Incorporating winter mixed cover crops into spring maize improves nitrogen-utilization efficiency and environmental benefits on the North China Plain

Background and aims Understanding the contributions of winter cover crops (CCs) to nitrogen (N) uptake of succeeding spring maize will help achieve more efficient soil N use. Methods A single-factor field experiment was conducted to quantify residual N effects of contrasting CC tops on spring maize N utilization and environmental benefits. 15N-labeled fertilizers were applied at the time of CC establishment in a microplot experiment to determine the contribution of aboveground residue N of winter cover crops (hairy vetch (HV), February orchid (OV), hairy vetch/ February orchid mixture (HO)) to the following spring maize. Results Compared with the winter fallow, HV, OV and HO treatments significantly increased the partial factor productivity of N fertilizer by 43%, 16%, and 23%, respectively. The spring maize N derived from the residues was 27 (HV), 6 (OV) and 22 (HO) kg ha−1 and the total contribution to the N uptake of spring maize from the aboveground residues was 2.2~10.3%. Net N surplus was defined as total N input minus N output, and the value of OV (112 kg N ha−1) was significantly lower than that of OV (182 kg N ha−1) and HO (197 kg N ha−1). The HO was the most environmental-friendly cropping system with the lowest carbon footprint, which decreased greenhouse gas (GHG) emissions by 30%. Conclusions The introduction of winter mixed CCs in the rotation system of three crops across two years on the North China Plain had a higher N-use efficiency, maintained yields with higher net profits, and lowered emissions.