Winter hairy vetch-spring maize rotation can improve nitrogen-utilization efficiency on the North China Plain

Understanding the contributions of winter cover crops (CCs) to nitrogen (N) uptake of succeeding spring maize will help achieve more efficient soil N use. A single-factor field experiment was conducted to quantify residual N effects of contrasting cover crop 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. Compared with the winter fallow, HV, OV and HO treatments decreased N fertilizer input by 30%, 9%, and 28%, 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%. The fallow treatment had the highest N surplus (167 kg N ha−1), and HV, OV and HO treatments significantly reduced them to 78, 127 and 102 kg N ha−1, respectively. Introducing hairy vetch or hairy vetch/ February orchid mixture in the sole spring maize cropping system will deliver significant improvements in nitrogen use efficiency on the North China Plain.