Adopting Minimum Irrigation Strategy for Sustainable Underground Water Use in the North China Plain.

Winter wheat and summer maize form the annual double cropping system in the North China Plain. The annual water requirements of the two crops are around 800-850 mm, while the annual rainfall is around 450-600 mm. Supplemental irrigation is required for the high yielding of the two crops and annually 200-300 mm water was pumped from underground for irrigation. Rapid decline in groundwater level was observed that threatens the sustainable irrigation agricultural development in this region. Field experiment was conducted from 1997 to 2016 to examine the crop performance under minimum irrigation strategy, which was to irrigate winter wheat and maize only once at sowing to maintain good germination for continuous 20 seasons. The average yield for winter wheat was 4991.3 kg/ha under minimum irrigation and 6875.2 kg/ha under full irrigation, with the corresponding seasonal evapotranspiration (ET) of 268.7 mm and 416.2 mm, respectively. The average yield for maize was 6750.8 kg/ha under minimum and 7516.1 kg/ha under full irrigation, and the corresponding evapotranspiration was 341.2 mm and 448.1 mm. The average annual ET was 609.8 mm under minimum and 864.3 mm under full irrigation treatment. The average annual yield production was 11742.1 kg/ha and 14391.3 kg/ha, respectively, for the two irrigation strategies. The reduction in ET was around 40% with annual yield penalty around 22%. The results indicated the minimum irrigation strategy could significantly reduce the irrigation water use, with less reduction in yield. The significant reduction in annual crop water use under minimum irrigation strategy would maintain the sustainable groundwater use in the North China Plain.