The coupled effects of various irrigation scheduling and split nitrogen fertilization modes on post-anthesis grain weight variation, yield, and grain quality of drip-irrigated winter wheat (Triticum aestivum L.) in the North China Plain

Irrigation methods and nitrogen (N) fertilization modes have a complicated impact on wheat physiology, growth, and development, leading to the regulation of wheat grain yield and quality. However, the optional water-N combination for drip-irrigated winter wheat remains unclear. A two-year fieldwork was conducted to evaluate the influences of various N-fertigation and water regimes on wheat post-anthesis grain weight variation, yield, grain NPK content, and grain quality. The two irrigation quotas were I45 (Irrigation when ETa-P reaches 45 mm) and I30 (Irrigation when ETa-P reaches 30 mm) and the six N application rates were N0-100 (100% at jointing/booting), N25-75 (25% at sowing and 75% at jointing/booting), N50-50 (50% at sowing and 50% at jointing/booting), N75-25 (75% at sowing and 25% at jointing/booting), N100-0 (100% at sowing), and SRF100 (100% of slow release fertilizer at sowing). The experimental findings showed that post-anthesis grain weight variation, grain yield, grain NPK content, and grain quality were markedly influenced by the various irrigation scheduling and N-fertilization modes. The N50-50 treatment was more beneficial for winter wheat post-anthesis grain weight variation than the N100-0 and N0-100 treatments under the two irrigation quotas and during the two seasons. The highest grain yield of 9.72 and 9.94 (t ha−1) were obtained with the I45N50-50 treatment in 2020-2021 and 2021-2022, respectively. The grain crude protein was higher in the I45SRF100 treatment during the two seasons. The I45N100-0 significantly (P<0.05) enhanced the content of grain total starch by 7.30 and 8.23% compared with the I45N0-100 and I30N0-100 treatments, respectively during the 2021-2021 season. The I45N100-0 significantly (P<0.05) enhanced the content of grain total starch concentration by 7.77%, 7.62 and 7.88% in comparison with the I45N0-100, I30N0-100, and I30N25-75 treatments, respectively in the 2021-2022 season. Considering the principal component analysis (PCL), the N50-50 split N-fertigation mode could be an optional choice for farmers during winter wheat production via drip irrigation.