Nitrogen Fertilizer Optimization and Its Response to the Growth and Yield of Lowland Rice

Lowland rice (Oryza sativa L.) in South Asia is under stress, as nitrogen removals by crops are higher than their replenishment through fertilizers. Limited information is available on optimizing nitrogen dose in lowland rice to turn out higher yield. The present investigation aimed to optimize nitrogen fertilization and it’s response to the growth and yield of lowland rice. We evaluated two modern rice varieties (BRRI dhan28 and BRRI dhan29) under six nitrogen rates ranging from 0 to 250 kg ha-1 during the dry season. Positive response of nitrogen fertilization was observed in tiller and dry matter production from the early growing stage in both varieties. Tillering increased progressively with the advancement of growth stage and reached at the peak within 60 days after transplanting (DAT) in all cases. BRRI dhan28 and BRRI dhan29 achieved the highest dry matter at 75 and 90 DAT with 250 kg N ha-1. The relationship between N application and N uptake by plants became quite evident at 30 DAT and beyond. N uptake started to increase from 45 DAT and showed a peak at 75 DAT in both the varieties. Nitrogen application significantly increased the grain yield of both varieties. The highest yield of 5.15 and 6.34 Mg ha-1 was obtained with 150 kg N ha-1 in BRRI dhan28 and BRRI dhan29, respectively. However, the nitrogen dose was optimized at 156 and 158 kg ha-1 for BRRI dhan28 and BRRI dhan29, respectively.