Excessive application of nitrogen (N) fertilizer is the main cause of N loss and poor use efficiency in winter wheat (Triticum aestivum L.) production in the North China Plain (NCP).  Drip fertigation is considered to be an effective method for improving N use efficiency and reducing losses, while the performance of drip fertigation in winter wheat is limited by poor N scheduling.  A two-year field experiment was conducted to evaluate the growth, development and yield of drip-fertigated winter wheat under different split urea (46% N, 240 kg ha^–1) applications.  The six treatments consisted of five fertigation N application scheduling programs and one slow-release fertilizer (SRF) application.  The five N scheduling treatments were N0–100 (0% at sowing and 100% at jointing/booting), N25–75 (25% at sowing and 75% at jointing and booting), N50–50 (50% at sowing and 50% at jointing/booting), N75–25 (75% at sowing and 25 at jointing/booting), and N100–0 (100% at sowing and 0% at jointing/booting).  The SRF (43% N, 240 kg ha^–1) was only used as fertilizer at sowing.  Split N application significantly (P<0.05) affected wheat grain yield, yield components, aboveground biomass (ABM), water use efficiency (WUE) and nitrogen partial factor productivity (NPFP).  The N50–50 and SRF treatments respectively had the highest yield (8.84 and 8.85 t ha^–1), ABM (20.67 and 20.83 t ha^–1), WUE (2.28 and 2.17 kg m^–3) and NPFP (36.82 and 36.88 kg kg^–1).  This work provided substantial evidence that urea-N applied in equal splits between basal and topdressing doses compete economically with the highly expensive SRF for fertilization of winter wheat crops.  Although the single-dose SRF could reduce labor costs involved with the traditional method of manual spreading, the drip fertigation system used in this study with the N50–50 treatment provides an option for farmers to maintain wheat production in the NCP.

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 N_0-100 (100% at jointing/booting), N_25-75 (25% at sowing and 75% at jointing/booting), N_50-50 (50% at sowing and 50% at jointing/booting), N_75-25 (75% at sowing and 25% at jointing/booting), N_100-0 (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 N_50-50 treatment was more beneficial for winter wheat post-anthesis grain weight variation than the N_100-0 and N_0-100 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 I₄₅N_50-50 treatment in 2020-2021 and 2021-2022, respectively.  The grain crude protein was higher in the I₄₅SRF₁₀₀ treatment during the two seasons.  The I₄₅N_100-0 significantly (P<0.05) enhanced the content of grain total starch by 7.30 and 8.23% compared with the I₄₅N_0-100 and I₃₀N_0-100 treatments, respectively during the 2021-2021 season.  The I₄₅N_100-0 significantly (P<0.05) enhanced the content of grain total starch concentration by 7.77%, 7.62 and 7.88% in comparison with the I₄₅N_0-100, I₃₀N_0-100, and I₃₀N_25-75 treatments, respectively in the 2021-2022 season. Considering the principal component analysis (PCL), the N_50-50 split N-fertigation mode could be an optional choice for farmers during winter wheat production via drip irrigation.