Responses of grain yield and water-nitrogen dynamic of drip-irrigated winter wheat (Triticum aestivum L.) to different nitrogen fertigation and water regimes in the North China Plain

The North China Plain (NCP) has progressively implemented drip irrigation for winter wheat (Triticum aestivum L.) production because of its substantial irrigation water saving and improved water and nitrogen (N) use efficiency. Nevertheless, the ideal water-N utilization regime for drip-irrigated winter wheat remains ambiguous. Two years of field experiments were carried out to assess the influences of different N fertigation and water regimes on winter wheat grain yield (GY), evapotranspiration (ETc), water-N productivity, and optimization procedure (TOPSIS). The two irrigation quotas were I45 (Irrigation when ETc reaches 45 mm) and I30 (Irrigation when ETc reaches 30 mm). The six-N application modes were N0-100 (100 % from jointing to booting), N25-75 (25 % at sowing and 75 % from jointing to booting), N50-50 (50 % at sowing and 50 % from jointing to booting), N75-25 (75 % at sowing and 25 % from jointing to booting), N100-0 (100 % at sowing), and SRF100 (240 kg ha-1, 43 % N at sowing). Results demonstrated that optimizing irrigation and N application regimes positively influenced wheat GY, ETc, and water-N productivity. The maximum GY of 9.72 and 9.94 (t ha-1) was achieved in I45N50-50, which had ETc of 376.67 and 378.67 (mm), in 2020-2021 and 2021-2022, respectively. The TOPIS designated I45N50-50 as the best treatment (ranked 1st) based on high GY and minimized ETc. Based on the two years average, the I45N50-50 treatment also resulted in the highest water use efficiency (2.61 kg m- 3), irrigation water use efficiency (3.74 kg m- 3), and partial factor productivity of nitrogen (40.99 kg kg-1). Considering comprehensively GY, ETc, and water-N productivity, the combination of split N application as 50 % of basal and 50 % of topdressing and 45 mm irrigation quota was an optional choice for winter wheat production under drip irrigation system. These findings could serve as a scientific foundation for water-N management of drip-irrigated wheat in the NCP.