Assessing irrigated water utilization to optimize irrigation schedule in the oasis-desert ecotone of Hexi Corridor of China

Water is the key factor limiting crop production in arid inland river basins of northwestern China, where water scarcity challenges food security and the sustainability of eco-environment. Changing the chronical management strategies is urgent to realize more crop per drop and to satisfy ecological water requirement in the Hexi Corridor, where agriculture relied heavily on irrigation using groundwater. Long-term observations of soil water balance components and crop production are lack but essential to optimize irrigation schedules with moderate groundwater recharge. AquaCrop model was calibrated and validated using field data on spring wheat and spring maize rotation in the midstream of the Heihe River from 2005 to 2014, and used to assess current irrigation practices and to generate optimal deficit irrigation schedules. Simulations of soil water balance, canopy progression, biomass accumulation and yield production over time well mimicked the water utilization and crop development. Plastic mulching prevented 53.5% and 62.6% of potential soil evaporation for spring wheat and spring maize, respectively. Temporary water logging soon after irrigation reduced transpiration by restricting canopy development and stomatal conductance. No more than 30% of water supply was used by crops, but drainage below mot zone occupied more than 68% of water supply by present. Mean biomass water use efficiency (WUE) was 0.034 kg m(-3) and 0.047 kg m(-3), and mean yield WUE was 1.16 kg m(-3) and 2.41 kg m(-3) for spring wheat and spring maize, respectively. Cultivar "2014" for spring wheat and cultivar "8703" for spring maize were suitable for yield production in this area. Beyond 50% of applied water would be productively used with reduction of drainage in water supply by more than 25% under the modified irrigation schedules. Total amount of applied water reduced by about 50%, but the biomass and yield values would remain unchanged. These irrigation schedules will greatly improve WUE of irrigated agriculture, supporting the rational allocation of water resources of the inland river basins at a watershed scale.