Optimizing deficit irrigation and regulated deficit irrigation methods increases water productivity in maize

At present, maize yields as high as 15.0 Mg ha-1 can be achieved under fully irrigated conditions in China. However, due to water restrictions, exploring appropriate water-saving irrigation methods is of great signifi-cance. Here, we sought to test the ability of several irrigation regimes to maintain high grain yield while increasing water productivity (WPc). Two water-saving irrigation methods, deficit irrigation (DI) and regulated deficit irrigation (RDI), were optimized based on changes in maize water consumption and soil water content over the growing season. The experiments were carried out in one of China's primary spring maize-producing areas (Qitai, Xinjiang) in 2019 and 2020, with mulched drip irrigation and dense planting (12 x 104 plants ha-1) adopted in both experiments. The control (CK) treatment consisted of the application of 540 mm of water during each irrigation interval. Compared with CK, the soil water content (SWC) in the 0-100 cm (particularly 0-60 cm) soil layers were lower during the water-insensitive growth periods (6th leaf-tasseling and milk-maturity stage) under both optimized DI and RDI. Furthermore, the daily crop evapotranspiration (DCE), phase water-consumption coefficient (Kp), and ineffective crop evapotranspiration (ETc) were reduced by 12.6-35.1%, 3.4-9.9%, and 6.7-16.6%, respectively. Both the maximum leaf area index (LAImax) and biomass accumulation were maintained during the 6th leaf-milk stage. Under optimized DI and RDI, high maize yield was maintained (>15.0 Mg ha-1), WPc was increased (>2.7 Kg m- 3), and irrigation water productivity (WPI) was increased by 10.3-33.4% and 36.0-41.3%, respectively. Optimized DI resulted in higher maize yields, but optimized RDI used less irrigation water. We propose that these optimized irrigation methods can improve maize yield and WPc in arid and semi-arid production areas.

Automated summary

Currently, maize yields as high as 15.0 Mg ha-1 can be achieved under fully irrigated conditions in China. However, due to water restrictions, exploring appropriate water-saving irrigation methods is crucial. This study tested the effectiveness of deficit irrigation (DI) and regulated deficit irrigation (RDI) in maintaining high grain yield and increasing water productivity (WPc). The experiments were carried out in a maize-producing area in Xinjiang, China, with mulched drip irrigation and dense planting adopted. The results showed that optimized DI and RDI reduced soil water content (SWC) and crop evapotranspiration (ETc), while maintaining high maize yield and increasing WPc and irrigation water productivity (WPI).