Nitrogen use efficiency in a wheat–corn cropping system from 15 years of manure and fertilizer applications

•Long-term field research proved that manure application with chemical fertilizer improved the nitrogen use efficiency (NUE) of wheat–corn rotation system the most especially in acid soil.•Phosphorus is found to be another important factor to improve NUE up to 40–60% if soil is P deficient.•Between the rotation crops, both grain yield and NUE of wheat were determined more responsive to P fertilization, and that for corn were more responsive to manure application.

Low nitrogen use efficiency (NUE) and adverse environmental impacts caused by N fertilization increasingly threaten the sustainability of agriculture. To develop strategies for efficient nutrient management, we investigated the effects of long-term (1991–2005) various fertilization regimes on yield, NUE and N agronomic efficiency (NAE) in a wheat–corn cropping system at four sites (Changping, Zhengzhou, Yangling, and Qiyang) in China. Treatments included unfertilized control (CK), chemical fertilization only (N, NP, NK, and NPK), manure application (supplying 70% N) with NPK (NPKm) and at 1.5× rate (1.5NPKm), and NPK with corn stover returned (NPKs). The NP and NPK treatments resulted in generally higher yield, NUE and NAE than the N and NK for both wheat and corn demonstrating the importance of P in NUE improvement. The manure treatments resulted in significant increase or no decrease in the overall system NUE in all four sites with the highest mean NUE (49%) from NPKm treatment. In acid soil at Qiyang, only manure treatments resulted in significant increases of NUE and NAE indicating the importance of organic amendment. Wheat was more responsive to P fertilizer and corn was more responsive to manure in NUE improvement. Thus an effective nutrient management strategy is to ensure adequate P supply for the wheat crop and manure application for the corn crop to improve overall NUE for the wheat–corn production system.