Yield benefits from replacing chemical fertilizers with manure under water deficient conditions of the winter wheat – summer maize system in the North China Plain

Abstract

Recycling of livestock manure in agroecosystems has been shown to improve crop yields, increase resource use efficiency, and reduce adverse environmental consequences from intensive crop-livestock systems. However, such effects have not been well explored for the widely planted winter wheat - summer maize double cropping system in the North China Plain, especially under deficit irrigation. A three years split-plot field experiment was established with and without irrigation (at wheat jointing stage) as main plots, and with chemical fertilizer N (Fc), manure N (Fm), and 50 % chemical fertilizer N + 50 % manure N (Fc + m) using the same amount of N input as sub-plots. Irrigation increased wheat yield significantly by 8–19 % in the normal years (2015/2016 and 2016/2017, p < 0.05) and 124 % in the dry year (2017/2018, p < 0.01), which was attributed to the higher spike number and aboveground biomass. Specifically, irrigation increased aboveground biomass before (p < 0.01) and after anthesis (p = 0.08), as well as the fruiting efficiency (grain number per spike weight at anthesis, p < 0.01) and grain number per unit area (p < 0.01), resulting in increased wheat grain yield. However, irrigation in the wheat season reduced maize yield significantly (p < 0.05) by 5 % in the normal years. The maize yield of Fc+m was 7 % higher than that of Fc under irrigated conditions (p < 0.05). Overall, manure application alone had a higher annual yield without irrigation, while mixed fertilization yielded better and earned more (both were 6% higher than Fc) with irrigation. In conclusion, the annual yield of the winter wheat - summer maize system can be maintained or even increased by replacing mineral N with manure, suggesting multiple benefits from integrating manure application into cereal-based cropping systems.