Effect of Sodicity on Soil–Water Retention and Hydraulic Properties

Abstract

The present study analyses the effect of sodicity on unsaturated soil hydraulic properties. Permeameter and pressure plate experiments were conducted on six texturally different soils at varying sodicity levels to obtain saturated hydraulic conductivity and van Genuchten soil–water retention parameters. The results show that soils retain less water with high soil–water sodicity relative to low sodicity at the same matric suction. The van Genuchten water retention parameter α obtained from the experimental water retention curves increased in fine-textured soils with an increase in sodicity. In coarse-textured soils, no significant trend was observed. However, the value of parameter n increased in all soil samples. Hydraulic conductivity reduced in fine-textured soils and increased in coarse-textured soils with an increase in sodicity. The simulation of a hypothetical infiltration event at different sodicity levels indicated that the wetting front movement slows down with an increase in the sodicity level for fine-textured soils, whereas the wetting front moves at a faster rate in coarse-textured soils with an increase in sodicity level. Gravity drainage simulations indicate that there is a buildup of soil moisture storage in fine-textured soils with an increase in soil–water sodicity due to reduced gravity drainage and drying of the soil profile in coarse-textured soils due to increased gravity drainage. This study is useful to better manage irrigation scheduling in saline conditions.