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 ma nure, 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 cal careous sandy loam soil receiving sustained sodic irrigations under ri ce-wheat-maize system. Irrigation with sodic water caused precipitatio n of Ca and carbonates and increased the build up of Na in the soil an d, hence, adversely affected plant growth. Application of gypsum incre ased the removal of Na in drainage water, decreased soil Na saturation and improved crop yields. Incorporation of organic materials decrease d the precipitation of Ca and carbonates, increased the removal of Na in drainage water, decreased pH and exchangeable Na percentage (ESP) i n 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 properti es could be considerably decreased. Application of gypsum with green m anure or farmyard manure seemed to be the optimum treatment for improv ing soil properties and crop yields.