Assessment of the sustainability of different cropping systems under three irrigation strategies in the North China Plain under climate change

The annual double-cropping system of winter wheat and summer maize requires a large amount of irrigation which has led to the rapid depletion of groundwater resources in the North China Plain (NCP). Alternate cropping systems and limited irrigation strategies should be developed for the purposes of maintaining sustainable groundwater use now and in the future. In this study, the water use and crop production of seven cropping systems under three irrigation strategies were assessed using the Agricultural Production Systems SIMulator (APSIM) during 1987-2017 as a baseline and in 2040, 2060, and 2080 under climate change conditions at a typical site in the NCP. The APSIM was calibrated and validated using field experimental data collected during 2007-2016. The seven cropping systems included the current double annual cropping system (2C/1Y) and six other reduced cropping-intensity systems with either three crops every two years (3C/2Y) or one crop per year (1C/1Y). The three irrigation strategies were full irrigation (FI), minimum irrigation (MI, only one irrigation at sowing for seedling establishment) and critical stage irrigation (CI, adding one more irrigation at the critical stage based on MI). The results showed that under current growing conditions, sustainable groundwater use could be achieved with 2C/1Y under MI, 3C/2Y and 1C/1Y under FI. However, the annual yield production was reduced by 9-22% under 3C/2Y and 54-79% under 1C/1Y compared with that under 2C/1Y. The results indicated that 2C/1Y was a better choice for crop production under similar water use. The simulated yield for future scenarios was lower than that during the baseline period; and the reduction rate varied from 2 to 11% under FI; 6-9% under CI; and 10-21% under MI, suggesting that crop production would be more negatively affected under water-limited conditions than that under full water supply condition. The annual water use of the reduced cropping systems was projected to increase because of relative high soil evaporation during the fallow period (Ef). Water use efficiency (WUE) was reduced partly due to the increased Ef. The traditional 2C/1Y under MI had the potential to sustain the groundwater balance in the region and concurrently resulted in higher grain production and WUE than that of the systems with reduced cropping intensity, both now and under climate change, and therefore, this system should be prioritized in this region.