Relative performance of granulated and nano urea on productivity and nitrogen use efficiency of wheat–rice sequence

The increasing reliance on nitrogen (N) fertilizers in modern wheat and rice varieties has raised concerns about grain quality and environmental sustainability. Nano-fertilizers, particularly nano-urea, have been suggested as alternative use to conventional urea. A two-year field study (2021–22 and 2022–23) was conducted at the ICAR-Indian Agricultural Research Institute, New Delhi, to assess the efficacy of granulated urea with and without nano-urea were tested with five nitrogen treatments (0 kg N ha^–1, 130 kg N ha^–1, 97.5 kg N ha^–1 + nano urea foliar spray, 65 kg N ha^–1 + nano urea spray, and 65 kg N ha^–1 + 2 % granulated urea spray). Results indicated that 130 kg N ha^–1 increased wheat and rice grain yields by 28.7 % and 29.4 %, respectively, and N uptake by 62 % in wheat and 52.4 % in rice compared to the control. However, the application of 65 kg ha^–1 + nano urea foliar sprays at the rate of 2.5 l ha^–1 recorded reduced grain yields, by 10.7 %, 9.4 % in wheat and rice, and N uptake decreased by 20.7 and 14.4 % in wheat and rice, respectively, in comparison to 130 kg N ha^–1. Additional net returns of 16.5 % and 16.1 %, along with a higher B: C, were observed with N applied at 130 kg ha^–1 as compared to the 65 kg N ha^–1 + nano urea. The study concludes that applying 130 kg N ha^–1 of granulated urea is more effective for improving grain yield, N uptake, and profitability in the wheat-rice system.