Moderate soil drying improves physiological performances and kernel yield of maize

Water shortage is a serious problem in crop production, and maize (Zea mays L.) is the largest grain crop worldwide. It would have great significance in increasing kernel yield and water use efficiency to establish a high-yielding and water-saving irrigation technology in maize. In this study, two high-yielding maize varieties were used and two irrigation regimes composed of well-watered (WW) and moderate soil drying (MD) were conducted. Physiological performances, kernel yield, and water use efficiency were investigated. Compared with WW, the MD increased kernel yield by 4.69–6.40%, reduced irrigation water by 26.5–33.3%, and improved irrigation water use efficiency by 43.1–59.3%. In terms of physiological performances, the MD enhanced the leaf superoxide dismutase (SOD) activity, decreased malondialdehyde (MDA) content, increased the leaf photosynthetic rate and the contents of indole-3-acetic acid (IAA), zeatin (Z) + zeatin riboside (ZR), gibberellin-3 (GA₃), and abscisic acid (ABA) in inferior kernels, promoted the remobilization of non-structural carbohydrates (NSC) from stalks and sheaths to kernels, and improved the filling rate and weight of inferior kernels. Correlation analysis showed that IAA, Z + ZR, and ABA contents in kernels were significantly and positively correlated with the kernel filling rate. These results suggest that the moderate soil drying imposed during the whole growth period of maize can achieve the dual goal of increasing food production and saving water by improving physiological performance, especially regulating hormonal levels in the kernel.