Sustainable fertilizer practices for upland rice (Oryza sativa) from permanent manurial trials under subhumid alfisols

Twelve permanent manurial trials were conducted from 1994 to 2005 to develop a sustainable fertilizer application schedule for upland rice (Oryza sativa L.) and find out optimal fertilizer requirement for attaining maximum productivity in a moist subhumid alfisol. Nine treatments of organic N (glyricidia, cassia and farmyard manure) and inorganic N, P and K fertilizers together with a contol, were tested. The treatments differed significantly from each other in all seasons. Application of 50% N (FYM) + 50% PK of recommended dose proved superior, as evident from lowest yield decrease of 86.4 kg/year compared with a maximum of 170.9 kg/year with application of 100% NPK (inorganic). Regression analysis revealed that the treatment comprising 50% N (FYM) + 50% NPK was superior with a maximum yield predictability of 0.85 with a prediction error of 511 kg/ha, and a maximum sustainability yield index (0.47), maximum mean yield (1,811 kg/ha) and lowest variation (29%) in the study. The study indicated that an optimum application of 32, 22, 17 and 14 kg/ha organic N together with 28, 33, 39 and 47 kg/ha inorganic N could be made respectively under 500–750, 750–1,000, 1,000–1,250 and 1,500–1,750 mm of crop seasonal rainfall for attaining sustainable productivity of upland rice under rainfed conditions in moist subhumid alfisols.