Suitable split nitrogen application increases grain yield and photosynthetic capacity in drip-irrigated winter wheat ( 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 ( 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, 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 (Irrigation scheduling when ETa-P reaches 45 mm) and I (Irrigation scheduling when ETa-P reaches 30 mm). The six N levels were N (100% from jointing to booting), N (25% during sowing and 75% from jointing to booting), N (50% during sowing and 50% from jointing to booting), N (75% during sowing and 25% from jointing to booting), N (100% during sowing), and SRF (240 ha, 43% N during sowing). N top-dressing application significantly (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 IN and ISRF treatments, respectively had the highest GY (9.83 and 9.5 t ha), ABM (19.91 and 19.79 t ha), net photosynthetic rate (35.92 and 34.59 µmol ms), stomatal conductance (1.387 and 1.223 mol ms), (69.33 and 64.03), and chlorophyll fluorescence (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 IN treatment offers to farmers an option to sustain wheat production in the NCP.