EFFECT OF ORGANIC-MATTER AND GYPSUM IN CONTROLLING SOIL SODICITY IN RICE-WHEAT-MAIZE SYSTEM IRRIGATED WITH SODIC WATERS

A greenhouse experiment was conducted to study the effect of different organic materials (green manuring with Sesbania aculeata, farmyard manure, rice straw) and different levels of gypsum (to supply 2, 4, and 6 mEq Ca/l of sodic waters) in controlling the build up of Na in a calcareous sandy loam soil receiving sustained sodic irrigations under rice-wheat-maize system. Irrigation with sodic water caused precipitation of Ca and carbonates and increased the build up of Na in the soil and, hence, adversely affected plant growth. Application of gypsum increased the removal of Na in drainage water, decreased soil Na saturation and improved crop yields. Incorporation of organic materials decreased the precipitation of Ca and carbonates, increased the removal of Na in drainage water, decreased pH and exchangeable Na percentage (ESP) in the soil, and improved crop yields. With the mobilization of Ca due to decomposition of organic materials, the quantity of gypsum required for controlling the harmful sodic irrigation effects on soil properties could be considerably decreased. Application of gypsum with green manure or farmyard manure seemed to be the optimum treatment for improving soil properties and crop yields.