Optimization of nitrogen fertilization for aerobic rice (Oryza sativa)

Field experiments were conducted during the rainy (kharif) seasons of 2014 and 2015 at Aduthurai, Tamil Nadu, to assess the efficiency of N scheduling and dosage for aerobic rice (Oryza sativa L.) cultivation. The soil was clay loam. The experiments were laid out in a split-plot design with 3 replications. The main plot treatments consisted of 4 nitrogen(N) levels and the subplots 6 N split doses. Among the N levels, application of 200 kg N/ha registered higher growth parameters, N uptake and yield attributes. The growth attributes of aerobic rice increased with the increased N dose up to 200 kg N/ha and was comparable with 175 and 150 kg N/ha. The higher grain yield and benefit: cost (B: C) ratio were observed with the application of 175 kg N/ha. Among the split doses, N at 4 splits (1/4 at 10–12 days after emergence + 1/4 at active tillering stage + 1/4 at panicle-initiation stage + 1/4 at flowering) recorded higher growth parameters, yield attributes, grain yield, gross returns, net returns and eventually higher B: C ratio. Achieving higher yield with remunerative B: C ratio, a nitrogen dose of 175 kg N/ha in 4 splits 1/4 at 10–12 days after emergence + 1/4 at active tillering stage + 1/4 at panicle-initiation stage + 1/4 at flowering can be recommended for sustaining the aerobic rice yield.