Assessing the impacts of regulated deficit irrigation on soybean using AquaCrop

Deficit irrigation (DI) is a viable adaptation strategy to reduce agricultural water demand. Field experiments and subsequent data modelling help assess the impacts of DI on crop yield and water productivity (WPET). This study aims to simulate the potential impacts of climate change on soybean performance under full (FI) and regulated deficit (RDI) irrigation using 30-years (1993–2022) of historical climate data. The field experiment showed no significant difference in yield and actual water productivity (WPobs) between FI and RDI, with average values of 3447 kg ha⁻1 and 6.6 kg ha⁻1 mm⁻1, respectively. However, RDI saved about 22.5% of irrigation water. Additionally, the AquaCrop model accurately simulated the effects of FI and RDI on soybean performance in the last 30 years of climatic conditions. The 30-year simulations revealed that RDI reduced yield by an average of 4.0%, biomass by 4.8%, and WPET by 0.9% compared to FI. In contrast, RDI increased irrigation water saving by an average of 17.0% (-55 mm per year) and the irrigation water productivity (WPIrr) by 14.5% (+1.6 kg ha⁻1 mm⁻1). These results indicate that the AquaCrop model can effectively simulate the impacts of DI on soybean, making it a valuable tool in designing irrigation management plans as adaptation strategies to climate change and water scarcity.