An integrated model to optimize irrigation amount and time in shallow groundwater area under drought conditions

Drought is one of the main factors negatively affecting crop growth. Optimizing irrigation time and irrigation amount are two effective ways to improve crop yield and water use efficiency. In order to achieve process-based optimization in shallow groundwater area, a comprehensive model is established by combining EPIC crop growth module, soil and groundwater water-salt balance models, and multi-objectives 0-1 programming. Multi-objectives are set to maximize crop biomass accumulated in drought period and improve water use efficiency for saving water. The irrigation amount and irrigation time of maize during drought periods are optimized by the day. The results indicate that soil salinization can aggravate the water stress to crops. The optimized schemes show the significant difference of total biomass and water use efficiency when irrigating at different time during drought conditions. Water sensitivity coefficients can be used to roughly guide the irrigation strategies that irrigation should be conducted as early as possible during water sensitive periods, so as to guarantee the high crop biomass and water use efficiency. The integrated model established in this study provides a reference approach for optimizing irrigation time and irrigation amount based on dynamic changes. The established model and obtained results in this study seek to potentially provide effective strategies combating agricultural droughts.