1a.Objectives (from AD-416):
To develop information on the impact on soil physical and chemical properties when using degraded and saline waters for irrigation and determine predictive relationships based on statistical analysis of lab and field experiments.
1b.Approach (from AD-416):
To conduct laboratory and field research as needed to determine the impact of degraded and saline waters on physical and chemical properties of California soils.
This research is related to the parent project, objective 1: Develop new knowledge and guidelines related to major ions, Boron (B), and Molybdeum (Mo) concentrations for the sustained use of degraded waters including drainage waters and municipal waste waters. We initiated and conducted an experiment to evaluate the changes in infiltration rates of a soil with smectite clay from the Central Coast when irrigated with waters of increased SAR and pH. We examined a range of sodium adsorption ratios between 0-10, and pH between 6 and 9. We utilized a wetting and drying sequence to simulate field conditions, including rain via a rain simulator. Previous infiltration experiments examining these variables have been with non swelling clays. The patterns of sensitivity to increased sodium adsorption ratio (SAR) were comparable to the other soils tested with decreases in infiltration observed even at sodium adsorption ratios as low as 2. We also initiated an experiment to evaluate the changes in unsaturated hydraulic conductivity related to solution chemistry. The limited literature available on this subject was based on experiments that did not consider the effect of pH nor adequately characterize the initial chemical conditions. These results will compliment the infiltration studies and the known literature on saturated hydraulic conductivity.