Location: Water Reuse and Remediation Research2011 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.
3. Progress Report
Boron adsorption-desorption hysteresis was evaluated on soils having varying organic matter content, since organic matter may control B hysteresis in soils. Our results suggest that B hysteresis may instead be the result of improper experimental technique. If this is true, the use of B adsorption data to describe B desorption behavior is justified and simplifies modeling soil B behavior. Release of native and amended boron from US and European soils after 11 to 23 month incubation times indicated only a small hysteresis effect. Potentially toxic concentrations of organic arsenic compounds can occur in agricultural soils and irrigation waters via application of herbicides, contaminated poultry manure from feed additives, and other degraded waters. Adsorption of dimethylarsenic acid and p-arsanilic acid by iron oxide minerals was investigated as related to solution pH and ion concentration. Adsorption behavior of dimethylarsenic and p-arsanilic acid was determined and described using a chemical surface complexation model. Water quality criteria did not consider impact of rain on infiltration when using elevated sodium waters. Most irrigated areas have input of rain so this is an important research gap. We conducted experiments in presence and absence of rain (rain machine) with varied sodicity and pH using the soil used for earlier FAO guidelines. This soil behaved similar to others studied earlier; the combined rain-irrigation had a more adverse response to sodicity compared to the irrigation only system. This finding is of direct use to all producers in regions where there is rain and use of lower quality irrigation water. Hazards associated with use of treated municipal waste water as related to loss in infiltration is currently represented only by water sodicity and salinity. In an initial experiment, we examined infiltration of treated waste water and prepared water of the same composition. Regardless of sodicity or pH the waste water had reduced infiltration, related to increased dissolved organic matter. This research is of importance to any producer using treated waste water for irrigation. Sustainability of Degraded Water Use Can Be Evaluated with ECa-directed Sampling of Soil Quality: An ECa survey and ECa-directed sampling were conducted at Westlake Farms after 12 years of drainage water reuse. Soil samples were taken and analyzed for a variety of soil properties. Spatio-temporal analysis of the data is underway to determine impact and sustainability of long-term drainage water reuse. Geophysical Techniques Can Be Used to Map and Monitor Saline-Sodic Soils at Field Scales during Remediation: A research paper was prepared comparing response surface sampling design for characterizing soil spatial variability with more traditional design-based sampling strategies. Integrated Advanced Information Technologies to Delineate Site-Specific Nitrogen Management Units (SSNMUs): The analysis of yearly soil and plant samples was completed. N use efficiency data have been compiled and calculated for 3 non-drought years (2005, 2006, and 2010). Analysis of the spatial data is in progress to establish optimal N rates for ECa-based SSNMUs.
1. Distinguishing boron (B) desorption from mineral dissolution in arid-zone soils. Boron is a specifically adsorbing anion that can be detrimental to plants at elevated levels, thus we need to accurately characterize B pools in soils. Release of native adsorbed B has been reported to be a significant source of soluble B in arid land soils, hence using six arid land soils we quantified B release, including under conditions designed to suppress and alternately allow for dissolution of B containing Mg silicates. Researchers at the Salinity Lab in Riverside, CA, established that most B release is due to desorption and not mineral dissolution, thus producers do not have to be concerned about regeneration of soluble B and potential toxicity after leaching to below toxic levels. This research is important to the management and control of soluble B in regions containing high native soil B, common in the arid southwest of the U.S.
2. Use of geophysical techniques to map and monitor saline-sodic soils at field scales during remediation. Field-scale monitoring and mapping of soil salinity with mobile geophysical techniques is based on statistical sampling strategies that use geospatial measurements of apparent soil electrical conductivity (ECa) as a surrogate to characterize spatial variability. Design-based sampling strategies, such as stratified random sampling and unsupervised classification, are commonly used, but a model-based sampling strategy (i.e., response surface sampling design) can offer the advantage of minimizing the sampling requirement. The ARS scientists in Riverside, CA, compared model- and design-based sampling strategies for characterizing the spatial variability of soil salinity with ECa-directed soil sampling indicated that the model-based sampling approach resulted in better model discrimination, more precise parameter estimates, and smaller prediction variances. This comparison provided further validation of the response surface sampling design for characterizing spatial variability with ECa-directed sampling and suggests that it is as reliable as any design-based sampling strategy with the advantage of reduced sample size. Implementation of these sampling design will allow for more rapid and less costly salinity mapping benefiting producers and irrigation districts that utilize mobile geophysical techniques.
3. Evaluation of boron extractants to characterize added and native adsorbed boron. It is important to characterize adsorbed soil boron since it can be readily transformed into soluble boron. Researchers at the Salinity Lab in Riverside, CA, quantified the release of native and added B on five arid zone soils, using various recommended extracting solutions and various times since boron addition. Boron release decreased as a function of time for some of the extractions and treatments, but more importantly all of the current B extraction methods significantly underestimate the quantities of adsorbed B in arid land soils. These results will benefit scientists attempting to improve predictions of B behavior in soils as well as specialists and producers who need to manage boron concentrations to avoid toxicity.
Ahmad, H.R., Ghafoor, A., Corwin, D.L., Aziz, M.A., Saifullah, Sabir, M. 2011. Organic and inorganic amendments affect soil concentration and accumulation of cadmium and lead in wheat in calcareous alkaline soils. Communications in Soil Science and Plant Analysis. 42:111-122.