STUDY ON FERTILIZER RATES FOR GETTING MAXIMUM GRAIN YIELD AND PROFITABILITY OF RICE PRODUCTION

Generally, fertilizer is the major factor affected on grain yield, quality and rice production cost. Intensive rice production in sustainable agriculture requires the appropriated fertilizer input that is not only for getting high grain yield but also for attaining maximum profitability. The experiments were conducted on two soil types of Mekong Delta: Alluvium soil at Chau thanh, An giang and slightly acid sulfate soil at Codo, Can tho. The experiment treatments were the combination of five N fertilizer rates (0, 30, 50, 70 and 90 kg N/ha), four phosphorus rates (0, 30, 50 and 70 kg P2O5/ha) and four potassium rates (0, 30, 50 and 70 kg K2O/ha) on the background of organic fertilizer of VIDAGRO (0.5t/ha) with the following composition: 45% of organic matter, 10%, of total N and extractable K of 3.5%. They were designed in a randomized completed block with three replications. The results showed that the grain yield varied from 5.77 to 6.05 t/ha on the slightly acid sulfate soil. The fertilizer rates of 80-120 kg N/ha, 30-70 kg P2O5/ha, 30-50 kg K2O/ha with the treatments of O.F+50-50-50, O.F+50-50-30 and O.F+50-30-30 kg N-P2O5-K2O/ha got high grain yield and maximum profit as compared to others. On the alluvium soil in An giang, the grain yield was higher than that of Can tho site. The high grain yield and maximum profitability were recorded at the following fertilizer doses: 100-120 kg N/ha, 30-50 kg P2O5/ha, 30-70 kg K2O/ha. The treatments of O.F+50-30-50, O.F+50-50-30, O.F+70-5050, and O.F+50-50-70 kg N- P2O5-K2O/ha were the best for both grain yield and profitability.