Response of lowland rice (Oryza sativa L.) to fertilization when grown as main and ratoon crop

Ratooning is widely considered as a strategy to increase lowland rice productivity. However, limited studies have yet been conducted in the Philippines that focus on the fine tuning of this technology. Thus, this study was conducted to evaluate the growth and yield response of main and ratoon crop of lowland rice (PSB R082) to fertilization and to assess the profitability of lowland rice production when grown as main and ratoon crop as influenced by fertilization. Both main and ratoon crop were subjected to the following treatments: T0-No fertilizer application (Control), T1– 90-60-60kgha-1 N, P2O5 and K2O (Inorganic Fertilizer), T2– 10tha-1 Organic Fertilizer, T3– 5tha-1 Organic Fertilizer + 45-30-30 kgha-1 N, P2O2 and K2O. Results revealed that application of inorganic fertilizers at the rates of 90-60-60 and 45-30-30kgha-1 N, P2O5, K2O for the main and ratoon crops, respectively, significantly increased the leaf area index (LAI), number of productive tillers, weight of panicle, number of filled grains and grain yield. The combined application of organic and inorganic fertilizers produced taller plants, heavier straw yield, abundant number of productive tillers, heavy panicle and more filled grains. Plants applied with inorganic fertilizer at the rate of 90-60-60kgha-11 N, P2O3, K2O for the main crop and 45-30-30kgha-1 of N, P2O5, K3O for the ratoon crop resulted in the highest net income.