INTEGRATED NUTRIENT MANAGEMENT IN WETLAND RICE (ORYZA-SATIVA)

A field experiment was conducted during rainy seasons of 1989 and 1990 at Maruteru to develop an integrated nutrient-management system in 'Chaitanya' wetland rice (Oryza saliva L). Application of 50 (N-30, P-8.7, K-16.6, 75 (N-45, P-13.1, K-25 and 100% (N-60, P-17.5, K-33.3 of the recommended NPK fertilizer through inorganic form increased the yield by 29.8, 54.8 and 93.3% respectively compared with unfertilized control. Among the organic manures, farmyard manure (3.75 tonnes/ha) and green-manuring with prickly sesban [Sesbania cannabina (Retz) Pers.] (2.24 tonnes/ha) in conjunction with inorganic fertilizers (N-45, P-13.1, K-25 gave rice yield on a par with that from the sole supply of chemical fertilizers (N60P17.5K33.3. In general incorporation of rice straw (6 tonnes) and green-manuring with prickly sesban (4.48 tonnes/ha) in combination with 50% recommended chemical fertilizers decreased the yield by 36.3 and 29.5% respectively. Application of 2.5% recommended N (15 kg N/ha) through farmyard manure: (3.75 tonnes/ha) and prickly sesban (2.24 tonnes/ha) increased the grain yield by 90 and 84% respectively compared with the central (N-0) and was equal to that with complete chemical fertilization, due to low C : N ratio. Incorporation of rice straw at 6 tonnes/ha in the soil delayed the seedling establishment, caused high seedling mortality and decreased the yield by 36.3% compared with sole supply of inorganic fertilizers, indicating unsuitability of high carbonaceous material in the soil. Judicious use (25% of recommended NPK) of farmyard manure @ 3.75 tonnes/ha and prickly sesban @ 2.24 tonnes/ha showed least interference with seedling establishment and growth.