Abstract
A field experiment was conducted from 1988-89 to 1994-95 to evaluate different organic supplements, viz., cowpea (green manure), subabul (Leucaena leucocephala) as biomulch, and farmyard manure (FYM) in different combinations, to substitute fertilizer N and improve the productivity of cotton (Gossypium hirsutum L.) grown on marginal soils under rainfed conditions. Within four years, cotton yields equivalent to that using 30 kg N ha-1 could be obtained with continuous incorporation of cowpea (in situ green manure) followed by a biomulch with subabul at 10 t ha-1 or with cowpea along with subabul at 5 t ha-1 and FYM at 5 t ha-1 or FYM alone at 10 t ha-1, thus providing alternative farming practices to reduce fertilizer N. Organic supplements improved soil organic C, resulting in an improved hydrophysical environment resulting in a 2-2.5% high available soil moisture and 10-27% higher mineralizable N during the critical boll development period of rainfed cotton.
