Optimized micro-sprinkling irrigation scheduling improves grain yield by increasing the uptake and utilization of water and nitrogen during grain filling in winter wheat

The North China Plain (NCP) is the main wheat production area in China; however, irrigation water and nitrogen fertilizer use in this area is relatively inefficient, and must be optimized to attain higher yield and resource use efficiency for winter wheat. In this study, a four-year field experiment was conducted during the 2012-2016 growing seasons. Under quota irrigation conditions, an experiment with various micro-sprinkling frequencies (S2, irrigation at jointing and anthesis; S3, irrigation at jointing, booting and filling; and S4, irrigation at jointing, booting, anthesis and filling) was conducted in 2012-2014. In 2014-2016, different nitrogen application rates (150, 195, and 240 kg N ha−1; denoted as S4N1, S4N2, and S4N3, respectively) under the S4 condition were tested. The local traditional flood irrigation pattern was designated as the control (CK) in 2012-2016. The grain yield, leaf area index of the population (LAI), flag leaf senescence during gain filling, accumulation and distribution of dry matter and nitrogen, and water and nitrogen use characteristics were investigated. The results showed that, no significant difference was observed in grain yield between the CK and S2, whereas S4 and S3 showed increased grain yields of 5.7-22.2% and 4.6-19.1%, respectively, compared with the CK. The increase of yield in micro-sprinkling treatments was mainly due to a significant increase in the 1000-grain weight. With increasing irrigation frequency, the LAI at the filling stage improved significantly; the flag leaf chlorophyll content decreased slowly; and the total dry matter accumulation, dry matter after anthesis, and its contribution to grain yield increased significantly. Meanwhile, the total water consumption of S4 (N2) decreased significantly, and the water use efficiency increased by 10.0-27.8% compared with the CK. In addition, micro-sprinkling irrigation with frequent application of a small amount of water with optimized nitrogen application (S4N2) yielded the highest nitrogen fertilizer use efficiency. Water consumption and nitrogen accumulation during grain filling were significantly increased in S4, which could explain the higher yield and resource use efficiency of S4. Overall, a suitable micro-sprinkling irrigation frequency (S4) and nitrogen application (195 kg N ha−1) can achieve higher grain yields and resource use efficiencies in the NCP.