Modeling salt transport in irrigated soils

This study evaluates the effects of the volume of leachate on the quality of the leachate. A numerical model of salt transport was used in the study. Field data were collected on 63 research plots located in the Grand Valley (Colorado, U.S.A.) and used to test and calibrate the model. The model was used in a series of hypothetical simulations designed to provide the required information.From the calibration of the moisture-flow model using infiltration data, soil water-content profiles, and soil water-storage change data, it was concluded that soil-water flow could be adequately modeled for the Grand Valley. The functional relations used for hydraulic conductivity and soil-water diffusivity and the method of averaging the values of the hydraulic parameters were developed during the course of the study. From comparisons of simulated and field data used in evaluating the chemistry model, it was concluded that total dissolved solids (TDS) concentrations were adequately modeled, but that individual ionic species concentrations were not. Comparison of calculated and measured data indicate that the CaSO₄CaCO₃Ca(HCO₃)₂ system is not properly modeled for the soil in the Grand Valley.Data for single growing season simulations using 7- and 14-day irrigation schedules and 2, 5, 20 and 40% leaching increments, coupled with data from a six-year simulation using a 14-day irrigation interval and 20% leaching increment, indicate that the salt concentration of the leachate at the bottom of the soil profile is independent of the volume of leachate.