Optimizing nitrogen application and sowing date can improve environmental sustainability and economic benefit in wheat-rice rotation

In wheat-rice rotation, late sowing and excessive nitrogen (N) application lead to low annual yield and additional fertilizer waste. A comprehensive assessment of yield sustainability, N use efficiency, N balancing mechanism, and economic benefit is urgent. To explore the feasibility of optimizing N application and sowing date to improve yield, N use efficiency, and economic benefit in wheat-rice rotation. A two-year experiment of wheat-rice rotation was conducted in China, involving four N application rates (0, 180, 240, and 300 kg ha−1), three sowing dates (normal, delayed, and late sowing), three planting density (1.2 × 104, 1.8 × 104, and 2.4 × 104 seeds ha−1) for wheat (Yangmai-23), and four N application rates (0, 135, 270, and 405 kg ha−1), three sowing dates (normal, delayed, and late sowing), and three varieties (Yongyou-2640, Wuyunjing-32, and Nanjing-9108) for rice. Treatments were imposed in a split-plot experiment design with three replications (except N0). Soil information, N uptake, and yield were obtained through field survey and sampling. In addition, N balance was studied based on measured data and Denitrification-Decomposition (DNDC) model. Reactive N emissions (NH3, N2O, and NO) simulated by DNDC were converted into environmental damage costs for annual economic analysis. Delaying sowing could reduce annual yield from 6.14% to 13.72%, while appropriate N application can mitigate this trend. However, delaying sowing promoted soil N accumulation and yield sustainability. N fertilizer addition and late sowing would reduce annual N physiologic efficiency by 45.98%, N recovery efficiency by 42.02%, and N agronomic efficiency by 68.10%, leading to N surplus. Applying more N not only increased annual yield (24.85%–39.44%) and profit (74.27%–162.16%) but also brought more reactive N damage cost (7.40%–25.14%). In this study, the appropriate N application rate for delayed sowing (WR-S2) and late sowing (WR-S3) were 510–705 kg N ha−1 and 315–510 kg N ha−1, respectively. Optimizing N fertilizer and sowing date is an easy-followed strategy for improving yield, N use efficiency, and economic benefit in wheat-rice rotation, which is highly-consistent with United Nations Sustainable Development Goals. This strategy is simple to implement for policy formulation on precision agriculture and highly-effective to manage.