Optimal Irrigation Levels Can Improve Maize Growth, Yield, and Water Use Efficiency under Drip Irrigation in Northwest China

Drip irrigation systems are becoming more and more mature, and are presently extensively applied to increase crop yield and water use efficiency. In order to investigate the effects of irrigation quota on maize growth, the grain yield, and the water use efficiency (WUE), a field experiment with four irrigation quotas (T1 420 mm, T2 480 mm, T3 540 mm, and T4 600 mm) was conducted from 2013 to 2021 in Xinjiang, China. The results showed significant changes in maize growth, yield, and WUE in response to different irrigation quotas. The plant height, leaf area index, soil and plant analyzer development (SPAD), dry matter accumulation, yield, and harvest index of maize at different irrigation quotas all showed a ‘single peak curve’, and its change was closely related to the irrigation level. The growth index, dry matter accumulation, yield, and irrigation water use efficiency with T3 were the highest. The dry matter transfer efficiency, contribution of dry matter translocation to grain, and the harvest index with T3 showed a significant increase of 13.86%, 26.06%, 29.93%, and 7.62% compared to T1, respectively. In comparison to T1, T2, and T4, the yield of T3 increased by 32.17%, 13.54%, and 11.27%, respectively, and the WUE increased by 16.56%, 6.49%, and 23.70%, respectively. The significant correlations established between the maize yield and irrigation quotas could be simulated by a Kuznets-style relation. The maize yield was negatively correlated with irrigation quotas. When the irrigation quota (x) was 539.12 mm, the maize yield (y) was 16043.92 kg·hm⁻². These results demonstrate that the optimized irrigation quota (540 mm) can effectively improve the growth, yield, and WUE of drip irrigation maize in northwest China. Meanwhile, it can provide a theoretical reference and data support for the optimal amount of irrigation for drip irrigation maize in Xinjiang China.