Reducing nitrate (N) leaching is important for reducing pollution sources to groundwater worldwide. For the annual double cropping system of winter wheat and summer maize in the North China Plain (NCP), irrigation management in the dry winter wheat growing season affects the water balance in the summer rainy maize growing season and therefore influences the water drainage and N leaching from the crop root zone. Measurement data from a field experiment with three irrigation schedules for winter wheat and maize from 2006 to 2009 were used to calibrate and validate the APSIM model (Agricultural Production Systems sIMulator). The evaluated model was used to simulate the long-term effects of different irrigation schedules for the winter wheat season on N leaching during the summer maize season from 1981 to 2018, and to investigate strategies with minimum irrigation to maintain crop yield while reducing N leaching. Simulation results showed that when irrigation application to winter wheat was less than twice (total irrigation amount being less than 140 mm during the growing season), soil water depletion by winter wheat was greater than 130 mm for the top 2 m soil profile, which led to a significant reduction in drainage and N leaching during the summer rainy season. The average drainage during the summer maize season varied from 1 mm up to 134 mm following rainfed to five irrigations during the winter wheat season. The average N leaching corresponding to the drainage changes varied from 0.6 kg/ha to 67.1 kg/ha. The results indicated that the reduction in irrigation water use during the dry season significantly increased soil water use, allowing more rainfall to be stored in the mot zone soil profile without being leached during the rainy season. Although the reduction in irrigation water use reduced the yield of winter wheat, using moderate irrigation scheduling (one or two irrigations) significantly improved water use efficiency for grain yield with only a small yield penalty. Therefore, reducing the N leaching potential by increasing soil water use through irrigation management is an effective measure in the NCP.
