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1

Soil nitrogen mineralization as affected by water and temperature interactions  

Microsoft Academic Search

The hypothesis that water and temperature interact to influence the rate of soil N mineralization was studied in laboratory incubation experiments with two contrasting soils. Small sample rings (10 mm tall, 50 mm diameter) were packed to uniform bulk density with 1–2 mm aggregates of Plano silt loam and Wacousta silty clay loam. Samples were brought to five different water

Eileen J. Kladivko; Dennis R. Keeney

1987-01-01

2

Molecular interactions of pesticides at the soil-water interface.  

PubMed

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

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

2008-08-01

3

Interactions between soil structure and excess water formation on chernozem soils  

NASA Astrophysics Data System (ADS)

The main natural resource of Hungary is soil therefore its protection is a fundamental obligation for the state and the farmers too. The frequency of the weather extremeties have increased due to the global climate change which takes effect also on the soil properties. The hungarian agriculture was stricken with drought in the 1990's, whereas excess water has caused damages in the previous decade. According to multi-variable correlation tests, pedological parameters influence on the formation of excess water besides hydrometeorological, geological or relief factors. But not only the soil parameters can take effect on the formation of excess water, but also excess water can modify the soil parameters - causing appearance of hydromorfical characteristics or physical degradation. In our research the interactions between soil structure, excess water and land use were investigated in the aspects of changes in the structure of the upper soil, on a cultivated study area (located on the South Hungarian Great Plain). Three excess water patches were appointed with analysis of multitemporal Landsat images in the study area and were connected a southwest-west-nordeast-east line, forming a 700 meter-long catena. In July, 2011 soil samples were collected along this catena at each 50 meters from the depth of 0-5 cm, 10-15 cm and 20-25 cm to compare the agronomical structure and aggregates stability of soils covered temporally by excess water and without it. Furthermore, penetration resistance and relative moisture of soil were determined at the deep of 60 cm in definite points of a 25x25 m grid on the 45 hectares study field using 3T System hand penetrometer in order to create a multilayer-map from the soil compaction datas. The results call the attention both to the physical soil degradation caused by excess water and to the risk of erosion due to inadequate tillage or cultivation.

Gál, N.; Farsang, A.

2012-04-01

4

Interactions among Climate Forcing, Soil Water, and Groundwater for Enhanced Water Management Practices in Nebraska  

NASA Astrophysics Data System (ADS)

Water is one of the most valuable and vulnerable resources. The varying precipitation regimes together with the varying land use and land cover types over the state of Nebraska necessitate continuous monitoring and modeling of soil water, particularly in the root zone. Underlying the irrigated lands is the High Plains Aquifer, one of the largest in the world. The Ogallala Aquifer is hydrologically connected with streams in numerous river valleys and with rainfall/soil water at the surface. To sustain water reserves the net effect of groundwater pumping for irrigation and recharging the ground water system by precipitation/irrigation. If the net effect is zero or positive the reserves will not shrink. The Automated Weather Data Network (AWDN) of Nebraska has intensive soil water observation and critical weather measurements. Nebraska also has ground water wells, co-located with or near some of the AWDN stations. This work was conducted to continuously monitor the soil water and groundwater table and to model the surface and subsurface hydrologic processes as an integrated/linked system. The further task is to quantify the recharge under different initial conditions, land use practices, and to combine the new information with a surface hydrology model over various sites in Nebraska. To accomplish these objectives two weather stations were installed and enhanced at Shelton and Kearney and soil probes were buried directly under the crop lands. The newly installed soil water probes are co-located with the nearby weather stations and ground water wells. All the data recorded from the atmosphere, soil and aquifer will be incorporated into AWDN data archives and will be analyzed to examine the interactions between precipitation, soil moisture and groundwater.

You, J.; Hubbard, K. G.; Chen, X.

2009-12-01

5

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

Microsoft Academic Search

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

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

2010-01-01

6

Dynamics of the water-pipeline-soil interaction  

SciTech Connect

Pipeline designers must be able to predict the pipeline response to ocean forces in terms of motion amplitude, accumulated displacements, stresses in the steel pipe, and the number of stress oscillations. The mathematical model presented here takes into account the complex environmental and pipeline conditions affecting a pipeline's response to dynamic water-pipe-seabed interaction. The described analysis yields time histories of pipeline motion and steel pipe stresses.

Karal, K.; Halvorsen, S.A.

1982-12-01

7

Interacting vegetative and thermal contributions to water movement in desert soil  

USGS Publications Warehouse

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.

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

2011-01-01

8

Gravel Admix, Vegetation, and Soil Water Interactions in Protective Barriers: Experimental Design, Construction, and Initial Conditions.  

National Technical Information Service (NTIS)

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 d...

W. J. Waugh

1989-01-01

9

Elastoplastic pipe-soil interaction analyses of partially-supported jointed water mains  

Microsoft Academic Search

Water distribution networks are essential components of water supply systems. The combination of pipe structural deterioration\\u000a and mechanics leads to the failure of pipelines. A physical model for estimating the pipe failure must include both the pipe\\u000a deterioration model and mechanics model. Winkler pipe-soil interaction (WPSI), an analytical mechanics model developed by\\u000a Rajani and Tesfamariam (2004), takes external and internal

Yu Shao; Tu-qiao Zhang

2008-01-01

10

Interactions among Climate Forcing, Soil Water, and Groundwater for Enhanced Water Management Practices in Nebraska  

Microsoft Academic Search

Water is one of the most valuable and vulnerable resources. The varying precipitation regimes together with the varying land use and land cover types over the state of Nebraska necessitate continuous monitoring and modeling of soil water, particularly in the root zone. Underlying the irrigated lands is the High Plains Aquifer, one of the largest in the world. The Ogallala

J. You; K. G. Hubbard; X. Chen

2009-01-01

11

Dynamics of the water-pipeline-soil interaction  

SciTech Connect

A design engineer-oriented approach to determining the pipeline dynamic response to ocean forces accounting for complex environmental and pipeline conditions is presented. The described analysis yields time histories of pipeline motion and steel pipe stresses induced by water motion. Sinusoidal variation of normal water particle motion in time and along the pipeline, waves, flexural rigidity of pipe, damaged concrete coating, among other effects, are accounted for in the mathematical model.

Karal, K.; Halvorsen, S.A.

1982-12-01

12

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

Microsoft Academic Search

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

Steven S. Lower; Colin M. Orians

2003-01-01

13

Multi-phase mechanics and multi-scale interactions among soil-water-gas in tsunami disaster  

NASA Astrophysics Data System (ADS)

A tsunami destroys many offshore and seafront structures supported by the sea floor. However, a disaster mechanism to address these concerns has not yet been completely formulated. In this paper, we discuss the ways in which multi-phase interactions among soil, water, and gas and multi-scaling problems from soil, water, and gas particles affect these structures. Based on centrifuge model tests and SPH simulation with three phase interactions, it is shown that the destabilization of offshore structures due to a tsunami not only impacts the sea-front structures, but also causes water seepage into the seabed/seafront soil, which results in the scouring of the soil due to turbulence. Excessive pore water pressure in the soil is generated and liquefaction occurs as a result, which decreases the stiffness of the soil. The scouring and liquefaction occur both at the particle scale and, in the soil, at mass scale, thereby destroying the structures: this is a multi-scale interaction. This study attempts to explain the scouring mechanism by focusing on the tractive force and pore water pressure in the ground. During a tsunami, the traction water flow and the water overflow in the soil generates a vertically upward hydraulic gradient along with excess pore water pressure in the saturated ground and, consequently, scouring is facilitated. Scouring is also expanded when the pore air is blown out of the unsaturated ground. This study finds the scouring in the ground to be facilitated by a three-phase interaction among the soil particles, the pore water, and the pore air.

Imase, Tatsuya; Maeda, Kenichi; Ito, Yoshimi; Goto, Mai

2013-06-01

14

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

NASA Astrophysics Data System (ADS)

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

Otomo, K.; Shikazono, N.

2008-02-01

15

Trees, Soil and Water  

NSDL National Science Digital Library

Trees, soil and water: Journey to Forever - health care for mountains, trees for deserts, trees for people, forest, forestry, deforestation, erosion, soil conservation, water conservation, desertification.

Addison, Keith

2010-01-01

16

Plant-soil Interactions in Temperate Grasslands  

Microsoft Academic Search

We present a conceptual model in which plant-soil interactions in grasslands are characterized by the extent to which water is limiting. Plant-soil interactions in dry grasslands, those dominated by water limitation (‘belowground-dominance’), are fundamentally different from plant-soil interactions in subhumid grasslands, where resource limitations vary in time and space among water, nitrogen, and light (‘indeterminate dominance’). In the belowground-dominance grasslands,

Ingrid C. Burke; William K. Lauenroth; Mary Ann Vinton; Paul B. Hook; Robin H. Kelly; Howard E. Epstein; Martin R. Aguiar; Marcos D. Robles; Manuel O. Aguilera; Kenneth L. Murphy; Richard A. Gill

1998-01-01

17

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

NASA Astrophysics Data System (ADS)

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.

Runyan, C.; D'Odorico, P.

2010-12-01

18

Uncoupled axial, flexural, and circumferential pipe–soil interaction analyses of partially supported jointed water mains  

Microsoft Academic Search

Pipelines used in the distribution of potable water are a vital part of everyday life. The pipelines buried in soil-backfill are exposed to different deleterious reactions; as a result, the design factor of safety may be significantly degraded and, consequently, pipelines may fail prematurely. Proactive pipeline management, which entails optimal maintenance, repair, or replacement strategies, helps increase the longevity of

Balvant Rajani; Solomon Tesfamariam

2004-01-01

19

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

SciTech Connect

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.

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

1988-10-01

20

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

NASA Astrophysics Data System (ADS)

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

Montaldo, N.; Albertson, J. D.

2009-12-01

21

Indicators of nitrate in wetland surface and soil-waters: interactions of vegetation and environmental factors  

NASA Astrophysics Data System (ADS)

This paper describes a new bio-indicator method for assessing wetland ecosystem health; as such, the study is particularly relevant to current legislation such as the EU Water Framework Directive, which provides a baseline of the current status of surface waters. Seven wetland sites were monitored across northern Britain, with model construction data for predicting eco-hydrological relationships collected from five sites during 1999. Two new sites and one repeat site were monitored during 2000 to provide model test data. The main growing season for the vegetation, and hence the sampling period, was May-August during both years. Seasonal mean concentrations of nitrate (NO3-) in surface and soil water samples during 1999 ranged from 0.01 to 14.07 mg N l-1, with a mean value of 1.01 mg N l-1. During 2000, concentrations ranged from trace level (<0.01 mg N l-1) to 9.43 mg N l-1, with a mean of 2.73 mg N l--1. Surface and soil-water nitrate concentrations did not influence plant species composition significantly across representative tall herb fen and mire communities. Predictive relationships were found between nitrate concentrations and structural characteristics of the wetland vegetation, and a model was developed which predicted nitrate concentrations from measures of plant diversity, canopy structure and density of reproductive structures. Two further models, which predicted stem density and density of reproductive structures respectively, utilised nitrate concentration as one of the independent predictor variables. The models were tested where appropriate using data collected during 2000. This approach is complementary to species-based monitoring, representing a useful and simple tool to assess ecological status in target wetland systems and has potential for bio-indication purposes.

Kennedy, M. P.; Murphy, K. J.

22

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

SciTech Connect

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.

Hakim Boukhalfa Mary, P. Neu Alvin Crumbliss

2006-03-28

23

SOIL WATER ENERGY CONCEPTS  

Technology Transfer Automated Retrieval System (TEKTRAN)

The soil water hydraulic pressure head is composed of matric, overburden, and hydrostatic pressures. The soil solution will flow from higher hydraulic pressure heads to lower hydraulic pressure heads. Piezometers are used to measure the hydrostatic pressure head, and tensiometers are used to measu...

24

Effects of C and N availability and soil-water potential interactions on N 2O evolution and PLFA composition  

Microsoft Academic Search

Mitigation of agricultural N2O emissions via management requires quantitative information about the regulation of the underlying processes. In this laboratory study, short-term evolution of N2O from repacked soil was determined using an arable sandy loam soil adjusted to three water potentials (?15, ?30 or ?100 hPa) that were reached by adjustment of partly air-dried soil with nutrient solutions or water; a

Astrid J. Andersen; Søren O. Petersen

2009-01-01

25

Challenges in humid land ecohydrology: Interactions of water table and unsaturated zone with climate, soil, and vegetation  

Microsoft Academic Search

Soil water content is a key determinant of the health of terrestrial ecosystems. It plays a fundamental role in the feedbacks between the Earth and the atmosphere, as well as in all aspects of vegetation growth and composition. The dynamics of soil water in humid areas, and especially in wetlands, presents particularly challenging features for its quantitative description, since it

Ignacio Rodriguez-Iturbe; Paolo D'Odorico; Francesco Laio; Luca Ridolfi; Stefania Tamea

2007-01-01

26

Diurnal Hysteresis Between Soil CO2 and Soil Temperature is Controlled by Soil Water Content  

NASA Astrophysics Data System (ADS)

Soil temperature plays an important role in many model representations of soil CO2 production and transport. However, interactions among environmental variables such as temperature and soil moisture may introduce uncertainty into these models. Among the sources of uncertainty in models of soil CO2 production and transport is daily hysteresis between soil CO2 flux and soil temperature. We quantified the degree to which hysteresis between soil [CO2] and soil temperature is controlled by soil water content in a montane conifer forest, and how this nonlinearity impacts estimates of soil CO2 efflux. Based on chamber measurements at our site, a developed Q10 relationship overestimates CO2 flux by 42 g C m-2 (19%) for the entire growing season due to its inability to account for the daily cycle of soil [CO2], the variability of soil moisture, and moisture-dependent diffusive transport of CO2 through the soil column. Only under late- season dry conditions is the Q10 relationship able to predict CO2 flux. We found that at high levels of soil water content, hysteresis imposes organized, daily variability in the relationship between soil [CO2] and soil temperature, and at low levels of soil water content, hysteresis is minimized. Our results demonstrate that diurnal hysteresis between soil [CO2] and soil temperature is due mostly to the balance (or imbalance in wet soils) between production and diffusion. The seasonality in soil moisture controls the transition from an imbalanced system (where diurnal hysteresis is observed) to a balanced system (no diurnal hysteresis observed). The magnitude of hysteresis in the soil [CO2] - soil temperature relationship is an important indicator of the existence of concomitant, yet independent, autotrophic and heterotrophic soil [CO2] processes. As such, the role of soil water content in controlling the relationship between soil [CO2] and soil temperature should be considered when modeling the dynamics of carbon cycling in ecosystems with strong seasonality in soil water content.

McGlynn, B. L.; Riveros-Iregui, D. A.; Emanuel, R. E.; Muth, D. J.; Epstein, H. E.; Welsch, D. L.; Pacific, V. J.; Wraith, J. M.

2007-12-01

27

Responses of mountain forested watersheds to climate warming: interactions among snowmelt, soil/geology and vegetation water use (Invited)  

NASA Astrophysics Data System (ADS)

At regional scales, spatial variation in eco-hydrologic processes is a complex function of geology, soil, topography, climate and vegetation patterns. Understanding how these different controls vary and interact remains a key challenge for climate change impact assessment. In snow-dominated mountain environments, there is growing evidence that reduced snow accumulation and earlier melt is already occurring and is an important driver of summer streamflow and ecosystem responses. Modelling these responses requires estimation not only of the spatial pattern of melt response to warming, but also the convolution of these spatial patterns with vegetation water use and subsurface drainage. We use a coupled process-based model of ecosystem hydrologic and carbon cycling, RHESSys, to demonstrate that soil moisture drainage and storage characteristics exert a significant control on how forest water use, and streamflow respond to earlier snowmelt. We focus our modeling scenarios on sites with measurements of streamflow, and vegetation growth that can be used to evaluate model performance. We then use the model to show how the combined changes in snowmelt and terrestrial ecosystem responses alter streamflow regimes and may have important implications for aquatic and human communities. These modeling studies provide an expanded perspective on landscape-level sensitivities to climate warming, and can provide guidance for the strategic design of data assimilation and monitoring strategies.

Tague, C.; Choate, J.; Dugger, A. L.; Garcia, E.; Groulx, D.; Son, K.

2010-12-01

28

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

Microsoft Academic Search

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

Maja ZUPAN?I? JUSTIN

29

Soils, Water Quality, and Watershed Size: Interactions in the Maumee and Sandusky River Basins of Northwestern Ohio  

Microsoft Academic Search

The Water Quality Laboratory (WQL) at Heidelberg College initiated storm event sampling for total phos- Soil variability in watersheds accounts for the problem of parti- phorus in the Sandusky River basin in 1969 (Baker and tioning downstream water quality data and evaluating sources of non- Kramer, 1976). Continuous studies of nutrient and sedi- point pollution. This review of previous water

Frank G. Calhoun; David B. Baker; Brian K. Slater

30

Vegetation-soil water interaction within a dynamical ecosystem model of grassland in semi-arid areas  

NASA Astrophysics Data System (ADS)

A dynamical ecosystem model with three variables, living biomass, wilted biomass and available soil wetness, is developed to examine the vegetation-soil water interaction in semi-arid areas. The governing equations are based on the mass conservation law. The physical and biophysical processes are formulated with the parameters estimated from observational data. Both numerical results and qualitative analysis of the model as well as observational data indicate that the maintenance of a grassland requires a minimum precipitation (or equivalently, a minimum moisture index), and the grassland and desert ecosystem can coexist when precipitation is within a range above this threshold. Sensitivity studies show that these numerical results are robust with respect to model parameters and the transformation functions. It is also found that the wilted vegetation plays a very important role in shaping the transition between grassland and desert. By using the theories of an attractor basin and multiple equilibrium states, the conditions for grassland maintenance and the strategy of grazing are also analysed.

Zeng, Xiaodong; Zeng, Xubin; Shen, Samuel S. P.; Dickinson, Robert E.; Zeng, Qing-Cun

2005-07-01

31

Challenges in humid land ecohydrology: Interactions of water table and unsaturated zone with climate, soil, and vegetation  

NASA Astrophysics Data System (ADS)

Soil water content is a key determinant of the health of terrestrial ecosystems. It plays a fundamental role in the feedbacks between the Earth and the atmosphere, as well as in all aspects of vegetation growth and composition. The dynamics of soil water in humid areas, and especially in wetlands, presents particularly challenging features for its quantitative description, since it needs to be linked to the intertwined stochastic fluctuations of the water table and the soil moisture of the unsaturated zone. These fluctuations are themselves dependent on the climate, soil, and vegetation of the region. The paper describes some of the most important problems that need to be considered in attempting to develop a quantitative framework for the ecohydrology of humid areas. The avenues of research suggested here will play a keystone role in the understanding of the complex dynamics of humid lands as well as in their scientifically based management in the face of a changing climate.

Rodriguez-Iturbe, Ignacio; D'Odorico, Paolo; Laio, Francesco; Ridolfi, Luca; Tamea, Stefania

2007-09-01

32

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

NASA Astrophysics Data System (ADS)

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

Lowry, C.; Loheide, S. P.

2009-12-01

33

Soils, water quality, and watershed size: interactions in the Maumee and Sandusky river basins of northwestern Ohio.  

PubMed

Soil variability in watersheds accounts for the problem of partitioning downstream water quality data and evaluating sources of non-point pollution. This review of previous water quality studies was conducted to examine more closely the influence of soil properties on pollutant export. The approach used in this paper was to start with data from the two largest watersheds (Maumee and Sandusky) and then compare them on a unit area export basis with data from intermediate-size and smaller watersheds. General relationships between pollutant levels at the river mouth and upstream soil conditions are vague and seemingly contradictory at the large-watershed scale. With smaller watersheds, it can be determined that soil texture, slope, and internal drainage are controlling factors for pollutant export. Although Paulding (very-fine, illitic, nonacid, mesic Typic Epiaquept) and Roselms (very-fine, illitic, mesic Aeric Epiaqualf) soils occupy only 5% of the Maumee basin, they generate more than 10 times as much sediment per unit area as the tile-drained Hoytville (fine, illitic, mesic Mollic Epiaqualf) soils that occupy 16% of the Maumee basin. Tile drainage of very poorly drained soils that are formed from either glacial till or silty to sandy lake deposits reduces runoff and increases downward movement of soluble nutrients into tile drains. The assumption that sloping moraine areas are the primary source of pollutants should be reexamined based on this review. PMID:11837443

Calhoun, Frank G; Baker, David B; Slater, Brian K

34

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

Microsoft Academic Search

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

R. D Connolly

1998-01-01

35

Soils - Part 2: Physical Properties of Soil and Soil Water  

NSDL National Science Digital Library

 This lesson will help you understand the major components of the physical properties of soil. You will learn such terms as texture, aggregation, soil structure, bulk density, and porosity as it relates to soils. You will learn how soil holds and transmits water and cultural practices that enhance or degrade physical properties of the soil.[This lesson, as well as the other nine lessons in the Soils series, is taken from the "Soils Home Study Course," published in 1999 by the University of Nebraska Cooperative Extension.

36

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

NASA Astrophysics Data System (ADS)

The conversion of wetlands to intensively managed forest lands in eastern North Carolina is widespread and the consequences on water and carbon balances are not well studied. Quantification of evapotranspiration (ET), tree transpiration and their biophysical regulation are needed for assessing forest water management options. We characterized vertical variation in the diurnal and seasonal soil volumetric water content at 10 cm intervals to evaluate changes in water availability for root uptake and monitored eddy covariance ET and tree transpiration (sap flux) in a drained Loblolly pine (Pinus taeda L.) plantation. We also quantified the magnitude of hydraulic redistribution (HR), the passive movement of soil water from deep to shallow roots, to identify factors affecting the seasonal dynamics of root water uptake, root and plant water potentials and stomatal conductance. Soil water content varied with soil depth and total water use from the upper 1m peaked between 4 and 6.5 mm/day during the growing season and was strongly correlated and similar to ET (ET represented 90-95% of total water depletion). After periods of more than 10 days without rain, water extraction shifted to the deeper layers, and recharge from HR approached 0.5 mm/day in the upper 60 cm. However, the upper 30cm accounted for 40% of total water depletion from the upper 1m at peak water uptake (>4 mm/day), and increased to 65% during days of low water uptake (<2 mm/day), illustrating the contribution of deeper roots to water uptake during days of high evaporative demand. This result was supported by the fact that deep roots (from 30-50cm) accounted for 65% of the total water redistributed. Because of stomatal regulation to prevent water potentials from reaching critical values that would cause significant loss of tree hydraulic conductivity, maximum tree transpiration during high evaporative demand remained constant at around 3 mm/day. Tree transpiration represented on average 60% of ET. However, it represented only 50% of ET on days following rain events and up to 80% of ET after prolonged periods without rain. We propose that HR prevented predawn water potentials from decreasing during periods of increasing soil water deficit, therefore maintaining a constant driving force for water uptake of around 1.7 MPa. It was thought that HR was an important mechanism for maintaining shallow root function during drought and preventing total stomatal closure but our study shows that even in wet conditions with soil water potentials never dropping below -0.6 MPa, HR may play a role in wetland hydrological balance. This first approximation of the extent of HR in this ecosystem suggests that it is likely to be an important process in wet forests of North Carolina.

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

2007-12-01

37

72: Measuring Soil Water Content  

Microsoft Academic Search

Major advances in the measurement of soil water content have arisen from electromagnetic (EM) methods that have developed rapidly in the last 20years. Estimates of water content from EM measurements make use of the large relative permittivity of water compared to other soil components. Time domain reflectometry (TDR) and capacitance approaches use \\

G CLARKE TOPP

38

Boron isotopes in different grain size fractions: Exploring past and present water–rock interactions from two soil profiles (Strengbach, Vosges Mountains)  

NASA Astrophysics Data System (ADS)

In the present study, we test the ability of B isotopes to trace past and present weathering reactions in the case of two forest soils formed by a polyphasic sequence involving early hydrothermal alteration of the bedrock and pedogenesis. We provide B chemical and isotopic compositions in two 2-m soil profiles sampled in the Strengbach watershed (Vosges, France). The two soils belong to different soil series, an ochreous podzol (Haplorthod) and a brown acidic soil (dystrochrept), developed on the same granitic bedrock but differently affected by hydrothermal alteration. Separated granulometric fractions and bulk soil samples have been analyzed. Coarse particles are mostly composed of primary minerals and show a clear anti-correlation between ?11B and Mg/Al, reflecting various grades of the early hydrothermal alteration. The finest particles (clay-size fractions) deviate from this "hydrothermal" trend and are diagnostic of pedogenic processes occurring after B exchange with the surrounding 11B-rich soil solution. Examination of the B distribution in different particle size fractions also indicates that B is transferred from the coarse sand fraction in deeper soil layers to the clay fraction in the upper layers. The intermediate size fractions are found to play only a secondary role in the soil-forming reactions. The two soils show distinct B isotope profiles, which are consistent with the different pedogenic processes that govern their formation. In the podzolic soil, ?11B can be explained by a simple model in which pedogenesis occurs by continuous dissolution of primary minerals and precipitation of secondary ones. In the brown acid soil, a more complex model that includes the precipitation of clay minerals in the deep horizon and their gradual dissolution in the upper soil layers accounts for the observed results. Additionally, residual hydrothermal illites are more resistant to weathering and are found in the clay fraction where they were directly inherited from the dislocation of coarser grains in which they were encapsulated.On a broader scale, the large B isotopic fractionation during water–rock interactions greatly facilitates the quantification of matter exchange between soil solutions and solids and the determination of global weathering rates. The data from the present study demonstrate that the determination of B isotopes in different particle size fractions can reveal the relative importance of source and process effects during weathering.

Lemarchand, D.; Cividini, D.; Turpault, M.-P.; Chabaux, F.

2012-12-01

39

Interactive Effect of Soil Salinity and Water Stress on Growth and Chemical Compositions of Pistachio Nut Tree  

Microsoft Academic Search

The effects of three sodium chloride (NaCl) levels (0, 1200, and 2400 mg kg soil) and three irrigation intervals (3, 7, and 14 d) on the growth and chemical composition of two Pistacia vera rootstocks (‘Sarakhs’ and ‘Qazvini’) were investigated under greenhouse conditions. Eight-week-old pistachio seedlings were gradually exposed to salt stress which afterward, water stress was initiated. At any

A. R. Saadatmand; Z. Banihashemi; M. Maftoun; A. R. Sepaskhah

2007-01-01

40

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

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

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

2012-08-21

41

Soil water availability and microsite mediate fungal and bacterial phospholipid fatty acid biomarker abundances in Mojave Desert soils exposed to elevated atmospheric CO2  

Microsoft Academic Search

Elevated CO2 interacts with soil water and microsite to affect soil microbesFungal biomarkers indicate active metabolism of newer C under elevated CO2Soil water availability is key to Mojave Desert soil C and nutrient cycles

V. L. Jin; S. M. Schaeffer; S. E. Ziegler; R. D. Evans

2011-01-01

42

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

NASA Astrophysics Data System (ADS)

In snow-dominated mountain systems, a warming climate alters soil water deficit through changing the timing and magnitude of moisture inputs as precipitation and snowmelt and through changes in the timing and magnitude of evapotranspiration losses. The net effect of climate warming on soil water deficit and associated ecosystem processes ultimately depends on the interaction between changes in inputs and outputs and on vegetation, micro-climate and soil properties that control the sensitivity of soil water to changes in input/output drivers. In mountain environments, steep spatial gradients result in substantial variation in atmospheric forcing and vegetation and soil properties over relatively short spatial scales, which necessitate providing finer-scale assessment of climate change impact. Measurements of soil moisture and forest responses to climate are often made at plot scales but are limited in spatial coverage. Coupled eco-hydrologic models, applied at relatively fine (m) scales provide a method of extrapolating findings from local measurements and exploring hillslope and watershed scale impacts of climate warming on moisture deficit. In this study, we use RHESSys (Regional hydro-ecologic simulation system) combined with spatially intensive monitoring of coupled ecohydrologic variables at the Southern Sierra Critical Zone Observatory (SSCZO), located in the Sierra National Forest, California. We initially use the model to identify clusters of distinctive water deficit behavior as summarized by indices of summertime soil moisture and transpiration recessions. The resulting clusters demonstrate that both elevational differences in energy availability and topographic controls on drainage are 1st order controls on spatial patterns of summertime moisture deficit and tree transpiration. We then use these initial model clusters to guide soil moisture and sapflux data collection. The collected data are used to characterize soil moisture deficit and transpiration for each cluster evaluate and improve the model predictions. Our initial results highlight the importance of adequate representation of micro-climate patterns as controls on summer moisture deficits and transpiration. We then use the model to show how spatial patterns of summertime moisture deficit and transpiration may change under future climate scenarios. We apply two approaches which are 1) using 2 and 4 C° uniform temperature adding to the historic meteorological records and 2) using a downscaled GCM climate projection.

Son, K.; Tague, C.

2011-12-01

43

Antimony interactions with heterogeneous complexants in waters, sediments and soils: A review of data obtained in bulk samples  

NASA Astrophysics Data System (ADS)

Published studies where antimony association with colloidal and particulate phases is studied in waters, soils and sediments are reviewed. The techniques considered range from the simple calculation of partition coefficients, the application of size-based speciation methods or sequential extraction techniques to the use of more sophisticated techniques such as X-ray absorption spectroscopy (XAS). What these methods have in common is that they are applied directly to bulk samples and that, with the exception of XAS, they give operationally defined results, which are very often difficult to interpret and compare. In the case of the extraction methods, which are the most commonly used, this difficulty is compounded by the tendency of many authors to endlessly modify the experimental procedures. Antimony does not seem to associate to any significant extent with colloidal and particulate phases in waters. However, at the same time, it appears not to be easily extractable from soils where, even if it is usually present to a certain extent in 'iron oxide' fractions in sequential extraction methods, most remains in the so called 'residual' fraction. Unfortunately, the direct application of XAS techniques to real environmental samples, which could help to clarify antimony binding by solid phases, is precluded in most systems because of their insensitivity; only a few heavily polluted systems have been studied so far using these techniques. In these studies antimony is present as Sb(V) in soils and significantly bound by iron oxide phases.

Filella, Montserrat

2011-08-01

44

Multiple equilibrium states and the abrupt transitions in a dynamical system of soil water interacting with vegetation  

NASA Astrophysics Data System (ADS)

In semi-arid areas, multiple equilibrium states of an ecosystem (e.g., grassland and desert) are found to coexist, and the transition from grassland to desert is often abrupt at the boundary. A simple ecosystem model is developed to provide the biophysical explanation of this phenomenon. The model has three variables: living biomass, wilted biomass, and soil wetness. The moisture index, which is the ratio of the annual precipitation to potential evaporation, is the only external climate driving force, and the key mechanism is the vegetation-soil interaction. It is found that the maintenance of a grassland requires a minimum moisture index, and the abrupt transition occurs when the moisture index is around this critical value. These results are robust within a wide range for most model parameters, suggesting that the model may be applicable to other temperate grasslands. The characteristics of the wilted biomass also strongly influence the ecosystem's dynamics.

Zeng, Xiaodong; Shen, Samuel S. P.; Zeng, Xubin; Dickinson, Robert E.

2004-03-01

45

Soil and Water: Some Teaching Suggestions.  

ERIC Educational Resources Information Center

|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)|

Fischer, Richard B.

1987-01-01

46

Estimating soil water retention using soil component additivity model  

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

47

Elementary soil and water engineering  

SciTech Connect

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

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

1985-01-01

48

The Mobility of Water in Frozen Soils.  

National Technical Information Service (NTIS)

New relations for the flow of water in partially frozen soils are now being incorporated into frost heave models. The thermodynamic equilibrium equations for freezing soil water are well established but the partition of the soil system stresses within fre...

V. J. Lunardini R. Berg R. McGaw T. Jenkins Y. Nakano

1982-01-01

49

Sowing soil water content effects on chickpea ( Cicer arietinum L.): Seedling emergence and early growth interaction with genotype and seed size  

Microsoft Academic Search

Soil water content at sowing is an important determinant of chickpea seed emergence and early growth. The seed emergence and seedling growth of 9 kabuli and 11 desi chickpea genotypes sown and grown under four soil moisture contents (25, 50, 75 and 100% of field capacity) was measured in a glasshouse study. Across soil moisture treatments the day of first

N. M. Hosseini; J. A. Palta; J. D. Berger; K. H. M. Siddique

2009-01-01

50

The Effects of Microbiotic Soil Crustson Soil Water Loss  

Microsoft Academic Search

Microbiotic soil crusts play several important roles in many arid and semiarid ecosystems around the world. Their effects on soil hydrology, however, are poorly understood. It has been speculated that crusts (1) improve soil water availability by \\

D. B. George; B. A. Roundy; L. L. S. T. CLAIR; J. R. Johansen; G. B. Schaalje; B. L. Webb

2003-01-01

51

Comparison of laboratory TDR soil water measurements  

Microsoft Academic Search

Reliable soil moisture sensors are essential for agricultural application. Time Domain Reflectometry (TDR) is a useful method for nondestructive, continuous measurements of soil water content. Laboratory measurements of soil volumetric water content by the TDR 100 Time Domain Reflectometer were compared to gravimetric measurements in three soils, Clay Loam, Silt Loam and Sand soil. Comparison between original and homemade 10

Vesna ZUPANC; Gregor ADAM; Marina PINTAR

2005-01-01

52

Microbiotic soil crusts in the Sahel of Western Niger and their influence on soil porosity and water dynamics  

Microsoft Academic Search

Microbiotic soil crusts are common features of the surface of fallow land in Western Niger. We investigated the interaction between these microbial covers and the porosity and water dynamics of soils at the surface of a Sahelian landscape. The soil pore system was examined by microscopic observations and mercury porosimetry. The soil water retention capacity was measured using a Richard

O. Malam Issa; C. Défarge; J. Trichet; C. Valentin; J. L. Rajot

2009-01-01

53

Solitary water wave interactions  

Microsoft Academic Search

This article concerns the pairwise nonlinear interaction of solitary waves in the free surface of a body of water lying over a horizontal bottom. Unlike solitary waves in many completely integrable model systems, solitary waves for the full Euler equations do not collide elastically; after interactions, there is a nonzero residual wave that trails the post-collision solitary waves. In this

Walter Craig; P. Guyenne; J. Hammack; D. Henderson; C. Sulem

2006-01-01

54

Soil-Plant Nutrient Interactions on Manure Enriched Calcareous Soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

55

Estimating adsorbed water film thickness in unsaturated soil  

NASA Astrophysics Data System (ADS)

In saturated soil, water fills every crack and crevice between the individual grains of dirt. As the water evaporates or drains away, some water can become trapped between soil particles by capillary pressure or be adsorbed onto the surface of the grains in extremely thin films. The variable thickness of these adsorbed films affects contaminant reaction and transfer rates, stored water volumes, and the rate of water transfer through the soil. As such, proper parameterizations of adsorbed film thickness are important in hydrologic models. However, techniques that estimate the film thickness by averaging the total water volume by the soil surface area or by relating the film thickness to the size of the individual soil grains tend to underestimate or overestimate the thickness of the adsorbed films. Many of these previous approaches use macroscopic properties to estimate a quantity that is largely controlled by small-scale interactions.

Schultz, Colin

2011-09-01

56

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...

57

The moisture response of soil heterotrophic respiration: interaction with soil properties  

NASA Astrophysics Data System (ADS)

Soil moisture is of primary importance for predicting the evolution of soil carbon stocks and fluxes, both because it strongly controls organic matter decomposition and because it is predicted to change at global scales in the following decades. However, the soil functions used to model the heterotrophic respiration response to moisture have limited empirical support and introduce an uncertainty of at least 4% in global soil carbon stock predictions by 2100. The necessity of improving the representation of this relationship in models has been highlighted in recent studies. Here we present a data-driven analysis of soil moisture-respiration relations based on 90 soils. With the use of linear models we show how the relationship between soil heterotrophic respiration and different measures of soil moisture is consistently affected by soil properties. The empirical models derived include main effects and moisture interaction effects of soil texture, organic carbon content and bulk density. When compared to other functions currently used in different soil biogeochemical models, we observe that our results can correct biases and reconcile differences within and between such functions. Ultimately, accurate predictions of the response of soil carbon to future climate scenarios will require the integration of soil-dependent moisture-respiration functions coupled with realistic representations of soil water dynamics.

Moyano, F. E.; Vasilyeva, N.; Bouckaert, L.; Cook, F.; Craine, J.; Curiel Yuste, J.; Don, A.; Epron, D.; Formanek, P.; Franzluebbers, A.; Ilstedt, U.; Kätterer, T.; Orchard, V.; Reichstein, M.; Rey, A.; Ruamps, L.; Subke, J.-A.; Thomsen, I. K.; Chenu, C.

2012-03-01

58

The moisture response of soil heterotrophic respiration: interaction with soil properties  

NASA Astrophysics Data System (ADS)

Soil moisture is of primary importance for predicting the evolution of soil carbon stocks and fluxes, both because it strongly controls organic matter decomposition and because it is predicted to change at global scales in the following decades. However, the soil functions used to model the heterotrophic respiration response to moisture have limited empirical support and introduce an uncertainty of at least 4 % in global soil carbon stock predictions by 2100. The necessity of improving the representation of this relationship in models has been highlighted in recent studies. Here we present a data-driven analysis of soil moisture-respiration relations based on 90 soils. With the use of linear models we show how the relationship between soil heterotrophic respiration and different measures of soil moisture is consistently affected by soil properties. The empirical models derived include main and moisture interaction effects of soil texture, organic carbon content and bulk density. When compared to other functions currently used in different soil biogeochemical models, we observe that our results can correct biases and reconcile differences within and between such functions. Ultimately, accurate predictions of the response of soil carbon to future climate scenarios will require the integration of soil-dependent moisture-respiration functions coupled with realistic representations of soil water dynamics.

Moyano, F. E.; Vasilyeva, N.; Bouckaert, L.; Cook, F.; Craine, J.; Curiel Yuste, J.; Don, A.; Epron, D.; Formanek, P.; Franzluebbers, A.; Ilstedt, U.; Kätterer, T.; Orchard, V.; Reichstein, M.; Rey, A.; Ruamps, L.; Subke, J.-A.; Thomsen, I. K.; Chenu, C.

2011-12-01

59

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...

60

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...

61

A modified soil water based Richards equation for layered soils  

Microsoft Academic Search

Most Soil-Vegetation-Atmosphere-Transfer (SVAT) models like TERRA-ML (implemented e.g. in the CCLM model (www.clm-community.eu)) use the soil moisture based Richards equation to simulate vertical water fluxes in soils, assuming a homogeneous soil type. Recently, high-resolution soil type datasets (e.g. BüK 1000, only for Germany (Federal Institute for Geosciences and Natural Resources, BGR, www.bgr.bund.de) or Harmonized World Soil Database (HWSD, version 1.1,

F. Kalinka; B. Ahrens

2010-01-01

62

Soil Water and Temperature System (SWATS) Handbook  

SciTech Connect

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

Bond, D

2005-01-01

63

Modeling the soil system: Bridging the gap between pedology and soil-water physics  

NASA Astrophysics Data System (ADS)

The biological and geochemical processes in soil such as organic matter mineralization, microbiological activity, and plant alimentation can be accurately assessed and modeled only with the knowledge of the thermodynamic status of the soil medium where these processes take place. However, current soil water models do not define and characterize the soil structure or the thermodynamic state of the soil water interacting with this structure. This article presents a new paradigm in characterizing and modeling the organized soil medium and the physical properties resulting from this organization. It describes a framework of the modeling approach as a contribution to the General Systems theory. The basic concept of Representative Elementary Volume (REV) in soil physics and hydrology was transformed into the concept of Structure Representative Volume (SREV) which takes into account the hierarchical organization of the structured soil medium. The pedostructure is defined as the SREV of the soil medium and this concept is at the basis of the new paradigm including variables, equations, parameters, and units in soil physics, in a similar way that the REV is at the basis of the continuous porous media mechanics applied to soils. The paradigm allows for a thermodynamic characterization of the structured soil medium with respect to soil water content then bridging the gap between pedology and soil physics. We show that the two points of view (REV and SREV) are complementary and must be used in the scaling of information. This approach leads to a new dimension in soil-water properties characterization that ensures a physically based modeling of processes in soil and the transfer of information from the physical scale of processes (pedostructure or laboratory measurements scale) to the application scale of the other disciplines (modeling and mapping scale).

Braudeau, Erik; Mohtar, Rabi H.

2009-05-01

64

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

65

A modified soil water based Richards equation for layered soils  

NASA Astrophysics Data System (ADS)

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

Kalinka, F.; Ahrens, B.

2010-09-01

66

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

Microsoft Academic Search

Documentation of the degree and direction of effects of ozone on transpiration of canopies of mature forest trees is critically needed to model ozone effects on forest water use and growth in a warmer future climate. Patterns of sap flow in stems and soil moisture in the rooting zones of mature trees, coupled with late-season streamflow in three forested watersheds

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

2007-01-01

67

Simulations on soil water variation in arid regions  

Microsoft Academic Search

Significant soil water variation has often been found in top few meters of arid soils. Understanding soil water variation in these soils is crucial to groundwater recharge estimation, rainfall runoff process, risk assessment, and water resource management. A soil hydrologic model (SHM) was developed for simulating soil water movement in the vertical direction using time steps of minutes to days.

Weiquan Dong; Zhongbo Yu; Dennis Weber

2003-01-01

68

Solitary water wave interactions  

NASA Astrophysics Data System (ADS)

This article concerns the pairwise nonlinear interaction of solitary waves in the free surface of a body of water lying over a horizontal bottom. Unlike solitary waves in many completely integrable model systems, solitary waves for the full Euler equations do not collide elastically; after interactions, there is a nonzero residual wave that trails the post-collision solitary waves. In this report on new numerical and experimental studies of such solitary wave interactions, we verify that this is the case, both in head-on collisions (the counterpropagating case) and overtaking collisions (the copropagating case), quantifying the degree to which interactions are inelastic. In the situation in which two identical solitary waves undergo a head-on collision, we compare the asymptotic predictions of Su and Mirie [J. Fluid Mech. 98, 509 (1980)] and Byatt-Smith [J. Fluid Mech. 49, 625 (1971)], the wavetank experiments of Maxworthy [J. Fluid Mech. 76, 177 (1976)], and the numerical results of Cooker, Weidman, and Bale [J. Fluid Mech. 342, 141 (1997)] with independent numerical simulations, in which we quantify the phase change, the run-up, and the form of the residual wave and its Fourier signature in both small- and large-amplitude interactions. This updates the prior numerical observations of inelastic interactions in Fenton and Rienecker [J. Fluid Mech. 118, 411 (1982)]. In the case of two nonidentical solitary waves, our precision wavetank experiments are compared with numerical simulations, again observing the run-up, phase lag, and generation of a residual from the interaction. Considering overtaking solitary wave interactions, we compare our experimental observations, numerical simulations, and the asymptotic predictions of Zou and Su [Phys. Fluids 29, 2113 (1986)], and again we quantify the inelastic residual after collisions in the simulations. Geometrically, our numerical simulations of overtaking interactions fit into the three categories of Korteweg-deVries two-soliton solutions defined in Lax [Commun. Pure Appl. Math. 21, 467 (1968)], with, however, a modification in the parameter regime. In all cases we have considered, collisions are seen to be inelastic, although the degree to which interactions depart from elastic is very small. Finally, we give several theoretical results: (i) a relationship between the change in amplitude of solitary waves due to a pairwise collision and the energy carried away from the interaction by the residual component, and (ii) a rigorous estimate of the size of the residual component of pairwise solitary wave collisions. This estimate is consistent with the analytic results of Schneider and Wayne [Commun. Pure Appl. Math. 53, 1475 (2000)], Wright [SIAM J. Math. Anal. 37, 1161 (2005)], and Bona, Colin, and Lannes [Arch. Rat. Mech. Anal. 178, 373 (2005)]. However, in light of our numerical data, both (i) and (ii) indicate a need to reevaluate the asymptotic results in Su and Mirie [J. Fluid Mech. 98, 509 (1980)] and Zou and Su [Phys. Fluids 29, 2113 (1986)].

Craig, W.; Guyenne, P.; Hammack, J.; Henderson, D.; Sulem, C.

2006-05-01

69

Numerical Modeling of Steady-State Plow/Soil Interaction.  

National Technical Information Service (NTIS)

A numerical model of steady-state plow/soil interaction in support of cable burial operations on the seafloor was developed. Coupled field equations for equilibrium of an elasto-plastic medium and pore water diffusion in the presence of rigid surfaces con...

T. A. Shugar

1997-01-01

70

Analysis of Soil-Structure Interaction Considering Complicated Soil Profile  

Microsoft Academic Search

The effect of soil-structure interaction (SSI) is an important consideration and cannot be neglected in the seismic design\\u000a of structures on soft soil. Various methods have been developed to consider SSI effects and are currently being used. However,\\u000a most of the approaches including a general finite element method cannot appropriately consider the properties and characteristics\\u000a of the sites with complicated

Jang Ho Park; Kwan-soon Park; Ok Seung-yong

2006-01-01

71

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

Microsoft Academic Search

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

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

2005-01-01

72

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

NASA Astrophysics Data System (ADS)

The conversion of wetlands to intensively managed forest lands in eastern North Carolina is widespread and the consequences on water and carbon balances are not well studied. Quantification of evapotranspiration (ET), tree transpiration and their biophysical regulation are needed for assessing forest water management options. We characterized vertical variation in the diurnal and seasonal soil volumetric water content at 10 cm intervals to evaluate changes in water availability for root uptake and monitored eddy covariance ET and tree transpiration (sap flux) in three contrasting loblolly pine (Pinus taeda L.) stands. Those stands included a 50- yr-old wetland natural regeneration (NG), a 17-yr-old drained mid-rotation plantation (MP) and a 5-yr-old drained plantation (YP) in eastern North Carolina. We also quantified the magnitude of hydraulic redistribution (HR), the passive movement of soil water from deep to shallow roots, to identify factors affecting the seasonal dynamics of root water uptake, root and plant water potentials and stomatal conductance. In NG, soil water content was always at full saturation and total tree water use peaked between 6-7 mm/day, and this stand was used as reference. In MP, soil water content varied with soil depth and total water use from the upper 1m peaked between 4 and 6.5 mm/day during the growing season and was strongly correlated and similar to ET (ET represented 90-95% of total water depletion). In YP, soil water used was limited to the upper 30 cm and was strongly affected by summer drought by declining progressively from 0.9 mm/day in spring to 0.4 m/day in September. After periods of more than 10 days without rain, water extraction in MP shifted to the deeper layers, and recharge from HR approached 20% of ET. During days of high evaporative demand, water use in MP was comparable to NG thanks to HR and to the contribution of deeper roots to water uptake. In YP, HR never contributed for more than 8% of ET. There was no HR in NG. Tree transpiration represented on average 60% and 40% of ET in MP and YP, respectively. However, in MP it represented only 50% of ET on days following rain events and up to 80% of ET after prolonged periods without rain. In MP, we propose that HR prevented soil water potentials from decreasing during periods of increasing soil water deficit, therefore maintaining a constant driving force for water uptake. In MP, HR was an important mechanism for maintaining shallow root function during drought and preventing total stomatal closure. Our study shows that HR prevented soil water potentials from dropping below -0.6 MPa, and played a role in wetland hydrological balance by increasing water uptake in MP to level close to those of trees growing on pure wetlands (NG).

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

2009-05-01

73

Porosity and Water Flow in Soils  

NSDL National Science Digital Library

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.

Gautam, Tej

74

SW—Soil and Water  

Microsoft Academic Search

The propagation of heat in soil is governed by its thermal characteristics. The ability to monitor soil thermal conductivity is an important tool in managing the soil temperature regime to affect seed germination and crop growth. The effect of bulk density and moisture content on the thermal conductivity of two sieved and repacked soils was investigated through laboratory studies. These

N. H. Abu-Hamdeh

2001-01-01

75

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...

76

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

PubMed

* Documentation of the degree and direction of effects of ozone on transpiration of canopies of mature forest trees is critically needed to model ozone effects on forest water use and growth in a warmer future climate. * Patterns of sap flow in stems and soil moisture in the rooting zones of mature trees, coupled with late-season streamflow in three forested watersheds in east Tennessee, USA, were analyzed to determine relative influences of ozone and other climatic variables on canopy physiology and streamflow patterns. * Statistically significant increases in whole-tree canopy conductance, depletion of soil moisture in the rooting zone, and reduced late-season streamflow in forested watersheds were detected in response to increasing ambient ozone levels. * Short-term changes in canopy water use and empirically modeled streamflow patterns over a 23-yr observation period suggest that current ambient ozone exposures may exacerbate the frequency and level of negative effects of drought on forest growth and stream health. PMID:17335503

McLaughlin, S B; Wullschleger, S D; Sun, G; Nosal, M

2007-01-01

77

Soil Water Repellency in Amazonian Pastures  

NASA Astrophysics Data System (ADS)

Conversion of forest to pastures represents the largest land use change in the Brazilian Amazon. Soil water repellency (hydrophobicity) impacts water, carbon, and nutrient pathways on millions of hectares worldwide and has been shown to result from fire. However, the extent and severity of soil water repellency and its impact on tropical agroecosystems remains an important knowledge gap. Water repellent soils were identified in pastures in Northwest Mato Grosso. The intensity and spatial variability of soil water repellency were determined in situ at the mineral soil surface at both micro- (mm<) and meso-scales (m<) following several weeks without rainfall. Measurements were made using the Molarity of an Ethanol Droplet (MED) test in pastures of various lengths of time since burning. Drops of increasing ethanol molarity were applied until the surface tension of the solution was sufficiently small to overcome the hydrophobic repulsion of the soil. Soils of recently burned pastures exhibited extreme water repellency (MED > 3.5 N). Soil water repellency of pastures was found to be significantly correlated to the length of time since the pasture was last burned (R2=0.38; p=0.02). Pastures that had not been burned for over a year were found to be strongly water repellent (MED > 2 N), with 7 years without burning required for pastures to become hydrophilic (MED <1 N). High MED values following pasture fires may indicate the role of water repellency in pasture degradation. The areal coverage of Brachiaria brizantha grass tufts was measured as a proxy for net primary productivity of pastures under varying grazing pressures, and was also found to be correlated with hydrophobicity (R2=0.38; p=0.06). Surprisingly, soil water repellency was found to increase for increases in B. brizantha coverage. This may be due to the increased hydrophobicity-inducing potential of a pasture with greater biomass. While pasture soils were found to be generally compacted with bulk density (0-5 cm) ranging from 1.31 to 1.52, the relationship between hydrophobicity and surface soil compaction is non-significant. Spatial variability of soil water repellency was high at both meso- and micro-scales, with hydrophilic point measurements (MED < 1.0 N) scattered through generally hydrophobic soil. Dissipation over time of soil water repellency is consistent with hydrophobicity theory.

Johnson, M. S.; Lehmann, J.; Fernandes, E. C.

2002-12-01

78

Hygrometric Measurement of Soil Water Potential  

NASA Astrophysics Data System (ADS)

Knowledge of soil water potential as a function of water content is required to make unsaturated flow and transport predictions. Although numerous methods are available to measure soil water potential, they are largely difficult and time consuming procedures. The goal of the research is to develop a hygrometric method that will perform satisfactorily with minimal required hardware or technician time. The volume of a drop of saline water will change due to evaporation or condensation until its salinity, and hence osmotic potential, is equal to the water potential in the adjacent gas phase. This relationship is exploited by our method to measure soil moisture potential. To begin, a drop of KCl solution with known mass and KCL concentration is placed adjacent to a soil sample with known water content inside a hermetically sealed container. The mass of the KCl drop is recorded over time with an electronic balance. As thermodynamic equilibrium is achieved, the mass of water within the KCl drop changes until its osmotic potential is equal to the capillary potential of water within the soil sample. After the mass of the KCl drop reaches equilibrium, the KCl concentration is calculated, which enables direct determination of the water potential within the soil sample. Unlike transient hygrometric measurements of water potential using psychrometers, no calibration is required.

Butler, C. D.; Tyner, J. S.

2004-12-01

79

Water potential in nonrigid unsaturated soil-water medium  

NASA Astrophysics Data System (ADS)

This paper presents a development of water potential functions for a dual porosity nonrigid aggregated soil medium defined and characterized by its characteristic shrinkage curve. Fractal and thermodynamic approaches to modeling soil water potential are evaluated using simultaneous and continuously measured soil shrinkage and tensiometric curves on a standard laboratory soil sample. Water potential relationships are developed and analyzed for five Ivory Cost soils with clay content ranging from 10 to 50%. Analysis of modeled and observed results showed that the tensiometric curve, for its entire range of measurement, is directly linked to the interped water pool. The tensiometric curve, which is a function of the interped water pool, was modeled using both the fractal and the thermodynamical equations. Fits to the measured tensiometric curves were very well. This study demonstrates the link between the tensiometric curve with some of the pedostructure (soil-water medium) variables and parameters determined by the shrinkage curve, which leads to physically based equations of soil water potential. An interpretation of the origin of the swelling pressure inside and outside the primary peds and of the resulting suction pressure in unsaturated aggregated soils is proposed and discussed. This interpretation explains the link between the generalized Low's [1979] equation for the thermodynamic properties of the hydration layers of water surrounding particles in primary peds and the equations given by Berezin et al. [1983] for the swelling and the suction pressures in unsaturated aggregates.

Braudeau, Erik; Mohtar, Rabi H.

2004-05-01

80

Polymer-water interaction studies  

NASA Astrophysics Data System (ADS)

Polymer water interactions were investigated. The following interactions were studied: (1) water absorption and desorption kinetics in EVA and PVB; (2) humidity dependence of electrical properties of EVA and PVB; (3) plasticizer effects in PVB; and (4) radiation effects in PVB and EVA.

Orehotsky, J.

1984-10-01

81

Predicting interactions between wetland vegetation and the soil-water and surface-water environment using diversity, abundance and attribute values  

Microsoft Academic Search

This study investigated the response of freshwater wetland vegetation to hydrological driving factors by assessing collective\\u000a vegetation variables, traits of dominant plant populations and hydrological and hydrochemical variables, repeat-sampled within\\u000a wetland sites across Scotland and northern England. Sampling was conducted at 55 permanent sample stations located along 11\\u000a independent transects. Eco-hydrological interactions were investigated using a regression-based modelling approach. Facets

M. P. Kennedy; K. J. Murphy; D. J. Gilvear

82

Predicting interactions between wetland vegetation and the soil-water and surface-water environment using diversity, abundance and attribute values  

Microsoft Academic Search

This study investigated the response of freshwater wetland vegetation to hydrological driving factors by assessing collective\\u000a vegetation variables, traits of dominant plant populations and hydrological and hydrochemical variables, repeat-sampled within\\u000a wetland sites across Scotland and northern England. Sampling was conducted at 55 permanent sample stations located along 11\\u000a independent transects. Eco-hydrological interactions were investigated using a regression-based modelling approach. Facets

M. P. Kennedy; K. J. Murphy; D. J. Gilvear

2006-01-01

83

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)

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.

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

2012-09-01

84

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)

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.

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

2013-07-01

85

Interaction between Diclofenac and Soil Humic Acids  

Microsoft Academic Search

The interaction between the non-steroidal anti-inflammatory drug diclofenac and standard humic acids (HAs) in bulk solution was studied using two complementary analytical methods: UV-Visible spectroscopy and square wave voltammetry. The observed UV-Vis spectra and Ip\\/V curves suggested that, at our experimental conditions, albeit both substances being negatively charged at pH 6.5, interaction between the pharmaceutical and the soil humic acids

Alja Margon; Arnold Pastrello; Davide Mosetti; Pierpaolo Cantone; Liviana Leita

2009-01-01

86

Fly ash dynamics in soil-water systems  

SciTech Connect

Studies regarding the effluents and coal ashes (or fly ash) resulting from coal burning are numerous, but their disposal and interactions with the soil and water systems and their detailed environmental impact assessment with concrete status reports on a global scale are scanty. Fly ash dynamics in soil and water systems are reviewed. After detailing the physical composition of fly ash, physicochemical changes in soil properties due to fly ash amendment are summarized. Areas covered include texture and bulk density, moisture retention, change in chemical equilibria, and effects of fly ash on soil microorganisms. Plant growth in amended soils is discussed, as well as plant uptake and accumulation of trace elements. In order to analyze the effect of fly ash on the physicochemical properties of water, several factors must be considered, including surface morphology of fly ash, pH of the ash sluice water, pH adjustments, leachability and solubility, and suspended ash and settling. The dynamics of fly ash in water systems is important due to pollution of groundwater resources from toxic components such as trace metals. Other factors summarized are bioaccumulation and biomagnification, human health effects of contaminants, and the impact of radionuclides in fly ash. Future research needs should focus on reduction of the environmental impact of fly ash and increasing utilization of fly ash as a soil amendment. 110 refs., 2 figs., 10 tabs.

Sharma, S.; Fulekar, M.H.; Jayalakshmi, C.P. (Energy and Environment Group, New Delhi (India))

1989-01-01

87

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...

88

Phase Boundary Water in Frozen Soils.  

National Technical Information Service (NTIS)

It is now widely recognized that water a phase boundaries plays an important and in some cases the dominant role governing heat and mass transport, electrical conduction, transmission of compression waves and other processes of importance in frozen soils....

D. M. Anderson

1970-01-01

89

SW—Soil and Water  

Microsoft Academic Search

By constructing an artificial perched watertable which is a horizontal and cylindrical soil cavity with a diameter of 3 m and a height of 0·3 m, at a depth of about 0·8 m from the soil surface in the fields, it was envisaged that the runoff caused in the summer could preferably be held in this layer and, hence, the

K. Araya; G. Guo

2002-01-01

90

Effects of soil water content on soil respiration in forests and cattle pastures of eastern Amazonia  

Microsoft Academic Search

The effect of soil water content on efflux of CO2 from soils has been described by linear, logarithmic, quadratic, and parabolic functions of soil water expressed as matric potential, gravimetric and volumetric water content, water holding capacity, water-filled pore space, precipitation indices, and depth to water table. The effects of temperature and water content are often statistically confounded. The objectives

Eric A. Davidson; Louis V. Verchot; J. Henrique Cattânio; Ilse L. Ackerman; J. E. M. Carvalho

2000-01-01

91

Use of the soil freezing charactertistic to model frozen and unfrozen soil water dynamics  

Technology Transfer Automated Retrieval System (TEKTRAN)

The soil moisture characteristic is critical to accurately simulate soil water dynamics but is difficult to measure, particularly for the dry regions of the curve. The relation between freezing soil temperatures, soil water potential and liquid water content, termed the soil freezing characteristic...

92

Soil porous system changes quantified by analyzing soil water retention curve modifications  

Microsoft Academic Search

Soil water retention curves (SWRCs) relate soil water pressure head (h) to soil water content (?) and can also be used to find information regarding soil pore distribution. To analyze SWRCs in relation to pore size distribution (PSD), changes due to wetting and drying (W–D) cycles were studied in three different tropical soils (Geric Ferralsol, GF; Eutric Nitosol, EN; Rhodic

Luiz F. Pires; Fabio A. M. Cássaro; Klaus Reichardt; Osny O. S. Bacchi

2008-01-01

93

Derivation of soil water capacity parameters from standard soil texture information for Bulgarian soils  

Microsoft Academic Search

Prediction of total porosity and volumetric water content at field capacity, and permanent wilting point have been evaluated for their possible applicability to supply important missing soil information. The results were compared to the experimental data from Bulgaria. Also the possibility is explored to convert soil particle size distribution data as determined according to the soil standards in Bulgaria to

Boyko Kolev; Svetla Rousseva; Dimitar Dimitrov

1996-01-01

94

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

NASA Astrophysics Data System (ADS)

Surface characteristics of soils are one of the main factors controlling processes at the soil-water interface like wetting, sorption or dissolution processes and, thereby, have a high impact on natural soil functions like habitat, filter, buffer, storage and transformation functions. Since surface characteristics, like wettability or repellency, are not static soil properties but continuously changing, the relevant processes and mechanisms are in the focus of the presented study. These mechanisms help to gain further insight into the behaviour of soil and its dynamics under changing environmental conditions. The influence of water content, relative air humidity and drying temperature on soil water repellency has been investigated in many studies. In contrast, few studies have systematically investigated the relationship between soil water repellency (SWR) and soil pH. Several studies found alkaline soils to be less prone to SWR compared to acidic soils (e.g., Cerdà, and Doerr 2007; Mataix-Solera et al. 2007). Furthermore, SWR has been successfully reduced in acidic soils by increasing soil pH via liming (e.g., Karnok et al. 1993; Roper 2005). However, SWR has also been reported in calcareous soils in the Netherlands (Dekker and Jungerius 1990), California, USA (Holzhey 1968) and Spain (Mataix-Solera and Doerr 2004). The hypothesis that the pH may control repellency via changes in the variable surface charge of soil material has not yet been tested. Previously it has been shown that it is necessary to eliminate the direct influence of changes in soil moisture content so that the unique relationship between pH and SWR can be isolated (Bayer and Schaumann 2007). A method has been developed which allows adjustment of the pH of soils with low moisture content via the gas phase with minimal change in moisture content. The method was applied to 14 soil samples from Germany, Netherlands, the UK and Australia, using the water drop penetration time (WDPT) as the indicator of SWR. Sessile drop and Wilhelmy plate contact angles (CAsess and CAwpm resp.) were measured on the four samples from Germany and the data correlated with those of WDPT. The titratable surface charge of these four soils was measured at selected pH values using a particle charge detector (PCD). Changes in SWR with soil pH were found to be influenced by the density and type of sites able to interact with protons at the available surfaces of organic and mineral materials in soil. The maximum SWR occurred for soil at natural pH and where the charge density was minimal. As pH increased, negative surface charge increased due to deprotonation of sites and WDPT decreased. Two types of behaviour were observed: Those in which (i) WDPT shortened with decreasing pH and ii) WDPT was sensibly constant with decreasing pH. The data suggest that the availability and relative abundance of proton active sites at mineral surfaces, and those at organic functional groups influence the behaviour. Bayer, J. V. and G. E. Schaumann (2007). Hydrological processes 21(17): 2266 - 2275. Cerdà, A. and S. H. Doerr (2007). Hydrological Processes 21(17): 2325-2336. Dekker, L. W. and P. D. Jungerius (1990). Dunes of the European coasts, Catena-Verlag. 18: 173-183. Holzhey, C. S. (1968). Symposium on water repellent soils, Riverside, California. Karnok, K. A., E. J. Rowland, et al. (1993). Agronomy Journal 85(5): 983-986. Mataix-Solera, J., V. Arcenegui, et al. (2007). Hydrological Processes 21(17): 2300-2309. Mataix-Solera, J. and S. H. Doerr (2004). Geoderma 118(1-2): 77-88. Roper, M. M. (2005). Australian Journal of Soil research 43: 803-810.

Diehl, Doerte

2010-05-01

95

Water Transfer from Soil to the Atmosphere as Related to Soil Properties, Plant Characteristics and Weather.  

National Technical Information Service (NTIS)

A laboratory technique is described for independent measurement of the total soil water potential and its components, based on the principles of the soil psychrometer and the porous plate apparatus. Only a negligible quantity of soil water is displaced. S...

S. L. Rawlins E. M. Cullen F. N. Dalton W. R. Gardner G. J. Hoffman

1967-01-01

96

Soil-water relations of shallow forested soils during flash floods in ...  

Treesearch

Other flash floods struck seven forested sections of the state in August. ... overland flow occurred only when soils became saturated by infiltrated water draining ... Soil-water relations of shallow forested soils during flash floods in West Virginia.

97

Soil water retention curve analysis using radial basis function network  

Microsoft Academic Search

The soil water retention curve (SWRC) shows the relationship between soil suction pressure and water content, which is one of the key hydraulic properties to study the flow and solute transports in unsaturated zone. A radial basis function network (RBFN) was developed to describe the SWRC with the observed soil suction pressure and simultaneous soil water content derived from laboratory

Jin Gao; Yanfeng Liu

2010-01-01

98

Net radiation — soil heat flux relations as influenced by soil water content variations  

Microsoft Academic Search

Net radiation, soil heat flux, incoming and reflected solar radiation, and soil water content were measured during several clear day periods following approximate 10-cm applications of water to loam soils at Phoenix, Arizona, and at Sidney, Montana. The regression of soil heat flux on net radiation changed significantly as the soil dried, with the difference between them being a linear

S. B. Idso; J. K. Aase; R. D. Jackson

1975-01-01

99

Soil water and temperature regimes in drip and sprinkler irrigation, and implications to soybean emergence  

Microsoft Academic Search

Irrigation has long been used in agriculture as a primary means of water management. It is well known that water distributions in the soil differ depending on the methods of irrigation. However, it is less clear how soil thermal regimes would change over time and space when irrigation methods are different. A field study was conducted to investigate the interactive

D. Wang; M. C. Shannon; C. M. Grieve; S. R. Yates

2000-01-01

100

THE BALANCED ENTROPY INDEX TO CHARACTERIZE SOIL TEXTURE FOR SOIL WATER RETENTION ESTIMATION  

Technology Transfer Automated Retrieval System (TEKTRAN)

Pedotransfer procedures are often used to estimate soil hydraulic properties from soil basic data available from soil surveys. Soil particle size distribution, or texture, is known to be a leading soil property affecting soils' ability to retain and transmit water and solutes. A substantial effort h...

101

Controlled experimental soil organic matter modification for study of organic pollutant interactions in soil.  

PubMed

Interactions of organic pollutants with soil organic matter can be studied by adsorption of the pollutants on well-characterized soil samples with constant mineralogy but different organic matter compositions. Therefore, the objectives of the current study are establishing a set of different, well-characterized soil samples by systematic modifications of their organic matter content and molecular composition and prove these modifications by advanced complementary analytical techniques. Modifications were done by off-line pyrolysis and removal/addition of hot-water extracted organic fraction (HWE) from/to the original soil sample. Both pyrolysis-field ionization mass spectrometry (Py-FIMS) and synchrotron-based C- and N- X-ray absorption near-edge structure spectroscopy (XANES) were applied to investigate the composition of the soil organic matter. These complementary analytical methods in addition to elemental analysis agreed in showing the following order of organic matter contents: pyrolyzed soil residuesoil+3 HWE<soil+6 HWEsoil sample increases the relative proportions of carbohydrates, N-containing heterocyclic compounds and peptides, and decreases the relative proportions of phenols, lignin monomers and dimers, and lipids. The most abundant organic compound classes in the pyrolyzed sample are aromatics, aliphatic nitriles, aldehydes, five- and six-membered N-containing heterocyclic compounds, and aliphatic carboxylic acids. It can be expected that removal or addition of HWE, that mimic biomass inputs to soil or soil amendments, change the binding capacity for organic pollutants less intensively than heat impact, e.g. from vegetation burning. It will be possible to interpret kinetic data on the pollutants adsorption by these original and modified soil samples on the basis of the bond- and element-specific speciation data through C-XANES and N-XANES and the molecular-level characterization through Py-FIMS. Finally, this combination of analytical techniques can be recommended for similar problems that require characterizing the bulk, non-extracted SOM instead of pre-selected compounds or compound classes. PMID:23137980

Ahmed, Ashour A; Kühn, Oliver; Leinweber, Peter

2012-11-06

102

Macropores and water flow in soils revisited  

NASA Astrophysics Data System (ADS)

The original review of macropores and water flow in soils by Beven and Germann is now 30 years old and has become one of the most highly cited papers in hydrology. This paper attempts to review the progress in observations and theoretical reasoning about preferential soil water flows over the intervening period. It is suggested that the topic has still not received the attention that its importance deserves, in part because of the ready availability of software packages rooted firmly in the Richards domain, albeit that there is convincing evidence that this may be predicated on the wrong experimental method for natural conditions. There is still not an adequate physical theory linking all types of flow, and there are still not adequate observational techniques to support the scale dependent parameterizations that will be required at practical field and hillslope scales of application. Some thoughts on future needs to develop a more comprehensive representation of soil water flows are offered.

Beven, Keith; Germann, Peter

2013-06-01

103

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

Microsoft Academic Search

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

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

2009-01-01

104

Battelle completes three-year study of pipe-soil interaction  

SciTech Connect

It has been recognized in recent years that understanding pipe-soil interaction is a key aspect of designing pipelines and risers for deep water and severe operating conditions. Incorrect prediction of pipe-soil interaction may lead to excessive pipeline movement and overstressing of the lower pipeline riser elbow and other key components. Unsafe designs may result from a lack of understanding of this interaction. Battelle's Petroleum Technology Center in Houston, Texas, has completed a three-year study of offshore pipe-soil interaction and its impact on pipeline and riser design. This article reviews the conduct and results of the study.

Not Available

1984-09-01

105

Using High-Resolution Soil Moisture Data to Assess Soil Water Dynamics in the Vadose Zone  

Microsoft Academic Search

ditions and soil management practices can be enhanced by monitoring volumetric soil water content in near- Infiltration and water flow in soils are highly transient processes, continuous real time. Time domain reflectometers and but may be estimated from high frequency measurements of soil water capacitance probes are two instrumental methods being content. The objectives of our study were to assess

James L. Starr; Dennis J. Timlin

2004-01-01

106

Using soil freezing characteristics to model multi-season soil water dynamics  

Technology Transfer Automated Retrieval System (TEKTRAN)

The soil moisture characteristic relation is critical to accurately simulate soil water dynamics but is difficult and time consuming to measure, particularly for the dry regions of the curve. The relation between freezing soil temperatures, soil water potential and liquid water content, termed the ...

107

Hillslope scale temporal stability of soil water storage in diverse soil layers  

NASA Astrophysics Data System (ADS)

Analysed soil water storage (SWS) temporal stability in three layers on two hillslopes.Spatial variation in mean SWS increased with increasing soil depth.At greater depths, soil water storage tended to be more temporally stable.A representative site can estimate mean soil water storage on a hillslope.Strong temporal stability due to texture, organic carbon, elevation, vegetation.

Jia, Xiaoxu; Shao, Ming’an; Wei, Xiaorong; Wang, Yunqiang

2013-08-01

108

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

ERIC Educational Resources Information Center

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,…

Miller, Larry E.

109

Water repellency and critical soil water content in a dune sand  

Microsoft Academic Search

Assessments of water repellency of soils are commonly made on air-dried or oven-dried samples, without considering the soil water content. The objectives of this study were to examine the spatial and temporal variability of soil water content, actual water repellency over short distances, and the variations in critical soil water contents. Between 22 April and 23 November 1999, numerous samples

Louis W. Dekker; Stefan H. Doerr; Klaas Oostindie; Apostolos K. Ziogas; Coen J. Ritsema

2001-01-01

110

Nutrient and temperature interactions in bioremediation of cryic soils  

Microsoft Academic Search

Low temperatures and lack of available nutrients often limit the rate of microbial petroleum hydrocarbon degradation in contaminated cryic soils. Proper management of both these parameters may increase microbial respiration in such soils. Interactions between nutrient level and temperature could impact management decisions for both factors, but these interactions have not previously been adequately described. Petroleum-contaminated soils from two Alaskan

James Walworth; Joan Braddock; Craig Woolard

2001-01-01

111

Enhancing Green Water in Soils of South Asia  

Microsoft Academic Search

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,

M. S. Kahlon; R. Lal

2011-01-01

112

Experimental Investigation on Excess Pore Water Pressure in Soft Soil-Foundations under Minor Shocks  

Microsoft Academic Search

? Abstract—In this study, shaking table tests are performed to investigate the behavior of excess pore water pressure in different soft soil-foundations of soil-structure interaction (SSI) system. The variation of the behaviors under cycled minor shock is observed. Moreover, The generation and variation mechanism of excess pore water pressure under earthquake excitation in different soft soil- foundations are analyzed and

Zhiying Zhang; Chongdu Cho; Qiang Pan; Xilin Lu

2009-01-01

113

Intermolecular interaction in water hexamer.  

PubMed

The origin of the intermolecular interaction, especially the many-body interaction, in eight low-lying water hexamer structures (prism, cage, book-1, book-2, cyclic-chair, bag, cyclic-boat-1, and cyclic-boat-2) is unraveled using the localized molecular orbital energy decomposition analysis (LMO-EDA) method at the second-order Møller-Plesset perturbation (MP2) level of theory with a large basis set. It is found that the relative stabilities of these hexamer structures are determined by delicate balances between different types of interaction. According to LMO-EDA, electrostatic and exchange interactions are strictly pairwise additive. Dispersion interaction in these water hexamer structures is almost pairwise additive, with many-body effects varying from -0.13 to +0.05 kcal/mol. Repulsion interaction is roughly pairwise additive, with many-body effects varying from -0.84 to -0.62 kcal/mol. Polarization interaction is not pairwise additive, with many-body effects varying from -13.10 to -8.85 kcal/mol. PMID:20932059

Chen, Yiming; Li, Hui

2010-11-01

114

SOIL WATER CHARACTERISTIC ESTIMATES BY TEXTURE AND ORGANIC MATTER FOR HYDROLOGIC SOLUTIONS.  

Technology Transfer Automated Retrieval System (TEKTRAN)

Hydrologic analyses often involve the evaluation of soil water infiltration, conductivity, storage, and plant-water relationships. To define the variable soil water effects requires estimating soil water relationships for water potential and hydraulic conductivity which depend on soil characteristic...

115

The Impact of Soil Water Repellency on Hydrological Properties of Soil, the Plant Growing Environment, Irrigation Efficiency and Water Consumption  

NASA Astrophysics Data System (ADS)

Soil water repellency causes at least temporal changes in the hydrological properties of a soil. These changes, among other things, often result in suboptimal growing conditions, reduced crop performance, and/or increased irrigation requirements. Water repellency in soil is more wide spread than previously thought and has been identified in many soil types under a wide array of climatic conditions and cropping systems worldwide. (Dekker et al., 2005) The reduction or loss of soil wettability caused by soil water repellency leads to drastically different hydrological behavior (Dekker et al. 2009), and reduces the ability of the soil to function as expected. Consequences of soil water repellency include increased runoff and preferential flow, reduced plant available water, reduced irrigation efficiency, suboptimal crop performance, increased requirement for water and other inputs, and increased potential for non-point source pollution. (Dekker et al., 2001) This presentation consolidates information on basic hydrological and soil system functions as they relate to the plant growth environment, irrigation efficiency and water conservation, and shows the differences between what happens in soils affected by varying levels of soil water repellency compared to wettable soils or soils where soil surfactants have been used to restore/optimize wettability. The impact on irrigation efficiency and the plant growth environment is also discussed. The conclusion is that the impact of soil water repellency compromises hydrological properties and the plant growth environment in a wider range of conditions than previously recognized and, therefore, deserves consideration in the management of soil and water in crop systems.

Moore, Demie; Kostka, Stanley; Boerth, Thomas; McMillan, Mica; Ritsema, Coen; Dekker, Louis; Oostindie, Klaas; Stoof, Cathelijne; Wesseling, Jan

2010-05-01

116

Effect of soil water table on soil respiration in a riparian forest of northeast Spain.  

NASA Astrophysics Data System (ADS)

Soil respiration is a major component in ecosystem carbon cycle and is strongly affected by soil water content. Soil respiration consists of autotrophic and heterotrophic respiration, which may have different sensitivities toward soil water content. The objectives of this study are: (1) to analyze the seasonal variation in soil water table and soil respiration in a Mediterranean riparian forest. (2) To examine difference in soil respirations of tree species. We measured the soil respiration rate along the soil water table with 5 transects of three tree species. Soil respiration rate decreased significantly from riverside to middle hill and showed clearly seasonality. Soil respiration rate also showed significantly different among tree species. Heterotrophic respiration rate contributed to the soil respiration rate from 48% to 95% depends on season and species.

Chang, Chao-Ting; Sperlich, Dominik; Gracia, Carlos; Sabaté, Santiago

2013-04-01

117

Interactions of Azospirillum spp. in soils: a review  

Microsoft Academic Search

This review summarizes and discusses the current knowledge and the, as yet, unanswered questions on the interactions of Azospirillum spp. in bulk soil (but not in the rhizosphere). It contains sections on the isolation of these bacteria from tropical to\\u000a temperate soils, and on their short- and long-term persistence in bulk soil. The interactions of these bacteria with soil\\u000a particles

Y. Bashan

1999-01-01

118

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...

119

Evaluation of different field methods for measuring soil water infiltration  

Microsoft Academic Search

Soil infiltrability, together with rainfall characteristics, is the most important hydrological parameter for the evaluation and diagnosis of the soil water balance and soil moisture regime. Those balances and regimes are the main regulating factors of the on site water supply to plants and other soil organisms and of other important processes like runoff, surface and mass erosion, drainage, etc,

Ildefonso Pla-Sentís; Francisco Fonseca

2010-01-01

120

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

NASA Astrophysics Data System (ADS)

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

Jackisch, Conrad; Zehe, Erwin

2013-04-01

121

Soil organic matter–metal interactions in Chilean volcanic soils under different agronomic management  

Microsoft Academic Search

The organic matter existing in volcanic soils must be investigated not only in quantity, but also in quality in order to understand its role in soils and thus ensure adequate levels of stable organic polymers contributing to soil humification.The meaningful contribution proposed by this investigation is based on the study of the interaction of soil organic matter (SOM) in its

Wendy Heredia; Pedro Peirano; Gilda Borie; María Aguilera

2002-01-01

122

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

Microsoft Academic Search

The role of vegetation and soil micro flora and fauna interaction during soil formation was studied in post mining sites in Czech Republic, Germany and USA. Vegetation and character of substrate substantially effect, micro flora, namely fungal bacterial ration, fauna composition and resulting microstructure of soil. Plants that bring more nitrogen in to the system support larger biomass of soil

J. Frouz

2009-01-01

123

Movement and Storage of Water in North Carolina Soils.  

National Technical Information Service (NTIS)

The most important soil physical properties affecting the movement and storage of water in soils are given, including analyses for bulk density, total porosity, pore-size distribution, total and available water-holding capacity and hydraulic conductivity....

J. F. Lutz

1970-01-01

124

The Impact of Soil Water Repellency on Hydrological Properties of Soil, the Plant Growing Environment, Irrigation Efficiency and Water Consumption  

Microsoft Academic Search

Soil water repellency causes at least temporal changes in the hydrological properties of a soil. These changes, among other things, often result in suboptimal growing conditions, reduced crop performance, and\\/or increased irrigation requirements. Water repellency in soil is more wide spread than previously thought and has been identified in many soil types under a wide array of climatic conditions and

Demie Moore; Stanley Kostka; Thomas Boerth; Mica McMillan; Coen Ritsema; Louis Dekker; Klaas Oostindie; Cathelijne Stoof; Jan Wesseling

2010-01-01

125

Modeling of soil deformation and water flow in a swelling soil  

Microsoft Academic Search

Soil deformation and unsaturated transient water flow in swelling soil on a laboratory scale is predicted using a one-dimensional numerical model. The model is based on a soil water flow equation and extended to soil deformation using Lagrangian description (LD). The specific features of the model are inclusion of an overburden component in the total potential of the flow equation,

D. J Kim; R Angulo Jaramillo; M Vauclin; J Feyen; S. I Choi

1999-01-01

126

Effects of temperature, soil water status, and soil type on swine slurry nitrogen transformations  

Microsoft Academic Search

Manure N dynamics are affected by manure characteristics, soil factors, and environmental conditions. An incubation experiment was conducted to assess the relationship of these factors. The effects of temperature (11, 18, and 25°C), soil texture (three soils, silt loam to sandy loam), and soil water status (constant at 60% water filled pore space, WFPS, and fluctuating between 30% and 60%

T. S. Griffin; C. W. Honeycutt; Z. He

2002-01-01

127

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

Microsoft Academic Search

Soil water content strongly affects permafrost dynamics by changing the soil thermal properties. However, the movement of liquid water, which plays an important role in the heat transport of temperate soils, has been under-represented in boreal studies. Two different heat transport models with and without convective heat transport were compared to measurements of soil temperatures in four boreal sites with

Zhaosheng Fan; Jason C. Neff; Jennifer W. Harden; Tingjun Zhang; Hugo Veldhuis; Claudia I. Czimczik; Gregory C. Winston; Jonathan A. O'Donnell

2011-01-01

128

WATER AS A REAGENT FOR SOIL REMEDIATION  

SciTech Connect

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.

Indira S. Jayaweera; Jordi Diaz-Ferraro

2000-02-28

129

Climate Change Impacts on Soil and Water Conservation  

Microsoft Academic Search

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

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

2007-01-01

130

Estimation of Areal Soil Water Content through Microwave Remote Sensing  

Microsoft Academic Search

In this thesis the use of microwave remote sensing to estimate soil water content is investigated. A general framework is described which is applicable to both passive and active microwave remote sensing of soil water content. The various steps necessary to estimate areal soil water content are discussed through literature review, laboratory experimental results and results of extensive field experimental

Oevelen van P. J

2000-01-01

131

Sensible heat observations reveal soil-water evaporation dynamics  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

132

Occurrence of soil water repellency in arid and humid climates  

Microsoft Academic Search

Soil water repellency generally tends to increase during dry weather while it decreases or completely vanishes after heavy precipitation or during extended periods with high soil water contents. These observations lead to the hypothesis that soil water repellency is common in dry climates and rare in humid climates. The study objective is to test this hypothesis by examining the occurrence

D. F. Jaramillo; L. W. Dekker; C. J. Ritsema; J. M. H. Hendrickx

2000-01-01

133

Interactive Soils Information System. Users Manual.  

National Technical Information Service (NTIS)

This report describes and provides basic instructions for using the Soils Information Retrieval System (SIRS), which was designed for efficient retrieval, analysis, and use of soils data from the U.S. Department of Agriculture's Soil Conservation Service ...

W. D. Goran

1983-01-01

134

Soil water regime and runoff formation in a small catchment  

NASA Astrophysics Data System (ADS)

The precipitation - runoff transformation is realised in two steps in a small catchment. In the first step, the soil behaves as a reservoir, filled with rainwater, and emptied by the water uptake for plant transpiration. In the course of the vegetation season, the soil water content oscillates between two typical values - maximum and minimum. The maximum value corresponds to such soil water content, where the infiltration of further rain calls percolation of water to the drainage layer. The minimum value corresponds to such soil water content, where insufficient soil moisture renders a further withdrawal of water for plant transpiration impossible. This feedback is a source of complicated problems concerning the water and energy transport in the soil - plant - atmosphere system. Thus the soil water regime is a very complex matter. Two phases of soil water regime can be distinguished: the percolation phase and the accumulation phase. In the percolation phase, the rainwater percolates through the soil into the drainage layer. In the accumulation phase, the rainwater accumulates in the soil and does not outflow into the drainage layer. The soil profile can attenuate or amplify the rainfall pulses during their transformation to the outflow below the soil profile. If the soil water content is lower than the threshold value, the rainfall pulses can be suppressed down to zero. If the soil profile contains more water, the soil does not attenuate the rainfall pulses, it can even amplify them by adding the released soil water. Support from the Grant Agency of ASCR (Grants No. A30060001 and S2060104) and Ministry of Environment of the Czech Republic (Project No. VaV 610/3/00) is greatly acknowledged. Keywords: Catchment hydrology, soil water regime, rainfall - runoff relationship.

Tesar, M., , Sir; Prazak, J.; Lichner, L.

2003-04-01

135

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...

136

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...

137

DIVISION S-1—SOIL PHYSICS Modeling Soil Water Redistribution during Second-Stage Evaporation  

Microsoft Academic Search

practices such as irrigation scheduling (Lascano and Hatfield 1992; Chanzy and Bruckler, 1993; Bonsu, 1997). Calculating the dynamics of soil water content () near the surface Water evaporation from a soil surface can be divided and modeling soil water evaporation (Es) are critical for many agricul- into two stages: (i) the constant-rate stage in which Es tural management strategies. This

A. A. Suleiman; J. T. Ritchie

138

Estimating root zone soil water content using limited soils information and surface soil moisture data assimilation  

Microsoft Academic Search

The various hydrologic processes of infiltration, redistribution, drainage, evaporation, and water uptake by plants are strongly interdependent, as they occur sequentially or simultaneously. An important state variable that strongly influences the magnitude to which these rate processes occur is the amount of water present within the root zone, and in particular, the top few centimeters near the soil surface. Traditionally,

Gary Claude Heathman

2001-01-01

139

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

Microsoft Academic Search

Plants are big water movers and have a significant impact on soil water dynamics as well as on the global water cycle. Despite the relevance of root water uptake in terrestrial ecology, the movement of water from soil to roots still presents important open questions, e.g the following two. Which are the properties of the soil near the roots? And

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

2009-01-01

140

A numerical model of heat and water movement in furrow-sown water repellent sandy soils  

Microsoft Academic Search

Water repellent soils have thin layers of hydrophobic organic matter on the surfaces of soil particles. The hydrophobic organic matter makes these soils difficult to wet in opening rains after dry periods. This can cause losses of crop and pasture production and encourage land degradation by wind and water erosion. Wetting patterns in water repellent soils are irregular and incomplete,

Bangjie Yang; Paul S. Blackwell; David F. Nicholson

1996-01-01

141

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

Microsoft Academic Search

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 COâ assimilation.

E D Schulze

1986-01-01

142

Water movement through an experimental soil liner  

USGS Publications Warehouse

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.

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

1991-01-01

143

Predicting soil water, tile drainage, and runoff in a mole?tile drained soil  

Microsoft Academic Search

There has been considerable intensification of agriculture on mole?tile drained soils in New Zealand. Management techniques and tools are needed for predicting and understanding water and nutrient transport. While simple water balance models have been effective in estimating soil water deficit, such models cannot differentiate between the different water loss mechanisms. More complex water?transport models include the ability to predict

V. O. Snow; D. J. Houlbrooke; N. I. Huth

2007-01-01

144

Dynamics of soil water content in the rhizosphere  

Microsoft Academic Search

Water flow from soil to plants depends on the properties of the soil next to roots, the rhizosphere. Although several studies\\u000a showed that the rhizosphere has different properties than the bulk soil, effects of the rhizosphere on root water uptake are\\u000a commonly neglected. To investigate the rhizosphere’s properties we used neutron radiography to image water content distributions\\u000a in soil samples

Andrea Carminati; Ahmad B. Moradi; Doris Vetterlein; Peter Vontobel; Eberhard Lehmann; Ulrich Weller; Hans-Jörg Vogel; Sascha E. Oswald

2010-01-01

145

Partitioning of organic matter in soils: effects of pH and water\\/soil ratio  

Microsoft Academic Search

The effects of pH and water\\/soil ratio on the soil–water partitioning of soil organic matter (SOM) in 15 New Jersey soils were investigated. The dissolved organic carbon (DOC) concentration stabilized within 24 h. An increase in pH increased dissolution of soil organic matter. The ratio of UV absorbance at 465 nm to that at 665 nm (E4\\/E6 ratio) of the

Sun-Jae You; Yujun Yin; Herbert E Allen

1999-01-01

146

Effects of Soil Water on Soil Surface CO2 Fluxes and the Carbon Budget of a Deciduous Forest  

NASA Astrophysics Data System (ADS)

The CO2 flux from the soil surface is an important component of the carbon budget in a forest stand. The soil surface CO2 may contribute about 20 percent of the photosynthesis uptake by the forest with the remainder coming from the atmosphere. Since such a large fraction of the total CO2 flux above the forest canopy may originate in the soil, the contribution of soil surface CO2 flux must therefore be considered in using field measurements of CO2 fluxes to evaluate models for predicting the components of photosynthesis. The CO2 flux at the floor of a deciduous forest seems to depend on soil temperature, soil water content, amount of litter, and the photosynthesis capacity of the forest. An important way to understand these factors is to use fast response and accurate instrument to measure soil CO2 fluxes. We used a prototype soil chamber to measure soil CO2 fluxes at two locations in an oak forest in the NOAA-ATDD GEWEX flux tower network in TN, and the results from the measurement were used to evaluate the performance of a soil-plant-atmosphere model important as a gap- filling tool. Soil surface CO2 flux is the result of largely respiration by the soil biomass consisting of plant roots and dead plant materials. The respiration in vegetation environments depends on the capacity and types of vegetation, as well as on the mineralization of the organic matter by soil microbial activity, which provides nutrients for plant growth and development. In our case of the deciduous forest with large litter cover at floor below the canopy, CO2 flux may be produced by chemical reaction between rainwater and the top organic soil layer. During and immediately after rainfall, the CO2 dissolved in rainwater seems to be released from the warm soil relative to the rainwater. Similarly, CO2 may be released from the soil when rainwater displaces gas in the soil pore space. This physical interaction was observed at two flux tower sites in the oak forest reservation in Oak Ridge, TN. The soil chamber measurements reported strong increases in the hourly soil CO2 flux from low values of below 0.1 mg m-2 s-1 for dry soil conditions to values as high as 0.4 mg m-2 s-1 following rainstorm, suggesting that the soil CO2 flux is sensitive to soil water content. The fraction of the CO2 flux in the deciduous forest attributable to respiration seems to vary from 20 to 80 percent related to time of day and year and rainfall.

Wilson, T. B.; Meyers, T. P.; Heuer, M.

2007-12-01

147

Modelling soil anaerobiosis from water retention characteristics and soil respiration  

Microsoft Academic Search

Oxygen is a prerequisite for some and an inhibitor to other microbial functions in soils, hence the temporal and spatial distribution of oxygen within the soil matrix is crucial in soil biogeochemistry and soil biology. Various attempts have been made to model the anaerobic fraction of the soil volume as a function of structure, moisture content and oxygen consumption. Aggregate

Guy Schurgers; Peter Dörsch; Lars Bakken; Peter Leffelaar; Lars Egil Haugen

2006-01-01

148

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

USGS Publications Warehouse

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.

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

2010-01-01

149

Effects of Soil Structure Interaction on Strength Reduction Factors  

Microsoft Academic Search

In this study, strength reduction factors for SDOF systems of period range of 0.1-3.0s. with elastoplastic behavior are obtained for 20 earthquake motions recorded on soft soils considering soil structure interaction. Soil structure interacting systems are modeled with effective period, effective damping and effective ductility values differing from fixed-base case. For inelastic time history analyses, Newmark method for step by

M. Eser; C. Aydemir; I. Ekiz

2011-01-01

150

Influences affecting the soil-water characteristic curve  

Microsoft Academic Search

The soil-water characteristic curve (SWCC) is the primary partially saturated soil information as its behavior and properties can be derived from it. Although there have been many studies of unsaturated soils and the SWCC, there is still no combined constitutive model that can simulate soil characteristics accurately. In cases when hydraulic hysteresis is dominant (e.g. under cyclic loading) it is

ZHOU Jian; YU Jian-lin

2005-01-01

151

Quantifying nonisothermal subsurface soil water evaporation  

NASA Astrophysics Data System (ADS)

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

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

2012-11-01

152

On the influence of coarse fragments on soil water retention  

NASA Astrophysics Data System (ADS)

The classical determination of the soil water retention curve (SWRC) by measuring soil water content ? at different matric potentials ? using undisturbed soil samples is time consuming and expensive. Furthermore, undisturbed soil sampling can be an intricate task when coarse soil fragments (>2 mm) are present. The objective of this study was to test whether tension infiltrometry could be used to estimate the SWRC of stony soils and to investigate to what extent the coarse fragments affected the SWRC. Tension infiltrometer measurements were conducted at 44 sites with stony soils in arid Chile. Soil water retention curves obtained through inverse modeling were compared with laboratory-determined water retention (?, ?) data pairs. Differences were found to be small, confirming the applicability of the inverse modeling method. Rock fragments had a significant indirect influence on water retention for matric potentials higher than -0.30 kPa, which could be attributed to their direct influence on pore size distribution.

Baetens, J. M.; Verbist, K.; Cornelis, W. M.; Gabriels, D.; Soto, G.

2009-07-01

153

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

EPA Science Inventory

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

154

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

EPA Science Inventory

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

155

Effect of soil water osmotic potential on growth and water relationships in barley during soil water depletion  

Microsoft Academic Search

Barley plants (Hordeum distichum, L., cv. ‘Zita’) grown in a sandy soil in pots were adjusted during a pretreatment period of 5 days to three levels of soil water osmotic potential by percolating 61 of a nutrient solution with additional 0, 22.3 and 44.6 mM KCl. A drying cycle was then started and the plants were harvested when the soil

C. R. Jensen

1982-01-01

156

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 ...

157

Effect of extraction techniques on soil pore?water chemistry  

Microsoft Academic Search

The retention of contaminants in soil and overburden is often estimated using a solid\\/liquid partition coefficient, Kd, which lumps all the processes into an empirical value. Determination of this value in unsaturated porous media requires the separation of the pore water from the solid phase. Soil pore?water recovery and composition were investigated in three chemically and texturally different mineral soils

Marsha I. Sheppard; D. H. Thibault; P. A. Smith

1992-01-01

158

Water Drainage in Layered Soils. Laboratory Experiments and Numerical Simulation  

Microsoft Academic Search

Experimental results during first and second drainage in a vertical column of saturated layered soil were compared to those predicted from simulation. The sample was composed of a sandyloam soil overlying a fine sand. The soil water content was measured by using ?-ray absorption method (241Am) and the water pressure through tensiometers, arranged vertically along the column and connected to

M. Sakellariou-Makrantonaki

1997-01-01

159

Evaporation From a Bare Soil Evaluated Using a Soil Water Transfer Model and Remotely Sensed Surface Soil Moisture Data  

Microsoft Academic Search

Daily surface soil moisture data, obtained with a C band scatterometer on a bare soil, provide the upper boundary condition for a numerical soil water transfer model. The model uses an implicit finite difference scheme to solve the nonlinear Richards equation. The soil is represented by two layers differing in hydraulic conductivity. Following calibration by comparison of calculated and measured

L. Prevot; R. Bernard; O. Taconet; D. Vidal-Madjar; J. L. Thony

1984-01-01

160

Diurnal fluctuations of water and heat flows in a bare soil  

NASA Astrophysics Data System (ADS)

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

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

1998-11-01

161

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

NASA Astrophysics Data System (ADS)

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.

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

2013-08-01

162

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

Microsoft Academic Search

Surface characteristics of soils are one of the main factors controlling processes at the soil-water interface like wetting, sorption or dissolution processes and, thereby, have a high impact on natural soil functions like habitat, filter, buffer, storage and transformation functions. Since surface characteristics, like wettability or repellency, are not static soil properties but continuously changing, the relevant processes and mechanisms

Doerte Diehl

2010-01-01

163

Effects of tillage on soil microrelief, surface depression storage and soil water storage  

Microsoft Academic Search

Conservation of soil water is an important management objective for crop production in the semi-arid tropics where droughts are persistent. Identification of the best tillage methods to achieve this objective is thus imperative. The integrated effects of conservation tillage on soil micro topography and soil moisture on a sandy loam soil were evaluated. The field experiment consisted of five tillage

A. C Guzha

2004-01-01

164

Unsaturated water flow across soil aggregate contacts  

NASA Astrophysics Data System (ADS)

Unsaturated water flow through soil aggregates is controlled by the contacts between aggregates. The contacts are highly conductive when wet and become bottle-necks for flow when drained. We postulate that the hydraulic conductivity of the contacts is in first place determined by the water-filled contact area. The objective of this study was to measure and model the water-filled contact area and to relate it to the conductivity of a series of aggregates. We performed microscopic tomography of an aggregate pair equilibrated at different water potentials. By means of image analysis and a morphological pore network model, the water-filled contact area was calculated. We found that the aggregate surface is rough and the contact region contains macropores which are rapidly drained. As a consequence the water-filled contact area dramatically decreases as the water potential is diminished. We modeled this process by describing the aggregates as spheres covered by much smaller spheres representing the roughness. The water-filled contact was analytically calculated from this model. Knowing the water-filled contact area we up-scale the hydraulic conductivity of a series of aggregates. This is calculated as the harmonic mean of the contact and aggregate conductivities. The contact conductivity is calculated from the water-filled contact area. Near saturation the conductivity of a series of aggregates is close to the conductivity of a single aggregate, and, when further drained, it rapidly decreases as the water-filled contact area. The model matches the experimental data well.

Carminati, A.; Kaestner, A.; Lehmann, P.; Flühler, H.

2008-09-01

165

Outcomes of fungal interactions are determined by soil invertebrate grazers.  

PubMed

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

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

2011-09-19

166

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

Microsoft Academic Search

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

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

2011-01-01

167

Soil structures produced by tillage as affected by soil water content and the physical quality of soil  

Microsoft Academic Search

Tillage experiments were carried out in order to study the effect of water content on the aggregate size distribution produced by tillage, and to investigate the relationship between the soil structures produced by tillage and Dexter's index of soil physical quality, S. Tillage with a mouldboard plough was done on four different soils over a range of naturally occurring water

Thomas Keller; Johan Arvidsson; Anthony R. Dexter

2007-01-01

168

On the assessment of root and soil respiration for soils of different textures: interactions with soil moisture contents and soil CO2 concentrations  

Microsoft Academic Search

Estimates of root and soil respiration are becoming increasingly important in agricultural and ecological research, but there\\u000a is little understanding how soil texture and water content may affect these estimates. We examined the effects of soil texture\\u000a on (i) estimated rates of root and soil respiration and (ii) soil CO2 concentrations, during cycles of soil wetting and drying in the

Tjeerd J. Bouma; David R. Bryla

2000-01-01

169

Correction of cone index for soil water content differences in a coastal plain soil  

Microsoft Academic Search

Soil penetration resistance (cone index) varies with water content. The field variation of water content could mask treatment differences. The correction of cone index data to a single water content would help prevent this. We used equations from TableCurve™ software and from the literature to correct cone indices for differences in soil water contents. Data were taken from two field

W. J. Busscher; P. J. Bauer; C. R. Camp; R. E. Sojka

1997-01-01

170

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

Microsoft Academic Search

Accurate measurement and sampling of infiltration water from root zone are necessary to understand soil and groundwater contamination processes. The traditional instruments for sampling water leaching below the root zone cause divergence or bypass of the water flow around the instrument itself. That results in undesired soil water profile and inaccurate sampling. A suction controlled lysimeter, which consists of porous

N. Higashi; M. Inoue; Y. Mori

2003-01-01

171

Soil Water Components Based on Capacitance Probes in a Sandy Soil  

Microsoft Academic Search

availability to support optimal production and quality. The purpose of well-managed irrigation is to optimize Understanding soil water movement is needed to manage irrigation water spatial and temporal distribution, to promote crop to minimize water drainage, nutrient leaching below the root zone, and contamination of groundwater. We hypothesized that soil water growth and yield, and to enhance citrus economic re-

A. Fares; A. K. Alva

2000-01-01

172

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)

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.

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

2008-06-01

173

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...

174

PERMEABILITY OF SOILS TO FOUR ORGANIC LIQUIDS AND WATER  

EPA Science Inventory

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

175

Surface soil water content regimes: opportunities in soil science  

Microsoft Academic Search

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

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

1996-01-01

176

Estimating soil water retention curve in rhodic ferralsols from basic soil data  

Microsoft Academic Search

Determining soil water retention curve by field methods is expensive, laborious and time consuming. Several indirect methods have been developed to circumvent these setbacks. However, tropical soils have hardly benefited from these innovations. In this work, pedo-transfer functions (PTFs) and fractal analysis were used to predict the soil water characteristic curve of a Rhodic Ferralsol, collected from the three western

Mohamed Tarawally; Alicia del Valle; Mar??a Elena Ruiz

2002-01-01

177

Comparison of soil freezing curve and soil water curve data for Windsor sandy loam  

Microsoft Academic Search

Unfrozen water content as a function of temperature was measured in the laboratory using pulsed nuclear magnetic resonance (PNMR) for a Windsor sandy loam soil. The PNMR data were related to previously measured soil moisture retention data through the modified Clausius-Clapeyron equation, with suitable adjustment for surface tension. The transformed measured unfrozen water content data and the previously measured soil

Patrick B. Black; Allen R. Tice

1989-01-01

178

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

Microsoft Academic Search

Chemical analyses were performed on soil water extracted from two cores taken from a sandy calcareous soil near Delhi, Ontario. Calcite saturation is attained within the unsaturated zone over short distances and short periods of time, whereas dolomite undersaturation persists to the groundwater table. The progressive dissolution of dolomite by soil water, within the unsaturated zone, after calcite saturation is

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

1980-01-01

179

Verification of Ground Penetrating Radar for Soil Water Content Measuring  

NASA Astrophysics Data System (ADS)

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

Ermolaeva, O.; Zeiliguer, A.

2009-04-01

180

WATER AS A REAGENT FOR SOIL REMEDIATION  

SciTech Connect

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.

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

2001-03-29

181

Comparison of Soil Freezing Curve and Soil Water Curve Data for Windsor Sandy Loam,  

National Technical Information Service (NTIS)

Unfrozen water content as a function of temperature was measured in the laboratory using nuclear magnetic resonance (NMR) for a Windsor sandy loam soil. The data were related to previously measured soil moisture retention data through the modified Clapeyr...

A. R. Tice P. B. Black

1988-01-01

182

Hydrologic modeling of soil water storage in landfill cover systems  

SciTech Connect

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

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

1987-01-01

183

MODELING SOIL-WATER DISTRIBUTION OF AROMATIC AMINES IN WATER SATURATED SOIL SYSTEMS  

EPA Science Inventory

Research summarized in this report focuses on the abiotic interactions of aromatic amines with whole soils in aqueous systems. This work was initiated to improve our ability to predict the mobility of aromatic amines and their potential to contaminate groundwater, and to improve...

184

Using Entropy to Quantify Soil Structure from Water Retention and Texture Data  

NASA Astrophysics Data System (ADS)

Soil structure embodies complex interactions between particle sizes (texture) and environmental factors that lead to the formation of structural units of different sizes and shapes. Water retention curves of structured soils reflect those interactions on the distribution and connectivity of pores. The main hypothesis of this work is that a measure of soil structure is given by the entropic distance between pore systems resulting from the same particle size distribution arranged randomly (reference distribution) and in structural units. It was also hypothesized that such distance can be derived from water retention curves by assuming that the reference and structured pore systems follow lognormal distributions and that textural pore systems are the result of random arrangements of particles sizes. Reference pore size distributions were obtained from texture using an empirical model to convert from particle to pore size distributions. Soil clods were sampled in triplicate from each of 24 horizons of soil profiles under forest and agriculture management. Disturbed samples were collected to measure texture and organic matter. Soil clods were used to measure bulk density and water retention by the hanging column and pressure extractor methods (7 points between -0.3 to -10 kPa). Clods were then disturbed and water retention measured on packed soil (13 points between-0.3 to -1500 kPa on disturbed samples). Water retention data were fit with the Kosugi lognormal water retention model and the parameters from the model used to calculate the entropic or Kullback-Leibler Distance (KLD) between measured and reference pore size distributions. Values of KLD estimated from undisturbed clods were significantly (P<0.05) greater than the corresponding values estimated from the disturbed clods. The KLD measure of undisturbed soil exhibited distinctive trends with soil texture and aggregate size classes. The proposed measure could serve as a link between qualitative field description of soil structure and a quantitative measure of the effect of soil structure on pore size distribution.

Gimenez, D.; Yoon, S.-W.

2012-04-01

185

Seasonal Dynamics of Preferential Flow in a Water Repellent Soil  

Microsoft Academic Search

The temporal dynamic of water repellency in soils has a strong influence on water flow and the appearance of preferential flow paths at potentially water repellent sites. To quantify this effect, field inves- tigations were conducted at a sandy site near Berlin, Germany. A large number of soil samples were collected at 32 different times during a 3-yr period. Additionally,

K. Täumer; H. Stoffregen; G. Wessolek

2006-01-01

186

Can surfactants affect management of non-water repellent soils?  

Technology Transfer Automated Retrieval System (TEKTRAN)

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

187

Predicting the permeability function for unsaturated soils using the soil-water characteristic curve  

Microsoft Academic Search

The coefficient of permeability for an unsaturated soil is primarily determined by the pore-size distribution of the soil and can be predicted from the soil-water characteristic curve. A general equation, which describes the soil-water characteristic curve over the entire suction range (i.e., from 0 to 10 6 kPa), was proposed by the first two authors in another paper. This equation

D. G. Fredlund; ANQUING XING; Shangyan Huang

1994-01-01

188

Modeling distributions of water and dielectric constants around land mines in homogeneous soils  

NASA Astrophysics Data System (ADS)

Many sensors for landmine detection are affected by soil water content, temperature, electrical conductivity and dielectric constant. The most important of these is water content since it directly influences the three other properties. We model water distribution around antitank mines buried in a loam and loamy sand soil under the climatic conditions of Bosnia and Kuwait. In Kuwait the loam and loamy sand have mean soil water contents of about 16 and 7 volume percent, respectively; in Bosnia, the mane water contents are higher with means of 30 and 14 volume percent in the loam and loamy sand. As a result the soil dielectric constant in Kuwait varied from about 4 to 8 in the loamy sand and from 8 to 14 in the loam. In Bosnia the higher water contents result in a soil dielectric constant from 4 to 12 in the loamy sand and from 9 to 50 in the loam. Water contents below the landmine were sometimes higher than above it. The modeling result demonstrate that a solid water content regimes and the resulting distributions of soil dielectric constants around landmines are strongly affected by the interaction between climate, soil type, and landmine geometry.

Hendrickx, Jan M.; Das, Bhabani S.; Borchers, Brian

1999-08-01

189

The effect of soil surfactants on soil hydrological behavior, the plant growth environment, irrigation efficiency and water conservation  

Microsoft Academic Search

Soil water repellency causes at least temporal changes in the hydrological properties of a soil which result in, among other things, suboptimal growing conditions and increased irrigation requirements. Water repellency in soil is more widespread than previously thought and has been identified in many soil types under a wide array of climatic conditions worldwide. Consequences of soil water repellency include

D. Moore; S. J. Kostka; T. J. Boerth; M. A. Franklin; C. J. Ritsema; L. W. Dekker; K. Oostindie; C. R. Stoof; J. G. Wesseling

2010-01-01

190

Temperature dependence of the water retention curve for dry soils  

Microsoft Academic Search

Water retention curves (WRCs) are equivalent to water adsorption isotherms that display the soil water content as a function of water activity in the pore space. The use of water activity implies that pure (unbound) water at the given temperature is considered to be a reference state. In this study we measured the temperature dependence of WRCs for nine European

M. Schneider; K.-U. Goss

2011-01-01

191

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

NASA Astrophysics Data System (ADS)

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.

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

2009-04-01

192

SWBCM: a soil water balance capacity model for environmental applications in the UK  

Microsoft Academic Search

The paper presents a daily-time step, multi-horizon capacity model of soil-water balance (SWBCM—Soil Water Balance Capacity Model) suitable for ecological and environmental applications investigating the spatial and temporal variability of soil water content determined by changes in soil hydraulic conductivity, soil water storage capacity and the pathways of water movement through the soil and across soil types. SWBCM simulates soil

Samuel P. Evans; Thomas R. Mayr; John M. Hollis; Colin D. Brown

1999-01-01

193

A Comparison of Soil-Water Sampling Techniques  

NASA Astrophysics Data System (ADS)

The representativeness of soil pore water extracted by suction lysimeters in ground-water monitoring studies is a problem that often confounds interpretation of measured data. Current soil water sampling techniques cannot identify the soil volume from which a pore water sample is extracted, neither macroscopic, microscopic, or preferential flowpath. This research was undertaken to compare values of extracted suction lysimeters samples from intact soil cores with samples obtained by the direct extraction methods to determine what portion of soil pore water is sampled by each method. Intact soil cores (30 centimeter (cm) diameter by 40 cm height) were extracted from two different sites - a sandy soil near Altamonte Springs, Florida and a clayey soil near Centralia in Boone County, Missouri. Isotopically labeled water (O18? - analyzed by mass spectrometry) and bromide concentrations (KBr- - measured using ion chromatography) from water samples taken by suction lysimeters was compared with samples obtained by direct extraction methods of centrifugation and azeotropic distillation. Water samples collected by direct extraction were about 0.25 ? more negative (depleted) than that collected by suction lysimeter values from a sandy soil and about 2-7 ? more negative from a well structured clayey soil. Results indicate that the majority of soil water in well-structured soil is strongly bound to soil grain surfaces and is not easily sampled by suction lysimeters. In cases where a sufficient volume of water has passed through the soil profile and displaced previous pore water, suction lysimeters will collect a representative sample of soil pore water from the sampled depth interval. It is suggested that for stable isotope studies monitoring precipitation and soil water, suction lysimeter should be installed at shallow depths (10 cm). Samples should also be coordinated with precipitation events. The data also indicate that each extraction method be use to sample a different component of soil-pore water. Centrifugation can be used with success, particularly for efficient sampling of large areas. Azeotropic distillation is more appropriate when strict qualitative and quantitative data on sorption/desorption and various types of kinetic studies may be needed.

Tindall, J. A.; Figueroa-Johnson, M.; Friedel, M. J.

2007-12-01

194

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 ...

195

Interactions of low-level, liquid radioactive wastes with soils. 3. Interaction of waste radionuclides with soil from horizons of two soil series  

Microsoft Academic Search

We interacted a low-level radioactive waste with the respective horizons of two soils series, the Fuquay and the Fayette. The sorption of the soluble radionuclides was determined by batch reaction methods. Cesium-137 was sorbed to a very high degree, greater than 95 percent, and that degree of sorption was independent of both the soil horizon and the soil series. Uranium

W. L. Polzer; E. B. Fowler; E. H. Essington

1981-01-01

196

Predicting and mapping soil available water capacity in Korea  

PubMed Central

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

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

2013-01-01

197

Predicting and mapping soil available water capacity in Korea.  

PubMed

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

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

2013-04-23

198

Changes in Soil Water Storage in Winter Fallowed and Cover Cropped Soils  

Microsoft Academic Search

The use of winter cover crops to improve the productivity and sustainability of agroecosystems in California has increased during the last decade. Little information exists however, on water use by winter cover crops. This 3-year study was conducted in the Central Valley of California to quantify changes in water storage in winter fallowed and cover cropped soils. Soil water depletions

J. P. Mitchell; D. W. Peters; C. Shennan

1999-01-01

199

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

200

Interactions of Liquid Propellant/LP XM46 With Soils.  

National Technical Information Service (NTIS)

Development of an effective spill response plan for liquid propellant/LP XM46 (LP) required an understanding of the potential interactions between soil and the propellant. Studies were designed to characterize potential hazards of initial contact of LP wi...

J. C. Pennington C. B. Price D. Gunnison D. W. Rathburn T. E. Myers

1994-01-01

201

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

202

Subsurface And Surface Water Flow Interactions  

EPA Science Inventory

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

203

Difficulties in the evaluation and measuring of soil water infiltration  

NASA Astrophysics Data System (ADS)

Soil water infiltration is the most important hydrological parameter for the evaluation and diagnosis of the soil water balance and soil moisture regime. Those balances and regimes are the main regulating factors of the on site water supply to plants and other soil organisms and of other important processes like runoff, surface and mass erosion, drainage, etc, affecting sedimentation, flooding, soil and water pollution, water supply for different purposes (population, agriculture, industries, hydroelectricity), etc. Therefore the evaluation and measurement of water infiltration rates has become indispensable for the evaluation and modeling of the previously mentioned processes. Infiltration is one of the most difficult hydrological parameters to evaluate or measure accurately. Although the theoretical aspects of the process of soil water infiltration are well known since the middle of the past century, when several methods and models were already proposed for the evaluation of infiltration, still nowadays such evaluation is not frequently enough accurate for the purposes being used. This is partially due to deficiencies in the methodology being used for measuring infiltration, including some newly proposed methods and equipments, and in the use of non appropriate empirical models and approaches. In this contribution we present an analysis and discussion about the main difficulties found in the evaluation and measurement of soil water infiltration rates, and the more commonly committed errors, based on the past experiences of the author in the evaluation of soil water infiltration in many different soils and land conditions, and in their use for deducing soil water balances under variable and changing climates. It is concluded that there are not models or methods universally applicable to any soil and land condition, and that in many cases the results are significantly influenced by the way we use a particular method or instrument, and by the alterations in the soil conditions by the land management, but also due to the manipulation of the soil before and during the measurement. Direct "in situ" field evaluations have to be preferred in any case to indirect deductions from other soil characteristics measured under laboratory conditions in the same soils, or in other soils, through the so called "pedo-transfer" functions, or through the use of stochastic models such as the SCS Curve Number Method, or of other models using empirical or physical approaches, which have demonstrated to be of limited value in most of the cases. References Philip, J. R., 1954., An infiltration equation with physical significance: Soil Sci..,v. 77, p. 153-157. Philip, J. R., 1958. The theory of infiltration, pt. 7: Soil Sci., v. 85, no. 6, p. 333-337. Pla, I.1981. Simuladores de lluvia para el estudio de relaciones suelo-agua bajo agricultura de secano en los trópicos. Rev. Fac. Agron. XII(1-2):81-93.Maracay (Venezuela) Pla, I. 1986. A routine laboratory index to predict the effects of soil sealing on soil and water conservation. En "Assesment of Soil Surface Sealing and Crusting". 154-162.State Univ. of Ghent.Gante (Bélgica Pla, I., 1997. A soil water balance model for monitoring soil erosion processes and effects on steep lands in the tropics. Soil Technology. 11(1):17-30. Elsevier Pla, I., M.C. Ramos, S. Nacci, F. Fonseca y X. Abreu. 2005. Soil moisture regime in dryland vineyards of Catalunya (Spain) as influenced by climate, soil and land management. "Integrated Soil and Water Management for Orchard Development". FAO Land and Water Bulletin 10. 41-49. Roma (Italia). Pla, I., 2006. Hydrological approach for assessing desertification processes in the Mediterranean region. In W.G. Kepner et al. (Editors), Desertification in the Mediterranean Region. A Security Issue. 579-600 Springer. Heidelberg (Germany) Pla, I. 2011. Evaluación y Modelización Hidrológica para el Diagnóstico y Prevención de "Desastres Naturales". Gestión y Ambiente 14 (3): 17-22. UN-Medellín (Colombia). ISSN 0124.177X

Pla-Sentís, Ildefonso

2013-04-01

204

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

Microsoft Academic Search

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

Shuhua Yi; A. David McGuire; Jennifer Harden; Eric Kasischke; Kristen Manies; Larry Hinzman; Anna Liljedahl; Jim Randerson; Heping Liu; Vladimir Romanovsky; Sergei Marchenko; Yongwon Kim

2009-01-01

205

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

206

Critical water contents of hydrophobic soils in New Zealand  

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

207

Effect of Intercropping Coconut Lands on Soil Water Retention  

Microsoft Academic Search

This study was conducted to evaluate the effect of intercropping coconut lands on soil water retention, available water, porosity and their relationship with organic matter contents. The results showed that the water holding capacity and available water increased significantly at both depths (0–20 and 20–40 cm) investigated. The increase in available water was mainly due to increase in field capacity

Ranjith B. Mapa

1995-01-01

208

Soil Water Content Measurements with Ground-Penetrating Radar: a Review  

Microsoft Academic Search

We present a comprehensive review of methods to measure soil water content with ground penetrating radar. We distinguish four categories: soil water content determined from reflected wave velocity, soil water content determined from ground wave velocity, soil water content determined from transmitted wave velocity between boreholes and soil water content determined from the surface reflection coefficient. For each of the

J. A. Huisman; S. S. Hubbard; D. Redman; P. A. Annan

2003-01-01

209

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...

210

A Technique for Producing Soil Water Retention Curves  

Microsoft Academic Search

Water retention curves compiled for specific soil types are an essential management and research tool in evaluating plant stress. The method of producing water retention curves by means of the 1500 kPa pressure extractor is described.

L. van der Merwe

1990-01-01

211

Soil-Water Evaporation Dynamics Determined From Soil Sensible Heat Transfer Measurements  

NASA Astrophysics Data System (ADS)

Soil-water evaporation is important in both the hydrologic cycle and the surface energy balance and for processes ranging from microbial ecology to global climate change. Yet, routine measurements are unable to capture rapidly shifting near-surface soil heat and water transfer processes involved in soil-water evaporation. Recent advancements in fine-scale measurement of soil thermal properties provide a new opportunity to observe heat transfer associated with soil-water evaporation in the upper centimeters of the vadose zone. The objective of this study was to determine the depth and location of the evaporation zone within soil using observations of sensible heat transfer. Three-needle heat-pulse sensors were used to monitor soil heat capacity, thermal conductivity, water content, and temperature below a bare soil surface in Central Iowa during natural wetting/drying cycles. Soil heat flux and changes in heat storage were calculated from these data to obtain a balance of sensible heat components. The residual from this balance (i.e., the net heat flux minus the change in heat storage) was attributed to latent heat from water evaporation, and thus, provided estimates of in situ water evaporation. As the soil dried following rainfall, results showed divergence in the soil sensible heat flux with depth. Divergence in the heat flux indicated the location of a heat sink associated with soil-water evaporation. Evaporation estimates from the sensible heat balance provided depth and time patterns consistent with observed soil-water depletion patterns. Evaporation occurred near the soil surface immediately after rainfall and the evaporation zone proceeded below 3 mm in the profile within 2-3 d of rainfall events. As the soil dried, the evaporation zone continued to penetrate deeper into the soil extending below 13 mm within 6 d after rainfall. Peak evaporation rates as high as 0.42 mm/h were observed at the 3-mm depth near midday, with evaporation declining by late afternoon. Evaporation occurred simultaneously at multiple soil depth increments, but with time lag between peak evaporation rates for the deeper depths. Daily heat-balance evaporation estimates compared well with microlysimeter evaporation estimates taken 3 or more d after rainfall providing root mean square error of 0.11 mm/d and r2 = 0.90. Implementation of fine-scale measurement techniques for the soil sensible heat balance provides a new opportunity to improve understanding of soil-water evaporation.

Heitman, J. L.; Horton, R.; Sauer, T. J.; Desutter, T. M.

2007-12-01

212

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

NASA Astrophysics Data System (ADS)

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).

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

2008-12-01

213

FIRE AND GRAZING EFFECTS ON WIND EROSION, SOIL WATER CONTENT, AND SOIL TEMPERATURE  

Technology Transfer Automated Retrieval System (TEKTRAN)

Selective grazing of burned patches can be intense if animal distribution is not controlled and may compound the independent effects of fire and grazing on soil characteristics. Our objectives were to quantify the effects of patch burning and grazing on wind erosion soil water content, and soil temp...

214

Relationship between porosimetry measurement and soil–water characteristic curve for an unsaturated residual soil  

Microsoft Academic Search

Soil–water characteristic curve (SWCC) is an important tool for determining the engineering properties of unsaturated soil. This depends on the size and distribution of pore structures which control the permeability and amount of volume change. Mercury Intrusion Porosimetry tests can be used to determine the size, amount and distribution of pore spaces of the soil in a shorter time period

K. K. Aung; H. Rahardjo; E. C. Leong; D. G. Toll

2001-01-01

215

Performance of pedotransfer functions in predicting soil water characteristics of soils in Norway  

Microsoft Academic Search

Pedotransfer functions (PTFs), predicting the soil water retention curve (SWRC) from basic soil physical properties, need to be validated on arable soils in Norway. In this study we compared the performance of PTFs developed by Riley (1996), Rawls and Brakensiek (1989), Vereecken et al. (1989), Wösten et al. (1999) and Schaap et al. (2001). We compared SWRCs calculated using textural

Sigrun Hjalmarsdottir Kværnø; Lars Egil Haugen

2011-01-01

216

Soil Moisture-Ecosystem-Climate Interactions in a Changing Climate  

NASA Astrophysics Data System (ADS)

Soil moisture is a key variable of the climate system. It constrains plant transpiration and photosynthesis in several regions of the world, with consequent impacts on the water, energy and biogeochemical cycles (e.g. Seneviratne et al. 2010). Moreover it is a storage component for precipitation and radiation anomalies, inducing persistence in the climate system. Finally, it is involved in a number of feedbacks at the local, regional and global scales, and plays a major role in climate-change projections. This presentation will provide an overview on these interactions, based on several recent publications (e.g. Seneviratne et al. 2006, Orlowsky and Seneviratne 2010, Teuling et al. 2010, Hirschi et al. 2011). In particular, it will highlight possible impacts of soil moisture-ecosystem coupling for climate extremes such as heat waves and droughts, and the resulting interconnections between biophysical and biogeochemical feedbacks in the context of climate change. Finally, it will also address recent regional- to global-scale trends in land hydrology and ecosystem functioning, as well as issues and potential avenues for investigating these trends (e.g. Jung et al. 2010, Mueller et al. 2011). References Hirschi, M., S.I. Seneviratne, V. Alexandrov, F. Boberg, C. Boroneant, O.B. Christensen, H. Formayer, B. Orlowsky, and P. Stepanek, 2011: Observational evidence for soil-moisture impact on hot extremes in southeastern Europe. Nature Geoscience, 4, 17-21, doi:10.1038/ngeo1032. Jung, M., et al., 2010: Recent decline in the global land evapotranspiration trend due to limited moisture supply. Nature, 467, 951-954. doi:10.1038/nature09396 Mueller, B., S.I. Seneviratne, et al.: Evaluation of global observations-based evapotranspiration datasets and IPCC AR4 simulations, Geophys. Res. Lett., 38, L06402, doi:10.1029/2010GL046230 Orlowsky, B., and S.I. Seneviratne, 2010: Statistical analyses of land-atmosphere feedbacks and their possible pitfalls. J. Climate, 23(14), 3918-3932 Seneviratne, S.I., T. Corti, E.L. Davin, M. Hirschi, E.B. Jaeger, I. Lehner, B. Orlowsky, and A.J. Teuling, 2010: Investigating soil moisture-climate interactions in a changing climate: A review. Earth-Science Reviews, 99, 3-4, 125-161, doi:10.1016/j.earscirev.2010.02.004 Seneviratne, S.I., D. Lüthi, M. Litschi, and C. Schär, 2006: Land-atmosphere coupling and climate change in Europe. Nature, 443, 205-209. Teuling, A.J., S.I. Seneviratne, et al. 2010: Contrasting response of European forest and grassland energy exchange to heatwaves. Nature Geoscience, 3, 722-727, doi:10.1038/ngeo950.

Seneviratne, S. I.; Davin, E.; Hirschi, M.; Mueller, B.; Orlowsky, B.; Teuling, A.

2011-12-01

217

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

NASA Astrophysics Data System (ADS)

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

Vanclooster, Marnik

2010-05-01

218

Scaling soil water retention functions using particle-size distribution  

NASA Astrophysics Data System (ADS)

The application of spatially distributed hydrological model is a challenging problem, particularly because of the difficulties arising in the identification of the model parameters describing the soil hydraulic properties and their spatial variability. Generally soil data are available just for a limited number of locations across the study area and very often the available data consist of soil physical and chemical properties rather than direct measurements of the soil hydraulic properties. Thus indirect methods are often required for an assessment of model parameters describing the soil hydraulic properties, based on a limited number of measurements. This study presents a methodology for assessing the variability of soil water retention from soil texture and bulk density measurements, based on a combination of the scaling approach proposed by Kosugi and Hopmans (1998) and the Arya-Paris (AP) physico-empirical pedotransfer function. The approach proposed by Kosugi and Hopmans (1998) represents the spatial variability of soil hydraulic properties by scaling factors which relate the soil hydraulic functions in any location to a single reference function, provided that soils are characterised by geometric similitude within the study area. The Arya-Paris (AP) physico-empirical pedotransfer function estimates the soil water retention from the soil particle-size distribution and bulk density. The proposed method has been evaluated in two different areas of Southern Italy. Laboratory-measured and AP-predicted reference water retention functions are compared by evaluating the lognormal distributions of the corresponding scaling factors. The method proved to be effective even with a limited number of soil samples (30-40 soil samples), provided that the study region is classified according to homogeneous soil textural classes, to ensure the geometric similitude within each soil sample set. This method can be potentially used as an effective tool for identifying homogeneous soil hydrologic response units at the catchment scale.

Nasta, P.; Chirico, G. B.; Kamai, T.; Hopmans, J. W.; Romano, N.

2009-04-01

219

Scaling soil water retention functions using particle-size distribution  

NASA Astrophysics Data System (ADS)

The application of spatially distributed hydrological model is a challenging problem, particularly because of the difficulties arising in the identification of the model parameters describing the soil hydraulic properties and their spatial variability. Generally soil data are available just for a limited number of locations across the study area and very often the available data consist of soil physical and chemical properties rather than direct measurements of the soil hydraulic properties. Thus indirect methods are often required for an assessment of model parameters describing the soil hydraulic properties, based on a limited number of measurements. This study presents a methodology for assessing the variability of soil water retention from soil texture and bulk density measurements, based on a combination of the scaling approach and the Arya-Paris (AP) physico-empirical pedotransfer function. The approach represents the spatial variability of soil hydraulic properties by scaling factors which relate the soil hydraulic functions in any location to a single reference function, provided that soils are characterised by geometric similitude within the study area. The Arya-Paris (AP) physico-empirical pedotransfer function estimates the soil water retention from the soil particle-size distribution and bulk density. The proposed method has been evaluated in two different areas of Southern Italy. Laboratory-measured and AP-predicted reference water retention functions are compared by evaluating the lognormal distributions of the corresponding scaling factors. The method proved to be effective even with a limited number of soil samples (30-40 soil samples), provided that the study region is classified according to homogeneous soil textural classes, to ensure the geometric similitude within each soil sample set. This method can be potentially used as an effective tool for identifying homogeneous soil hydrologic response units at the catchment scale.

Nasta, P.; Hopmans, J. W.; Kamai, T.; Romano, N.; Chirico, G.

2009-12-01

220

The Forest as a Soil and Water Manager  

NASA Astrophysics Data System (ADS)

Forests provide a vital service in regulating stream flow and protecting soil from erosion. Loss of forest cover increases erosion (by raindrop impact, surface runoff, gullies, landslides and river bank failure) and the transfer of eroded soil or sediment to the river network. It also increases annual runoff and the peak discharges of at least small to moderate flood events, and thus the sediment transporting capability of streams. Adverse impacts include reservoir sedimentation, aquatic habitat degradation and river channel instability. Sediment also greatly increases the destructive effects of floods. The forest/erosion interface takes many forms, e.g. forest fire impact, forest/landslide interaction and impact of pre-plantation activities such as ditching. However, despite decades of study, data on forests and erosion remain relatively fragmented and there is no integrated overview at regional to continental scales, e.g. at the European scale. Further, quantitative understanding does not yet match qualitative understanding and lags behind our ability to make quantitative generalizations on, for example, the impact of forest cover on water yields and flood frequencies. This presentation therefore discusses our current understanding of the effect of forest cover on water runoff and soil erosion, highlighting in particular the type of quantitative data available and the quantitative methods which are available to predict the impact of changes in forest cover, including their limitations. It also considers the type of models needed to predict the impacts of land use and climate change on soil erosion and proposes a next step in improving our predictive capability for the forest/erosion interface through an integration of existing research to provide generalizations and an overview at regional to subcontinental scales.

Bathurst, J. C.

2012-04-01

221

Studies on physico-chemical relations of soil and water  

Microsoft Academic Search

Summary and Conclusions  The paper deals with effects of ammonium sulphate (N), potassium sulphate (K) and double superphosphate (P), singly and in\\u000a combinations (total 8 treatments) on the water retentive force of the soil at different moisture contents.\\u000a \\u000a As the moisture content of the soil decreases the water retentive force of the soil increases. The changes in this force are\\u000a less

B. N. Singh; M. L. Mehta

1939-01-01

222

Numerical analysis of soil pipe effects on hillslope water dynamics  

Microsoft Academic Search

Soil pipes are considered to drain off water from a hillslope and play an important role in the subsurface runoff generation\\u000a process, thus reducing the slope failure susceptibility. However, soil pipes are also often detected on the collapsed slope\\u000a suggesting that they might act to induce slope instability. To examine how the soil pipes act on pore-water pressure generation\\u000a and

Raj H. Sharma; Heinz Konietzky; Ken’ichirou Kosugi

2010-01-01

223

Management of Irrigation with Saline Water in Cracking Clay Soils  

Microsoft Academic Search

Management scenarios aimed at optimizing irrigation in a Sicilian vineyard characterized by a cracking clay soil irrigated with saline wa- ter were explored for seven soil profiles (Baglio 1-Baglio 7), by using the simulation model soil-water-atmosphere-plant environment (SWAP), which accounts for shrinkage and cracking. Accurate pre- diction of water content, u, was obtained for the seven profiles by expressing the

Giuseppina Crescimanno; Paolo Garofalo

2006-01-01

224

Water and heat fluxes in desert soils 1. Field studies  

Microsoft Academic Search

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

Bridget R. Scanlon

1994-01-01

225

Clay Deposits for Water Management of Sandy Soils  

Microsoft Academic Search

Water management practices in conserving water for arid lands are crucial in sustaining agriculture and food production. Sandy soils (Typic Torrripsamments) are practically important land resources in many Middle Eastern countries. In a laboratory experiment, five naturally occurring clay deposits were applied at different rates to sandy calcareous soil in order to evaluate their effect on relative swelling, infiltration and

A. M. AL-OMRAN; A. M. FALATAH; A. S. SHETA; A. R. AL-HARBI

2004-01-01

226

Soil water regime and runoff formation in a small catchment  

Microsoft Academic Search

The precipitation - runoff transformation is realised in two steps in a small catchment. In the first step, the soil behaves as a reservoir, filled with rainwater, and emptied by the water uptake for plant transpiration. In the course of the vegetation season, the soil water content oscillates between two typical values - maximum and minimum. The maximum value corresponds

J. Prazak; L. Lichner

2003-01-01

227

EVAPORATION FROM SHALLOW WATER TABLE THROUGH LAYERED SOIL PROFILES  

Microsoft Academic Search

The purpose of this study is to estimate the steady state evaporation rates from layered soils in the presence of high water table under isothermal conditions. A finite difference numerical scheme based upon the one-dimensional Richards equation has been employed to estimate the evaporation rates from a two-layered soil profile overlying a shallow water for appropriate initial and boundary conditions.

C. P. Kumar

1999-01-01

228

Measuring surface water in soil with light reflectance  

Microsoft Academic Search

The light absorbed by water in soil and plants is readily determined using hyperspectral full-range imagery and field spectrometers. The full absorption of light can be accounted for by fitting the shape of water absorptions at the same time as other diagnostic bands using multiple Gaussian functions. This research is particularly important in soils due to the loss of mineral

Michael L. Whiting

2009-01-01

229

Effect of single Quercus ilex trees upon spatial and seasonal changes in soil water content in dehesas of central western Spain  

Microsoft Academic Search

The spatial and temporal evolution of soil water content (?) in Quercus ilex dehesas has been investigated to determine how trees modify the soil water dynamics and the nature of tree-grass interactions\\u000a in terms of soil water use in these ecosystems. Soil physical parameters and ? were measured at different distances from the\\u000a tree trunk (2–30 m) in the upper

Elena Cubera; Gerardo Moreno

2007-01-01

230

Soil as a Medium for the Renovation of Acid Mine Drainage Water: Part II. Soil Physical and Chemical Changes.  

National Technical Information Service (NTIS)

Acid coal mine water was applied to a Linden sandy loam soil at various levels. The soil data indicated that the main reactions between the applied water and the soil occurred in the upper part of the soil profile. The cation exchange capacity of the soil...

E. J. Ciolkosz L. T. Kardos R. C. Cronce E. R. Stein

1978-01-01

231

Sewage sludge-soil interactions as measured by plant and soil chemical composition. [Lactuca sativa L  

Microsoft Academic Search

The utilization of sewage sludge on agricultural lands requires prior knowledge of the interactions among sludge, soil, and plant. A greenhouse experiment was conducted on three mineralogically different soils: a limed, volcanic ash-derived Andept (Akaka series, thixotropic, isomesic Typic Hydrandepts), and alkaline Vertisol (Lualualei series, very-fine, montmorillonitic, isohyperthermic Typic Chromusterts) and a limed, manganiferous Oxisol (Wahiawa series, clayey, kaolinitic, isohyperthermic

N. V. Hue; J. A. Silva; R. Arifin

2009-01-01

232

Temperature and soil moisture interactively affected soil net N mineralization in temperate grassland in Northern China  

Microsoft Academic Search

Intact soil cores from three adjacent sites (Site A: grazed, Site B: fenced for 4 years, and Site C: fenced for 24 years) were incubated in the laboratory to examine effects of temperature, soil moisture, and their interactions on net nitrification and N mineralization rates in the Inner Mongolia grassland of Northern China. Incubation temperature significantly influenced net nitrification and

Changhui Wang; Shiqiang Wan; Xuerong Xing; Lei Zhang; Xingguo Han

2006-01-01

233

SOIL AND COLLOIDAL PHOSPHORUS DYNAMICS IN THREE KY SOILS: BIOAVAILABILITY, TRANSPORT AND WATER QUALITY IMPLICATIONS  

Microsoft Academic Search

Particulate P constitutes a significant portion of the total P found in surface runoff water. Water dispersed P-containing particles can travel long distances via surface runoff and reach water bodies causing decrease in water quality. The main objective of the study was to evaluate the potential facilitation of P transport by the water dispersed soil colloids (WDC) using three KY

Konstantinos Christos Makris

2003-01-01

234

Scatterometer-Derived Soil Moisture Calibrated for Soil Texture With a One-Dimensional WaterFlow Model  

Microsoft Academic Search

Current global satellite scatterometer-based soil moisture retrieval algorithms do not take soil characteristics into account. In this paper, the characteristic time length of the soil water index has been calibrated for ten sampling frequencies and for different soil conductivity associated with 12 soil texture classes. The calibration experiment was independently performed from satellite observations. The reference soil moisture data set

Remko de Lange; Rob Beck; Nick van de Giesen; Jan Friesen; Allard de Wit; Wolfgang Wagner

2008-01-01

235

Compatibility of Ninth Avenue Superfund Site Ground Water with Two Soil-Bentonite Slurry Wall Backfill Mixtures.  

National Technical Information Service (NTIS)

The interactions between solutes found in leachates from uncontrolled landfills and components of a soil-bentonite (SB) slurry wall are capable of causing swelling or shrinking slurry wall. The effect of solutes in contaminated ground water from the Ninth...

M. E. Zappi R. A. Shafer D. D. Adrian

1990-01-01

236

Effects of different soil and water conservation tillage on runoff, sediment and soil carbon  

Microsoft Academic Search

To study effects of different tillage on soil and water conservation (SWC) and soil carbon reduction on red-soil sloping land in south China, field experiments including three tillage measures(strip intercropping, contour intercropping and clean tillage) and a check were performed on the representative area named Jiangxi Eco-science Park of SWC. The surface runoff and soil loss of each treatment were

Haijin Zheng; Hongjiang Zhang; Shaowen Fang; Jie Yang; Songhua Xie; Xiaoan Chen

2011-01-01

237

Reaction of soil water repellency to artificially induced changes in soil pH  

Microsoft Academic Search

Soil water repellency (SWR) is widely thought to be influenced by soil pH, however, few studies have systematically investigated the relationship between these variables. Specifically the hypothesis that the pH may control repellency via changes in the variable surface charge of soil material has not yet been tested. In previous work, methods for changing soil pH have also involved changes

D. Diehl; J. V. Bayer; S. K. Woche; R. Bryant; S. H. Doerr; G. E. Schaumann

2010-01-01

238

Soil Water Distribution and Movement in Layered Soils of a Dam Farmland  

Microsoft Academic Search

In soil profiles, special emphasis has been placed on the migration of agricultural chemicals spread intentionally or accidentally\\u000a into deep soils or groundwater body. To prevent soil water pollution and estimate the magnitude of the hazard caused by these\\u000a chemicals, it is necessary to know the processes controlling their movement from the soil surface, through the root zone and\\u000a eventually

Peipei Zhao; Ming-an Shao; Ahmed A. Melegy

2010-01-01

239

Effect of an anionic soil conditioner on water stable aggregation of three Hawaiian soils  

Microsoft Academic Search

The primary purpose of soil conditioner application is to enhance a soil's resistance to erosion processes by increasing the water stability of aggregates. In this study, a wrist?action shaker was used to assess the aggregate stability of three Hawaiian soils treated with an anionic surfactant soil conditioner (AGRI?SC). Aggregates of 2.00 to 4.00 mm in size were treated with Agri?SC

A. D. Ziegler; R. A. Sutherland

1998-01-01

240

Dynamic factor analysis of surface water management impacts on soil and bedrock water contents in Southern Florida Lowlands  

NASA Astrophysics Data System (ADS)

Canal stage fluctuations significantly affect temporal change in soil water content. Net recharge significantly affects soil water content near ground surface. Effect of water table evaporation on soil water content variation is nonsignificant. Proposed raises in C111 stage are predicted to result in negligible changes in soil water at low elevation sites.

Kisekka, I.; Migliaccio, K. W.; Muñoz-Carpena, R.; Schaffer, B.; Li, Y. C.

2013-04-01

241

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

Microsoft Academic Search

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

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

2009-01-01

242

Modeling root water uptake with root mediated soil water content redistribution  

NASA Astrophysics Data System (ADS)

The main objective of this study was to develop and test a simple root water uptake parameterization applicable in numerical models of soil water movement. The suggested approach was implemented in a one-dimensional dual-continuum model of soil water flow based on Richards' equation. The model was used to simulate soil water movement at an experimental forest site. The performance of the model was evaluated using observed soil water pressure and soil water content data. Several episodes, during which the root mediated soil water content redistribution effects played an important role, were detected. Differences between the model responses and observations, as well as differences between the traditional and newly developed root water uptake modeling approaches, were analyzed. The research was supported by the Czech Science Foundation project No. 205/08/1174.

Dohnal, M.; Votrubova, J.; Vogel, T.; Tesar, M.

2012-04-01

243

Element interactions limit soil carbon storage.  

PubMed

Rising levels of atmospheric CO2 are thought to increase C sinks in terrestrial ecosystems. The potential of these sinks to mitigate CO2 emissions, however, may be constrained by nutrients. By using metaanalysis, we found that elevated CO2 only causes accumulation of soil C when N is added at rates well above typical atmospheric N inputs. Similarly, elevated CO2 only enhances N2 fixation, the major natural process providing soil N input, when other nutrients (e.g., phosphorus, molybdenum, and potassium) are added. Hence, soil C sequestration under elevated CO2 is constrained both directly by N availability and indirectly by nutrients needed to support N2 fixation. PMID:16614072

van Groenigen, Kees-Jan; Six, Johan; Hungate, Bruce A; de Graaff, Marie-Anne; van Breemen, Nico; van Kessel, Chris

2006-04-13

244

Large-scale properties of simulated soil water variability  

NASA Astrophysics Data System (ADS)

Surface water balance computations were applied to historical data from the central and southeastern United States. The focus of the study was to characterize soil water variability across spatial scales in these two different parts of the United States. The regions studied in each area span the range of spatial scales from 106 km2 to 103 km2. Routinely collected precipitation, temperature, pan evaporation, and discharge data were utilized together with widely used parameterizations to reconstruct soil water (depth-integrated and areal-averaged soil moisture) for the period from January 1960 through December 1988. The results suggest that in the central United States, larger regions possess a greater range of temporal soil water variability than smaller embedded regions and that extreme soil water anomalies possess scales of spatial coherence that range from 105 km2 to 103 km2, with stronger anomalies characterized by smaller scales. In the Mississippi-Missouri region, variability of aggregate soil water cannot be fully characterized by soil water variability in a few "representative" catchments. Remarkable similarity of the spatiotemporal variability of soil water across scales (106 km2 to 103 km2) was found for the southeastern United States. In this area the variability across scales was characterized by a frequency scaling ratio which decreased linearly with soil water anomaly strength and which remained substantially higher than that corresponding to random occurrence, even for extreme soil water anomalies. In both regions of the United States and for all spatial scales, extreme positive anomalies show smaller spatial coherence than negative anomalies of the same magnitude.

Guetter, Alexandre K.; Georgakakos, Konstantine P.

1996-03-01

245

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

NASA Astrophysics Data System (ADS)

Understanding root-soil interactions is of high importance for environmental and agricultural management. Root uptake is an essential component in water and solute transport modeling. The amount of groundwater recharge and solute leaching significantly depends on the demand based plant extraction via its root system. Plant uptake however not only responds to the potential demand, but in most situations is limited by supply form the soil. The ability of the plant to access water and solutes in the soil is governed mainly by root distribution. Particularly under conditions of heterogeneous distribution of water and solutes in the soil, it is essential to capture the interaction between soil and roots. Root architecture models allow studying plant uptake from soil by describing growth and branching of root axes in the soil. Currently root architecture models are able to respond dynamically to water and nutrient distribution in the soil by directed growth (tropism), modified branching and enhanced exudation. The porous soil medium as rooting environment in these models is generally described by classical macroscopic water retention and sorption models, average over the pore scale. In our opinion this simplified description of the root growth medium implies several shortcomings for better understanding root-soil interactions: (i) It is well known that roots grow preferentially in preexisting pores, particularly in more rigid/dry soil. Thus the pore network contributes to the architectural form of the root system; (ii) roots themselves can influence the pore network by creating preferential flow paths (biopores) which are an essential element of structural porosity with strong impact on transport processes; (iii) plant uptake depend on both the spatial location of water/solutes in the pore network as well as the spatial distribution of roots. We therefore consider that for advancing our understanding in root-soil interactions, we need not only to extend our root models, but also improve the description of the rooting environment. Until now there have been no attempts to couple root architecture and pore network models. In our work we present a first attempt to join both types of models using the root architecture model of Leitner et al., (2010) and a pore network model presented by Raoof et al. (2010). The two main objectives of coupling both models are: (i) Representing the effect of root induced biopores on flow and transport processes: For this purpose a fixed root architecture created by the root model is superimposed as a secondary root induced pore network to the primary soil network, thus influencing the final pore topology in the network generation. (ii) Representing the influence of pre-existing pores on root branching: Using a given network of (rigid) pores, the root architecture model allocates its root axes into these preexisting pores as preferential growth paths with thereby shape the final root architecture. The main objective of our study is to reveal the potential of using a pore scale description of the plant growth medium for an improved representation of interaction processes at the interface of root and soil. References Raoof, A., Hassanizadeh, S.M. 2010. A New Method for Generating Pore-Network Models. Transp. Porous Med. 81, 391-407. Leitner, D, Klepsch, S., Bodner, G., Schnepf, S. 2010. A dynamic root system growth model based on L-Systems. Tropisms and coupling to nutrient uptake from soil. Plant Soil 332, 177-192.

Leitner, Daniel; Bodner, Gernot; Raoof, Amir

2013-04-01

246

Response of soil nitrogen retention to the interactive effects of soil texture, hydrology, and organic matter  

NASA Astrophysics Data System (ADS)

Advances in nitrogen (N) saturation and retention theories have focused on soil organic matter (SOM) biogeochemistry in the absence of dynamic soil hydrology. Here we exploit two soil types with contrasting textures that span a hillslope gradient to test hypotheses that suggest N saturation symptoms are regulated by the interactive effects of soil texture, OM, and hydrology on N retention capacity (maximum pool size) and N retention kinetics (N retention rate). Down the hillslope gradient, soil solution nitrate (NO3) concentrations sampled with lysimeters increased, while 15NO3-N retention decreased. Landscape location (upland, hillslope, and toeslope) and soil type interacted to affect soil solution NO3 concentrations so that the downslope increase in NO3 was greater in sandy versus silty soils. These patterns manifest despite a downslope increase in soil organic carbon (SOC) and C/N ratios. A positive correlation between saturated hydraulic conductivity and soil solution NO3 sampled in zero-tension lysimeters during precipitation events suggested that high hydraulic conductivity promotes periodic rapid NO3 transport at rates that exceed retention kinetics. The downslope increase in soil solution NO3 in spite of a concomitant increase in SOC and C/N ratios provides an important contrast with previous N saturation research that highlights negative correlations between SOM C/N ratios and NO3 concentrations and suggests NO3 transport along connected hillslope flow paths may overwhelm stoichiometric sinks for inorganic N retention in SOM. Our results reveal important gaps in N retention theory based on SOM biogeochemistry alone and demonstrate how coupled biogeochemical and hydrological models can improve predictions of N saturation, particularly when considering periodic advective NO3 transport in the vadose zone. We show that in coarse-textured soils, low capacity for protection of SOM N by association with fine mineral particles interacts with rapid hydrological flushing of NO3 to enhance the expression of ecosystem N saturation symptoms.

Castellano, Michael J.; Lewis, David Bruce; Kaye, Jason P.

2013-03-01

247

Laboratory Experiments to Study Radiocaesium Interaction in Organic Soils  

Microsoft Academic Search

The total concentration of a pollutant in a given environmental compartment is often used for risk assessment. However, the real impact of the pollutant also depends on its toxicity and mobility. In soils, pollutant mobility is strongly related to its interaction with the different sites. The mechanisms and dynamics of this interaction may be studied by adsorption and desorption approaches.

A. Rigol; M. Vidal; G. Rauret

2000-01-01

248

Effect of soil water content on soil thermal conductivity under field conditions  

NASA Astrophysics Data System (ADS)

Knowledge of the thermal properties of soils is required in many areas of engineering, meteorology, agronomy, and ecosystem and soil science. Soil thermal conductivity varies in time and space, since it is influenced by soil properties as well as soil temperature and moisture conditions. We use the one dimensional heat conduction equation in conjunction with two-year data measured in a grass-covered field in North Carolina Piedmont to estimate soil thermal conductivity and to investigate how it is impacted by water content. In agreement with laboratory experiments reported in the literature, our results suggest that under dry conditions soil thermal conductivity increases across a relatively narrow range of soil water contents, above which a further increase in water content does not significantly change thermal conductivity. However, when soil approaches saturation, heat transfer is further improved, a fact not previously noted. This nonlinear behavior is consistent with the formation at high water contents of a continuous film of liquid water in soil aggregates of mineral and organic matter.

Vico, G.; Daly, E.; Manzoni, S.; Porporato, A.

2008-12-01

249

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

Microsoft Academic Search

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

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

2010-01-01

250

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

251

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...

252

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

Code of Federal Regulations, 2010 CFR

...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...

2009-04-01

253

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

Code of Federal Regulations, 2010 CFR

...2009-04-01 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...

2009-04-01

254

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

Code of Federal Regulations, 2010 CFR

...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...

2010-04-01

255

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

Code of Federal Regulations, 2010 CFR

...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...

2010-04-01

256

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...continued) § 1.175-2 Definition of soil and water conservation expenditures...expenditures paid or incurred for the purpose of soil or water conservation in...

2013-04-01

257

Interaction between reinforcing geosynthetics and soil-tire chip mixtures  

SciTech Connect

The objective of the present study was to evaluate the mechanical properties of tire chips and soil-tire chip mixtures relevant to geosynthetic-reinforced earthworks. Tests were conducted to evaluate shear strength and pull-out capacity with a woven geotextile and two geogrids. Soil-tire chip mixtures made with clean sand and sandy silt were tested. These properties were then used to assess the potential advantages of using soil-tire chip backfills for geosynthetic-reinforced retaining walls and embankments. The test results show that the geosynthetic pull-out force in tire chip and soil-tire chip backfills increases with displacement--i.e., no peak pull-out force is generally obtained, at least for displacements {le}100 mm. Pull-out interaction coefficients for the chip backfills are typically greater than 1, whereas for soil-tire chip backfills are typically greater than 1, whereas for soil-tire chip backfills they typically range between 0.2 and 0.7, even though the pull-out capacity for soil-tire chip backfills is generally similar to or greater than the pull-out capacity in a soil backfill. The higher strength, lower unit weight and good backfill-geosynthetic interaction obtained with soil-tire chip backfills can result in walls requiring less geosynthetic reinforcement than walls backfilled with soil. In addition, embankments can potentially be constructed with steeper slopes and a smaller volume of material when soil-tire chip fill is used, while providing greater resistance against lateral sliding and foundation settlement.

Tatlisoz, N. [International United Consultants, Inc., Istanbul (Turkey); Edil, T.B.; Benson, C.H. [Univ. of Wisconsin, Madison, WI (United States). Civil and Environmental Engineering

1998-11-01

258

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

259

INTERACTION OF VEGETATION AND SOIL FROST PHENOMENA?  

Microsoft Academic Search

N northern lands special problems presented by frost in soils are receiving more and more attention as the pace of construction and settlement increases. Investigations aimed primarily at these problems, notably that of permafrost, have partially revealed the composition and mechanisms of the severe frost climate1 environment. Parts of this environment owe their nature to the influence of vegetation and

William S. Benninghoff

260

Scaling Infiltration and Other Soil Water Processes Across Diverse Soil textural Classes  

NASA Astrophysics Data System (ADS)

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 dependant) were also strongly related to lambda. We then examined how these relationships to lambda led to relationships for infiltration across soil textural classes using three different approaches, as well as the subsequent soil water contents during redistribution, evaporation, and transpiration. The Root Zone Water Quality Model was used to generate data for infiltration under four rainfall intensities, redistribution for four initial wetting depths, and evaporation and transpiration under different potential rates in eleven textural class mean soils. Cumulative infiltration could be scaled quite well across textural classes based on knowledge of lamda using the Green-Ampt normalization equations. There were also strong empirical functional relationships between cumulative infiltration at fixed times across soils and the soils' lamda, and between the parameters of the empirical Kostiakov (Lewis) infiltration equation and lamda as well as Ksat. The Kostiakov parameters vs. lamda or Ksat (Ksat was better) provided more compact and explicit relationships across diverse soil classes both for instantaneous ponding and non-instantaneous ponding (e.g., rainfall) infiltration conditions, and could be used to scale and estimate infiltration across these classes. Similar strong relations were found between lamda (and by inference Ksat) and soil water contents across soil types during redistribution, and for evapotranspiration and transpiration. This study is a breakthrough in our understanding of the soil water relationships and scaling among soil textural classes, that could serve as a basis for describing spatial variability of soil water on the landscape for site-specific management and for scaling up results in modeling from plots to fields to watersheds.

Kozak, J.; Ahuja, L.; Green, T.

2005-12-01

261

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

PubMed Central

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.

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

2011-01-01

262

Tank-farm construction: Tank-soil interaction in tank-farm construction  

Microsoft Academic Search

This article illustrates examples of tank-soil interaction as a result of utilization of the above concepts. The need to address tank-soil interaction arises due to concern for two phenomena, namely, stability and settlement. If adequate soil bearing is not available, soil will move out from under the tank causing the tank to fail. Settlement of soil can create stresses leading

Ahmed

1984-01-01

263

Evaluation of different field methods for measuring soil water infiltration  

NASA Astrophysics Data System (ADS)

Soil infiltrability, together with rainfall characteristics, is the most important hydrological parameter for the evaluation and diagnosis of the soil water balance and soil moisture regime. Those balances and regimes are the main regulating factors of the on site water supply to plants and other soil organisms and of other important processes like runoff, surface and mass erosion, drainage, etc, affecting sedimentation, flooding, soil and water pollution, water supply for different purposes (population, agriculture, industries, hydroelectricity), etc. Therefore the direct measurement of water infiltration rates or its indirect deduction from other soil characteristics or properties has become indispensable for the evaluation and modelling of the previously mentioned processes. Indirect deductions from other soil characteristics measured under laboratory conditions in the same soils, or in other soils, through the so called "pedo-transfer" functions, have demonstrated to be of limited value in most of the cases. Direct "in situ" field evaluations have to be preferred in any case. In this contribution we present the results of past experiences in the measurement of soil water infiltration rates in many different soils and land conditions, and their use for deducing soil water balances under variable climates. There are also presented and discussed recent results obtained in comparing different methods, using double and single ring infiltrometers, rainfall simulators, and disc permeameters, of different sizes, in soils with very contrasting surface and profile characteristics and conditions, including stony soils and very sloping lands. It is concluded that there are not methods universally applicable to any soil and land condition, and that in many cases the results are significantly influenced by the way we use a particular method or instrument, and by the alterations in the soil conditions by the land management, but also due to the manipulation of the surface soil before and during the measurement. Due to the commonly found high variability, natural or induced by land management, of the soil surface and subsurface hydrological properties, and to the limitations imposed by the requirements of water for the measurements, there is proposed a simple and handy method, which do not use high volumes of water, adaptable to very different soil and land conditions, and that allow many repeated measurements with acceptable accuracy for most of the purposes. References Pla, I., 1997. A soil water balance model for monitoring soil erosion processes and effects on steep lands in the tropics. Soil Technology. 11(1):17-30. Elsevier Pla, I., 2006. Hydrological approach for assessing desertification processes in the Mediterranean region. In W.G. Kepner et al. (Editors), Desertification in the Mediterranean Region. A Security Issue. 579-600 Springer. Heidelberg (Germany) Reynolds W.D., B.T. Bowman, R.R. Brunke, C.F. Drury and C.S. Tan. 2000. Comparison of Tension Infiltrometer, Pressure Infiltrometer, and Soil Core Estimates of Saturated Hydraulic Conductivity . Soil Science Society of America Journal 64:478-484 Segal, E., S.A.Bradford, P. Shouse; N. Lazarovich, and D. Corwin. 2008. Integration of Hard and Soft Data to Characterize Field-Scale Hydraulic Properties for Flow and Transport Studies. Vadose Zone J 7:878-889 Young, E. 1991. Infiltration measurements, a review. Hydrological processes 5: 309-320.

Pla-Sentís, Ildefonso; Fonseca, Francisco

2010-05-01

264

Errors in water retention curves determined with pressure plates: Effects on the soil water balance  

NASA Astrophysics Data System (ADS)

Pressure plates apparatus are very common experimental devices utilized to measure the soil water retention curve. Many studies have demonstrated the lack of reliability of pressure plates apparatus when they are used to measure the soil water retention curve in the dry range, due to low plate and soil conductance, lack of hydrostatic equilibrium, lack of soil-plate contact and soil dispersion. In this research, we investigated measurements of soil water retention curves obtained with a combination of Stackman's tables, pressure plates apparatus and the chilled-mirror dew point technique. Specifically, the aim of this research was: (a) to investigate the differences in the measured soil water retention curves by the different experimental methods, (b) evaluate relationships between the experimental differences and soil texture, (c) analyze the effect of experimental differences on hydraulic properties parameterization and (d) investigate the effects of the different parameters set on water transport computation. The results showed differences in measurements made by the combination of Stackman's tables and Richards' pressure plates apparatus as compared to the dew point method, for fine textured soils, while no significant differences were detected for coarse textured soils. Computed cumulative drainage and evaporation displayed lower values if soil water retention curves were obtained from data obtained with the Stackman's tables and Richards' pressure plates apparatus instead of the dew point method. In soils, where the soil water retention curve was measured with traditional methods (Stackman's tables and Richards' pressure plates apparatus) average cumulative drainage was 173 mm, with respect to a combination of methods including the dew point methods, where the average cumulative drainage was 184 mm. Average cumulative evaporation was 77 mm for the traditional methods, while it was 91 mm, for the combination of methods. Overall, when simulation models are used for studies related to solute transport, polluted soil remediation, irrigation management and others, erroneous measurement of the SWRC for fine textured soils, may lead to erroneous computation of the soil water balance.

Solone, R.; Bittelli, M.; Tomei, F.; Morari, F.

2012-11-01

265

Water Dynamics and Interactions in Water-Polyether Binary Mixtures  

PubMed Central

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

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

2009-01-01

266

The role of waste thermal water in the soil degradation  

NASA Astrophysics Data System (ADS)

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.

Balog, Kitti; Farsang, Andrea

2010-05-01

267

The mean depth of soil water uptake by two temperate grassland species over time subjected to mild soil water deficit and competitive association  

Microsoft Academic Search

Little is known concerning the soil water use dynamics of white clover (WC) and ryegrass (RG) grown in mixtures. A greenhouse study, on a deep soil, was conducted to determine the mean depth of soil water uptake of WC and RG plants grown in a competitive association and subjected to a moderate soil water deficit. Plant growth period simulated that

P. Grieu; D. W. Lucero; R. Ardiani; J. R. Ehleringer

2001-01-01

268

Residues of some chlorinated hydrocarbon pesticides in rain water, soil and ground water, and their influence on some soil microorganisms  

Microsoft Academic Search

Residues of lindane, heptachlor, heptachlor epoxide, aldrin, endrin, dieldrin, and DDT were monitored in rain water, the soil profile, and ground water. Heptachlor and heptachlor epoxide were detected in rain water in 1995 and 1996. The total concentrations of organochlorine detected were 4.7 and 10.6 ?g L?1 for 1995 and 1996, respectively. Top soil showed a wider spectrum and higher

Mohamed Tawfic Ahmed; Saad M. M. Ismail; S. S. Mabrouk

1998-01-01

269

Water films and scaling of soil characteristic curves at low water contents  

Microsoft Academic Search

Individual contributions of capillarity and adsorptive surface forces to the matric potential are seldom differentiated in determination of soil water characteristic (SWC) curves. Typically, capillary forces dominate at the wet end, whereas adsorptive surface forces dominate at the dry end of a SWC where water is held as thin liquid films. The amount of adsorbed soil water is intimately linked

Markus Tuller

2005-01-01

270

Soil Water Characteristic Determination from Concurrent Water Content Measurements in Reference Porous Media  

Microsoft Academic Search

tant in many water flow processes. Common approaches to measuring (h) in intact field soils require paired We introduce and verify the use of calibrated reference soils or and h sensors; however, most paired-sensor methods other porous media having known and reproducible water retention characteristics as a means to determine the unknown water retention suffer from incompatibility in measurement range

Jon M. Wraith; Dani

2001-01-01

271

Soil Water Characteristic Estimates by Texture and Organic Matter for Hydrologic Solutions  

Microsoft Academic Search

Hydrologic analyses often involve the evaluation of soil water in- filtration, conductivity, storage, and plant-water relationships. To de- fine the hydrologic soil water effects requires estimating soil water characteristics for water potential and hydraulic conductivity using soil variables such as texture, organic matter (OM), and structure. Field or laboratory measurements are difficult, costly, and often impractical for many hydrologic analyses.

K. E. Saxton; W. J. Rawls

2006-01-01

272

SOIL WATER CHARACTERISTIC ESTIMATES BY TEXTURE AND ORGANIC MATTER FOR HYDROLOGIC SOLUTIONS  

Technology Transfer Automated Retrieval System (TEKTRAN)

Hydrologic analyses frequently involve the evaluation of soil water infiltration, conductivity and storage, and plant-water relationships. To define variable soil water effects requires estimating relationships of soil-water potential and hydraulic conductivity with soil water content. These rela...

273

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

NASA Astrophysics Data System (ADS)

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

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

2007-12-01

274

Soil water content and freezing temperature affect freeze–thaw related N 2 O production in organic soil  

Microsoft Academic Search

An organic agricultural soil was exposed to freeze–thaw cycles (FTC) using either intact soil cores or cores packed with homogenized soil. The cores were first exposed to two mild FTCs (–1.5?°C\\/+4?°C) with soil water content being 56–85% of the water-filled pore space (WFPS). Both intact and packed soil cores showed high N2O emissions when the soil was thawing and had

Hannu T. Koponen; Pertti J. Martikainen

2004-01-01

275

Estimating the water retention curve from soil properties: comparison of linear, nonlinear and concomitant variable methods  

Microsoft Academic Search

The unsaturated soil hydraulic functions involving the soil–water retention curve (SWRC) and the hydraulic conductivity provide useful integrated indices of soil quality. Existing and newly devised methods were used to formulate pedotransfer functions (PTFs) that predict the SWRC from readily available soil data. The PTFs were calibrated using a large soils database from Hungary. The database contains measured soil–water retention

Kálmán Rajkai; Sándor Kabos; M. Th. van Genuchten

2004-01-01

276

WATER REPELLENT SOILS AND THEIR RELATION TO WILDFIRE TEMPERATURES  

Microsoft Academic Search

A naturally occurring water resistant soil was exposed to different burning times and temperatures after which the soil samples were tested for non-wettability. The less intense treatments produced an extremely non-wettable condition. Temperatures of 800 and 900 degrees applied for 20 minutes completely destroyed the non-wettable property. Heat treatments within the realm of soil temperatures existing during wildfires were capable

L. F. DEBANO; J. S. KRAMMES

1966-01-01

277

Unity of mechanisms of water and wind erosion of soils  

NASA Astrophysics Data System (ADS)

An equation for the threshold velocity of the water or wind flow at which erosion of a homogeneous model soil begins was derived on the basis of accepted and explicitly formulated suppositions and limitations and tested using experimental data. The validity of the proposed mechanisms and equations describing the lifting force of the soil-eroding water or wind flow and the interaggregate cohesion in a model homogeneous incoherent soil was confirmed. The limit for the decrease in the threshold flow velocity with decreasing size of the soil particles (aggregates) was theoretically substantiated. The first unified equation of the threshold velocity of the water or wind flow for a homogeneous model soil in dimensionless variables was derived and experimentally justified.

Gendugov, V. M.; Glazunov, G. P.

2009-05-01

278

Optimum nitrogen rate for corn related to hillslope variability in soil water redistribution  

Technology Transfer Automated Retrieval System (TEKTRAN)

Improving site-specific N recommendations for corn (Zea mays L.) will depend on an improved understanding of the interactive effects of yield response to N and other independent variables. The objective of this study was to determine in-season soil water content redistribution (dW) for ten locations...

279

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

NASA Astrophysics Data System (ADS)

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

Sela, Shai; Svoray, Tal; Assouline, Shmuel

2013-04-01

280

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

SciTech Connect

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

Gillham, M.L.; Perry, D.A. [Oregon State Univ., Corvallis, OR (United States)

1995-09-01

281

Measurement of soil water potential over an extended range by polymer tensiometers: comparison with other instruments  

Microsoft Academic Search

In water scarce areas, plant growth and productivity can be severely hampered by irregular precipitation and overall water shortage. Root water uptake is mainly driven by matric potential gradients, but measurement of soil water matric potential is limited by the measurement range of water-filled tensiometers (-0.085 MPa). Other measurement techniques indirectly measure soil water potential by converting soil water content

M. J. van der Ploeg; H. P. Gooren; R. C. Hoogendam; G. Bakker; C. Huiskes; L. K. Koopal; H. Kruidhof; G. H. de Rooij

2007-01-01

282

A conceptual model of the soil water retention curve  

Microsoft Academic Search

A conceptual model based on the assumption that soil structure evolves from a uniform random fragmentation process is proposed to define the water retention function. The fragmentation process determines the particle size distribution of the soil. The transformation of particles volumes into pore volumes via a power function and the adoption of the capillarity equation lead to an expression for

S. Assouline; D. Tessier; A. Bruand

1998-01-01

283

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

SciTech Connect

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.

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

1999-08-01

284

Modeling gravity driven unstable flow in a water repellent soil  

Microsoft Academic Search

One mechanism for the initiation of unstable flow in porous media is a condition of hydrophobicity of the solid phase. Recent continuous and nondestructive measurements of water content distribution in a 200cm wide by 70cm deep trench of a Netherlands’ field soil containing a hydrophobic layer, reveals a complicated wetting pattern with fingered flow being quite prevalent. The soil profile

H. V. Nguyen; J. L. Nieber; C. J. Ritsema; L. W. Dekker; T. S. Steenhuis

1999-01-01

285

Climate Change Impacts on Soil and Water Conservation  

NASA Astrophysics Data System (ADS)

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 (SWCS), this question was answered with an emphatic yes. Impacts of projected precipitation changes on soil erosion and runoff are complex, display high regional and temporal variability, and depend on a number of nonclimatic factors, such as seasonal timing of agronomic practices and antecedent soil moisture conditions. Altogether, observed and projected changes in precipitation are believed to substantially heighten the risk of runoff, soil erosion, and related environmental consequences. This article reports on a follow-up workshop that called for a review of current approaches to estimating soil erosion and runoff on agricultural lands, enhancements to soil and water planning tools, and strengthening of conservation practices and standards.

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

2007-03-01

286

Soil surfactant stops water repellency and preferential flow paths  

Microsoft Academic Search

This study reports the effects of a soil surfactant on reduction and prevention of water repellency and preferential flow paths in a sandy soil of a golf course fairway, located at Bosch en Duin near Utrecht, the Netherlands. The golf course is constructed on inland dunes composed of fine sand with low organic matter content. The topsoil (0-25 cm) of

K. Oostindie; L. W. Dekker; J. G. Wesseling; C. J. Ritsema

2008-01-01

287

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...

288

Water and heat fluxes in desert soils: 2. Numerical simulations  

Microsoft Academic Search

Transient one-dimensional fluxes of soil water (liquid and vapor) and heat in response to 1 year of atmospheric forcing were simulated numerically for a site in the Chihuahuan Desert of Texas. The model was initialized and evaluated using the monitoring data presented in a companion paper (Scanlon, this issue). Soil hydraulic and thermal properties were estimated a priori from a

Bridget R. Scanlon; P. C. D. Milly

1994-01-01

289

Water and heat fluxes in desert soils 2. Numerical simulations  

Microsoft Academic Search

Transient one-dimensional fluxes of soil water (liquid and vapor) and heat in response to 1 year of atmospheric forcing were simulated numerically for a site in the Chihuahuan Desert of Texas. The model was initialized and evaluated using the monitoring data presented in a companion paper (Scanlon, this issue). Soil hydraulic and thermal properties were estimated a priori from a

Bridget R. Scanlon; P. C. D. Milly

1994-01-01

290

measurement of soil water content in the field  

Technology Transfer Automated Retrieval System (TEKTRAN)

Measurement of soil water content is a critical component of much hydrologic research that also has important practical applications. The combination of advances in electronics and the success of time domain reflectometry (TDR) has lead to the development of numerous new, relatively inexpensive soil...

291

Advances in modelling hysteretic water retention curve in deformable soils  

Microsoft Academic Search

Experimental findings on the hysteretic nature of the soil water retention curve, relating the degree of saturation to the matric suction, have generally to be superimposed with the aspects due to the deformability of the soil matrix. Indeed, most state-of-the-art models for retention curves only feature one of these two essential features, that is either capillary hysteresis or void ratio

Mathieu Nuth; Lyesse Laloui

2008-01-01

292

Modeling water retention curves of sandy soils using neural networks  

Microsoft Academic Search

We used neural networks (NNs) to model the drying water retention curve (WRC) of 204 sandy soil samples from particle-size distribution (PSD), soil organic matter content (SOM), and bulk density (BD). Neural networks can relate multiple model input data to multiple model output data without the need of an a priori model concept. In this way a high performance black-box

Marcel G. Schaap; Willem Bouten

1996-01-01

293

FREEZE-THAW AND WATER TENSION EFFECTS ON SOIL DETACHMENT  

Technology Transfer Automated Retrieval System (TEKTRAN)

Many areas of the northern United States and southern Canada, and particularly the four million ha of non-irrigated cropland in eastern Oregon and Washington, northern and southern Idaho, and northern Utah, experience severe water erosion under thawing soil conditions. Modeling soil erosion in these...

294

Stemflow-induced processes of soil water storage  

NASA Astrophysics Data System (ADS)

Compared to stemflow production studies only few studies deal with the fate of stemflow at the near-stem soil. To investigate stemflow contribution to the root zone soil moisture by young and adult babassu palms (Attalea speciosa Mart.), I studied stemflow generation, subsequent soil water percolation and root distributions. Rainfall, stemflow and perched water tables were monitored on an event basis. Perched water tables were monitored next to adult palms at two depths and three stem distances. Dye tracer experiments monitored stemflow-induced preferential flow paths. Root distributions of fine and coarse roots were related to soil water redistribution. Average rainfall-collecting area per adult palm was 6.4 m², but variability between them was high. Funneling ratios ranged between 16-71 and 4-55 for adult and young palms, respectively. Nonetheless, even very small rainfall events of 1 mm can generate stemflow. On average, 9 liters of adult palm stemflow were intercepted and stemflow tended to decrease for-high intensity rainfall events. Young babassu palms funneled rainfall via their fronds, directly to their subterranean stems. The funneling of rainfall towards adult palm stems, in contrast, led to great stemflow fluxes down to the soil and induced initial horizontal water flows through the soil, leading to perched water tables next to palms, even after small rainfall events. The perched water tables extended, however, only a few decimeters from palm stems. After perched water tables became established, vertical percolation through the soil dominated. To my knowledge, this process has not been described before, and it can be seen as an addition to the two previously described stemflow-induced processes of Horton overland flow and fast, deep percolation along roots. This study has demonstrated that Babassu palms funnel water to their stems and subsequently store it in the soil next to their stems in areas where coarse root length density is very high. This might partly explain the competitive position of babassu palms on pastures or secondary forests.

Germer, Sonja

2013-04-01

295

Export of Acidity in Drainage Water from Acid Sulphate Soils  

Microsoft Academic Search

Disturbed acid sulphate soils are potent sources of acidity in coastal waterways. Monitoring studies of the drainage water for sites at East Trinity, Cairns and Pimpama, south-east Queensland indicate that considerable acidity is found in the drainage water from these sites. Hydrogen (H+), ferrous (Fe2+) and aluminium (Al) ions are the dominant acid cations involved. When drainage water is mixed

F. J Cook; W Hicks; E. A Gardner; G. D Carlin; D. W Froggatt

2000-01-01

296

Effects of carbon dioxide enrichment and soil water on maize  

Microsoft Academic Search

The current global rise in atmospheric COâ concentration may lead to changes in yield and water use of crops. This study was done to determine the effects of increased COâ in combination with soil water levels on the growth, yield, transpiration, and water use efficiency of maize (Zea mays L.). Corn plants (cv. PX74) were grown in Opiki humic silty

K. M. King; D. H. Greer

2009-01-01

297

Non-isothermal soil water transport and evaporation  

Microsoft Academic Search

A detailed model was formulated to describe the non-isothermal transport of water in the unsaturated soil zone. The model consists of the coupled equations of mass conservation for the liquid phase, gas phase and water vapor and the energy conservation equation. The water transport mechanisms considered are convection in the liquid phase, and convection, diffusion and dispersion of vapor in

Jordi Grifoll; Josep Ma. Gastoa; Yoram Cohen

2005-01-01

298

Water holding of biochar amended SE Coastal Plain soils  

Technology Transfer Automated Retrieval System (TEKTRAN)

Because southeastern Coastal Plain soils are sandy, poorly aggregated, and low in organic matter, they have low water holding capacities. Water holding can be improved with biochar amendments that have the potential to increase aggregation and provide a medium of water storage in the char. Changes i...

299

Soil Water Content Measurement with a High-Frequency Capacitance Sensor  

Microsoft Academic Search

The calibration of a capacitance sensor (operating at 80–150 MHz) for monitoring soil water content ? is described. The capacitance of two electrodes inserted into soil is used to measure the dielectric properties of the soil, soil water content being the principal factor influencing these properties. A probe designed for measuring surface soil water content was used in laboratory trials

C. M. K. Gardner; T. J. Dean; J. D. Cooper

1998-01-01

300

Errors in water retention curves determined with pressure plates and their effect on soil hydraulic properties  

Microsoft Academic Search

Pressure plates are commonly used to measure the soil water retention curve. Low plate and soil conductance, lack of plate-soil contact, and soil dispersion, however, make this method often unreliable at low water potentials. In this paper, we investigate how errors in the determination of the water retention curve affect the soil hydraulic properties and the computation of plant available

M. Bittelli; M. Flury

2009-01-01

301

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

Microsoft Academic Search

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

Ö. Berglund; K. Berglund

2011-01-01

302

RELATION OF WATER TABLE DEPTH AND SOIL MORPHOLOGY IN TWO CLAY-RICH SOILS OF NORTHWESTERN OHIO1  

Microsoft Academic Search

Water table levels within the upper 165 cm of the soil and precipitation were measured over a three—yr period for two forested soils representative of clay-rich soils common throughout much of northwestern Ohio. The soils included very poorly drained Hoytville taxadjunct (fine, illitic, mesic Typic Haplaquept) and moderately well drained Glynwood (fine, illitic, mesic Aquic Hapludalf). A water table was

TED M. ZOBECK; A. RITCHIE

1984-01-01

303

Interaction between water and defective silica surfaces.  

PubMed

We use the density functional theory method to study dry (1 × 1) ?-quartz (0001) surfaces that have Frenkel-like defects such as oxygen vacancy and oxygen displacement. These defects have distinctively different effects on the water-silica interface depending on whether the adsorbent is a single water molecule, a cluster, or a thin film. The adsorption energies, bonding energies, and charge transfer or redistributions are analyzed, from which we find that the existence of a defect enhances the water molecule and cluster surface interaction by a large amount, but has little or even negative effect on water thin film-silica surface interaction. The origin of the weakening in film-surface systems is the collective hydrogen bonding that compromises the water-surface interaction in the process of optimizing the total energy. For clusters on surfaces, the lowest total energy states lower both the bonding energy and the adsorption energy. PMID:21428652

Chen, Yun-Wen; Cheng, Hai-Ping

2011-03-21

304

The estimation of soil water fluxes using lysimeter data  

NASA Astrophysics Data System (ADS)

The validation of soil water balance models regarding soil water fluxes in the field is still a problem. This requires time series of measured model outputs. In our study, a soil water balance model was validated using lysimeter time series of measured model outputs. The soil water balance model used in our study was the Hydrus-1D-model. This model was tested by a comparison of simulated with measured daily rates of actual evapotranspiration, soil water storage, groundwater recharge and capillary rise. These rates were obtained from twelve weighable lysimeters with three different soils and two different lower boundary conditions for the time period from January 1, 1996 to December 31, 1998. In that period, grass vegetation was grown on all lysimeters. These lysimeters are located in Berlin, Germany. One potential source of error in lysimeter experiments is preferential flow caused by an artificial channeling of water due to the occurrence of air space between the soil monolith and the inside wall of the lysimeters. To analyse such sources of errors, Hydrus-1D was applied with different modelling procedures. The first procedure consists of a general uncalibrated appli-cation of Hydrus-1D. The second one includes a calibration of soil hydraulic parameters via inverse modelling of different percolation events with Hydrus-1D. In the third procedure, the model DUALP_1D was applied with the optimized hydraulic parameter set to test the hy-pothesis of the existence of preferential flow paths in the lysimeters. The results of the different modelling procedures indicated that, in addition to a precise determination of the soil water retention functions, vegetation parameters such as rooting depth should also be taken into account. Without such information, the rooting depth is a calibration parameter. However, in some cases, the uncalibrated application of both models also led to an acceptable fit between measured and simulated model outputs.

Wegehenkel, M.

2009-04-01

305

Deforestation effects on soil moisture, streamflow, and water ...  

Treesearch

Forest Service National Links, Forest Service Home, Employment, Fire and Aviation ... that of forest soil throughout the growing season and especially in dry weather. ... With all components of the water balance quantified, including leakage, ...

306

Arsenic Treatment Technologies for Soil, Waste, and Water.  

National Technical Information Service (NTIS)

The purpose of this report is to provide a synopsis of the availability, performance, and cost of 13 arsenic treatment technologies for soil, water, and waste. Its intended audience includes hazardous waste site managers; generators and treaters of arseni...

2002-01-01

307

Criterion I: Soil and water conservation on rangelands [Chapter 2  

Treesearch

Jul 21, 2013 ... Laramie, WY: University of Wyoming. p. ... and maintenance of soil and water resources as a criterion of rangeland sustainability. ... Booth, D. Terrance; Borchard, Steven J.; Ypsilantis, William G.; Barrett, Richard H. 2010.

308

Soil water samplers in ion balance studies on acidic forest soils  

SciTech Connect

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

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

1986-04-01

309

Quantifying soil water effects on nitrogen mineralization from soil organic matter and from fresh crop residues  

Microsoft Academic Search

A loamy sand was incubated with and without addition of carrot leaves at six different water contents ranging from 6% to 20% (g 100 g-1 dry soil) and N mineralization was monitored during 98 days. We calculated zero- and first-order rates for mineralization in the unamended soil and first-order rates for N mineralization in the residue-amended soil. Although N mineralization

Stefaan De Neve; Georges Hofman

2002-01-01

310

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

NASA Astrophysics Data System (ADS)

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

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

2012-04-01

311

Monitoring stream aquifer interaction and ground water evapotranspiration in a humid shallow water table environment  

NASA Astrophysics Data System (ADS)

In humid environments, like the southern U.S., a dynamic shallow water table controls many hydrological fluxes across the ground water-vadose zone-atmosphere continuum. Heterogeneity in the vegetative cover of these environments influences lateral water table gradients in the surficial aquifer and associated stream aquifer interaction fluxes. In this study, we monitor the shallow water table fluctuation along two flow paths (transects) encompassing two types of vegetative landscapes: a pasture upland and a riparian zone with dense canopy lowland. The monitoring system consists of a series of observation wells along the flow path, soil moisture sensors, continuous rainfall gaging, total weather station, a stage recorder in the creek, and an evaporation pan. All instruments are automated with pressure transducers and data loggers providing continuous recording at time intervals in minutes. In addition, soil cores were removed and analyzed in the lab from selected locations and depths. The cores were used to determine hydraulic conductivity, aquifer thickness, and texture distribution of the shallow surficial aquifer. The objectives of this study are (1) to estimate specific yield variation with water table depth (specific yield is the depth of water released per unit fluctuation in water table), (2) to quantify ground water evapotranspiration as a function of depth to water table, (3) to compare groundwater evapotranspiration for the two vegetated landscapes.

Nachabe, M.; Thompson, D.; de Silva, M.

2003-04-01

312

Soil Management Plan For The Potable Water System Upgrades Project  

SciTech Connect

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.

Field, S. M.

2007-04-01

313

Influence of soil-structure interaction on floor response spectra  

SciTech Connect

A study was undertaken to investigate the influence of soil-structure interaction on floor response spectra developed in typical nuclear power plant structures. A horizontal earthquake time history, whose spectra envelops the Regulatory Guide 1.60 criteria and is scaled to a log peak acceleration, was used as input to structural models. Two different structural stick models were used, representing typical BWR and PWR facilities. By varying the structural and soil stiffness parameters, a wide range of system behaviors were investigated. Floor response spectra, required to assess equipment qualification, were of primary interest. It was found from a variation of parameter study that the interaction soil parameters, particularly radiation damping, greatly affect the nature of the calculated responses. 2 refs., 2 figs., 2 tabs.

Costantino, C.J.; Miller, C.A.; Curreri, J.R.

1985-01-01

314

Ant interactions with soil organisms and associated semiochemicals.  

PubMed

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

Vander Meer, Robert

2012-06-01

315

7 CFR 610.12 - Equations for predicting soil loss due to water erosion.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 false Equations for predicting soil loss due to water erosion. 610.12...CONSERVATION OPERATIONS TECHNICAL ASSISTANCE Soil Erosion Prediction Equations § 610.12 Equations for predicting soil loss due to water erosion. (a)...

2010-01-01

316

7 CFR 610.12 - Equations for predicting soil loss due to water erosion.  

Code of Federal Regulations, 2013 CFR

...2013-01-01 false Equations for predicting soil loss due to water erosion. 610.12...CONSERVATION OPERATIONS TECHNICAL ASSISTANCE Soil Erosion Prediction Equations § 610.12 Equations for predicting soil loss due to water erosion. (a)...

2013-01-01

317

7 CFR 610.12 - Equations for predicting soil loss due to water erosion.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 false Equations for predicting soil loss due to water erosion. 610.12...CONSERVATION OPERATIONS TECHNICAL ASSISTANCE Soil Erosion Prediction Equations § 610.12 Equations for predicting soil loss due to water erosion. (a)...

2009-01-01

318

Influence of rocks on soil temperature, soil water potential, and rooting patterns for desert succulents  

Microsoft Academic Search

At a site in the Sonoran Desert, subterranean rocks and exposed boulders affected soil water potential as well as root morphology and distribution. For Agave deserti, the number of lateral roots per unit length of main root was 11 times higher under rocks and six times higher alongside rocks than in rock-free regions. Total root length per unit soil volume

Park S. Nobel; Patsy M. Miller; Eric A. Graham

1992-01-01

319

Comparison of available soil water capacity estimated from topography and soil series information  

Microsoft Academic Search

We present a simple and generalized method to predict Available Soil Water Capacity (ASWC-TOP) for a given area using a topographic index, defined as ln(?\\/tan?), where ? is the upslope area draining past a certain point per unit width of slope, and ? is the local surface slope angle. The estimated results (ASWC-TOP) were then compared with the available soil

Daolan Zheng; E. R. Hunt; Steven W. Running

1996-01-01

320

Laboratory-field scaling of soil hydraulic properties: numerical validation based on soil water content measurements  

Microsoft Academic Search

Hydraulic properties should be determined at the scale of the process modeled. The methods to hydraulically characterize a soil in situ remain extremely difficult to implement, needing measurements of water content and pressure head with adequate time-depth resolution. The authors recently proposed a method of scaling, physically based, that allows to obtain the field soil hydraulic parameters from the laboratory

Antonello Bonfante; Antonio Coppola; Angelo Basile

2010-01-01

321

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...

322

Only one isotopic water world: relevant processes at the soil-vegetation-atmosphere interface (Invited)  

NASA Astrophysics Data System (ADS)

The stable water isotopes of oxygen and hydrogen have been used to gain process and system knowledge about flow pathways, residence times, mixing and redistribution for many decades. In recent years the processes due to water-ecosystem interactions have become more relevant and new ideas how processes effect the isotopic signature of soil water and runoff have been postulated (e.g. Brooks et al, 2009, doi:10.1038/NGEO722). On the other side, new measurement techniques have increased the sampling rate of stable water isotopes in soils and plants tremendously. This allows us, for example, to measure stable isotope profiles in soils up to several meters in depth with sub-decimetre sampling interval within 2 days. Using these rich datasets together with physically-based modelling of water and isotope fluxes in soils and plants we investigated distinct processes at the soil-vegetation-atmosphere interface that influence the isotopic signature in soil water, recharge and runoff. We hypothesize that a combination of distinct processes in combination with the local climate can considerably alter the isotopic signature of streamwater or groundwater and that these processes are often not adequately considered. A literature survey revealed eight mechanisms, which can be grouped into redistribution, selection, leakage and uptake effects that have the potential to modify the isotopic signal in runoff or recharge. Applying the proposed modelling concepts to a variety of climate and vegetation conditions we can predict the impact of individual and multiple effects on the isotopic signature in runoff as well as on the isotope profiles in soils. The predicted profiles match well with the observed profiles. This framework allows us finally to predict if the isotopic signature is significantly altered under specific soil-vegetation-atmosphere conditions.

Weiler, M.; Gimbel, K.; Weber, R.

2010-12-01

323

Consideration of Uncertainties in Soil-Structures Interaction Computations.  

National Technical Information Service (NTIS)

The report presents a summary of the results obtained in a study conducted to evaluate and quantify some important effects of soil-structure interaction (SSI) on the seismic response of Category I facilities. The current procedures utilized in SSI evaluat...

C. J. Constantino C. A. Miller

1992-01-01

324

[Effects of water supply and 3-methylphenol on soil microbial diversity and enzyme activity in wheat field intercropped with horse bean].  

PubMed

With pot experiment, this paper studied the effects of water supply levels (45%, 60% and 75% of soil water hold capacity) and allelochemical 3-methylphenol (300 x 10(-6) mol x kg(-1) soil) on the soil microbial diversity and enzyme activity in mono-cropped and horse bean-intercropped wheat fields during vigorous growth period. The results showed that with the decrease of water supply, the numbers of soil bacteria, fungi and actinomytes in the two fields decreased significantly, and 3-methylphenol enlarged this negative effect. 3-methylphonel had a negative effect on soil microbial diversity, but the increase of water supply could weaken this effect in intercropped field. The strongest allelopathic effect of 3-methylphenol was observed in mono-cropped field when the water supply was 75% of soil water hold capacity, while intercropping could maintain a relatively stable soil microbial diversity, compared to the mono-cropping with 3-methylphenol and low water supply. The allelopathic effect of 3-methylphenol was not significant on soil catalase activity, but significant on soil urease and phosphatase activities. Water supply level affected soil enzyme activity significantly, the lower the water supply level, the weaker the soil enzyme activity was. The interactions of water supply with 3-methyl phenol or cropping pattern were not significant, but intercropping could significantly affect the activities of soil catalase and phosphatase. PMID:17147169

Chai, Qiang; Huang, Gaobao; Huang, Peng

2006-09-01

325

How Soil Structure Influences the Topsoil Water Dynamics  

NASA Astrophysics Data System (ADS)

For various applications in soil science, hydrology and climatology it is important to estimate soil hydraulic properties over large areas. The methods to quantify them have been of limited success so far. One of the main difficulties is the influence of soil structure on infiltration and drainage of soils. The classical soil physical methods cannot be applied because they yield local measurements of properties, which are spatially averaged over sampling volumes of soil columns but not over plots or entire fields. One way out of this dilemma may be the use of microwave radiometry to quantify the dynamics of surface water contents and use this information as a proxy variable to estimate the hydraulic properties of the underlying soil. We present the results of a field experiment conducted on two sites of arable land near Zurich, Switzerland. Beside measuring the dynamics of the water content in the topsoil by a ground-based 11.4 GHz microwave radiometer, we carried out in-situ measurements of water content, temperature and matric potential. In addition we conducted a sprinkling experiment to test the infiltration behavior of the soil. The infiltration pattern, visualized with a blue dye tracer added to the infiltrating solution, showed that both soils were strongly susceptible to preferential flow. The reflectivity measured by the radiometer agreed well with the topsoil water dynamics observed from in-situ measurements. The correlation between them revealed a distinct hysteresis, which clearly separated wetting and drying branch of a cycle. The data obtained from the field experiments was used in MACRO 4.1, a one-dimensional non-steady state model of water flow and solute transport in field soils. This model can be run in two flow domains: a macropore domain (fast transport) and a domain representing the soil matrix (slow transport). The model structure therefore enables quantitative evaluation of the impact of preferential water flow in structured soils. This impact on the topsoil water dynamics measured by the 11.4 GHz radiometer will be evaluated. It will be tested whether the flow regimes can be separated based on the water dynamics in the topsoil.

Schneeberger, K.; Stamm, C.; Mätzler, C.; Wydler, H.; Flühler, H.

2001-12-01

326

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

NASA Astrophysics Data System (ADS)

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

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

2013-04-01

327

Soil water dynamics and deep soil recharge in a record wet year in the southern Loess Plateau of China  

Technology Transfer Automated Retrieval System (TEKTRAN)

Analysis of soil water dynamics and recharge is required to understand the regional soil water cycle processes and to guide agricultural production and ecological restoration. It has been reported that soil water reserve in high yield plots had been reduced by 270 mm after 13 years of continuous wh...

328

Soil water repellency: its causes, characteristics and hydro-geomorphological significance  

NASA Astrophysics Data System (ADS)

Water repellency (hydrophobicity) of soils is a property with major repercussions for plant growth, surface and subsurface hydrology, and for soil erosion. Important advances have been made since the late 1980s in identifying the range of environments affected by water repellency, its characteristics and its hydro-geomorphological impacts. This review summarises earlier work, but focusses particularly on these recent advances and identifies remaining research gaps. The associations of water repellency with (a) soils other than coarse-textured ones, (b) an expanding list of plant species, and (c) a widening range of climates other than seasonally dry types have been recurrent themes emphasised in recent literature. Nevertheless, knowledge about the extent of water repellency amongst world soils is still comparatively sparse. Its origin by the accumulation of long-chained organic compounds on or between soil particles is now widely accepted, but understanding of their exact chemical composition and means of attachment to particle surfaces remains incomplete. The transient nature of water repellency has been found to be mainly associated with fluctuations in soil moisture, but the precise processes and required conditions for the changes from hydrophobic to hydrophilic and vice versa are so far only poorly understood. Significant advances relating to the hydro-geomorphological impacts of hydrophobic layers have been made since the late 1980s in identifying and separating the various effects of such layers on surface and subsurface water flow. It has become evident that these effects in turn are influenced by variables such as the frequency and effectiveness of flow pathways through hydrophobic layers as well as their position and transitory behaviour. Recent literature has continued to highlight the role of water repellency in promoting soil erosion and it is now recognised that it can promote rainsplash detachment and soil loss not only by water, but also by wind. Major research gaps, however, remain in (a) isolating the erosional impact of water repellency from other factors, and (b) identifying the exact role of, and the interactions between the different variables controlling development and effectiveness of flow pathways through hydrophobic soil. Improved understanding of the effects of soil water repellency will enable its overall role in surface and subsurface hydrological and erosional processes to become more clearly defined.

Doerr, S. H.; Shakesby, R. A.; Walsh, R. P. D.

2000-08-01

329

A note on the soil-water conductivity of a fractal soil  

Microsoft Academic Search

We show that for a fractal soil the soil-water conductivity, K, is given by \\u000a$$\\\\frac{K}{{K_\\\\varepsilon }} = (\\\\Theta \\/\\\\varepsilon )^{2D\\/3 + 2\\/(3 - D)}$$\\u000a where \\u000a$$K_\\\\varepsilon$$\\u000a is the saturated conductivity, ? the water content, ? its saturated value and D is the fractal dimension obtained from reinterpreting Millington and Quirk's equation for practical values of the porosity ?, as \\u000a$$D

Carlos Fuentes; Michel Vauclin; Jean-Yves Parlange; Randel Haverkamp

1996-01-01

330

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

SciTech Connect

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

Wan, Shiqiang [Chinese Academy of Sciences; Norby, Richard J [ORNL; Childs, Joanne [ORNL; Weltzin, Jake [University of Tennessee, Knoxville (UTK)

2007-01-01

331

Reflectance of Vegetation, Soil, and Water.  

National Technical Information Service (NTIS)

The author has identified the following significant results. The Kubelka-Munk model, a regression model, and a combination of these models were used to extract plant, soil, and shadow reflectance components of vegetated surfaces. The combination model was...

C. L. Wiegand

1974-01-01

332

Estimating Soil Water Content Using Cokriging.  

National Technical Information Service (NTIS)

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 ...

S. R. Yates A. W. Warrick

1987-01-01

333

Evaluation of Hydrogel Application on Soil Water Retention Characteristics  

Microsoft Academic Search

Hydrogels can absorb irrigation and rain water and help to reduce deep percolation by using gravitational water as well as capillary water. The objective of this study was to evaluate the effect of hydrogels on soil water retention characteristic curve (WRC) using RETC computer model. The hydrogels, PR3005A and Tarawat A100 in four levels, 2, 4, 6, and 8 g\\/kg,

Jahangir Abedi-Koupai; Farahnaz Sohrab; Gareth Swarbrick

2008-01-01

334

Field compaction at different soil-water status: effects on pore size distribution and soil water characteristics of a Rhodic Ferralsol in Western Cuba  

Microsoft Academic Search

The level of compaction induced on cultivated fields through trafficking is strongly influenced by the prevailing soil-water status and, depending on the attendant soil degradation, vital soil hydraulic processes could be affected. Therefore, understanding the relationship between field soil-water status and the corresponding level of induced compaction for a given load is considered an imperative step toward a better control

Mohamed A Tarawally; M. E Frómeta; C. Alberto Itza

2004-01-01

335

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

PubMed

Soil water content strongly affects permafrost dynamics by changing the soil thermal properties. However, the movement of liquid water, which plays an important role in the heat transport of temperate soils, has been under-represented in boreal studies. Two different heat transport models with and without convective heat transport were compared to measurements of soil temperatures in four boreal sites with different stand ages and drainage classes. Overall, soil temperatures during the growing season tended to be over-estimated by 2-4°C when movement of liquid water and water vapor was not represented in the model. The role of heat transport in water has broad implications for site responses to warming and suggests reduced vulnerability of permafrost to thaw at drier sites. This result is consistent with field observations of faster thaw in response to warming in wet sites compared to drier sites over the past 30 years in Canadian boreal forests. These results highlight that representation of water flow in heat transport models is important to simulate future soil thermal or permafrost dynamics under a changing climate. PMID:21356544

Fan, Zhaosheng; Neff, Jason C; Harden, Jennifer W; Zhang, Tingjun; Veldhuis, Hugo; Czimczik, Claudia I; Winston, Gregory C; O'Donnell, Jonathan A

2011-02-26

336

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

USGS Publications Warehouse

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

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

2011-01-01

337

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

NASA Astrophysics Data System (ADS)

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.

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

2013-04-01

338

Groundwater Surface Water Interaction Effects on Pesticide Persistence and Transformation Pathways  

NASA Astrophysics Data System (ADS)

Historical DDT use at Point Pelee National Park (PPNP) has left a legacy of contamination found in the flora, fauna, soils, and groundwater. The transformation pathway and the rate of transformation of DDT to either DDE or DDD, and subsequent metabolites depends on many environmental factors including soil texture, soil moisture, temperature, organic carbon content, flooding, and microbial activity, (Guenzi and Beard 1968, 1976; Spencer et al. 1996; Aigner et al. 1998). Under aerobic conditions the transformation of DDT to DDE is the preferred pathway, whereas under anaerobic conditions, DDT to DDD is the preferred pathway. Also, the transformation of DDT to DDD under anaerobic conditions is faster than that for DDT to DDE under aerobic conditions. Given that one of the primary factors effecting the redox conditions of a soil is soil wetness, and that flooded soils tend to become anaerobic and reducing, it was hypothesized that there may be a relation between the dynamic nature of groundwater-surface water interactions at PPNP and the concentrations and proportions of DDT, DDE, and DDD. The soils are texturally sand and are mostly of the Brunisolic Soil Order (Inceptisols) with the Regosolic Soil Order (Entisols) on the sand dunes and the Organic Soil Order (Histosols) along the margins of the Marsh. The location of the groundwater-surface water interface coinciding with historic water levels within Lake Erie and the marsh has played a significant role.

Smith, J. E.; Crowe, A. S.; Marenco, N.

2004-05-01

339

Shear strength of surface soil as affected by soil bulk density and soil water content  

Microsoft Academic Search

This paper proposes a new method to measure the soil strength parameters at soil surface in order to explain the processes of soil erosion and sealing formation. To simulate the interlocks between aggregates or particles within top 2mm of the soil, a piece of sandpaper (30 particles cm?2) was stuck on the bottom face of a plastic box of diameter

B Zhang; Q. G Zhao; R Horn; T Baumgartl

2001-01-01

340

Study of Radiation Damping and Soil-Structure Interaction Effects in the Centrifuge.  

National Technical Information Service (NTIS)

The report describes the experimental phase of an ongoing research project on dynamic soil-structure interaction effects. The details of an in-depth experimental study of radiation damping and dynamic soil-structure interaction performed in the Princeton ...

J. H. Prevost K. Weissman

1988-01-01

341

Effect of soil salinity and soil water availability on growth and chemical composition of Sorghum halepense L  

Microsoft Academic Search

Summary  Effects of soil salinity and soil water regime on growth and chemical composition ofSorghum halepense L. was studied with a view to evaluating its potential as a forage crop in saline soils. The experiment was conducted under\\u000a controlled conditions using pot-culture with three levels of soil salinity (ECe 0.5, 5.0, 10.0 ds\\/m) and three soil water regimes (60%, 40% and

Anubha Sinha; S. R. Gupta; R. S. Rana

1986-01-01

342

Soil-structure interaction in nuclear power plants: a comparison of methods. [Calculation of soil-structure interactions for nuclear power plant site selection  

Microsoft Academic Search

We performed an extensive parametric survey to analyze the differences between two methods of calculating soil-structure interaction. One method involves discretizing the soil-structure system and solving for the complete response with the LUSH computer code. The other method solves for the lumped mass structural response with Whitman soil springs. Twelve soil-structure interaction problems are solved by each of these methods.

Wight

1976-01-01

343

Mechanical impedance of soil crusts and water content in loamy soils  

NASA Astrophysics Data System (ADS)

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).

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

2013-04-01

344

Soil water balance and ecosystem response to climate change.  

PubMed

Some essential features of the terrestrial hydrologic cycle and ecosystem response are singled out by confronting empirical observations of the soil water balance of different ecosystems with the results of a stochastic model of soil moisture dynamics. The simplified framework analytically describes how hydroclimatic variability (especially the frequency and amount of rainfall events) concurs with soil and plant characteristics in producing the soil moisture dynamics that in turn impact vegetation conditions. The results of the model extend and help interpret the classical curve of Budyko, which relates evapotranspiration losses to a dryness index, describing the partitioning of precipitation into evapotranspiration, runoff, and deep infiltration. They also provide a general classification of soil water balance of the world ecosystems based on two governing dimensionless groups summarizing the climate, soil, and vegetation conditions. The subsequent analysis of the links among soil moisture dynamics, plant water stress, and carbon assimilation offers an interpretation of recent manipulative field experiments on ecosystem response to shifts in the rainfall regime, showing that plant carbon assimilation crucially depends not only on the total rainfall during the growing season but also on the intermittency and magnitude of the rainfall events. PMID:15540152

Porporato, Amilcare; Daly, Edoardo; Rodriguez-Iturbe, Ignacio

2004-09-22

345

Hierarchical Measurement of Field-Scale Soil Water Content  

Microsoft Academic Search

Water content is a key variable in terrestrial systems. It is closely related to soil texture, hence varies continuously as well as discontinuously on many spatial and temporal scales. Measuring water content at large scales is thus a significant challenge. We demonstrate the relative merits of two electromagnetic methods -- TDR (time-domain reflectometry) and GPR (ground-penetrating radar) -- both of

K. Roth; U. Wollschläger

2006-01-01

346

Verification of Ground Penetrating Radar for Soil Water Content Measuring  

Microsoft Academic Search

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

O. Ermolaeva; A. Zeiliguer

2009-01-01

347

Water-facilitated dispersal of inoculant Bradyrhizobium japonicum in soils  

Microsoft Academic Search

Studies were performed to assess the influence of percolating water and an advancing wetting front on the transport of Bradyrhizobium japonicum in sand and silt loam soils, and to assess the influence of clay content on water-facilitated dispersal of these bacteria in a sand amended with various amounts of kaolin. The data obtained showed that movement of B. japonicum in

G. A. Breitenbeck; H. Yang; E. P. Dunigan

1988-01-01

348

Water Intake by Soil, Experiments for High School Students.  

ERIC Educational Resources Information Center

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

1969

349

Soil and Water Management in West Africa: An Economic Analysis.  

National Technical Information Service (NTIS)

Water conservation is a necessary component in efforts to raise the productivity of traditional rain-fed farming in West Africa. Soil-water balance relationships and a whole-farm modeling approach are used to estimate benefits of conservation on a typical...

J. C. Day

1989-01-01

350

Characteristics of soil moisture in permafrost observed in East Siberian taiga with stable isotopes of water  

Microsoft Academic Search

Soil moisture and its isotopic composition were observed at Spasskaya Pad experimental forest near Yakutsk, Russia, during summer in 1998, 1999, and 2000. The amount of soil water (plus ice) was estimated from volumetric soil water content obtained with time domain reflectometry. Soil moisture and its 18O showed large interannual variation depending on the amount of summer rainfall. The soil

A. Sugimoto; D. Naito; N. Yanagisawa; K. Ichiyanagi; N. Kurita; J. Kubota; T. Kotake; T. Ohata; T. C. Maximov; A. N. Fedorov

2003-01-01

351

Effect of drop energy and soil and water chemistry on infiltration and erosion  

Microsoft Academic Search

The effect of water salinity, soil sodicity, and raindrop energy on final infiltration rate, wash erosion, and soil particle splash of two kaolinitic soils (ustochrepts and paleudalf) was studied. Final infiltration rate decreased with the increase in soil sodicity and drop energy and increased with the increase of water salinity. Wash erosion and splash increased with the increase in soil

M. Agassi; D. Bloem; M. Ben-Hur

1994-01-01

352

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...

353

A multimedia and interactive approach to teach soil science  

NASA Astrophysics Data System (ADS)

Soil Science is a discipline concerned with a material that has unique features and behaviours (Churchman, 2010). Thus, teachers of Soil Science need to be experienced with Soil Science practices and must appreciate the complexities and relationships inherent within the discipline (Field et al, 2011). But when soil science had to be taught not by specialists, for instance in the introductory courses of earth and environmental sciences Degrees or in Secondary School, adequate material cannot be found. For this reason, multimedia and interactive programmes have been developed and showed here. EDAFOS is an e-learning resource that provides a comprehensive review of the fundamental concepts on soil science and reveals it as the living skin of planet Earth (European Commission, 2006). This programme is available via website (www.cienciadelsuelo.es) both in Spanish and, more recently, also in English. Edafos is a programme with different modules, which after outlining the study of soil components goes on to examine the main factors and processes of soil genesis explaining the mechanisms of soil processes. By the use of animations, the vital functions of soil are explained. The program ends with a section of multiple-choice exercises with self-assessment. To complement this program, virtual visits to the field are showed in the program iARASOL (www.suelosdearagon.es), in a time when field trips are gradually diminishing due to insufficiency in time and budget, as well as safety concerns (Çaliskan, 2011). In this case, the objective of iARASOL is to set out that soil vary from place to place not randomly, but in a systematic way, according to landscape units; therefore, graduates can classify the soils using the WRB system (IUSS, 2007). It presents diverse types of data and images instantly, from a variety of viewpoints, at many different scales and display non-visual information in the field. Both programs provide an additional source of information to supplement lectures, real field visits and other learning activities on soil sciences. The development of these programmes has been sponsored by the Spanish Ministry of Science and Innovation (Fundación Española para la Ciencia y la Tecnología, FECYT) and it has won the "Félix de Azara" Award (2011). Çaliskan, O. (2011). Virtual field trips in education of earth and environmental sciences. Procedia Social and Behavioral Sciences, 15: 3229-3243. Churchman, G. J. (2010). The philosophical status of soil science. Geoderma 157, 214-221. European Commission (2006). Thematic strategy for soil protection. COM (2006) 231. Field D.J., A. J. Koppi, L. E. Jarrett, L. K. Abbott, S. R. Cattle, C. D. Grant, A. B. McBratney, N. W. Menzies, A. J. Weatherley (2011). Soil Science teaching principles. Geoderma, 167-168: 9-14. IUSS Working Group WRB (2007). World Reference Base for Soil Resources 2006, fist update 2007. World Soil Resources Reports n° 103. FAO. Rome.

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

2012-04-01

354

Effect of Ionic Soil Stabilizers on Soil-Water Characteristic of Special Clay  

NASA Astrophysics Data System (ADS)

The engineering properties of special clay are conventionally improved through the use of chemical additive such as ionic soil stabilizer (ISS). Such special clays are often referred to as stabilized or treated clays. The soil-water characteristic curves (SWCC) of special clays from Henan province and Hubei province were measured both in natural and stabilized conditions using the pressure plate apparatus in the suction range of 0-500 kPa. The SWCC results are used to interpret the special clays behavior due to stabilizer treatment. In addition, relationships were developed between the basic clay and stabilized properties such as specific surface area and pore size distribution. The analysis showed that specific surface area decreases, cumulative pore volume and average pore size diameter decrease, dehydration rate slows and the thickness of water film thins after treatment with Ionic Soil Stabilizer. The research data and interpretation analysis presented here can be extended to understand the water film change behaviors influencing the mechanical and physical properties of stabilized special clay soils. KEY WORDS: ionic soil stabilizer, special clay, pore size diameter, specific surface area, soil water characteristic curve, water film

Cui, D.; Xiang, W.

2011-12-01

355

Interactive influences of silvicultural management and soil chemistry upon soil microbial abundance and nitrogen mineralization  

Microsoft Academic Search

The purpose of this study was to determine whether soil acidification, a widespread, chronic mode of disturbance and forest thinning, a site specific acute disturbance, produced interactive effects capable of producing changes in more general ecosystem properties and processes. Two forested sites in the Daniel Boone National Forest, KY which were similar in history, management, and parent material but which

Sherri Jeakins Morris; R. E. J. Boerner

1998-01-01

356

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

Microsoft Academic Search

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

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

1995-01-01

357

Molecular Indicators of Soil Humification and Interaction with Heavy Metals  

SciTech Connect

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.

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

2003-03-26

358

Interactions of aromatic radicals with water.  

PubMed

The interactions of the benzyl radical (1), the anilinyl radical (2), and the phenoxyl radical (3) with water are investigated using density functional theory (DFT). In addition, we report dispersion-corrected DFT-D molecular dynamics simulations on these three systems and a matrix isolation study on 1-water. The radicals 1-3 form an interesting series with the number of lone pairs increasing from none to two. The anilinyl and benzyl radicals can act as Lewis base through their unpaired electrons, the lone pairs of the heteroatoms, or the doubly occupied ? orbitals of the aromatic system. Matrix isolation experiments provide evidence for the formation of a ? complex between 1 and water. By combining computational and experimental techniques we identify the possible interactions between the aromatic radicals 1-3 and water, predict the structure and vibrational spectra of the resulting complexes, and analyze the effects of substitution and temperature. PMID:23335277

Crespo-Otero, Rachel; Bravo-Rodriguez, Kenny; Roy, Saonli; Benighaus, Tobias; Thiel, Walter; Sander, Wolfram; Sánchez-García, Elsa

2013-01-18

359

Water quality and surfactant effects on the water repellency of a sandy soil  

Technology Transfer Automated Retrieval System (TEKTRAN)

Differences in irrigation water quality may affect the water repellency of soils treated or untreated with surfactants. Using simulated irrigations, we evaluated water quality and surfactant application rate effects upon the water repellency of a Quincy sand (Xeric Torripsamment). We used a split ...

360

Modeling the water balance and soil water fluxes in a fast growing Eucalyptus plantation in Brazil  

Microsoft Academic Search

A five-layered water balance model, with water movement between layers along hydraulic gradients, was developed and parameterized for a eucalypt plantation (Eucalyptus grandis Hill ex. Maiden hybrids) in Brazil. Available soil water controls stomatal conductance and hence transpiration, which is calculated by the Penman–Monteith equation. The model accounts for changes in the depths of the water table. Calculations are supported

J. V. Soares; A. C. Almeida

2001-01-01

361

Root Water Extraction and Limiting Soil Hydraulic Conditions Estimated by Numerical Simulation  

Microsoft Academic Search

Root density, soil hydraulic functions, and hydraulic head gra- dients play an important role in the determination of transpiration- rate-limiting soil water contents. We developed an implicit numerical root water extraction model to solve the Richards equation for the modeling of radial root water extraction. The average soil water con- tent at the moment root water potential dropped below a

Quirijn de Jong van Lier; Klaas Metselaar; Jos C. van Dam

2006-01-01

362

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...

363

Soil water repellency: the knowledge base, advances and challenges  

NASA Astrophysics Data System (ADS)

The topic of soil water repellency (SWR or soil hydrophobicity) has moved from being perhaps a little known curiosity a few decades ago to a well established sub-discipline of soil physics and soil hydrology. In terms of the number of journal publications, SWR is comparable with other physical soil properties or processes such as crusting, aggregation or preferential flow. SWR refers to a condition when soil does not wet readily when in contact with water. This may be evident at the soil surface, when SWR leads to prolonged ponding on soils despite the presence of sufficient pore openings, or in the soil matrix, as manifest by enhanced uneven wetting and preferential flow that is not caused by structural in homogeneity. Amongst major milestones advancing the knowledge base of SWR have been the recognition that: (1) many, if not most, soils can exhibit SWR when the soil moisture content falls below a critical threshold, (2) it can be induced (and destroyed) during vegetation fires, but many soils exhibit SWR irrespective of burning, (3) it can be caused, in principle, by a large variety of naturally-abundant chemical compounds, (4) it is typically highly variable in space, time and its degree (severity and persistence), and (5) its impacts on, for example, soil hydrology, erosion and plant growth have the potential to be very substantial, but also that impacts are often minor for naturally vegetated and undisturbed soils. Amongst the key challenges that remain are: (a) predicting accurately the conditions when soils prone to SWR actually develop this property, (b) unravelling, for fire effected environments, to what degree any presence of absence of SWR is due to fire and post-fire recovery, (c) the exact nature and origin the material causing SWR at the molecular level in different environments, (d) understanding the implications of the spatial and temporal variability at different scales, (e) the capability to model and predict under which environmental conditions its impacts are of significance, and (f) what changes to SWR and its implications we can expect under future climatic and land management conditions. This presentation aims to provide a brief overview of the main milestones reached to date in SWR research and of some of the key challenges for future research in this rapidly growing field.

Doerr, S. H.

2012-04-01

364

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

Microsoft Academic Search

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

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

2008-01-01

365

An Improved Model for Predicting Soil Thermal Conductivity from Water Content at Room Temperature  

Microsoft Academic Search

The thermal conductivity and water content relationship is required for quantitative study of heat and water transfer processes in saturated and unsaturated soils. In this study, we developed an improved model that describes the relationship between thermal conductivity and volumetric water content of soils. With our new model, soil thermal conductivity can be estimated using soil bulk density, sand (or

Sen Lu; Tusheng Ren; Yuanshi Gong; Robert Horton

2007-01-01

366

Soil water and temperature patterns in an arid desert dune sand  

Microsoft Academic Search

Under arid natural conditions, soil water content governs and limits the number and size of perennial plant species. Thus, plant-available soil water is the main constraint for sustainable control of desert encroachment. To evaluate possibilities for re-vegetation of bare sand surfaces, soil water and temperature patterns for typical sand dunes in a desert climate were investigated. Bare and vegetated soil

Ronny Berndtsson; Kanichi Nodomi; Hiroshi Yasuda; Thomas Persson; Heshen Chen; Kenji Jinno

1996-01-01

367

Desert shrub water relations with respect to soil characteristics and plant functional type  

Microsoft Academic Search

Summary 1. Soil characteristics influence plant communities in part through water relations. Hypothetically, finer textured soils in arid climates should be associated with more negative plant and soil water potentials during drought, greater resistance of xylem to cavitation, and shallower root systems than coarse soils. 2. These hypotheses were tested by comparing the water relations of Great Basin shrubs growing

J. S. Sperry; U. G. Hacke

2002-01-01

368

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 ...

369

Water and heat fluxes in desert soils: 2. Numerical simulations  

NASA Astrophysics Data System (ADS)

Transient one-dimensional fluxes of soil water (liquid and vapor) and heat in response to 1 year of atmospheric forcing were simulated numerically for a site in the Chihuahuan Desert of Texas. The model was initialized and evaluated using the monitoring data presented in a companion paper (Scanlon, this issue). Soil hydraulic and thermal properties were estimated a priori from a combination of laboratory measurements, models, and other published information. In the first simulation, the main drying curves were used to describe soil water retention, and hysteresis was ignored. Remarkable consistency was found between computed and measured water potentials and temperatures. Attenuation and phase shift of the seasonal cycle of water potentials below the shallow subsurface active zone (0.0- to 0.3-m depth) were similar to those of temperatures, suggesting that water potential fluctuations were driven primarily by temperature changes. Water fluxes in the upper 0.3 m of soil were dominated by downward and upward liquid fluxes that resulted from infiltration of rain and subsequent evaporation from the surface. Upward flux was vapor dominated only in the top several millimeters of the soil during periods of evaporation. Below a depth of 0.3 m, water fluxes varied slowly and were dominated by downward thermal vapor flux that decreased with depth, causing a net accumulation of water. In a second simulation, nonhysteretic water retention was instead described by the estimated main wetting curves; the resulting differences in fluxes were attributed to lower initial water contents (given fixed initial water potential) and unsaturated hydraulic conductivities that were lower than they were in the first simulation. Below a depth of 0.3 m, the thermal vapor fluxes dominated and were similar to those in the first simulation. Two other simulations were performed, differing from the first only in the prescription of different (wetter) initial water potentials. These three simulations yielded identical solutions in the upper 0.2 m of soil after infiltration of summer rain; however, the various initial water potentials were preserved throughout the year at depths greater than 0.2 m. Comparison of all four simulations showed that the predominantly upward liquid fluxes below a depth of 0.2 m were very sensitive to the differences in water retention functions and initial water potentials among simulations, because these factors strongly affected hydraulic conductivities. Comparison of numerical modeling results with chemical tracer data showed that values of downward vapor flux below the surface evaporation zone were of the same order of magnitude as those previously estimated by analysis of depth distributions of bomb 3H (volatile) and bomb 36Cl (nonvolatile).

Scanlon, Bridget R.; Milly, P. C. D.

1994-03-01

370

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

NASA Astrophysics Data System (ADS)

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.

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

2012-04-01

371

Modelling the relative permittivity of soils using soil hygroscopic water content  

Microsoft Academic Search

A model describing the increase in the relative permittivity of water with distance from the soil mineral surface is presented. The model assumes an exponential increase in the value of permittivity with increasing distance from the mineral surface; arguments are presented supporting this approach. The volume of bound water (within the bandwidth of time domain reflectometry, (TDR) 0.01–1GHz) is considered

D. A. Robinson; J. D. Cooper; C. M. K. Gardner

2002-01-01

372

Plant response to the soil environment: An analytical model integrating yield, water, soil type, and salinity  

Microsoft Academic Search

An accessible solution capable of reliably predicting plant-environmental interrelationships for variable species, climates, soils, and management options is a necessary tool for creating sustainable agriculture and environmental preservation. A mechanism-based analytical solution, the first of its kind that considers multiple environmental variables and their combined effects on plant response, was developed and tested. Water uptake by plants, water and salt

Uri Shani; Alon Ben-Gal; Effi Tripler; Lynn M. Dudley

2007-01-01

373

Surface reactions of chromium in soils and waters  

Microsoft Academic Search

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

Scott E. Fendorf

1995-01-01

374

Grain sorghum growth, water use, and yield in contrasting soils  

Microsoft Academic Search

Soil characteristics and the climate in which they occur help control crop growth and yield. We conducted a study to determine the influence of contrasting soils on grain sorghum (Sorghum bicolor Moench) growth, water use, and yield. In 1992 and 1993, grain sorghum (‘DK-46’) was grown in 0.75-m rows with 16 plants m?2 at Bushland, TX in lysimeters containing monolithic

J. A. Tolk; T. A. Howell; J. L. Steiner; S. R. Evett

1997-01-01

375

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

NASA Astrophysics Data System (ADS)

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 the bulk soil microbial community and selected soil processes. Plant species were associated with distinct ecosystem process rates such as net nitrogen mineralization, nitrification, decomposition and soil respiration. Bacterial community substrate utilization profiles differed among different plant species and were related to labile soil C. DNA-based fingerprints of bacterial, ammonia oxidizer, and fungal communities did not generally differ in soils planted to different species; however, these microbial community profiles did strongly correlate to rates of decomposition. Terminal Restriction Fragment Length Polymorphism (TRFLP) analysis of soil microbial communities showed that the lupine community was distinct from the other four plant-associated communities. Phospholipid fatty acid (PLFA) patterns also failed to distinguish differences in the overall microbial communities associated with the five different moncultures. Interestingly, PLFA biomarker 16:1w5, indicative of AM fungi, differed among plant species treatments. This PLFA biomarker and bacterial TRFLP patterns were related to decomposition rates of a common litter. In summary, large functional differences were found between field plots with different plant species and the composition of the microbial communities was closely related to some of the functions assessed, independent of plant species. Only small plant-induced changes in microbial community composition were detected, yet apparently these changes had significant impact on function. Our analyses were not specifically targeted to microsites with high activity (such as rhizosphere soil) and our DNA and PLFA-based analyses included a potentially huge "dormant" community of soil microorganisms. While our analyses could detect little impact of plant species on overall microbial community profiles, a smaller active-fraction of the soil microbial community may have been more significantly affected.

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

2002-12-01

376

The effects of water exposure, soil conditions, and fungus exposure on hatching of the larval lone star tick, Amblyomma americanum (Acari: Ixodidae)  

Microsoft Academic Search

We examined whether water functions as a developmental cue for hatching in the lone star tick, Amblyomma americanum. The experiments examined various exposure routes to water: submersion, relative humidity and an ecologically relevant setup of moist soil along with soil fungi to mimic fungus–egg interactions at oviposition sites. We demonstrate that eggs survive for up to a week underwater; increasing

Jay A. Yoder; Benjamin A. Rausch; Brian Z. Hedges; Sarah E. Stueber; Andrew J. Jajack; Joshua B. Benoit

2012-01-01

377

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

PubMed Central

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.

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

2010-01-01

378

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

PubMed

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

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

2010-07-01

379

Interactions of low-level, liquid radioactive wastes with soils. 1. Behavior of radionuclides in soil-waste systems  

Microsoft Academic Search

The characteristics of radioactive wastes and soils vary over a wide range. Liquid radioactive waste entering the environment will eventually contact the soil or geological matrix; interactions will be determined by the chemical and physical nature of the liquid, as well as the soil matrix. We report here the results from an investigation of certain of those characteristics as they

E. B. Fowler; E. H. Essington; W. L. Polzer

1981-01-01

380

Seasonally frozen soil's effect on stochastic response of masonry minaret–soil interaction systems to random seismic excitation  

Microsoft Academic Search

Seasonal freezing, causing significant change in the stiffness of soils and its potentially significant impact on the seismic response of soil–structure interaction systems, is an accepted principle. Since many masonry structures in cold regions are located in seismic active zones, determining the effect of seasonally frozen soil on the stochastic response of masonry structures subjected to random seismic excitation becomes

Kemal Hac?efendio?lu

2010-01-01

381

Experimental and numerical studies of the 18O exchange between CO2 and water in the atmosphere soil invasion flux  

NASA Astrophysics Data System (ADS)

The 18O/16O ratio of CO2 is a potentially powerful tracer of carbon dioxide fluxes from the soil to the atmosphere, which is influenced by complex interactions involving both biotic and abiotic soil processes. We use a simplified experimental approach and numerical simulations to examine in isolation the 18O exchange between CO2 and soil water associated with the abiotic invasion of atmospheric CO2 into soil. This allowed us to verify, in particular, whether the 18O of the retro-diffusion flux of CO2 from the soil reflects 18O equilibration with water at the soil surface, or at some depth. Sterile soil samples with known water isotopic composition were placed in a closed box attached to a specially designed flow chamber and the changes in ?18O of CO2 between the chamber inlet and outlet, due only to invasion effects, were determined. Numerical simulations constrained by the laboratory gas exchange measurements indicated that between the two commonly used diffusion models [Penman, H.L. (1940). Gas and vapor movements in soil, 1: the diffusion of vapors through porous solids. Int. J. Agric. Sci.30, 437 462; Moldrup, P., Olesen, T., Yamaguchi, T., Schjonning, P., Rolston, D.E. (1999). Modeling diffusion and reaction in soils, IX, the Backingham Burdine Campbell equation for gas diffusivity in undisturbed soil. Soil Sci.164, 542 551], only the former provided good agreement with the measurements over a wide range of soil water contents. Based on the model calculations constrained by experimental data, and on comparison of characteristic diffusion/reaction times, we conclude that the depth required for full CO2 water 18O equilibration ranges between 2 and 8.5 cm. The depth depends, in order of importance, on (1) soil moisture content; (2) temperature, which dominates the rate of hydration isotopic exchange; (3) CO2 residence time, which is determined by the time of replacement of the column air above the soil; and (4) soil structure, including porosity, tortuosity and grain size, with the later probably influencing the water surface area exposed to CO2 exchange. Using field data from a semi-arid forest site in Israel, numerical simulations indicated that the 18O full equilibrium depth varied at this site between 4 cm (January) and 8 cm (November), being sensitive mostly to temperature and soil water content. Deepening of the equilibration depth as the soil dries should limit the effects of 18O evaporative enrichment at the surface on the isotopic composition of the soil atmosphere CO2 flux.

Kapiluto, Yaacov; Yakir, Dan; Tans, Pieter; Berkowitz, Brian

2007-06-01

382

Spatial Variability of Physical Properties of a Tropical Soil. II. Soil Water Retention Curves and Hydraulic Conductivity.  

National Technical Information Service (NTIS)

The characterization of a field site from the soil physics point of view, the improvement of the use of soil and water resources under a particular condition and the development of means for controlling the dynamics of soil-water movement are presented. S...

K. Reichardt P. L. Libardi S. V. Queiroz F. Grohmann

1976-01-01

383

Precision and accuracy of three alternative instruments for measuring soil water content in two forest soils of the Pacific Northwest  

Microsoft Academic Search

We compared the accuracy and precision of three devices for measuring soil water content in both natural and repacked soils and evaluated their temperature sensitivity. Calibrations were developed for a capacitance instrument (ECH2O), a time domain reflectometry cable tester (CT), and a water content reflectometer (WCR) in soils collected from the Wind River and H.J. Andrews Experimental Forests. We compared

Nicole M. Czarnomski; Georgianne W. Moore; Tom G. Pypker; Julian Licata; Barbara J. Bond

2005-01-01

384

Behavior of bromobutide in paddy water and soil after application.  

PubMed

Behavior of the herbicide bromobutide, (RS)-2-bromo-N-(?,?-dimethylbenzyl)-3,3-dimethylbutyramide, in paddy water and soil after application to paddy fields was investigated to evaluate the degradation to bromobutide-debromo, N-(?,?-dimethylbenzyl)-3,3-dimethylbutyramide, and runoff of the herbicide. The respective maximum concentrations of bromobutide and the metabolite were 1,640–2,230 and 11.1–15.8 ?g/L in the paddy water, and 2,210–4,140 ?g/kg dry and 74–119 ?g/kg dry in the paddy soil, respectively. The runoff ratios of the applied bromobutide from the paddy fields were calculated as 28 ± 16%. The respective mean values of the half-lives of bromobutide in the paddy water and the soil were 2.7 ± 0.34 days and 6.9 ± 2.6 days, respectively. PMID:22297629

Morohashi, Masayuki; Nagasawa, Shunsuke; Enya, Nami; Suzuki, Kazuyuki; Kose, Tomohiro; Kawata, Kuniaki

2012-04-01

385

DenNit – Experimental analysis and modelling of soil N 2 O efflux in response on changes of soil water content, soil temperature, soil pH, nutrient availability and the time after rain event  

Microsoft Academic Search

To quantify the effects of soil temperature (Tsoil), and relative soil water content (RSWC) on soil N2O emission we measured N2O soil efflux with a closed dynamic chamber in situ in the field and from soil cores in a controlled climate chamber experiment. Additionally we analysed the effect of soil acidity, ammonium, and nitrate concentration in the field. The analysis

Sascha Reth; Kerstin Hentschel; Matthias Drösler; Eva Falge

2005-01-01

386

Modeling plant competition for soil water balance in Water-limited Mediterranean Ecosystems  

NASA Astrophysics Data System (ADS)

In heterogeneous ecosystems, such Mediterranean ecosystems, contrasting plant functional types (PFTs, e.g., grass and woody vegetation) compete for the water use. In these complex ecosystems current modeling approaches need to be improved due to a general lack of knowledge about the relationship between ET and the plant survival strategies for the different PFTs under water stress. Indeed, still unsolved questions are: how the PFTs (in particular the root systems) compete for the water use, the impact of this competition on the water balance terms, and the role of the soil type and soil depth in this competition. For this reasons an elaborated coupled Vegetation dynamic model (VDM) - land surface model (LSM) model able to also predict root distribution of competing plant systems is developed. The transport of vertical water flow in the unsaturated soil is modelled through a Richards’ equation based model. The water extraction (sink) term is considered as the root water uptake. Two VDMs predict vegetation dynamics, including spatial and temporal distribution/evolution of the root systems in the soil of two competing species (grass and woody vegetation). An innovative method for solving the unlinear system of predicting equations is proposed. The coupled model is able to predict soil and root water potential of the two competing plant species. The model is tested for the Orroli case study, situated in the mid-west of Sardinia within the Flumendosa river watershed. The site landscape is a mixture of Mediterranean patchy vegetation types: trees, including wild olives and coark oaks, different shrubs and herbaceous species. In particular two contrasting plant functional types (grass and woody vegetation) have been included. The model well predict the soil moisture and vegetation dynamics for the case study, and significantly different root potentials are predicted for the two PFTs, highlighting the root competition for the water use. The soil depth is low in the case study, while the Flumendosa basin is characterized by soils of different type and depth (more silty and deep nearly the river valley), such as typical in Mediterranean basins. A sensitivity analysis to the soil depth and soil type is performed for investigating their influences on the PFT dynamics and soil water balance. The influence of vegetation cover distribution of each plant type is also investigated. Results show that the plant compete differently according to site soil characteristics, and the impact of vegetation dynamics on the soil water balance terms is significant and cannot be neglected in current hydrological approaches.

Cortis, C.; Montaldo, N.

2009-12-01

387

Soil water Storage, from Profile to Watershed (Invited)  

NASA Astrophysics Data System (ADS)

At present, stream discharge from a watershed is the only integrated hydrologic measurement that is practical at many scales. For this reason, an enormous effort has gone into the description of water leaving watersheds as streamflow. Relatively little attention has been paid to water that is retained on the watershed. This water is critical for estimating upland processes such as carbon sequestration, transpiration and contaminant transport or for predicting streamflow using distributed modeling approaches. We present field data illustrating how soil water, viewed in a storage context, can be useful for describing both upland processes in a spatially distributed manner and for estimating watershed-scale stream discharge. Point scale soil water data, which is becoming increasingly available with new instrumentation, is amenable to direct parameterization for one dimensional modeling using a water balance approach. An advantage of this approach over the commonly used Richards equation, is that the parameters exhibit relatively low spatial variability and are closely related to soil texture, perhaps the best known field soil characteristic. These aspects facilitate extrapolation across the landscape to the watershed scale. We show that, because storage terms are additive and all parts of the watershed are ultimately connected, the entire watershed can be regarded as a single store with an effective storage capacity and lower limit.

Seyfried, M. S.

2010-12-01

388

Natural Processes of Ground-Water and Surface-Water Interaction  

NSDL National Science Digital Library

This site explains the hydrologic cycle and interactions of ground water with surface water, streams, lakes, and wetlands. There are sections about chemical interactions of ground water and surface water; evolution of water chemistry in drainage basins; and interaction of ground water and surface water in different landscapes. Mountainous, riverine, coastal, glacial and dune, and karst terrain are examined.

Winter, Thomas; Harvey, Judson; Franke, O. L.; Alley, William

1998-01-01

389

Onset of perched water in a gradually layered soil: a laboratory experiment  

NASA Astrophysics Data System (ADS)

The genetic layering of the soil hydrological properties can significanly affect a number of processes as the onset of soil-slips, the runoff production and those related to the interaction between soil, water, plants and atmosphere. Therefore, with the aim of better understanding some aspects of these processes, we focused on the effect, during an imbibition process, of the decrease of the soil hydraulic conductivity at saturation Ks. A laboratory experiment was setup in order to observe the conditions and dynamics of the onset of a perched water in a gradually layered soil. A prismatic column was realised and filled with 9 different soil strata, each 0.1 m deep, whose grain-size distribution curve and porosity were such as to reproduce an exponential decay of Ks, on the basis of the application of a modified Kozeny-Carman relatioship. The so-rebuilt soil was artificially wetted by means of a rainfall simulator at a rate previously determined in order to maintain a constant water content on the surface for 9 hours. Istantaneous volumetric water content profiles were measured along the soil profile by means of 9 TDR probes and a multiplexer device. As a result of the experiment we observed and documented the formation of a water content peak at about 0.15 m depth, about 1.5 h after the beginning of the imbibition process. Then the peak emphasised and moved downward and a perched water formed at an intermediate height in the column, about 6 h after the beginning of the experiment. By this experiment we could then verify the formation of a water content peak, as predicted by a previously developed theoretical model and by a finite volume numerical simulation. The peak is then enveloped reaching the saturation as the wetting front moves downward. The perched water depth then rapidly increased upward while the wetting front slowly travelled downward. Before the transition toward saturation, the experiment supported the phoenomenological aspects enlightened by the analytical solution, although the adopted Gardner's constitutive laws tend to overestimate the unsaturated conductivity for most of the soils. A quantitative good agreement was observed between the experimental data and the numerical simulations.

Barontini, S.; Belluardo, G.; Bacchi, B.; Ranzi, R.

2009-04-01

390

Interactions between phosphate and water in solution  

PubMed Central

The Natural Bond Orbital (NBO) and Natural Energy Decomposition Analysis (NEDA) calculations are used to analyze the interaction between mono-methyl phosphate-ester (MMP) and its solvation environment in a combined quantum mechanical/molecular mechanical (QM/MM) framework. The solute-solvent configurations are generated using a specific parameterization of the self-consistent-charge density functional tight-binding (SCC-DFTB) model for the MMP and TIP3P for water. The NBO and NEDA calculations are done with several QM/MM partitioning schemes with the HF/6-31+G** as the QM level. Regardless of the size of the QM region, a notable amount of charge transfer is observed between MMP and the neighboring water molecules and the charge-transfer interactions are, in the NEDA framework, as important as the electric (electrostatic and polarization) components. This work illustrates that NBO based analyses are effective tools for probing intermolecular interactions in condensed phase systems.

Yang, Yang; Cui, Qiang

2008-01-01

391

Multivariate analyses of water chemistry: surface and ground water interactions.  

PubMed

Multivariate statistical methods (MSMs) applied to ground water chemistry provide valuable insight into the main hydrochemical species, hydrochemical processes, and water flowpaths important to ground water evolution. The MSMs of principal component factor analysis (FA) and k-means cluster analysis (CA) were sequentially applied to major ion chemistry from 211 different ground water-sampling locations in the Amargosa Desert. The FA reduces the number of variables describing the system and finds relationships between major ions. The CA of the reduced system produced objective hydrochemical facies, which are independent of, but in good agreement with, lithological data. The derived factors and hydrochemical facies are innovatively presented on biplots, revealing composition of hydrochemical processes and facies, and overlaid on a digital elevation model, displaying flowpaths and interactions with geologic and topographic features in the region. In particular, a distinct ground water chemical signature is observed beneath and surrounding the extended flowpath of Fortymile Wash, presenting some contradiction to contemporary water levels along with potential interaction with a fault line. The signature surrounding the ephemeral Fortymile Wash is believed to represent the relic of water that infiltrated during past pluvial periods when the amount of runoff in the wash was significantly larger than during the current drier period. This hypothesis and aforementioned analyses are supported by the examination of available chloride, oxygen-18, hydrogen-2, and carbon-14 data from the region. PMID:18194324

Woocay, Arturo; Walton, John

2008-01-09

392

Effects of Soil pH and Soil Water Content on Prosulfuron Dissipation  

Microsoft Academic Search

The sulfonylurea herbicide prosulfuron, 1-(4-methoxy-6-methyltriazin-2-yl)-3-(2-(3,3,3-trifluoropropyl)- phenylsulfonyl)urea, is used for the selective control of broadleaf weeds in corn, sorghum, and cereal grains. To investigate its fate in soils, this study examined the effects of soil pH and water content on the rates of dissipation processes and the products formed under aerobic conditions. Radiometry and chromatography analyses were used to quantify the

Ryan P. Hultgren; Robert J. M. Hudson; Gerald K. Sims

2002-01-01

393

Soil particle-size dependent partitioning behavior of pesticides within water–soil–cationic surfactant systems  

Microsoft Academic Search

Cationic surfactants have been proposed for enhanced sorption zones to contain hydrophobic organic compound (HOC) contamination. Benzalkonium chloride (BC), a cationic surfactant, was selected to study the particle-size dependent sorption behavior of the surfactant and its role in the immobilization of two hydrophobic pesticides (atrazine and diuron) within soil–water–surfactant systems for this application. Five different soils were considered in this

Peng Wang; Arturo A. Keller

2008-01-01

394

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

Microsoft Academic Search

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

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

2010-01-01

395

Soil and water conservation policies: Successes and failures  

SciTech Connect

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?

Napier, T.A. [ed.

2000-07-01

396

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

NASA Astrophysics Data System (ADS)

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

Gill, R. A.

2005-12-01

397

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

NASA Astrophysics Data System (ADS)

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

Iqbal, J.; Owens, P. R.

2005-12-01

398

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

Microsoft Academic Search

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

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

399

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...

400

SWRC fit - a nonlinear fitting program with a water retention curve for soils having unimodal and bimodal pore structure  

Microsoft Academic Search

The soil hydraulic parameters for analyzing soil water movement can be determined by fitting a soil water retention curve to a certain function, i.e., a soil hydraulic model. For this purpose, the program \\

K. Seki

2007-01-01

401

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

Technology Transfer Automated Retrieval System (TEKTRAN)

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

402

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

Code of Federal Regulations, 2010 CFR

...full extent and location of soils contaminated by the release and the...3) There is evidence that contaminated soils may be in contact with ground...on the potential effects of contaminated soil or ground water on nearby...

2009-07-01

403

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

Code of Federal Regulations, 2010 CFR

...full extent and location of soils contaminated by the release and the...3) There is evidence that contaminated soils may be in contact with ground...on the potential effects of contaminated soil or ground water on nearby...

2010-07-01

404

Proceedings of the Ground-Water Surface-Water Interactions Workshop.  

National Technical Information Service (NTIS)

Contents: Executive Summary; Presentation Abstracts (A Federal Statutory/Regulatory/Policy Perspective on Remedial Decision-making with Respect to Ground-Water/Surface-Water Interaction, Interaction of Ground Water and Surface Water, Hydrogeology and Bige...

2000-01-01

405

Impact of alfalfa on soil and water quality  

SciTech Connect

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.

Sharma, P.; Moncrief, J.; Gupta, S.

1997-10-30

406

Selenium status in soil, water and essential crops of Iran  

PubMed Central

Abstracts As a contributing factor to health, the trace element selenium (Se) is an essential nutrient of special interest for humans and all animals. It is estimated that 0.5 to 1 billion people worldwide suffer from Se deficiency. In spite of the important role of Se, its concentrations in soil, water and essential crops have not been studied in Iran. Therefore, the main aim of the current study was to determine the Se content of soil, water, and essential crops (rice in North, wheat in Center, date, and pistachio in South) of different regions of Iran. Sampling was performed in the North, South, and Central regions of Iran. In each selected area in the three regions, 17 samples of surface soil were collected; samples of water and essential crops were also collected at the same sampling points. Upon preliminary preparation of all samples, the Se concentrations were measured by ICP-OES Model Varian Vista-MPX. The amount of soil-Se was found to be in the range between 0.04 and 0.45 ppm in the studied areas; the Se content of soil in the central region of Iran was the highest compared to other regions (p<0.0001). The average Se concentration in irrigation water of different areas was less than 0.01 mg/L, and the mean concentrations of Se in the rice, wheat, date, and pistachio samples were 0.95, 0.74, 0.46, and 0.40 ppm, respectively. Although Se-soil and water-Se level in different regions were low, the typical levels of Se in the essential crops were relatively high.

2012-01-01

407

Soil water and nitrogen dynamics in dryland cropping systems of Washington State, USA  

Microsoft Academic Search

Understanding the fate of soil water and nitrogen (N) is essential for improving crop yield and optimizing the management of water and N in dryland cropping systems. The objective of this study was to evaluate how conventional (CT) and no-till (NT) cropping systems affect soil water and N dynamics. Soil water and N were monitored in 30cm increments to a

Juan P. Fuentes; Markus Flury; David R. Huggins; David F. Bezdicek

2003-01-01

408

Soil water hysteresis as a cause of delayed yield from unconfined aquifers  

Microsoft Academic Search

Hysteresis in the relation between soil water content and (negative) pressure head of the soil water produces a lag in the release of pore water from a rewetted soil when the pressure heads are lowered (made more negative). For an unconfined aquifer this means that the water table must drop some distance in response to pumping a well before pore

Herman Bouwer

1979-01-01

409

The influence of shade and clouds on soil water potential: The buffered behavior of hydraulic lift  

Microsoft Academic Search

In the sagebrush\\/bunchgrass steppe of the North American Great Basin soil water potential has been shown to exhibit diel fluctuations with water potential increasing during the night as a result of water loss from roots in relatively dry soil layers. We hypothesized that environmental conditions promoting low transpiration rates (shading, cloudiness) would cause a net increase in soil water potential

Kimberlyn Williams; Martyn M. Caldwell; James H. Richards

1993-01-01

410

Measurements of surface soil water heterogeneity with high spatial resolution using Ground Penetration Radar  

Microsoft Academic Search

The soil water content is an important variable in soil physics. At small scales, TDR-probes (Time Domain Reflectometry) can measure the water content and especially changes of water content with very high accuracy. But there is still a lack of methods suitable for areas and measurements of heterogeneity of soil water content. Using TDR, a high number of probes have

H. Stoffregen; J. Schmalholz; K. Täumer; U. Yaramanci

2003-01-01

411

Models of the water retention curve for soils w@h a fractal , pore size distribution  

Microsoft Academic Search

The relationship between water content and water potential for a soil is termed its water retention curve. This basic hydraulic property is closely related to the soil pore size distribution, for which it serves as a conventional method of measurement. In this paper a general model of the water retention curve is derived for soils whose pore size distribution is

Edith Perrier; Michel Rieu; Gliislain de Marsily

1996-01-01

412

Models of the water retention curve for soils with a fractal pore size distribution  

Microsoft Academic Search

The relationship between water content and water potential for a soil is termed its water retention curve. This basic hydraulic property is closely related to the soil pore size distribution, for which it serves as a conventional method of measurement. In this paper a general model of the water retention curve is derived for soils whose pore size distribution is

Edith Perrier; Michel Rieu; Garrison Sposito; Ghislain de Marsily

1996-01-01

413

Dynamics of the soil water and solute in the sodic saline soil in the Songnen Plain, China  

Microsoft Academic Search

According to the field experiment in the sodic saline soil region in the Songnen Plain, the dynamics of the soil water and\\u000a solute affected by the shallow groundwater were explored during the growing season in 2004. The results presented that, influenced\\u000a by the strongly evaporative demand, the soil water tended to transport to the upper soil layer with salt. The

Qiang Liu; Baoshan Cui; Zhifeng Yang

2009-01-01

414

SOURCES OF BASE CATIONS IN SOIL SOLIDS AND SOIL WATER: EXAMPLES FROM RED BROWN EARTHS OF SOUTH AUSTRALIA  

Microsoft Academic Search

In the study summarised here, Sr isotopic ratios of soil solid, soil carbonate, soil solute extracts, bedrock, silicate-organic dust, carbonate dust, dust extract, irrigation water, and grapes have been analysed in order to better understand the origin and pathways of Sr, and therefore Ca, and by extrapolation the other base cations in the soil-water-plant system. The solid, silicate mineral dominated

Erick A. Bestland; Graham P. Green; Kelly Rivett

415

Field-Scale Water Flow Simulations Using Ensembles of Pedotransfer Functions for Soil Water Retention  

Microsoft Academic Search

Using pedotransfer functions (PTF) to estimate soil hydraulic prop- erties may be necessary in soil water flow simulations for large-scale projects or in pilot studies. The accuracy of a PTF outside of its devel- opment dataset is generally unknown. The existence of multiple models that are developed and tested in one region, but may perform relatively poorly in other regions,

A. K. Guber; Ya. A. Pachepsky; M. Th. van Genuchten; W. J. Rawls; J. Simunek; D. Jacques; T. J. Nicholson; R. E. Cady

2006-01-01

416

Subsurface drip irrigation emitter spacing effects on soil water redistribution, corn yield, and water productivity  

Technology Transfer Automated Retrieval System (TEKTRAN)

Emitter spacings of 0.3 to 0.6 m are commonly used for subsurface drip irrigation (SDI) of corn on the deep, silt loam soils of the United States Great Plains. Subsurface drip irrigation emitter spacings of 0.3, 0.6, 0.9 and 1.2 m were examined for the resulting differences in soil water redistribut...

417

Migration through soil of organic solutes in an oil-shale process water  

Microsoft Academic Search

The migration through soil of organic solutes in an oil-shale process water (retort water) was studied by using soil columns and analyzing leachates for various organic constituents. Retort water extracted significant quantities of organic anions leached from ammonium-saturated-soil organic matter, and a distilled-water rinse, which followed retort-water leaching, released additional organic acids from the soil. After being corrected for organic

Jerry A. Leenheer; Harold A. Stuber

1981-01-01

418

[Soil water resource use limit in semi-arid loess hilly area].  

PubMed

Taking Caragana korshinskii as test object, and by using neutron probe, a long term observation was conducted on the soil water and plant growth during the process of vegetation restoration in semi-arid loess hilly area. The results showed that after seeding on waste land, the capability of plant community in conserving soil and water was promoted with time, with the depth of roots to absorb and use soil water increased and the soil water content reduced. Then, the dried soil layer appeared, and its deepness and thickness increased with increasing plant age. Therefore, the plant use of soil water had a limit, soil water resource use limit, i.e., the soil water storage when the deepness of dried soil layer was equal to the largest depth that rain could recharge. In the C. korshinskii woodland in semi-arid loess hilly area, the soil water resource use limit in 0-290 cm layer was 249.4 mm. When the soil water storage in woodland was close or equal to the soil water resource use limit, effective measures should be taken to decrease soil evapotranspiration or increase soil water supply to ensure the sustainable water use of plant roots. PMID:21442986

Guo, Zhong-sheng

2010-12-01

419

Soil water availability and microsite mediate fungal and bacterial phospholipid fatty acid biomarker abundances in Mojave Desert soils exposed to elevated atmospheric CO2  

NASA Astrophysics Data System (ADS)

Changes in the rates of nitrogen (N) cycling, microbial carbon (C) substrate use, and extracellular enzyme activities in a Mojave Desert ecosystem exposed to elevated atmospheric CO2 suggest shifts in the size and/or functional characteristics of microbial assemblages in two dominant soil microsites: plant interspaces and under the dominant shrub Larrea tridentata. We used ester-linked phospholipid fatty acid (PLFA) biomarkers as a proxy for microbial biomass to quantify spatial and temporal differences in soil microbial communities from February 2003 to May 2005. Further, we used the 13C signature of the fossil CO2 source for elevated CO2 plots to trace recent plant C inputs into soil organic matter (SOM) and broad microbial groups using ?13C (‰). Differences between individual ?13CPLFA and ?13CSOM for fungal biomarkers indicated active metabolism of newer C in elevated CO2 soils. Total PLFA-C was greater in shrub microsites compared to plant interspaces, and CO2 treatment differences within microsites increased under higher soil water availability. Total, fungal, and bacterial PLFA-C increased with decreasing soil volumetric water content (VWC) in both microsites, suggesting general adaptations to xeric desert conditions. Increases in fungal-to-bacterial PLFA-C ratio with decreasing VWC reflected functional group-specific responses to changing soil water availability. While temporal and spatial extremes in resource availability in desert ecosystems contribute to the difficulty in identifying common trends or mechanisms driving microbial responses in less extreme environments, we found that soil water availability and soil microsite interacted with elevated CO2 to shift fungal and bacterial biomarker abundances in Mojave Desert soils.

Jin, V. L.; Schaeffer, S. M.; Ziegler, S. E.; Evans, R. D.

2011-06-01

420

Effect of Clay Content and Soil-water Potential On Mobilization and Leaching of Colloids In Unsaturated Macroporous Soil  

NASA Astrophysics Data System (ADS)

The transport of strongly sorbed environmental contaminants may be enhanced due to sorption to mobile soil colloids. The most common source of mobile colloids in soil is the in-situ release of water-dispersible colloids (WDC), however experimental investigations of colloid mobilization in unsaturated macroporous soil are scarce. An understanding of the arrangement of colloids in aggregates, and the influence of clay on the development of the soil fabric and pore-size distributions is essential for the in- terpretation of colloid mobilization in soils. This emphasizes the important role of clay content, when evaluating the susceptibility of soils to release colloids and associated contaminants. This study was conducted to determine the effect of clay content and initial soil- water potential on colloid mobilization and leaching. Intact soil cores were sampled from an arable field at six locations along a naturally occurring texture gradient. Soil dispersibility was investigated using capillary saturation and drainage of field-moist packed aggregates. The amount of WDC in the soil was measured for each com- bination of clay content and initial soil-water potential (-2.5, -98 and -15530 hPa). Mobilization and leaching of colloids was investigated from unsaturated intact soil cores. The soils were irrigated at low intensity (1 mm/h), and effluent sampling was conducted at 5 cm tension. The results showed that colloid dispersion was significantly affected by both clay con- tent and initial soil-water potential. With a soil-water potential of -15530 hPa the col- loid release was generally low and no variation occurred between the soils. With in- creasing soil-water potential there was an increase in the amount of WDC for all soils. The increase in WDC was negatively correlated with clay content. The leaching of colloids from intact soil cores also decreased with increasing clay content at an ini- tial soil-water potential of -98 and -2.5 hPa, and no difference between clay contents was observed at -15530 hPa. Initial soil-water potential strongly affected the leach- ing of colloids from the soils with low clay content (<18 % clay), while no effect was observed at higher clay content. This may be explained by restricted contact area between the infiltrating water and the soil matrix as indicated by tracer breakthrough 1 experiments. 2

Kjaergaard, C.; de Jonge, L. W.; Moldrup, P.

421

An interactive virtual soil museum: a pilot project of the International Soil Reference and Information Centre with focus on arid soils  

Microsoft Academic Search

To increase the accessibility and use of the unique collection of world soils, together with its accompanying data and documentation, at the International Soil Reference and Information Centre (ISRIC) in Wageningen, the Netherlands, ISRIC, together with Wageningen Software Labs (W!SL) and Green Dino Virtual Realities, started a pilot project to develop an interactive Virtual Soil Museum5. The pilot project focuses

Otto Spaargaren; Jan Erik Wien; Onno Roosenschoon; Willem-Jan Jansen

2002-01-01

422

Long-term interaction of carbon cycling and geochemical weathering in soils: Does substrate quality matter over millennial timescales?  

NASA Astrophysics Data System (ADS)

Changes in the physical and chemical characteristics of soils control the form and extent of mechanisms of organic carbon stabilization. Evolution of soil geochemistry, and the resulting influence on soil carbon storage, is manifested over the timescales of soil development (millennial). However, these dynamics may still be relevant for understanding contemporary heterogeneity in soil carbon storage as well as the susceptibility of soil carbon stocks to disturbances. In particular, we hypothesize that functional soil type, or groupings of soils based on soil forming factors, can be used to predict the storage and stability of physically and chemically protected soil carbon. Implicit to our conceptual view of soil carbon cycling is the assumption that organic substrate quality is not a primary factor controlling carbon mean residence time over such long timescales. Rather, prevalence of physical and chemical mechanisms of carbon stabilization is the most germane predictor of long-term dynamics. To examine whether functional soil type can be used to predict contemporary soil carbon stability, especially with regard to the so called "slow" and "passive" carbon pools, we have quantified differences in mechanisms of soil carbon stabilization for soils of varying degree of pedogenic development from the Santa Cruz Marine Terrace Chronosequence, CA. Specifically, we have measured quantitative mineralogy, elemental chemistry, bulk soil carbon and radiocarbon and have implemented a sequential chemical extraction to approximate the fraction of organic carbon stored through interaction with various classes of minerals. Our results indicate that organic carbon cycling is coupled to both primary mineral dissolution and secondary mineral precipitation and also suggest a seasonal dynamic of mineral stabilization. In order to constrain long-term patterns in soil carbon storage and stability over changing soil conditions, we have integrated organic carbon reactions into a geochemical model (CrunchFlow), which has previously been used to simulate soil development at the Santa Cruz Marine Terraces. Our preliminary results suggest this modeling approach is a useful tool for understanding the dynamics of slowly cycling soil organic carbon. In addition, this work has also provided insights into the role of organic substrates as a control on mineral weathering and soil pore water chemistry.

Lawrence, C. R.; Maher, K.; Schulz, M. S.; White, A. F.; Harden, J. W.

2011-12-01

423

Influence of temperature on soil water content measured by ECH2O-TE sensors  

NASA Astrophysics Data System (ADS)

The aim of this study was to investigate the influence of temperature on water content value measured by ECH2O-TE sensors. The influence of temperature on measured soil water content values was clearly demonstrated. Soil water content values measured during the day apparently oscillated with oscillating soil temperatures. Average daily temperature and soil water