Rational regulation of nitrogen input represents a crucial approach for simultaneously boosting cereal productivity and enhancing the efficiency of agricultural input use. Nevertheless, the intrinsic mechanisms of how nitrogen application regimes in the North China Plain (NCP) regulate grain yield and nitrogen use efficiency (NUE) of winter wheat (Triticum aestivum L.) by modulating tiller physiological traits remain elusive. A two-year field experiment from 2023 to 2025 was carried out with four nitrogen application levels: conventional rate of 210 kg N ha−1 (N2), 10% nitrogen increase (N1), 10% nitrogen reduction (N3), and 20% nitrogen reduction (N4). Physiological traits of the wheat population were systematically investigated, and the correlations among grain yield, NUE and physiological indices were analyzed. The results indicated that moderate nitrogen reduction (N3) effectively inhibited ineffective tillers and maintained sufficiently stable stems at maturity. Meanwhile, N3 enhanced flag leaf photosynthesis, sucrose synthase and sucrose phosphate synthase activities, delayed flag leaf senescence during mid-late grain filling, and facilitated grain photoassimilate accumulation. On average across two years, N3 increased yield by 6.53% and 9.49% compared with N1 and N4, showing no remarkable difference from N2, while achieving the highest NUE. Further analysis demonstrated that tiller establishment and photoassimilate accumulation dominate wheat yield formation. In conclusion, optimized nitrogen management of N3 realizes synergistic improvement of yield and NUE, reduces agricultural resource input, and promotes sustainable green development of winter wheat production in the NCP.
Zhang et al. (Fri,) studied this question.