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1

Soil-water interaction: Lessons across scales  

Microsoft Academic Search

Understanding and modeling water flow behavior at the field scale is integral to various environmental and agricultural applications. Unfortunately, this understanding is challenged with preferential flows rendering the use of Darcian fluxes, developed at the laboratory scale, unable to describe the flow at the field. Preferential paths development in the field is the result of the complex interaction of multiple

Majdi Rafic Abou Najm

2009-01-01

2

Interaction of soil, water and TNT during degradation of TNT on contaminated soil using subcritical water.  

PubMed

Subcritical water was used at laboratory scale to reveal information with respect to the degradation mechanism of TNT on contaminated soil. Highly contaminated soil (12% TNT) was heated with water at four different temperatures, 150, 175, 200 and 225 degrees C and samples were obtained at appropriate time intervals. At the same time, similar experiments were performed with TNT spiked on to clean soil, sand and pure water in order to compare and eliminate various factors that may be present in the more complex contaminated soil system. Subcritical water was successful at remediating TNT-contaminated soil. TNT destruction percentages ranged between 98 and 100%. The aim of this work was to study the soil-water-contaminant interaction and determine the main physical parameters that affect TNT degradation. It was shown that the rate-limiting step of the process is the extraction/diffusion of TNT molecules from the soil core to the soil surface, where they degrade. Additionally, it was determined that the soil matrix also catalyses degradation to a lesser extent. Autocatalytic effects were not clearly observed. PMID:18384944

Kalderis, Dimitrios; Hawthorne, Steven B; Clifford, Anthony A; Gidarakos, Evangelos

2008-11-30

3

Estimating respiration of roots in soil: Interactions with soil CO 2 , soil temperature and soil water content  

Microsoft Academic Search

Little information is available on the variability of the dynamics of the actual and observed root respiration rate in relation to abiotic factors. In this study, we describe I) interactions between soil CO2 concentration, temperature, soil water content and root respiration, and II) the effect of short-term fluctuations of these three environmental factors on the relation between actual and observed

Tjeerd J. Bouma; Kai L. Nielsen; David M. Eissenstat; Jonathan P. Lynch

1997-01-01

4

A model for soil-vegetation-atmosphere interactions in water-limited ecosystems  

E-print Network

it reaches a wet and cool state when starting from higher initial values of soil moisture and of vegetationA model for soil-vegetation-atmosphere interactions in water-limited ecosystems M. Baudena,1,2 F. D; published 20 December 2008. [1] We study the interaction between atmosphere, soil moisture, and vegetation

D'Andrea, Fabio

5

Numerical simulation of soil–water interaction using smoothed particle hydrodynamics (SPH) method  

Microsoft Academic Search

An application of smoothed particle hydrodynamics (SPH) to simulation of soil–water interaction is presented. In this calculation, water is modeled as a viscous fluid with week compressibility and soil is modeled as an elastic–perfectly plastic material. The Mohr–Coulomb failure criterion is applied to describe the stress states of soil in the plastic flow regime. Dry soil is modeled by one-phase

Ha H. Bui; K. Sako; R. Fukagawa

2007-01-01

6

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

SciTech Connect

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

Waugh, W.J.

1989-05-01

7

Digital Soil Mapping: Interactions with  

E-print Network

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

Grunwald, Sabine

8

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

NASA Astrophysics Data System (ADS)

In isotope-enabled hydrology, soil and vadose zone sediments have been generally considered to be isotopically inert with respect to the water they host. This is inconsistent with knowledge that clay particles possessing an electronegative surface charge and resulting cation exchange capacity (CEC) interact with a wide range of solutes which, in the absence of clays, have been shown to exhibit ?18O isotope effects that vary in relation to the ionic strength of the solutions. To investigate the isotope effects caused by high CEC clays in mineral-water systems, we created a series of monominerallic-water mixtures at gravimetric water contents ranging from 5% to 32%, consisting of pure deionized water of known isotopic composition with homoionic (Mg, Ca, Na, K) montmorillonite. Similar mixtures were also created with quartz to determine the isotope effect of non-, or very minimally-, charged mineral surfaces. The ?18O value of the water in these monominerallic soil analogs was then measured by isotope ratio mass spectrometry (IRMS) after direct headspace CO2 equilibration. Mg- and Ca-exchanged homoionic montmorillonite depleted measured ?18O values up to 1.55‰ relative to pure water at 5% water content, declining to 0.49‰ depletion at 30% water content. K-montmorillonite enriched measured ?18O values up to 0.86‰ at 5% water content, declining to 0.11‰ enrichment at 30% water. Na-montmorillonite produces no measureable isotope effect. The isotope effects observed in these experiments may be present in natural, high-clay soils and sediments. These findings have relevance to the interpretation of results of direct CO2-water equilibration approaches to the measurement of the ?18O value of soil water. The adsorbed cation isotope effect may bear consideration in studies of pedogenic carbonate, plant-soil water use and soil-atmosphere interaction. Finally, the observed isotope effects may prove useful as molecular scale probes of the nature of mineral-water interactions.

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

2014-07-01

9

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

10

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

E-print Network

Oxygen isotope fractionation effects in soil water via interaction with cations (Mg, Ca, K, Na. Goldsmith c , Todd Dawson d , Ronald Amundson a a Department of Environmental Science, Policy and Management, Berkeley, United States a r t i c l e i n f o Article history: Received 5 February 2014 Received in revised

Goldsmith, Greg

11

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

PubMed Central

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

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

2014-01-01

12

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

Microsoft Academic Search

The relationship between vegetation and soil water was studied on the Syncrude South West Sand Storage facility in the Athabasca Oil Sands region of Alberta, Canada. Soil water and relevant soil chemical and physical properties were measured at the soil surface, as well as above and below the reclamation soil and tailings sand interface, in areas of low and high

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

2011-01-01

13

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

EPA Science Inventory

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

14

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

15

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

NASA Astrophysics Data System (ADS)

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

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

2014-11-01

16

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

2006-03-28

17

Alkali Soils, Irrigation Waters.  

E-print Network

, or it may be carried away to accumulate in another field. JVhen water comes in contact with the soil, it dissolves the soluble constituents as far as it penetrates. If afterwards it rises and evap- orates, it leaves there all the alkali which it held... Vetch .................................. The Bureau cf Soils of the United States Department of Agriculture divides soils into six grades, according to their average of soluble calts to a depth of six feet. - Percentage Black of Total Salts Alkali...

Fraps, G. S. (George Stronach)

1910-01-01

18

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

EPA Science Inventory

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

19

The interaction of water vapor with a lunar soil, a compacted soil, and a cinder-like rock fragment  

NASA Technical Reports Server (NTRS)

A volumetric adsorption system incorporating a pressure gauge was employed to determine nitrogen adsorption and evaluate surface areas. The water adsorption of the lunar samples was measured with the aid of a gravimetric adsorption system including a microbalance. The results obtained in the investigation for the three samples are discussed in detail, giving attention to aspects of dehydroxylation and rehydroxylation.

Cadenhead, D. A.; Stetter, J. R.

1974-01-01

20

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

E-print Network

Indicators of nitrate in wetland surface and soil-waters: interactions of vegetation and environmental factors 663 Hydrology and Earth System Sciences, 8(4), 663672 (2004) © EGU Indicators of nitrate, and hence the sampling period, was MayAugust during both years. Seasonal mean concentrations of nitrate (NO3

Paris-Sud XI, Université de

21

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

Microsoft Academic Search

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

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

2003-01-01

22

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

NASA Astrophysics Data System (ADS)

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

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

2004-12-01

23

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

E-print Network

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

Ahmed, Ashour; Kühn, Oliver

2013-01-01

24

Nitrogen and carbon interactions between boreal soils and lakes  

Microsoft Academic Search

In this study, we used a large data set on nitrogen (N) and carbon (C) from Swedish boreal soils and lake waters to investigate N and C interactions between soils and lake waters. To link thousands of soils sites with hundreds of lake sites distributed all over Sweden, we gridded the data and found a significant relation between gridded C:N

Maria I. Khalili; Johan Temnerud; Mats Fröberg; Erik Karltun; Gesa A. Weyhenmeyer

2010-01-01

25

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

26

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.

27

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

28

Soil and Human Interactions in Maya Wetlands  

NASA Astrophysics Data System (ADS)

Since the early 1990s, we have studied Maya interaction with soils in Mexico, Belize, Guatemala, and elsewhere. We studied upland and lowland soils, but here we focus on seasonal or 'Bajo' wetlands and perennial wetlands for different reasons. Around the bajos, the ancient Maya focused on intensive agriculture and habitation despite the difficulties their Vertisol soils posed. For the perennial wetlands, small populations spread diffusely through Mollisol and Histisol landscapes with large scale, intensive agro-ecosystems. These wetlands also represent important repositories for both environmental change and how humans responded in situ to environmental changes. Work analyzing bajo soils has recorded significant diversity but the soil and sediment record shows two main eras of soil instability: the Pleistocene-Holocene transition as rainfall fluctuated and increased and tropical forest pulsed through the region, and the Maya Preclassic to Classic 3000 to 1000 BP as deforestation, land use intensity, and drying waxed and waned. The ancient Maya adapted their bajo soil ecosystems successfully through agro-engineering but they also withdrew in many important places in the Late Preclassic about 2000 BP and Terminal Classic about 1200 BP. We continue to study and debate the importance of perennial wetland agro-ecosystems, but it is now clear that Maya interaction with these soil landscapes was significant and multifaceted. Based on soil excavation and coring with a broad toolkit of soil stratigraphy, chemistry, and paleoecology from 2001 to 2013, our results show the ancient Maya interacted with their wetland soils to maintain cropland for maize, tree crops, arrow root, and cassava against relative sea level rise, increased flooding, and aggradation by gypsum precipitation and sedimentation. We have studied these interactions across an area of 2000 km2 in Northern Belize to understand how Maya response varied and how these soil environments varied over time and distance. Most areas dealt with water table rise and gypsum aggradation from extremely sulfur- and calcium-rich water sources. Thus far we have evidence for Archaic to Classic aggradation (5000 BP to the present) and Classic period fields and canals as mostly piecemeal attempts by the Maya to adapt to these and other environmental changes. Wetland fields were mainly Classic period systems (1500 to 1000 BP) but varied from long- to short-lived. We found one example of a very Late/Terminal Classic (c. 1200 BP), preplanned reclamation project on a floodplain. One system had some reoccupation in the Postclassic about 800 BP. These findings and a recent discovery in Campeche, MX display the burgeoning evidence for intricate Maya connections with tropical wetland soils.

Beach, Timothy; Luzzadder-Beach, Sheryl

2013-04-01

29

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

30

Interaction of Herbicides and Soil Microorganisms.  

National Technical Information Service (NTIS)

The introduction of microorganisms with specific degradative capacities into the soil was shown to be a possible means of ridding the soil of contaminating chemicals. An investigation of the interactions of soil microorganisms and several groups of herbic...

1971-01-01

31

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

Microsoft Academic Search

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

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

2009-01-01

32

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

33

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

34

Soil Quality Information Sheet Rangeland Soil Quality--Water Erosion  

E-print Network

Soil Quality Information Sheet Rangeland Soil Quality--Water Erosion USDA, Natural Resources Conservation Service May 2001 Rangeland Sheet 9 What is water erosion? Water erosion is the detachment and removal of soil material by water. The process may be natural or accelerated by human activity. The rate

35

SOIL & WATER MANAGEMENT & CONSERVATION Landscape and Conservation Management Effects on Hydraulic Properties of a Claypan Soil Toposequence  

Microsoft Academic Search

Information on the effects of landscape and its interaction with management on soil hydraulic properties is scarce. Our objective was to investigate the effects and interactions of landscape position and conservation management systems (e.g., reduced tillage or permanent grass) on soil bulk density, saturated hydraulic conductivity (Ksat), soil water retention, and pore-size distributions for claypan soils in central Missouri. Landscape

S. H. Anderson; E. J. Sadler; K. A. Sudduth

36

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

E-print Network

on soil car- bon storage, whereas fertilization and nitrogen-fixing vegeta- tion increase overall soilSummary Soil respiration is controlled by soil temperature, soil water, fine roots, microbial activity, and soil physical and chemical properties. Forest thinning changes soil temperature, soil water

Cohen, Ronald C.

37

Soil and Water Conservation Spring 2014  

E-print Network

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

Ma, Lena

38

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

39

Soil and Water Conservation Spring 2014  

E-print Network

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

Ma, Lena

40

Field Devices for Monitoring Soil Water Content  

E-print Network

. Professor, Soil and Water Science Dept. Univ. of Florida for The Irrigation Water Management Program Team content in the soil can be directly determined using the difference in weight before and after drying content (GWC, g g-1 ) as weight of water over weight of dry soil, i.e. the ratio of the mass of water

41

Poverty, Resource Scarcity and Incentives for Soil and Water Conservation: Analysis of Interactions with a Bio-economic Model  

Microsoft Academic Search

The paper examines the interlinkages between population pressure and poverty, possible impacts on household welfare and land management, and the consequent pathways of development in a low potential rural economy. A dynamic non-separable bio-economic model, calibrated using data from the Ethiopian highlands, is used to trace key relationships between population pressure, poverty and soil fertility management in smallholder agriculture characterized

Bekele A. Shiferaw; Stein Holden

2003-01-01

42

CROP & SOIL SCIENCES Water Policy and Management  

E-print Network

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

Arnold, Jonathan

43

5, 723748, 2008 Soil water dynamics  

E-print Network

in the soil water balance dynamics. 1 Introduction15 Dynamics of soil moisture in time and space is governedHESSD 5, 723­748, 2008 Soil water dynamics within a river basin S. Manfreda and M. Fiorentino Title A stochastic approach for the description of the water balance dynamics in a river basin S. Manfreda and M

Boyer, Edmond

44

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

NASA Astrophysics Data System (ADS)

High-resolution soil property maps are one major prerequisite for the specific protection of soil functions and restoration of degraded soils as well as sustainable land use, water and environmental management. To generate such maps the combination of digital soil mapping approaches and remote as well as proximal soil sensing techniques is most promising. However, a feasible and reliable combination of these technologies for the investigation of large areas (e.g. catchments and landscapes) and the assessment of soil degradation threats is missing. Furthermore, there is insufficient dissemination of knowledge on digital soil mapping and proximal soil sensing in the scientific community, to relevant authorities as well as prospective users. As one consequence there is inadequate standardization of techniques. At the poster we present the EU collaborative project iSOIL within the 7th framework program of the European Commission. iSOIL focuses on improving fast and reliable mapping methods of soil properties, soil functions and soil degradation risks. This requires the improvement and integration of advanced soil sampling approaches, geophysical and spectroscopic measuring techniques, as well as pedometric and pedophysical approaches. The focus of the iSOIL project is to develop new and to improve existing strategies and innovative methods for generating accurate, high resolution soil property maps. At the same time the developments will reduce costs compared to traditional soil mapping. ISOIL tackles the challenges by the integration of three major components: (i)high resolution, non-destructive geophysical (e.g. Electromagnetic Induction EMI; Ground Penetrating Radar, GPR; magnetics, seismics) and spectroscopic (e.g., Near Surface Infrared, NIR) methods, (ii)Concepts of Digital Soil Mapping (DSM) and pedometrics as well as (iii)optimized soil sampling with respect to profound soil scientific and (geo)statistical strategies. A special focus of iSOIL lies on the sustainable dissemination of technologies and concepts developed in the projects through workshops for stakeholders and the publication of a handbook "Methods and Technologies for Mapping of Soil Properties, Function and Threat Risks". Besides, the CEN Workshop offers a new mechanism and approach to standardization. During the project we decided that the topic of the CEN Workshop should focus on a voluntary standardization of electromagnetic induction measurement to ensure that results can be evaluated and processed under uniform circumstances and can be comparable. At the poster we will also present the idea and the objectives of our CEN Workshop "Best Practice Approach for electromagnetic induction measurements of the near surface"and invite every interested person to participate.

Dietrich, Peter; Werban, Ulrike; Sauer, Uta

2010-05-01

45

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

E-print Network

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

Southern California, University of

46

Thresholds of biotic/abiotic interactions in soil carbon storage  

NASA Astrophysics Data System (ADS)

Thresholds of biotic/abiotic interactions during soil development are linked to the spatial proximity of biological inputs and chemical weathering. On stable landforms, the downward transport of water and weathering products through soils give rise to vertical biogeochemical and mineralogical gradients, and the shape of these gradients change through time as the soil development proceeds. The weathering-zone, where rates of mineral dissolution and precipitation are greatest, typically migrates downward through the soil profile with increased duration of soil development. As the weathering-zone moves deeper in the soil profile, away from the zone of maximum biological inputs, abiotic/biotic interactions controlling the formation of secondary minerals and the stabilization of carbon may shift toward new stable states. Here we explore the relationship between soil development and organic carbon storage and stability and evaluate the existence of threshold behavior in soil carbon sequestration. We compare depth profiles of soil mineralogy, geochemistry and surface area with carbon stocks and radiocarbon content for a soil chronosequence spanning 1200 kyr. Results show a strong inverse correlation between radiocarbon content and mineral surface area and indicate the possible existence of a threshold behavior in soil carbon stabilization. Increases in surface area appear to arise from increasing amounts of secondary clay precipitation. Such thresholds have been previously observed in systems where short-range order minerals are prevalent but we demonstrate they may also be important in other soils. We use the reactive transport model CrunchFlow to evaluate the relationship of organic inputs and chemical weathering and to explore the influence of climate (specifically water flux) on soil threshold behavior.

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

2013-12-01

47

Transpiration as a Function of Soil Temperature and Soil Water Stress  

PubMed Central

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

Cox, L. M.; Boersma, L.

1967-01-01

48

Macroscopic modeling of plant water uptake: soil and root resistances  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

49

Stochastic analysis of soil-structure interaction  

E-print Network

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

Chan, Charles Cheuk Lap

2012-06-07

50

SSI (soil-structure interactions) and structural benchmarks  

SciTech Connect

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

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

1986-01-01

51

Irrigation Monitoring with Soil Water Sensors  

E-print Network

and need to be irrigated more frequently than clay or loam soils. Management allowable depletion (MAD). This is the point below which the soil available water should not be depleted to avoid excessive water stress and, therefore, reduction... in production. The volume of water between the MAD point and field capacity should be the irrigation depth. The volume of water below this limit is what re- mains in the soil. The management allowable depletion (or allowable deficit) will depend on the plant...

Enciso, Juan; Porter, Dana; Peries, Xavier

2007-01-19

52

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

53

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

54

Understanding Dynamic Soil Water Repellency and its Hydrological Implications  

NASA Astrophysics Data System (ADS)

The adverse effects of water repellent soils on vadose zone hydrology are being increasingly identified worldwide in both rural and urban landscapes. Among the affected landscapes are agricultural fields, forests, effluent application sites, golf greens, wetlands, and wildfire sites. In spite of cross-discipline research efforts put forth in recent years, understanding of fundamental parameters controlling soil water behaviour in these systems is lacking. This is due, in part, to inherent complexities of water repellent soil systems and logistical shortcomings of methods commonly used by researchers in-situ and in the lab. As a result, modeling flow in these systems has further proven to be a difficult task. The objectives of our study were 1) to systematically measure and quantify water infiltration and distribution in dynamic water repellent systems and 2) to identify fundamental hydraulic behaviours that lead to the expression of changes in soil water repellency. To achieve this, we combined techniques to elucidate soil- water interactions at a post-wildfire site. Field tests and subsequent lab work reveal essential hydrological information on fire-affected water repellent soils at variable scales and under different burn conditions. Through the use of traditional and newer techniques, our work shows unique and previously unreported behaviour of soil water in these systems. We also address limitations of current field methods used to study repellency and associated infiltration behaviours.

Beatty, S. M.; Smith, J. E.

2009-05-01

55

Outcomes of fungal interactions are determined by soil invertebrate grazers  

E-print Network

soil fauna may influence fungal community composition and diversity. Factors affecting soil composition in litter resources and soil (Boddy 2000). Species-specific fungal enzyme productionLETTER Outcomes of fungal interactions are determined by soil invertebrate grazers Thomas W

Bruns, Tom

56

IRRIGATION OPTIMIZATION BY MODELING OF PLANT-SOIL INTERACTION  

E-print Network

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

Boyer, Edmond

57

A minimalist probabilistic description of root zone soil water  

USGS Publications Warehouse

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

Milly, P.C.D.

2001-01-01

58

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

NASA Astrophysics Data System (ADS)

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

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

2012-05-01

59

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

SciTech Connect

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.

McLaughlin, Samuel B. [Oak Ridge National Laboratory (Retired); Wullschleger, Stan D [ORNL; Sun, G. [USDA Forest Service; Nosal, M. [University of Calgary, ALberta, Canada

2007-01-01

60

Pesticide interactions with soils affected by olive oil mill wastewater  

NASA Astrophysics Data System (ADS)

Soil pesticide sorption is well known to affect the fate of pesticides, their bioavailability and the potential to contaminate air and water. Soil - pesticide interactions may be strongly influenced by soil organic matter (SOM) and organic matter (OM)-rich soil amendments. One special OM source in soils is related to olive oil production residues that may include both solid and liquid wastes. In the Mediterranean area, the olive oil production is considered as an important field in the agricultural sector. Due to the significant rise in olive oil production, the amount of wastes is growing respectively. Olive oil mill waste water (OMWW) is the liquid byproduct in the so-called "three phase" technological process. Features of OMWW include the high content of fatty aliphatic components and polyphenols and their often-considered toxicity. One way of OMWW disposal is the land spreading, e.g., in olive orchards. The land application of OMWW (either controlled or not) is supposed to affect the multiple soil properties, including hydrophobicity and the potential of soils to interact with pesticides. Therefore, there is both basic and applied interest in elucidating the interactions between organic compounds and soils affected by OMWW. However, little is known about the impact of OMWW - soil interactions on sorption of organic compounds, and specifically, on sorption of agrochemicals. This paper reports an experimental study of sorption interactions of a series of organic compounds including widely used herbicides such as diuron and simazine, in a range of soils that were affected by OMWW (i) historically or (ii) in the controlled land disposal experiments. It is demonstrated that there is a distinct increase in apparent sorption of organic chemicals in soils affected by OMWW. In selected systems, this increase may be explained by increase in SOM content. However, the SOM quality places a role: the rise in organic compound - soil interactions may both exceed the SOM content increase and be less than that. Sorption interactions of herbicides with soils demonstrate a strong hysteresis (which is not expected to be related to a biodegradation). The data suggests that the OMWW - soil interaction seems to change the shape of the apparent sorption isotherms of organic sorbates, and, possibly, their sorption mechanisms: from a Langmuir-like sorption isotherm (describing the adsorptive interactions with a saturation of sorption sites) in the native soils to the sigmoidal or linear isotherms (expected for a partitioning into the bulk OM phases and their swelling) in the OMWW-amended soils. These results may have a significant impact on multiple agricultural and hydrological aspects, e.g., such as the application rate of herbicides in the field, and their possible release and the long term effect on groundwater. The authors acknowledge the support from the OLIVEOIL project (SCHA849/13) funded by DFG.

Keren, Yonatan; Bukhanovsky, Nadezhda; Borisover, Mikhail

2013-04-01

61

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

62

Soil water hydrology: simulation for water balance computations  

Microsoft Academic Search

Soil moisture occurs as the result of the climatic, crop, and soil processes which impact water on a vegetated landscape. This complex and highly dynamic water supply provides the water upon which the vast majority of the world food supply depends. Most importantly, it is as variable within and between years and location as the variables which determine its occurrence.

KEITH E. SAXTON

1983-01-01

63

7 Phosphorus Modeling in Soil and Water  

E-print Network

163 7 Phosphorus Modeling in Soil and Water Assessment Tool (SWAT) Model Indrajeet Chaubey, Decomposition, and Immobilization..................... 170 7.2.3 Inorganic Phosphorus Sorption............................................................................................................. 185 7.1 SWAT MODEL BACKGROUND The Soil and Water Assessment Tool (SWAT) model was developed by the U

64

America's Soil and Water: Condition and Trends.  

ERIC Educational Resources Information Center

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

1981

65

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

E-print Network

in preserving soil moisture over long periods needs further investigation. Diurnal Changes in Soil Moisture - Soil water content in the upper 30 cm (12 inches) of the soil apparently changes diurnally with major diurnal changes in soil temperature. Such changes...

Wendt, C. W.

66

Numerical Analysis of Transport of Interacting Solutes in a Three-Dimensional Unsaturated Heterogeneous Soil  

Microsoft Academic Search

dence of the hydraulic conductivity and water retentivity on solute heterogeneous soils. concentrations. Numerical simulations of flow and transport of both The aforementioned studies focused on transport of a tracer and mixed Na-Ca solutes were employed to analyze long-term single noninteracting solute. In reality, however, mixed- effects of the interactions between the soil solution and the soil matrix salt solutions,

David Russo; Jacob Zaidel; Asher Laufer

2004-01-01

67

Water and Energy Interactions  

E-print Network

capacitive deionization (50% of brackish water treatment energy) and (b) advanced RO or membranecapacitive deionization with high- surface-area electrodes to treat brackish water; and (c) employing membrane

McMahon, James E.

2013-01-01

68

Mathematical models of plant-soil interaction.  

PubMed

In this paper, we set out to illustrate and discuss how mathematical modelling could and should be applied to aid our understanding of plants and, in particular, plant-soil interactions. Our aim is to persuade members of both the biological and mathematical communities of the need to collaborate in developing quantitative mechanistic models. We believe that such models will lead to a more profound understanding of the fundamental science of plants and may help us with managing real-world problems such as food shortages and global warming. We start the paper by reviewing mathematical models that have been developed to describe nutrient and water uptake by a single root. We discuss briefly the mathematical techniques involved in analysing these models and present some of the analytical results of these models. Then, we describe how the information gained from the single-root scale models can be translated to root system and field scales. We discuss the advantages and disadvantages of different mathematical approaches and make a case that mechanistic rather than phenomenological models will in the end be more trustworthy. We also discuss the need for a considerable amount of effort on the fundamental mathematics of upscaling and homogenization methods specialized for branched networks such as roots. Finally, we discuss different future avenues of research and how we believe these should be approached so that in the long term it will be possible to develop a valid, quantitative whole-plant model. PMID:18818147

Roose, Tiina; Schnepf, Andrea

2008-12-28

69

SW—Soil and Water  

Microsoft Academic Search

Standard triaxial compression tests were carried out on an agricultural sandy loam soil to assess the effect of soil dry bulk density and moisture content on soil mechanical properties, namely, cohesion, internal friction angle, Young's modulus of elasticity and Poisson's ratio. Regression analyses were performed to establish mathematical relationships for simulating the variation in these mechanical properties as a function

Abdul Mounem Mouazen; Herman Ramon; Josse De Baerdemaeker

2002-01-01

70

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

71

Estimating Soil Water Retention and Unsaturated Soil Hydraulic Conductivity of Aggregated Soils Using the Additivity Model  

NASA Astrophysics Data System (ADS)

Soil-water potential and hydraulic conductivity relationships with soil water content are needed for many plant and soil-water studies. Conventional soil pore space model lying in the base of "one pore region - one continuum", described by pair of water retention and unsaturated soil hydraulic functions, often oversimplifies representation of variably saturated porous media as a homogeneous textural pore space. Soil structure has a major effect on soils ability to retain and to conduct water. This is especially right for aggregated soils in which pore space consists of interconnected intra- and inter-aggregate pores with distinct hydraulic properties. When a proportion of the inter-aggregate pore space is significant, in many cases the conventional description of water flow provides results that don't much an experimental data. In case of developed "aggregated soil" based on the concept "two pore regions - two continuums" soil pore space is described by two pair of both unsaturated soil hydraulic functions. A special model to estimate these functions is developed based on input data of bulk and aggregate density, structural and textural component distributions. This model was tested with experimental data measured of water retention and hydraulic conductivity of soil cores consisting of aggregates with sizes within narrow ranges. Cores were fabricated from separated individual aggregate fractions of Halpic Chernozem, Podzoluvisol, Halpic Kastanozem soils and artificially prepared aggregates. The obtained results demonstrate the sensitivity of the "additivity" model to estimate both unsaturated soil hydraulic functions for each pore regions. Keywords: aggregated soil, soil structure, soil water retention, additivity model

Zeiliger, A.; Ermolaeva, O.

2009-04-01

72

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

73

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

74

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

75

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

76

The effect of soil water upon soil albedo  

E-print Network

potential and albedo is more general than the rela- tion between water content and albedo, as can be deduced fran the mechanism proposed by Dolgov and Vinogradova (1973). They attribute the decrease in albedo to increased reflection of light into the soil..., when water films become thicker and the number of intersecting water-air interfaces of the water continuum increases. As water potential is closely related to the thickness of the water films, and the filling or draining of pores of a particular size...

Graser, Elizabeth Annette

2012-06-07

77

Modeling, estimation, and control of robot-soil interactions  

E-print Network

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

Hong, Won, 1971-

2001-01-01

78

Water Drainage from Unsaturated Soils in a Centrifuge Permeameter  

NASA Astrophysics Data System (ADS)

This study involves an analysis of water drainage from an initially saturated silt layer in a centrifuge permeameter to evaluate the hydraulic properties of the soil layer in unsaturated conditions up to the point where the water phase becomes discontinuous. These properties include the soil water retention curve (SWRC) and the hydraulic conductivity function (HCF). The hydraulic properties of unsaturated silt are used in soil-atmosphere interaction models that take into account the role of infiltration and evaporation of water from soils due to atmospheric interaction. These models are often applied in slope stability analyses, landfill cover design, aquifer recharge analyses, and agricultural engineering. The hydraulic properties are also relevant to recent research concerning geothermal heating and cooling, as they can be used to assess the insulating effects of soil around underground heat exchangers. This study employs a high-speed geotechnical centrifuge to increase the self-weight of a compacted silt specimen atop a filter plate. Under a centrifuge acceleration of N times earth's gravity, the concept of geometric similitude indicates that the water flow process in a small-scale soil layer will be similar to those in a soil layer in the field that is N times thicker. The centrifuge acceleration also results in an increase in the hydraulic gradient across the silt specimen, which causes water to flow out of the pores following Darcy's law. The drainage test was performed until the rate of liquid water flow out of the soil layer slowed to a negligible level, which corresponds to the transition point at which further water flow can only occur due to water vapor diffusion following Fick's law. The data from the drainage test in the centrifuge were used to determine the SWRC and HCF at different depths in the silt specimen, which compared well with similar properties defined using other laboratory tests. The transition point at which liquid water flow stopped (and Darcy's law is no longer valid) was at a relatively high degree of saturation of 0.8. This finding is important as many water flow analyses in the literature assume that Darcy's law is valid over a much wider range of degrees of saturation, an error that potentially may lead to overestimates of water flow in unsaturated soil layers.

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

2013-12-01

79

Water retention, hydraulic conductivity of hydrophilic polymers in sandy soil as affected by temperature and water quality  

NASA Astrophysics Data System (ADS)

SummaryHydrophilic polymers can swell by absorbing huge volumes of water or aqueous solutions. This property has led to many practical applications of these new materials, particularly in arid regions for improving water retention in sandy soils and the water supply to plants grown on them. The effects of two hydrophilic polymers, carboxymethylcellulose (RF) and isopropyl acrylamide (BF) on the water holding capacity and saturated hydraulic conductivity ( KS) of a sandy soil at varying soil temperature and water quality were evaluated. The RF was less efficient in absorbing water than BF, but the efficiency of BF in retaining water was negatively affected by its thermo-sensitivity and the quality of water. The temperature dependence of the water absorption was not clear for the soils treated with RF, whereas, the efficiency of BF treatment in absorbing water decreased significantly ( P < 0.05) with increasing soil temperature. The dependence of the KS on soil temperature differed with the type of hydrophilic polymer used. The KS of the control soil remained nearly constant as the soil temperature increased. The KS of the BF treated soil increased significantly ( P < 0.05) and linearly with increasing soil temperature, while that of soil treated with RF showed a quadratic response. The soil-absorbent mixtures exhibited different water retention characteristics under different soil temperature conditions. The increase in soil temperature did not affect the water retention characteristics curve of the control. The effect of soil temperature on the water potential curve of the soil treated with RF was not clear particularly when the temperature increased from 25 to 35 °C. The water potential curve for soil-BF mixtures showed that the water content value at field capacity shifted from 0.21 to 0.10 cm 3 cm -3 for 0.1% and from 0.27 to 0.12 cm 3 cm -3 for 0.2%, as the soil temperature increased from 15 to 35 °C. This implies that the soil-BF absorbent mixtures would release some moisture as the soil temperature would increase from 15 to 35 °C, and this water could be lost by percolation or taken up by plant. It was found that available water content increased up to four times with RF as compared to control soil whereas it increased up to five times with BF treatment. At high temperature, the difference was much reduced except for RF at 0.2%. This understanding of the characteristics of the absorbents and the interactions among absorbents, soil, and temperature would be of help in water management in sandy soil.

Andry, H.; Yamamoto, T.; Irie, T.; Moritani, S.; Inoue, M.; Fujiyama, H.

2009-06-01

80

Spatial and Statistical Similarities of Local Soil Water Fluxes  

Microsoft Academic Search

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

Bing Cheng Si

2002-01-01

81

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

82

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

E-print Network

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

MacDonald, Lee

83

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

NASA Astrophysics Data System (ADS)

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

Gonzales, Christopher; Baumgartl, Thomas; Scheuermann, Alexander

2014-05-01

84

Fall Contour Ripping Increases Water Infiltration into Frozen Soil  

Microsoft Academic Search

Crop residue management to trap snow and soil management to improve water infiltration into frozen soil might reduce spring runoff and increase soil water storage. We hypothesized that soil macropores created by tillage would improve water infiltration when the soil was frozen. This hypothesis was tested by ripping a Dooley sandy loam (fine-loamy, mixed Typic Argiboroll) in the fall of

J. L. Pikul; J. K. Aase

1998-01-01

85

EFFECT OF SOIL WATER AND NUTRIENTS ON PRODUCTIVITY OF KENTUCKY BLUEGRASS SYSTEM IN ACIDIC SOILS  

Microsoft Academic Search

The grasslands of the Appalachian region spread over undulating terrain with high annual precipitation rate which causes a large variation in soil and nutrient factors like water potential (WP), pH, nitrogen (N) and phosphorus (P) levels. There is a need to understand these factors and their interactive effects to design precise agronomic practices for acidic grasslands to maximize production. A

Rajesh Chintala; Louis M. McDonald; William B. Bryan

2012-01-01

86

Energy and Water Fluxes at the Soil Atmosphere Interface of Water Repellent Soils  

NASA Astrophysics Data System (ADS)

Water transport processes in water repellent soils are different from transport processes in non repellent soils. These differences have been and are studied extensively. Little is known about the effects of water repellency on energy exchange between soil and atmosphere. Changes of the energy balance are mainly caused by changes of water content distribution in the topsoil. Our working hypothesis is that water repellency will significantly affect the soil-atmosphere energy balance. These changes can influence local and even global climate. The above mentioned change of water distribution influences many factors of energy transfer, e.g. thermal capacity, thermal conductivity, and albedo. We further hypothesize that water distribution on the microscopic scale is changed due to water repellency. This means that the thermal conductivity as a function of water content ?(?) of hydrophilic and water repellent soils may not be unique. To test our hypotheses we are conducting lysimeter experiments. All components of the water and energy balances are measured in and on top of lysimeters filled with strongly water repellent soil. Reference lysimeters are filled with the same substrate which was treated with surfactant to become hydrophilic. In addition to the lysimeter measurements we are conducting laboratory experiments to study fundamental processes and to determine the hydraulic and thermal properties of the hydrophilic and water repellent materials. We will also undertake field experiments to obtain measurements on a larger scale. Finally the results shall be incorporated in a numerical model for water and energy transport in the soil-atmosphere continuum.

Schonsky, Horst; Peters, Andre; Wessolek, Gerd

2013-04-01

87

SW—Soil and Water  

Microsoft Academic Search

The overgrowing population and the recent droughts are putting water resources under pressure and calling for new approaches for water planning and management if escalating conflicts are to be avoided and environmental degradation is to be reversed. As countries are using their water resources with growing intensity, poor rainfall increasingly leads to national water crises as water tables fall and

Ragab Ragab; Christel Prudhomme

2002-01-01

88

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

89

ESTIMATION OF GROUND WATER RECHARGE USING SOIL MOISTURE BALANCE APPROACH  

E-print Network

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

Kumar, C.P.

90

Investigation of indigenous water, salt and soil for solar ponds  

NASA Astrophysics Data System (ADS)

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

Marsh, H. E.

91

Analysis of the response of soil water to climate change  

SciTech Connect

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

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

1994-06-01

92

DIVISION S-6—SOIL & WATER MANAGEMENT & CONSERVATION Soil Water Retention as Related to Topographic Variables  

Microsoft Academic Search

long been routinely used in soil mapping (Northcote, 1954). Geomorphometry was proposed as a data source Digital elevation models were proposed and used as a data source to predict soil properties (Moore et al., 1993; McKenzie to estimate soil properties. This study evaluated variability of texture and water retention of soils for a gently sloping 3.7-ha field located and Austin,

A. Pachepsky; D. J. Timlin; W. J. Rawls

93

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

Microsoft Academic Search

Agricultural producers require knowledge of soil water at plant rooting depths, while many remote sensing studies have focused on surface soil water or mechanistic models that are not easily parameterized. We developed site-specific empirical models to predict spring soil water content for two Montana ranches. Calibration data sample sizes were based on the estimated variability of soil water and the

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

2008-01-01

94

Name ___________________________________________ Soil, Water and Forage Testing Laboratory  

E-print Network

Name ___________________________________________ Soil, Water and Forage Testing Laboratory + Micronutrients (Micro) $17 per sample (in addition to Suite 1, DTPA Zn, Fe, Cu, and Mn) 3. R + Micro + Hot Water limestone test) 7. R + Micro + B + Lime + Organic Matter + Sal $74 per sample (in addition to Suite 3, adds

95

Name ___________________________________________ Soil, Water and Forage Testing Laboratory  

E-print Network

Name ___________________________________________ Soil, Water and Forage Testing Laboratory + Micronutrients (Micro) $17 per sample (In addition to suite 1, DTPA Zn, Fe, Cu, and Mn) 3. R + Micro + Hot Water acidity titration test) 7. R + Micro + B + Lime + Organic Matter + Sal $74 per sample (In addition

96

Interactions of Soil Minerals with Organic Components and Microorganisms  

Microsoft Academic Search

Minerals, organic matter and microorganisms of the pedosphere are the key factors necessary for soil formation (pedogenesis) and other soil processes (1). The mineral composition of soil is a major part of the ecology of microorganisms. Interaction of soil minerals with microorganisms affects the metabolic transformation of natural and xenobiotic organic compounds and the fate of metals and other inorganic

BOLLAG Jean-Marc; LEYVAL Corinne

97

On the influence of coarse fragments on soil water retention  

Microsoft Academic Search

The classical determination of the soil water retention curve (SWRC) by measuring soil water content $\\\\theta$ 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

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

2009-01-01

98

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

Microsoft Academic Search

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

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

1999-01-01

99

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

100

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.

101

Soil Interfaces in a Changing World International Symposium of Interactions of Soil Minerals with  

E-print Network

Sciences, University of Delaware, Newark, Delaware, USA, and Institute of Soil Science, UniversitySoil Interfaces in a Changing World 6th ISMOM International Symposium of Interactions of Soil Minerals with Organic Components and Microorganisms 3rd InterCongress of Commission 2.5 IUSS Soil chemical

Sparks, Donald L.

102

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

103

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

104

Soil and Water Conservation Activities for Scouts.  

ERIC Educational Resources Information Center

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

Soil Conservation Service (USDA), Washington, DC.

105

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

E-print Network

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

Russo, Bernard

106

SOIL AND WATER ASSESSMENT TOOL (SWAT)  

EPA Science Inventory

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

107

Heat Exchange in Air, Water, and Soil  

NSDL National Science Digital Library

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

Eichinger, John

2009-05-30

108

A multi-scale ''soil water structure'' model based on the pedostructure concept  

NASA Astrophysics Data System (ADS)

Current soil water models do not take into account the internal organization of the soil medium and, a fortiori, the physical interaction between the water film surrounding the solid particles of the soil structure, and the surface charges of this structure. In that sense they empirically deal with the physical soil properties that are all generated from this soil water-structure interaction. As a result, the thermodynamic state of the soil water medium, which constitutes the local physical conditions, namely the pedo-climate, for biological and geo-chemical processes in soil, is not defined in these models. The omission of soil structure from soil characterization and modeling does not allow for coupling disciplinary models for these processes with soil water models. This article presents a soil water structure model, Kamel®, which was developed based on a new paradigm in soil physics where the hierarchical soil structure is taken into account allowing for defining its thermodynamic properties. After a review of soil physics principles which forms the basis of the paradigm, we describe the basic relationships and functionality of the model. Kamel® runs with a set of 15 soil input parameters, the pedohydral parameters, which are parameters of the physically-based equations of four soil characteristic curves that can be measured in the laboratory. For cases where some of these parameters are not available, we show how to estimate these parameters from commonly available soil information using published pedotransfer functions. A published field experimental study on the dynamics of the soil moisture profile following a pounded infiltration rainfall event was used as an example to demonstrate soil characterization and Kamel® simulations. The simulated soil moisture profile for a period of 60 days showed very good agreement with experimental field data. Simulations using input data calculated from soil texture and pedotransfer functions were also generated and compared to simulations of the more ideal characterization. The later comparison illustrates how Kamel® can be used and adapt to any case of soil data availability. As physically based model on soil structure, it may be used as a standard reference to evaluate other soil-water models and also pedotransfer functions at a given location or agronomical situation.

Braudeau, E.; Mohtar, R. H.; El Ghezal, N.; Crayol, M.; Salahat, M.; Martin, P.

2009-02-01

109

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...

110

Investigation of indigenous water, salt and soil for solar ponds  

SciTech Connect

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

Marsh, H.E.

1983-08-01

111

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

112

Modeling structural influences on soil water retention  

USGS Publications Warehouse

A new model quantities the effect of soil structure, considered as the arrangement of particles in the soil, on soil water retention. The model partitions the pore space into texture-related and structure-related components, the textural component being what can be deduced to exist if the arrangement of the particles were random, and the structural component being the remainder. An existing model, based on particle-size distributions, represents the textural component, and a new model, based on aggregate-size distributions, represents the structural component. This new model makes use of generalized properties that vary little from one medium to another, thereby eliminating any need for empirically tilted parameters. It postulates a particular character of the structural pore space that in same ways resembles texture-related pore space, but with pore shape related to the breadth of the aggregate-size distribution. To predict a soil water retention curve, this model requires the soil's porosity and particle- and aggregate-size distributions. Tested with measurements for 17 samples from two sources, it fits the data much better than does a model based on texture alone. Goodness of fit indicated by correlation coefficients ranged from 0.908 to 0.998 for the new model, compared with a range of 0.686 in 0.955 for the texture-based model.

Nimmo, J. R.

1997-01-01

113

Water and Solute Flow in a Highly-Structured Soil  

E-print Network

. An improved understanding of why water and solute follow particular flow paths is needed to identify soils that allow agricultural chemicals to move rapidly to groundwater. The rate that water and contaminants are transferred from the soil surface...

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

114

Simulation of Soil Water Content Variability in a Heavy Clay Soil under Contrasting Soil Managements  

NASA Astrophysics Data System (ADS)

Soil water content (SWC) is a key variable for numerous physical, chemical and biological processes that take place at or near the soil surface. Understanding the spatial and temporal variability of SWC at the field scale is of prime importance for implementing efficient measurement strategies in applications. The aim of this study was to characterize the spatial and temporal variation of gravimetric SWC in a heavy clay soil, in a wheat-sunflower-legume rotation under conventional (CT) and no-till (NT) using a simple water balance model. An experimental field in SW Spain, where conventional (CT) and no-till (NT) management of a heavy clay soil are being compared since 1983, was sampled for gravimetric SWC on 38 occasions during 2008 and 2009. Topsoil clay content across the six plots was on average 55%, with a standard deviation of 2.7%. The soil profile was sampled at 54 locations, evenly distributed over the three CT and NT plots, at depths of 0-10, 25-35, and 55-65 cm. Topsoil water retention curves (SWRC) were determined in the laboratory on undisturbed soil samples from each of the 54 locations. A weather station recorded daily precipitation and evapotranspiration, as calculated by the Penman-Monteith FAO equation. The water balance was calculated using the Thornthwaite-Mather model with a daily time step. Three parameters, water holding capacity, and water evaporation corrector coefficients for each of the two years, were inversely estimated at the 54 SWC observation points and probability density functions were identified. Spatial variability of SWC was estimated using a Monte Carlo approach, and simulated and observed variability were compared. This Monte Carlo scheme, using a simple water balance model with only three parameters, was found to be useful for evaluating the influence of soil management on the variability of SWC in heavy clay soils.

Pedrera, A.; Vanderlinden, K.; Martínez, G.; Espejo, A. J.; Giráldez, J. V.

2012-04-01

115

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

E-print Network

, Soil and Water Research Laboratory, Temple, TX Sampling Components: 1) Automated vs Manual sampling 2Agricultural Research Service Grassland, Soil and Water Research Laboratory, Temple, TX Monitoring, Soil and Water Research Laboratory, Temple, TX Objectives for Today · Small watershed monitoring

116

Indicators for Soil and Water Conservation on Rangelands INTRODUCTION  

E-print Network

Chapter II - 1 - CHAPTER II Indicators for Soil and Water Conservation on Rangelands INTRODUCTION conservation and maintenance of soil and water resources as a criterion, defined as a category of conditions sustainability. As a criterion, conservation and maintenance of soil and water resources is too general

Wyoming, University of

117

NEZ PERCE SOIL AND WATER CONSERVATION DISTRICT CULDESAC, IDAHO 83524  

E-print Network

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

118

Post-doctoral Fellow Soil and Water Conservation Position specification  

E-print Network

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

119

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

120

Modelling for planning soil and water conservation: a critical review  

Microsoft Academic Search

Degradation of soil and water resources, which is increasing throughout the World, is affecting directly and indirectly all the vital processes on the Earth's surface. This is partially due to non-appropriate land use planning, where soil and water conservation must be the most important components. Global climate changes may contribute to accelerate some soil and water degradation processes and their

SENTÍS Ildefonso

121

Spatial variability constraints to modeling soil water at different scales  

Microsoft Academic Search

There is increasing interest in modeling soil water content over relatively large areas or scales. In general, the spatial variability of soil water content increases with scale, but it is not known how much or at which scales. High spatial variability constrains soil water models by reducing the accuracy of input parameters, calibration and verification data. It may also require

M Seyfried

1998-01-01

122

Dynamic Soil-Structure Interaction Analysis by a Hybrid Method  

Microsoft Academic Search

In this paper, the dynamic interaction between soil and a cooling tower is analysed using a hybrid method that combines a finite element method and a boundary element method. The dynamic behavior of the soil half-space is investigated in detail. The effect of soil-structure interaction on the gust responses of draught column-supported hyperbolic cooling towers is estimated, and a comparison

Zheng-Wen Yang; Wen-Da Lu

1994-01-01

123

A Review on Temporal Stability of Soil Water Contents  

NASA Astrophysics Data System (ADS)

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 published data on TC SWC and to determine knowledge gaps. Mean relative difference (MRD) values and associated standard deviations (SDRD) were digitized from 157 graphs in 37 publications and analyzed. The MRD followed generally a Gaussian distribution with the determination coefficient R2 > 0.84. The standard deviation of MRD (SDMRD) showed a trend of increase with scale. No relationship between SDMRD and R2 was observed. The smallest R2 values were mostly found for negatively skewed and platykurtic MRD distributions. An analysis of seven measurement-, terrain-, and climate-related TS SWC controls suggested strong interactions and showed that combined effects are typically observed. Many of the existing datasets on TS WCS are mostly byproducts of soil water dynamics studies in agronomic or environmental projects. Future research should include more focused TS SWC studies tailored to understand interactions of controls, underlying mechanisms, and efficiency of applications.

Vanderlinden, Karl; Vereecken, Harry; Hardelauf, Horst; Herbst, Michael; Martínez, Gonzalo; Cosh, Michael H.; Pachepsky, Yakov A.

2013-04-01

124

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

125

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...

126

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 ...

127

Wetting properties of fungi mycelium alter soil infiltration and soil water repellency in a ?-sterilized wettable and repellent soil.  

PubMed

Soil water repellency (SWR) has a drastic impact on soil quality resulting in reduced infiltration, increased runoff, increased leaching, reduced plant growth, and increased soil erosion. One of the causes of SWR is hydrophobic fungal structures and exudates that change the soil-water relationship. The objective of this study was to determine whether SWR and infiltration could be manipulated through inoculation with fungi. The effect of fungi on SWR was investigated through inoculation of three fungal strains (hydrophilic -Fusarium proliferatum, chrono-amphiphilic -Trichoderma harzianum, and hydrophobic -Alternaria sp.) on a water repellent soil (WR-soil) and a wettable soil (W-soil). The change in SWR and infiltration was assessed by the water repellency index and cumulative infiltration respectively. F. proliferatum decreased the SWR on WR-soil and slightly increased SWR in W-soil, while Alternaria sp. increased SWR in both the W-soil and the WR-soil. Conversely T. harzianum increased the SWR in the W-soil and decreased the SWR in the WR-soil. All strains showed a decrease in infiltration in W-soil, while only the F. proliferatum and T. harzianum strain showed improvement in infiltration in the WR-soil. The ability of fungi to alter the SWR and enmesh soil particles results in changes to the infiltration dynamics in soil. PMID:23245615

Chau, Henry Wai; Goh, Yit Kheng; Vujanovic, Vladimir; Si, Bing Cheng

2012-12-01

128

The available-water capacities of North Auckland soils  

Microsoft Academic Search

Available-water capacities of the principal groups of soils of high clay content in North Auckland have been determined. Within each main soil group they are markedly uniform.Among the soils on sedimentary parent rocks podzolisation is accompanied by larger available-water capacities in the A horizons and smaller ones in some B horizons than are found for unpodzolised soils. Of the soils

M. W. Gradwell

1971-01-01

129

Effect of different water content, sample number, and soil type on determination of soil water using a home microwave oven  

Microsoft Academic Search

Soil water content values determined on three soil types at three water contents using a home-type microwave oven were within 1% of the values obtained using a conventional electric oven to dry samples. Four 50–60 g soil samples of different type and different water content were fully dried in 20 min in the microwave oven, but 45 min was needed

Chin S. Tan

1992-01-01

130

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

Microsoft Academic Search

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

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

2004-01-01

131

Effect of temperature and water on gaseous emissions from soils treated with animal slurry  

Microsoft Academic Search

Microbial respiration and denitrification are greatly affected by abiotic factors, but they are difficult to assess in natural environments. Under controlled conditions the interactions between temperature and soil water content on microbial respiration, NâO production, and denitrification in soil amended with animal slurries were studied. The effects of the abiotic factors on the biological processes were monitored for 8 wk

Michael Maag; Finn P. Vinther

1999-01-01

132

UNIVERSITY OF MINNESOTA Twin Cities Campus Department of Soil, Water, and Climate  

E-print Network

UNIVERSITY OF MINNESOTA Twin Cities Campus Department of Soil, Water, and Climate College of Food of biofuel production on soil dynamics and environmental quality; · effects of climate and land use change and the coupled interactions between the two. Students have the option of developing a program based on one

Minnesota, University of

133

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

PubMed Central

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

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

2008-01-01

134

Physical properties and soil-water balance of key soils of the Opotiki region, North Island, New Zealand  

Microsoft Academic Search

The soil pattern of the Opotiki region consists of alluvial soils and soils derived from volcanic ash. The soils range from recent soils to gley soils and yellow-brown loams and are discussed in terms of soil physical properties and water balance. Levels of available water are generally high to very high except where root depth is restricted by high ground

W. C. Rijkse

1989-01-01

135

Arbuscular mycorrhizae and soil\\/plant water relations  

Microsoft Academic Search

Augé, R. M. 2004. Arbuscular mycorrhizae and soil\\/plant water relations. Can. J. Soil Sci. 84: 373-381. The water relations of arbuscular mycorrhizal (AM) plants have been compared often. However, virtually nothing is known about the comparative water relations of AM and nonAM soils or about the relative influence of AM colonization of soil vs. AM colonization of plants on host

Robert M. Augé

136

Watershed scale temporal stability of soil water content  

Microsoft Academic Search

The recognition of temporally stable locations with respect to soil water content is of importance for soil water management decisions, especially in sloping land of watersheds. Neutron probe soil water content (0 to 0.8m), evaluated at 20 dates during a year in the Loess Plateau of China, in a 20ha watershed dominated by Ust-Sandiic Entisols and Aeolian sandy soils, were

Wei Hu; Mingan Shao; Fengpeng Han; Klaus Reichardt; Jing Tan

2010-01-01

137

Soil phosphorus levels needed for equal P uptake from four soils with different water contents at the same water potential  

Microsoft Academic Search

Soil volumetric water contents, ?, at ?33 kPa potential may vary with soil from 0.06 to 0.70. Because P diffusion depends on ?, most economic P fertilizer rates required for different soils may require adjusting according to their soil-water relationships. The objective of this study was, after experimentally verifying a mechanistic nutrient uptake model on a series of soils varying

M. S. Cox; S. A. Barber

1992-01-01

138

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

139

Soil erosion by water - model concepts and application  

NASA Astrophysics Data System (ADS)

Soil erosion is not a continuous process but the result of isolated surface runoff events, whose erosional effects are determined by numerous temporally and spatially varying variables. Thus the monitoring of soil loss by direct observation is extremely limited with respect to space and time. Usually observation plots cover an area of less than 100 m2 and the observation period is less than 10 years. In order to estimate soil losses by water erosion for others than empirically observable conditions, mathematical models are needed, which are able to describe the interaction of the different physical mechanisms involved either statistically or on the basis of physical algorithms. Such models are absolutely essential for risk prognoses on catchment and regional scale. Besides the aspect of soil conservation the delivery of sediments and sediment bound pollutants into surface water bodies are of increasing relevance in this context. Based on an exemplary selection of existing water erosion models this contribution aims to give an overview over different mathematical approaches used for the description of particle detachment, transport and deposition of soil particles. According to the chronology in the development of soil erosion models empirical algorithms will be presented first based on the USLE approach. However, since purely empirical models like USLE are limited to the estimation of annual soil loss further attempts in soil erosion modelling are focussed on event based estimations considering the fact that soil erosion is not a continuous process but the result of isolated runoff events. One of the first models of this type was CREAMS using physically based algorithms in combination with empirical ones in order to describe the basic erosion processes. Today there are diverse soil erosion models available following in principle the CREAMS concept but using different algorithms in detail. Concerning particle detachment, transport and deposition alternative approaches will be discussed taking account of the models WEPP, EUROSEM, IISEM and EROSION 3D. In order to provide a better representation of spatially heterogeneous catchments in terms of landuse, soil, slope, and rainfall most of recently developed models operate on a grid-cell basis or other kinds of sub-units, each having uniform characteristics. These so-called "Distributed Models" accepts inputs from raster based geographic information system (GIS). The cell-based structure of the models also allows to generate drainage paths by which water and sediment can be routed from the top to the bottom of the respective watershed. One of the open problems in soil erosion modelling refers to the spontaneous generation of erosion rills without the need for pre-existing morphological contours. A promising approach to handle this problem was realized first in the RILLGROW model, which uses a cellular automaton system in order to generate realistic rill patterns. With respect to the above mentioned models selected applications will be presented and discussed regarding their usability for soil and water conservation purposes.

Schmidt, Juergen

2010-05-01

140

Experimental Investigation of Water Flow through Hydrophobic Soils  

NASA Astrophysics Data System (ADS)

Water flow through soils is traditionally been modeled using the richards equation and the water retention and unsaturated hydraulic properties properties are characterized using the equations such as the van Genuchten-Mualem model. The van genuchten water retention model assumes that the capillary pressure in soils increases as the water content in the soils decreases. Hydrophobic soils deviate from the traditional VG characterization because they repel water in dry state. In this study, we perform an experimental investigation on how hydrophobicity impacts the hydraulic characteristics of soils. We will study the impact of hydrophobicity on soil hydraulics as a function of the degree of hydrophobicity as well as the grain size. Finally, we will characterize the soil hydraulic properties of hydrophobic soils using a new model.

Twarakavi, N.; Saito, H.; Kalra, A.

2012-12-01

141

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

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

142

Mucilage exudation facilitates root water uptake in dry soils  

NASA Astrophysics Data System (ADS)

As plant roots take up water and the soil dries, water depletion is expected to occur in the rhizosphere. However, recent experiments showed that the rhizosphere of lupines was wetter than the bulk soil during root water uptake. On the other hand, after irrigation the rhizosphere remained markedly dry and it rewetted only after one-two days. We hypothesize that: 1) drying/wetting rates of the rhizosphere are controlled by mucilage exuded by roots; 2) mucilage alters the soil hydraulic conductivity: in particular, wet mucilage increases the soil hydraulic conductivity and dry mucilage makes the soil water repellent; 3) mucilage exudation favors root water uptake in dry soil; and 4) dry mucilage limits water loss from roots to dry soils. We used a root pressure probe to measure the hydraulic conductance of artificial roots sitting in soils. As an artificial root we employed a suction cup with a diameter of 2 mm and a length of 45 mm. The root pressure probe gave the hydraulic conductance of the soil-root continuum during pulse experiments in which water was injected into or sucked from the soil. First, we performed experiments with roots in a relatively dry soil with a volumetric water content of 0.03. Then, we repeated the experiment with artificial roots covered with mucilage and then placed into the soil. As a model for mucilage, we collected mucilage from Chia seeds. The water contents (including that of mucilage) in the experiments with and without mucilage were equal. The pressure curves were fitted with a model of root water that includes rhizosphere dynamics. We found that the artificial roots covered with wet mucilage took up water more easily. In a second experimental set-up we measured the outflow of water from the artificial roots into dry soils. We compared two soils: 1) a sandy soil and 2) the same soil wetted with mucilage from Chia seeds and then let dry. The latter soil became water repellent. Due to the water repellency, the outflow of water from the root in this soil was significantly reduced. The experiments demonstrated that mucilage increased the hydraulic conductance of the root-soil continuum and facilitated the extraction of water from dry soils. The increase in conductivity resulted from the higher water content of the soil near the roots. Mucilage has a lower surface tension than pure water and a higher viscosity, resulting in a slower penetration of mucilage into the soil. After mucilage was placed into the soil, it did not spread into the bulk soil, but it remained near the roots, maintaining the rhizosphere wetter and more conductive than the bulk soil. However, as mucilage dried, it turned water repellent and reduced the back flow of water from the root to soil. We hypothesize that mucilage exudation is a plant strategy to locally and temporally facilitate water uptake from dry soils. After drying, mucilage becomes water repellent and may limit the local uptake of water after irrigation. On the other hand, mucilage water repellency may as well be a strategy to reduce water loss from roots to dry soils.

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

2014-05-01

143

Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable for  

E-print Network

Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable for methods used by laboratory. Nitrogen Soil Fertility Recommendations for Texas Fiber Crop 0 2 4 6 8 10 12 14 16 18 20 updated 140 130 120 110 100 #12;Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable

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Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable for  

E-print Network

Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable for methods used by laboratory. Nitrogen Soil Fertility Recommendations for Forage Crops 0 2 4 6 8 10 12 14 16 18 20 updated on 3 (ESTABLISHMENT) 40 35 30 25 20 20 15 10 5 0 #12;Soil, Water and Forage Testing Laboratory Nitrogen

145

Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable for  

E-print Network

Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable for methods used by laboratory. Nitrogen Soil Fertility Recommendations for Texas Grain and Row Crops 0 2 4 6 8 10 12 14 16 18 20/A) 295 295 290 285 280 275 275 270 265 260 255 #12;Soil, Water and Forage Testing Laboratory Nitrogen

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Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable for  

E-print Network

Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable for methods used by laboratory. Nitrogen Soil Fertility Recommendations for Texas Vegetable, Nut and Fruit Production 0 2 4 6 8 110 105 100 100 95 90 85 80 80 #12;Soil, Water and Forage Testing Laboratory Nitrogen recommendations

147

Willie Harris Address: Soil and Water Science Department  

E-print Network

1 Willie Harris Address: Soil and Water Science Department 2169 McCarty Hall University of Florida in Graduate Research, 2005 Soil and Water Science Department Outstanding Teacher/Advisor of the Year, 2003, classification, and utilization of Spodosols. USDA-Soil Conservation Service, U.S. Government Printing Office

Jawitz, James W.

148

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

NASA Technical Reports Server (NTRS)

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

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

1992-01-01

149

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

150

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

E-print Network

Stable or unstable wetting fronts in water repellent soils ± effect of antecedent soil moisture wetting; Preferential ¯ow; Critical soil moisture content 1. Introduction Simulation models are widely.V. All rights reserved. P I I S 0 1 6 7 - 1 9 8 7 ( 9 8 ) 0 0 0 8 2 - 8 #12;wetting fronts in soils may

Walter, M.Todd

151

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

152

Interaction between soil hydrology and boundary-layer development  

Microsoft Academic Search

A two-layer model of soil hydrology and thermodynamics is combined with a one-dimensional model of the planetary boundary layer to study various interactions between evolution of the boundary layer and soil moisture transport. Boundary-layer moistening through surface evaporation reduces the potential and actual surface evaporation as well as the boundary-layer growth. With more advanced stages of soil drying, the restricted

H.-L. Pan; L. Mahrt

1987-01-01

153

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

E-print Network

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

Paris-Sud XI, Université de

154

Quantifying root water extraction by rangeland plants through soil water modeling  

Microsoft Academic Search

We used soil water modeling as a tool to quantify water use of non-cultivated plant communities based on easily measured field\\u000a data of soil water contents, soil hydraulic properties, and leaf area index. The model was applied in the mixed-grass prairie,\\u000a considering a dynamic and non-uniform root distribution, the effect of soil water stress on plant water uptake, as well

Xuejun Dong; Bob D. Patton; Anne C. Nyren; Paul E. Nyren; Lyle D. Prunty

2010-01-01

155

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...

156

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

EPA Science Inventory

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

157

Method for Measuring Enriched Levels of Deuterium in Soil Water.  

National Technical Information Service (NTIS)

This report describes procedures for analyzing hydrogen isotope ratios. Hydrogen is separated from liquid water or soil water by reacting the water with heated uranium. An isotope-ratio mass spectrometer determines the atom % deuterium in the hydrogen to ...

J. L. Oliphant, T. F. Jenkins, A. R. Tice

1982-01-01

158

Effects of land use on temporal-spatial variability of soil water and soil-water conservation  

Microsoft Academic Search

The Loess Plateau of China suffers serious soil erosion primarily resulting from irrational land uses. Soil water plays a critical role influencing vegetation-restoration processes, but varies with temporal and spatial characteristics, of concern to many researchers. However, few studies consider the influence of deep soil water and varied weather patterns in a semi-arid region. Four vegetation types chosen for this

Chen Zeng; Mingan Shao; Quanjiu Wang; Jun Zhang

2011-01-01

159

Lepidium latifolium : plant nutrient competition-soil interactions  

Microsoft Academic Search

Exotic weeds are invading rangelands of the western United States at unprecedented rates. Understanding plant-soil relationships and competitive interactions of invasive weeds is crucial in long-term control strategies. In a greenhouse experiment, we investigated the influence of soil nutrient depletion on plant growth and plant competition between the exotic invasive weeds, Lepidium latifolium (invading wetlands) and Bromus tectorum (invading a

Robert R. Blank; Robert G. Qualls; James A. Young

2002-01-01

160

Water and Soil Conservation Experiments at Spur, Texas.  

E-print Network

LIBRARY, TEXAS AGRICULTURAL EXPERIMENT STATION A. B. CONNER, DIRECTOR, College Station, Texas BULLETIN NO. 587 WATER AND SOIL CONSERVATION IXPERI- MENTS AT SPUR, TEXAS Division of Agronomy and the Soil Conservation Service, United States... JULY 1940 WATER AND SOIL CONSERVATION EXPERIMENTS AT SPUR, TEXAS R. E. DICKSON, B. C. LANGLEY, AND C. E. FISHER* Texas Agricultural Experiment Station in Cooperation With the Soil Conservation Service, United States Department of Agriculture "Much...

Langley, B. C. (Bryon Caldwell); Dickson, R. E.; Fisher, Charles E. (Charles Emil)

1940-01-01

161

Global distribution of plant-extractable water capacity of soil  

USGS Publications Warehouse

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

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

1996-01-01

162

A one-dimensional model of water flow in soil-plant systems based on plant architecture  

Microsoft Academic Search

The estimation of root water uptake and water flow in plants is crucial to quantify transpiration and hence the water exchange\\u000a between land surface and atmosphere. In particular the soil water extraction by plant roots which provides the water supply\\u000a of plants is a highly dynamic and non-linear process interacting with soil transport processes that are mainly determined\\u000a by the

Michael Janott; Sebastian Gayler; Arthur Gessler; Mathieu Javaux; Christine Klier; Eckart Priesack

2011-01-01

163

The dependence of water potential in shoots of Picea abies on air and soil water status  

E-print Network

The dependence of water potential in shoots of Picea abies on air and soil water status A. Sellin there is sucient water storage in the soil the water potential Wx in shoots of Norway spruce [Picea abies (L water potential W is above �0X62 MPa, the principal factor causing water de®ciency in shoots of P. abies

Paris-Sud XI, Université de

164

Soil CO? dynamics in a tree island soil of the Pantanal: the role of soil water potential.  

PubMed

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

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

2013-01-01

165

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

PubMed Central

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

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

2013-01-01

166

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...

167

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

E-print Network

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

Prathapar, Sanmugam Ahembaranathan

2012-06-07

168

Shor Lab "Soil Water" Project Undergraduate Research Opportunity  

E-print Network

biofilm EPS level, drying condition and water retention. 5. Use microfluidic devices to systematically the water retention curve for whole soils. Bacteria can produce up to five times their mass in EPS, to characterize the affects of EPS on soil water retention. To achieve that, we need to first understand effect

Shor, Leslie McCabe

169

Semiempirical model of soil water hysteresis  

USGS Publications Warehouse

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

Nimmo, J. R.

1992-01-01

170

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

171

Soil Water Content vs. Tension at three sites Horizon A  

E-print Network

Results Soil Water Content vs. Tension at three sites § Horizon A § Horizon Bw § Horizon BC (site 263 Water Holding Properties Soil Properties 0.2 0.4 0.6 0.1 1 10 100 1000 Site Three 0.1 1 10 100 has lower bulk density and higher porosity � Site one soil holds less water at field capacity (10 k

172

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

173

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

174

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

NASA Astrophysics Data System (ADS)

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

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

2014-10-01

175

Water-soluble organic matter in forest soils  

Microsoft Academic Search

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

A. T. Kuiters; W. Mulder

1993-01-01

176

Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable for  

E-print Network

Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable for methods used by laboratory. Nitrogen Soil Fertility Recommendations for Lawn and Gardens 0 2 4 6 8 10 12 14 16 18 20 updated. Nitrogen Soil Fertility Recommendations for Lawn and Gardens 25 30 35 40 45 50 55 60 65 70 75 updated on 3

177

Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable for  

E-print Network

Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable for methods used by laboratory. Nitrogen Soil Fertility Recommendations for Texas Turf and Landscapes 0 2 4 6 8 10 12 14 16 18 20 Testing Laboratory Nitrogen recommendations applicable for methods used by laboratory. Nitrogen Soil

178

Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable for  

E-print Network

Soil, Water and Forage Testing Laboratory Nitrogen recommendations applicable for methods used by laboratory. Nitrogen Soil Fertility Recommendations for Oil Crops 0 2 4 6 8 10 12 14 16 18 20 updated on 3. Nitrogen Soil Fertility Recommendations for Oil Crops 0 2 4 6 8 10 12 14 16 18 20 updated on 3

179

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

ERIC Educational Resources Information Center

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

Foster, Albert B.; Fox, Adrian C.

180

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

181

Onset of water stress, hysteresis in plant conductance, and hydraulic lift: Scaling soil water dynamics  

E-print Network

for harvesting most of the soil water, which then flows within the plant vascular system up to the leaves whereOnset of water stress, hysteresis in plant conductance, and hydraulic lift: Scaling soil water] Estimation of water uptake by plants and subsequent water stress are complicated by the need to resolve

Katul, Gabriel

182

Water quality transformations during soil aquifer treatment at the Mesa Northwest Water Reclamation Plant, USA  

Microsoft Academic Search

Water quality transformations during soil aquifer treatment at the Mesa Northwest Water Reclamation Plant (NWWRP) were evaluated by sampling a network of groundwater monitoring wells located within the reclaimed water plume. The Mesa Northwest Water Reclamation Plant has used soil aquifer treatment (SAT) since it began operation in 1990 and the recovery of reclaimed water from the impacted groundwater has

P. Fox; K. Narayanaswamy; A. Gen; J. E. Drewes

183

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

E-print Network

that the water-entry value, in terms of soil water potential, is positive in repellent soils, and negative to measure water-repellency is the water drop penetration time (WDPT) test (Van't Woudt, 1959, 1969; Letey, 1969). Three drops of distilled water from a standard medicine dropper are placed on the smoothed

Wang, Zhi "Luke"

184

Genetic by environment interactions affect plant–soil linkages  

PubMed Central

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

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

2013-01-01

185

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

186

Microbial enhancement of hydrazine degradation in soil and water  

SciTech Connect

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

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

1987-09-01

187

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

188

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 objective of this study was to test the potential of integrated non invasive geophysics and ground-image analysis and to quantify the effect of the soil vegetation interaction on the water balance of a fallow land at the local and plot scale. We measured repeatedly in space and time local soil saturation and vegetation cover over two small plots located in southern Sardinia, Italy, during an infiltration experiment. One plot was left unseeded and the other was cultivated. The comparative analysis of the experimental data evidenced a positive feedback between weed growth and infiltration at the fallow plot. A simple bucket model captured the different soil moisture dynamics at the two plots during the infiltration experiment and was used to estimate the impact of the soil vegetation feedback on the yearly water balance at the site.

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

2013-04-01

189

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

NASA Astrophysics Data System (ADS)

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

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

2014-08-01

190

Sorption of nano-C60 clusters in soil: hydrophilic or hydrophobic interactions?  

PubMed

We studied the sorption behaviour of fullerene nano-C(60) particles (nC(60)) in soil from binary solvent mixtures of ethanol-water in order to critically evaluate the previous reports in the literature that the partitioning mechanism explains the soil sorption of fullerene C(60) as hydrophobic molecules. The sorption of nC(60) particles was studied in a range of solvent mixtures by changing volume fractions of ethanol from 20 to 100 percent. Sorption and particle characteristics were found to be very different in ethanol : water mixtures above and below 60% ethanol. In the range of 20-60% ethanol, sorption increased from 1.2 to 14.6 L kg(-1) accompanied by a change in zeta (?) potential from -32.4 to -7.2 mV. This observation can be attributed to hydrophilic interactions that negatively charged nC(60) particles undergo with soil colloids and water molecules. From 60% to 100% ethanol volume fractions, hydrophobic interactions of weakly charged nanoparticles may control the overall extent of soil sorption. The findings of this study indicate the importance of hydrophilic forces in controlling the sorption behaviour of nC(60) particles which are stabilized in water dominated solvent mixtures. The validity of the partitioning mechanism and K(OC) modelling approach in describing and estimating the sorption of nC(60) particles in soil (previously suggested in the literature) are, therefore, questioned. PMID:21394375

Forouzangohar, Mohsen; Kookana, Rai S

2011-05-01

191

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

NASA Astrophysics Data System (ADS)

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

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

2008-01-01

192

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

E-print Network

distribution of the forecast. We use observed soil moisture data from four SCAN sites: Ames, IA (42°00' N 933.13 SEASONAL SOIL MOISTURE PREDICTION USING A CLIMATE-PLANT-SOIL COUPLED AGROECOSYSTEM WATER moisture prediction is a critical factor for economic decision-making in agriculture. The national outlook

Takle, Eugene S.

193

EFFICIENCY OF SOIL CORE AND SOIL-PORE WATER SAMPLING SYSTEMS  

EPA Science Inventory

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

194

Soil porosity characteristics and water movement under zero tillage in silty soils in Argentinian Pampas  

Microsoft Academic Search

The objective of this study was to identify pore characteristics (quantity, distribution, stability and orientation of pores) that condition water dynamics under continuous zero tillage (ZT) on silty soils of the Argentinian Rolling Pampas. Soil properties were analyzed under continuous chisel plough (CP) and ZT treatments from three trials with different duration and crop sequence. The following soil properties of

M. C. Sasal; A. E. Andriulo; M. A. Taboada

2006-01-01

195

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

196

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

PubMed

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

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

2011-06-01

197

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. PMID:21606374

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

198

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

199

Aerodynamic method for obtaining the soil water retention curve  

NASA Astrophysics Data System (ADS)

A new method for the rapid plotting of the soil water retention curve (SWRC) has been proposed that considers the soil water as an environment limited by the soil solid phase on one side and by the soil air on the other side. Both contact surfaces have surface energies, which play the main role in water retention. The use of an idealized soil model with consideration for the nonequilibrium thermodynamic laws and the aerodynamic similarity principles allows us to estimate the volumetric specific surface areas of soils and, using the proposed pedotransfer function (PTF), to plot the SWRC. The volumetric specific surface area of the solid phase, the porosity, and the specific free surface energy at the water-air interface are used as the SWRC parameters. Devices for measuring the parameters are briefly described. The differences between the proposed PTF and the experimental data have been analyzed using the statistical processing of the data.

Alekseev, V. V.; Maksimov, I. I.

2013-07-01

200

Analysis of soil and water for TATB content  

SciTech Connect

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

Schaffer, C.L.

1992-11-01

201

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

202

Soil water content and infiltration in agroforestry buffer strips  

Microsoft Academic Search

Agroforestry practices are receiving increased attention in temperate zones due to their environmental and economic benefits.\\u000a To test the hypothesis that agroforestry buffers reduce runoff by increased infiltration, water use, and water storage; profile\\u000a water content and soil water infiltration were measured for a Putnam soil (fine, smectitic, mesic Vertic Albaqualf). The watershed\\u000a was under no-till management with a corn

Stephen H. Anderson; Ranjith P. Udawatta; Tshepiso Seobi; Harold E. Garrett

2009-01-01

203

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

NASA Astrophysics Data System (ADS)

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

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

2014-02-01

204

A review of soil and water conservation in China  

Microsoft Academic Search

The preservation and sustainable development of soil and water resources is one of the basic principles for the development\\u000a of China. Throughout the course of history, all the social improvement and economic development are deeply concerned with\\u000a soil loss and ecological environmental protection. It is now a common sense that soil and water conservation is the safety\\u000a insurance for national

Zhang Xingchang; Shao Mingan; Li Shiqing; Peng Keshan

2004-01-01

205

Soil water dynamics inside and outside of lysimeters  

NASA Astrophysics Data System (ADS)

Lysimeters are the one and only instrument to directly measure water fluxes through the upper an lower boundary of soil profiles. This allows to close the water balance including soil water storage, deep seepage and evapotranspiration. However, lysimeters force the water flow to the vertical direction while in reality lateral water movement is deemed to play an important role in soil water dynamics especially along hillslopes. We present an approach where we monitor soil water dynamics in lysimeters and in the field at the same location of a gentle hillslope. A cylindrical soil monolith is taken leaving the surrounding soil undisturbed. The monolith is used as a weighable lysimeter while the pit in the field is equipped with the same sensors (moisture, water potential, temperature) as the lysimeter. Based on this set up, we can evaluate in how far water flow inside the lysimeter corresponds to the situation in the field. The results demonstrate that lateral flow becomes important when the water content is close to saturation. This is true at the soil surface in case of surface runoff but also at the depth of a compacted plow pan where interflow is initiated. Under unsaturated conditions, the limitation of lysimeters to 1D flow seems to be an acceptable approximation even in slopy areas.

Vogel, Hans-Joerg; Rupp, Holger; Köhne, Max; Wollschläger, Ute

2014-05-01

206

Visual soil water status indicator for improved irrigation management  

Microsoft Academic Search

A device to aid in irrigation scheduling by visually indicating current soil water status relative to an upper and lower set point was developed and field tested. The device can be used by farm managers to easily evaluate current soil water status from a distance. This information can be used to guide irrigation scheduling decisions throughout the season. Seven farm

B. A King; R. W Wall; J. P Taberna Jr

2001-01-01

207

Soil Water Use by Ceanothus velutinus and Two Grasses  

Microsoft Academic Search

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

W. Lopushinsky; G. O. Klock

208

Bottom Soil and Water Quality Management in Shrimp Ponds  

Microsoft Academic Search

Marine shrimp farming has become an important component of aquaculture. Water and soil conditions have a great influence on the efficiency of shrimp production, and a review of water quality and bottom soil management will be provided. After a shrimp pond has been drained for harvest, organic carbon analyses can indicate if organic matter concentrations are too low (< 0.5%)

Claude E. Boyd

2003-01-01

209

GIS IN SOIL & WATER SCIENCE On-Campus Section 8197  

E-print Network

with the basic concepts of geographic information systems and applications focused on soil and water resourceSWS 4720C GIS IN SOIL & WATER SCIENCE On-Campus Section 8197 Fall 2014 Instructor Wade Ross wader, no technical help for setup/debugging problems will be provided by the instructor. PREREQUISITES: Basic

Ma, Lena

210

Modeling Base Flow Soil Water Residence Times From Deuterium Concentrations  

Microsoft Academic Search

Three approaches to determining mean soil water residence times in a steep headwater catchment were investigated. The deuterium concentrations of soil water collected from 11 suction cup samplers at the Maimai M8 catchment were determined weekly for 14 weeks and the results compared with those of rainfall in the same period. Deuterium variations in the suction samples were considerably delayed

Michael K. Stewart; Jeffrey J. McDonnell

1991-01-01

211

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

212

Dynamic study on water stability of soil structure and soil characteristics of several types of soils in southwest China  

Microsoft Academic Search

Three suborder soils in southwest China were adopted, namely Ustic Vertisol, Stagnic Anthrosol and Ustic Ferrosol, so as to\\u000a carry out the basic physical and chemical analysis respectively, to design a dynamic measuring method for water stability\\u000a of soil structure and conduct the comparative study on the quality of the soil structure. The results indicated that ? The\\u000a water stability

Nan Shen; Yurong He; Xiangming Xu

2008-01-01

213

Soil-root mechanical interactions within bundles of roots  

NASA Astrophysics Data System (ADS)

Root-soil mechanical interactions play an important role in strength and force redistribution in rooted soil. Recent advances in root reinforcement modeling implement detailed representation of root geometry and mechanical properties as well as root-soil mechanical interactions. Nevertheless, root-soil mechanical interactions are often considered at the single root scale ignoring interactions between neighboring roots and root bundles known to play important role in similar applications such as engineered composite material reinforcement. The objective was to quantify mechanical interactions among neighboring roots or roots network using pullout laboratory experiments and modeling. We focus on the on effects of such interactions on global pull out force of a bundle of roots via better understanding of transmission of radial stresses to soil matrix due to the friction at the interface soil-root. Additionally, we wish to predict how cumulative friction changes along a single root axis with and without branching points during the slipping out. Analytical models of fiber reinforced materials show the magnitude of bonded friction depends on three key parameters: bond modulus, maximal bond strength and difference between the Young moduli of fiber and Young moduli of matrix. Debonded friction is calculated assuming failure follows Coulomb failure that includes apparent cohesion, effective normal stress and residual root soil friction angle. We used a pullout device to measure displacement and force of individual roots and for the bundle of roots. Additionally, we monitored and detected activation of root-soil friction by six acoustic emission sensors placed on waveguide in contact with the soil matrix. Results from experiments with parallel and crossing roots demonstrated the importance of considering factors such as distance of root axis, branching points, crossing of roots and roots diameter for the behavior of bundle of roots and inclined roots during pullout. Acoustic emission measurements provided interesting insights into progressive activation of root-soil friction. These results enhance understanding of root reinforcement mechanism and enable more realistic implementation of root reinforcement modeling for stability calculation of vegetated slopes.

Giadrossich, Filippo; Schwarz, Massimiliano; Preti, Federico; Or, Dani

2010-05-01

214

Management practices to improve the use efficiency of nutrients and water in a sandy soil under rice based cropping system  

E-print Network

methods on soil physical properties and water expenses ofimprove soil physical properties such as water holdingphysical properties like bulk density, soil strength, mean weight diameter, micro porosity, water

Bhaskaran, Usha Pankajam Dr.; S, Pushkala. Dr; A.K., Sreelatha Dr; Aparna, B Dr.

2009-01-01

215

The effect of soil:water ratios on the induction of isoproturon, cypermethrin and diazinon mineralisation.  

PubMed

The rate of pesticide biodegradation does not remain constant with time, and is dependent on the physico-chemical properties of the soil and of the pesticide as well as on the biology of the soil. Prolonged or repeated contact between soil microbes and pesticides has been shown to result in an increase in the rate and extent of biodegradation. This work assessed the impact of the soil:water ratio on measurement of catabolic induction for ¹?C-isoproturon, ¹?C-diazinon and ¹?C-cypermethrin. Slurrying (1:1 and 1:3 soil:water) with agitation resulted in significantly higher rates and extents of mineralisation than the non-slurried system (P ? 0.05; 1:0 soil:water), except for the mineralisation of ¹?C-diazinon where the greatest extent of mineralisation occurred in non-slurried soil. Slurrying without agitation resulted in the significant lower mineralisation in all cases (P ? 0.05). There was a significant interaction between the soil:water ratio and length of contact (P ? 0.05). Whilst the use of slurried systems can enhance the extent and rate of mineralisation, there is no improvement in reproducibility, and so for the measurement of catabolic induction, the use of field conditions will lead to a more environmentally relevant measurement. PMID:21047667

Fenlon, Katie A; Jones, Kevin C; Semple, Kirk T

2011-01-01

216

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

E-print Network

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

Fasano, Antonio

217

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

218

The Influence of Soil Type, Soil Water and Share Sharpness of a Mouldboard Plough on Energy Consumption, Rate of Work and Tillage Quality  

Microsoft Academic Search

The results of field tests to investigate the influence of soil type and soil water on the wear of soil tillage tools are presented. The soil water had a positive effect for loam and clay soils because the wear decreased as the water content increased. For sandy soils however, wear increased with soil water. As the thickness of the cutting

A. Natsis; G. Papadakis; J. Pitsilis

1999-01-01

219

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

220

Fractal processes in soil water retention  

Microsoft Academic Search

The authors propose a physical conceptual model for soil texture and pore structure that is based on the concept of fractal geometry. The motivation for a fractal model of soil texture is that some particle size distributions in granular soils have already been shown to display self-similar scaling that is typical of fractal objects. Hence it is reasonable to expect

Scott W. Tyler; Stephen W. Wheatcraft

1990-01-01

221

Coupled Soil-Plant Water Dynamics During Drought-Rewetting Transitions  

NASA Astrophysics Data System (ADS)

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

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

2013-12-01

222

Subcritical water extraction of polychlorinated biphenyls from soil and sediment  

Microsoft Academic Search

Two certified reference materials, an industrial soil (CRM 481) and a river sediment (NIST 1939), were extracted by subcritical water at 50 atm and temperatures ranging from 50 to 300°C. The extraction efficiency of PCBs is extremely dependent on water temperature, since the polarity (dielectric constant) of water can be dramatically lowered by raising the water temperature. While only traces

Yu. Yang; S. Bewadt; Steven B. Hawthorne; David J. Miller

1995-01-01

223

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

NASA Astrophysics Data System (ADS)

Forest fires are recurrent phenomena in the Mediterranean area and are one of the main causes of changes in the Mediterranean ecosystems, increasing the risk of soil erosion and desertification. Fire is an important agent which can induce important changes in the chemical and physical characteristics of soils. During wildfires, only a small part of the heat generated is transmitted to the first centimetres of the soil profile. The intensity of the changes produced in the physical and chemical characteristics of the soil depends on the temperatures reached at different soil depths, the time of residence of temperature peaks, and the stability of the different soil components. One of the soil physical properties strongly affected by fire is soil water repellency (WR). Depending on temperature, time of heating, type of soil and fuel, fire can induce, enhance or destroy soil WR. Soil WR is a key factor in controlling soil hydrology and water availability in burnt soils together with other factors as texture or aggregation. Although the occurrence and consequences of fire-induced soil WR have been deeply studied, some gaps still exist, as the influence of rock fragment cover during burning. During combustion of litter and aerial biomass, the soil surface under rock fragments is heated and reachs temperature peaks after a certain delay respect to exposed areas. In contrast, temperature peaks are longer, increasing the time of residence of high temperature. In consequence, rock fragments may change the expected spatial distribution of soil WR. Up to date, very scarce research concerns the effect of rock fragments at the soil surface on the fire-induced pattern of soil water repellency. METHODS Two experiments were carried out in this research. In the first case, an experiment was conducted in an experimental farm in Sevilla (southern Spain). The effect of a low severity prescribed fire was studied in soil plots under different rock fragment covers (0, 15, 30, 45 and 60%). Soil WR was assessed in soil samples (0-10 cm) collected monthly during 6 monhts after burning. In the second case, a fire-affected forest soil from Calañas (Huelva, southweastern Spain) was studied. Soil plots under different fire severities (low, medium and high severity burning) and rock fragment cover classes (20-40 and 60-80%) were analyzed. Soil WR was assessed in the soil surface immediately under the vertical projection of randomly selected stones and in the middle point between these and the nearest stones. Unburned adjacent soils under similar rock fragment cover classes were used as control. All soil WR assessments were carried out using the WDPT method. RESULTS In both cases, soil WR was induced in the soil surface contacting rock fragments after burning. Severity of WR ranged between subcritical or slight (low severity burning) and strong (high severity burning). Soil WR was also found to increase with rock fragment cover, especially after moderate or high severity burning, both under and between rock fragments. It is suggested that high density of rock fragments on the soil surface create a continuous surface of high residence of temperature peaks (in agreement with García-Moreno et al., 2013). Combustion of plant residues in oxygen depletion conditions between adjacent nearby rock fragments contributes to heat transfer to the soil surface and consequent enhanced soil WR. REFERENCES García-Moreno, J., Gordillo-Rivero, A.J., Gil, J., Jiménez-Morillo, N.T., Mataix-Solera, J., González-Peñaloza, F.A., Granged, A.J.P., Bárcenas-Moreno, G., Jiménez-Pinilla, P., Lozano, E., Jordán, A., Zavala, L.M. 2013. Do stones modify the spatial distribution of fire-induced soil water repellency? Preliminary data. Flamma, 4:76-80.

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

2013-04-01

224

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

NASA Astrophysics Data System (ADS)

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

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

2008-11-01

225

Measurement of coupled soil heat and water processes  

NASA Astrophysics Data System (ADS)

Coupled soil heat and water processes are critical for terrestrial life at all scales. Yet detailed understanding of these processes is limited. Inability to measure fine-scale, transient, one-dimensional (1-D) heat and water redistribution encumbers laboratory and field experiments and restricts testing of theory. The impetus for this work is to strengthen understanding of soil heat and water processes through improved measurement. Objectives were to (1) Develop closed soil cells with 1-D, non-isothermal conditions; (2) Measure soil temperature, water content, and thermal conductivity distributions under transient, 1-D conditions; (3) Test diffusion-based coupled heat and water transfer theory; and 4) Measure in situ soil water evaporation under dynamic field conditions. Soil-insulated, closed soil cells were developed to achieve 1-D conditions. These cells provided a 1:0.02 ratio between intended axial and unintended radial temperature gradients. The cells were instrumented with thermo-TDR sensors to measure transient temperature, water content, and thermal conductivity for two soils (sand and silt loam), two initial moistures, and ten boundary temperature gradients. Thermo-TDR water content measurements provided root mean square error (RMSE) <0.02 m3 m-3 versus gravimetric measurements. Co-located inflection points in temperature, water content, and thermal conductivity distributions indicated heat and water redistribution consistent with coupled transfer. These data were used to calibrate and test transfer theory. Adjustment of calculated vapor and liquid fluxes via the vapor enhancement factor and saturated hydraulic conductivity, respectively, reduced RMSE by an average of 36% for water content and temperature. Predictions from calibrated theory agreed with measurement when boundary and initial conditions changed gradually, but showed more disparity for drastic changes in boundary temperature conditions. In the field, a measurement-based soil heat balance was used to track the transient evaporation zone within the soil. Heat-pulse sensors measured soil temperature and thermal properties under bare surface conditions during multiple natural wetting/drying cycles. The heat-balance approach revealed the diurnal and inter-diurnal pattern of in situ soil water evaporation. Comparison of the heat balance approach to independent evaporation estimates gave RMSE of 0.11 mm d-1. Overall, the experiments demonstrated the utility of improved measurement for describing coupled soil heat and water processes.

Heitman, Joshua L.

226

Impact of interspecific interactions on antimicrobial activity among soil bacteria  

PubMed Central

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

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

2014-01-01

227

Perchlorate levels in soil and waters from the Atacama Desert.  

PubMed

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

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

2014-02-01

228

UF/IFAS Soil and Water Science 2181 McCarty Hall  

E-print Network

Soil and Water Conservation 3 sws 4245 Water Resource Sustainability 3 sws 4307 Ecology of WaterborneContact UF/IFAS Soil and Water Science 2181 McCarty Hall PO Box 110290 Gainesville, FL 32611 Phone: 352.294.3152 E-mail: mjsisk@ufl.edu soils.ifas.ufl.edu soil and water science major SOIL SCIENCE u n d

Jawitz, James W.

229

Measuring Low Concentrations of Liquid Water in Soil  

NASA Technical Reports Server (NTRS)

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

Buehler, Martin

2009-01-01

230

Soil water regime of agricultural field and forest ecosystems  

Microsoft Academic Search

The unsaturated zone of soil is one of the most important and complicated parts considering the water movement in the hydrologic\\u000a cycle. Water transfer through its upper and lower boundary directly influences the amount of water in this zone. The depth\\u000a of groundwater table usually delimits the lower boundary. The soil surface with or without plant canopy is the upper

Vlasta Štekauerová; Viliam Nagy; Dana Kotorová

2006-01-01

231

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

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

232

Dynamic interactions between soil animals and microorganisms in upland grassland soils amended with sheep dung: a microcosm experiment  

Microsoft Academic Search

There is presently much discussion over factors regulating soil microbial processes in grazed grassland ecosystems. We examined the relative importance of dung and soil fauna, and their interactions on microbial biomass and activity in two contrasting upland grassland soils. We found that the presence of nematodes and Collembola was associated with significant (P<0.05) increases in microbial biomass in both soil

R. D. Bardgett; S. Keiller; R. Cook; A. S. Gilburn

1998-01-01

233

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

234

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

NASA Astrophysics Data System (ADS)

Interactions of water molecules with soil organic matter (SOM) may affect the ability of SOM to participate in multiple physical, chemical and biological processes. Specifically, water-SOM interactions may have a profound effect on interactions of organic compounds with SOM which is often considered as a major natural sorbent controlling the environmental fate of organic pollutants in the soil environment. Quantification of water - SOM interactions may be carried out by using water vapor sorption isotherms. However, water sorption isotherms providing macroscopic thermodynamic data do not allow examining water-SOM interactions on a microenvironment scale. The examination of water-SOM interactions in a local SOM environment may be carried out by determining the response of the SOM hydration to sorption of probe organic compounds. Recently, the model-free approach was proposed which allows quantifying effects of sorbing organic molecules on water - SOM interactions, by using relatively more available data on the effect of water activity on organic compound - SOM interactions. Therefore, this thermodynamic approach was applied to the experimental data describing sorption of organic compounds by SOM, both from the vapor and liquid phases, at various water activities. Hence, the response of water interactions with the model SOM materials such as a humic acid and an organic matter-rich peat soil to the presence of various organic sorbates was evaluated. Depending on a molecular structure of organic sorbates probing various molecular environments in SOM, the SOM-bound water may be driven in or out of the SOM sorbents. Organic compounds containing the atoms of oxygen, nitrogen or sulfur and preferring a relatively "polar" SOM microenvironment demonstrate the distinct enhancing effect on water-SOM interactions. In contrast, the "low-polarity" organic compounds, e.g., hydrocarbons or their halogen-substituted derivatives, produce a weakening effect on water-SOM interactions. Importantly, the changes in water-SOM interactions induced by the presence of organic compounds may demonstrate the cooperative behavior: (1) several water molecules may be involved in an enhanced hydration of SOM, (2) at the presence of an organic sorbate, interactions of water molecules with SOM enhance the uptake of the following water molecules. The proposed cooperative water-SOM interactions may result from a perturbation of the SOM matrix due to a sorption of organic and water molecules where a partial disrupting of molecular contacts in SOM makes easier the following SOM-water interactions thus promoting the enhanced SOM hydration.

Borisover, Mikhail

2014-05-01

235

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

E-print Network

1 Running heading: Water retention properties of the clay in clayey soils Water retention. E-mail: ary.bruand@orleans.inra.fr Summary We have investigated the water retention properties retention properties have been studied from -10 hPa to -15 000 hPa water potential using small clods

Paris-Sud XI, Université de

236

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

237

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

238

Water repellent soils as they occur on UK golf greens  

NASA Astrophysics Data System (ADS)

Water repellent soils have been identified as a major problem in the management of golf greens in the UK for over 60 years. The cause of this problem has provoked much speculation, but prior to this work, no research into the possible cause of water repellent soils in the UK had been completed. One of the commonly believed links with water repellent soils on UK golf greens was the activity of basidiomycete fungi. This was proposed as a possible causal factor because the symptoms expressed on the turf above affected soils, were similar in many instances to those symptoms expressed by the activity of superficial fairy rings. Since it was impractical to study superficial fairy rings, it was decided to observe other basidiomycete fairy rings (Type 1 fairy rings) to see if any water-repellence could be identified as being associated with them. Three of these rings, caused by the fungus Marasmius oreades (Bolt ex. Fr) Fr., were studied on each of the two different sites. Soil samples were removed at intervals from the centre of the rings, across the obvious symptoms of the rings (i.e. the zone of dead grass bordered on both sides by a zone of stimulated grass growth) and beyond, into the uncolonised soil. These samples were taken to the laboratory, allowed to air dry and were then tested to determine relative levels of water repellence. It was found that on the 'outside' of the fairy rings where the fungus had not yet colonised, the soils were less water repellent than they were in the other zones of the rings (i.e. the dead zone and the inner zone). In the region of the dead zone of these fairy rings, the soil was very water repellent. This may have been expected because the fungus was present in this area in large quantities and the fungus itself repels water. However, of particular interest, were the results from the inner part of the ring where the fungus had been present in the past, but where it no longer colonised the soil. In these soil samples, the rootzone soil was still very water repellent. It was concluded from the study that it was possible for basidiomycete-type fungi to effect water repellence on soils through which they have passed. Thus, this may be at least a contributory factor to the development of severely water repellent soils on UK golf greens.

York, C. A.; Canaway, P. M.

2000-05-01

239

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

Microsoft Academic Search

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

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

2002-01-01

240

A conceptual model of the soil water retention curve  

NASA Astrophysics Data System (ADS)

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 the water retention curve. This expression presents two fitting parameters only. The proposed model is tested on water retention data sets of 12 soils representing a wide range of soil textures, from sand to clay. The agreement between the fitted curves and the measured data is very good. The performances of the model are also compared with those of the two-parameter models of van Genuchten [1980] and Russo [1988] for the water retention function. In general, the proposed model exhibits increased flexibility and improves the fit at both the high and the low water contents range.

Assouline, S.; Tessier, D.; Bruand, A.

1998-02-01

241

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

242

Protein-water interactions and functional properties  

Microsoft Academic Search

Hydration or rehydration is the first and perhaps most critical step in imparting desired functional properties to proteins\\u000a in a food system. Water that interacts with the protein molecule exhibits different properties from those of “free” water.\\u000a The types of water in protein-food systems are described in terms of structural, monolayers, unfreezable, hydrophobic hydration,\\u000a imbibition or capillary condensation, and hydrodynamic

David H. Chou; Charles V. Morr

1979-01-01

243

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

Microsoft Academic Search

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

J. H. Richards; M. M. Caldwell

1987-01-01

244

Flux-gradient relationships and soil-water diffusivity from curves of water content versus time  

Microsoft Academic Search

Direct analysis of a family of curves of soil-water content vs. time at different fixed positions enables assessment of the flux-gradient relationship prior to the calculations of soil-water diffusivity. The method is evaluated on both smooth and random-error data generated from the solution of the horizontal soil-water intake problem with a known diffusivity function. Interpolation, differentiation, and intergration are carried

D. L. Nofziger; L. R. Ahuja; D. Swartzendruber

2009-01-01

245

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

246

Impact of soil and groundwater heterogeneity on surface water chemistry in an upland catchment  

NASA Astrophysics Data System (ADS)

The interaction of precipitation with catchment soils is commonly assumed to be the dominant control on the composition and quality of the resulting surface waters. A hydrochemical investigation of a small granitic upland catchment (NE Scotland) was undertaken to study the link between the spatial distribution of soils and the heterogeneity of surface water chemistry. The approach involved division of the study area into subcatchments with a spatial range of 4-124 ha. Mean concentrations of stream water solutes showed considerable spatial variability across the catchment. Although links existed between surface water hydrochemistry and soil distribution, the dominant soil types on an area basis did not necessarily control subcatchment hydrochemistry. Solute fluxes showed more pronounced heterogeneity than that reflected by concentrations alone. Groundwater inputs to streams were implicated from calculations of water budgets and were characterised by elevated geochemical solute concentrations; this enhanced the hydrochemical heterogeneity attributed to surface soil drainage and hence highlighted the complexities of subsurface flow pathways. One small tributary lower in the catchment (3% of the total area) from a groundwater-dominated source was influential in controlling the overall outflow chemistry from the whole catchment. Generally, whilst hydrochemical modelling often considers such catchments as homogeneous units, advances in understanding the hydrochemical functioning of catchments will only be made when the full range of catchment water source compositions is accounted for. Such heterogeneity makes it difficult for management decisions based on spatially averaged data to adequately predict and protect against degradation in water quality.

Stutter, M. I.; Deeks, L. K.; Low, D.; Billett, M. F.

2006-03-01

247

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

248

Volatile-mediated interactions between phylogenetically different soil bacteria  

PubMed Central

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

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

2014-01-01

249

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

NASA Astrophysics Data System (ADS)

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

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

2013-02-01

250

Exponential increase of publications related to soil water repellency  

Microsoft Academic Search

Soil water repellency is much more wide-spread than formerly thought. During the last decades, it has been a topic of study for soil scientists and hydrologists in at least 21 States of the USA, in Canada, Australia, New Zealand, Mexico, Colombia, Chile, Congo, Nepal, India, Hong Kong, Taiwan, China, Ecuador, Venezuela, Brazil, Mali, Japan, Israel, Turkey, Egypt, South Africa, Germany,

Louis W. Dekker; Klaas Oostindie; Coen J. Ritsema

2005-01-01

251

Predicting Soil-Water Partition Coefficients for Cadmium  

E-print Network

Predicting Soil-Water Partition Coefficients for Cadmium S U E N - Z O N E L E E Department and chemical composition, particularly organic matter and metal oxides. The adsorption of Cd(II) followed concentration, greater adsorption was observed for soils with higher organic matter content. To better

Sparks, Donald L.

252

Demetalisation of soils by continuous acidified subcritical water extraction  

Microsoft Academic Search

Acidified subcritical water is proposed for the continuous extraction of metals (namely, lead, copper, cadmium, arsenic, selenium and mercury) from soils prior to: (a) continuous derivatisation (by hydride formation for As and Se, and cold vapour formation for Hg) and determination by atomic fluorescence; and (b) determination by Graphite Furnace-Atomic Absorption Spectrometry for Pb, Cu and Cd. Soil samples (5

E Priego-López; M. D Luque de Castro

2002-01-01

253

Remediation of soil contaminated with dioxins by subcritical water extraction  

Microsoft Academic Search

The effectiveness of subcritical water extraction (SCWE) was examined for removing dioxins from contaminated soil. Most dioxins in the soil sample were reduced at 300 °C or more, but decreased dioxin concentrations were also observed at 150 °C. After 4 h of extraction, 99.4%, 94.5% and 60% of PCDDs were removed from samples at 350, 300 and 150 °C, respectively.

Shunji Hashimoto; Kiyohiko Watanabe; Kazutoshi Nose; Masatoshi Morita

2004-01-01

254

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

255

University of Florida Soil and Water Science Department  

E-print Network

health Describe processes of site evaluation, risk assessment, data reporting, and public communication that enable preliminary estimates of how various contaminants may move, react, and dissipate in dynamic soil Explain how risk evaluations develop into standards Describe soil, water, and public health topics from

Ma, Lena

256

Soil science Disinfection of drain water in greenhouses  

E-print Network

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

Paris-Sud XI, Université de

257

Original article Scaling xylem sap flux and soil water  

E-print Network

transpiration, we quantified water flux in a forest using three approaches: 1) measuring water flux in xylem of trees, and scaling to stand transpiration of canopy trees (EC); 2) measuring soil water content, differences between the patterns indicate that patchiness in branch transpiration may pre- clude using branch

Boyer, Edmond

258

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

259

Agri-environmental policy in Germany: soil and water conservation  

Microsoft Academic Search

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

Peter Weingarten

1997-01-01

260

Surfactant-enhanced remediation of organic contaminated soil and water  

Microsoft Academic Search

Surfactant based remediation technologies for organic contaminated soil and water (groundwater or surface water) is of increasing importance recently. Surfactants are used to dramatically expedite the process, which in turn, may reduce the treatment time of a site compared to use of water alone. In fact, among the various available remediation technologies for organic contaminated sites, surfactant based process is

Santanu Paria

2008-01-01

261

Soil and Vegetation Management: Keys to Water Conservation on Rangeland  

E-print Network

The amount of water that soaks into the soil largely determines plant productivity. We can manage and conserve water where and when it falls, and by controlling the kind of vegetation we can make the fullest use of rain water. This publication...

Schuster, Joseph L.

2001-01-11

262

Plant species, atmospheric CO 2 and soil N interactively or additively control C allocation within plant-soil systems  

Microsoft Academic Search

Two plant species, Medicago truncatula (legume) and Avena sativa (non-legume), were grown in low-or high-N soils under two CO2 concentrations to test the hypothesis whether C allocation within plant-soil system is interactively or additively controlled\\u000a by soil N and atmospheric CO2 is dependent upon plant species. The results showed the interaction between plant species and soil N had a significant

Shenglei Fu; Ferris Howard

2006-01-01

263

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

264

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

265

University of Florida Soil and Water Science Department  

E-print Network

Control Week 45 Monitoring Surface Water Sampling objectives Sampling methods Sampling equipment and well configuration Sampling methods Sampling equipment Purging and Stabilization Criteria Week 6 Soil and Vadose Characterization Sampling objectives Sampling methods Sampling equipment Field

Jawitz, James W.

266

Microbial interaction networks in soil and in silico  

NASA Astrophysics Data System (ADS)

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

Vetsigian, Kalin

2012-02-01

267

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

E-print Network

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

Rubin, Yoram

268

Rise in CO 2 affects soil water transport through repellency  

Microsoft Academic Search

Several studies have shown improved soil stability under elevated atmospheric CO2 caused by increased plant and microbial biomass. These studies have not quantified the mechanisms responsible for soil stabilisation\\u000a or the effect on water relations. The objective of this study was to assess changes in water repellency under elevated CO2. We hypothesised that increased plant biomass will drive an increase

Dennis C. Gordon; Paul D. Hallett

2009-01-01

269

Field scale soil characterization using pedostructural properties  

Microsoft Academic Search

Accurate soil characterization is crucial for understanding soil-water interactions and allow for better on-farm agricultural and environmental management. Current soil characterization methods lack quantitative attributes that integrate the soil mapping units with environmental and agronomical models. In this research we propose a methodology to physically characterize the soil water medium using quantitative parameters. We incorporated the continuously measured soil water

Mohammed Ali Salahat

2006-01-01

270

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

271

Human interactions with ground-water  

USGS Publications Warehouse

Ground-Water could be considered as an immense reservoir, from which only a certain amount of water can be withdrawn without affecting the quantity and quality of water. This amount is determined by the characteristics of the environment in which ground-water occurs and by the interactions of ground-water with precipitation, surface water, and people. It should be recognized that quantity and quality of ground-water are intimately related and should be considered accordingly. Quantity refers to usable water and water is usable for any specific purpose only so long as its quality has not deteriorated beyond acceptable limits. Thus an overall quantitative and qualitative management of ground water is inevitable, and its should also involve the uses of ground-water reservoirs for purposes other than water supply. The main objective of ground-water management is to ensure that ground-water resources will be available in appropriate time and in appropriate quantity and quality to meet the most important demands of our society. Traditional, and obvious uses of ground-water are the extraction of water for water supplies (domestic, municipal, agricultural, and industrial) and the natural discharge feeding lakes and maintaining base flow of streams. Not so obvious are the uses of ground-water reservoirs, the very framework within which ground-water occurs and moves, and in which other fluids or materials can be stored. In the last two decades, ground-water reservoirs have been intensively considered for many other purposes than water supplies. Diversified and very often conflicting uses need to be evaluated and dealt with in the most efficient way in order to determine the importance of each possible use, and to assign priorities of these uses. With rising competition for the use of ground-water reservoirs, we will also need to increase the potential for effective planning of ground-water development and protection. Man's development and use of ground-water necessarily modifies the natural conditions and the total natural system must be successfully blended with the unnatural stresses placed upon it. This can be accomplished by introducing new methods (such as ground-water zoning) in and by developing alternative strategies for ground-water management and protection. ?? 1983 D. Reidel Publishing Company.

Zaporozec, A.

1983-01-01

272

Contamination of soil, soil gas, and ground water by hydrocarbon compounds near Greear, Morgan County, Kentucky. Water resources investigation  

Microsoft Academic Search

The purpose of the report is to present the results of an investigation of hydrocarbon contamination near Greear, KY. Specifically, the report describes the areal extent and migration of the hydrocarbon contamination in the soil, soil gas, and ground water in the study area. The report also includes a description of the hydrogeologic framework of the Greear area. The application

A. G. Alexander; D. D. Zettwoch; M. D. Unthank; R. B. Burns

1993-01-01

273

Capillary rise in partially water repellent soils - measurements and modeling  

NASA Astrophysics Data System (ADS)

In water repellent soils water transport processes are different from transport processes in non repellent soils. In most soils the extent of water repellency, expressed by the contact angle between fluid and solid phase, is not static but changes with time (e.g. due to fluid flow velocity). One method to precisely determine the contact angle is the capillary rise method using water and additionally a liquid with a contact angle close to zero (e.g. ethanol). Usually this method is used to determine static contact angles, by fitting the original or a simplified version of the Washburn equation to the measured data. The classical Washburn theory assumes a constant contact angle between the solid phase and the liquid. In this work we test different modification of the Washburn equation accounting for dynamic change of contact angles. Several capillary rise experiments with soils of different water repellency with water and ethanol were carried out. The inflow of water and the water contents in eight different heights within the soil columns were detected with high temporal resolution. The original Washburn equation and different modifications are fitted to the data. Since different model formulation may have different numbers of free adjustable parameters an information criterion like the AIC is applied to find the best model.

Lacour, Jan; Peters, Andre; Schonsky, Horst; Wessolek, Gerd

2013-04-01

274

Effect of soil water repellency on soil hydraulic properties estimated under dynamic conditions  

NASA Astrophysics Data System (ADS)

SummarySoil research done over the past decades has proven that water repellent soils are widespread in all climates. Water repellency enhances the leaching of contaminants in the unsaturated zone by introducing preferential flow. In order to predict soil water fluxes in the unsaturated zone the accurate knowledge of the soil hydraulic properties (SHP) is mandatory. In this study the effect of water repellency on both imbibition and drainage SHP was studied. Inflow/outflow experiments were conducted in the laboratory for two soils and two artificially created hydrophobic mixtures. In the inflow/outflow experiments the pressure head at the bottom of the soil column was increased/decreased and the estimated SHP functions were obtained by means of inverse modeling. Inflow/outflow experiments were also conducted using ethanol instead of water in order to estimate the effect of liquid wetting properties on the estimated characteristic curves of the materials under study. The results showed that the water retention functions and the unsaturated hydraulic conductivity functions estimated from the dynamic experiments are strongly dependent on the degree of water repellency and the wetting/drying process.

Diamantopoulos, E.; Durner, W.; Reszkowska, A.; Bachmann, J.

2013-04-01

275

Soil Moisture and Vegetation Water Content Retrieval Using QuikSCAT data  

NASA Astrophysics Data System (ADS)

Future water resources are a critical societal impact of climate change and hydrological cycles. Current climate models uncertainties result in disagreement on whether there will be more or less water. On a global scale, there are important gaps in knowledge of where water is stored, where it is going, and how fast it is moving. Soil moisture and vegetation water content are key environmental variables on evaporation and transpiration at the land-atmosphere boundary. Radar remote sensing helps to improve our estimate of water resources globally and temporally. SMAP (Soil Moisture Active Passive) and SWOT (Surface Water Ocean Topography) are the two future NASA missions to monitor water resources and their variation spatially and temporally. Li et al. (Li. Et al. 2010) developed a physically based six-channel algorithm, which uses dual-polarization Windsat passive microwave data to retrieve soil moisture and vegetation water content. We use the retrieved soil moisture and vegetation water content using Windsat descending pass (around 6AM), and also simultaneous collocated QuikSCAT dual-polarization backscattered power to estimate different parameters of the land. The backscattered power can be written as ?pi = fbare ?grp(smi,m) + (1-fbare){ Ap ( 1-exp(-Bp Wi) ) + Cp Wi? exp(-Bp Wi) } where ?pi is the ith QuikSCAT backscatter power with polarization p, fbare is the bare surface fraction, m is soil rms. slope, ?grp is the ground backscattered power with polarization p, and smi and Wi are the retrieved soil moisture and vegetation water content using Windsat data. Ap, Cp, and Bp are the backscattering contributions from vegetation volume, canopy ground interaction, and attenuation of the canopy with polarization p, respectively. We assume all parameters remain constant for each month of different years compared to soil moisture and vegetation water content. Therefore for each point, we have 10 unknowns for HH and VV polarizations. We collect all observations of simultaneous QuikSCAT and retrieved smi and Wi for each location during the summer season and retrieve all those 10 parameters. We show how the retrieved global bare surface fraction compares well with the existing maps. These parameters are then used to estimate the soil moisture and vegetation water content for summer days of a different year using QuikSCAT backscattered power and formula above. Although QuikSCAT satellite is designed to capture sea-winds, it also collects data over land globally almost every day. Therefore, we can generate a global map of soil moisture and vegetation water content daily. We compare the retrieved values with Li et al.'s retrieval values.

Oveisgharan, S.; Haddad, Z. S.; Turk, J.; Li, L.; Rodriguez, E.

2013-05-01

276

Hydraulic redistribution of soil water by neotropical savanna trees.  

PubMed

The magnitude and direction of water transport by the roots of eight dominant Brazilian savanna (Cerrado) woody species were determined with a heat pulse system that allowed bidirectional measurements of sap flow. The patterns of sap flow observed during the dry season in species with dimorphic root systems were consistent with the occurrence of hydraulic redistribution of soil water, the movement of water from moist to drier regions of the soil profile via plant roots. In these species, shallow roots exhibited positive sap flow (from the soil into the plant) during the day and negative sap flow (from the plant into the soil) during the night. Sap flow in the taproots was positive throughout the 24-h period. Diel fluctuations in soil water potential, with maximum values occurring at night, provided evidence for partial rewetting of upper soil layers by water released from shallow roots. In other species, shallow roots exhibited negative sap flow during both the day and night, indicating that hydraulic redistribution was occurring continuously. A third sap flow pattern was observed at the end of the dry season after a heavy rainfall event when sap flow became negative in the taproot, and positive in the small roots, indicating movement of water from upper soil layers into shallow roots, and then into taproots and deeper soil layers. Experimental manipulations employed to evaluate the response of hydraulic redistribution to changes in plant and environmental conditions included watering the soil surface above shallow roots, decreasing transpiration by covering the plant and cutting roots where probes were inserted. Natural and manipulated patterns of sap flow in roots and stems were consistent with passive movement of water toward competing sinks in the soil and plant. Because dry shallow soil layers were often a stronger sink than the shoot, we suggest that the presence of a dimorphic root system in deciduous species may play a role in facilitating leaf expansion near the end of the dry season when the soil surrounding shallow lateral roots is still dry. PMID:12069916

Scholz, Fabian G; Bucci, Sandra J; Goldstein, Guillermo; Meinzer, Frederick C; Franco, Augusto C

2002-06-01

277

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

278

A new Approach to Soil Water Retention (Drying Branch)  

NASA Astrophysics Data System (ADS)

Available models of soil water retention for both swelling and non-swelling cases with all essential differences between them are, in part or totally, based on curve-fitting to relevant experimental soil water retention data. The models use either parameters of a pore-size distribution in the fitting or parameters of some mathematical approximation (different for different models) of a retention curve. At least a part of the parameters have no clear physical meaning and can only be found by fitting. As a consequence, although the models can be of practical use for engineering applications, their possibilities from the viewpoint of advancement in the physical understanding and knowledge of the links between inter- and intra-aggregate soil structure and soil water retention as a function of the structure, are, even in the best case, limited. Recently the possibility of the physical prediction of another key soil characteristic - the shrinkage curve - was shown (Chertkov, 2007a, b, 2008a, b). These works permit one to explain soil shrinkage from inter- and intra-aggregate soil structures and without fitting (after many years of the domination of curve-fitting approaches). The results of these works strengthen the certainty that the physical prediction of soil characteristics is not hopeless, but just a difficult problem. The objective of this work is to slightly "dilute" the curve-fitting domination and to suggest some physical alternative as applied to the consideration of soil water retention (drying branch) in the general case, i.e., for swell-shrink soils. The attempt to be proposed relies on the concepts and results of recent works devoted to pure clay water retention (Chertkov, 2004) and soil shrinkage (Chertkov, 2007a, b, 2008a, b). The physical model to be presented includes three parts. We consider: (i) how in the general case a soil water retention curve can be presented through water retention curves of a contributive clay, an intra-aggregate matrix, and a system of internally saturated aggregates; (ii) essential improvement of the available clay water retention model (Chertkov, 2004); and (iii) water retention of a rigid matrix that can consist of sand grains or rigid water saturated aggregates. Then, using the model, we analyze available data to substantiate it. Chertkov V.Y. 2004. A physically based model for the water retention curve of clay pastes. Journal of Hydrology. 286, 203-226. Chertkov V.Y. 2007a. The reference shrinkage curve at higher than critical soil clay content. Soil Sci. Soc. Am. J. 71(3), 641-655. Chertkov V.Y. 2007b. The soil reference shrinkage curve. Open Hydrology Journal. 1, 1-18. Chertkov V.Y. 2008a. Estimating the aggregate/intraaggregate mass ratio of a shrinking soil. Open Hydrology Journal. 2, 7-14. Chertkov V.Y. 2008b. The physical effects of an intra-aggregate structure on soil shrinkage. Geoderma. 146, 147-156.

Chertkov, V. Y.

2008-12-01

279

Sustainable Rangelands Roundtable Indicators I. Conservation and Maintenance of Soil and Water Resources on Rangelands  

E-print Network

Sustainable Rangelands Roundtable Indicators I. Conservation and Maintenance of Soil and Water with accelerated soil erosion by water or wind. Water-based Indicators 6. Percent of water bodies in rangeland Resources on Rangelands Soil-based Indicators 1. Area and percent of rangeland soils with significantly

Wyoming, University of

280

Modelling interactions between soil evolution and diffusive surface processes  

NASA Astrophysics Data System (ADS)

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

Kirkby, Mike; Johnson, Michelle; Gloor, Emanual

2014-05-01

281

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

282

Occurrence and origin of mutagenicity in soil and water environment.  

PubMed

Surface soil and surface water are repositories of chemicals released into the environment, and contaminations of surface soil and river water with mutagens were first reported in the 1970s. However, the identity of major mutagens in surface soil and river water remained unclear for more than two decades. Recently, we have identified some nitrated polycyclic aromatic hydrocarbons (nitro-PAHs), e.g., dinitropyrene isomers and 3-nitrobenzanthrone, as major mutagens in the organic extracts of surface soil that showed strong mutagenicities toward Salmonella typhimurium TA98 in the absence of a mammalian metabolic system (S9 mix), using a bioassay-directed fractionation method. Moreover, we identified new potent mutagens from substances adsorbed on a blue cotton (blue rayon) from river water samples, which showed strong mutagenicity toward S.typhimurium YG1024 with or without the S9 mix. One group was the phenylbenzotriazole (PBTA)-type mutagens, which were detected in river water samples collected at sites below textile dyeing factories. The other group has a dichlorobiphenyl skeleton, i.e., 4-amino-3,3'-dichloro-5,4'-dinitrobiphenyl, and was isolated from a river water sample contaminated with effluent from chemical plants treating polymers and dye intermediates. Some of the nitro-PAHs detected in surface soil, such as PBTA-type mutagens, and 4-amino-3,3'-dichloro-5,4'-dinitrobiphenyl are novel compounds. Up to approximately 50% of the total mutagenicity of extracts from surface soils and river waters was accounted for by nitro-PAHs, PBTA-type mutagens, or 4-amino-3,3'-dichloro-5,4'-dinitrobiphenyl. However, major mutagens in most types of surface soil and river water with high mutagenicity remain unknown. Because environmental mutagens may play some role in the development of diseases such as cancer, their identification is an important step for understanding the risks to indigenous biota and human health. Further effort to identify these major mutagens must be made. PMID:16609672

Watanabe, Tetsushi; Ohe, Takeshi; Hirayama, Teruhisa

2005-01-01

283

Modelling water flow and seasonal soil moisture dynamics in an alluvial groundwater-fed wetland Hydrology and Earth System Sciences, 7(1), 5766 (2003) EGU  

E-print Network

Modelling water flow and seasonal soil moisture dynamics in an alluvial groundwater-fed wetland 57 variations in soil moisture are reproduced well by the model thus translating external hydrological boundary). These studies were concerned mainly with floodplain-channel interactions and, although soil moisture

Paris-Sud XI, Université de

284

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

285

Remediation of soil contaminated with dioxins by subcritical water extraction.  

PubMed

The effectiveness of subcritical water extraction (SCWE) was examined for removing dioxins from contaminated soil. Most dioxins in the soil sample were reduced at 300 degrees C or more, but decreased dioxin concentrations were also observed at 150 degrees C. After 4 h of extraction, 99.4%, 94.5% and 60% of PCDDs were removed from samples at 350, 300 and 150 degrees C, respectively. It was also determined that degradation of dioxins had occurred, since the sum of dioxins in the soil plus water extracts after the experiments had considerably decreased. This study revealed that pressurizing is not essential for the removal of dioxins. Reduction was complete within 30 min at 350 degrees C; however, it took a much longer time at lower temperatures. The results of addition experiments in which OCDDs were added to different types of soil samples have shown that dechlorination is one of the major reaction pathways. After addition of OCDD to soil samples, experiments were carried out to examine in detail the degradation pathways of PCDDs. The removal rates and congener profiles varied among soil types. Although it was previously assumed that removal rates and congener profiles depended on the chemical components in soil, nonparametric statistical analysis revealed no significant relationship between the rate of reduction and elements present in the soil. It was confirmed from isomer patterns that dechlorination of the 2,3,7,8-positions in PCDDs takes place somewhat faster than for the 1,4,6,9-positions. PMID:14559261

Hashimoto, Shunji; Watanabe, Kiyohiko; Nose, Kazutoshi; Morita, Masatoshi

2004-01-01

286

Impact of hydroclimatic fluctuations on the soil water balance  

NASA Astrophysics Data System (ADS)

We analyze the propagation of daily fluctuations in rainfall and potential evapotranspiration to soil moisture dynamics, using a stochastic model that accounts for these two different forms of hydroclimatic variability. The pulsing, intermittent behavior of daily precipitation is described by a compound Poisson process that models the unpredictability of both frequency and amount of rainfall events, while fluctuations in potential evapotranspiration that act continuously in time are assumed to be Gaussian. The resulting model for the soil water balance is thus a stochastic differential equation, forced by a state-dependent compound Poisson noise and a multiplicative Gaussian noise. Steady state probability distribution functions (pdfs) of soil moisture are obtained analytically along with the equations for the expected water balance and its variability. The multiplicative effect of temporal fluctuations in potential evapotranspiration on soil moisture reduces the soil water losses caused by evapotranspiration compared to the case when they are not present. Most importantly, the analysis also shows that because of their different forms and state dependence the impact of rainfall variability on soil moisture dynamics is much more significant than that of potential evapotranspiration, the fluctuations of which do not affect appreciably the soil moisture statistical properties.

Daly, E.; Porporato, A.

2006-06-01

287

Does pre-dawn water potential reflect conditions of equilibrium in plant and soil water status?  

NASA Astrophysics Data System (ADS)

Variation in base water potential ( ?b, a daily maximum level of plant water potential, which is presumed to correspond to the equilibrium between soil and plant water potentials) was examined in shoots of Picea abies and Vaccinium myrtillus with respect to soil (available water storage, water potential, temperature) and atmospheric (temperature, relative humidity, vapour pressure deficit) conditions. The available soil water storage (W tr) accounted for 77% of the dynamics of ?b, while the influence of atmospheric factors became evident under high evaporative demand. ?b was not always observable immediately before dawn, but on 30% of observation days, the recovery continued up to an hour or two after dawn. Full equilibrium between soil and plant water potentials in P. abies in northern conditions is rather improbable by dawn in summer-time, because of the shortness of the dark period and probable night-time transpiration in the case of high atmospheric vapour pressure deficit.

Sellin, Arne

1999-02-01

288

Water extraction as a soil?testing procedure for phosphate  

Microsoft Academic Search

A water?extraction procedure which is specific for a pool of P defined by a sorption model based on the Langmuir equation was evaluated in a glasshouse experiment using perennial ryegrass grown in three contrasting soils. For each of three harvests, water?extractable P values determined at the beginning of each period of growth gave a very much better relationship with dry

P. C. Luscombe; J. K. Syers; P. E. H. Gregg

1979-01-01

289

Applicability of CS616 Soil Water Sensors for South  

E-print Network

Reflectometry High dielectric constant (r)of water. r ­ measure of molecules tendency to orient: Determine if CS616 soil water sensors are functioning adequately at field site. Hypothesis: Presence of air (Gong 2003). Comparison study at TREC ­ TDR sensors more accurate than dielectric and gypsum block

Migliaccio, Kati White

290

Earthworms, water infiltration and soil stability: Some new assessments  

Microsoft Academic Search

Water infiltration (by limiting surface water run-off) and stable crumb formation (by increasing top infiltration and decreasing slaking) are two key soil factors greatly affected by earthworms. Because of the great number of environmental variables controlling (1) earthworm populations; (2) their physical rôle behaviour; (3) their feeding behaviour inducing faeces composition; and (4) the microbial activity stabilizing faeces to crumbs,

Marcel B. Bouché; Fathel Al-Addan

1997-01-01

291

NEWLY DEVELOPED TECHNOLOGIES FOR SOIL AND WATER CONSERVATION  

Microsoft Academic Search

Recent discoveries and technological innovations in the field of soil and water conservation can be traced to the works of our predecessors. In this paper, conservation is defined broadly, to include the quality of water lower in watersheds, and is discussed according to contaminants. Within-field source prevention and reduction practices as well as off-site mitigation practices are described. Examples concerning

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

292

Theoretical characterization of water-surfaces interactions  

NASA Astrophysics Data System (ADS)

Much effort is being devoted to the understanding of water-substrate interactions at metallic or semiconducting surfaces with catalytic properties. Confined water represents a great interest for physicists and chemists interested in state-of-the-art technologies such as, fuel cells where the rates of proton have to be controlled, nano-sensors, heterogeneous catalysis, or nano-fluids. Creation of hydrogen gas from water dissociation, also remains an important challenge in order to complete the cycle of CO2 free green energies production. Photocatalytic processes, with semiconducting substrates such as GaN 101&barbelow;0 seem to represent strong candidates towards this achievement. This work focuses on the investigation of water-substrate interactions. It is mainly directed from first-principle calculations with molecular dynamics simulations. The nature of the hydrogen bond is broadly discussed and comparisons between water-water and water-substrate are proposed. Interesting features of spontaneous metal polarization are also put in evidence and electrochemical mechanisms are explained.

Poissier, Adrien

293

Groundwater and Surface Water: Understanding the Interaction  

NSDL National Science Digital Library

This site provides an introduction to groundwater-surface water interactions and how groundwater can be affected by land use. The page describes threats to groundwater, common contaminants, sources of contamination, and groundwater management approaches and tools. A short glossary and a groundwater quiz are also included.

Phillips, Nancy; Center, Conservation T.

294

Elevated atmospheric CO2 and soil N fertility effects on growth, mycorrhizal colonization, and xylem water potential of juvenile ponderosa pine in a field soil  

Microsoft Academic Search

Interactive effects of atmospheric CO2 enrichment and soil N fertility on above- and below-ground development and water relations of juvenile ponderosa pine (Pinus ponderosa Dougl. ex Laws.) were examined. Open-top field chambers permitted creation of atmospheres with 700 µL L-1, 525 µL L-1, or ambient CO2 concentrations. Seedlings were reared from seed in field soil with a total N concentration

R. F. Walker; D. R. Geisinger; D. W. Johnson; J. T. Ball

1997-01-01

295

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

296

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 ...

297

Water-depth dependent infiltration into burnt forest soils  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

298

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

299

Collimated neutron probe for soil water content measurements  

USGS Publications Warehouse

A collimated neutron probe was designed to enable mesurements in specific directions from the access tube. To determine the size and shape of soil volume affecting the neutron counts, experiments were conducted to evaluate: 1) the vertical distance of soil above and below the probe that influences neutron counts; 2) the horizontal distance away from the probe into the soil that influences neutron counts; 3) the angle of soil viewed by the probe from the collimator; and 4) the three-dimensional thermal-neutron density field. The vertical distance was ~0.5m, the horizontal distance was ~0.2m, and the angle of soil viewed by the probe from the collimator was ~120??. Thermal neutrons detected from distances or angles larger than these values influence the determination of relative water content by 5% or less. -from Authors

Klenke, J.M.; Flint, A.L.

1991-01-01

300

Soil-Water Characteristic Curves of Red Clay treated by Ionic Soil Stabilizer  

NASA Astrophysics Data System (ADS)

The relationship of red clay particle with water is an important factor to produce geological disaster and environmental damage. In order to reduce the role of adsorbed water of red clay in WuHan, Ionic Soil Stabilizer (ISS) was used to treat the red clay. Soil Moisture Equipment made in U.S.A was used to measure soil-water characteristic curve of red clay both in natural and stabilized conditions in the suction range of 0-500kPa. The SWCC results were used to interpret the red clay behavior due to stabilizer treatment. In addition, relationship were compared between the basic soil and stabilizer properties such as water content, dry density, liquid limit, plastic limit, moisture absorption rate and stabilizer dosages. The analysis showed that the particle density and specific surface area increase, the dehydration rate slows and the thickness of water film thins after treatment with Ionic Soil Stabilizer. After treatment with the ISS, the geological disasters caused by the adsorbed water of red clay can be effectively inhibited.

Cui, D.; Xiang, W.

2009-12-01

301

Observations of flow path interactions with surface structures during initial soil development stage using irrigation experiments  

NASA Astrophysics Data System (ADS)

Structures and processes are dynamically linked especially during initial stages of soil and ecosystem development. Here we assume that soil pore structures and micro topography determine the flow paths and water fluxes as well as further structure changes. Reports about flow path developments at the soil surface are still limited because of an insufficient knowledge of the changing micro topography at the surface. The objective of this presentation is to evaluate methods for parameterisation of surface micro topography for analysing interactions between infiltration and surface runoff. Complex irrigation experiments were carried out at an experimental site in the neighbourhood of the artificially created water catchment "Chicken Creek". The irrigation rates between 160 mm/h and 250 mm/h were held constant over a time period of 20 minutes. The incoming intensities were measured as well as the raindrop-velocity and -size distributions. The surface runoff was continuously registered, soil samples were taken, and soil water potential heads were monitored using tensiometers. Surface and subsurface flow paths were identified using different tracers. The soil surface structures were recorded using a high resolution digital camera before, during, and after irrigation. Micro topography was surveyed using close-range photogrammetry. With this experimental design both, flow paths on the surface and in the soil as well as structure and texture changes could be observed simultaneously. In 2D vertical cross-sections, the effect of initial sediment deposition structure on infiltration and runoff was observed. Image analysis of surface pictures allowed identifying structural and soil textural changes during the runoff process. Similar structural changes related to surface flow paths were found with the photogrammetric surface analysis. We found evidence for the importance of the initial structures on the flow paths as well as a significant influence of the system development. Flow paths tended to orient along initial structures and changes during the early stages of development. The amount of runoff increased from about 20% of irrigation on the first stage to 50% for the same plot one year later. The data will be used in 2D and 3D numerical simulations of the observed surface and soil water fluxes.

Bartl, Steffen; Biemelt, Detlef; Badorreck, Annika; Gerke, Horst H.

2010-05-01

302

Visualizing Clogging up of Soil Pores in the Tropical Degraded Soils and Their Impact on Green Water Productivity  

NASA Astrophysics Data System (ADS)

Abstract Restrictive soil layers commonly known as hardpans restrict water and airflow in the soil profile and impede plant root growth below the plow depth. Preventing hardpans to form or ameliorate existing hardpans will allow plants root more deeply, increase water infiltration and reduce runoff, all resulting in greater amounts of water available for the crop (i.e. green water). However, there has been a lack of research on understanding the influence of transported disturbed soil particles (colloids) from the surface to the subsurface to form restrictive soil layers, which is a common occurrence in degraded soils. In this study we investigated the effect of disturbed soil particles on clogging up of soil pores to form hardpans. Unsaturated sand column experiments were performed by applying 0.04 g/ml soil water solution in two sand textures. For each experiment, soil water solution infiltration process was visualized using a bright field microscope and soil particles remained in the sand column was quantified collecting and measuring leachate at the end of the experiment in the soil and water lab of Cornell University. Preliminary results show that accumulation of significant amount of soil particles occur in between sand particles and at air water interfaces, indicating the clogging of soil pores occurs as a result of disturbed fine soil particles transported from the soil surface to the subsurface. Key Words: Soil pore clogging; Hardpans; Green water productivity Visualization of sand column experiment showing the sand column at the start of the experiment (left) and two hours after the second application in that soil particles were accumulated at the air water interfaces(right).

Tebebu, T.; Baver, C.; Stoof, C.; Steenhuis, T. S.

2013-12-01

303

Effects of organic compounds, water content and clay on the water repellency of a model sandy soil  

Microsoft Academic Search

Soil water repellency is related to organic matter and clay, and varies non-linearly with soil water content. The purpose of this study is to assess the combined effects of organic compounds, water content and clays on water repellency of a model sandy soil under wetting and drying processes. Hydrophobic stearic acid and hydrophilic glucomannan were used as the organic compounds,

D. A. L. Leelamanie; Jutaro Karube

2007-01-01

304

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

E-print Network

. The space-time statistical structure of soil water uptake by oak trees was investigated in a 3.1-mSoil water depletion by oak trees and the influence of root water uptake on the moisture content, resistance block measured soil water pressure, and a compact constant head permeameter measured saturated

Katul, Gabriel

305

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

306

Solubilization and biodegradation of polycyclic aromatic hydrocarbon compounds in soil-water suspensions with surfactants  

SciTech Connect

Hydrophobic organic compounds (HOCs) sorb strongly onto soil and sediment material, and the effectiveness of microbial treatment can be diminished by HOC phase partitioning and decreased substrate accessibility to microorganisms. Surfactant addition has been suggested as a technique for decreasing the interfacial tension and partitioning of the HOC with soil, and thereby increasing HOC mobility and bioavailability. However, this study indicates that nonionic surfactant solubilization of HOCs from soil may not be beneficial for the enhancement of soil bioremediation. The solubilization and microbial degradation of phenanthrene, a three-ring polycyclic aromatic hydrocarbon (PAH) compound, was examined in various soil-water systems with commercially-available surface-active agents. This was accomplished by a series of batch tests using radiolabeled techniques. The purpose of surfactant addition was to assess the effect of surfactant solubilization of PAHs on their biodegradation. For soil-water suspensions without surfactant approximately 50-60% of the phenanthrene was mineralized over the course of ten weeks. The addition of nonionic surface-active agents was observed not to be beneficial for microbial mineralization of phenanthrene in the soil-water systems, and for supra-CMC surfactant doses phenanthrene mineralization was completely inhibited for all the surfactants tested. Sub-CMC levels of surfactant in the soil-water systems generally did not have an inhibitory effect on phenanthrene mineralization, but neither did such doses serve to enhance the rate of degradation, which proceeded most rapidly in the absence of any surfactant. Companion tests suggest that the supra-CMC inhibitory effect is not a toxicity phenomenon, per se, of the surfactant or micellized PAH. An assessment of the results from the various experiments suggest that the inhibitory effect is probably related to a reversible physiological surfactant micelle-bacteria interaction.

Laha, S.

1992-01-01

307

Developing joint probability distributions of soil water retention characteristics  

Microsoft Academic Search

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

Robert F. Carsel; Rudolph S. Parrish

1988-01-01

308

Effect of the soil water content on Jatropha seedlings in a tropical climate  

NASA Astrophysics Data System (ADS)

The purpose of this study was to evaluate growth, chlorophyll content, and photosynthesis in Jatropha at different levels of soil moisture. Plants were cultivated in containers and the treatments of the soil water content evaluated were: 0% (without watering), 20, 40, 60, and 80% soil water content. Plant height was statistically similar for all treatments, but the number of leaves differed significantly. Total dry matter and chlorophyll at 40, 60, and 80% soil water content were statistically similar, but different from 0 and 20% soil water content. Leaf area at 40, 60, and 80% soil water content was statistically different from 0 and 20% soil water content. The photosynthetic rate, transpiration and stomatal conductance at 60 and 80% soil water content were statistically similar but different from 0 and 20% soil water content. Water stress affected growth, chlorophyll content, photosynthetic rate, transpiration, and stomatal conductance.

Pérez-Vázquez, A.; Hernández-Salinas, G.; Ávila-Reséndiz, C.; Valdés-Rodríguez, O. A.; Gallardo-López, F.; García-Pérez, E.; Ruiz-Rosado, O.

2013-09-01

309

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

310

Soil Moisture: The Hydrologic Interface Between Surface and Ground Waters  

NASA Technical Reports Server (NTRS)

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

Engman, Edwin T.

1997-01-01

311

Modeling of water balance, cracking and subsidence of clay soils  

NASA Astrophysics Data System (ADS)

A general procedure has been developed to model water balance, cracking and subsidence of clay soils. The main feature of this procedure is the introduction of the shrinkage characteristic in addition to the water retention and hydraulic conductivity curves into simulation models. The proposed procedure enables direct calculation of volume changes in dependance on moisture transport. With appropriate assumptions for geometry of swelling and shrinkage, these volume changes are converted into cracking and subsidence. Taking into account the calculated area of shrinkage cracks at the soil surface, together with the maximum infiltration rate of the soil matrix and the rainfall intensity, rainfall is dynamically partitioned in matrix and crack infiltration. In this way bypass flow and resulting rapid rises of groundwater levels in cracked soils can be simulated. The procedure was validated by adapting a model for calculation of transient moisture flow in soils, FLOWEX, into a version applicable on clay soils, FLOCR. Computations with FLOCR of subsidence, cracking, groundwater level and top layer wetness of a Dutch basin clay soil during 1985 were in good agreement with field observations. Moreover, the proposed method of bypass calculation is supported by good correspondence between measured and simulated rapid rises of groundwater levels.

Bronswijk, J. J. B.

1988-02-01

312

Chemical migration during soil water retention curve evaluation.  

PubMed

Wetting and drying (W-D) cycles can induce important elemental migrations in soils. The main purpose of this work was to study the possible existence of soil chemical elemental migrations in samples submitted to repeated W-D cycles during evaluations of soil water retention curve (SWRC). The experimental measurements were carried out by Atomic Absorption Spectrometry (AAS) for Ca(2+), Mg(2+) and K(+) on samples of three different Brazilian tropical soils (Geric Ferralsol, Eutric Nitosol and Rhodic Ferralsol). Results demonstrate an increase in the electrical conductivity of the water extracted from the samples and significant losses of Ca(2+), Mg(2+) and K(+) during the applications of up to nine W-D cycles. It was also observed differences in SWRC for all soils when samples submitted to the application of several W-D cycles were compared with samples not submitted to it. These differences occurred at the region of both structural and textural pores. A possible explanation for these results could be the soil chemical migration during the sequences of W-D cycles, which can affect the soil structure development. PMID:21830003

Pires, Luiz F; Villanueva, Felipe C A; Dias, Nivea M P; Bacchi, Osny O Santos; Reichardt, Klaus

2011-09-01

313

Biological interactions between soil nitrogen and alkaline-hydrolysing nitrogen fertilizers  

Microsoft Academic Search

Added N interactions were measured in four soil incubated with 15N-labelled urea or diammonium phosphate. The use of biologically active, ?-irradiated, or reinoculated ?-irradiated samples allowed us to separate added N interactions due to chemical and biological processes, and to distinguish real interactions from apparent effects. Real biologically mediated added N interactions were observed in one soil for both fertilizer

S. Sen; P. M. Chalk

1995-01-01

314

From the litter layer to the saprolite: Chemical changes in water-soluble soil organic matter and their correlation to  

E-print Network

From the litter layer to the saprolite: Chemical changes in water-soluble soil organic matter 2013 Accepted 27 September 2013 Available online 14 October 2013 Keywords: Water soluble organic matter matter/microbe interactions EEM-PARAFAC a b s t r a c t Organic matter content and chemistry is vital

Colorado at Boulder, University of

315

Scale Issues in Developing Regional-Scale Soil Water Balance Surfaces  

Microsoft Academic Search

Availability of water in the soil is a key environmental parameter for many models of physical systems from those dealing with plant ecology and biodiversity, crop production, and even soil erosion, ground water pollution and hydrological processes. Landcare Research has been developing a model for making spatial estimates of soil water balance based on best available soil and climate data.

James Barringer; Linda Lilburne

316

Effects of hydrophobic and hydrophilic organic matter on the water repellency of model sandy soils  

Microsoft Academic Search

Soil water repellency affects the hydrological functions of soil systems. Water repellency is associated with the content and the composition of soil organic matter. In the present study, we examined the effects of hydrophobic and hydrophilic organic matter contents, the hydrophobic\\/hydrophilic organic matter ratio and the total organic matter content on water repellency using model sandy soils. Stearic acid and

D. A. L. Leelamanie; Jutaro Karube

2009-01-01

317

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

318

Field measurement of soil water repellency and its impact on water flow under different vegetation  

Microsoft Academic Search

Numerous recent laboratory studies have shown that vegetation can influence soil water flow by inducing very low levels of\\u000a water repellency. In this study we extended on this previous research by developing a field-based test using a miniature infiltrometer\\u000a to assess low levels of water repellency from physically based measurements of liquid flow in soil. The field-based test was\\u000a verified

L’ubomír Lichner; Paul D. Hallett; Debbie S. Feeney; Olívia ?ugová; Miroslav Tesa?

2007-01-01

319

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. PMID:20639342

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

2010-01-01

320

Laboratory Characterization of Capacitance Sensors for Measuring Soil Water Content  

NASA Astrophysics Data System (ADS)

Automated sensing of soil water content with capacitance methods is common due to the relative ease of installation and monitoring at multiple sites. The resonant frequency of an inductance-capacitance circuit is a function of the dielectric permittivity of the material surrounding the ring-capacitor sensor. However, limited relationships between resonant frequency and permittivity in the soil water range have been reported. Furthermore, sensor readings and apparent water contents have been shown to vary with temperature in laboratory and field studies in the opposite direction of that expected for free water. We designed laboratory equipment and experiments to improve our fundamental knowledge about the behavior and characterization of such a capacitance sensor (Sentek EnviroSMARTTM). Four sensors are used for resonant frequency readings, while a fifth measures total capacitance directly on an HP Network Analyzer. A solvent-resistant container was designed for water-dioxane mixtures, which provide a complete range of permittivity values from 2.2 to over 80. The sensor readings are sensitive to permittivity changes in the range expected for soils from very dry to fully saturated. Variability between four sensors is reduced by normalization to readings in air and water. Frequency-based permittivity estimates in free water decreased linearly with temperature, as expected, substantiating the field-measured temperature dependence. Next, an expanding metal cylinder was used to interfere with the electrical field in air, water and two dioxane-water mixtures. The change in normalized readings with distance to the metal boundary is approximated by a negative exponential function with a characteristic length of 11 mm. The laboratory results are confirmed with numerical experiments assuming axisymmetric materials. Using the improved capacitance sensor characterization, water content can be estimated directly from permittivity using a universal calibration, and there is now a stronger basis for addressing the temperature-dependence of measurements in soil-air-water systems.

Green, T. R.; Schwank, M.; Flühler, H.

2005-12-01

321

SOIL FUNGI ALTER INTERACTIONS BETWEEN THE INVADER CENTAUREA MACULOSA AND NORTH AMERICAN NATIVES  

Microsoft Academic Search

Soil microbes may affect the way exotic invasive plants interact with native neighbors. We investigated the effects of soil fungi on interactions between the invasive weed Centaurea maculosa(spotted knapweed) and six species native to the intermountain prairies of the northwestern United States. We also compared the effect of C. maculosa on the composition of the soil microbial community to that

Ragan M. Callaway; Giles C. Thelen; Sara Barth; Philip W. Ramsey; James E. Gannon

2004-01-01

322

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

E-print Network

Interaction effects of climate and land use/land cover change on soil organic carbon sequestration carbon sequestration Climate change Soil carbon change Historically, Florida soils stored the largest in Florida (FL) have acted as a sink for carbon (C) over the last 40 years. � Climate interacting with land

Grunwald, Sabine

323

Farm water budgets for semiarid irrigated floodplains of northern New Mexico: characterizing the surface water-groundwater interactions  

NASA Astrophysics Data System (ADS)

KEY WORDS - Hydrology, Water budget, Deep percolation, Surface water-Groundwater interactions. With the recent projections for water scarcity, water balances have become an indispensable water management tool. In irrigated floodplains, deep percolation from irrigation can represent one of the main aquifer recharge sources. A better understanding of surface water and groundwater interactions in irrigated valleys is needed for properly assessing the water balances in these systems and estimating potential aquifer recharge. We conducted a study to quantify the parameters and calculate the water budgets in three flood irrigated hay fields with relatively low, intermediate and, high water availability in northern New Mexico. We monitored different hydrologic parameters including total amount of water applied, change in soil moisture, drainage below the effective root zone, and shallow water level fluctuations in response to irrigation. Evapotranspiration was calculated from weather station data collected in-situ using the Samani-Hargreaves. Previous studies in the region have estimated deep percolation as a residual parameter of the water balance equation. In this study, we used both, the water balance method and actual measurements of deep percolation using passive lysimeters. Preliminary analyses for the three fields show a relatively rapid movement of water through the upper 50 cm of the vadose zone and a quick response of the shallow aquifer under flood irrigation. Further results from this study will provide a better understanding of surface water-groundwater interactions in flood irrigated valleys in northern New Mexico.

Gutierrez, K. Y.; Fernald, A.; Ochoa, C. G.; Guldan, S. J.

2013-12-01

324

Polychlorinated biphenyl sorption by soils: Measurement of soil-water partition coefficients at equilibrium  

Microsoft Academic Search

The sorption of PCB congeners 24? (lUPAC number 8), 22?55? (52) and 22?44?55? (153) by eight soils differing in their organic carbon content (2.3 to 0.2% by Wt.) and expandable clay mineral content (17 to 53 % by wt.) has been investigated for 0.1 g\\/L soil-water suspensions. The time to reach sorption equilibrium, i.e. sorption-diffusion equilibrium, for a highly aggregated

Don C. Girvin; Al J. Scott

1997-01-01

325

Factors affecting drying and wetting soil-water characteristic curves of sandy soils  

Microsoft Academic Search

Drying and wetting soil-water characteristic curves (SWCCs) for five sandy soils are investigated using a Tempe pressure cell and capillary rise open tube. The test data are fitted to two SWCC equations using a least-squares algorithm. The obtained fitting parameters and some hysteretic behaviour are discussed and correlated with grain-size distribution parameters. A concept of total hysteresis is proposed to

Hong Yang; Harianto Rahardjo; Eng-Choon Leong; D. G. Fredlund

2004-01-01

326

Using soil surface gray level to determine surface soil water content  

Microsoft Academic Search

How to determine surface soil water content (SWC) quickly and accurately is fundamental in studying eco-hydrological processes\\u000a and their modeling. Here we use laboratory experiments to determine surface SWC using soil surface gray level (SGL) values.\\u000a A negatively exponential relationship exists between SGL and SWC, i.e., SGL increases with the decrease of SWC. SGL can be\\u000a estimated based on initial

YuanJun Zhu; YunQiang Wang; MingAn Shao

2010-01-01

327

Water-Retention of Fractal Soil Models Using Continuum Percolation Theory: Tests of Hanford Site Soils  

Microsoft Academic Search

ABSTRACT,of percolation theory for flow in a fractal medium in- creases understanding of the steady-state hydraulic con- For 43 Hanford site soils, we use fractal analysis and assume propor- ductivity in the DOE Hanford Site soils. A related prob- tionality of pore radii to particle radii to generate water-retention curves, h(), from particle-size distributions. The air-entry head is lem, which

Allen G. Hunt; Glendon W. Gee

2002-01-01

328

Multiscale Bayesian neural networks for soil water content estimation  

NASA Astrophysics Data System (ADS)

Artificial neural networks (ANN) have been used for some time now to estimate soil hydraulic parameters from other available or more easily measurable soil properties. However, most such uses of ANNs as pedotransfer functions (PTFs) have been at matching spatial scales (1:1) of inputs and outputs. This approach assumes that the outputs are only required at the same scale as the input data. Unfortunately, this is rarely true. Different hydrologic, hydroclimatic, and contaminant transport models require soil hydraulic parameter data at different spatial scales, depending upon their grid sizes. While conventional (deterministic) ANNs have been traditionally used in these studies, the use of Bayesian training of ANNs is a more recent development. In this paper, we develop a Bayesian framework to derive soil water retention function including its uncertainty at the point or local scale using PTFs trained with coarser-scale Soil Survey Geographic (SSURGO)-based soil data. The approach includes an ANN trained with Bayesian techniques as a PTF tool with training and validation data collected across spatial extents (scales) in two different regions in the United States. The two study areas include the Las Cruces Trench site in the Rio Grande basin of New Mexico, and the Southern Great Plains 1997 (SGP97) hydrology experimental region in Oklahoma. Each region-specific Bayesian ANN is trained using soil texture and bulk density data from the SSURGO database (scale 1:24,000), and predictions of the soil water contents at different pressure heads with point scale data (1:1) inputs are made. The resulting outputs are corrected for bias using both linear and nonlinear correction techniques. The results show good agreement between the soil water content values measured at the point scale and those predicted by the Bayesian ANN-based PTFs for both the study sites. Overall, Bayesian ANNs coupled with nonlinear bias correction are found to be very suitable tools for deriving soil hydraulic parameters at the local/fine scale from soil physical properties at coarser-scale and across different spatial extents. This approach could potentially be used for soil hydraulic properties estimation and downscaling.

Jana, Raghavendra B.; Mohanty, Binayak P.; Springer, Everett P.

2008-08-01

329

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

330

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

Microsoft Academic Search

Abstract. Estimation of the retention and unsaturated,hydraulic conductivity functions is essential to effectively provide input for water flow and transport simulation,and prediction. A parameter,optimization,procedure,is shown,as a promising,tool to estimate inversely these hydraulic function parameters,from transient soil matric potential and cumulative,soil solution extraction measurements.,Sensitivity analyses from synthetic data generated,from forward,numerical,model,simulations showed,that optimum,tensiometer locations will depend,on soil type. Experiments,were carried out in

M. Inoue; J. Šimunek; J. W. Hopmans; V. Clausnitzer

1998-01-01

331

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

332

Organic compounds in hot-water-soluble fractions from water repellent soils  

NASA Astrophysics Data System (ADS)

Water repellency (WR) is a soil property providing hydrophobic protection and preventing rapid microbial decomposition of organic matter entering the soil with litter or plant residues. Global warming can cause changes in WR, thus influencing water storage and plant productivity. Here we assess two different approaches for analysis of organic compounds composition in hot water extracts from accelerated solvent extraction (ASE) of water repellent soils. Extracts were lyophilized, fractionated on SiO2 (sand) and SPE cartridge, and measured by GC/MS. Dominant compounds were aromatic acids, short chain dicarboxylic acids (C4-C9), sugars, short chain fatty acids (C8-C18), and esters of stearic and palmitic acids. Polar compounds (mainly sugars) were adsorbed on applying SPE clean-up procedure, while esters were highly abundant. In addition to the removal of polar compounds, hydrophobic esters and hydrocarbons (alkanes and alkenes < C20) were extracted through desorption of complex colloids stabilized as micelles in dissolved organic carbon (DOC). Water repellency was completely eliminated by hot water under high pressure. The molecular composition of HWSC can play a critical role in stabilization and destabilization of soil organic matter (SOM), particle wettability and C dynamics in soils. Key words: soil water repellency, hot water soluble carbon (HWSC), GC/MS, hydrophobic compounds

Atanassova, Irena; Doerr, Stefan

2014-05-01

333

The speciation of water-soluble Al and Zn in the rhizosphere of forest soils.  

PubMed

This study focuses on the relationships of dissolved Al and Zn speciation with microbial and chemical soil properties in the bulk and rhizosphere of forest soils. The soil components were sampled under Populus tremuloides Michx. at six sites located close to industrial facilities. Total water-soluble (Al(WS), Zn(WS)) and reactive (Al(R), Zn(R)) Al and Zn concentrations measured in soil water extracts, speciation data modeled by WHAM 6, chemical properties (pH, DOC, major cations and anions) and microbial properties (microbial biomass and enzyme activities) were measured on all soils. Enrichment in Al(R) and Zn(R) was observed in the rhizosphere compared to bulk soils. In a given soil material, the speciation of Al and Zn varied according to solution pH and Al-organic as well as Zn-organic complexes or Zn(2+) were generally the dominant species. The factors controlling the Al(WS), Zn(WS), Al(R) and Zn(R) concentrations differed between soil components, shifting from strictly chemical in the bulk (78%) to interactions among microbial and chemical variables in the rhizosphere (87%). Results further indicate that organic matter and pH were significantly linked to these response variables in the rhizosphere. Involvement of rhizospheric microorganisms occurred via pH changes induced by either the microbial assimilation of nitrogen or through the release of metals during the mineralization of roots. Our results therefore suggest that microbial activity is an important component of the biogeochemistry of Al and Zn in the rhizosphere. The study further provides key information to improve the assessment of ecological risk associated to Al and Zn in forest soils. PMID:20383395

Cloutier-Hurteau, Benoît; Turmel, Marie-Claude; Sauvé, Sébastien; Courchesne, François

2010-06-01

334

Response of rice genotype to straighthead disease as influenced by arsenic level and water management practices in soil.  

PubMed

Arsenic (As) uptake by rice plants and the straighthead disease induced by As-based herbicide are of environmental concerns. Bioavailability or mobility of inorganic As in soil has been reported to be significantly influenced by soil minerals such as iron (hydr) oxide; however, the interactions of organic As such as monosodium methanearsonate (MSMA) with soil minerals are little studied, thus largely unknown. In an effort to minimize the As uptake by rice and determine rice cultivar response to soil MSMA level, a field experiment was conducted on three rice cultivars grown in both MSMA-treated and -untreated soils under continuous or intermittent flood water management practices. Results indicated that the grain yield and the occurrence of straighthead disease were cultivar-dependent and influenced by soil As level and water management practices. Straighthead-resistant cultivars yielded more and had lower grain As than the susceptible ones. Elevated soil As with continuous flood management significantly reduced the grain yield of susceptible cultivars by >89% due to substantially increased straighthead, which were induced by increased As content in grains. Yield reduction by MSMA treatment could be partially mitigated with intermittent flood water practice. The As accumulation was found to be associated with soil iron redox transformation influenced by the water management. This study demonstrates that the selection of less As-susceptible cultivars and intermittent flood water practice could be effective means to lower the As accumulation in grains and minimize the occurrence of the As-induced straighthead symptom and yield reduction. PMID:23183123

Hua, Bin; Yan, Wengui; Yang, John

2013-01-01

335

Transport of PCBs with leachate water from contaminated soil.  

PubMed

Natural soil contaminated with PCBs was used in this study. The soil was excavated from the area around the damaged capacitor of an electrical transformer station in Zadar (ETS 110/35 kV). A lysimeter experiment was conducted for 17 months under natural climatic conditions and designed to measure the concentration of PCB in the soil and leachates. Our research field was composed of four plots and there were three lysimeters on each plot. After 12 months, a negligible quantity of Aroclor 1248 (an average of 0.24%) and the Sigma 7 key PCB congeners (SigmaPCB(7); IUPAC No.: PCB 28, PCB 52, PCB 101, PCB 118, PCB 138, PCB 153 and PCB 180) were leached from the soils into the water collected under the lysimeters (an average of 0.32%). During two soil samplings, the soil was taken at three depths from each lysimeter. The distribution of Aroclor 1248 and 7 individual PCB congeners in the soil layers was determined before and after planting. Plot No. 1 had the highest percentage of contaminant removal after 12 months. The data indicate that the Sigma 7 key PCBs in the surface soil layers of all the plots decreased and the removal percentages ranged between 19.0% (Plot No. 2) and 47.6% (Plot No. 1). Volatilization from the soil surface may be the most important mechanism for the loss of these "more volatile" PCB congeners. The results showed an accumulation of PCBs in the deepest level of the soil plots, probably due to the vertical transfer of the PCBs and the lack of volatilization. PMID:18440045

Kobasi?, Vedranka Hodak; Picer, Mladen; Picer, Nena; Cali?, Violeta

2008-08-01

336

Subcritical water extraction to isolate kinetically different soil nitrogen fractions  

NASA Astrophysics Data System (ADS)

Soil organic N is largely composed of inherently biologically labile proteinaceous N and its persistence in soil is mainly explained by stabilization through binding to minerals and other soil organic matter (SOM) components at varying strengths. In order to separate kinetically different soil N fractions we hypothesize that an approach, which isolates soil N fractions on the basis of bonding strength is required, rather than employing chemical agents or physical methods. We developed a sequential subcritical water extraction (SCWE) procedure at 100 °C, 150 °C and 200°C to isolate SOM fractions. We assessed these SCWE N fractions as predictors for aerobic and anaerobic N mineralization measured from 25 paddy soil cores in incubations. SCWE organic carbon (SCWE OC) and N (SCWE N) increased exponentially with the increase of temperature and N was extracted preferentially over OC. The efficiency of SCWE and the selectivity towards N were both lower in soils with increasingly reactive clay mineralogy. The 100-150 °C SCWE N and the 100 °C + 100-150 °C SCWE N correlated slightly better with the aerobic N mineralization than soil N content. The resulting explained percentages (46-49%) are, however, too small to allow accurate fertilizer recommendations. No correlations were found between the SCWE fractions and anaerobic N mineralization rate and consequently alternative driving factors should be looked for. Nonetheless, perhaps SCWE does, still hold potential to separate kinetically different SOM pools from upland soils, in which the bio-availability of N is more likely to be a key constraint in the N mineralization process. This in contrast to the studied paddy soils, in which N mineralization appeared to be largely decoupled from SOM quantity and quality or its availability, perhaps due to an overriding control of abiotic factors on the anaerobic N mineralization process.

Sleutel, S.; Kader, M. A.; Demeestere, K.; Walgraeve, C.; Dewulf, J.; De Neve, S.

2013-06-01

337

The importance of plant-soil interactions for N mineralisation in different soil types  

NASA Astrophysics Data System (ADS)

The last hundred years has seen major advancements in our knowledge of nitrogen mineralisation in soil, but key drivers and controls remain poorly understood. Due to an increase in the global population there is a higher demand on food production. To accommodate this demand agriculture has increased its use of N based fertilizers, but these pose risks for water quality and GHG emissions as N can be lost through nitrate leaching, ammonia volatilization, and denitrification processes (Velthof, et al., 2009). Therefore, understanding the underlying processes that determine the soils ability to supply N to the plant is vital for effective optimisation of N-fertilisation with crop demand. Carbon rich compounds exuded from plant roots to the rhizosphere, which are utilized by the microbial biomass and support activities including nutrient transformations, may be a key unaccounted for driver of N mineralisation. The main aim of this study was to study the impact of root exudates on turnover of C and N in soil, as mediated by the microbial community. Two soil types, known to contrast in N-mineralisation capacity, were used to determine relationships between C inputs, organic matter mineralisation (priming effects) and N fluxes. 15N and 13C stable isotope approaches were used to quantify the importance of rhizosphere processes on C and N mineralisation. Gross nitrogen mineralisation was measured using 15N pool dilution. Total soil CO2 efflux was measured and 13C isotope partitioning was applied to quantify SOM turnover and microbial biomass respiration. Also, 13C was traced through the microbial biomass (chloroform fumigation) to separate pool-substitution effects (apparent priming) from altered microbial utilisation of soil organic matter (real priming effects). Addition of labile carbon resulted in an increase in N-mineralisation from soil organic matter in both soils. Concurrent with this there was an increase in microbial biomass size, indicating that labile C elicited real priming effects that mobilised N from organic matter. The results from this experiment indicate that rhizosphere processes play an important role in mediating rates of C and N mineralisation and should be accounted for in estimating soil N-supply capacities. Velthof, G.L., Oudendag, D., Witzke, H.P., Asman, W.A.H., Klimont, Z., Oenema, O., 2009. Integrated assessment of nitrogen losses from agriculture in EU-27 using MITERRA-EUROPE. Journal of Environmental Quality 38, 402-417.

Murphy, Conor; Paterson, Eric; Baggs, Elizabeth; Morley, Nicholas; Wall, David; Schulte, Rogier

2013-04-01

338

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. PMID:23369199

2012-01-01

339

Spatiotemporal Pattern of Root Water Uptake for Locally Differing Soil Water Availability  

NASA Astrophysics Data System (ADS)

One of the important but not well known questions is how the root system of a plant respond to water scarcity, especially if there is a locally heterogeneous distribution of soil moisture or accessibility of water. However, heterogeneous water availability is a typical characteristic of soils, for example by heterogeneity of soil properties, infiltration and evaporation or competition between plant roots. On top of that, water content in soil has a large temporal dynamics. Despite these intrinsic heterogeneities of soil-plant water relations, we know little about the ways how plants respond to local environmental properties. Recently imaging and tomography methods have become available, that facilitate the measurement of spatial and temporal distribution of water content and of the root system itself, which offers the possibility to investigate also the distribution of water uptake in a plant root system. To monitor root water uptake response to local soil water availability, we used neutron radiography especially suited to detect water distribution, to non-invasively image root growth and 2-D soil water distribution as time-lapsed images. We applied a method to hydraulically partition the soil to be able to actively control the level of water available locally and at the same time to locally quantify water uptake for these heterogeneous conditions. The key results for an imaging experiment running full three weeks show topological patterns of water uptake along the root system. Moreover, under water stress, compensatory root water uptake maximizes soil water utilization in response to transpiration demand. Lupin plants were grown in 40*35*1 cm³ aluminum containers. The root zone was partitioned into twenty compartments separated by capillary barriers and divides the root system into taproot and lateral roots, and into young and old later root segments at the top, middle and bottom profile positions. Three weeks after planting, four soil-water treatments in three replaces each, were applied as: no stress (control), %50 stress (water available for 50% of the lateral roots) and 75% stress (water available for 25% of lateral roots in old and young parts in two individual treatments). Two levels of transpiration demand in 5-day periods each were also applied, interrupted by five days of recovering in between. Daily changes in soil water content and root water uptake rate in each compartment have been monitored by neutron radiography four times a day as well as daily transpiration rates. The results show a high compensatory water uptake by the root segments in the wet parts under water stress. This root compensation increases significantly with increasing portion of the root system suffering water scarcity. ; While for low transpiration demand, there was not a significant difference in transpiration rate between 50% and 25% local water availability, for higher transpiration demand transpiration demand cannot be fully compensated when water is provided for the root system locally. In respect to root topology , root segments in the top with less distance to the shoot show higher rates of water uptake then those in the lower position while the difference in local root water uptake between old and young roots is not that high.

Dara, Abbas; Moradi, Ahmad B.; Oswald, Sascha

2013-04-01

340

Interaction Effects of Selected Pesticides on Soil Enzymes  

PubMed Central

The laboratory studies were conducted to resolute the effects of imidacloprid (insecticide) and triadimefon (fungicide) singly and in combination on enzymatic activities of soil microorganisms in tomato cultivated soils at different concentrations of 0.2, 0.5 and 0.7 kg/ha. The rate of amylase activity was stimulated by the application of pesticides at field rate. High dosage decreased the activity of amylase. Decline in the activity of cellulase was observed at all concentrations than control. Imidacloprid had an improved activity of cellulase at 0.5 ?g/g than tridimefon and combination. At higher concentration (0.7 ?g/g), the combination of insecticide and fungicide showed an antagonistic interaction toward cellulase. After 24 h, maximum inhibition was observed in invertase enzyme rate at all examined dosages. After 48 h, the activity was revived to some extent and imidacloprid showed enhanced activity at 0.5 ?g/g (field rate). However at 0.7 ?g/g, imidacloprid has a noticeable effect on the invertase. The pesticide application in single and in combination (0.2-0.7 ?g/g soil) triggered the dehydrogenase activity. At field rate triadimefon significantly quickened the activity. PMID:24403727

Deborah, B. Vineela; Mohiddin, M. Jaffer; Madhuri, R. Jaya

2013-01-01

341

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

NASA Technical Reports Server (NTRS)

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

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

1975-01-01

342

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

343

UF/IFAS Soil and Water Science 2181 McCarty Hall  

E-print Network

& Environmental Policy 3 sws 4245 Water Resource Sustainability 3 sws 4307 Ecology of Waterborne Pathogens 3Contact UF/IFAS Soil and Water Science 2181 McCarty Hall PO Box 110290 Gainesville, FL 32611 Phone: 352.294.3152 E-mail: mjsisk@ufl.edu soils.ifas.ufl.edu soil and water science major WATER SCIENCE u n

Jawitz, James W.

344

Morphology of rain water channelization in systematically varied model sandy soils  

E-print Network

We visualize the formation of fingered flow in dry model sandy soils under different raining conditions using a quasi-2d experimental set-up, and systematically determine the impact of soil grain diameter and surface wetting property on water channelization phenomenon. The model sandy soils we use are random closely-packed glass beads with varied diameters and surface treatments. For hydrophilic sandy soils, our experiments show that rain water infiltrates into a shallow top layer of soil and creates a horizontal water wetting front that grows downward homogeneously until instabilities occur to form fingered flows. For hydrophobic sandy soils, in contrast, we observe that rain water ponds on the top of soil surface until the hydraulic pressure is strong enough to overcome the capillary repellency of soil and create narrow water channels that penetrate the soil packing. Varying the raindrop impinging speed has little influence on water channel formation. However, varying the rain rate causes significant changes in water infiltration depth, water channel width, and water channel separation. At a fixed raining condition, we combine the effects of grain diameter and surface hydrophobicity into a single parameter and determine its influence on water infiltration depth, water channel width, and water channel separation. We also demonstrate the efficiency of several soil water improvement methods that relate to rain water channelization phenomenon, including pre-wetting sandy soils at different level before rainfall, modifying soil surface flatness, and applying superabsorbent hydrogel particles as soil modifiers.

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

2014-03-13

345

Morphology of Rain Water Channeling in Systematically Varied Model Sandy Soils  

NASA Astrophysics Data System (ADS)

We visualize the formation of fingered flow in dry model sandy soils under different rain conditions using a quasi-2D experimental setup and systematically determine the impact of the soil grain diameter and surface wetting properties on the water channeling phenomenon. The model sandy soils we use are random closely packed glass beads with varied diameters and surface treatments. For hydrophilic sandy soils, our experiments show that rain water infiltrates a shallow top layer of soil and creates a horizontal water wetting front that grows downward homogeneously until instabilities occur to form fingered flows. For hydrophobic sandy soils, in contrast, we observe that rain water ponds on the top of the soil surface until the hydraulic pressure is strong enough to overcome the capillary repellency of soil and create narrow water channels that penetrate the soil packing. Varying the raindrop impinging speed has little influence on water channel formation. However, varying the rain rate causes significant changes in the water infiltration depth, water channel width, and water channel separation. At a fixed rain condition, we combine the effects of the grain diameter and surface hydrophobicity into a single parameter and determine its influence on the water infiltration depth, water channel width, and water channel separation. We also demonstrate the efficiency of several soil water improvement methods that relate to the rain water channeling phenomenon, including prewetting sandy soils at different levels before rainfall, modifying soil surface flatness, and applying superabsorbent hydrogel particles as soil modifiers.

Wei, Yuli; Cejas, Cesare M.; Barrois, Rémi; Dreyfus, Rémi; Durian, Douglas J.

2014-10-01

346

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

Microsoft Academic Search

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

Yaohu Kang; Shuqin Wan

2005-01-01

347

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

348

Predawn disequilibrium between plant and soil water potentials in two cold-desert shrubs  

Microsoft Academic Search

Classical water relations theory predicts that predawn plant water potential should be in equilibrium with soil water potential\\u000a (soil ?w) around roots, and many interpretations of plant water status in natural populations are based on this expectation. We examined\\u000a this expectation for two salt-tolerant, cold-desert shrub species in glasshouse experiments where frequent watering assured\\u000a homogeneity in soil ?w and soil-root

L. A. Donovan; D. J. Grisé; J. B. West; R. A. Pappert; N. N. Alder; J. H. Richards

1999-01-01

349

Hysteresis and uncertainty in soil water-retention curve parameters  

USGS Publications Warehouse

Accurate estimates of soil hydraulic parameters representing wetting and drying paths are required for predicting hydraulic and mechanical responses in a large number of applications. A comprehensive suite of laboratory experiments was conducted to measure hysteretic soil-water characteristic curves (SWCCs) representing a wide range of soil types. Results were used to quantitatively assess differences and uncertainty in three simplifications frequently adopted to estimate wetting-path SWCC parameters from more easily measured drying curves. They are the following: (1) ?w=2?d, (2) nw=nd, and (3) ?ws=?ds, where ?, n, and ?s are fitting parameters entering van Genuchten’s commonly adopted SWCC model, and the superscripts w and d indicate wetting and drying paths, respectively. The average ratio ?w/?d for the data set was 2.24±1.25. Nominally cohesive soils had a lower ?w/?d ratio (1.73±0.94) than nominally cohesionless soils (3.14±1.27). The average nw/nd ratio was 1.01±0.11 with no significant dependency on soil type, thus confirming the nw=nd simplification for a wider range of soil types than previously available. Water content at zero suction during wetting (?ws) was consistently less than during drying (?ds) owing to air entrapment. The ?ws/?ds ratio averaged 0.85±0.10 and was comparable for nominally cohesive (0.87±0.11) and cohesionless (0.81±0.08) soils. Regression statistics are provided to quantitatively account for uncertainty in estimating hysteretic retention curves. Practical consequences are demonstrated for two case studies.

Likos, William J.; Lu, Ning; Godt, Jonathan W.

2014-01-01

350

Observing plants dealing with soil water stress: Daily soil moisture fluctuations derived from polymer tensiometers  

NASA Astrophysics Data System (ADS)

Periods of soil water deficit often occur within a plant's life cycle, even in temperate deciduous and rain forests (Wilson et al. 2001, Grace 1999). Various experiments have shown that roots are able to sense the distribution of water in the soil, and produce signals that trigger changes in leaf expansion rate and stomatal conductance (Blackman and Davies 1985, Gollan et al. 1986, Gowing et al. 1990 Davies and Zhang 1991, Mansfield and De Silva 1994, Sadras and Milroy 1996). Partitioning of water and air in the soil, solute distribution in soil water, water flow through the soil, and water availability for plants can be determined according to the distribution of the soil water potential (e.g. Schröder et al. 2013, Kool et al. 2014). Understanding plant water uptake under dry conditions has been compromised by hydrological instrumentation with low accuracy in dry soils due to signal attenuation, or a compromised measurement range (Whalley et al. 2013). Development of polymer tensiometers makes it possible to study the soil water potential over a range meaningful for studying plant responses to water stress (Bakker et al. 2007, Van der Ploeg et al. 2008, 2010). Polymer tensiometer data obtained from a lysimeter experiment (Van der Ploeg et al. 2008) were used to analyse day-night fluctuations of soil moisture in the vicinity of maize roots. To do so, three polymer tensiometers placed in the middle of the lysimeter from a control, dry and very dry treatment (one lysimeter per treatment) were used to calculate water content changes over 12 hours. These 12 hours corresponded with the operation of the growing light. Soil water potential measurements in the hour before the growing light was turned on or off were averaged. The averaged value was used as input for the van Genuchten (1980) model. Parameters for the model were obtained from laboratory determination of water retention, with a separate model parameterization for each lysimeter setup. Results show daily fluctuations in water content changes, with both root water uptake and root water excretion. The magnitude of the water content change was in the same order for all treatments, thus suggesting compensatory uptake. References Bakker G, Van der Ploeg MJ, de Rooij GH, Hoogendam CW, Gooren HPA, Huiskes C, Koopal LK and Kruidhof H. New polymer tensiometers: Measuring matric pressures down to the wilting point. Vadose Zone J. 6: 196-202, 2007. Blackman PG and Davies WJ. Root to shoot communication in maize plants of the effects of soil drying. J. Exp. Bot. 36: 39-48, 1985. Davies WJ and Zhang J. Root signals and the regulation of growth and development of plants in drying soil. Annu. Rev. Plant Physiol. Plant Mol. Biol. 42: 55-76, 1991. Gollan T, Passioura JB and Munns R. Soil water status affects the stomatal conductance of fully turgid wheat and sunflower leafs. Aust. J. Plant Physiol. 13: 459-464, 1986. Gowing DJG, Davies WJ and Jones HG. A Positive Root-sourced Signal as an Indicator of Soil Drying in Apple, Malus x domestica Borkh. J. Exp. Bot. 41: 1535-1540, 1990. Grace J. Environmental controls of gas exchange in tropical rain forests. In: Press, M.C, J.D. Scholes and M.G. Barker (ed.). Physiological plant ecology: the 39th Symposium of the British Ecological Society. Blackwell Science, United Kingdom, 1999. Kool D, Agam N, Lazarovitch N, Heitman JL, Sauer TJ, Ben-Gal A. A review of approaches for evapotranspiration partitioning. Agricultural and Forest Meteorology 184: 56- 70, 2014. Mansfield TA and De Silva DLR. Sensory systems in the roots of plants and their role in controlling stomatal function in the leaves. Physiol. Chem. Phys. & Med. 26: 89-99, 1994. Sadras VO and Milroy SP. Soil-water thresholds for the responses of leaf expansion and gas exchange: a review. Field Crops Res. 47: 253-266, 1996. Schröder N, Lazarovitch N, Vanderborcht J, Vereecken H, Javaux M. Linking transpiration reduction to rhizosphere salinity using a 3D coupled soil-plant model. Plant Soil 2013, doi: 10.1007/s11104-013-1990-8 Van der Ploeg MJ, Gooren HPA, Bakker G and de Rooij GH.

van der Ploeg, Martine; de Rooij, Gerrit

2014-05-01

351

A method to extract soil water for stable isotope analysis  

USGS Publications Warehouse

A method has been developed to extract soil water for determination of deuterium (D) and 18O content. The principle of this method is based on the observation that water and toluene form an azeotropic mixture at 84.1??C, but are completely immiscible at ambient temperature. In a specially designed distillation apparatus, the soil water is distilled at 84.1??C with toluene and is separated quantitatively in the collecting funnel at ambient temperature. Traces of toluene are removed and the sample can be analyzed by mass spectrometry. Kerosene may be substituted for toluene. The accuracy of this technique is ?? 2 and ?? 0.2???, respectively, for ??D and ??18O. Reduced accuracy is obtained at low water contents. ?? 1990.

Revesz, K.; Woods, P.H.

1990-01-01

352

Soil properties evolution after irrigation with reclaimed water  

NASA Astrophysics Data System (ADS)

Many arid and semi-arid countries are forced to look for new and alternative water sources. The availability of suitable quality water for agriculture in these regions often is threatened. In this context of water scarcity, the reuse of treated wastewater for crop irrigation could represent a feasible solution. Through rigorous planning and management, irrigation with reclaimed water presents some advantages such as saving freshwater, reducing wastewater discharges into freshwater bodies and decreasing the amount of added fertilizers due to the extra supply of nutrients by reclaimed water. The current study, which involves wastewater reuse in agriculture, has been carried out in the Experimental Plant of Carrión de los Céspedes (Sevile, Spain). Here, two survey parcels equally designed have been cultivated with Jatropha curcas L, a bioenergetic plant and a non-interfering food security crop. The only difference between the two parcels lies on the irrigation water quality: one is irrigated with groundwater and another one with reclaimed water. The main aim of this study focuses on analysing the outstanding differences in soil properties derived from irrigation with two water qualities, due to their implications for plant growth. To control and monitor the soil variables, soil samples were collected before and after irrigation in the two parcels. pH, electrical conductivity, cation exchange capacity, exchangeable cations (Ca2+, Mg2+, Na+ and K+), kjeldahl nitrogen, organic matter content and nutrients (boron, phosphorus, nitrogen, potassium) were measured. Data were statistically analyzed using the R package. To evaluate the variance ANOVA test was used and to obtain the relations between water quality and soil parameters, Pearson correlation coefficient was computed. According to other authors, a decrease in the organic matter content and an increase of parameters such as pH, electrical conductivity and some exchangeable cations were expected. To date and after one year of irrigation, no significant differences have been found among the soil properties of the two parcels. The results show in one hand, a slightly decrease in phosphorus, nitrates and electrical conductivity and on the other hand, an increase of organic matter. These trends should be contrasted by new soil quality measurements. The implications on vegetation growth, oil production and nutrients assimilation derived from the irrigation with reclaimed water should be also evaluated over time.

Leal, M.; González-Naranjo, V.; de Miguel, A.; Martínez-Hernández, V.; Lillo, J.

2012-04-01

353

[Optimum soil water supply range of Malus pumila].  

PubMed

By means of the determination of net photosynthetic rate and transpiration rate of the leaves of seven-year field and two-year spotted Malus pumila (Goldspur) under different soil water contents and illumination and calculation of water use efficiency (WUE), the optimum soil water supply range of Malus pumila was determined. The results showed that because photosynthetic advantageous radiation (PAR) and soil water content (SWC) decided the value of photosynthetic rate and transpiration rate of Goldspur, thus they influenced the value of WUE. The response of WUE to illumination had relations with soil water. When SWC was 10% (50% of field capacity-FC) or so, the maximum of WUE was the highest value among all the soil water treatment and reached about 230 mumolCO2.g-1H2O. When the water supply was adequate (SWC > 15%), the maximum was only 160 mumolCO2.g-1H2O or so, the difference between each SWC level was not obvious and simulated curve fundamentally overlapped, although WUE decreased slowly after reached the maximum. The variation of WUE with SWC had relations with illumination. WUE was the highest while PAR was in the range of 500-1,000 mumol.m-2.s-1). Because the state of soil water decided the values of stomatic resistance (RS) and leaf water potential, RS and psi 1 also had influence on the changes of WUE. When RS and psi 1 were respectively 2.0 s.cm-1 and -3.0 MPa, WUE was the highest, but Pn was relatively low, which was not good to the normal growth and fruitage of trees. From the overall consideration of WUE, Pn and Tr, the scopes of RS and psi 1 were 2-6 s.cm-1 and -2.1 approximately -1.65 MPa, respectively, which not only guaranteed the normal photosynthesis of Goldspur, but also benefited the increase of WUE. The scope of the corresponding SWC was 11%-15%, which was equal to 55%-75% of FC and this scope could be used as theoretical index of field water supply for Goldspur. PMID:14733015

Wang, Keqin

2003-09-01

354

Treated wastewater effects on water repellency and soil hydraulic properties of soil aquifer treatment infiltration basins  

NASA Astrophysics Data System (ADS)

SummaryIrrigation with treated wastewater (TWW) has been reported to induce low to moderate hydrophobicity in soils of different texture with or without vegetation cover. Additional potential sites for adverse effects of TWW are infiltration basins, where TWW undergoes tertiary treatment, known as soil aquifer treatment (SAT). The annual organic matter (OM) loads in SAT are a hundred fold higher than those applied in irrigation with TWW. Therefore, we initially presumed that in the sandy soils of SAT infiltration basins, hydrophobicity would be expressed to a higher extent and would further affect the hydraulic properties of these soils. This hypothesis was tested in the Dan Region Wastewater Reclamation Project, Tel-Aviv, Israel. In terms of water drop penetration time (WDPT) test, the results obtained exhibited similar hydrophobicity levels (0 ? WDPT ? 238 s) to those obtained in the TWW irrigated fields and in a similar manner, soil hydrophobicity was only exhibited in the surface soil layer. It is suggested that the low to moderate hydrophobicity obtained under TWW irrigation and recharge into the SAT basins, may primarily stem from the drying and wetting cycle regimes employed. Under these conditions, hydrophobic compounds, which may impart hydrophobicity to the soil particles, are likely to detach and dissolve into the soil solution at the subsequent irrigation or recharge event. Furthermore, the frequent displacement of the resident TWW derived OM by repeatedly flooding events, prevents maturation and humification of the resident OM. Further investigations on the hydraulic properties of the basin soils were conducted in conjunction with the solid-liquid contact angle ( ?) and the surface tension ( ?L) of the soil solution. The results obtained imply that the dependence of the hydraulic properties on ? and/or ?L, can be attributed to the hydrophobic nature of both the solid and dissolved OM originating from the recharged TWW.

Arye, Gilboa; Tarchitzky, Jorge; Chen, Yona

2011-01-01

355

Water content dependence of trapped air in two soils  

Microsoft Academic Search

An improved air pycnometer method was used to examine the water content dependence of trapped-air volumes in two repacked, nonswelling soils. Trapped-air volumes were determined at a series of hydrostatic equilibrium stages which were attained during water pressure-controlled wetting and drying cycles over a range of 0 to ?10 kPa for a sand and 0 to ?20 kPa for a

David A. Stonestrom; Jacob Rubin

1989-01-01

356

Plant Response to Differential Soil Water Content and Salinity  

NASA Astrophysics Data System (ADS)

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

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

2011-12-01

357

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

Microsoft Academic Search

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

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

2001-01-01

358

Wave propagation in marine sediments and water saturated soils  

Microsoft Academic Search

Summary A unification of the theories of Biot and Weiskopf has been made to form the suitable equations of motion for porous water saturated soils and marine sediments. It has been shown that the velocities of the body waves depend on the direction of propagation. In the vertical direction there are three, one distortional and two dilatational waves. In the

S. K. Bose

1962-01-01

359

Wave propagation in marine sediments and water saturated soils  

Microsoft Academic Search

A unification of the theories of Biot and Weiskopf has been made to form the suitable equations of motion for porous water saturated soils and marine sediments. It has been shown that the velocities of the body waves depend on the direction of propagation. In the vertical direction there are three, one distortional and two dilatational waves. In the horizontal

S. K. Bose

1962-01-01

360

Salix vegetation filters for purification of waters and soils  

Microsoft Academic Search

During recent years it has become obvious that it is both environmentally and economically appropriate to use vegetation filters of short rotation willows (Salix spp.) to purify waters and soils. Swedish and Polish experiences of vegetation filter efficiencies have been demonstrated in several laboratory, field lysimeter and full-scale experiments. However, there are still many questions to be answered; for example,

K. L. Perttu; P. J. Kowalik

1997-01-01

361

ANIMAL WASTE EFFECTS UPON CROP PRODUCTION, SOIL AND RUNOFF WATERS  

EPA Science Inventory

This investigation was initiated to study the effects of application of differing rates of manure to land on crops, soil, and runoff water. The study was conducted under field conditions in the sub-humid climate of the Northern Great Plains. Manure application rates included leve...

362

External exposure to radionuclides in air, water, and soil  

SciTech Connect

Federal Guidance Report No. 12 tabulates dose coefficients for external exposure to photons and electrons emitted by radionuclides distributed in air, water, and soil. The dose coefficients are intended for use by Federal Agencies in calculating the dose equivalent to organs and tissues of the body.

Eckerman, K.F.; Ryman, J.C.

1996-05-01

363

SOIL AND WATER QUALITY MANAGEMENT THROUGH VETIVER GRASS TECHNOLOGY  

Microsoft Academic Search

Soil quality and water quality are concepts related with the functions of these natural resources within the environment. Indicators and indexes can be linked with standards for the multiple uses of these resources and can be used as guides for land use and land management planning, from the field to the watershed levels. The design of a resource management system

Oscar S. Rodríguez

364

GIS IN SOIL & WATER SCIENCE Distance Education Sections  

E-print Network

. COURSE OBJECTIVES: To provide students with the basic concepts of geographic information systemsSWS 4720C GIS IN SOIL & WATER SCIENCE Distance Education Sections Fall 2013 Instructor Susan Curry, no technical help for setup/debugging problems will be provided by the instructor. PREREQUISITES: Basic

Ma, Lena

365

GIS IN SOIL & WATER SCIENCE On-Campus Section 8197  

E-print Network

: To provide students with the basic concepts of geographic information systems and applications focusedSWS 4720C GIS IN SOIL & WATER SCIENCE On-Campus Section 8197 Fall 2013 Instructor Susan Curry will be provided by the instructor. #12;PREREQUISITES: Basic knowledge in Windows operating system and high

Ma, Lena

366

Laboratory measurements of electrical resistivity versus water content on small soil cores  

NASA Astrophysics Data System (ADS)

The assessment of soil water content variations more and more leans on geophysical methods that are non invasive and that allow a high spatial sampling. Among the different methods, DC electrical imaging is moving forward. DC Electrical resistivity shows indeed strong seasonal variations that principally depend on soil water content variations. Nevertheless, the widely used Archie's empirical law [1], that links resistivity with voids saturation and water conductivity is not well suited to soil materials with high clay content. Furthermore, the shrinking and swelling properties of soil materials have to be considered. Hence, it is relevant to develop new laboratory experiments in order to establish a relation between electrical resistivity and water content taking into account the rheological and granulometrical specificities of soil materials. The experimental device developed in IRD laboratory allows to monitor simultaneously (i) the water content, (ii) the electrical resistivity and (iii) the volume of a small cylindrical soil core (100cm3) put in a temperature controlled incubator (30°C). It provides both the shrinkage curve of the soil core (voids volume versus water content) and the electrical resistivity versus water content curve The modelisation of the shrinkage curve gives for each moisture state the water respectively contained in macro and micro voids [2], and then allows to propose a generalized Archie's like law as following : 1/Rs = 1/Fma.Rma + 1/Fmi.Rmi and Fi = Ai/(Vi^Mi.Si^Ni) with Rs : the soil resistivity. Fma and Fmi : the so called "formation factor" for macro and micro voids, respectively. Rma and Rmi : the resistivity of the water contained in macro and micro voids, respectively. Vi : the volume of macro and micro voids, respectively. Si : the saturation of macro and micro voids, respectively. Ai, Mi and Ni : adjustment coefficients. The variations of Rmi are calculated, assuming that Rma is a constant. Indeed, the rise of ionic concentration in water may be neglected during the sewage of macro voids as it corresponds to a small quantity of water for the studied samples. Soil solid components are generally electrical insulators, the conduction of electrical current only lies on two phenomenon occurring in water : (i) volume conduction controlled by the electrolyte concentration in water and the geometrical characteristics of macro voids network ; (ii) surface conduction controlled by the double diffuse layer that depends on the solid-liquid interactions, the specific surface of clay minerals and the geometry of particles contacts. For the water contained in macro voids the preeminent phenomenon seems to be volume conduction while for the water contained in micro voids, it seems to be surface conduction. This hypothesis satisfyingly explains the shape of the electrical resistivity versus water content curves obtained for three different oxisols with clayey, clayey-sandy and sandy-clayey texture. [1] Archie G.E. 1942. The electrical resistivity log as an aid in determining some reservoirs characteristics. Trans. AIME, 146, 54-67. [2] Braudeau E. et al. 1999. New device and method for soil shrinkage curve measurement and characterization. S.S.S.A.J., 63(3), 525-535.

Robain, H.; Camerlynck, C.; Bellier, G.; Tabbagh, A.

2003-04-01

367

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

NASA Astrophysics Data System (ADS)

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

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

2009-04-01

368

Effects of corn stalk orientation and water content on passive microwave sensing of soil moisture  

NASA Technical Reports Server (NTRS)

A field experiment was conducted utilizing artificial arrangements of plant components during the summer of 1982 to examine the effects of corn canopy structure and plant water content on microwave emission. Truck-mounted microwave radiometers at C (5 GHz) and L (1.4 GHz) band sensed vertically and horizontally polarized radiation concurrent with ground observations of soil moisture and vegetation parameters. Results indicate that the orientation of cut stalks and the distribution of their dielectric properties through the canopy layer can influence the microwave emission measured from a vegetation/soil scene. The magnitude of this effect varies with polarization and frequency and with the amount of water in the plant, disappearing at low levels of vegetation water content. Although many of the canopy structures and orientations studied in this experiment are somewhat artificial, they serve to improve understanding of microwave energy interactions within a vegetation canopy and to aid in the development of appropriate physically based vegetation models.

Oneill, P. E.; Blanchard, B. J.; Wang, J. R.; Gould, W. I.; Jackson, T. J.

1984-01-01

369

Groundwater-surface water interactions in fractured Mediterranean mountain environments  

NASA Astrophysics Data System (ADS)

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

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

2014-05-01

370

Comparison of methods for estimating maximum soil water content for optimum workability  

Microsoft Academic Search

Tillage causes changes to soil structure, and if the soil is too wet when tillage is performed, the change to the soil structure will be detrimental. A methodology that could be used for estimating the maximum gravimetric soil water content for optimum tillage would be helpful to prevent soil structural damage. The objective of this study was to compare five

Lothar Mueller; Uwe Schindler; Norman R Fausey; Rattan Lal

2003-01-01

371

Seasonal variation of soil physical properties under different water managements in irrigated rice  

Microsoft Academic Search

While soil porosity and soil hydrological properties are key characteristics that define different soil types, they are influenced by many factors: land use, tillage management, and agricultural practices such as irrigation. As expected, water management impacts the physical properties of soil in irrigated rice significantly; however, the importance of seasonal variation on those soil properties requires further consideration, especially given

Dario Sacco; Cassiano Cremon; Laura Zavattaro; Carlo Grignani

372

The Dual Gravimetric Hot-Air Method for Measuring Soil Water Diffusivity  

Microsoft Academic Search

The hot-air method provides rapid measurement of a soil's unsatu- rated hydraulic diffusivity function. The original method consists of blowing hot air across one end of a soil column for a short period, and then quickly extruding, dissecting, and oven drying the soil to provide the soil water content profile, which is used to calculate the soil's un- saturated hydraulic

J. S. Tyner; L. M. Arya; W. C. Wright

2006-01-01

373

Water uptake of barley roots from rhizospheric soil solutions of different salt concentrations  

Microsoft Academic Search

Roots absorbing water from saline soils cause the rapid accumulation of soluble salts in the soil in close vicinity of the roots (rhizospheric soil). Thus the roots are in contact with a soil solution which is often several times more concentrated than that to be expected from average soil solution data. This paper describes a simple method to determine the

U. Schleiff

1983-01-01

374

Linkages between forest soils and water quality and quantity Daniel G. Neary a,  

E-print Network

the stability of soil aggregates. Stable aggregates prevent soil crusting by reducing detachment of small soil ecosystems. The biological, chemical, and physical characteristics of forest soils are particularly wellLinkages between forest soils and water quality and quantity Daniel G. Neary a, *, George G. Ice b

375

Lithium/water interactions: Experiments and analysis  

SciTech Connect

The interaction of molten-lithium droplets with water is studied experimentally. In one set of experiments, droplets of [approximately]10- to 15-mm diameter are injected into a vessel filled with water. The reaction is filmed, and pressure measurements are made. The initial metal and water temperatures range from 200 to 500[degrees]C and 20 to 70[degrees]C, respectively. It is found that when reactant temperatures are high, an explosive reaction often occurs. When the initial lithium temperature is >400[degrees]C and the water is >30[degrees]C, the explosive reactions become much more probable, with pressure peaks as high as 4 MPa. The reaction is modeled to explain the temperature threshold for this metal-ignition phenomena. Results with the model support the hypothesis that explosive reactions occur when the lithium droplet surface reaches its saturation temperature while the hydrogen film surrounding the drop is relatively thin. A second set of experiments measures the reaction rate of nonexplosive lithium-water reactions. The test geometry parallels that of the previous experiments, and the reactant temperature combinations are deliberately kept below the observed ignition threshold. Two separate methods are used to determine the reaction rate in each test: One uses a three-color pyrometer to measure the drop temperature as the lithium rises through the water, while the other consists of a photographic technique that measures the amount of hydrogen generated. Measured reaction rates range from [approximately]10 to 50 mol/s[center dot]m[sup 2] with good agreement between the two measurement techniques. The data do not show any significant variation in the reaction rate as a function of either the initial water or initial lithium temperature. 17 refs., 15 figs.

Lomperski, S.; Corradini, M.L. (Univ. of Wisconsin, Madison, WI (United States))

1993-08-01

376

Effects of spatial variability of soil hydraulic properties in water budget modeling  

Microsoft Academic Search

There is appreciable spatial variability of soil properties on the scale of a watershed or a field even in a single soil type. The spatial variation of soil water characteristics in an area was simulated from average properties and the assumption of scale heterogeneity (Philip, 1967). Simulated soil water characteristics and other data representing forest vegetation were used in a

A. J. Peck; R. J. Luxmoore; Janice L. Stolzy

1977-01-01

377

The Utility of Surface Temperature Measurements for the Remote Sensing of Surface Soil Water Status  

Microsoft Academic Search

Experiments carried out on an Avondale loam soil indicated that the thermal inertia concept of soil water content detection is reasonably sound. The volumetric water contents of surface soil layers between 2 and 4 cm thick were found to be linear functions of the amplitude of the diurnal surface soil temperature wave for clear day-night periods. They were also found

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

1975-01-01

378

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

Microsoft Academic Search

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

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

1997-01-01

379

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

Microsoft Academic Search

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

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

2005-01-01

380

Microbial activity in response to water-filled pore space of variably eroded southern Piedmont soils  

Microsoft Academic Search

Potential C and N mineralization and soil microbial biomass C (SMBC) are soil biological properties important in understanding nutrient and organic matter dynamics. Knowledge of soil water content at a matric potential near field capacity is needed to determine these biological properties. The objective of this study was to examine whether adjustment of soil water content to a common level

A. J. Franzluebbers

1999-01-01

381

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

ERIC Educational Resources Information Center

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

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

382

Soil Microbial Properties and Plant Growth Responses to Carbon and Water Addition in a Temperate Steppe: The Importance of Nutrient Availability  

PubMed Central

Background Global climatic change is generally expected to stimulate net primary production, and consequently increase soil carbon (C) input. The enhanced C input together with potentially increased precipitation may affect soil microbial processes and plant growth. Methodology/Principal Findings To examine the effects of C and water additions on soil microbial properties and plant growth, we conducted an experiment lasting two years in a temperate steppe of northeastern China. We found that soil C and water additions significantly affected microbial properties and stimulated plant growth. Carbon addition significantly increased soil microbial biomass and activity but had a limited effect on microbial community structure. Water addition significantly increased soil microbial activity in the first year but the response to water decreased in the second year. The water-induced changes of microbial activity could be ascribed to decreased soil nitrogen (N) availability and to the shift in soil microbial community structure. However, no water effect on soil microbial activity was visible under C addition during the two years, likely because C addition alleviated nutrient limitation of soil microbes. In addition, C and water additions interacted to affect plant functional group composition. Water addition significantly increased the ratio of grass to forb biomass in C addition plots but showed only minor effects under ambient C levels. Our results suggest that soil microbial activity and plant growth are limited by nutrient (C and N) and water availability, and highlight the importance of nutrient availability in modulating the responses of soil microbes and plants to potentially increased precipitation in the temperate steppe. Conclusions/Significance Increased soil C input and precipitation would show significant effects on soil microbial properties and plant growth in the temperate steppe. These findings will improve our understanding of the responses of soil microbes and plants to the indirect and direct climate change effects. PMID:22496905

Guo, Chengyuan; Wang, Renzhong; Xiao, Chunwang

2012-01-01

383

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

E-print Network

for the debre~ of MASTER OF SCIFNCE May 19G9 Major Subject: Range Science LEAF WATER POTENTIAL IN P2'NUS TAEDA L. AS RELATED TO FLUCTUATING SOIL WATER AND ATMOSPHERIC CONDITIONS A Thesis by STANLEY LEE ELLISON Approved as to style and content by...: (Chairman of Committee) (Head o D partment) Member) e er) May l969 ABSTRACT Leaf Water potential in pinus trreda L. as Related to Fluctuating Soil Water and Atmospheric Conditions (May 1969) Stanley Lee Ellison, B. S. , Texas A&M University Directed...

Ellison, Stanley Lee

2012-06-07

384

Modeling of soil water content and soil temperature at selected U.S. and central European stations using SoilClim model  

Microsoft Academic Search

Within the presented study the SoilClim model was tested through various climatic and soil conditions. SoilClim model enables to estimate reference and actual evapotranspiration from defined vegetation cover and consequently the soil water content within two defined layers (named as Moisture control section I and II) could be deduced. The soil temperature in 0.5 m depth is also estimated (on

P. Hlavinka; M. Trnka; J. Balek; Z. Zalud; M. Hayes; M. Svoboda; J. Eitzinger

2009-01-01

385

Seismic Soil-Foundation-Structure Interaction in Urban Environments  

NASA Astrophysics Data System (ADS)

The interactions between a structure, its foundation, and the surrounding soil during an earthquake are referred to as soil-foundation-structure interaction (SFSI). The interactions between multiple structures, and their foundations, through the surrounding soil are collectively known as structure-soil-structure interaction (SSSI). Modern design codes in use in the United States, and abroad, provide guidance for considering SFSI during the seismic design of structural systems. However, these same codes do not provide any guidance for considering SSSI. This situation is a direct result of the current paucity of research into the effects of SSSI on structural performance. This dissertation describes the results of four centrifuge experiments designed to study the influence of SSSI on the seismic performance of building-foundation systems. Following these experiments, numerical models were developed and their efficiency at reproducing measured response evaluated. The experimental program involved two pairs of tests. During Test-1 and Test-2, the SFSI and SSSI-influenced responses of two three-dimensional inelastic frame structures were recorded. During Test-3 and Test-4, the interactions between an inelastic frame structure and an elastic rocking wall arranged in a variety of orientations were recorded. In each of the pair of test series, one configuration was devoted to the evaluation of the response of the model frame structures far from any neighboring structure. Ultimately, the experimental results demonstrate that when structures are placed next to each other, the seismic demands in inelastic frame structures can increase. As such, seismic structural performance may be negatively impacted by SSSI. The tests reveal that footings of buildings placed nearest to other buildings can be physically restrained when loaded towards the other building -- a physical mechanism that had not previously been observed. This asymmetrical physical restraint resulted in a stiffened hysteretic response of footings nearest to adjacent buildings and nominal increases in seismic demands to superstructure elements. It is also demonstrated that wave-based analytical solutions to the SSSI problem alone are not adequate for modeling the interactions between building-foundation systems with highly nonlinear foundation responses. During the numerical phase of this research, available tools for modeling SFSI effects (i.e., absent the effects of neighboring structures) in OpenSees were first refined. The shallowFoundationGen command was redeveloped to give the user greater flexibility. Subsequently, it was demonstrated that the updated modeling technique provides an adequate means to model the experimentally observed coupling of the vertical footing force and overturning moment load combinations for shallow foundations attached to inelastic frame structures. Finally, an available methodology for modeling wave-based SSSI effects was implemented in OpenSees and its capability to predict the experimentally measured seismic demands of an SSSI-influenced inelastic structure was evaluated. Ultimately, it is concluded that the use of foundation-to-foundation connection springs, which are based on wave-based solutions, is insufficient for capturing the seismic response of adjacent structures with highly nonlinear individual SFSI responses.

Trombetta, Nicholas Wade

386

Effect of temperature and water on gaseous emissions from soils treated with animal slurry  

SciTech Connect

Microbial respiration and denitrification are greatly affected by abiotic factors, but they are difficult to assess in natural environments. Under controlled conditions the interactions between temperature and soil water content on microbial respiration, N{sub 2}O production, and denitrification in soil amended with animal slurries were studied. The effects of the abiotic factors on the biological processes were monitored for 8 wk in repacked soil cores amended with pig or cattle slurry. The soil cores were incubated at 43, 57, and 72% water-filled pore space (WFPS) and at 10, 15, and 20 C with or without addition of 10% acetylene. The amount of N{sub 2}O lost at 72% WFPS corresponded to 8 to 22% of the slurry's NH{sub 4}{sup +} content, but for only 0.01 to 1.2% at 43 to 57% WFPS. The amount of available C accounted for by denitrification was 8 to 16% of total respiration at 72% WFPS, but only 0.03 to 0.4% at 43 to 57% WFPS. Both N{sub 2}O production and denitrification peaked earlier in the cattle-slurry treated soil than in the pig-slurry treated soil, whereas the total N loss was greatest from the latter. Neither amendments nor soil water contents seemed to affect the Q{sub 10}-values for the CO{sub 2} production, resulting in values between 1.6 and 2.6. At 72% WFPS, N{sub 2}O production and denitrification had Q{sub 10}-values ranging between 3.3 and 5.4. High temperatures enhanced both aerobic respiration and denitrification, and aerobic respiration further enhanced denitrification by consuming oxygen, resulting in strong sensitivity of denitrification to temperature.

Maag, M.; Vinther, F.P.

1999-08-01

387

Arsenic Enrichment in Surface Water and Soil in Tibetan Plateau  

NASA Astrophysics Data System (ADS)

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

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

2008-12-01

388

Subcritical water extraction to isolate kinetically different soil nitrogen fractions  

NASA Astrophysics Data System (ADS)

Soil organic N is largely composed of inherently biologically labile proteinaceous N and its persistence in soil is mainly explained by stabilization through binding to minerals and other soil organic matter (SOM) components at varying strengths. In order to separate kinetically different soil N fractions we hypothesize that an approach which isolates soil N fractions on the basis of bonding strength is required, rather than employing chemical agents or physical methods. We developed a sequential subcritical water extraction (SCWE) procedure at 100, 150 and 200 °C to isolate SOM fractions. We assessed these SCWE N fractions as predictors for aerobic and anaerobic N mineralization measured from 25 paddy soil cores in incubations. SCWE organic carbon (SCWE OC) and N (SCWE N) increased exponentially with the increase of temperature and N was extracted preferentially over OC. The efficiency of SCWE and the selectivity towards N were both lower in soils with increasingly reactive clay mineralogy. Stepwise linear regression found no relations between the SCWE fractions and the anaerobic N mineralization rate but instead with pH and a model parameter describing the temperature dependency of SCWE extraction. Both were linked to texture, mineralogy and content of pedogenic oxides, which suggests an indirect relation between anaerobic NH4+ release and these edaphic soil factors. N mineralization appeared to be largely decoupled from SOM quantity and quality. From the present study on young paddy soils low in pedogenic oxides and with high fixed NH4+ content we cannot infer the performance of SCWE to isolate bio-available N in more developed upland soils. There may be potential to separate kinetically different SOM pools from upland soils because 1° for aerobic N mineralization at 100-150 °C SCWE N was the best predictor; and 2° SCWE selectively extracted N over C and this preference depended on the mineralogical composition. Hence N fractions differing in bonding strength with minerals or SOM might be isolated at different temperatures, and specifically this association has frequently been found a prominent stabilization mechanism of N in temperate region cropland soils.

Sleutel, S.; Kader, M. A.; Demeestere, K.; Walgraeve, C.; Dewulf, J.; De Neve, S.

2013-11-01

389

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

USGS Publications Warehouse

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

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

2007-01-01

390

Biological and chemical interactions of pesticides with soil organic matter.  

PubMed

There is little doubt that organic matter plays a major role in the binding of pesticides in soil, and that this phenomenon is usually the most important cause for interaction of pesticides in the soil environment. Fulvic or humic acids are the chemicals most commonly involved in the binding interactions. Binding can occur with the original pesticide or a transformation product, the reaction being caused by abiotic agents or biotic agents (microbial or plant enzymes). The reactions or processes involved appear to be the same as those responsible for the formation of humic substances, i.e. for the humification process. Binding of pesticides to organic matter can occur by sorption (Van der Waal's forces, hydrogen bonding, hydrophobic bonding), electrostatic interactions (charge transfer, ion exchange or ligand exchange), covalent bonding or combinations of these reactions. Our investigation focused primarily on the binding of substituted phenols and aromatic amines to humus monomers and humic substances. In model reactions, we demonstrated the formation of covalent linkages between pesticides and humus constituents and fulvic or humic acids in the presence of phenol oxidases or clay minerals. With chlorinated phenols and carboxylic acids, it was possible to isolate and identify cross-coupling products and to elucidate the site and type of binding. The binding of chlorinated phenols to humic substances was determined by using 14C-labelled chemicals and by measuring the uptake of radioactivity by the humic material. These experiments provide a base for explaining the formation of bound residues in certain cases and for assuming the toxic potential of the immobilized pollutants. PMID:1439732

Bollag, J M; Myers, C J; Minard, R D

1992-08-12

391

Occurrence, fate, and persistence of gemfibrozil in water and soil.  

PubMed

Pharmaceuticals and personal care products (PPCPs) have emerged as a group of potential environmental contaminants of concern. The occurrence of gemfibrozil, a lipid-regulating drug, was studied in the influent and effluent at a wastewater treatment plant (WWTP) and groundwater below a land application site receiving treated effluent from the WWTP. In addition, the sorption of gemfibrozil in two loam soils and sand was assessed, and biological degradation rates in two soil types under aerobic conditions were also determined. Results showed that concentrations of gemfibrozil in wastewater influent, effluent, and groundwater were in the range of 3.47 to 63.8?µg/L, 0.08 to 19.4?µg/L, and undetectable to 6.86?µg/L, respectively. Data also indicated that gemfibrozil in the wastewater could reach groundwater following land application of the treated effluent. Soil-water distribution coefficients for gemfibrozil, determined by the batch equilibrium method, varied with organic carbon content in the soils. The sorption capacity was silt loam?>?sandy loam?>?sand. Under aerobic conditions, dissipation half-lives for gemfibrozil in sandy loam and silt loam soils were 17.8 and 20.6 days, respectively; 25.4 and 11.3% of gemfibrozil was lost through biodegradation from the two soils over 14 days. PMID:22180293

Fang, Yu; Karnjanapiboonwong, Adcharee; Chase, Darcy A; Wang, Jiafan; Morse, Audra N; Anderson, Todd A

2012-03-01

392

Maize canopies under two soil water regimes  

Microsoft Academic Search

The feasibility of determining at 5-min intervals the fluxes of water vapor and CO2 using a Bowen ratio\\/energy balance\\/CO2 gradient (BREB+) apparatus was studied. Details of the BREB+ apparatus are given. The results obtained over maize canopies at the short 5-min signal averaging time are examined in several aspects. One aspect is the fact that on days when net radiation

Pasquale Steduto; Theodore C. Hsiao

1998-01-01

393

Water repellency and soil moisture variations under Rosmarinus officinalis in a burned soil  

Microsoft Academic Search

Mediterranean semi-arid landscapes are characterised by the patchiness of the vegetation cover, in which variations in the distribution pattern of soil water repellency (SWR) can be of major importance for their hydrological and geomorphological effects in burned areas, and also for their ecological implications concerning to the re-establishment of their plant cover. Within a broader research framework, the present work

E. Gimeno-García; J. A. Pascual-Aguilar; J. Llovet

2009-01-01

394

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

NASA Astrophysics Data System (ADS)

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

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

2010-05-01

395

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

E-print Network

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

Florida, University of

396

Modeling of molten metal/water interactions  

SciTech Connect

A theoretical model has been developed for molten metal/water interactions by using a semiempirical heat transfer correlation and a mass transfer analogy to predict the metal ignition threshold temperatures for aluminum and zirconium. The predictions of the aluminum and zirconium metal temperature responses are studied to identify self-propagating chemical reactions that lead to metal ignition for various metal particle sizes and initial temperatures. The results showed that the ignition of the aluminum metal is possible when the aluminum oxide layer remains in the liquid phase until the metal temperature reaches its oxide layer solidification temperature under highly transient conditions. For both metals, the ignition temperature increased with a larger size of the metal particle, with zirconium requiring qualitatively larger temperatures for ignitions. It was observed that the effect of the water temperature strongly depends on where the chemical reaction front may actually be located.

Uludogan, A.; Corradini, M.L. [Univ. of Wisconsin, Madison, WI (United States). Dept. of Nuclear Engineering and Engineering Physics

1995-02-01

397

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

E-print Network

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