AquaCrop modeling to explore optimal irrigation of winter wheat for improving grain yield and water productivity

Abstract

Water shortage is the main constraint resulting in low crop yields in arid and semiarid areas, where irrigation is essential to sustain agricultural production. Unreasonable irrigation will not effectively improve crop yield but will cause a waste of water resources and a decrease in water productivity. The objectives of this study were intended to investigate the variability of yield and water productivity (WP) as a function of irrigation amount, time, and frequency and to explore optimal irrigation of winter wheat for improving grain yield and water productivity over a 60-year of long-term meteorological data (1961—2020). A water-driven model, AquaCrop model, was used to reproduce crop growth and yield responses to changes in water supply, with a total of 625 irrigation scenarios of irrigation amount and time. The results showed that there has been no significant change in seasonal ET0 (reference evapotranspiration) of winter wheat over the last 60 years. Instead, seasonal precipitation during the winter wheat growing cycle displayed a decreasing trend, potentially increasing the risk of meteorological drought. Despite the crop ET has remained stable at around 370 mm for the past 60 seasons, the grain yield and WP have steadily increased as the cumulative temperature increased. In all three typical meteorological years, crop average yield and ET were considerably improved under irrigation conditions compared with that in non-irrigated (rainfed). The total irrigation amounts of 90, 120, and 150 mm with two irrigation times in the wet, normal, and dry years, respectively, could achieve higher yields as well as the WP and IWP. Consequently, the optimal irrigation schedules in the wet, normal, and dry years were determined to be first irrigation in the wintering stage with 90 mm and second irrigation in the jointing stage with 0, 30, 60 mm, respectively. This work demonstrates that the AquaCrop model has a reliable accuracy for revealing crop growth and production under water deficit conditions and provides a technical means of application for formulating optimal irrigation schedules.