An alternative water-fertilizer-saving management practice for wheat-maize cropping system in the North China Plain: Based on a 4-year field study

Developing an alternative water-fertilizer-saving management practice for winter wheat-summer maize double cropping system in the North China Plain (NCP) is urgent to address severe water scarcity and adverse environmental impacts. A four-year field experiment in split plot design was conducted to evaluate the effects of supplemental drip irrigation on grain yield, water use efficiency (WUE), nitrogen use efficiency (NUE), nitrogen (N) loss and economic benefits, keeping three supplemental drip irrigation times (DI0, no irrigation after emergence; DI3, irrigation once at wheat jointing, once at maize seedling and once at maize jointing; DI5, irrigation once at wheat jointing, once at wheat anthesis, once at maize seedling, once at maize jointing and once at maize tasseling) in the main plots and three N fertilizer rates (N0, no N fertilizer; N60%, 60% of the local recommended N fertilizer rate, 272 kg N ha−1 yr−1; N100%, 100% of the local recommended N fertilizer rate, 453 kg N ha−1 yr−1) in the sub plots. The traditional surface irrigation regime was also conducted as control (CK) under local recommended N fertilizer at 453 kg N ha−1 yr−1. The results showed that DI5N60% achieved the highest WUE in wheat (1.93 kg m−3) and maize (3.00 kg m−3) on average, which was 3.0% and 25.3% higher compared to CK, respectively. The highest partial factor productivity from applied N (PEPN) in wheat and maize were also observed in DI5N60% (56.8 kg kg−1 and 56.3 kg kg−1, respectively) on average, which was 54.0% and 74.0% higher compared to CK, respectively. For winter wheat-summer maize double cropping system, DI5N60% can generally achieve similar crop yield and net income but reduce irrigation and N fertilizer use and N loss compared to CK. Therefore, DI5N60% was considered as an alternative water-fertilizer-saving management practice for winter wheat-summer maize double cropping system in the NCP. Moreover, the optimized combination of irrigation amount and N fertilizer rate corresponding simultaneously to higher crop yield, WUE and net income were determined by using the response surface methodology based on binary quadratic regression analysis, and the optimal irrigation amount were 165 mm and 90 mm, optimal N rates were 186 kg N ha−1 and 185 kg N ha−1 for winter wheat and summer maize, respectively.