2007 Annual Report 1a.Objectives (from AD-416) Water quality criteria were initially developed to protect irrigated soils from possible adverse soil structural changes (such as reduced infiltration) and avoid reductions in crop yield due to salinity. Increased demands on our limited water resources necessitates that we more accurately determine these criteria since many waters deemed unsuitable can be used under specified conditions. Application of these criteria and application of recycled irrigation drainage water and treated municipal waste water will reduce the margin of error and require that we carefully monitor changes in soil properties, and thus develop improved monitoring protocols and practices. Based on these needs the research project is focused under two objectives: Objective 1: Develop new knowledge and guidelines related to major ion, B, and Mo concentrations for the sustained use of degraded waters including drainage waters and municipal waste waters. Objective 2: Evaluate the use of geophysical and geographic information system technology to monitor spatio-temporal changes of soil properties, salinity, trace elements and N. Both of these objectives are necessary for effective and protective implementation of irrigation with impaired waters. Although the stated objectives can be achieved by pursuing parallel lines of research, they will be combined in development of management practices. The monitoring technology objective is also essential to future field evaluation of the criteria and predictions made relative to objective one. 1b.Approach (from AD-416) 1:The adsorption behavior of B and Mo will be studied as a function of solution pH, solution anion concentration, electrolyte composition, and competing anion concentration in batch systems on soils chosen to represent a variety of soil orders. The adsorption behavior will be described using a chemical surface complexation model, allowing for development of improved management of degraded waters high in B and Mo. The desorption behavior of both native soil B and recently added B will be characterized in batch systems to determine the extent of desorption hysteresis in the presence and absence of competing ions. If desorption hysteresis is found, mathematical equations will be developed to describe the B desorption process in batch systems. Data will be analyzed, and B movement predicted using initial soil characteristics, ET calculations, and water composition using the UNSATCHEM model. New B transport routines will be developed if needed. Waters of varying composition including salinity, SAR, pH, alkalinity, and Ca/Mg ratio, will be applied to soils in outdoor containers with measurement of the water infiltration rate for both irrigation water and alternate application of rain using a rainfall simulator. The results of these experiments will be incorporated into predicted routines in UNSATCHEM and in guidelines for use of impaired waters. We will evaluate the impact of use of degraded water on soil quality, productivity and forage quality of a marginally productive saline-sodic soil. Characterization of soil spatial variability will utilize ECa measured by electromagnetic induction equipment, where each site is geo-referenced using GPS. 2: Validation of use of ECa-directed sampling to spatially characterize soil properties (salinity, texture, water content) will be made at a drainage water reuse site. ECa measurements will be used to determine 40 site locations from a response surface sampling design algorithm. Additional sites will be randomly selected for a validation data set. Correlating properties will be predicted from spatial regression models and compared to randomly chosen positions where validation sample data have been collected with development of a protocol for model validation of directed sampling techniques. A site in semi-arid CO under no-till will be used to evaluate ECa-delineated zones as a framework for site-specific N management in winter wheat and for field-scale monitoring of soil quality response and identification of soil quality trends. To evaluate site specific management, using ECa zones, 3 years of yield, ECa zone, and N-treatment maps will be compared with geo-referenced soil sample analyses for N-use efficiency and optimal N rates for each ECa zone. A phenomenological model of salinity development will be formulated based on spatial data of potential soil salinization factors (e.g., soil type, poor drainage areas, topography, leaching fraction, depth to groundwater, groundwater quality, etc.) for the Red River Valley basin of North Dakota and Minnesota. The phenomenological model will be used to create an inventory map of salinity for the entire Red River Valley. Formerly 5310-5310-61000-012-00D. 4.Accomplishments Sustainability of Drainage Water Reuse as Evaluated with ECa-directed Soil Sampling: Drainage water reuse offers one means of providing an additional source of irrigation water and concurrently reducing the volume of drainage water. The short-term (i.e., 5 years from 1999-2004) sustainability of drainage water reuse on a saline-sodic site located on the San Joaquin Valley's west side (WSJV) was evaluated using ECa-directed soil sampling by USSL, Riverside, CA scientists. The evaluation demonstrated the reclamation of marginally productive WSJV saline-sodic soil while reducing drainage volumes and serving as an alternative water resource for salt tolerant forage. The reuse of drainage water at the saline-sodic site reduced salinity, Mo, B, and SAR from 1999-2004 with associated increases in forage yield and quality. However, long-term sustainability may be in question due to the unexpected appearance of low levels of Se and reappearance of Mo at shallow soil depths. This work confirms the short-term viability of drainage water reuse as an alternative water source for marginally productive WSJV saline-sodic soils and as a means of reducing drainage volumes, thereby reducing the need for evaporation ponds. This research directly relates to National Program 211 Water Availability and Watershed Management, addresses goal 2.3: Improved irrigation and cropping for reuse of degraded waters and the National Program 202 Soil Resource Management, addresses program area 9: Soil Degradation. Predicting selenite adsorption by soils using soil chemical parameters in the constant capacitance model: Selenium is an essential trace element that can be toxic to animals at elevated concentrations. Toxic concentrations can occur in agricultural soils and irrigation waters necessitating a better understanding of its adsorption behavior. Adsorption of selenite by 36 soil samples was investigated under changing conditions of solution pH. USSL, Riverside, CA researchers evaluated and predicted the adsorption behavior using a chemical model, the constant capacitance model, and the easily measured soil chemical characteristics: inorganic carbon, organic carbon, iron oxide, and aluminum oxide content and surface area. The results will benefit scientists who are developing models of selenite movement in arid zone soils. The results can be used to improve predictions of selenite behavior in soils and thus aid action and regulatory agencies in the management of soils and waters which contain elevated concentrations of selenite. This research directly relates to National Program 211 Water Availability and Watershed Management, addresses goal 2.3: Improved irrigation and cropping for reuse of degraded waters. Predicting soil water composition from extract analyses: Monitoring and evaluation of soil salinity and irrigation management is critical when using impaired waters for irrigation. Evaluation of soil salinity status is made by collection of soils, addition of water to the soil and extraction of available solution in the laboratory. Interpretation of the results is made complex by the lack of a general relationship between the extracted solution and the in situ soil solution, due to the solution dilution and subsequent chemical processes of mineral dissolution, cation exchange and oxyanion desorption. ARS scientists at USSL, Riverside, CA developed EXTRACTCHEM, a computer model, with user friendly interface, (available on our web site) that considers the relevant chemical processes and predicts the solution, composition, electrical conductivity, and osmotic pressure from any specified water content to any other water content. The model is essential for calibration of apparent electrical conductivity soil surveys, especially in gypsiferous soils, reporting of salt tolerance information, and evaluation of soil salinity status based on soil extract analyses. This research directly relates to National Program 211 Water Availability and Watershed Management, addresses goal 2.3: Improved irrigation and cropping for reuse of degraded waters. Guidelines and Protocols for Field-scale Measurement of Soil Salinity Using EMI in the Red River Valley: Climatic change has resulted in abnormally high precipitation in the Red River Valley (RRV) of North Dakota and Minnesota, leading to higher groundwater tables and subsequent salinization of highly productive Mollisols. Inventorying soil salinity at field and regional scales is a high priority for NRCS in the RRV to understand the extent of the salinity problem and its impact over time. Guidelines and protocols are needed for both field- and regional-scale salinity assessments. General guidelines and protocols were developed by USSL scientists and transferred to NRCS RRV field staff for inventorying soil salinity at field scale. These guidelines and protocols were presented to NRCS field staff at the SWCS Soil and Water Summit (Carrington, ND; June 13, 2007). This work will reduce misinterpretation and misunderstanding common in prior efforts to inventory salinity, thereby laying the foundation for the development and evaluation of future regional-scale salinity assessment protocols. The research directly addresses the Soil Degradation Problem Area (Problem. 9)in National Program 202. Mechanism of molybdenum adsorption on soil minerals evaluated using vibrational spectroscopy and surface complexation modeling: Molybdenum is a specifically adsorbing anion that can be detrimental to animals at elevated levels. A better understanding of the adsorption behavior of molybdenum is necessary to predict soil solution molybdenum concentrations. ARS scientists at the USSL, Riverside, CA evaluated and predicted adsorption of molybdenum by 36 soil samples using a chemical model, the triple layer model, and the easily measured soil chemical characteristics: inorganic carbon, organic carbon, aluminum oxide, and iron oxide content, and cation exchange capacity. Our results will benefit scientists who are developing models of molybdenum movement in soils. The results can be used to improve the management of soils and waters which contain elevated concentrations of molybdenum. This research directly relates to National Program 211 Water Availability and Watershed Management, addresses goal 2.3: Improved irrigation and cropping for reuse of degraded waters. 5.Significant Activities that Support Special Target Populations None 6.Technology Transfer Number of web sites managed 1 Number of non-peer reviewed presentations and proceedings 27 Review Publications Corwin, D.L., Rhoades, J.D., Simunek, J. 2007. Leaching requirements for soil salinity control: steady-state versus transient models. Agricultural Water Management. Vol 90: 165-180 Herbel, M.J., Suarez, D.L., Goldberg, S.R., Gao, S. 2007. Evaluation of chemical amendments for ph and redox stabiliztion in aqueous suspensions of three california soils. Soil Science Society of America Journal. Vol 71(3): 927-939 Goldberg, S.R., Suarez, D.L. 2006. Prediction of anion adsorption and transport in soil systems using the constant capacitance model. In: J. Lutzenkirchen (ed.) Surface complexation modeling. Interface Science and Technology series, Elsevier, Amsterdam, Volume 11 p: 491-517. Shouse, P.J., Goldberg, S.R., Soppe, R.W., Skaggs, T.H., Ayars, J.E. 2006. Effects of shallow groundwater management on the spatial and temporal variability of boron and salinity in an irrigated field. Vadose Zone Journal. 5:377-390. Goldberg, S.R., Criscenti, L.J., Turner, D.R., Davis, J.A., Cantrell, K.J. 2007. Adsorption-desorption processes in subsurface reactive transport modeling. Vadose Zone Journal. Vol 6(3):407-435.