Grain yield, actual evapotranspiration and water productivity responses of maize crop to deficit irrigation: A global meta-analysis

Deficit irrigation (DI) has been implemented in arid regions to improve water productivity while maintaining or increasing crop yield. In this study, we carried out a global scale meta-analysis to (1) quantify the response ratios of grain yield (GY), actual crop evapotranspiration (ETc act) and water productivity (WP) under DI stress. Then, we (2) examined the effects of nitrogen (N), phosphorus (P) and potassium (K) fertilizer rates, climate, soil texture, DI application mode, and maize growing cycle on GY, ETc act and WP. A total of 1192 observations retrieved from 167 studies were used to estimate the effect size and generate forest plots for each factor at three different growth stages. The response ratio (RR) of maize GY was higher for short-cycle varieties (RR, 0.14), in semi-arid climates (RR, 0.25) and under irrigation amount reduction (RR, 0.21). Maize ETc act was higher for long and medium cycle varieties (RR, 0.22), for medium-textured soils (RR, 0.14) and drier climates. The WP improved by 9% on heavy soils compared to both light and medium soils, indicating that heavy soils are more suitable for growing maize under DI. This study highlights that high DI stress was often applied with low nitrogen rates to limit reciprocal effect on yield loss. The application of DI stress before the reproductive stage induced an adaptation strategy that limits maize yield loss and improves WP. Thus, the application of DI stress should start earlier at the vegetative stage to be more beneficial to maize. Furthermore, DI stress should target early-maturing maize varieties to achieve higher crop WP. The findings imply that DI stress could be a promising strategy for water management in maize cropping systems while considering appropriate soil, growing stages, varieties and climate.