Impact of different cropping systems and irrigation schedules on evapotranspiration, grain yield and groundwater level in the North China Plain

Water shortage is the most limiting factors for the crop production in the North China Plain (NCP). The alternative cropping systems and the water-saving irrigation schedules are the main measures to reduce the groundwater level decline. In this study, APSIM model was used to simulate the effects of four different cropping systems (winter wheat and summer maize cropping system (WW-SM); winter wheat cropping system (WW); summer maize cropping system (SM); winter wheat summer maize spring maize cropping systems (WW-SM-sM)) under four different irrigation schedules (normal irrigation (NI); critical irrigation (CI); minimum irrigation (MI); and rain-fed (RF)) on evapotranspiration (ET), water use efficiency (WUE) groundwater table level and crop water productivities in the NCP. Results showed that the WW-SM cropping system had the higher grain yield and ET under NI, CI, MI, and RF conditions. Grain yield reduction (GYR) was decreased with the irrigation amount decreased for the WW cropping system, SM cropping system, and WW-SM-Sm cropping systems which ranged from 21.59% to 48.11%, from 16.71% to 46.93%, from 15.82% to 43.92%, and from 5.09% to 27.22% under the NI, CI, MI and RF irrigation schedules, respectively. For WOE and the economic water use efficiency (WUEe), WW-SM and WW-SM-sM had the higher value, WW and SM had the lower value. The differences for the different cropping systems were mostly caused by the grain yield and the soil evaporation. Meanwhile, the water-saving irrigation schedules and cropping systems both could reduce the groundwater table decline compared to that under normal irrigation and traditional cropping system. There all had the significant impact on groundwater table changes for both the irrigation schedules and cropping systems. However, water restriction will lead to crop yield reduction and water saving depending on the chosen alternative cropping systems and irrigation schedules. Results strongly suggest that the critical irrigation and WW-SM-sM cropping system could mitigate the groundwater over-exploitation and ensure the food safety in the NCP.