Nitrogen (N) plays a vital role in plant growth; however, the yield response to N fertilizer is regularly declining in the major cropping systems due to overuse and the upper limit of yields. Heavy losses of N are also documented due to its excessive use in the rice-wheat rotation system, resulting in low nitrogen-use efficiencies (NUE) and environmental problems. Therefore, a three-year field experiment was performed with different N managements to investigate the impact of reduced N input rates in this exhaustive cropping system. Reducing the N application rates did not affect the wheat and rice yields significantly, only during the second wheat season was the yield slightly reduced as compared to higher N input treatments. Decreasing the N input rates in the prior crop and present crop, and the interactions of both rice and wheat seasons (R × W) did not influence the yields of either crop. A reduction in N fertilizer had a considerable impact on dry matter production during the wheat seasons but demonstrated no effect during the rice season. The accumulation of N was significantly reduced during both crop seasons by lowering the rate of N application. In addition, the NUE indices were significantly influenced by N fertilizer application rates. In conclusion, N fertilizer input rates for both rice and wheat crops can be lowered as compared to present fertilization rates without any risk of yield decline. Lowering the N input increases the NUE and effectively reduces N losses, and soil N status can also be maintained.

What strategy of nutrient management can maintain the high and stable annual yield in rice–wheat systems under climate change? A 10-year term experiment was conducted in the rice–wheat system to investigate the effect of optimal nutrient management on crop yield and meteorological drivers of year-to-year fluctuations in rice and wheat yield. Treatments were as follows: conventional fertilization (CF, as control), fertilizer postponing (FP, with the same amount fertilization as CF and increasing rate and times of panicle fertilizer) with/without straw incorporation (including only straw returned in rice (W) or wheat (R) season, and both straw incorporation (WS), RFP (reducing amount based on FP) with/without organic fertilizer. Results showed that FP with/without straw incorporation increased 10-year average yields of rice, wheat, and annual by 4.5~6.5%, 3.8~7.2%, and 4.8~6.8%, respectively, while RFP with/without organic fertilizer did not markedly reduce wheat yield, compared with CF. Effect of optimal treatments on wheat and rice yield stability was different; among the annual yield stability in FP + WRS was the greatest due to increasing and a stable number of spikelets and dry matter accumulation (DMA) after heading. Furthermore, the coefficient of variation (CV) of DMA during rice jointing-heading (21.6~30.0%) and heading-maturity stage (20.1~27.9%) was higher than before jointing (13.9~16.7%), which were affected by day photosynthetically active radiation (explain: 26%) and the number of rainy days (explain: 34%), respectively, using Stepwise regression; in contrast, in wheat season, the fluctuation of DMA before jointing was the highest (CV: 83.8~109.9% (before jointing) vs. 61.1~97.4% (heading-mature stage) vs. 33.7~46.3% (jointing-heading period), 55% of its variations was impacted by day-night temperature differences, the number of rainy days and photosynthetically active radiation accumulation. Our finding suggested that nutrient management to increase and stable the DMA after rice jointing and before wheat jointing could maintain the high and stable annual yield in rice–wheat systems.