Management of Salt-affected Vertisols with Sub-surface Drainage and Crop Residue Incorporation under Soybean-Wheat Cropping System

Field experiments were conducted during 1994–95 to 1997–98 to study the effect of sub-surface drain spacings and crop residue incorporation on reclamation of salt-affected Vertisols under soybean-wheat cropping system. The results indicated that sub-surface drains at 25, 50 and 75 m spacings installed at 1.3 m depth with corrugated PVC perforated pipe worked efficiently in draining out excess water from the field and thereby significantly increased the productivity of soybean and wheat crops besides improving the physical properties of soil such as bulk density, infiltration rate, hydraulic conductivity and decreased soil salinity (EC_e from 4.06 to 2.03 dS m⁻¹) and sodicity (ESP from 14.7 to 9.8). In general, the drainage discharge induced at 450 to 550 mm rainfall. The drainage coefficient was highest (18 mm day⁻¹) under 25 m spacing. Based on gross monetary returns of soybean-wheat system and drainage installation cost 75 m drain spacing was found beneficial. The incorporation of crop residue either sugarcane trash @ 5 t ha⁻¹ or green manuring with dhaincha significantly increased the productivity of crops and proved to be better for reducing soil salinity and improving physical properties and the organic matter content of the salt-affected Vertisols.