Integrated water and nitrogen application increases summer maize (Zea mays L.) yield and water/nitrogen use efficiency under micro-sprinkling irrigation conditions

To improve the yield and water-nitrogen (N) use efficiency of summer maize, a two-year field experiment with four irrigation soil layers (0-10, 0-20, 0-30, and 0-40 cm, denoted as W-10, W-20, W-30, and W-40, respectively) and three N applications (180, 240, and 300 kg ha(-1), denoted as N-180, N-240, and N-300, respectively) was performed using micro-sprinkling irrigation system in 2018 and 2019. The interaction between water and N application significantly affects dry matter accumulation (DM). Under the same N application, the grain yield of W-10 was significantly lower than that of W-40. The irrigation amount and evapotranspiration for W20N180 and W20N240 significantly decreased by 47.18%-52.31% and 12.32%-12.68%, respectively, over that of W40N300, and water-use-efficiency (WUE) significantly increased by 7.75%-12.47%. Compared with N-180, the N partial factor productivity of N-240 and N-300 decreased by 21.02%similar to 22.04% and 37.12%similar to 38.24%, respectively; with no significant difference in yield. Grain yield was significantly positively correlated with leaf area index at tasseling, grains per ear, DM at maturity, and evapotranspiration. Overall, suitable irrigation (W-20) and N application (180-240 kg ha(-1)) can achieve higher grain yield and WUE for summer maize in the Huang-Huai-Hai Plain of China.