Long-term effects of fertilizers and integrated nutrient supply systems in intensive cropping on soil fertility, nutrient uptake and yield of rice

Abstract

The long-term effect of fertilizers and an integrated nutrient supply system was studied in a rice–rice sequence for 8 years at Hyderabad in India from 1988/89 to 1995/96. Nutrient uptake and seed yield improved with increase in fertilizers up to the recommended dose of 120, 60, 40 kg/ha, N, P₂O₅ and K₂O in the rainy and post-rainy seasons during the 8 years sequence cycles. The soil became enriched in organic carbon (OC) and maintained the available P while K concentration was reduced from medium to low status after 8 years. Integrated nutrient supply by incorporating glyricidia or FYM 15 days before transplanting the rice thereby substituting 25% nitrogen in the rainy season and application of only 75% of the recommended fertilizers in the post-rainy season maintained the overall mean yield at a level equal to that from the continuous application of the recommended fertilizer dose. The practice saved 30 kg N, 15 kg P₂O₅ and 10 kg K₂O/ha in every season and improved the OC% and available P of the soil. The overall mean production of rice grain following the substitution of 50% nitrogen with glyricidia in the rainy season and fertilizer application at the recommended dose in the post-rainy season was also equal to that given by the application of the recommended fertilizer dose applied in every season and increased the OC% and available P of the soil. This procedure reduced the fertilizer dose in the rainy season by 60 kg N, 30 kg P₂O₅ and 20 kg K₂O/ha.