Highly Efficient Water and Nitrogen Application Strategies for Maintaining Summer Maize Yield in the North China Plain During Future Drought Years

Future frequent droughts threaten summer maize production in the North China Plain (NCP). A proper combination of irrigation and nitrogen (N) application can improve water and N use efficiency while maintaining summer maize yield. However, the optimal irrigation and N application strategies (OINASs) for summer maize during future drought years in the NCP require further exploration. This study applied the DSSAT-CERES-Maize model to investigate OINASs for summer maize for all drought years during 2021–2050 under three shared socioeconomic pathways (SSP1-2.6, SSP2-4.5, and SSP5-8.5). The performance of the OINASs was subsequently evaluated against no irrigation and N application (CK) condition and a conventional irrigation and N application strategy (CINAS). The results highlight the following: (1) For all drought years under the three SSP scenarios, the base fertilizer rate should be 60 kg/hm², after that the irrigation and N application are required during the jointing and heading periods. Under the SSP1-2.6 scenario, the average values of irrigation and N application during each earlier period are 35.5 mm and 22 kg/hm². Under the SSP2-4.5 and SSP5-8.5 scenarios, the average values are (34.5 mm, 23 kg/hm²) and (47.5 mm, 18 kg/hm²). (2) Under all SSP scenarios, the optimal irrigation amounts and N application rates are much lower than those under the CINAS. After applying OINASs for summer maize, an average of 1.16–1.22 billion kg of N and 2.98–5.19 billion m³ of freshwater will be saved per future drought year in the NCP. (3) Under all SSP scenarios, the summer maize yields under the OINASs are slightly and significantly greater than those under the CINAS and CK conditions. Moreover, both water and N use efficiencies improved under the OINASs compared with those under the CINAS, with more significant improvements in N use efficiency. The OINASs provide a practical way to ensure food security and environmental sustainability.