Predicting Sodification of Soil Following Irrigation with Saline-Sodic Water

Models based on simple and easily determinable soil parameters were prepared to predict the exchangeable sodium percentage (ESP) in a soil profile after a number of irrigations with water of high sodium adsorption ratio (SAR). The models assumed complete mixing between the initial and the incoming solutions, and also instantaneous exchange equilibrium between the cations in solution and those on the soil exchange complex. Gapon's equation was used to predict the changes in the cationic composition of solution and adsorbed phases. Experiments were conducted on large soil columns to verify the computed results. The agreement between experimental and predicted values was fair. Discrepancies were explained on the basis of mobile and immobile zones of the flowing solution in soil.