Location: Water Reuse and Remediation Research2008 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
Molybdenum (Mo) is a potentially toxic element to livestock and is present in high concentrations in some agricultural drainage waters. Understanding its movement in soil is essential to maintaining concentrations below toxic levels. The adsorption behavior of Mo was studied as a function of solution pH, Mo concentration, salt composition and competing ion concentration on 5 arid zone soils from CA. Adsorption was studied using salt solutions simulating low and high salinity irrigation water. We determined both Mo adsorption isotherms (amount adsorbed as a function of equilibrium solution Mo concentration) and adsorption envelopes (amount adsorbed as a function of solution pH per fixed total Mo mass). The adsorption behavior was described using a chemical surface complexation model. The model was able to describe Mo adsorption, thus helping us in predicting Mo transport in soils. Boron (B) is an essential micronutrient that can also be toxic to plants in high concentrations. Agricultural drainage waters often exceed these levels and management practices are needed to maintain B at non-toxic levels in the rootzone. The study on B movement and adsorption-desorption in 12 large soil columns, examined B transport with different concentrations and different solution compositions. Relatively low water applications, leaching fractions and deep soil profiles better represent field water and solute flow than typical short laboratory column experiments run at high flow velocities. Analyses were completed and final data interpretation is in progress. Recycled waters are generally elevated in pH (usually above 8.0) and SAR (sodium adsorption ratio) relative to typical irrigation waters. We completed the outdoor study examining the effect of SAR on infiltration under wetting and drying cycles and alternate rain and irrigation cycles. This study has been extended to examine the impact of changes in pH on infiltration using the same experimental setup. Sensitivity to SAR of the irrigation water was greater than indicated in previous studies and in currently utilized water quality criteria for irrigation. Sustainability of Drainage Water Reuse as Evaluated with ECa-directed Soil Sampling: Water reuse will require monitoring of the chemical status of the soils that receive drainage waters in order to maintain an optimal environment for crop production. Spatio-temporal data of soil chemical properties were analyzed and interpreted to establish the environmental impacts and potential sustainability of drainage water reuse. Guidelines and Protocols for Regional-scale Salinity Assessment of the Red River Valley: An increase in salinity, due to climate change has been noted in the valley. Technology is needed to assess the extent, map and quantify this salinity change Field selection, ECa (soil electrical conductivity) surveys, and soil sampling were completed for the second of three counties being used to formulate and calibrate the regional-scale salinity development model for the entire Red River Valley. Chemical analyses of soil samples from the first sampled county were completed. NP211, Component 2
1. Water Quality Criteria for Irrigation: Increased use of low quality waters requires consideration of the resultant impact on soil infiltration, as many waters are higher in sodium adsorption ratio (SAR) and pH than currently used irrigation waters. Based on experiments conducted by researchers at the U.S. Salinity Laboratory in Riverside, CA, we propose new water quality criteria related to SAR and pH effects on infiltration, including consideration of the interaction of rain and irrigation water. Previous criteria did not consider pH or rain interactions. These new criteria are essential to irrigation specialists, extension personnel and consultants that provide advice to producers, as well as to action agencies. This research directly addresses National Program 211 Water Availability and Watershed Management, Problem area II. Irrigation Water Management.
2. Distinguishing Boron Desorption from Mineral Dissolution in Arid Zone Soils: High levels of boron in the soil solution or from additions of boron via the irrigation water can be detrimental to plants. ARS scientists at the U.S Salinity Laboratory in Riverside, CA were able to distinguish B desorption from B release due to mineral dissolution as well as determine that currently used extraction methodology incompletely extracts adsorbed B. Our results will benefit scientists who are developing models of boron movement in arid zone soils and enable better characterization of plant available B. The results can be used to improve predictions of boron behavior in soils and thus aid action and regulatory agencies in the management of soils which contain elevated concentrations of boron. This research directly relates to National Program 211 Water Availability and Watershed Management, Water Availability and Watershed Management, Problem area II. Irrigation Water Management.
3. Geophysical Techniques for Mapping and Monitoring Saline-Sodic Soils at Field Scales during Remediation. It is currently difficult and expensive to assess the impact of remediation or use of recycled water at large, field scales. ARS scientists at the U.S Salinity Laboratory in Riverside, CA examined and assessed the adequacy and precision of spatial regression models calibrated using the response surface sampling design approach in comparison to random sampling. Results confirmed the validity of the response surface sampling design approach and thereby validated ECa-directed sampling for characterizing soil spatial variability to map and monitor fields during remediation or during management-induced change due to degraded water reuse. This research will enable agricultural specialists to efficiently sample and thus monitor changes in soil chemistry and salinity when degraded waters are used for irrigation. This research directly addresses National Program 211 Water Availability and Watershed Management, Problem area II. Irrigation Water Management.
4. Guidelines and Protocols for Regional-scale Salinity Assessment of the Red River Valley: There is currently no adequate method to assess salinity changes at the valley or basin scale. ARS scientists at the U.S Salinity Laboratory in Riverside, CA evaluated Moderate-resolution Imaging Spectroradiometer (MODIS) imagery as a tool to aid in the selection of a small subset of fields that can be examined more extensively using electrical conductivity surveys. We determined that this method provided the desired range of salinities enabling development and calibration of a salinity model for Kittson County in the Red River Valley. The methodology and developed county salinity model can potentially be used to develop a model for the entire Red River Valley, enabling evaluation of the salinity status of the valley. This research directly addresses National Program 211 Water Availability and Watershed Management, Problem area II. Irrigation Water Management.
5. Influence of Soil Solution Salinity on Boron Adsorption by Soils: Boron is a specifically adsorbing anion that can be detrimental to plants when present at elevated levels in the soil solution. The adsorption behavior of Boron was described and predicted by ARS scientist at the Water Reuse and Remediation Research Unit in Riverside, CA using a chemical model, the constant capacitance model, and the easily measured soil chemical characteristics; thereby demonstrating the predictive ability of the model at variable salinity levels. Our results will benefit scientists who are developing models of boron movement in arid zone soils, thereby improving predictions of boron behavior in soils. Prediction of boron concentrations and transport will aid action and regulatory agencies in the management of waters which contain elevated concentrations of boron. This research directly relates to National Program 211 Water Availability and Watershed Management, Problem area II. Irrigation Water Management.
Corwin, D.L. 2008. Past, present and future trends of soil soil electrical conductivity measurement using geophysical methods. In: B.J. Allred, J.J. Daniels and M.R. Ehsani (editors) Handbook of Agricultural Geophysics. CRC Press. Boca Raton, FL. Chapter 2 pp: 17-44.