Performance of basmati rice (Oryza sativa) under variable irrigation and nitrogen management

A field experiment was conducted during the rainy seasons (kharif) of 2021 and 2022 at research farm of ICARIndian Agricultural Research Institute, New Delhi to study the effect of irrigation regimes and integrated use of prilled urea and nano-urea as a source of N, on productivity and profitability of basmati rice (Oryza sativa L.). The experiment was conducted in a three-time replicated split-plot design (SPD) comprised of 3 irrigation regimes, viz. irrigation at 1, 3 and 6 days after disappearance of surface water (DADSW) assigned to main-plots and 4 N-management variants including; 100% RDN (recommended dose of N, 120 kg/ha); 75% RDN + 4% nano-urea (NU) 2 sprays (75% RDN + 2 NU); 50% RDN + 2 NU; and no-N (control) in sub-plots. Irrigating basmati rice 1 DADSW exhibited the highest panicle weight (2.67-3.09 g) and number of grains/panicle (115.9, 109.8), across the years, respectively that were significantly higher than 3 and 6 DADSW. The most delayed irrigation at 6 DADSW caused significant reduction in grain yield, the magnitude of reduction was 13-19% over irrigation at 3 DADSW and substantially by 23-28% over 1 DADSW. Fertilizing rice crop with 100% RDN and 75% RDN + 2 NU resulted in statistically similar yield attributes and grain yield; however, both were, significantly superior to 50% RDN + 2 NU and no-N. Net returns, benefit cost (B:C) ratio and monetary efficiency were significantly higher when crop was irrigated 1 DADSW than 3 and 6 DADSW. The N-management options followed the trend as RDN>75% RDN + 2 NU >50% RDN > no-N for all studied economic parameters.