Simulating the exploration of the optimal irrigation of spring wheat in drought areas based on SWAP model

Water scarcity and low irrigation efficiency are the main factors causing yield losses in spring wheat in arid areas. To propose optimised irrigation scheduling for spring wheat in the arid areas of Ningxia, China, we first calibrated the SWAP (soil–water–atmosphere–plant) model and then utilised the well-tested SWAP model during three typical rainfall years to evaluate the 542 irrigation schemes. The results showed that the model performed well in simulating the plant height, leaf area index (LAI) and biomass of spring wheat under different water stress conditions. The R² values of the above three crop growth indicators were all greater than 0.89, and the normalised root mean square error (NRMSE) was less than 18% in the validation period. Additionally, the model achieved a high degree of accuracy in simulating the soil water content, evapotranspiration and yield, with RMSEs of 2%, 31 mm, and 326 kg/ha, respectively. The total irrigation amounts of 290, 320 and 350 mm with five, six and six irrigation times in the wet, average, and dry years, respectively, could achieve relatively high yields as well as improved water use efficiency (WUE) and irrigation water use efficiency (IWUE). The results can provide useful information for the efficient utilisation of irrigation water resources in arid areas.