Coordinating yield and quality formation of wheat through post-anthesis nitrogen spraying

It is a challenge to maintain high yields while improving grain quality of wheat under limited water and nitrogen supply conditions. To achieve a simultaneous improvement of yield and quality, a field trial was conducted from 2021 to 2023. Treatments with different timings (5, 10, and 15 ​d after anthesis) and frequencies of spraying nitrogen (1, 2, and 3 times) were set up after anthesis under a water-saving cultivation system. Spraying nitrogen after anthesis significantly increased grain yield and protein content by 4.99% and 6.00%, respectively. The increase in grain yield was mainly due to the improvement in grain weight, which was attributed to increased grain filling and starch synthesis. Spraying nitrogen once at 15 ​d after anthesis (T_{15 D}) was optimal. T_{15 D} treatment increased the photosynthetic pigment content and the enzyme activities of carbon and nitrogen metabolism of the flag leaves. T_{15 D} increased the pre-anthesis nitrogen remobilization to grains by 4.71%–9.06% compared to the other spraying treatments, and promoted the accumulation of nitrogen in the grains. Moreover, T_{15 D} optimized the protein composition of the grains and improved processing quality at maturity. In conclusion, spraying nitrogen at 15 ​d after anthesis may be an effective measure to simultaneously improve the yield and quality of winter wheat under a water-saving cultivation system.