Suitable split nitrogen application increases grain yield and photosynthetic capacity in drip-irrigated winter wheat (Triticum aestivum L.) under different water regimes in the North China Plain

Chemical fertilizer overuse is a major environmental threat, critically polluting soil and water resources. An optimization of nitrogen (N) fertilizer application in winter wheat (Triticum aestivum L.) in association with various irrigation scheduling is a potential approach in this regard. A 2-year field experiment was carried out to assess the growth, yield and photosynthetic capacity of drip-irrigated winter wheat subjected to various split applications of urea (240 kg ha(−1), 46% N). The eight treatments were, two irrigation scheduling and six N application modes in which, one slow-release fertilizer (SRF). Irrigation scheduling was based on the difference between actual crop evapotranspiration and precipitation (ETa-P). The two irrigation scheduling were I(45) (Irrigation scheduling when ETa-P reaches 45 mm) and I(30) (Irrigation scheduling when ETa-P reaches 30 mm). The six N levels were N(0-100) (100% from jointing to booting), N(25-75) (25% during sowing and 75% from jointing to booting), N(50-50) (50% during sowing and 50% from jointing to booting), N(75-25) (75% during sowing and 25% from jointing to booting), N(100-0) (100% during sowing), and SRF(100) (240( kg) ha(−1), 43% N during sowing). N top-dressing application significantly (P<0.05) influenced wheat growth, aboveground biomass (ABM), grain yield (GY) and its components, photosynthetic and chlorophyll parameters, and plant nutrient content. According to the averages of the two winter wheat-growing seasons, the I(45)N(50-50) and I(45)SRF(100) treatments, respectively had the highest GY (9.83 and 9.5 t ha(−1)), ABM (19.91 and 19.79 t ha(−1)), net photosynthetic rate (35.92 and 34.59 µmol m(−2)s(−1)), stomatal conductance (1.387 and 1.223 mol m(−2)s(−1)), SPAD (69.33 and 64.03), and chlorophyll fluorescence F(V)/F(M) (8.901 and 8.922). The present study provided convincing confirmation that N applied equally in splits at basal-top-dressing rates could be a desirable N application mode under drip irrigation system and could economically compete with the costly SRF for winter wheat fertilization. The I(45)N(50-50) treatment offers to farmers an option to sustain wheat production in the NCP.