Nitrogen management strategies improve yield and nitrogen use efficiency in double‐cropped rice

Abstract

The selection of high‐yielding cultivars is important for improving rice ( Oryza sativa L.) yield, yet the role of nitrogen (N) management, a key determinant of yield and nitrogen use efficiency (NUE), is often overlooked. Two field experiments were conducted on double‐cropped rice: Experiment 1 employed five N application rates (0–225 kg N  ha −1 ) to evaluate cultivar‐specific responses of five early‐season and five late‐season rice cultivars, while Experiment 2 used seven N application strategies with different frequencies and ratios to evaluate their effects on biomass, yield components, N uptake, and utilization. N fertilization significantly increased yield compared with N0. Maximum yields ranged from 5803 to 7614 kg ha −1 in early rice and from 7450 to 8713 kg ha −1 in late rice. Under the optimal N rate of 165 kg N ha −1 , average yields peaked, increasing 61.4% and 32.6% relative to N0. Optimal N rates differed among cultivars, ranging from 144 to 162 kg ha −1 for early rice and from 155 to 173 kg ha −1 for late rice. N application frequency and proportion affected yield and NUE, with the highest values achieved under 70% basal urea + 30% tiller urea for early rice and 50% basal urea + 30% tiller urea + 20% panicle urea for late rice. Compared with single basal urea application, the optimal N strategies increased biomass, yield, and N uptake by 7.9%, 10.2%, and 9.4% in early rice and by 13.8%, 17.0%, and 49.0% in late rice, respectively. Optimizing N strategies according to cultivar characteristics and application regimes improves productivity and nitrogen use efficiency in double‐cropped rice systems.