Increasing Topdressing Ratio of Nitrogen Fertilizer Improves Grain Yield and Nitrogen Use Efficiency of Winter Wheat Under Winter and Spring Night-Warming

Increasing nitrogen (N) topdressing ratio may be an effective cultivation method to enhance wheat yield and N use efficiency (NUE) under global asymmetric warming due to the lower N demands of wheat at seedling stage.

A two-year field experiment was conducted to investigate the effects of different basal and topdressing N ratios under winter and spring night-warming on grain yield and NUE of winter wheat.

Increasing N topdressing ratio under winter and spring night-warming improved grain yield by enhancing grain number per spike and 1000-grain weight, and winter night-warming exhibited a greater increase than spring night-warming. Increasing N topdressing ratio under night-warming facilitated post-anthesis dry matter accumulation by enhancing post-anthesis net photosynthetic rate and chlorophyll fluorescence parameters of flag leaves, leading to improved grain yield. Moreover, increasing N topdressing ratio under night-warming enhanced the capacity of pre-anthesis N uptake and post-anthesis N metabolism, improved the post-jointing upper root growth, and post-anthesis soil inorganic N content while reduced the apparent N surplus, together distributed more N to leaves at anthesis to improve the NUE.

Our findings suggest that increasing N topdressing ratio under winter and spring night-warming can improve grain yield and NUE caused by enhanced photosynthetic capacity, roots growth, and N uptake and assimilation.