Reduced nitrogen rate improves post-anthesis assimilates to grain and ameliorates grain-filling characteristics of winter wheat in dry land

Aims Nitrogen (N) fertilizer application greatly enhances grain yield by improving dry matter accumulation and grain filling in winter wheat. However, the regulation mechanism of N rates on dry matter accumulation, transportation, and grain filling in winter wheat under dry farming could be more precise. Methods Five N treatments viz. 0, 75, 150, 225, and 300 kg center dot N center dot ha(-1), designated as N0, N75, N150, N225, and N300, were tested in two growing seasons of 201718 and 2018-19. Results Fertilization significantly increased dry matter accumulation and intensity and assimilated accumulation after anthesis and its contribution to grain yield. N fertilizer significantly improved the superior and inferior grain weights, with the highest at N225, and increased by 22.29% and 24.41% in 2017-18 and 22.06% and 12.68% in 2018-19, respectively, compared to N0 (P < 0.05). Moreover, N fertilization increased the initial grain-filling potential and mean filling rate, shortened the days achieving the maximal grain-filling rate. N fertilizer increased the filling rate in the three periods, shortening the duration of the first-middle period, prolonging the late period, and increasing the contribution of the midlate filling period to grain weight. However, excessive N application led to a reduction in the filling rate for each period. It prolonged the duration in the mid-late periods, which was not conducive to further increases in grain weight. Conclusions The N225 can be a more suitable N fertilizer for improving the accumulation and transfer of dry matter, promoting grain-filling, and increasing wheat yield in dry farming in the Loess Plateau.

Automated summary

Nitrogen fertilizer application can significantly enhance dry matter accumulation and grain filling in winter wheat, leading to increased yield. Under dry farming conditions, the appropriate nitrogen application can promote dry matter accumulation and transportation, facilitate grain filling, and improve winter wheat yield.