Location: Water Reuse and Remediation Research2010 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.
3. Progress Report
Bromide (Br-) adsorption was investigated on oxides, clays, and soils. Adsorption decreased with increasing pH with minimal adsorption above pH 7. Our results indicate that Br- would not act conservatively at soil pH below 7. Therefore, researchers must evaluate the pH of their study site before assuming that Br- can be applied as a conservative tracer for transport experiments. Release of native boron (B) was quantified on soils in the presence and absence of sufficient magnesium (Mg) and silicon concentrations to suppress the dissolution of B containing Mg silicates. We established that most B release is due to desorption and not mineral dissolution. Boron adsorption was determined on kaolinite as a function of pH in the presence of K+ or Ca2+. When the data were corrected for dilution, adsorption in the Ca system was comparable to that in the K system. Adsorption of Ca-borate ion pairs is thus not significant, in contrast to existing literature reports which did not correct for dilution. Boron transport under agricultural conditions can be described without consideration of solution cation composition. Use of Geophysical Techniques to Map and Monitor Saline-Sodic Soils at Field Scales during Remediation: Soil and plant samples were taken (70 sites at 6 depths) and analyzed. A validation of the apparent soil electrical conductivity (ECa) directed sampling approach was conducted. A statistical comparison was made of model- and design-based sampling strategies for characterizing soil spatial variability with ECa-directed soil sampling. Integrated Advanced Information Technologies to Delineate Site-Specific Nitrogen Management Units (SSNMUs): Yearly soil and plant samples were taken (48 sites at 6 depths) and analyzed. Guidelines and Protocols for Regional-scale Salinity Assessment of the Red River Valley: Geo-referenced database of salinization factors was completed for Walsh and Kittson Counties. Exploratory statistical analysis of salinization factors was conducted. A site-specific salinity development model was formulated for approximately 300,000 ha (Walsh and Kittson Counties). We completed additional outdoor infiltration experiments on arid zone soils, using rain-irrigation and irrigation only treatments over a 180 d period, with waters of varying SAR (sodium adsorption ratio) and pH 7 and 8.2. We measured infiltration upon application of high quality water at the end of the experiment, evaluating potential for soil recovery. We analyzed data and developed predictive relationships describing the infiltration reduction related to SAR, pH and number of irrigation/rain events. We also examined the related saturated hydraulic conductivity response of lab soil columns, under 2 weeks of continuous application of the same waters. Short term lab studies did not show an adverse effect comparable to the outdoor experiments. We collected additional water samples from Grand Valley CO to evaluate the 25 y impact of improvements in irrigation management on salt discharge to the Colorado River. We initiated development of a user friendly model to predict plant yield as related to irrigation water salinity, ET and water application.
1. Guidelines and Protocols for Regional-scale Salinity Assessment of the Red River Valley (RRV): Land managers and policy makers across the globe need a regional-scale tool for measuring and inventorying soil salinity in agricultural fields where salt buildup lowers crop yields. A scientific team led by an ARS scientist at Riverside, CA, used MODIS imagery to assess and map soil salinity across 300,000 hectares of North Dakota’s and Minnesota’s RRV. Rising soil salinity levels due to rising water tables in the Red River Valley have been linked to increasing precipitation from climate change. They found that 53 percent of the variability in soil salinity could be correlated to multi-year enhanced vegetative index and whether land was eligible for Conservation Reserve Program inclusion (a federal program that sets aside marginally productive land based on conservation principles). Results from this research, provide the NRCS with protocols and guidelines for mapping soil salinity over hundreds of thousands of hectares of the RRV.
2. Water quality criteria for irrigation: Increased use of marginal waters and treated waste waters for irrigation increases the need for accurate water quality criteria degrading pH, sodium absorption ratio and salinity. Based on the new outdoor and laboratory experiments ARS scientists in Riverside, CA refined the earlier developed water quality criteria relating infiltration hazard to these variables. These guidelines replace earlier FAO criteria that did not consider pH and underestimated the adverse impact of even slight increases in SAR on water infiltration. Results from this work provides water quality specialists, water planners, regulatory agencies and producers the ability to better evaluate the infiltration hazards associated with application of a specific irrigation water composition.
3. Leaching requirements for irrigation with saline water: Current leaching criteria appear to overestimate the quantities of water required to be applied for leaching when using saline waters for irrigation, based on comparison with limited field studies. These criteria generally lead to the conclusion that most waters of elevated salinity may be unsuitable for most crops. Modeling studies of scientists in Riverside, CA (using their earlier developed Society of Webland Scientist soil-water plant model); predict that lower water applications, greatly reducing leaching requirements, are often possible, with little to no yield loss. These results are compatible with field data, thus leaching quantities should be determined with this or other dynamic plant response models, instead of from current leaching requirement guidelines. The research is critical for producers and irrigation specialists to accurately predict leaching requirements, and should enhance the utilization of more saline waters for irrigation.
4. Describing molybdenum (Mo) adsorption on gibbsite: Detrimental levels of Mo in livestock can occur from ingestion of forage plants grown on soils irrigated with waters containing high concentrations of Mo. Adsorption reactions reduce solution Mo concentrations and therefore a better understanding of the adsorption behavior of Mo is necessary. Adsorption of Mo by the aluminum oxide gibbsite, a common soil mineral, was evaluated by ARS scientists in Riverside, CA as a function of equilibrium solution Mo concentration, solution pH, and competing phosphorus (P) and sulfur (S) concentration and described using a chemical model with all ions at levels realistic of natural concentrations. Sulfur, even at elevated concentrations, did not affect Mo adsorption. The model was able to predict the competitive effect of P on Mo adsorption semi-quantitatively. Our results will benefit scientists who are developing models of Mo movement in arid zone soils and can be used to improve predictions of Mo behavior in soil solutions and soils and thus aid action and regulatory agencies in the management of soils and waters which contain elevated concentrations of Mo and to predict Mo transport at realistic concentrations in soils.
5. Use of geophysical techniques to map and monitor saline-sodic soils at field scales during remediation: Apparent soil electrical conductivity (ECa) directed soil sampling is a means of mapping soil salinity at field scale and larger spatial extents. ARS researchers at Riverside, CA collected field-scale data that indicates that geospatial measurements of ECa to map soil salinity should be taken at >70% of field capacity. If not, conductance pathways are restricted and spurious results will occur. A gray area of measurement was found to exist between 50-70% of field capacity, which ostensibly depends on texture. This information indicates a limitation of the ECa-directed soil sampling approach and modifies the current protocols for assessing field-scale salinity with electromagnetic induction or electrical resistivity.
Lobell, D.B., Lesch, S.M., Corwin, D.L., Ulmer, M.G., Anderson, K.A., Potts, D.J., Doolittle, J.A., Matos, M.R., Baltes, M.J. 2010. Regional-scale Assessment of Soil Salinity in the Red River Valley Using Multi-year MODIS EVI. Journal of Environmental Quality. 39(1):35-41