of 30 cm at all sites. Of particular significance, with data assimilation, model estimates more closely matched the measured dynamic fluctuations of soil moisture in the top 30 cm in response to rainfall events. There was no significant improvement in soil water estimates below the 30 cm depth. This may indicate that data assimilation of surface soil moisture tends to compensate for any errors in model simulations emanating from: (1) errors in the measurement of rainfall intensities or in using 5-min averaged rainfall intensities as done here; (2) errors in using daily average values of meteorological variables that determine ET in a daily ET model; (3) errors in determining hydraulic properties of the surface soil by either laboratory methods or more simple techniques; (4) errors due to the spatial variability of soil hydraulic properties not properly represented in the model.

  7. Interaction between soil moisture memory and different climate variables

    NASA Astrophysics Data System (ADS)

    Stacke, Tobias; Hagemann, Stefan

    2015-04-01

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

  8. Comparison of bioassays by testing whole soil and their water extract from contaminated sites.

    PubMed

    Leitgib, Laura; Kálmán, Judit; Gruiz, Katalin

    2007-01-01

    The harmful effects of contaminants on the ecosystems and humans are characterised by their environmental toxicity. The aim of this study was to assess applicability and reliability of several environmental toxicity tests, comparing the result of the whole soils and their water extracts. In the study real contaminated soils were applied from three different inherited contaminated sites of organic and inorganic pollutants. The measured endpoints were the bioluminescence inhibition of Vibrio fischeri (bacterium), the dehydrogenase activity inhibition of Azomonas agilis (bacterium), the reproduction inhibition of Tetrahymena pyriformis (protozoon), and Panagrellus redivivus (nematode), the mortality of Folsomia candida (springtail), the root and shoot elongation inhibition of Sinapis alba (plant: white mustard) and the nitrification activity inhibition of an uncontaminated garden soil used as "test organism". Besides the standardised or widely used methods some new, direct contact ecotoxicity tests have been developed and introduced, which are useful for characterisation of the risk of contaminated soils due to their interactive nature. Soil no. 1 derived from a site polluted with transformer oil (PCB-free); Soil no. 2 originated from a site contaminated with mazout; Soil no. 3 was contaminated with toxic metals (Zn, Cd, Cu, Pb, As). In most cases, the interactive ecotoxicity tests indicated more harmful effect of the contaminated soil than the tests using soil extracts. The direct contact environmental toxicity tests are able to meet the requirements of environmental toxicology: reliability, sensibility, reproducibility, rapidity and low cost. PMID:16860849

  9. Hydraulic lift: Substantial nocturnal water transport between soil layers by Artemisia tridentata roots

    Microsoft Academic Search

    J. H. Richards; M. M. Caldwell

    1987-01-01

    Diel soil water potential fluctuations reflected daytime depletion and nocturnal resupply of water in upper soil layers. Transpiration suppression experiments demonstrated that water absorption by roots caused the daytime depletion. The soil water potential data and experimental results suggest that at night water absorbed from moist soil by deeper roots is transported to and lost from roots into drier upper

  10. Dielectric model of bound water in wet soils for microwave remote sensing

    Microsoft Academic Search

    V. V. Tikhonov

    1997-01-01

    At present, modelling of dielectric properties of bound water in soil encounters significant obstacles. There are two main reasons: great variety of classifications of water in soils existing and controversial data on physical properties of water in contact with soil particles. Classifying soil water, specialists of different fields propose different approaches taking as principal one or another feature of water

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

    NASA Astrophysics Data System (ADS)

    Madi, Raneem; de Rooij, Gerrit

    2015-04-01

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

  12. 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.

  13. [Behavior of HTO in simulated rice-water-soil ecosystem].

    PubMed

    Shi, Jianjun; Guo, Jiangfeng

    2003-02-01

    The behavior of transportation, accumulation and disappearance of HTO (tritium water) in a simulated rice-water-soil ecosystem was studied by using isotope-tracer techniques for simulated pollutants, and the fitting equation was confirmed by application of the open three-compartment system model and nonlinear regression method. The results showed that HTO in water was not only transferred to other compartments in the ecosystem, but also vaporized into atmosphere rapidly. Both free water tritium and bound tritium were found in the rice, and tritium of hygroscopic and crystalline water was consisted in the soil. The specific activity of free water tritium (or tritium of hygroscopic water) was stronger than that of bound tritium (or tritium of crystalline water). The specific activity of total tritium reduced after reaching the maximum in the rice and soil, and the bound tritium increased slowly. The specific activity of total tritium in stem was the strongest in the rice, and reached equipoise each other in the later stage gradually. The regression equations of accumulation and disappearance for the specific activity of total tritium in the water, soil and rice were given by analyzing the obtained data with exponential regression method. The analysis results of variance showed that each regression equation could describe the behavior of accumulation and disappearance of HTO in the rice-water-soil ecosystems preferably. PMID:12827885

  14. 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.

  15. Investigating Unstable Water Infiltration into Alcohol Contaminated Soils

    NASA Astrophysics Data System (ADS)

    McLeod, H. C.; Smith, J. E.; Henry, E. J.; Brodsky, Y.

    2009-05-01

    A new mechanism causing highly focused, unstable flow exists in soils contaminated with alcohols due to their surface-activity. For example, surface-active compounds can significantly decrease the interfacial tension of the air-water interface and change the pressure-head of the soil water; directly affecting water flow and solute transport in the vadose zone. This study evaluated the fundamental effects of surface-active alcohols on water infiltration into contaminated soils under controlled laboratory conditions. A small scale 3-D glass flow cell and a mini disk tension infiltrometer were used to monitor the rates and physical characteristics of water infiltration from a constant head point source into sands of various textures contaminated with a butanol solution. The results confirmed that water infiltration into these soils is fundamentally and substantially different than the current understanding of infiltration patterns, including previously described mechanisms of wetting front instability. In butanol-contaminated soils, the wetting fronts exhibited highly focused flow with smaller wetted soil volumes, deeper penetration and substantially higher infiltration rates. In addition, the extent of fingered focused flow was confirmed to be texturally dependent, decreasing with grain size and dependent on the constant head boundary. This study characterized a new mechanism of focused, unstable flow with significant implications for groundwater management and solute transport in alcohol contaminated soils.

  16. (Field-scale water and solute flux in soils)

    SciTech Connect

    Luxmoore, R.J.

    1989-10-19

    The traveler evaluated and discussed research results of Mr. Andreas Papritz, a graduate student in soil physics, at the request of the Department Head, Professor Dr. Hannes Fluhler of the Swiss Federal Institute of Technology. He also participated in an international workshop on water and solute transport in field soils by giving an invited presentation, chairing a session, and contributing to a discussion group dealing with preferential flow processes in field soils. 10 refs.

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

    NASA Astrophysics Data System (ADS)

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

    2015-04-01

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

  18. Genetic by environment interactions affect plant–soil linkages

    PubMed Central

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

    2013-01-01

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

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

    Technology Transfer Automated Retrieval System (TEKTRAN)

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

  20. Agri-environmental policy in Germany: soil and water conservation

    Microsoft Academic Search

    Peter Weingarten

    1997-01-01

    This paper is concerned with agri-environmental policy in Germany and focuses in particular on soil and water conservation. At first it discusses to what extent agriculture contributes to erosion and the pollution of surface waters and groundwater with nutrients and pesticides. Whereas erosion is a minor problem in Germany water pollution due to modern and intensive agriculture is of major

  1. 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 The amount of water that may be extracted from an aquifer without causing depletion is primarily dependent upon the ground water recharge. Thus, a quantitative evaluation of spatial and temporal distribution

  2. Soil science Disinfection of drain water in greenhouses

    E-print Network

    Paris-Sud XI, Université de

    Soil science Disinfection of drain water in greenhouses using a wet condensation heater C Steinberg November 1994) Summary — A wet condensation heater has been modified to disinfect drain water were introduced into the disinfection circuit above the heater. Water was checked downstream

  3. Natural products in soil microbe interactions and evolution.

    PubMed

    Traxler, Matthew F; Kolter, Roberto

    2015-06-26

    Covering: up to 2015In recent years, bacterial interspecies interactions mediated by small molecule natural products have been found to give rise to a surprising array of phenotypes in soil-dwelling bacteria, especially among Streptomyces and Bacillus species. This review examines these interspecies interactions, and the natural products involved, as they have been presented in literature stemming from four disciplines: soil science, interspecies microbiology, ecology, and evolutionary biology. We also consider how these interactions fit into accepted paradigms of signaling, cueing, and coercion. PMID:26000872

  4. Modeling temporal and large-scale spatial variability of soil respiration from soil water availability, temperature and

    E-print Network

    Yakir, Dan

    Modeling temporal and large-scale spatial variability of soil respiration from soil water 2003. [1] Field-chamber measurements of soil respiration from 17 different forest and shrubland sites seasonal, interannual and spatial variability of soil respiration as affected by water availability

  5. 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...

  6. Soil and water conservation: Productivity and environmental protection. 3. edition

    SciTech Connect

    Troeh, F.R.; Hobbs, J.A.; Donahue, R.L.

    1999-08-01

    This book is a revision of a landmark book offering a broad coverage of the field of soil and water conservation while fully exploring the hazards posed by erosion, sedimentation, and pollution. Scope includes agriculture, engineering, mining, and other uses of land along with the techniques needed to conserve soil while maintaining environmental quality.

  7. 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...

  8. The Soil and Water Assessment Environmental Consequences of

    E-print Network

    AVSWATInput DataData Processing and Display Weather Stations Mask ArcView Raw GIS Data Land Use Soils x y Weather Stations and Time Series Hydrography Run Output Maps The Soil and Water Assessment Tool #12;The by forest above a certain elevation. The GIS was used to build a conditional replacement model using

  9. Field test of hydrophobic soil clod mulch for soil water conservation in a semiarid area 

    E-print Network

    Horton, Robert

    1977-01-01

    data for Troxler neutron probe, at Lubbock - ~ 22 Neasured volumetric water content as a spot check of the Troxier neutron probe, at Lubbock 24 Geometry of the unmulched soil system used in the model . 35 Geometry of the mulched soil system used...'tailed to monitor the wa er balances of the three plots. A weighing raingauge at the site measured precipitation. A neutron probe was used to measure volumetric soil water content in each plot on a weekly basis. The respective water balances were calculated...

  10. Influence of water table level and soil properties on emissions of greenhouse gases from cultivated peat soil

    Microsoft Academic Search

    Ö. Berglund; K. Berglund

    2011-01-01

    A lysimeter method using undisturbed soil columns was used to investigate the effect of water table depth and soil properties on soil organic matter decomposition and greenhouse gas (GHG) emissions from cultivated peat soils. The study was carried out using cultivated organic soils from two locations in Sweden: Örke, a typical cultivated fen peat with low pH and high organic

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

    PubMed

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

    2011-06-01

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

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

    E-print Network

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

    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...

  13. 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

  14. Supercritical extraction of organic mixtures from soil-water slurries

    E-print Network

    Green, Lynda Ann

    1994-01-01

    Supercritical C02was used to extract orgamc rruxtures from soil-water slurries. The extent of extraction and the equilibrium distribution of the mixture and of the individual components were determined. A single stage batch vessel was used...

  15. Predicting subgrid variability of soil water content from basic soil information

    NASA Astrophysics Data System (ADS)

    Qu, W.; Bogena, H. R.; Huisman, J. A.; Vanderborght, J.; Schuh, M.; Priesack, E.; Vereecken, H.

    2015-02-01

    Knowledge of unresolved soil water content variability within model grid cells (i.e., subgrid variability) is important for accurate predictions of land-surface energy and hydrologic fluxes. Here we derived a closed-form expression to describe how soil water content variability depends on mean soil water content (??()) using stochastic analysis of 1-D unsaturated gravitational flow based on the van Genuchten-Mualem (VGM) model. A sensitivity analysis showed that the n parameter strongly influenced both the shape and magnitude of the maximum of ??(). The closed-form expression was used to predict ??() for eight data sets with varying soil texture using VGM parameters obtained from pedotransfer functions that rely on available soil information. Generally, there was good agreement between observed and predicted ??() despite the obvious simplifications that were used to derive the closed-form expression. Furthermore, the novel closed-form expression was successfully used to inversely estimate the variability of hydraulic properties from observed ??() data.

  16. Soil properties and soil water conditions in the yangjuangou catchment of the chinese loess plateau

    Microsoft Academic Search

    U Schindler; Y Li; R Funk

    2004-01-01

    Soil properties and soil water conditions were assessed for different land use (forest, arable land, grassland) on a silty Calcaric Regosol in the Yangjuangou Catchment of the Chinese Loess Plateau. The loess here is unimodal, poorly sorted with abundant coarse silt, has very low dry bulk density (1.11?–?1.38?g cm) and little organic carbon content (1.6?–?3.7?g kg). The soils are hydrophilic,

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

    E-print Network

    Mattox, April Marie

    2013-07-30

    contents and changes were measured using neutron moisture meter to a depth of 180 cm. Average rooting depth was determined across three soil types. Soil and stem water stable isotopes were used to understand soil water movement. Rooting depth...

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

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

  19. 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.

  20. 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.

  1. Competitive sorption of metals in water repellent soils: Implications for irrigation recycled water

    Microsoft Academic Search

    X. XiongA; F. Stagnitti; N. Turoczy; G. Allinson; P. Li; J. Nieber; T. S. Steenhuis; J. Y. Parlange; M. LeBlanc; A. K. Ziogas; A. J. D. Ferreira; J. J. Keizer

    2005-01-01

    Australia is a water-stressed nation and demand on potable water supply is increasing. Consequently water conservation and reuse are increasingly becoming important. Irrigation of recycled wastewater on water repellent soils is a technology that is being trialled as a means of improving crop production and conserving potable supply. However, recycled water contains potentially harmful heavy metals. This paper reports the

  2. SCALING INFILTRATION AND OTHER SOIL WATER PROCESSES ACROSS DIVERSE SOIL TEXTURAL CLASSES

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Our studies showed that the pore-size distribution index (lambda) can scale Brooks-Corey (B-C) formulation of the soil-water retention curves below the air-entry pressure head across dissimilar (Sandy to clayey) soils, and other key B-C hydraulic parameters ( Ksat, air-entry pressure head, and depen...

  3. Calibration precision of capacitance and neutron soil water content gauges in arid soils

    Microsoft Academic Search

    W. J. Waugh; D. A. Baker; M. K. Kastens; J. A. Abraham

    1996-01-01

    Resonant frequency capacitance (RFC) gauges have been marketed as a replacement for neutron thermalization (NT) gauges for monitoring soil water content in access tubes. Regulatory restrictions have increased the cost of maintaining and operating NT gauges. Commercial RFC gauges have performed satisfactorily for some agronomic applications when tested in relatively uniform or recompacted soil profiles. We compared the calibration statistics

  4. Comparative Resistance of the Soil and the Plant to Water Transport 1

    PubMed Central

    Blizzard, Wayne E.; Boyer, John S.

    1980-01-01

    The resistances to liquid water transport in the soil and plant were determined directly and simultaneously from measurements of soil, root, and leaf water potentials and the flux of water through the soil-plant system to the sites of evaporation in the leaf. For soybean (Merr.) transporting water at a steady rate, water potential differences between soil and root were smaller than between root and leaf over the range of soil water potentials from ?0.2 to ?11 bars. As soil water was depleted, water flow through the soil and plant decreased to one-tenth the maximum rate, but both the soil resistance and plant resistance increased. The plant resistance remained larger than the soil resistance over the entire range of soil water availability. Previous suggestions that the soil is the major resistance have ignored the increase in plant resistance and/or assumed root densities that were too low. PMID:16661531

  5. 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...

  6. 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.

  7. Water balance of sandy soils of Niger, West Africa

    E-print Network

    Payne, William Albert

    1987-01-01

    WATER BALANCE OF SANDY SOILS OF NIGER, WEST AFRICA A Thesis by WILLIAM ALBERT PAYNE Submitted to the Graduate College of Texas A & M University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE December 1987... Major Subject: Soil Science WATER BALANCE OF SANDY SOILS OF NIGER, WEST AFRICA A Thesis by WILLIAM ALBERT PAYNE Approved as to style and content by: L ry Wi ng (Co-Chair of Committe ) Charles Wendt (Co-Chair of Committee) on Newton (Member...

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

    NASA Astrophysics Data System (ADS)

    Tawfik, A. B.; Dirmeyer, P.

    2014-12-01

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

  9. 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...

  10. Modelling daily soil respiration in lowland oak forest during and after soil water saturation events

    NASA Astrophysics Data System (ADS)

    Marjanovic, Hrvoje; Zorana Ostrogovic, Masa; Alberti, Giorgio; Peressotti, Alessandro

    2013-04-01

    Lowland forests of pedunculate oak (Quercus robur L.) in Croatia are acclimated to high soil water content and flooding during the cold part of the year (November - March). Changes in weather pattern and increasing frequency of extreme events, like high precipitation episodes or flooding events out of dormancy period, are becoming more likely. However, the response of these forest ecosystems to flooding during vegetation period is not well investigated. It is well known that soil respiration (SR) depends on soil water content. Nevertheless, some of the most popular daily time-step SR models, like the one of Reichstein et al (2003), do not take into account the effects of soil water saturation which leads to hypoxia in soil and decline of SR. Therefore, we propose a modification of the SR model of Reichstein et. al (2003) that takes into account the effects of high soil water content on SR. In a 37 years old forest of pedunculate oak, located in Jastrebarsko forest (N45.619, E15.688), we measured soil CO2 efflux, every four hours during years 2009 and 2010, using a closed dynamic system with 2-4 chambers. Measured effluxes were averaged to obtain a daily average CO2 efflux. Measurements have shown that high soil water content (i.e. greater that field capacity) strongly decreases soil CO2 efflux, while subsequent soil draining produces bursts in efflux, particularly in spring. Assuming that the measured CO2 efflux corresponds to the total SR, we parameterized the original Reichstein et al (2003) daily time-step SR model and models based on the original but with different modifications (added seasonality in LAI term, modification in soil water status term, addition of new pulse term due to soil draining) and their combinations. Performance of each model was assessed using standard statistical measures (R2, RMSE, Mean Absolute Error, Nash-Sutcliffe Efficiency). Modification of soil water status term significantly improved daily SR estimate (RMSE 0.67) compared to original model (RMSE 0.82), particularly during flooding and post-flooding periods. Annual SR estimated with new model showed greater variability than the estimates with the original model which could be plausible if differences in meteorological conditions between relatively dry 2009 and very wet 2010 are taken into account. New SR models could find application in wet ecosystems or during flooding events. However, additional validation with an independent dataset would be useful.

  11. Water and heat fluxes in desert soils: 1. Field studies

    NASA Astrophysics Data System (ADS)

    Scanlon, Bridget R.

    1994-03-01

    Soil physics parameters were monitored in a semiarid site in the Chihuahuan Desert of Texas to evaluate unsaturated flow processes under natural conditions. The bed of an ephemeral stream was instrumented with neutron probe access tubes to monitor water content for 3 years and with thermocouple psychrometers to monitor water potential and temperature for 2 years. Soil samples were collected from stream and interstream settings for laboratory measurement of water content, water potential, water retention, and saturated hydraulic conductivity. Absence of temporal variations in water content in deep (41-m) profiles indicated that within the accuracy of the neutron probe measurements, water pulses were not moving through the system. Penetration of water after rainfall was generally restricted to the uppermost 0.2 m of the sediments. During rain-free periods, the surficial sediments were extremely dry, as indicated by laboratory-measured water potentials as low as -16 MPa. After rainfall, water potentials were highest at the surface and decreased sharply at the base of the wetting front, with gradients as steep as -13 MPa in 0.05 m. Water potentials were out of range of the in situ psychrometers down to 0.8 m throughout most of the monitoring period because the soils were very dry (?-7 to -8 MPa). Seasonal fluctuations in water potential were recorded at depths of 1.1 and 1.4 m. Water potentials at greater depths remained fairly uniform with time. Except in the shallow subsurface after rainfall, water potentials generally decreased upward; this trend indicated an upward driving force for liquid and isothermal vapor movement. Soil temperatures displayed large seasonal and diurnal fluctuations. Temperatures generally increased with depth in the winter and decreased with depth in the summer. Downward summer temperature gradients opposed upward water potential gradients and resulted in a downward driving force for thermal vapor movement.

  12. 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.

  13. 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.

  14. 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.

  15. List of soils, soil-structure interaction and other related computer programs available for LMVD engineers

    NASA Astrophysics Data System (ADS)

    Radhakrishnan, N.; Senter, P. K.

    1981-05-01

    This report presents a list of soils, soil-structure interaction, and other related computer programs available for engineers of the Lower Mississippi Valley Division. Programs for use in the following subject areas are listed: T-walls; slope stability; piles; sheet piles, and cells; seepage; stress computation, settlement, and consolidation; piezometer data; instrumentation and laboratory data; plotting programs; finite element and finite difference methods; earthquakes and dynamics; and others. Also included are abstracts of some of the listed programs.

  16. 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).

  17. 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

  18. University of Florida Soil and Water Science Department

    E-print Network

    Jawitz, James W.

    University of Florida Soil and Water Science Department SWS 6932: Environmental Monitoring Techniques Course Syllabus General Information Credit/Contact 3 Online Live (Adobe Connect. Quality Assurance Section, 2008. (http://www.dep.state.fl.us/water/sas/sop/sops.htm) Environmental

  19. University of Florida Soil and Water Science Department

    E-print Network

    Jawitz, James W.

    University of Florida Soil and Water Science Department SWS 4932: Environmental Monitoring Techniques Course Syllabus General Information Credit/Contact 3 Online Live (Adobe Connect. Quality Assurance Section, 2008. (http://www.dep.state.fl.us/water/sas/sop/sops.htm) Environmental

  20. REDUCTION IN EXCESS SOIL PHOSPHORUS CONCENTRATIONS USING WATER TREATMENT RESIDUALS

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Livestock production in the southeastern Coastal Plain region has created environmental concern from the effects of excess soil phosphorus (P) concentrations on water quality. In many Coastal aquatic ecosystems, water quality can be at risk by elevated P transport via runoff, erosion, and leaching f...

  1. NEWLY DEVELOPED TECHNOLOGIES FOR SOIL AND WATER CONSERVATION

    Microsoft Academic Search

    E. John Sadler; Kenneth A. Sudduth; Newell R. Kitchen; Robert N. Lerch; Robert J. Kremer; Earl D. Vories

    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 source prevention and reduction practices as well as off-site mitigation practices are described. Examples concerning

  2. 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...

  3. Contributions of groundwater conditions to soil and water salinization

    Microsoft Academic Search

    Ramsis B. Salama; Claus J. Otto; Robert W. Fitzpatrick

    1999-01-01

    Salinization is the process whereby the concentration of dissolved salts in water and soil is increased due to natural or human-induced processes. Water is lost through one or any combination of four main mechanisms: evaporation, evapotranspiration, hydrolysis, and leakage between aquifers. Salinity increases from catchment divides to the valley floors and in the direction of groundwater flow. Salinization is explained

  4. Active Radar Soil Moisture Products for Water use Efficiency Estimation

    Microsoft Academic Search

    M. Doubkova; W. Wagner; C. Kuenzer; Z. Bartalis; S. Hasenauer

    2007-01-01

    The protection of water resources becomes more important with the increasing number of climate hazards. In order to protect water resources we have to fully understand the relationships between carbon and hydrological cycles and how these alter with increasing frequency of climate hazards. Numerous methods have been developed in order to monitor absorbed carbon, evapotranspiration, and soil moisture. Here, methods

  5. Verification of Ground Penetrating Radar for Soil Water Content Measuring

    Microsoft Academic Search

    O. Ermolaeva; A. Zeiliguer

    2009-01-01

    Spatially distributed water at the land surface is a vital natural resource for human being and ecosystems. Soil water content at vadose zone at regional scale controls exchange of moisture and energy between Earth surface and atmosphere, at the catchment scale - the separation of precipitation into infiltration, runoff and evapotranspiration, at the field scale - plant growing, at the

  6. 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...

  7. Solute Export Through Transpiration: A Possible Control of Soil Water Chemistry?

    NASA Astrophysics Data System (ADS)

    Alexander, S. C.; Boyle, D. B.; Alexander, E. C.

    2005-12-01

    Recent studies of soil and ground water interactions in western Minnesota have produced seemingly anomalous results. The soil waters beneath highly transpirative plants (Typha sp., Salix sp. and Populus sp.) in a ground water discharge area developed high calcium sulfate concentrations with only minor enrichment of sodium and chloride. It was expected that concentration of solutes by evapo-transpiration would enrich all ions in the originating ground water more equally. Transpired water is generally assumed to be essentially distilled water although there is little analytical data to support this hypothesis. Given the very high evapotranspiration rates of Western Minnesota, greater than 95% of total water movement, even relatively dilute ion concentrations in the transpired water may be significant in the total chemical budget. To investigate the chemistry of transpired water we adapted techniques that have been used to study total transpiration rates as well as isotopic composition of transpired waters. Our initial results from typha sp. have produced waters that while relatively dilute are distinctly not distilled water. Control samples using de-ionized water over dead vegetation produced minor ion enrichment. All results are in ppm. Ion - Ca, Mg, Na, K, P, Mn, Cl , SO4, NO3-N soil water - 18.5, 2.9, 4.8, 3.8, 0.2, 0.2, 5.6, 2.4, 0.5 transpiration - 1.9, 0.6, 1.5, 8.5, 0.3, 0.4, 9.0, 1.6, <0.1 DI control - 0.1, <0.1, 0.1, <0.1, <0.1, <0.1, <0.1, 1.6, <0.1 The observed transpiration chemistries are in rough agreement with reported literature values for plant stem water. While many plants are known to excrete large molecules the expulsion of ions in transpired water would represent a novel chemical plant pathway.

  8. 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).

  9. 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.

  10. Gas Transport Parameters for Landfill Cover Soils: Effects of Soil Compaction and Water Blockages

    NASA Astrophysics Data System (ADS)

    Wickramarachchi, P. N.; Hamamoto, S.; Kawamoto, K.; Nawagamuwa, U.; Komatsu, T.; Moldrup, P.

    2009-12-01

    Recently, landfill sites have been emerging in greenhouse warming scenarios as a significant source of atmospheric CH4. landfill management strategies have mainly addressed the problem of preventing groundwater contamination and reduction of leachate generation. Being one of the largest source of anthropogenic CH4 emission , the final cover system should also be designed for minimizing the biogas migration into the atmosphere or the areas surrounding the landfill. Compared to the intensive research efforts on hydraulic performances of landfill final cover soil , there are few studies about gas transport characteristics of landfill cover soils. Therefore, the effects of soil physical properties such as bulk density (i.e., compaction level), soil particle size and water blockage effects on the gas exchange in t highly compacted final cover soil are largely unknown. The gas exchange through the final cover soils is controlled by advective and diffusive gas transport. Air permeability (ka) governs the advective gas transport while the soil-gas diffusion coefficient (Dp) governs diffusive gas transport . In this study, the effects of compaction level and water blockage effects on ka and Dp for two landfill final cover soils were investigated. The disturbed soil samples were taken from landfill final covers in Japan and Sri Lanka. A compaction tests were performed for the soil samples with two different size fractions (< 35 mm and < 2.0 mm). In the compaction tests at field water content , the soil samples were repacked into soil cores (i.d. 15-cm, length 12-cm) at two different compaction levels (2700 kN/m2 and 600 kN/m2). After the compaction tests, ka and Dp were measured and then samples were saturated and subsequently drained at different soil-water matric potential (pF; pF equals to log(-?) where ? is soil-water matric potential in cm H2O) of 1.5, 2.0, 3.0, 4.1, and with air-dried (pF 6.0) and oven-dried (pF 6.9) conditions. Results showed that measured Dp values increased rather linearly with increasing soil air content (?) for both compacted and repacked samples using different size fractions and compaction levels in Japanese and Sri Lankan soils. This suggests that the gas diffusion was controlled primarily by the air-filled pore space and was less affected by the pore structure variations such as tortuosity and connectivity. On the other hand, measured ka values showed nonlinear relations with ? and were highly affected by compaction levels and water blockage effects. For the compacted soils at high energy level, peak values in ka appeared at drier conditions than optimum water contents in the compaction curves. This would be partially caused by the pore structure changes at different water conditions under compaction. Combined effects of soil compaction and water reduction will be further discussed taking pore structure characteristics derived from measured Dp and ka into account.

  11. A dynamic soil water threshold for vegetation water stress derived from stomatal conductance models

    Microsoft Academic Search

    Ryan E. Emanuel; Paolo D'Odorico; Howard E. Epstein

    2007-01-01

    In many terrestrial ecosystems, vegetation experiences limitation by different resources at different times. These resources include, among others, light, nutrients, and water. Frequently, however, leaf-level modeling frameworks that unite these limitations rely on empirical functions to scale stomatal conductance as a function of water stress. These functions use prescribed values of soil water content to mark the transition between water-stressed

  12. 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...

  13. 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...

  14. Numerical analysis of kinematic soil-pile interaction

    SciTech Connect

    Castelli, Francesco; Maugeri, Michele [Department of Civil and Environmental Engineering, University of Catania, Viale Andrea Doria no. 6, 95125, Catania (Italy); Mylonakis, George [Department of Civil Engineering, University of Patras, Rio GR-26500, Patras (Greece)

    2008-07-08

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

  15. Vibrational spectroscopy of interacting water molecules

    NASA Astrophysics Data System (ADS)

    Skinner, James

    2012-02-01

    I will discuss a new simulation model for water that includes three-body interactions explicitly, and describe our theoretical approach for calculating OH-stretch spectroscopic observables. I will present illustrative examples, involving pump-probe energy-transfer-induced anisotropy decay in liquid water, IR and Raman line shapes in ice Ih, phase-sensitive SFG spectra of the liquid/vapor interface, and energetics and IR spectra for the different conformations of the water hexamer.

  16. Water-depth dependent infiltration into burnt forest soils

    NASA Astrophysics Data System (ADS)

    Langhans, Christoph; Sheridan, Gary; Noske, Phil; Metzen, Daniel; Lane, Patrick

    2014-05-01

    Infiltration into severely burnt forest soils in South Eastern Australia exhibits a behaviour that is at odds with traditional infiltration theories that assumes a coherent soil matrix, which has important implications for upscaling from plot to hillslope. Infiltration patterns were studied at three severely burnt sites with different soils by applying a blue dye solution during rainfall and runon experiments, and subsequent profile excavation. Rainfall and runon rates were varied on each plot, runoff measured, and orthogonal photos taken during quasi-steady states. From transects on these photos average inundation fractions of the surface were measured, and 1.5 mm horizontal resolution DEMs were generated with image-based software. This information was combined in a DEM inundation algorithm that calculated water depth maps for each plot and rainfall and runon rate. At all three sites, nearly 100% of infiltration occurred through macropores that bypass the matrix of a water repellent layer. Average fractions of subsoil dye staining were 3% in shallow soils with a northerly aspect and low trees, 60% in deep soils with southerly aspects and high trees, and 20% in an intermediate soil. This was consistent with runoff coefficients of 0.94 for the shallow soil, 0.08 for the deep soil, and 0.71 for the intermediate soil. Irrespective of the runoff coefficient or dyed fraction there was a positive relationship between average water depth and infiltration rates on a given plot. Functions of water depth vs. bypass infiltration were derived inversely for each plot by matching average infiltration rates with the rates derived from sampling the water depth distributions. Additionally, characteristic bypass infiltration rates for all sites as function of runon and rainfall intensity were derived, normalized by the maximum infiltration rate at full inundation. These infiltration functions represent the water depth-dependent dynamics of runoff generation in bypass infiltration-dominated soils much better than traditional wetting front models. They are therefore more appropriate for upscaling plot scale runoff generation to the entire hillslope in those soils.

  17. Interactions Among Grassland Plant Species, Microbial Communities, and Soil Processes

    Microsoft Academic Search

    V. Eviner; M. Waldrop; E. Schwartz; J. Pett-Ridge; M. Firestone

    2002-01-01

    Plant-microbial interactions are thought to be an important determinant of ecosystem processes, yet we do not know whether impacts of plant species on soil microbial community composition translate to impacts on function. We established field plots in a California annual grassland of five plant monocultures for two years to determine the effects of different plant species on the composition of

  18. 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.

  19. Upscaled soil-water retention using van Genuchten's function

    USGS Publications Warehouse

    Green, T.R.; Constantz, J.E.; Freyberg, D.L.

    1996-01-01

    Soils are often layered at scales smaller than the block size used in numerical and conceptual models of variably saturated flow. Consequently, the small-scale variability in water content within each block must be homogenized (upscaled). Laboratory results have shown that a linear volume average (LVA) of water content at a uniform suction is a good approximation to measured water contents in heterogeneous cores. Here, we upscale water contents using van Genuchten's function for both the local and upscaled soil-water-retention characteristics. The van Genuchten (vG) function compares favorably with LVA results, laboratory experiments under hydrostatic conditions in 3-cm cores, and numerical simulations of large-scale gravity drainage. Our method yields upscaled vG parameter values by fitting the vG curve to the LVA of water contents at various suction values. In practice, it is more efficient to compute direct averages of the local vG parameter values. Nonlinear power averages quantify a feasible range of values for each upscaled vG shape parameter; upscaled values of N are consistently less than the harmonic means, reflecting broad pore-size distributions of the upscaled soils. The vG function is useful for modeling soil-water retention at large scales, and these results provide guidance for its application.

  20. 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.

  1. Association of water spectral indices with plant and soil water relations in contrasting wheat genotypes.

    PubMed

    Gutierrez, Mario; Reynolds, Matthew P; Klatt, Arthur R

    2010-07-01

    Spectral reflectance indices can be used to estimate the water status of plants in a rapid, non-destructive manner. Water spectral indices were measured on wheat under a range of water-deficit conditions in field-based yield trials to establish their relationship with water relations parameters as well as available volumetric soil water (AVSW) to indicate soil water extraction patterns. Three types of wheat germplasm were studied which showed a range of drought adaptation; near-isomorphic sister lines from an elite/elite cross, advanced breeding lines, and lines derived from interspecific hybridization with wild relatives (synthetic derivative lines). Five water spectral indices (one water index and four normalized water indices) based on near infrared wavelengths were determined under field conditions between the booting and grain-filling stages of crop development. Among all water spectral indices, one in particular, which was denominated as NWI-3, showed the most consistent associations with water relations parameters and demonstrated the strongest associations in all three germplasm sets. NWI-3 showed a strong linear relationship (r(2) >0.6-0.8) with leaf water potential (psi(leaf)) across a broad range of values (-2.0 to -4.0 MPa) that were determined by natural variation in the environment associated with intra- and inter-seasonal affects. Association observed between NWI-3 and canopy temperature (CT) was consistent with the idea that genotypes with a better hydration status have a larger water flux (increased stomatal conductance) during the day. NWI-3 was also related to soil water potential (psi(soil)) and AVSW, indicating that drought-adapted lines could extract more water from deeper soil profiles to maintain favourable water relations. NWI-3 was sufficiently sensitive to detect genotypic differences (indicated by phenotypic and genetic correlations) in water status at the canopy and soil levels indicating its potential application in precision phenotyping. PMID:20639342

  2. Association of water spectral indices with plant and soil water relations in contrasting wheat genotypes

    PubMed Central

    Gutierrez, Mario; Reynolds, Matthew P.; Klatt, Arthur R.

    2010-01-01

    Spectral reflectance indices can be used to estimate the water status of plants in a rapid, non-destructive manner. Water spectral indices were measured on wheat under a range of water-deficit conditions in field-based yield trials to establish their relationship with water relations parameters as well as available volumetric soil water (AVSW) to indicate soil water extraction patterns. Three types of wheat germplasm were studied which showed a range of drought adaptation; near-isomorphic sister lines from an elite/elite cross, advanced breeding lines, and lines derived from interspecific hybridization with wild relatives (synthetic derivative lines). Five water spectral indices (one water index and four normalized water indices) based on near infrared wavelengths were determined under field conditions between the booting and grain-filling stages of crop development. Among all water spectral indices, one in particular, which was denominated as NWI-3, showed the most consistent associations with water relations parameters and demonstrated the strongest associations in all three germplasm sets. NWI-3 showed a strong linear relationship (r2 >0.6–0.8) with leaf water potential (?leaf) across a broad range of values (–2.0 to –4.0 MPa) that were determined by natural variation in the environment associated with intra- and inter-seasonal affects. Association observed between NWI-3 and canopy temperature (CT) was consistent with the idea that genotypes with a better hydration status have a larger water flux (increased stomatal conductance) during the day. NWI-3 was also related to soil water potential (?soil) and AVSW, indicating that drought-adapted lines could extract more water from deeper soil profiles to maintain favourable water relations. NWI-3 was sufficiently sensitive to detect genotypic differences (indicated by phenotypic and genetic correlations) in water status at the canopy and soil levels indicating its potential application in precision phenotyping. PMID:20639342

  3. Effect of Plant-derived Hydrophobic Compounds on Soil Water Repellency in Dutch Sandy Soils

    NASA Astrophysics Data System (ADS)

    Mao, Jiefei; Dekker, Stefan C.; Nierop, Klaas G. J.

    2013-04-01

    Soil water repellency or hydrophobicity is a common and important soil property, which may diminish plant growth and promotes soil erosion leading to environmentally undesired situations. Hydrophobic organic compounds in the soil are derived from vegetation (leaves, roots, mosses) or microorganisms (fungi, bacteria), and these compounds induce soil water repellency (SWR) and can be called SWR-biomarkers. As common hydrophobic constituents of organic matter, plant lipids are mainly from wax layers of leaves and roots, whereas cutins and suberins as aliphatic biopolyesters occur in leaves and roots, respectively. Their unique compositions in soil can indicate the original vegetation sources. To investigate the individual or combined effects of the hydrophobic compounds on SWR and their possible associations with each other, we conducted experiments to analyse the organic composition of Dutch coastal dune sandy soils in relation to SWR. DCM/MeOH solvent is used to remove solvent soluble lipids. BF3-methanol is utilized to depolymerize cutins and suberins from isopropanol/NH3 extractable organic matter. Total organic carbon (TOC) has a positive linear relation with SWR only for those soils containing low TOC (

  4. Influence of arbuscular mycorrhizal fungi on soil structure and soil water characteristics of vertisols

    Microsoft Academic Search

    Birgitte Neergaard Bearden

    2001-01-01

    The influence of inoculation with arbuscular mycorrhizal fungi (AM fungi) on soil water characteristics of fast and slowly wetted vertisol samples was studied. Vertisols characteristically have a low stability to wetting, and the disruption of their larger pores when they swell leads to reduced water infiltration and thereby to runoff. The degree of aggregate breakdown determines the ability of the

  5. 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 ...

  6. Developing joint probability distributions of soil water retention characteristics

    Microsoft Academic Search

    Robert F. Carsel; Rudolph S. Parrish

    1988-01-01

    A method is presented for developing probability density functions for parameters of soil moisture relationships of capillary head (h(Phi)) and hydraulic conductivity (K(Phi)). These soil moisture parameters are required for the assessment of water flow and solute transport in unsaturated media. The method employs a statistical multiple regression equations proposed in the literature for estimating (h(Phi)) or (K(Phi)) relationships using

  7. 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.

  8. Surface reactions of chromium in soils and waters

    Microsoft Academic Search

    Scott E. Fendorf

    1995-01-01

    Chromium is a redox active metal that persists as either Cr(III) or Cr(VI) in the environment. These two oxidation states have opposing toxicities and mobilities: Cr(III) is rather benign and immobile in soils while Cr(VI) is toxic and readily transported. Reactions influencing Cr chemistry in soils and waters must be known in order to predict and understand the fate of

  9. 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).

  10. 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

  11. 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.

  12. Mulch tillage for conserving soil water

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Mulching is the practice of maintaining organic or inorganic materials on or applying them to the soil surface. It is an ancient practice, but through the years clean tillage that incorporated crop residues and also controlled weeds became the norm. Frequent and deep tillage often was promoted to co...

  13. 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 ...

  14. The impact of soil freezing/thawing processes on water and energy balances

    NASA Astrophysics Data System (ADS)

    Zhang, Xia; Sun, Shufen

    2011-01-01

    A frozen soil parameterization coupling of thermal and hydrological processes is used to investigate how frozen soil processes affect water and energy balances in seasonal frozen soil. Simulation results of soil liquid water content and temperature using soil model with and without the inclusion of freezing and thawing processes are evaluated against observations at the Rosemount field station. By comparing the simulated water and heat fluxes of the two cases, the role of phase change processes in the water and energy balances is analyzed. Soil freezing induces upward water flow towards the freezing front and increases soil water content in the upper soil layer. In particular, soil ice obviously prevents and delays the infiltration during rain at Rosemount. In addition, soil freezing/thawing processes alter the partitioning of surface energy fluxes and lead the soil to release more sensible heat into the atmosphere during freezing periods.

  15. Importance of soil organic carbon on surface soil water content variability among agricultural fields

    NASA Astrophysics Data System (ADS)

    Manns, Hida R.; Berg, Aaron A.

    2014-08-01

    Improvements to the downscaling estimates of soil water content (SWC) from passive microwave retrievals require detailed knowledge of field scale influences on SWC variability. The Soil Moisture Active Passive Validation Experiment (SMAPVEX-12) field campaign provided SWC and physical properties from 50 cropland fields to assess the influence of soil organic carbon (SOC) on SOC variability in a range of SOC, SWC and soil textural class over a 6 week period. Field average SWC over the duration of the experiment was optimally predicted by combination of soil texture and SOC in all soil wetness conditions, although either %Sand or SOC separately also expressed 82% of variance in SWC over all fields covering three soil textural groups. Soil OC explained greater variance in SWC than texture in dry conditions, while texture predominated in moist conditions. The high correlation between SOC and SWC suggests soil OC may contribute to the initiatives to downscale SWC estimates from satellite to field scale where SWC data are sparse or inaccurate.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. Surface interactions of black carbon and soil minerals

    NASA Astrophysics Data System (ADS)

    Lehmann, J.; Heymann, K.; Nguyen, B.

    2009-04-01

    An important mechanism for stabilization of organic matter in soils is its interaction with mineral surfaces. Studies that investigate the nature and strength of such interactions have focused on non-pyrogenic materials, and examination of interactions between minerals and black carbon are scarce. In a chronosequence of black carbon ages, we can show that aluminum and silicon rapidly accumulates on black carbon surfaces after deposition to soil and reaches equilibrium after about 20 years in an Oxisol in Western Kenya. In an attempt to investigate the nature of the interaction between black carbon and mineral surfaces, we utilized near-edge x-ray fine structure (NEXAFS) spectroscopy of black carbon particles in soil aggregates and artificial mixtures of minerals and black carbon. Cluster analyses of the stack images using scanning transmission x-ray microscopy (STXM) revealed greater amounts of carboxyl contents, but also accumulation of aliphatic compounds. The latter may not stem from oxidized surfaces of black carbon particles themselves but adsorbed non-black carbon material. Mixing black carbon and minerals clearly showed changes in peak intensities of the C(1s) NEXAFS spectra indicating a chemical interaction between black carbon and mineral surfaces.

  1. Interactions Between Snow Cover, Frozen Soils, and the Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Schaefer, K.; Zhang, T.; Baker, I.; Lu, L.

    2007-12-01

    We evaluate the complex interactions between frozen soil, snow cover, and the carbon cycle to understand how the soil thermal regime and freeze-thaw processes determine seasonal and inter-annual variability in terrestrial biomass, photosynthesis, respiration, and net CO2 fluxes over continental North America. We use the Simple Biosphere Carnegie-Ames-Stanford Approach (SiBCASA) model driven by the NCEP North American Regional Reanalysis (NARR), the GIMMS NDVI dataset, and in situ snow depth. To improve simulated soil temperatures, we integrated the Sturm et al. [1995] global snow classification system into the snow parameterization from the Community Climate Model and added simple representations of depth hoar and wind slab development. We also added the effects of peat development in tundra and boreal ecosystems. These additions give more realistic soil and snowpack thermodynamic properties, resulting in significantly improved simulated soil temperatures, freeze and thaw depths, and permafrost. Here, we compare simulated and observed soil temperatures, biomass, and carbon fluxes at eddy covariance flux towers representing a broad range of biome types and snow conditions, from permafrost and boreal forests at high latitudes, to deep snow in the northeast US, to wind blown snow of the Great Plains.

  2. Evapotranspiration of soil water movement in small area vegetation

    NASA Astrophysics Data System (ADS)

    Paraskevas, C.; Georgiou, P.; Ilias, A.; Panoras, A.; Babajimopoulos, C.

    2013-12-01

    In Greece, crops are frequently cultivated in small isolated areas in close proximity to roads and bare soils and therefore evapotranspiration is affected by local advection. Under these circumstances, oasis effect conditions are present and evapotranspiration is higher than what is expected. In this paper, the evapotranspiration and soil water dynamics of a cotton crop cultivated in small areas under the oasis effect is studied. To this end, two isolated free-drainage lysimeters cultivated with cotton in the year 2007 were used. Soil moisture of the soil profile of both the lysimeters was monitored with two capacitance water content probes. The soil water balance method was used to estimate crop evapotranspiration and corresponding crop coefficients in one of the two lysimeters. These coefficients were 75% larger than the FAO-56 crop coefficients at the mid-season stage. The FAO-56 and the derived crop coefficients were used for the simulation of the water dynamics in the second lysimeter by the SWBACROS model. The derived crop coefficients for these conditions produced much better results than the FAO-56 crop coefficients. The results were improved when crop coefficient value equal to 2.5 was used for the mid-season stage.

  3. The interaction of various polymers with water 

    E-print Network

    Quock, Billy

    1976-01-01

    that the methylcellulose is more soluble in water at lower temperatures. This must mean that the partial molar heat 39 (3 a HDi of dissolution of methylcellulose (3 n / in water is negative. Polymer P, T For the polymer to be only partially soluble in water at higher...THE INTERACTION OF VARIOUS POLYMERS WITH WATER A Thesis by BILLY OUOCK Submitted to the Graduate College of Texas ASM University in partial fulfillment of the requirement for the degree of MASTER OF SCIENCE May 1976 Major Subject...

  4. Monitoring of soil water content and quality inside and outside the water curtain cultivation facility

    NASA Astrophysics Data System (ADS)

    Ha, K.; Kim, Y.

    2014-12-01

    Water curtain cultivation system is an energy saving technique for winter season by splashing groundwater on the inner roof of green house. Artificial groundwater recharge application to the water curtain cultivation facilities was adopted and tested to use groundwater sustainably in a rural region of Korea. The groundwater level in the test site shows natural trend corresponding rainfall pattern except during mid-November to early April when groundwater levels decline sharply due to groundwater abstraction for water curtain cultivation. Groundwater levels are also affected by surface water such as stream, small dams in the stream and agricultural ditches. Infiltration data were collected from lysimeter installation and monitoring inside and outside water cultivation facility and compared with each other. The infiltration data were well correlated with rainfall outside the facility, but the data in the facility showed very different from the other. The missing infiltration data were attributed to groundwater level rise and level sensor location below water table. Soil water contents in the unsaturated zone indicated rainfall infiltration propagation at depth and with time outside the facility. According to rainfall amount and water condition at the initial stage of a rainfall event, the variation of soil water content was shown differently. Soil water contents and electrical conductivities were closely correlated with each other, and they reflected rainfall infiltration through the soil and water quality changes. The monitoring results are useful to reveal the hydrological processes from the infiltration to groundwater recharge, and water management planning in the water cultivation areas.

  5. The in-situ effects of soil water potential on Phymatotrichum omnivorum sclerotial formation and germination 

    E-print Network

    White, Tammy Lynn

    1988-01-01

    the interactive effects of water potential and temperature on pattern of sclerotial germination, a 3 x 3 factorially designed exper &ment, with 5 replicates per treatment was conducted. Water potentials of -0. 02, -0. 95, and -4. 0 Mpa and temperatures of 17...THE IN-SITU EFFECTS OF SOIL WATER POTENTIAL ON PHPPfA TOTRICHMCY1iVI VORLP1 SCLEROT I AL FORMATION AND GERMINATION A Thesis by TIFF LYNN WHITE Submitted to the Graduate College of Texas A@1 University in partial fulfillment...

  6. [Ecological effect of hygroscopic and condensate water on biological soil crusts in Shapotou region of China].

    PubMed

    Pan, Yan-Xia; Wang, Xin-Ping; Zhang, Ya-Feng; Hu, Rui

    2013-03-01

    By the method of field experiment combined with laboratory analysis, this paper studied the ecological significance of hygroscopic and condensate water on the biological soil crusts in the vegetation sand-fixing area in Shapotou region of China. In the study area, 90% of hygroscopic and condensate water was within the 3 cm soil depth, which didn' t affect the surface soil water content. The hygroscopic and condensate water generated at night involved in the exchange process of soil surface water and atmosphere water vapor, made up the loss of soil water due to the evaporation during the day, and made the surface soil water not reduced rapidly. The amount of the generated hygroscopic and condensate water had a positive correlation with the chlorophyll content of biological soil crusts, indicating that the hygroscopic and condensate water could improve the growth activity of the biological soil crusts, and thus, benefit the biomass accumulation of the crusts. PMID:23755477

  7. Belowground interactions for water between trees and grasses in a temperate semiarid agroforestry system

    Microsoft Academic Search

    María Elena Fernández; Javier Gyenge; Julian Licata; Tomás Schlichter; Barbara J. Bond

    2008-01-01

    A fundamental hypothesis of agroforestry is the complementary use of soil resources. However, productivity of many agroforestry\\u000a systems has been lower than expected due to net competition for water, highlighting the need for a mechanistic understanding\\u000a of belowground interactions. The goal of this study was to examine root–root interactions for water in a temperate semiarid\\u000a agroforestry system, based on ponderosa

  8. 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.

  9. Soil and water conservation policies: Successes and failures

    SciTech Connect

    Napier, T.A. [ed.

    2000-07-01

    This book presents an in-depth look at soil and water conservation programs throughout the world. For as far into the future as one can see, governments will probably topple, power will continue to exchange hands, the climate will undergo continuous change, and the global economy will ebb and flow like the oceans. But for the world's many diverse countries--whether they be highly industrialized or third world--one thing will always remain constant: the need to solve the planet's pressing soil and water conservation problems, as well as implement effective policies. This book addresses: Why do some policy initiatives succeed while others fail?

  10. Effects of Pentachlorophenol and Biotic Interactions on Soil Fauna and Decomposition in Humus Soil

    Microsoft Academic Search

    J. Salminen; J. Haimi; A. Sironen; J. Ahtiainen

    1995-01-01

    In a laboratory experiment, effects of chemical stress (pentachlorophenol, PCP, at concentrations of 0, 50, and 500 mg\\/kg) and biotic interactions (nematodes in the presence or absence of collembolas and enchytraeids) on the community structure of soil animals and decomposition processes were studied. PCP was strongly adsorbed to humus that contained 65% organic matter. Numbers of fungal-feeding nematodes decreased significantly

  11. Microbial interaction networks in soil and in silico

    NASA Astrophysics Data System (ADS)

    Vetsigian, Kalin

    2012-02-01

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

  12. 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...

  13. 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.

  14. The Influence of Airflow on the Vertical Infiltration of Water Into Soil

    Microsoft Academic Search

    Graham J. Weir; Warwick M. Kissling

    1992-01-01

    The vertical flow of air and water into a Gardner soil is investigated numerically and analytically. Instantaneously applying a constant head of water to the soil surface initially produces a rapid diffusive change in air pressure in the soil, and a slower diffusive change in water content. Fluid flow comprises a region of descending water at air entry conditions, below

  15. The influence of airflow on the vertical infiltration of water into soil

    Microsoft Academic Search

    Graham J. Weir; Warwick M. Kissling

    1992-01-01

    The vertical flow of air and water into a Gardner soil is investigated numerically and analytically. Instantaneously applying a constant head of water to the soil surface initially produces a rapid diffusive change in air pressure in the soil, and a slower diffusive change in water content. Fluid flow comprises a region of descending water at air entry conditions, below

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

    E-print Network

    Jawitz, James W.

    -profit, and many other environmentally-related fields such as: · USDA · EPA · Private Consulting Firms · WaterContact 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 WATER SCIENCE u n

  17. Effect of soil water potential on radish ( Raphanus sativus L.) growth and water use under drip irrigation

    Microsoft Academic Search

    Yaohu Kang; Shuqin Wan

    2005-01-01

    Radish (Raphanus sativus L.) is a moisture loving vegetable and is widely planted in China. Soil water is one of most important factors affecting the yield and quality of radishes. Field experiments for the effect of soil water potential on radish growth and water use were carried out in 2001 and 2002. The experiment included five treatments, which controlled soil

  18. The utility of surface temperature measurements for the remote sensing of surface soil water status

    NASA Technical Reports Server (NTRS)

    Idso, S. B.; Jackson, R. D.; Reginato, R. J.; Schmugge, T. J.

    1975-01-01

    Experiments carried out on an Avondale loam soil indicated that the thermal inertia concept of soil water content detection is reasonably sound. The volumetric water contents of surface soil layers between 2 and 4 cm thick were found to be linear functions of the amplitude of the diurnal surface soil temperature wave for clear day-night periods. They were also found to be linear functions of the daily maximum value of the surface soil-air-temperature differential. Tests on three additional soils ranging from sandy loam to clay indicated that the relations determined for Avondale loam could not be accurately applied to these other soil types. When the moisture characteristic curves of each soil were used to transform water contents into pressure potentials, however, it was found that soil water pressure potential could be determined without prior knowledge of soil type, and thus its value as a potential soil water status survey tool was significantly enhanced.

  19. Interactive effect of organic amendment and environmental factors on degradation of 1,3-dichloropropene and chloropicrin in soil.

    PubMed

    Qin, Ruijun; Gao, Suduan; Ajwa, Husein; Hanson, Bradley D; Trout, Thomas J; Wang, Dong; Guo, Mingxin

    2009-10-14

    Soil organic matter is an important factor affecting the fate of soil fumigants; therefore, the addition of organic amendments to surface soils could reduce fumigant emissions by accelerating fumigant degradation. Experiments were conducted to determine the degradation of fumigants [a mixture of cis- and trans-1,3-dichloropropene (1,3-D) and chloropicrin (CP), a similar composition as in Telone C35] in soils with organic amendment under a range of soil moisture, temperature, sterilization, and texture conditions. Degradation of the fumigants followed availability-adjusted first-order or pseudo-first-order kinetics with slower degradation of 1,3-D than CP. Increasing soil water content from 5 to 17.5% (w/w) slightly increased the degradation of 1,3-D, but not that of CP. Five different organic amendments at 5% (w/w) increased fumigant degradation 1.4-6.3-fold in this study. The degradation of both fumigants was accelerated with increasing amount of organic material (OM). Little interaction between soil moisture and OM was observed. Autoclave sterilization of soils did not reduce degradation of either fumigant; however, increasing the incubation temperature from 10 to 45 degrees C accelerated fumigant degradation 5-14 times. Soil texture did not affect 1,3-D degradation, but CP degraded more rapidly in finer-textured soil. These results suggest that OM type and rate and soil temperature are the most important factors affecting the degradation of 1,3-D and CP. PMID:19722521

  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. Modelling interactions between soil evolution and diffusive surface processes

    NASA Astrophysics Data System (ADS)

    Kirkby, Mike; Johnson, Michelle; Gloor, Emanual

    2014-05-01

    Bioturbation, combined with settlement under gravity, generates profiles of bulk density, porosity and hydraulic conductivity (Ksat). Rates of bioturbation are linked to rates of diffusive downslope sediment transport (creep) and rates can be compared via the increase in OSL ages of soil aggregate grains with depth. Some primary porosity is also produced by weathering of rock to saprolite, often with little reduction in bulk density but some dilation of joints. Downward percolation of rain water near the surface is controlled by the diffusion-induced decrease in porosity and Ksat, driving lateral subsurface flow in the zone of fluctuating water table, and leaving progressively less water for downward percolation. As the depth to the weathering front is varied, progressively less water is therefore available for weathering, producing the observed decrease in weathering rate with increasing soil depth. These processes are modelled by repeatedly applying a stochastic realisation of daily rainfalls for an area until the annual hydrological cycle stabilises, providing the average partition of rainfall into its components of evapotranspiration, lateral flow and downward percolation, with depth in the soil. The average hydrology is then applied to drive evolution of the weathering profile over longer time spans.

  2. On the Links Between Photosynthesis and Soil Water Balance

    NASA Astrophysics Data System (ADS)

    Daly, E.; Porporato, A.; Rodriguez-Iturbe, I.

    2002-12-01

    The equations of soil moisture dynamics and a model of leaf gas exchange and water transport through the Soil-Plant-Atmosphere Continuum (SPAC) are coupled to explore the dependence of plant CO2 assimilation on soil moisture. The model is also coupled with a daily growing boundary layer model, that gives the values of air specific humidity and potential temperature during the day. Two different approaches for modeling stomatal conductance gs are implemented and compared. One is the mixed-empirical formulation of stomatal conductance used by Jarvis (1976), who assumed a multiplicative relationship among the main environmental factors affecting stomatal movement; the other one is the empirical relationship between stomatal conductance and assimilation introduced by Ball et al. (1987) and modified by Leuning (1990, 1995), that assume a direct dependence of stomatal movement on the assimilation rate. This second approach is extended to include drought conditions and the common bases underlying the two approaches are elucidated. The model also gives the soil moisture value below which plants are under stress and the moisture content at the wilting point. These are used to evaluate the probability distribution of soil moisture, carbon assimilation by photosynthesis and plant water stress, thus providing a more physical basis to a previous stochastic model of soil moisture by the authors.

  3. 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...

  4. 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.

  5. Landscape controls on long-term fluxes of water, energy and soil formation in a Mediterranean catchment

    NASA Astrophysics Data System (ADS)

    Román Sánchez, Andrea; Giráldez, Juan V.; Vanwalleghem, Tom

    2015-04-01

    Soil formation is a complex process that depends on factors such as bedrock, climate, relief, vegetation and time. Despite of the great effort dedicated to explore these processes, little is known there is not a precise about the quantitative relationship between geomorphology and soil formation, especially on long timescales. In order to understand this complex interaction is important to investigate some quantitative aspects of the processes that drive pedogenesis. The integration of quantitative aspects by means of modeling will help us to understand better the soil formation upscaling this information at large scales of time. In this study the effect of aspect and relative elevation on long- term soil formation has been studied on two converging slopes. The geometry generates microclimates that can structure ecosystems and affect depth and surface processes regimes. In our study area, located in Sierra Morena, in Cordoba, S Spain, we studied 10 soil profiles along a catena distributed in various topographic conditions: plateau area, north and south facing slope. These profiles were sampled each 10-20 cm depth in order to study the quantitative differences in physical and chemical soil properties. A new, spatially explicit model is presented of water infiltration and redistribution, temperature coupled to soil forming processes as a function of properties such as topographical variables, like aspect, slope, climate variables and vegetation. This model is based on a simple soil water balance model and runs at a daily time step. As paleoclimate data for rainfall and temperature is generally only available at the yearly or seasonal time scale, a weather generator was used in order to generate the necessary input data. Model output, for example mean annual water percolation, are then compared against field observations to evaluate whether the model can explain important soil properties, such as for example total weathered soil depth or texture. This model allows to compare for different topographical positions the importance of water and energy fluxes, erosion and soil formation and incorporate in a simple way their interactions quantitatively.

  6. 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.

  7. 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.

  8. Interactions of ionic liquids and water.

    PubMed

    Ficke, Lindsay E; Brennecke, Joan F

    2010-08-19

    Experimental excess enthalpies of ionic liquid and water mixtures in combination with calculated CHELPG atomic charges were used to investigate the interactions between the species in solution. The excess enthalpies of ionic liquids in water were obtained by calorimetry, using a Setaram C80 calorimeter, including temperatures from (313.15 to 348.15) K and the entire range of composition. The ionic liquids investigated all contain the 1-ethyl-3-methylimidazolium cation except one, which has an added hydroxyl group on the cation (1-(2-hydroxyethyl)-3-methylimidazolium cation). The anions investigated are ethylsulfate, methylsulfate, hydrogensulfate, trifluoromethanesulfonate, methanesulfonate, and trifluoroacetate, and these will demonstrate the effect of systematically varying the substituents on the anion. The CHELPG atomic charges on the cations and anions were calculated using the Gaussian 03 program. The CHELPG atomic charges are consistent with the observed trends in excess enthalpy and provide insight into cation/water, anion/water, and cation/anion interactions. PMID:20701381

  9. Northern Namibia's Ehenge: marginal soil with high water use efficiency

    NASA Astrophysics Data System (ADS)

    Prudat, Brice

    2015-04-01

    Farmers of North-Central Namibia identify Ehenge as a common soil type. It has been described so far as a (hypoluvic hyperalbic) Arenosol. The sequence of characteristic horizons is as follows: sandy A and E; thin accumulation horizon Bt on top of a Bg horizon. Farmers consider this soil as nutrient-poor with a deep loose sand layer on top of a very hard layer at a depth of several decimeters. Despite its low nutrient content, the Ehenge is usually cultivated because it holds water for a longer period than some more nutrient-rich soils. This is attributed to the combination of the sandy texture and the hardpan, generating rapid infiltration, but protection from evaporation and drainage from the root zone of the millet typically planted in northern Namibia. The development of agriculture in North-Central Namibia will determine the future use and preservation of these soils, as the presence of hardpan is commonly considered to be a limiting factor for agricultural development. Our research on the hydrology of the Ehenge demonstrates that this soil has a large potential for agricultural water use efficiency, in an area with very limited water resources if understood in the context of its current use by the Namibian farmers.

  10. Predawn plant water potential does not necessarily equilibrate with soil water potential under well-watered conditions

    Microsoft Academic Search

    L. A. Donovan; M. J. Linton; J. H. Richards

    2001-01-01

    Predawn leaf water potential (Ow) and xylem pressure potential (Op) are expected to be in equilibrium with the soil water potential (soil Ow) around roots of well-watered plants. We surveyed 21 plant species (desert, chaparral, and coastal salt marsh species, as well as two temperate tree and two crop species) for departures from this expectation and for two potential mechanisms

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

    E-print Network

    Tokumoto, Ieyasu

    2013-05-09

    karst savanna with ~50% woody cover to monitor spatial and temporal variations in soil moisture and root water uptake with neutron probe and time-domain reflectometry measurements. Bulk density was measured using gamma densitometry. Measurements were...

  12. Discrete modeling of water and pesticide movement in soil

    NASA Astrophysics Data System (ADS)

    Vollmayr, Hans; Kleint, Friedemann; Schüürmann, Gerrit

    Simulations of water and pesticide movement are presented for the unsaturated zone. Water movement is studied with a two-dimensional Monte Carlo technique, where particles hop between the sites of a square lattice according to probabilistic rules. We developed this lattice gas method for two-dimensional simulations of water flow in inhomogeneous media. Generalization to three dimensions is straightforward. The dynamics of the pesticide is simulated by particle tracking. After presenting the underlying discrete algorithms we emphasize calibration of the system. A soil is divided into homogeneous horizons, and our model is compared with the conventional one-dimensional model PESTLA. We observe good agreement for both water content profile and pesticide distribution. The random elements in our algorithms cause moderate fluctuations in the results. As an example of two-dimensional simulation, spatiotemporal pesticide patterns under a ridge are compared with the distribution under a flat soil surface.

  13. 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.

  14. 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.

  15. Plant Response to Differential Soil Water Content and Salinity

    NASA Astrophysics Data System (ADS)

    Moradi, A. B.; Dara, A.; Kamai, T.; Ngo, A.; Walker, R.; Hopmans, J. W.

    2011-12-01

    Root-zone soil water content is extremely dynamic, governed by complex and coupled processes such as root uptake, irrigation, evaporation, and leaching. Root uptake of water and nutrients is influenced by these conditions and the processes involved. Plant roots are living and functioning in a dynamic environment that is subjected to extreme changes over relatively short time and small distances. In order to better manage our agricultural resources and cope with increasing constraints of water limitation, environmental concerns and climate change, it is vital to understand plants responses to these changes in their environment. We grew chick pea (Cicer arietinum) plants, in boxes of 30 x 25 x 1 cm dimensions filled with fine sand. Layers of coarse sand (1.5 cm thick) were embedded in the fine-sand media to divide the root growth environment into sections that were hydraulically disconnected from each other. This way, each section could be independently treated with differential levels of water and salinity. The root growth and distribution in the soil was monitored on daily bases using neutron radiography. Daily water uptake was measured by weighing the containers. Changes of soil water content in each section of the containers were calculated from the neutron radiographs. Plants that part of their root system was stressed with drought or salinity showed no change in their daily water uptake rate. The roots in the stressed sections stayed turgid during the stress period and looked healthy in the neutron images. However the uptake rate was severely affected when the soil in the non-stressed section started to dry. The plants were then fully irrigated with water and the water uptake rate recovered to its initial rate shortly after irrigation. The neutron radiographs clearly illustrated the shrinkage and recovery of the roots under stress and the subsequent relief. This cycle was repeated a few times and the same trend could be reproduced. Our results show that plants' response to water- or salinity-stress ranges from full compensation to severe reduction in transpiration, depending on the availability of water in their surrounding soil. Results of applying different treatments of salinity and drought will be shown. Available models of root water uptake will be employed to simulate the obtained results.

  16. 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 ...

  17. Artificial neural network and time series models for predicting soil salt and water content

    Microsoft Academic Search

    Ping Zou; Jingsong Yang; Jianrong Fu; Guangming Liu; Dongshun Li

    2010-01-01

    Volumetric water content of a silt loam soil (fluvo-aquic soil) in North China Plain was measured in situ by L-520 neutron probe (made in China) at three depths in the crop rootzone during a lysimeter experiment from 2001 to 2006. The electrical conductivity of the soil water (ECsw) was measured by salinity sensors buried in the soil during the same

  18. 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…

  19. Financial efficiency of major soil and water conservation measures in West Usambara highlands, Tanzania

    Microsoft Academic Search

    A. J. M. Tenge; J. De graaff; J. P. Hella

    2005-01-01

    Soil and Water Conservation (SWC) measures are needed to control soil erosion and sustain agricultural production on steep slopes of West Usambara mountains. However, the adoption by farmers of the recommended soil and water conservation measures is low and soil erosion continues to be a problem. It could well be that the reason for the low adoption is that the

  20. Soil physical properties, water depletion and crop development under traditional and conservation tillage in southern Spain

    Microsoft Academic Search

    F. Moreno; F. Pelegrín; J. E. Fernández; J. M. Murillo

    1997-01-01

    Tillage methods affect soil physical properties and, thus, have a direct influence on the replenishment and depletion of soil water storage and crop performance. This study was conducted to determine the effects of traditional and conservation tillage on soil physical properties, soil water replenishment and depletion, and crop development and yield under southern Spanish conditions. The experiments were carried out

  1. 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...

  2. Soil and water conservation investments and rural development in China

    Microsoft Academic Search

    Nico Heerink; Xiaobin Bao; Rui Li; Kaiyu Lu; Shuyi Feng

    2009-01-01

    This study uses a unique set of annual provincial data on soil and water conservation (SWC) investments during the period 1989–2005 to estimate the impact of such investments on the extent and severity of erosion, the growth rate of agricultural gross domestic product (GDP) and rural poverty reduction in China. We find that SWC investments made by local governments have

  3. 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...

  4. Midwest soil and water conservation: Past, present and future

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil and water conservation was, is, and will continue to provide the foundation for sustainable resource management in the U.S. Corn and Soybean Belt. This chapter briefly reviews the natural resource foundation, settlement patterns, and development of conservation programs in the U.S. Midwest. The...

  5. 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...

  6. Agricultural Grassland, Soil and Water Research Laboratory, Temple, TX

    E-print Network

    Agricultural Research Service Grassland, Soil and Water Research Laboratory, Temple, TX Monitoring, Modeling and Decision-Making Daren Harmel USDA-ARS, Temple, TX Agricultural Research Service Grassland monitoring, modeling, and decision- making (if time and interest!!) Agricultural Research Service Grassland

  7. Treatment Techniques of Oil-Contaminated Soil and Water Aquifers

    Microsoft Academic Search

    Mohammed M. Amro

    Many operations in the petroleum exploration, production and transportation have the potential to affect the environment in different degrees. Leakages from pipelines, oil wells, underground storage tanks of gas stations, improper disposal of petroleum wastes and stranded oil spills are the major sources of surface and groundwater contamination. The removal of hydrocarbons from contaminated soil and water aquifer is an

  8. Quantification of soil water evaporation using TDR-microlysimetry

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water evaporation is conventionally measured using microlysimeters by evaluating the daily change in mass. Daily removal is laborious and replacement immediately after irrigation events is impractical because of field wetness which leads to delays and an underestimation of evaporation. Irrigati...

  9. Button Heat-Pulse Sensor for Soil Water Content Measurements

    Microsoft Academic Search

    Antonio Valente; Salviano Soares; R aul Morais; J. M. Baptista; Manuel Cabral

    2010-01-01

    Recent developed button heat pulse probes (BHPP) demonstrated a great potential for soil water content measurements. This new probe compared to conventional heat pulse probes (HPP), does not use needles, and measurement accuracy is significantly improved. This new design, with the possibility to assembly the probe and electronics in the same package, with low-cost, and with less power consumption compared

  10. LABORATORY CHARACTERIZATION OF CAPACITANCE SENSORS FOR MEASURING SOIL WATER CONTENT

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Automated sensing of soil water content with capacitance methods is common due to the relative ease of installation and monitoring at multiple sites. The resonant frequency of an inductance-capacitance circuit is a function of the dielectric permittivity of the material surrounding the ring-capacito...

  11. Soil sheaths, photosynthate distribution to roots, and rhizosphere water relations for Opuntia ficus-indica

    Microsoft Academic Search

    Bingru Huang; Gretchen B. North; Park S. Nobel

    1993-01-01

    Soil sheaths incorporating aggregated soil particles surround young roots of many species, but the effects of such sheaths on water movement between roots and the soil are largely unknown. The quantity and location of root exudates associated with soil sheath along the entire length of its young roots, except within 1.4 cm of the tip. The soil sheaths, which average

  12. HSWCD EMPLOYMENT OPPORTUNITY The Highlands Soil and Water Conservation District (HSWCD) has created a new full-time

    E-print Network

    Watson, Craig A.

    HSWCD EMPLOYMENT OPPORTUNITY The Highlands Soil and Water Conservation District (HSWCD) has created history. Highlands Soil & Water Conservation District prohibits discrimination in all its programs, sexual orientation, and marital or family status. Highlands Soil & Water Conservation District

  13. Experimental nitrogen, phosphorus, and potassium deposition decreases summer soil temperatures, water contents, and soil CO2 concentrations in a northern bog

    NASA Astrophysics Data System (ADS)

    Wendel, S.; Moore, T.; Bubier, J.; Blodau, C.

    2010-08-01

    Ombrotrophic peatlands depend on airborne nitrogen (N), whose deposition has increased in the past and lead to disappearance of mosses and increased shrub biomass in fertilization experiments. The response of soil water content, temperature, and carbon gas concentrations to increased nutrient loading is poorly known and we thus determined these data at the long-term N fertilization site Mer Bleue bog, Ontario, during a two month period in summer. Soil temperatures decreased with NPK addition in shallow peat soil primarily during the daytime (t-test, p<0.05) owing to increased shading, whereas they increased in deeper peat soil (t-test, p<0.05), probably by enhanced thermal conductivity. RMANOVA suggested interactions between N and PK addition in particular soil layers and strong interactions between soil temperatures and volumetric water contents (p<0.05). Averaged over all fertilized treatments, the mean soil temperatures at 5 cm depth decreased by 1.3 °C and by 4.7 °C (standard deviation 0.9 °C) at noon. Water content was most strongly affected by within-plot spatial heterogeneity but also responded to both N and PK load according to RMANOVA (p<0.05). Overall, water content and CO2 concentrations in the near-surface peat (t-test, p<0.05) were lower with increasing N load, suggesting more rapid soil gas exchange. The results thus suggest that changes in bog ecosystem structure with N deposition have significant ramifications for physical parameters that in turn control biogeochemical processes.

  14. Interactions between soil scarification and Norway spruce seedling types

    Microsoft Academic Search

    Karin Johansson; Urban Nilsson; H. Lee Allen

    2007-01-01

    Interactions between scarification treatments and seedling types of Norway spruce were examined at two different locations in southern Sweden. The scarification treatments were not scarified control, mounding and soil inversion and the seedling types were a 10 week-old containerized seedling (mini seedling), a 2 year-old containerized seedling and a 2 year-old hybrid seedling, grown as a containerized seedling the first year and as

  15. Electrical properties of water in clay and silty soils

    NASA Astrophysics Data System (ADS)

    Saarenketo, Timo

    1998-10-01

    In order to better understand ground penetrating radar (GPR) results obtained in road surveys and site investigations, the dielectric properties and electrical conductivity of four silt and clay soils were measured at different densities and moisture contents ranging from oven dry material to the plastic state. The real parts K' and imaginary parts K? of the relative dielectric permittivity values of the soils were measured with an HP Surface Network Analyzer over a frequency range from 30 MHz to 3.0 GHz. A dielectric and electrical conductivity meter produced by Adek was also used. The results suggest that water in soils can be classified according to its electrical properties as: (1) an adsorption water layer, also known as the hygroscopic water layer; (2) a viscous or capillary water layer; and (3) free water. The measurements also showed that the adsorption water layer can be divided into inner and outer layers in accordance with the electrical double layer theory. The imaginary part of the dielectric value of the material is formed mainly in the outer layer and partly in the viscous (capillary) water layer, which also has two layers with differing electrical properties. The measurements also clearly showed that if the Cation Exchange Capacity (CEC) of a material is low, the water molecules are orderly arranged around the soil particles and the dielectric values of the bound water layers remain almost independent of frequency. If the CEC increases, the molecular structure of the bound water layers is disturbed and the water molecules more easily follow the changing AC field so that the dielectric value is higher. These materials are also highly dielectrically dispersive, especially at GPR frequencies below 400 MHz. Increasing CEC correlates well with increasing imaginary part of the adsorption water layer. Measured ohmic electrical conductivities were low at low moisture content and increased as the outer viscous water layer developed with higher moisture content. A clear jump in electrical conductivity takes place when the free unbound water starts to fill the pores between the mineral grains.

  16. Using soil sensing technology to examine interactions and controls between ectomycorrhizal growth and environmental factors on soil CO 2 dynamics

    Microsoft Academic Search

    Niles J. Hasselquist; Rodrigo Vargas; Michael F. Allen

    2010-01-01

    Soils play a critical role in the global carbon cycle, yet the biophysical factors regulating soil CO2 dynamics remain unclear. We combined high-frequency in situ observations of fine roots and ectomycorrhizal (EM) fungi with\\u000a data from multiple soil sensor arrays to examine the biophysical interactions influencing soil CO2 production for one year in a mixed conifer forest. Using structural equation

  17. Irrigation Water Source: Effect on Soil Nutrient Dynamics and Microbial Community Composition 

    E-print Network

    Holgate, Leon Carl

    2011-08-08

    reduced carbon in soil without grass (blank) and domestic tap water treatments. E. coli colonies were detected in source water (greywater), but not in leachate suggesting that there was no movement through the soil profile. The results of principal...

  18. Spatial Distribution of Soil Nutrients in a Northern Everglades Marsh: Water Conservation Area 2A

    E-print Network

    Florida, University of

    Spatial Distribution of Soil Nutrients in a Northern Everglades Marsh: Water Conservation Area 2A W of P, N, C, and related physico-chemical parameters in the peat soils (Histosols) of Water Conservation

  19. An improved approach for measurement of coupled heat and water transfer in soil cells

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Laboratory experiments on coupled heat and water transfer in soil have been limited in their measurement approaches. Inadequate temperature control creates undesired two-dimensional distributions of both temperature and moisture. Destructive sampling to determine soil water content prevents measurem...

  20. 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.

  1. Wildfire Ash: Chemical Composition, Ash-Soil Interactions and Environmental Impacts

    NASA Astrophysics Data System (ADS)

    Brook, Anna; Hamzi, Seham; Wittenberg, Lea

    2015-04-01

    Of the five classical factors of soil formation, climate, parent material, topography, time, organisms, and recently recognized human activity, it is the latter factor which discretely includes fire and post-burn impact. However, it is considered that soil undergoing fire just experience a temporary removal of the top organic horizon, thus slightly modified and often labeled as 'temporarily disturbed' soil or soil 'under restoration/rehabilitation'. In fact the suggested seventh factor, post-burned produced ash, can act both dependently and independently of the other soil forming factors (Levin et al., 2013; Certini 2013). They are interdependent in cases where ash influences occur on time scales similar to 'natural' soil formation (Keesstra et ai., 2014) such as changes in vegetation. On the other hand, in post-fire areas a strong dependency is expected between soil-water retention mechanism, climate and topography. Wild-land fires exert many changes on the physical, chemical, mineralogical, biological, and morphological properties of soil that, in turn, affect the soil's hydrology and nutrient flux, modifying its ability to support vegetation and resist erosion. The ash produced by forest fires is a complex mixture composed of organic and inorganic particles characterized by vary physical-chemical and morphological properties. The importance of this study is straightforwardly related to the frequency and large-scales wildfires in Mediterranean region. In fact, wildfires are major environmental and land management concern in the world, where the number and severity of wildfires has increased during the past decades (Bodi, 2013). Certini (2013) assumed that cumulatively all of the vegetated land is burned in about 31 years annually affecting 330-430 Mha (over 3% of the Earth's surface) and wide range of land cover types worldwide including forests, peatlands, shrublands and grasslands. Whereas, the fire is identified as an important factor in soil formation, the 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

  2. Bimodal and multimodal descriptions of soil-water characteristic curves for structural soils.

    PubMed

    Liu, Shiyu; Yasufuku, Noriyuki; Liu, Qiang; Omine, Kiyoshi; Hemanta, Hazarika

    2013-01-01

    In the last decades several approaches have been developed to describe bimodal or multimodal soil-water characteristic curves (SWCCs). Unfortunately, most of these models were derived empirically. In the presented study, physically based bimodal and multimodal SWCC functions have been developed for structural soils. The model involved two or more continual pore series; the probability density functions for each pore series were assumed to be lognormal distribution and can be superposed to obtain the overall probability density function of the structural soils. The proposed functions were capable of simulating bimodal or multimodal SWCCs using parameters which can be related to physical properties of the structural soils. The experimental SWCC data were used to verify the proposed method. The fitting results showed that the proposed approaches resulted in good agreement between measurement and simulation. These functions can potentially be used as effective tools for indentifying hydraulic porosities in the structural mediums. PMID:23579828

  3. 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.

  4. 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.

  5. Interaction between humans and the physical world is com-plex. Topics such as water management, mineral depletion,

    E-print Network

    Saldin, Dilano

    , soil, plant or water samples · Design and monitor waste disposal sites · Plan and implement systems are hired to work in water quality assessment, groundwater monitoring, and lake or stream managementInteraction between humans and the physical world is com- plex. Topics such as water management

  6. 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.

  7. Interactive Effects of Soil Drainage and Time Since Burn on Transpiration of Boreal Black Spruce Forests

    NASA Astrophysics Data System (ADS)

    Angstmann, J. L.; Ewers, B. E.; Kwon, H.; Bond-Lamberty, B.; Amiro, B.; Gower, S. T.

    2006-12-01

    Boreal forests and their changing fire frequencies are of interest in global climate change because they comprise one-third of the world's forest coverage and store large amounts of carbon. Much of this carbon storage is due to peat formation in cold, poorly-drained boreal soils. Here, evapotranspiration plays a crucial role in the interaction between carbon and water cycles. The main objective of this study is to quantify the amount of water being released through transpiration as boreal forest stands recover from wildfires across well- to poorly-drained soil conditions. Species composition of this region of boreal forest changes during succession in well-drained soils from a mix of Picea mariana (black spruce), Pinus banksiana (jack pine), and Populus tremuloides (trembling aspen) in younger stands to being dominated solely by Picea mariana in older stands. Poorly-drained soils are dominated by Picea mariana throughout the chronosequence. Previous work in well-drained stands recovering from wildfires showed that in all but the oldest black spruce stands 1) tree transpiration changed dramatically with stand age due to sapwood-to-leaf area ratio dynamics and 2) minimum leaf water potential was kept constant to prevent excessive cavitation. Thus, we hypothesized that 1) minimum leaf water potential would be constant and 2) transpiration would be proportional to the sapwood-to- leaf area ratio across both stand age and soil drainage except for the two oldest black spruce stands. We tested these hypotheses by measuring leaf water potential (Psi) of 95 trees and sap flux from 111 trees. Mixed results were found in Picea mariana Psi between well- and poorly-drained areas of each stand age, with only the 17-year-old burn in July (average midday Psi of -0.77 and -1.08 MPa for well- and poorly drained respectively) and the 76-year-old burn in June (average predawn Psi of -0.52 and -0.42 MPa for well- and poorly drained respectively) differing significantly. Growing season averages of Psi for Picea mariana resulted in significantly different values of -0.29, -0.44, -0.42, -0.34 for pre-dawn and -1.09, -1.37, -1.20, -1.25 MPa for mid- day at the17-, 42-, 76-, and 156-year-old burns respectively. Our results show that stand age has more of an influence on black spruce water potentials and, likely, stand transpiration per unit leaf area than soil drainage. Thus, regional scale process models of boreal forest transpiration can be simplified with respect to soil drainage while retaining mechanistic rigor with respect to plant hydraulics.

  8. Interactions between soil fractions and PAH compounds in thermal desorption of contaminated soils

    SciTech Connect

    Mehrotra, A.K.; Svrcek, W.Y. [Univ. of Calgary, Alberta (Canada); Maguire, V. [Amoco Canada Petroleum Co., Ltd., Calgary (Canada)

    1996-12-31

    Results are reported for the interactions between three fractions of a soil, namely fulvic acid (FA), humic acid (HA) and humic/inorganic fractions, and three polynuclear aromatic hydrocarbons (PAHs). Prepared PAH+soil fraction mixtures, with 0.8-7.0 mass% PAH, were tested using a differential scanning calorimeter (DSC) over a temperature range of 20-390{degrees}C. The DSC results for the PAH+HA mixtures showed distinctly different characteristics than the other two soil fractions, where the endothermic peak for the vaporization of the PAH was absent. With the aid of flash calculations, the absence of the vaporization peak is interpreted to be due to the liquid-phase miscibility of the PAHs and the HA fraction. The miscible behavior of HA+PAHs implies that the temperature necessary for complete removal of a PAH would be higher than its boiling point temperature. 7 refs., 6 figs.

  9. Arsenic Enrichment in Surface Water and Soil in Tibetan Plateau

    NASA Astrophysics Data System (ADS)

    Li, S.; Wang, M.; Zheng, B.; Zheng, Y.

    2008-12-01

    Corresponding author: yan.zheng@qc.cuny.edu The average soil arsenic concentration was reported to be 18.7 mg/kg based on a survey of 205 samples in Tibet. This is considerably higher than the commonly cited crustal background value of 10 mg/kg of As for soil, and is unlikely due to anthropogenic pollution. To investigate the origin of this geochemical anomaly in soil arsenic, water (n=80), stream sediment (n=69), soil (n=79), rock (n=58) samples were collected from the Yarlung Zangbo (upstream of Brahmaputra) River drainage and Shiquan (upstream of Indus) River drainage basins in June of 2008. Arsenic enrichment is pronounced in the Shiquan River drainage. The average arsenic concentration in soil, stream sediment and stream water is 34±23 mg/kg (n=33, range <12-84 mg/kg), 35± mg/kg (n=37, range <14-197 mg/kg) and 5±69 g/L (n=39, range 2-252 g/L), respectively. In the Yarlung Zangbo River drainage, the average arsenic concentration in soil, stream sediment and stream water is 28±35 mg/kg (n=23, range <12-152 mg/kg), 22±7 mg/kg (n=28, range <14-44 mg/kg) and 11±16 g/L (n=30, range 2 -83 g/L), respectively. The average concentration of arsenic in upstream water of Yarlung Zangbo River is 38±28 g/L (n=5), and is much higher than the value of 5±3 g/L (n=23) downstream. The high background concentration of arsenic in soil of this area may be associated to the broad distribution of ophiolite melange and meta-sedimentary sequences containing shale, phyllite and schist that may be rich in arsenic. However, the maximum concentration of arsenic in rock is only 35±6mg/kg in metamorphic breccia. About 91% of the rock samples are lower than the limit of detection of XRF (15 mg/kg). Thus, it is more likely that soil As enrichment result from the weathering process of rocks under cold and arid plateau conditions. Whether this soil As anomaly in Tibetan Plateau affects the down stream flood plain sedimentary As content or not requires further study. Other types water sampled also show As enrichment. Two hot spring waters contain 5985 g/L and 3842 g/L arsenic. A dug well (about 2m depth) is found to contain 195 g/L As. The average arsenic concentration of salt lake water is 1947±3619 g/L (n=8, range 40-10626 g/L ), but a fresh water lake has only 21 g/L arsenic. Arsenic enrichment in water samples from the Shiquan River and the upstream of the Yarlung Zangbo River is not only associated with higher concentrations of arsenic in soils and rocks but also associated to the salt lake and hot spring in these drainages.

  10. 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.

  11. 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....

  12. 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...

  13. 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.

  14. 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.

  15. PLANT-SOIL INTERACTIONS AND THE CARBON CYCLE Integrating plant-soil interactions into global carbon cycle models

    Microsoft Academic Search

    Nicholas J. Ostle; Pete Smith; Rosie Fisher; F. Ian Woodward; Joshua B. Fisher; Jo U. Smith; David Galbraith; Peter Levy; Patrick Meir; Niall P. McNamara; Richard D. Bardgett

    2009-01-01

    Summary 1. Plant-soil interactions play a central role in the biogeochemical carbon (C), nitrogen (N) and hydrologicalcycles.Inthecontextof globalenvironmentalchange,theyareimportantbothinmod- ulating the impact of climate change and in regulating the feedback of greenhouse gas emissions (CO 2, CH 4and N 2O)tothe climate system. 2. Dynamic global vegetation models (DGVMs) represent the most advanced tools available to predict the impacts of global change

  16. 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...

  17. Monitoring near surface soil water and associated dynamics of infiltration and evaporation fluxes

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In-situ monitoring of soil water has the advantage of integrating the precipitation, evaporation history, and gradual changes in hydraulic properties on the aggregate response of the system, which is manifested as soil water storage. Near-surface soil water and temperature dynamics were monitored th...

  18. Surfactant Effects on the Water-stable Aggregation of Wettable and Nonwettable Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surfactants may affect soil structure differently, depending upon a soil’s wettability or the quality of rainfall or irrigation water. This study evaluated the effects of two nonionic surfactants and a surfactant-free water control on the water drop penetration time (WDPT) and mean weight diameter ...

  19. Water distribution in the top 1 m of the earth's surface soil layer

    E-print Network

    Hubbard, Susan

    Water distribution in the top 1 m of the earth's surface soil layer often controls the success near-sur- face soil water content distribution and flux. Our research focuses on investigation of agri- cultural crops. In this near-sur- face zone, large spatial and temporal variations in soil water

  20. 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...

  1. Seasonal soil water storage changes beneath central Amazonian rainforest and pasture

    Microsoft Academic Search

    M. G. Hodnett; L. Pimentel da Silva; H. R. da Rocha; R. Cruz Senna

    1995-01-01

    Evaporation and infiltration were compared for tropical rainforest and pasture, near to Manaus, Brazil from October 1990 to February 1992 using measurements of soil water storage over a depth of 2 m. The soil is a clayey oxisol of low water available capacity. In both of the dry seasons studied, the maximum change in soil water storage in the forest

  2. 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...

  3. ASSESSMENT OF ADOPTION BEHAVIOR OF SOIL AND WATER CONSERVATION PRACTICES IN THE KOGA WATERSHED, HIGHLANDS OF

    E-print Network

    Walter, M.Todd

    ASSESSMENT OF ADOPTION BEHAVIOR OF SOIL AND WATER CONSERVATION PRACTICES IN THE KOGA WATERSHED Ethiopia. Even though a number of soil and water conservation methods were introduced to combat land' views on land degradation and to assess their adoption behavior of soil and water conservation knowledge

  4. Soil water sensing methods-Usefulness for evapotranspiration monitoring and links to remote sensing

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water sensing methods are widely used to characterize the rhizosphere 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 with minimal error. One such is the ne...

  5. 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...

  6. Aspect influences on soil water retention and storage I. J. Geroy,1

    E-print Network

    Marshall, Hans-Peter

    aspect retain as much as 25% more water at any given soil water pressure than samples from the south methods are commonly used to describe the distribution of soil moisture (Famiglietti et al., 1998; GraysonAspect influences on soil water retention and storage I. J. Geroy,1 M. M. Gribb,2 H. P. Marshall,3

  7. Bridging From Ecology to Hydrology and Soil Science Through Ecohydrology and Hydropedology: The Fundamental Role of Woody Plant Patterns on Heterogeneity in Soil Water and Carbon

    NASA Astrophysics Data System (ADS)

    Breshears, D. D.; Zou, C. B.

    2006-12-01

    Environmental scientists are facing a key challenge: to improve our ability to predict how fundamental attributes of mass and energy transport in the near-surface environment respond to land use and climate variation and change. These challenges have resulted in increased recognition of the importance of spatial heterogeneity and feedbacks and of the need for increased interdisciplinary interactions to address the challenges. Consequently, two interdisciplinary areas have been developing: hydropedology, focused on linking hydrology and soil science, and ecohydrology focused on linking ecology and hydrology. Ecohydrology and hydropedology are, of course, interrelated with one another, but frameworks outlining key linkages are still lacking. One important linkage between theses emerging areas is related to gradients of woody plants. Much of the terrestrial biosphere can be viewed as a gradient from grasslands with no woody plants to forests with nearly complete coverage by woody plants, referred to here and elsewhere as the grassland-forest continuum. Woody plants modify key attributes of the above- and below-ground microclimate around them and associated attributes of soil water and carbon. Here I summarize recent findings related to woody plant effects on vertical and horizontal heterogeneity in soil water and carbon patterns. Soil water content and soil carbon vary vertically with soil depth and depend strongly on woody plant canopy coverage. Consequently, advances in hydropedology and ecohydrology will need to more fully account for the effects of woody plants on soil water and carbon help produce much of the are underlie many of the fundamental role of woody plant patterns on heterogeneity in soil water and carbon.

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

    E-print Network

    Cohen, Ronald C.

    in the soil carbon pool may significantly affect the global carbon cycle and climate system. Soil respiration may accelerate global warming by acting as a positive feed- back in the global carbon cycle (Jenkinson

  9. Sorption of nonionic organic compounds in soil-water systems containing a micelle-forming surfactant

    SciTech Connect

    Sun, S.; Inskeep, W.P.; Boyd, S.A. [Montana State Univ., Bozeman, MT (United States). Dept. of Plant, Soil and Environmental Science; [Michigan State Univ., East Lansing, MI (United States). Dept. of Crop and Soil Science

    1994-12-31

    The solubility enhancement of nonionic organic compounds (NOCs) by surfactants may represent an important tool in chemical and biological remediation of contaminated soils. In aqueous systems, the presence of dissolved surfactant emulsions or micelles may enhance the solubility of NOCs by acting as a hydrophobic partitioning phase for the NOCs. However, most environmental remediation efforts involve soil-water or sediment-water systems, where surfactant molecules may also interact with the solid phase. An understanding of the effect of surfactants on the sorption and distribution of NOCs in soil or sediment environments will provide an essential basis for utilizing surfactants in environmental remediation. In this study, the authors examined the effect of a micelle-forming surfactant (Triton X-100) on the sorption of 2,2{prime},4,4{prime},5,5{prime}-PCB, 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (p,p{prime}-DDT) and 1,2,4-trichlorobenzene (1,2,4-TCB). A conceptual model, which accurately describes the functional dependence of K* on Triton X-100 concentration, was developed based on the partition coefficients of these NOCs by soil, soil-surfactant, surfactant monomer and surfactant micelle phases. This model can be further modified to provide quantitative prediction of K* of a given NOC at different surfactant concentrations.

  10. Interactions between physical and biotic factors influence CO2 flux in Antarctic dry valley soils

    E-print Network

    Wall, Diana

    Interactions between physical and biotic factors influence CO2 flux in Antarctic dry valley soils and physical controls over carbon (C) balance. In the McMurdo Dry Valleys of Antarctica, soil CO2 fluxes in dry valley soils is driven primarily by physical factors such as soil temperature and moisture

  11. Root controls on water redistribution and carbon uptake in the soil-plant system under current and future climate

    NASA Astrophysics Data System (ADS)

    Volpe, V.; Marani, M.; Albertson, J. D.; Katul, G.

    2013-10-01

    Understanding photosynthesis and plant water management as a coupled process remains an open scientific problem. Current eco-hydrologic models characteristically describe plant photosynthetic and hydraulic processes through ad hoc empirical parameterizations with no explicit accounting for the main pathways over which carbon and water uptake interact. Here, a soil-plant-atmosphere continuum model is proposed that mechanistically couples photosynthesis and transpiration rates, including the main leaf physiological controls exerted by stomata. The proposed approach links the soil-to-leaf hydraulic transport to stomatal regulation, and closes the coupled photosynthesis-transpiration problem by maximizing leaf carbon gain subject to a water loss constraint. The approach is evaluated against field data from a grass site and is shown to reproduce the main features of soil moisture dynamics and hydraulic redistribution. In particular, it is shown that the differential soil drying produced by diurnal root water uptake drives a significant upward redistribution of moisture both through a conventional Darcian flow and through the root system, consistent with observations. In a numerical soil drying experiment, it is demonstrated that more than 50% of diurnal transpiration is supplied by nocturnal upward water redistribution, and some 12% is provided directly through root hydraulic redistribution. For a prescribed leaf area density, the model is then used to diagnose how elevated atmospheric CO2 concentration and increased air temperature jointly impact soil moisture, transpiration, photosynthesis, and whole-plant water use efficiency, along with compensatory mechanisms such as hydraulic lift using several canonical forms of root-density distribution.

  12. Environmental chemistry of ethylene dibromide in soil and ground water.

    PubMed

    Pignatello, J J; Cohen, S Z

    1990-01-01

    Ethylene dibromide is a ground water pollutant principally as a result of its use as a soil pesticide and secondarily from spills or leaks of leaded gasoline in which it is an additive. The compound has been found in over 1900 wells in 4 countries: Japan, Israel, Australia, and the United States (10 states), typically at concentrations of 0.04-4 micrograms/L. The overall rate of detections in suspected areas is about 13%. Its use as a soil fumigant was banned in the US in 1983 because of its carcinogenicity. Concern over gasoline as a source should diminish as leaded fuels all but disappear from the market in many countries. The voluminous research and regulatory attention devoted to EDB has generated a picture, if not an entirely clear one, of how EDB behaves in the environment and what we can expect for the future. EDB is volatile, moderately water soluble, and has only weak equilibrium sorptive affinity for soil. Transport to ground water occurs by both vapor-phase diffusion and by advection with infiltrating water, depending on soil properties and precipitation and irrigation patterns. Models describing these processes have been developed and validated in part by laboratory experiments, but the complexity and heterogeneity of the field makes predictions difficult there. As with other pesticides, experience indicates that areas with permeable soils and shallow water tables are most vulnerable. However, EDB seems to have penetrated many tens of meters of unsaturated zone in some cases to reach the water table. Transport in ground water occurs with bulk water flow, subject to hydrodynamic dispersion effects common to all solutes, and subject to sorptive retardation. From equilibrium sorption partition coefficients, plume migration is likely to be a factor of 2-4 slower than bulk water flow. Hydrolysis is the most important abiotic reaction. The reaction is independent of pH in the range 4-9 and is probably uncatalyzed by particle surfaces. Both SN1 and SN2 mechanisms have been proposed. Estimates of the half-life range from 2-4 yr at 22-25 degrees C, to around two decades at 10 degrees C. These temperatures approximate subsurface conditions in warm climates (e.g., Florida) and temperate climates (e.g., New England), respectively. The major products are ethylene glycol and bromide ion. Both are of little concern at low concentrations. Vinyl bromide, which is a suspected carcinogen, is a minor product in lab studies, but so far there are no reports linking its presence with EDB in the field.(ABSTRACT TRUNCATED AT 400 WORDS) PMID:2405457

  13. Hydroclimatology of Illinois: A comparison of monthly evaporation estimates based on atmospheric water balance and soil water balance

    Microsoft Academic Search

    Pat Jen-Feng Yeh; Michelle Irizarry; Elfatih A. B. Eltahir

    1998-01-01

    Here we describe the regional-scale hydrological cycle of Illinois, including both the land and atmospheric branches, using a data set on most of the hydrological variables, i.e., precipitation, streamflow, soil water content, snow depth, groundwater level, and atmospheric flux of water vapor. Since direct observations of evaporation are not available, two different approaches, soil water balance and atmospheric water balance,

  14. [Effect of reclaimed water irrigation on soil properties and vertical distribution of heavy metal].

    PubMed

    Zhao, Zong-Ming; Chen, Wei-Ping; Jiao, Wen-Tao; Wang, Mei-E

    2012-12-01

    Utilization of reclaimed water is one of the important methods to alleviate water shortage. The effect of reclaimed water irrigation on soil is always a concern. To understand the effect of long time reclaimed water irrigation on soil, typical farmland irrigated with reused water was selected. Soil properties and heavy metal concentration of soil and water samples were analyzed to identify the effect of the irrigation on heavy metal vertical distribution and organic matter content, total carbon, total nitrogen and pH value in soil. The results show that heavy metal contents of irrigation water used in Liangshuihe farmland are 2.5 to 10.5 times higher than that of Beiyechang farmland, and reclaimed water irrigation could cause changes of soil properties that soil organic matter content, total carbon, total nitrogen were increased and pH values were reduced. Based on the field investigation results, the soil nutrient conditions benefit from irrigate reclaimed water, however, the accumulation of heavy metal in soil could raise the risk. As a source of soil heavy metal, reclaimed water irrigation could make differences on the accumulation and mobility of soil heavy metal. Also the distribution and mobility of soil heavy metal are influenced by soil organic matter content and there are more heavy metal were taken up by plants or transferred to the deeper area in Liangshuihe farmland. PMID:23379128

  15. The Soil Stack: An Interactive Computer Program Describing Basic Soil Science and Soil Degradation.

    ERIC Educational Resources Information Center

    Cattle, S. R.; And Others

    1995-01-01

    A computer program dealing with numerous aspects of soil degradation has a target audience of high school and university students (16-20 year olds), and is presented in a series of cards grouped together as stacks. Describes use of the software in Australia. (LZ)

  16. Scale-dependent soil and climate variability effects on watershed water balance of the SWAT model

    Microsoft Academic Search

    Ranjan S. Muttiah; Ralph A. Wurbs

    2002-01-01

    The water balance of large watersheds in Texas was studied using a process level watershed model called the soil and water assessment tool (SWAT). The major components of the SWAT watershed model are evapo-transpiration (ET), soil water storage (SW), and water yield (WYLD), which is the sum of surface runoff and subsurface flow. Important input variables controlling the water balance

  17. 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.

  18. 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.

  19. The impact of soil moisture variability on seasonal convective precipitation simulations via the soil-boundary layer interaction.

    NASA Astrophysics Data System (ADS)

    Khodayar, S.; Kalthoff, N.; Schädler, G.

    2012-04-01

    It is known that besides forcing by synoptic-scale processes, the boundary layer conditions often play a key role for the initiation of convective precipitation. The evolution and conditions of the boundary layer depend considerably on the transformation of the available energy at the Earth's surface into sensible and latent heat fluxes. The soil moisture (SM), besides other factors such as the vegetation coverage, land use and soil type, is one of the main factors governing this energy transformation. Additionally, the availability of humidity in the atmosphere is controlled by a number of processes including land surface processes, which in turn are strongly influenced by spatially variable fields of SM. Thus, an accurate specification of the SM distribution is a critical requirement in the representation of land and surface processes in forecast and climate models. Moreover, soil-atmosphere interactions, in particular, the SM-precipitation feedback, are highly relevant for numerical weather prediction and seasonal forecasting. Despite being a long-standing topic in research, different studies present inconclusive results showing some evidence for positive, negative, and no feedbacks depending on region and investigated period, model characteristics and resolution. Reliable data sets for validation or initialization of model simulations are frequently not at one's disposal; especially the SM is currently one of the least assessed quantities with almost no data from operational monitoring networks available. In summer 2007, the field campaign 'Convective and Orographically-induced Precipitation Study' (COPS) was performed in south-western Germany and eastern France. During COPS an innovative measurement approach using a very high number of different SM sensors was introduced. Each station was equipped with sensors at three different depths (5, 20 and 50cm) simultaneously measuring SM and soil temperature. The COPS data set, which provided suitable observations for model validation, in combination with seasonal climate simulations with the Consortium for Small-Scale modelling (COSMO) model in his climate version (CCLM) were used to investigate the seasonal climatology of the investigation area, as well as the interactions between the soil and the atmosphere in the complex orographic region of western Germany and eastern France. The impact of realistic model initialization with SM measurements from COPS on convective precipitation will be discussed. Additionally, the impact of the prescribed soil type distribution on seasonal climate simulations will be demonstrated. The combination of dense observations with CCLM simulations permitted a rigorous analysis of the water transfer process chain from SM and fluxes to convective initiation and precipitation.

  20. 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.

  1. 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 in Florida (FL) have acted as a sink for carbon (C) over the last 40 years. · Climate interacting with land

  2. Pipe-soil shear interaction stiffness in horizontal directional drilling and pipe bursting

    Microsoft Academic Search

    Abdul Ghafar Chehab; Ian Moore

    2010-01-01

    During horizontal directional drilling and pipe bursting installations, the shear forces between the pipe and the surrounding soil play a major role in the tensile loads and stresses experienced by the pipe. The magnitudes and variations in the shear forces are controlled by the pipe-soil interaction characteristics. This paper discusses the shear interaction between the pipe and the soil during

  3. Determination of water absorption and water holding capacities of different soil mixtures with MINIDRAIN system to enhance the plant growth

    NASA Astrophysics Data System (ADS)

    Sudan Acharya, Madhu; Rauchecker, Markus; Wu, Wei

    2014-05-01

    Soil water holding capacity is the amount of water that a given soil can hold against the force of gravity. Soil texture and organic matter are the key components that determine soil water holding capacity. Soils with smaller particle sizes, such as silt and clay have larger surface area can hold more water compared to sand which has large particle sizes which results in smaller surface area. A study report showed that 1% increase in soil humus will result in a 4% increase in stored soil water (Morris, 2004) and 1 part humus holds 4 parts of water (Wheeler and Ward, 1998). Therefore, the more humus that can be added to the soil, the greater the water holding capacity of the soil. As the level of organic matter increases in a soil, the water holding capacity also increases due to the affinity of organic matter for water. The water holding capacity of the soil is determined by the amount of water held in the soil sample vs. the dry weight of the sample. MINIDRAIN is a patented system made of geo-fabric (fleece) or combination of geosynthetics and humus. MINIDRAIN and vegetation nets developed by the company ÖKO-TEX (Linz, Austria) will improve the distribution of water and air in the soils, increase the growth of vegetation and reduce the soil erosion. Depending on the physical configuration, there are four different combinations of MINIDRAIN systems developed by ÖKO-TEX. a) Geotextile (fleece) strips of different sizes (e.g. 5x10x250 mm) b) Net formed strips (drainage nets) of different sizes c) Multilayer geotextile mats with humus, seeds or compost of different sizes (e.g. 10x30x200 mm) d) Multilayer geotextile net formed mats with humus, seeds or compost This paper describes the experimental results of the water absorption and water holding capacity of different forms of MINIDRAIN under different soil mixes. In this experiment, potting soil, coarse sand and LECA (Light weight clay aggregates) balls are mixed with different proportion of MINIDRAIN systems and the water absorption and water holding capacities are measured. A comparison of the results for an optimal combination of soil and MINIDRAIN system has also been made. The results show that, the soil mix with MINIDRAIN system with multilayer mats (with humus) have highest water absorption and water holding capacity among the tested soil mix combinations.

  4. Sensor-based soil water monitoring to more effectively manage agricultural water resources in coastal plain soils

    NASA Astrophysics Data System (ADS)

    Bellamy, Christopher A.

    Cotton (Gossypium hirsutum L.) is widely grown in the United States with 5.7 million ha grown nationally and 1.2 million ha grown in the humid southeastern states in 2005. From 1969 to 2003, agricultural irrigated farmland acreage and total water applied increased by over 40% and 11% respectively to include a total of 55.3 million acres in 2002. Combined with recent and more frequent drought periods and legal water conflicts between states, there has been an increased interest in more effective southeastern water management, thus making the need to develop improved irrigation scheduling methods and enhanced water use efficiency of cotton cultivars. Several irrigation scheduling methods (soil moisture monitoring, pan evaporation, and climate based) tested at Clemson and elsewhere have shown that sensor-based irrigation significantly increased cotton yields and provided a monetary savings compared to other methods. There is however limited information on capacitance based soil moisture analysis techniques in the southeastern coastal plain soils and also limited locally developed crop coefficients used in scheduling the ET based treatments. The first objective of this study was to determine and improve the feasibility of utilizing sensor-based soil water monitoring techniques in Southeastern Coastal Plain soils to more effectively manage irrigation and increase water use efficiency of several cotton cultivars. The second objective was to develop two weighing lysimeters equipped with wireless data acquisition system to determine a crop coefficient for cotton under southeastern humid conditions. Two multi-sensor capacitance probes, AquaSpy(TM) and Sentek EnviroSCAN RTM, were calibrated in this study. It was found that positive linear calibrations can be used to describe the relationship between the soil volumetric moisture content (VMC) and sensor readings found for both probes and that multi-sensor capacitance probes can be used to accurately measure volumetric soil moisture contents, if installed and calibrated properly. It was determined that a direct installation method should be used rather than a slurry mix method. The slurry method was found to overestimate the VMC in sandy soils. There were good correlations between In Season Estimated Yield (INSEY) as measured by the plant Normalized Difference Vegetation Index (NDVI) and the VMC of the soil. Results showed that when separated by irrigation regime, the relationship between INSEY and VMC follows good linear correlations. This was due to the health of the plant and its dependency on soil moisture. There were strong correlations between irrigation depths applied and seed cotton yields. Highest water use efficiency values were 0.55 kg seed cotton/m3 water applied in 2008 (0.55 kg seed cotton/m 3 ET) and 0.788 kg/m3 water applied (0.66 kg/m 3 ET) in 2009. Two weighing lysimeters were constructed to provide cotton and reference ET measurements. Evaporation pan and weather data from a local station were also used to provide a basis for calculating ET. Because the Penman-Monteith (P-M) method is widely known and trusted, a set of crop coefficients were developed based on P-M and cotton lysimeter data and determined to be 0.91, 1.24, and 0.72 for the initial, mid, and end stages for a Delta Pine 0949 BSRF cultivar.

  5. EFFECTS OF WATER RECIRCULATION ON WATER QUALITY AND BOTTOM SOIL IN AQUACULTURE PONDS

    Microsoft Academic Search

    Oscar Zelaya; Claude E. Boyd; David R. Teichert-Coddington; Bartholomew W. Green

    There is considerable interest in reducing negative environmental impacts of shrimp and fish farming. One of the most promising methods for reducing the environmental effects of pond aquaculture is to use water-recirculating systems to minimize effluents. However, few studies have been performed to evaluate the effect of recirculation upon soil and water quality in ponds. This study evaluates changes in

  6. Soil water dynamics, transpiration, and water losses in a crested wheatgrass and native shortgrass ecosystem

    Microsoft Academic Search

    M. J. Trlica; M. E. Biondini

    1990-01-01

    The status of water in soil and vegetation was monitored in a stand of crested wheatgrass (Agropyron cristatum) and a nearby shortgrass steppe during a growing season. This was done to determine if water use and losses were similar among two very different communities in a similar climate. Precipitation was similar throughout the study period for both the crested wheatgrass

  7. Manure Phosphorus and Surface Water Protection I: Basic Concepts of Soil and Water P

    NSDL National Science Digital Library

    This lesson focuses on the process of eutrophication; the relationship between land application of manure and soil phosphorus (P) dynamics on P delivery to surface waters; and on the P dynamics in water bodies that result in increased P available to aquatic vegetation.

  8. 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...

  9. Soil water content and water supply of plants in the southern Crimea

    NASA Astrophysics Data System (ADS)

    Sudnitsyn, I. I.

    2008-01-01

    In cinnamonic soils of the Nikitsky Botanical Garden (Crimea), the average productive water reserves (WR) under different plants in 1981-1990 exhibited close correlation with the field water capacity (FC) and the productive moisture range, which is equal to the difference between the FC and the permanent wilting point (WP). The soil water content (SWC) regularly increased with the depth. An 8-year-long variation cycle of the meteorological conditions and the WR was revealed. A correlation between the WR and the precipitation was noted. The relationship of the occurrence frequencies of the FC and WR with their values was analogous to the Maxwell distribution close to the normal (Gaussian) distribution.

  10. 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.

  11. Tracking water pathways in steep hillslopes by ?18O depth profiles of soil water

    NASA Astrophysics Data System (ADS)

    Mueller, Matthias H.; Alaoui, Abdallah; Kuells, Christoph; Leistert, Hannes; Meusburger, Katrin; Stumpp, Christine; Weiler, Markus; Alewell, Christine

    2014-11-01

    Assessing temporal variations in soil water flow is important, especially at the hillslope scale, to identify mechanisms of runoff and flood generation and pathways for nutrients and pollutants in soils. While surface processes are well considered and parameterized, the assessment of subsurface processes at the hillslope scale is still challenging since measurement of hydrological pathways is connected to high efforts in time, money and personnel work. The latter might not even be possible in alpine environments with harsh winter processes. Soil water stable isotope profiles may offer a time-integrating fingerprint of subsurface water pathways. In this study, we investigated the suitability of soil water stable isotope (?18O) depth profiles to identify water flow paths along two transects of steep subalpine hillslopes in the Swiss Alps. We applied a one-dimensional advection-dispersion model using ?18O values of precipitation (ranging from -24.7 to -2.9‰) as input data to simulate the ?18O profiles of soil water. The variability of ?18O values with depth within each soil profile and a comparison of the simulated and measured ?18O profiles were used to infer information about subsurface hydrological pathways. The temporal pattern of ?18O in precipitation was found in several profiles, ranging from -14.5 to -4.0‰. This suggests that vertical percolation plays an important role even at slope angles of up to 46°. Lateral subsurface flow and/or mixing of soil water at lower slope angles might occur in deeper soil layers and at sites near a small stream. The difference between several observed and simulated ?18O profiles revealed spatially highly variable infiltration patterns during the snowmelt periods: The ?18O value of snow (-17.7 ± 1.9‰) was absent in several measured ?18O profiles but present in the respective simulated ?18O profiles. This indicated overland flow and/or preferential flow through the soil profile during the melt period. The applied methods proved to be a fast and promising tool to obtain time-integrated information on soil water flow paths at the hillslope scale in steep subalpine slopes.

  12. The impact of soil freezing\\/thawing processes on water and energy balances

    Microsoft Academic Search

    Xia Zhang; Shufen Sun

    2011-01-01

    A frozen soil parameterization coupling of thermal and hydrological processes is used to investigate how frozen soil processes\\u000a affect water and energy balances in seasonal frozen soil. Simulation results of soil liquid water content and temperature\\u000a using soil model with and without the inclusion of freezing and thawing processes are evaluated against observations at the\\u000a Rosemount field station. By comparing

  13. 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.

  14. 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.

  15. 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.

  16. 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.

  17. 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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. Testing a full-range soil-water retention function in modeling water potential and temperature

    USGS Publications Warehouse

    Andraski, B.J.; Jacobson, E.A.

    2000-01-01

    Recent work has emphasized development of full-range water-retention functions that are applicable under both wet and dry soil conditions, but evaluation of such functions in numerical modeling has been limited. Here we show that simulations using the Rossi-Nimmo (RN) full-range function compared favorably with those using the common Brooks-Corey function and that the RN function can improve prediction of water potentials in near-surface soil, particularly under dry conditions. Simulations using the RN function also improved prediction of temperatures throughout the soil profile. Such improvements could be important for calculations of liquid and vapor flow in near-surface soils and in deep unsaturated zones of arid and semiarid regions.

  3. 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).

  4. Anion?exchange membrane, water, and sodium bicarbonate extractions as soil tests for phosphorus

    Microsoft Academic Search

    J. J. Schoenau; W. Z. Huang

    1991-01-01

    Three techniques were evaluated as soil P tests for western Canadian soils: anion?exchange membrane (AEM), water, and bicarbonate extraction. The AEM, water, and bicarbonate?extractable total P represented novel approaches to compare to the widely used bicarbonate?extractable inorganic P (traditional Olsen) soil test. In a range of Saskatchewan soils, similar trends in predicted relative P availability were observed for AEM, water

  5. Soil water distribution, uniformity and water-use efficiency under alternate furrow irrigation in arid areas

    Microsoft Academic Search

    S. Z. Kang; P. Shi; Y. H. Pan; Z. S. Liang; X. T. Hu; J. Zhang

    2000-01-01

    Soil water distribution, irrigation water advance and uniformity, yield production and water-use efficiency (WUE) were tested\\u000a with a new irrigation method for irrigated maize in an arid area with seasonal rainfall of 77.5–88.0?mm for 2?years (1997\\u000a and 1998). Irrigation was applied through furrows in three ways: alternate furrow irrigation (AFI), fixed furrow irrigation\\u000a (FFI) and conventional furrow irrigation (CFI). AFI

  6. 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.

  7. [Simulation of effect of irrigation with reclaimed water on soil water-salt movement by ENVIRO-GRO model].

    PubMed

    Lü, Si-Dan; Chen, Wei-Ping; Wang, Mei-E

    2012-12-01

    As the conflict between water supply and demand, wastewater reuse has become an important measure, which can relieve the water shortage in Beijing. In order to promote safe irrigation with reclaimed water and prevent soil salinisation, the dynamic transport of salts in urban soils of Beijing, a city of water shortage, under irrigation of reclaimed water was simulated by ENVIRO-GRO model in this research. The accumulation trends of soil salinity were predicted. Simultaneously, it investigated the effects of different irrigation practices on soil water-salt movement and salt accumulation. Results indicated that annual averages of soil salinity (EC(e)) increased 29.5%, 97.2%, 197.8% respectively, with the higher irrigation, normal irrigation, and low irrigation under equilibrium conditions. Irrigation frequency had little effect on soil salt-water movement, and soil salt accumulation was in a downward trend with low frequency of irrigation. Under equilibrium conditions, annual averages of EC(e) increased 23.7%, 97.2%, 208.5% respectively, with irrigation water salinity (EC(w)) 0.6, 1.2, 2.4 dS x m(-1). Soil salinity increased slightly with EC(w) = 0.6 dS x m(-1), while soil salinization did not appear. Totally, the growth of Blue grass was not influenced by soil salinity under equilibrium conditions with the regular irrigation in Beijing, but mild soil salinization appeared. PMID:23379129

  8. Water Repellency Effects on Water Retention in Heat Pre-treated Volcanic Ash Soil

    NASA Astrophysics Data System (ADS)

    Chhoden, T.; Karunarathna, A.; Kawamoto, K.; Komatsu, T.; Moldrup, P.

    2009-12-01

    Water repellency (WR) in soil is a common phenomenon after forest fires all over the world. It can induce hydrological problems such as preferential flow in soils and reduced water infiltration rate which in turn can lead to surface runoff and erosion. In this study, we examined the hydrophobicity for pre-heated volcanic ash soil samples with different temperatures between 60 and 200oC and non pre-heated samples (20oC) from a single surface soil profile down to 25 cm depth. Moreover, the pre-heated samples were used to investigate the effects of pre-heat treatment and hydrophobic severity on soil-water retention properties. We first assessed the degree of water repellency for pre-heated samples by the Water Droplet Penetration Time test and Molarity of Ethanol Droplet test and categorized the water repellency into four different classes (extremely, severely, strongly and non-WR) as proposed by Bisdom et al. (1993). The depth profiles of soil organic carbon (SOC) content for the pre-heated samples were also measured. Results showed the categorized WR classes changed depending on pre-heated temperatures and residual SOC contents. For top surface soil with 0-5cm depth, pre-heated samples at 105, 125, 150 and 175oC exhibited extremely WR, pre-heated samples at 60oC exhibited severely WR, non pre-heated samples (20oC) exhibited strongly WR, and pre-heated samples at 200oC exhibited non-WR. Moreover, the threshold value of SOC above which WR occurs was found to be around 7.4% based on the measured WR classes and SOC profiles. The water supply/drainage controlled hanging column setup equipped with a newly-developed mini tensiometer-TDR coil probe (5 cm in length and 0.5 cm in diameter) was used to measure wetting and drying processes of the soil-water retention curves (SWRCs) for the pre-heated samples. Results showed that the SWRCs on the wetting process were highly affected by the degree of water repellency. Clear water-entry pressures (hwe) were observed in the SWRCs for the preheated samples categorized as extremely and severely WR and the measured hwe values were between -1.5 and 2 cm H2O.

  9. 3D finite element analysis on pile-soil interaction of passive pile group

    Microsoft Academic Search

    Ming-hua Zhao; Dun-ping Liu; Ling Zhang; Chong Jiang

    2008-01-01

    The interaction between pile and soft soil of the passive pile group subjected to soil movement was analyzed with three-dimensional\\u000a finite element model by using ANSYS software. The soil was assumed to be elastic-plastic complying with the Drucker-Prager\\u000a yield criterion in the analysis. The large displacement of soil was considered and contact elements were used to evaluate\\u000a the interaction between

  10. Clustered Distribution of Tree Roots and Soil Water Exploitation

    Microsoft Academic Search

    M. Kazda; I. Schmid

    A substantial number of experiments have shown root proliferation and concentration in nutrient-rich patches. This article\\u000a focuses on root clustering observed on tree roots in forest stands and water uptake within these zones. Root clustering is\\u000a seen as a rule in natural soils for optimized exploitation of aggregated resources. In summary, root distribution in nature\\u000a is caused by two factors:

  11. Interactions between plant nutrients, water and carbon dioxide as factors limiting crop yields

    PubMed Central

    Gregory, P. J.; Simmonds, L. P.; Warren, G. P.

    1997-01-01

    Biomass production of annual crops is often directly proportional to the amounts of radiation intercepted, water transpired and nutrients taken up. In many places the amount of rainfall during the period of rapid crop growth is less than the potential rate of evaporation, so that depletion of stored soil water is commonplace. The rate of mineralization of nitrogen (N) from organic matter and the processes of nutrient loss are closely related to the availability of soil water. Results from Kenya indicate the rapid changes in nitrate availability following rain.
    Nutrient supply has a large effect on the quantity of radiation intercepted and hence, biomass production. There is considerable scope for encouraging canopy expansion to conserve water by reducing evaporation from the soil surface in environments where it is frequently rewetted, and where the unsaturated hydraulic conductivity of the soil is sufficient to supply water at the energy limited rate (e.g. northern Syria). In regions with high evaporative demand and coarse-textured soils (e.g. Niger), transpiration may be increased by management techniques that reduce drainage.
    Increases in atmospheric [CO2] are likely to have only a small impact on crop yields when allowance is made for the interacting effects of temperature, and water and nutrient supply.

  12. 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

  13. Water and heat transport in hilly red soil of southern China: I. Experiment and analysis*

    PubMed Central

    Lu, Jun; Huang, Zhi-zhen; Han, Xiao-fei

    2005-01-01

    Studies on coupled transfer of soil moisture and heat have been widely carried out for decades. However, little work has been done on red soils, widespread in southern China. The simultaneous transfer of soil moisture and heat depends on soil physical properties and the climate conditions. Red soil is heavy clay and high content of free iron and aluminum oxide. The climate conditions are characterized by the clear four seasons and the serious seasonal drought. The great annual and diurnal air temperature differences result in significant fluctuation in soil temperature in top layer. The closed and evaporating columns experiments with red soil were conducted to simulate the coupled transfer of soil water and heat under the overlaying and opening fields’ conditions, and to analyze the effects of soil temperature gradient on the water transfer and the effects of initial soil water contents on the transfer of soil water and heat. The closed and evaporating columns were designed similarly with about 18 °C temperatures differences between the top and bottom boundary, except of the upper end closed or exposed to the air, respectively. Results showed that in the closed column, water moved towards the cold end driven by temperature gradient, while the transported water decreased with the increasing initial soil water content until the initial soil water content reached to field capacity equivalent, when almost no changes for the soil moisture profile. In the evaporating column, the net transport of soil water was simultaneously driven by evaporation and temperature gradients, and the drier soil was more influenced by temperature gradient than by evaporation. In drier soil, it took a longer time for the temperature to reach equilibrium, because of more net amount of transported water. PMID:15822143

  14. 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.

  15. 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.

  16. [Simulation of effects of soil properties and plants on soil water-salt movement with reclaimed water irrigation by ENVIRO-GRO model].

    PubMed

    Lü, Si-Dan; Chen, Wei-Ping; Wang, Mei-E

    2012-12-01

    In order to promote safe irrigation with reclaimed water and prevent soil salinisation, the dynamic transport of salts in urban soils of Beijing under irrigation of reclaimed water was simulated by ENVIRO-GRO model in this study. The accumulation trends and profile distribution of soil salinity were predicted. Simultaneously, the effects of different soil properties and plants on soil water-salt movement and salt accumulation were investigated. Results indicated that soil salinity in the profiles reached uniform equilibrium conditions by repeated simulation, with different initial soil salinity. Under the conditions of loam and clay loam soil, salinity in the profiles increased over time until reaching equilibrium conditions, while under the condition of sandy loam soil, salinity in the profiles decreased over time until reaching equilibrium conditions. The saturated soil salinity (EC(e)) under equilibrium conditions followed an order of sandy loam < loam < clay loam. Salt accumulations in Japan euonymus and Chinese pine were less than that in Blue grass. The temporal and spatial distributions of soil salinity were also different in these three types of plants. In addition, the growth of the plants was not influenced by soil salinity (except clay loam), but mild soil salinization occurred under all conditions (except sandy loam). PMID:23379130

  17. 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.

  18. Soil and Water Assessment Tool Theoretical Documentation Version 2009

    E-print Network

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

    3:1.4 DENITRIFICATION 194 3:1.5 ATMOSPHERIC DEPOSITION 195 NITROGEN IN RAINFALL 196 NITROGEN DRY DEPOSITION 197 3:1.6 FIXATION 198 3:1.7 UPWARD MOVEMENT OF NITRATE IN WATER 198 3:1.8 LEACHING 198 3:1.9... i (mm H2O), w se e p is the amount of water entering the vadose zone from the soil profile on day i (mm H2O), and Q g w is the amount of return flow on day i (mm H2O). The subdivision of the watershed enables the model to reflect differences...

  19. 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.

  20. 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 in shallower than in the deeper layer for all plots.

  1. ESEM results and changes in wettability patterns within soil: three years irrigation with slightly-salted water

    NASA Astrophysics Data System (ADS)

    Valdes-Abellan, Javier; Candela, Lucila; Medero, Gabriela; Buckman, Jim; Hasnayn, Mohammad M.

    2015-04-01

    Impacts on soil and aquifer media from the use of non-conventional water (treated wastewater-TWW, desalted) for irrigation have been widely studied in the last years . A number of contributions have focused on the impacts derived from the use of TWW (Assouline and Narkis, 2013; Lahav et al., 2010; Xu et al., 2010). Changes in soil hydraulic conductivity and clogging processes have been studied in laboratory experiments from soil columns (Lado and Ben-Hur, 2010) and at field scale (Costa, 1999; Minhas et al., 1994). Irrigation with non-conventional water may also lead to the occurrence of contaminants, a major current environmental concern (Valdes-Abellan et al., 2013). Previous studies have considered impacts in a uniform soil media pore structure; less attention has been paid at a microscopic scale and the influence that high-salinity water may have on wettability of soil. Environmental scanning electron microscopy (ESEM) is a useful technique to be applied in soil science to analyse microscopic changes in soil structure or soil wetting patterns. Research applying this technology for wet systems (Donald, 1998) or porous media (Ali et al., 1995) is available, however as far as we know research on soil impacts due to long term irrigation with saline or non-conventional water are much less common. The dynamic mode of the ESEM allows changes of samples from wet to dry by modifying the water vapour pressure and to observe the wetting and drying patterns and interactions between the solid and liquid phase in the soil (Lourenço et al., 2008). Preliminary results of the study at a microscopic scale of soil samples collected before and after three year irrigation with slightly salted water in an experimental plot setup in semi-arid climatic conditions (Alicante, SE Spain) are presented. We will show the micro-structure of soil and undertake a preliminary investigation of wetting and drying of samples using ESEM techniques Differences in the water vapour pressure value at which complete saturation is achieved was detected, being lower in the 3-years irrigated samples compared with the initial ones. Besides, velocity in which saturation took place was different: initial samples saturation process were developed very quickly, as triggered by a critical shift in the water vapour pressure value and much gradual process were develop in the 3-years irrigated sample when saturation started earlier.

  2. Sugarcane Response to Water-Deficit Stress during Early Growth on Organic and Sand Soils

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Approximately 20% of sugarcane (Saccharum spp.) is grown on sand soils in south Florida, USA. Sugarcane yields in the region linearly increased in last 33 years on organic (muck) soils, but not on sand soils. Water deficit during the formative growth phase on sand soils probably limits sugarcane yie...

  3. Assessment of the Water-Extractable Genotoxic Potential of Soil Samples from Contaminated Sites

    Microsoft Academic Search

    Heike Ehrlichmann; Wolfgang Dott; Adolf Eisentraeger

    2000-01-01

    A screening method for the evaluation of the water-extractable genotoxic potential of soil is proposed. Due to the low sensitivity of genotoxicity test systems, PAD-1 resin was used as solid phase to concentrate less hydrophilic compounds from aqueous soil extracts. Concentrated and nonconcentrated aqueous soil extracts from 19 soil samples were evaluated using three genotoxicity assays: the umu test according

  4. Amending greenroof soil with biochar to affect runoff water quantity and quality

    Microsoft Academic Search

    Deborah A. Beck; Gwynn R. Johnson; Graig A. Spolek

    2011-01-01

    Numbers of greenroofs in urban areas continue to grow internationally; so designing greenroof soil to reduce the amount of nutrients in the stormwater runoff from these roofs is becoming essential. This study evaluated changes in extensive greenroof water discharge quality and quantity after adding biochar, a soil amendment promoted for its ability to retain nutrients in soils and increase soil

  5. How to assign a value to soil sustainability? An example based on water erosion modeling.

    E-print Network

    Paris-Sud XI, Université de

    , because life expectancy is a familiar concept, it can be understood easily by non-specialists, such as decision-makers. Life expectancy of soils thus appears to be a valuable indicator of soil sustainability. Keywords: soil sustainability, water erosion, modeling, life expectancy I. INTRODUCTION Soil erosion

  6. Effects of long term irrigation with polluted water and sludge amendment on some soil enzyme activities

    Microsoft Academic Search

    F. O. Topac; H. S. Baskaya; U. Alkan; A. V. Katkat

    2008-01-01

    The objective of this study was to determine the effects of wastewater sludge-fly ash mixtures on urease, dehydrogenase, alkaline phosphatase and beta-glucosidase activities in soils. In order to evaluate the probable effects of previous soil management practices (irrigation with polluted water) on soil enzymes, two different soil samples which were similar in physical properties, but different in irrigation practice were

  7. Relationship between the real and imaginary permittivities, temperature and soil water content measured at 50Hz.

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil moisture sensors generally strive to use the real permittivity as the basis for estimating soil water content from measured electrical properties of soil. It has been shown that a reasonably good general calibration can be developed for mineral soils on this basis. However, at the low measureme...

  8. The Effect of Irrigation Schedules on Water Table Depth and Root Zone Soil Moisture

    E-print Network

    Walker, Jeff

    The Effect of Irrigation Schedules on Water Table Depth and Root Zone Soil Moisture 1 H. T. Nguyen-Mail: thuhien@civenv.unimelb.edu.au Keywords: Irrigation schedules; water table depth; soil moisture; root zone EXTENDED ABSTRACT Indiscriminate use of irrigation water, particularly in existing areas of shallow water

  9. Water treatment residuals amended soils release Mn, Na, S and C

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Water treatment residuals (WTRs) are drinking water treatment byproducts containing chemicals used to purify raw water. Water treatment residuals are used to remediate P-enriched soils. Following soil application, elements present in WTRs have the potential of converting to soluble forms and cause c...

  10. Cumulative soil water evaporation as a function of depth and time

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Soil water evaporation is an important component of the surface water balance and the surface energy balance. Accurate and dynamic measurements of soil water evaporation enhance the understanding of water and energy partitioning at the land-atmosphere interface. The objective of this study is to mea...

  11. Chromium cycling in soils and water: links, gaps, and methods.

    PubMed Central

    Bartlett, R J

    1991-01-01

    The major links in the cycling of chromium in soils and in natural waters are between chromium(III) and chromium (VI). Between the larger links are lesser links involving processes of mobilization and oxidation of CrIII and reduction of CrVI. The gaps are mainly in our understanding of the factors that control these processes. If soluble CrIII is added to an "average" soil, a portion of it will become immediately oxidized by manganese oxides to CrVI. The rest of the CrIII may remain reduced for long periods of time, even in the presence of electron-accepting manganese oxides. However, this less available CrIII can be mobilized by low molecular weight organic complexers and then oxidized where redox conditions are optimal. Usually part of any CrVI added to a soil or sediment will be reduced instantly, especially under acid conditions. On the other hand, high concentrations of polluting CrVI may quickly exhaust the readily available reducing power of the matrix material and excess CrVI, the thermodynamically stable form in air, may persist for years in soils or lagoons without reduction. Cleanup of chromium pollution must involve the surrounding of both CrIII and CrVI with excesses of slowly available reducing substances and sealing them permanently from inputs of atmospheric oxygen. Monitoring the effectiveness of the measures is mandatory, but fortunately the chemical testing for CrVI in soil and water is simple and problem free compared with most colorimetric determinations. PMID:1935847

  12. Temporal changes in soil water repellency linked to the soil respiration and CH4 and CO2 fluxes

    NASA Astrophysics Data System (ADS)

    Qassem, Khalid; Urbanek, Emilia; van Keulen, Geertje

    2014-05-01

    Soil water repellency (SWR) is known to be a spatially and temporally variable phenomenon. The seasonal changes in soil moisture lead to development of soil water repellency, which in consequence may affect the microbial activity and in consequence alter the CO2 and CH4 fluxes from soils. Soil microbial activity is strongly linked to the temperature and moisture status of the soil. In terms of CO2 flux intermediate moisture contents are most favourable for the optimal microbial activity and highest CO2 fluxes. Methanogenesis occurs primarily in anaerobic water-logged habitats while methanotrophy is a strictly aerobic process. In the study we hypothesise that the changes in CO2 and CH4 fluxes are closely linked to critical moisture thresholds for soil water repellency. This research project aims to adopt a multi-disciplinary approach to comprehensively determine the effect of SWR on CO2 and CH4 fluxes. Research is conducted in situ at four sites exhibiting SWR in the southern UK. Flux measurements are carried out concomitant with meteorological and SWR observations Field observations are supported by laboratory measurements carried out on intact soil samples collected at the above identified field sites. The laboratory analyses are conducted under constant temperatures with controlled changes of soil moisture content. Methanogenic and Methanotrophic microbial populations are being analysed at different SWR and moisture contents using the latest metagenomic and metatranscriptomic approaches. Currently available data show that greenhouse gas flux are closely linked with soil moisture thresholds for SWR development.

  13. Effect of some surface and subsurface attributes on soil water erosion

    NASA Astrophysics Data System (ADS)

    Bertol, Ildegardis; César Ramos, Júlio; Vidal Vázquez, Eva; Mirás Avalos, José Manuel

    2013-04-01

    Soil erosion is a complex phenomenon depending on climate, topography, soil intrinsic characteristics, crop and residue cover, and management and conservation practices that may be accelerated by man activities. Within the above mentioned factors, soil cover and soil management most influence soil erosion. Soil management includes mechanical mobilization and in soil conservationist systems soil residues are mobilized for increasing soil surface roughness. Even if soil roughness is ephemeral, it increases soil water storage and sediment retention in surface microdepressions, which contributes to decrease water erosion. Conservationist soil management systems also maintain the soil surface covered by crop residues, which are more persistent than roughness and contribute to dissipate kinetic energy from raindrops and partly also from runoff. Crop residues are more efficient than soil roughness in controlling water erosion because of its ability to retain detached soil particles. The objective of this study was to assess the efficiency of both soil cover by crop residues and soil surface roughness in controlling water erosion. A field experiments was performed on an Inceptisol in South Brazil under simulated rainfall conditions during 2012. The following treatments were evaluated: 1) residues of Italian ryegrass (Lolium multiflorum), 2) residues of common vetch (Vicia sativa), 3) scarification after cultivation of Italian ryegrass, 4) scarification after cultivation of common vetch, 5) scarified bare soil with high roughness as a control. Treatments #1 and 2 involved no-tilled soil with a rather smooth soil surface, where roots and crop residues of the previous crop were maintained. Treatments # 3 and 4 involved a rather high roughness, absence of previous crop residues and maintenance of antecedent roots. Experimental plots were 11 m long and 3.5 m wide with an area of 38.5 m2. Six successive simulated rainfall tests were applied using a rotating-boom rain simulator. During each test, rain intensity was 60 mmhr-1, whereas rain duration was 90 minutes. Italian ryegrass was more efficient than common vetch to control water erosion, both in terms of crop residues and when combining scarification and roots of previous crop. Treatment 1, with soil cover by Italian ryegrass was most efficient to control soil water erosion as the cumulative soil losses were 248 kg ha-1, whereas treatment 4 involving scarification after common vetch was the less efficient within the cultivated treatments, as the soil losses recorded were as high as 31.018 kg ha-1. Soil losses from the control treatments (bare soil) were the highest with a cumulative value o 43.659 kg ha-1. Water losses followed the same rank as soil losses, even if the differences between treatments were smaller than these of soil losses.

  14. Errors in determination of soil water content using time-domain reflectometry caused by soil compaction around wave guides

    SciTech Connect

    Ghezzehei, T.A.

    2008-05-29

    Application of time domain reflectometry (TDR) in soil hydrology often involves the conversion of TDR-measured dielectric permittivity to water content using universal calibration equations (empirical or physically based). Deviations of soil-specific calibrations from the universal calibrations have been noted and are usually attributed to peculiar composition of soil constituents, such as high content of clay and/or organic matter. Although it is recognized that soil disturbance by TDR waveguides may have impact on measurement errors, to our knowledge, there has not been any quantification of this effect. In this paper, we introduce a method that estimates this error by combining two models: one that describes soil compaction around cylindrical objects and another that translates change in bulk density to evolution of soil water retention characteristics. Our analysis indicates that the compaction pattern depends on the mechanical properties of the soil at the time of installation. The relative error in water content measurement depends on the compaction pattern as well as the water content and water retention properties of the soil. Illustrative calculations based on measured soil mechanical and hydrologic properties from the literature indicate that the measurement errors of using a standard three-prong TDR waveguide could be up to 10%. We also show that the error scales linearly with the ratio of rod radius to the interradius spacing.

  15. Soil and Water Science Department University of Florida Effects of different soil amendments on the leachate chemistry of pine forest soil

    E-print Network

    Ma, Lena

    sludge and boiler ash from a paper company affect water quality for a forested site in GeorgiaSoil and Water Science Department University of Florida Effects of different soil amendments quality if we are to maximize the beneficial effects of these wastes while minimizing their adverse

  16. A novel approach in model-based mapping of soil water conditions at forest sites

    Microsoft Academic Search

    Kai Schwärzel; Karl-Heinz Feger; Janet Häntzschel; Alexander Menzer; Uwe Spank; Falko Clausnitzer; Barbara Köstner; Christian Bernhofer

    2009-01-01

    Knowledge of site-specific water conditions is important in forestland evaluation and fundamental for a sustainable forest management. In Central Europe, traditional site mapping has followed an integrated ecological approach. The assessment of soil water availability is based on overlaying relief and descriptive soil information. It is a relative system referring to an (hypothetical) equilibrium between relief-dependent soil conditions and the

  17. Surfactant and irrigation effects on wettable soils: Runoff, erosion, and water retention responses

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Surfactants are chemical compounds that change the contact angle of water on solid surfaces and are commonly used to increase infiltration into hydrophobic soil. Since production fields with water-repellent soil often contain areas of wettable soil, surfactants applied to such fields will likely be ...

  18. 40 CFR 280.65 - Investigations for soil and ground-water cleanup.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...280.65 Investigations for soil and ground-water cleanup...full extent and location of soils contaminated by the release...concentrations of dissolved product contamination in the ground water, owners...evidence that contaminated soils may be in contact with...

  19. 40 CFR 280.65 - Investigations for soil and ground-water cleanup.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...280.65 Investigations for soil and ground-water cleanup...full extent and location of soils contaminated by the release...concentrations of dissolved product contamination in the ground water, owners...evidence that contaminated soils may be in contact with...

  20. 40 CFR 280.65 - Investigations for soil and ground-water cleanup.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...280.65 Investigations for soil and ground-water cleanup...full extent and location of soils contaminated by the release...concentrations of dissolved product contamination in the ground water, owners...evidence that contaminated soils may be in contact with...