Brief Summary of Minutes of Annual Meeting

Minutes:The annual meeting was held at the Circus Circus Hotel & Casino Las Vegas, NV January 3-5, 2005. Chairperson Yan Jin called the meeting to order and reviewed the previous year's annual report. Allen Mitchell (AA) gave the administrtive report including the renewal of the project through 09/30/2009. Ray Knighton gave the the CSREES representative's report. The W1188 business meeting followed where the 2004 annual report was approved unanimously. Scott Bradford USDA-ARS USSL was elected secretary for 2005. Next year's meeting was discussed and the membership voted to hold it at the Desert Research Institute (Accomodations at the Hard Rock Hotel and Casino). Technical presentation followed the morning coffee break. A total of 35 presentation were made on the three objectives of the 1999-2004 project outline. The presentations covered all aspects of the project including: geochemical modeling using the HYDRUS software, preferential flow and transport, water repellency, vadose zone flow and transport spatial and time scales, soil microbial biophysics, methodology of soil heat flux measurement, TDR calibration, relationship between soil anisotropy coefficient and saturation, infiltration into a layered soil with structured one-deminsional heterogeneity for binary or a tertiary system, improved hydraulic funtions of structured soils, soil hydromechanics, soil dialectric measurements, universal scaling law for soil water retention curves,and at low water contents, and other vadose zone models. The committee also presnted new instrumentation and methodologies for the study of soil flow and transport characteristics including a multifunctional heat probe for simultaneous measurement of water heat and solute transport, introduction of root zone water quality model, GPFARM and whole farm decision support system, IFARM DSS, and modification of tension infiltrometers to measure low flow rates. A complete set of minutes is attached.

Objective 1: To study relationships between flow and transport properties or processes and the spatial and temporal scales at which these are observed: Researchers at the USDA-Salinity Lab (USDA-USSL) addressed processes governing colloid transport and retention in water saturated, physically heterogeneous systems. Colloid transport studies were conducted in water saturated physically heterogeneous systems to gain insight into the processes controlling transport in natural aquifer and vadose zone (variably saturated) systems. Modeling of the transport data indicated that straining was sometimes an important mechanism of colloid retention. Colloid retention in the heterogeneous systems was also influenced by spatial variations in the pore water velocity. The straining model typically provided a better description of the effluent and retention data than the attachment model, especially for larger colloids and finer-textured sands. Consistent with previously reported findings, straining occurred when the ratio of the colloid and median grain diameters was greater than 0.5%. In another project, USDA-USSL researchers worked on processes governing fate and transport of Cryptosporidium oocysts in saturated porous media. Accurate knowledge of the transport and deposition behavior for pathogenic Cryptosporidium parvum oocysts is needed to assess contamination and protect water resources. A physically realistic description of the data was obtained by modeling attachment, detachment, and straining. Dramatic differences in the predicted oocyst breakthrough curves were observed at greater transport distances for the various model formulations. At UC-Riverside, work was conducted on nitrogen best management practices (BMPs) for fertilizing turfgrass. Slow-release N and water soluble, fast-release N was applied at the same three rates. Several preliminary observations are: 1.Minimalist irrigation reduces the potential for nitrate leaching. However, sufficient irrigation is needed to promote healthy turfgrass. 2.An annual N rate of 4 to 6 lb/1000 ft2 produces an acceptable to good quality tall fescue lawn. Higher rates are not necessary and increase the risk of nitrate leaching. 3. Slow-release N sources (Nutralene, Milorganite, and Polyon) cause less nitrate leaching than a fast-release N source (ammonium nitrate). 4. The amount of nitrate leaching from a fast-release N source can be drastically reduced if N rates of individual applications do not exceed 1.5 lb/1000 ft2. UC-Riverside was also involved in a nursery runoff study. Because many nurseries are situated in urban environments, nursery runoff generally enters nearby streams and eventually enters large creeks or ocean estuaries. The overall purpose of this project is to prevent contamination of coastal waters from runoff from production nurseries. This will be achieved through the following objectives: (1) to minimize irrigation runoff from agricultural properties. This would allow growers to comply with the Basin Plan Objectives, Clean Water Act requirements, and future TMDL requirements from those currently in progress. (2) to reduce inputs to irrigation water, improve irrigation/fertilizer use efficiency, and reduce the potential of runoff that contributes to the non-point source pollution problems in the area; (3) to demonstrate effectiveness of BMPs and improved technologies in reducing runoff and leaching; and (4) To extend information gleaned from the project to growers in the Region as well as in the state. UC-Davis looked at the parameterization of large-scale hydrology models that may be hampered by the tremendous spatial heterogeneity of the subsurface, as well as the spatial and temporal variations in boundary conditions. An example of this approach is the Shuffled Complex Evolution Metropolis global optimization algorithm, SCEM-UA. It presents the multi-criteria calibration of a regional distributed subsurface water flow model for a 1,400 km2 irrigated agricultural area in the western San Joaquin Valley of California. Model parameters that were subjected to calibration included irrigation efficiency, effective drain depth and conductance, crop evapotranspiration correction coefficient, saturated hydraulic conductivity and specific yield values of coarse and fine fractions, and saturated hydraulic conductivity values defining water fluxes. There is a general lack of experiments that study the effects of soil structure and pore space characteristics on air and water permeability. Measurements showed large differences between disturbed and undisturbed samples, confirming the enormous impact of soil structure and pore space characteristics on flow. Regardless of soil disturbance, the researchers showed that the tortuosity/connectivity parameter, for the water permeability and air permeability were different. At Iowa State University, several studies were conducted. Through nondestructively monitoring coupled heat and water transfer in laboratory soil columns during a series of experiments, the researchers expect to gain insight into the coupled processes in unsaturated soils. Preliminary tests on Hanlon sand indicate that the new heat exchangers are able to establish and maintain desired temperature gradients with minimum heat loss from the soil columns. Scientists at Montana State University were active in a project where the focus was on microbial biophysics. Desaturation of soils results in fragmentation of aqueous soil microbial habitats, and increased tortuosity of liquid phase nutrient and metabolite mass transfer via diffusion. Montana State University and the University of Connecticut are collaborating on experimental and theoretical aspects of research to quantify the impacts of pore-scale physical conditions on soil microbial activities. Flat surfaces having matric potential-dependent-thickness water films were contrasted to grooves that remained water-filled at both matric potentials, thus creating a contrast in diffusion potential. Extensive areas (multiple locations and depth slices) of flat sections and grooves were included, for replicate coupons. Both Yellowstone National Park (Ragged Hills) soil and positive control Pseudomonas aeruginosa inocula produced relatively high cell densities for flat surfaces and grooves at -0.5 cm matric potential, while cell densities were much lower for flat surfaces than for grooves at -5 cm. This is consistent with expected similar diffusion potentials for both regions at the very wet -0.5 cm level, but lower diffusion potential in flat regions having only thin water films than for the still water-filled grooved regions at -5 cm matric potential. At North Dakota State University, field and laboratory studies were conducted related to the fate and transport of manure-borne hormones. The sorption, transformation, and mobility of two reproductive hormones, 17b-estradiol and testosterone have been studied in both field and laboratory settings. Both 17b-estradiol and testosterone are naturally present in animal manures and can be found in manures at concentrations that are potentially detrimental to aquatic organisms. Field experiments using lysimeters identified the fate of natural occurring 17b-estradiol and testosterone in manures. Subsurface water was analyzed for hormones beneath plots treated with hog lagoon material, raw manure, and compost materials. Hormones were detected at 0.6 m depth at concentration that may cause endocrine disruption. Hormones associated with the manure plots were at the lowest concentrations, while hormone concentrations found in the control plot were found to be highest. This result provided information that these compounds are antecedently present in the environment. Also, manures facilitate the degradation of hormones. The same research group at North Dakota State University worked on study on fate and transport of dioxins in soil-water systems. Dioxins are toxins that are produced from low-temperature combustion usually from anthropogenic sources, but can be produced from natural forest fires. They enter the ecosystem and little is know about the fate and transport of these potent chemicals in the soil. The three dioxin isomers that were used were nontoxic and behaved as true dioxins in the soil. These compounds were found to be strongly sorbed to soils and the strength of sorption was correlated to the organic matter content of the soil. If these chemicals can be transported to the lower depths of soil and if they are persistent; then the probability of subsurface water contamination increases. Experimental results can improve the understanding of contamination of surface and subsurface water and soil by these chemicals. Also, it can improve the remediation technologies used to clean contaminated areas. At the University of Minnesota, research emphasis was on analytic element modeling of two-dimensional, steady-state unsaturated flows. The analytic element method was applied to the solution of the steady-state Richards equation, transformed into the modified Helmholz equation using the Kirchhoff transformation and a space variable transformation. Results appeared to show that the analytic element solution is more accurate than the finite element solution. The finite element solution will also be used in 2005 to analyze the assumptions made in deriving the modified Helmholz equation. Colorado State University researchers conducted experimental studies that continue to investigate fundamental understanding of soil water hysteresis. Studies are focused on i) resolving an apparent relationship between wetting function parameters and degree of saturation, and ii) clarifying non-equilibrium effects in structured and non-structured soil. Utah State University participated within a project related to the effects of reduced gravity on porous media physical properties. Follow up imbibition experiments and novel water retention and saturated hydraulic conductivity experiments in different porous media were conducted. Experiments occurred during the 20 seconds of microgravity provided by the KC-135s parabolic flight. Experimental observations of measured water content and matric potential showed dynamic response to the parabolic flight. Reduced matric potentials compared to 1-g measurements were observed in a number of different porous media. Saturated hydraulic conductivity measurements were also carried out revealing no differences between Ks values at varying gravity levels except where density was reduced allowing significant quantities of free-floating particles. These data will provide valuable insight to advance the understanding of porous media soil physics in extra-terrestrial environments such as the International Space Station, the Moon or Mars. PNNL is developing better ways to assess the saturation dependent anisotropy of the hydraulic conductivity function. Soil anisotropy has been found to be a key in properly simulating flow and transport at the Hanford Site, where layered soils dominate the subsurface. The results show that the anisotropy coefficient, A, is independent of soil water retention properties. The model was tested using directional measurements of unsaturated hydraulic conductivity of undisturbed soil cores. Results show that the TCT model can describe different types of soil anisotropy, previously ignored in other models. Research at the University of Delaware has been centered on fate and transport of colloids (including viruses and other types of colloids) in porous media. Preliminary x-ray microtopography analysis suggests that viruses bypassed reaction sites in the matrix due to preferential flow heterogeneous medium (mixed glass beads), examination of the mechanisms responsible for deposition and transport of amphiphilic colloids with a wide range of particle sizes (20  420 nm) through variably saturated porous media. Results showed that decreasing water saturation enhanced colloid immobilization. This study highlights the importance of including size effect and surface properties in modeling or predicting deposition during transport of polydispersive colloids that often occur in natural environments, and investigation of the mechanisms of colloid retention on the air-water interface and air-water-solid interface at the pore scale. At Washington State University (WSU) the focus this year was on (1) studying colloid fate and transport in saturated and variably-saturated sediments, (2) synthesis and characterization of colloids formed under hyperalkaline conditions, (3) determining temporal dynamics of hydraulic conductivities in natural soils as affected by management practices. Using thermodynamic considerations the researchers showed that colloids likely attach to the solid-liquid-gas interface rather than the liquid-gas interface. In collaboration with the University of Delaware a study was initiated to compare the effects of a conservation tillage and chemical fallow on soil temperature and moisture regimes. Measured near-surface soil temperatures under conservation tillage were several degrees lower than under chemical fallow, but the chemical fallow plot stored the same or more water than the conservation tillage plot, reflecting the different characteristics of the two cropping systems. SHAW can be an effective modeling tool for evaluating the effects of cropping systems on soil temperature and water distributions. This information will help in the design of clean-up strategies for contamination at the Hanford site. At the University of Wyoming, studies focused on root length density (RLD). The RLD is an important parameter to model water and nutrient movement in the vadose zone and to study soil-root-shoot-atmosphere interactions. A generalized function was established to characterize the NRLD distributions versus normalized root depths. To verify the generalized function, the researchers measured RLD distributions of winter wheat (Triticum aestivum L.) using laboratory and field experiments for different soils, growing stages of wheat, atmospheric conditions, and water supplies. Using the generalized function, the researchers predicted winter wheat RLD and compared the predicted results with the experimental data and with results using other NRLD functions. A field experiment was conducted to measure distributions of soil water content, soil-plant osmotic potential, and root length density of winter wheat (Triticum aestivum L. cv. Nongda 186). The results showed that the inverse method was reliable and useful to estimate Lnrd distributions and simulate soil water flow with root-water-uptake continuously and effectively in field settings, without requiring any measured root density data. Objective 2: To develop and evaluate instrumentation and methods of analysis for characterization of flow and transport at different scales: USDA-USSL scientists were active in a number of areas including the search for a permanent storage facility for the geological disposal of high-level nuclear waste has motivated extensive research during the past several decades to characterize and predict fluid flow into and through unsaturated fractured rock. The researchers constructed several prototype instruments from porous stainless steel membrane, stainless steel casing, acrylic tubing, several pressure transducers, solenoid valves, and a data logger for automated control and data acquisition. An automated refill system was developed to facilitate long unattended equilibration periods typical for infiltration experiments on unsaturated fractured rock. Results show that the improved design reduces temperature effects on the infiltration rate, allows for much longer periods of unattended operation (auto-refill), and reduces evaporation from the infiltrometer. They also developed a method for the measurement of soil water content with capacitance probe sensors: Capacitance probe sensors are an attractive electromagnetic technique for estimating soil water content. At UC-Riverside, scientists worked on developing a potential hazard index for nitrate in states of the southwest in response degradation of aquifers under agricultural lands. A Nutrient Technical Advisory Committee (TAC), appointed by the California State Water Resources Control Board, recommended a hazard index approach to assess vulnerability of groundwater from agricultural nutrient contamination. Scientists are developing an interactive, web-based system where growers on irrigated lands in California, Arizona, or Nevada can assess their relative risk of contaminating groundwater. A database of over 500 soils and 150 crops in the three states has been compiled. The soils and crops were ranked for their leaching potential and rankings were reviewed by experts. An interactive website that calculates nitrate leaching potential and provides growers with best management practices was developed. Iowa State University scientists worked on field measurements related to surface soil chemical transport properties. The dripper-TDR method allows rapid field assessment of surface chemical transport properties. The researchers deployed a combination of drip-emitters and TDR to measure near-surface water content and chemical concentration, which in turn were used with CXTFIT for inverse prediction of soil chemical transport properties. Treatments included: No-till/no traffic, No-till/traffic, Chisel plow/no traffic, and Chisel plow/traffic. Several thermo-TDR probes were installed vertically from the soil surface, and heat-pulse and TDR measurements were recorded before a gravimetric sample was collected. Preliminary results indicate some success with the TDR portion of the measurement, but some difficulties with the heat-pulse measurements may impose some constraints. Montana State University researchers focused on three areas: (1) Impedance analysis approach for measuring dielectric spectra. The technique provides excellent agreement with the known dielectric constant of solvents, and evaluation in porous media is continuing, (2) Mutual interference by TDR signal multiplexers in electrical conductivity measurements, and (3) Temperature affects on TDR travel time measurements. TDR travel-time measurement for all soils and sand-clay mixtures are consistent with the earlier interpretations that these represent an interplay between the dielectric responses of free and bound water. The researchers consider that this phenomenon may now be confidently exploited, for example, to estimate specific surface area of soils and porous media. This will be highly useful in a number of soil management applications. In collaboration with Thomas J. Sauer (National Soil Tilth Laboratory) and Robert Horton (Iowa State University), University of Minnesota scientists have completed three field experiments to evaluate methods for measuring soil heat flux in surface energy balance studies. The researchers hope to demonstrate 1) the magnitude and frequency of errors in the plate method, 2) the likely causes of these errors, and 3) some alternatives to the plate method. The three needle gradient method the researchers utilized in this study is one promising alternative to the traditional plate method. The self-calibrating plate method which the researchers used at the soybean site also appears to give accurate readings. Both of these alternatives merit further research and development. Utah State University are continuing collaboration with University of Connecticut to improve water content determination using electromagnetic measurement techniques in saline and clayey soils. The major accomplishments for 2004 were the development of techniques to determine the permittivity of soil minerals, which greatly aids the modeling effort, a model was developed to describe the response of the Enviroscan in saline and clay soils. The Enviroscan is perhaps the most commonly used soil moisture sensor system currently used in agriculture, a number of articles have been accepted for publication, that begin to examine the application of sensor technology to spatial soil moisture content, and a methodology for characterizing electromagnetic sensors was developed. University of Connecticut and Utah State University in conjunction with Space Dynamics Laboratory, USU (Bingham) have developed a gas diffusion characterization measurement system for the International Space Station. University of Connecticut and Utah State University conducted experiments using Ground Penetrating Radar (GPR) with a suspended horn antenna to measure wheat and corn canopy properties and soil water content dynamics over bare and electrically terminating surfaces. University of Connecticut and Montana State University, are developing methods to estimate specific surface area of soils using the TDR thermo-dielectric response. To avoid measurement artifact in lossy soils, the researchers are quantifying the Maxwell-Wagner dielectric relaxation resulting from fragmentation polarization and DC electrical conductivity. University of Connecticut, Montana State University, and Utah State University researchers in collaboration with Volcani Center, Israel (S.P. Friedman) are evaluating the role of soil physical properties and water distribution characteristics on soil microbial behavior (activity, distribution and community composition). New methods to measure specific surface area, matric potential, and water retention will improve abilities to manage spatially variable soil and water resources efficiently and profitably. University of Idaho researchers investigated hydraulic and swelling properties of clays, visualization and quantification of spatial phase arrangement in bentonite-sand mixtures with x-ray computed tomography, developed observations of microstructure of clay-sand mixtures at different hydration states with scanning electron microscopy (with University of Connecticut), and developed a universal scaling law for soil water characteristic curves at low water contents (with University of Connecticut). Objective 3: To Apply scale-appropriate methodologies for the management of soil and water resources. Scientists at the USDA-USSL worked on two projects: 1. Application of soil fumigants with drip irrigation systems: Soil fumigants are used to control a wide variety of soil-borne pests in high-cash-value crops. Application of soil fumigants through drip irrigation systems is receiving increasing attention as a method to improve the uniformity of fumigant application. Little information is available on the emissions and soil distribution of fumigants following subsurface drip application, or the effect of plastic tarp on fumigant emissions in these systems. In these experiments, the fumigant compounds 1,3-dichloropropene (1,3-D), Vapam (a methyl isothiocyanate (MITC) precursor), and propargyl bromide (PrBr) were applied to soil beds via drip irrigation at 15 cm depth. Beds were tarped with either standard 1-mil high-density polyethylene (HDPE) or a virtually impermeable film (VIF). Cumulative emissions of 1,3-D, MITC, and PrBr in these tarped bedded systems was very low, amounting to <10% of the applied mass. Cumulative emissions of MITC and 1,3-D from a sandy loam field soil were decreased by ³80% by tarping the bed with VIF rather than HDPE. Monitoring the fumigant distribution in soil indicated that tarping the bed with VIF resulted in a more effective containment of fumigant vapors compared to use of a HDPE tarp. 2.Methyl bromide alternatives: Propargyl bromide (3-bromo-propyne, 3BP) is a potential replacement for the soil fumigant methyl bromide. A study was conducted to compare the volatilization and movement of 3BP in the soil profile for different irrigation treatments. Volatilization was about three times greater from non-irrigated soil. Irrigation and higher initial soil moisture content were more effective in controlling 3BP volatilization than the use of a HDPE tarp. At UC Riverside, research was also directed at ion diffusion in diffuse double layers. Ion diffusion and exchange in soil are usually treated as two independent processes. Ion diffusion is described by Ficks first and second laws without considering the influence of electrical field, while ion exchange is described by adsorption and desorption processes without considering the dynamic nature of ion distribution in the diffuse double layer (DDL). Researchers at UC-Davis analyzed water and sediment of irrigation and associated tail waters of a 30 ha corn field in the Central Valley in California, in order to quantify the sediment and carbon budget of a furrow-irrigated field. This field was monitored to assess the effects of minimum tillage versus standard tillage on soil C sequestration and greenhouse gas emissions. No differences were found between compositions of waters or sediments regarding tillage treatments. The measured soil C increase is approximately equal to 20% of the reported yearly carbon sequestration rates in long-term soil carbon sequestration experiments, that report C sequestration values of about100 kg C ha-1 y-1. To reduce the harmful effects of irrigated agriculture on the environment, the evaluation of alternative irrigation water management practices is essential. Micro-irrigation offers a large degree of control, enabling accurate application according to crop water requirements, thereby minimize leaching. Furthermore, fertigation allows the controlled placement of nutrients near the plant roots, reducing fertilizer losses through leaching into the groundwater. The presented two-dimensional modeling approach provides information to improve fertigation practices using four different micro-irrigation systems. The researchers found that seasonal leaching was the highest for coarse-textured soils, and conclude that fertigation at the beginning of the irrigation cycle tends to increase seasonal nitrate leaching. In contrast, fertigation events at the end of the irrigation cycle reduced the potential for nitrate leaching. At Montana State University, belowground mechanisms of invasive plant success were studied. The researchers hypothesized that C. maculosa (spotted knapweed), may succeed through a superior ability to access soil water. Researchers compared soil water uptake patterns under monocultures of the invasive C. maculosa resident perennial grasses, and a native perennial late-season forb, Rudbeckia hirta (blackeyed Susan), at two semiarid rangeland field locations. The Utah State University soil physics group is in the process of developing and testing a mobile sensor platform that can be integrated with agricultural machinery to provide mapping of soil water content, temperature, bulk electrical conductivity and other key properties of field soils. A prototype mobile sensor platform has been constructed based around an all terrain vehicle. Nevada is continuing research to better understand the linkages between soil morphology and soil hydrology. During 2004, Nevada focused on a new method to study the unsaturated hydraulic properties of individual soil peds (Meadows et al., 2004). Nevada has been seeking to apply concepts of time dependency on soil properties, to waste disposal practices. Waste disposal in Nevada, and other arid and semi-arid areas, often rely on evapotranspiration processes as a means of removing water that could otherwise percolate through soil and into the waste. The researchers hypothesize that these ET covers are also landforms that will be subject to environmental change over time. The researchers found good evidence for increased perennial plant cover, both from live and dead shrubs, at progressively older analog sites to about 10,000 years in the area of study; after 10,000 years, it appears that the plant cover decreased. The results support the hypothesis that ET covers are dynamic landforms that will evolve with time, and that environmental processes that influence landscape development are intimately linked to each other. At Washington State University, researchers have studied the scale-dependence of saturated and near-saturated hydraulic conductivity measurements. A 30-cm long soil core was taken from the topsoil of an agricultural field and hydraulic conductivities were measured with a constant head setup (tension infiltrometer). The core was dissected in 5-cm increments and hydraulic conductivities were measured after each dissection. Continued efforts were devoted to examining the uncertainty associated with water flow and solute transport through the variably-saturated, heterogeneous field at the Idaho Nuclear Technology and Engineering Center (INTEC), Idaho National Engineering and Environmental Laboratory (INEEL). The uncertainty in water and solute movement was related to the uncertainty in (i) categorization of the subsurface media into basalt and interbedding sediments; (ii) the spatial location of the interbeds; and (iii) estimated parameters in the geostatistical model. The US Department of Energys TOUGH2 model was used as the core deterministic model and the model predictions of flow and solute transport in response to changes in the aforementioned three factors were analyzed.

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