Response of crop yield and nitrogen use efficiency for wheat-maize cropping system to future climate change in northern China

Climate change and excessive fertilization will threaten the crops yields and nitrogen utilization in coming decades. The aim of this study is to quantify the response of crop yields and nitrogen use efficiency (NUE) to different fertilization strategies and climate change scenarios in the northern China by 2100 using the process-based SPACSYS model. The model was calibrated and validated with the data from four long-term experiments with winter wheat (Triticum Aestiviurn L.) and summer maize (Zea mays L.) rotation in the northern China. Five fertilizer treatments based on the long-term experiments were chosen: non-fertilizer (CK), a combination of mineral nitrogen, phosphorus and potassium (NPK), NPK plus manure (NPKM), a high application rate of NPKM (hNPKM) and NPK plus maize straw (NPKS). The model simulations and projections were performed under four different climate change scenarios including baseline, RCP2.6, RCP4.5 and RCP8.5. Validation demonstrated that SPACSYS can adequately simulate crop yields, N uptake and annual NUE for the wheat-maize rotation. Without considering the impact of cultivar change, maize yield would increase by an average of 8.5% and wheat yield would decrease by 3.8%, and the annual NUE would decrease by an average of 15% for all fertilization treatments under RCP climate scenarios compared with the baseline. This might be the interactive effects among elevated CO2 concentration, more concentrated and intensive rainfall events, and warming temperature. For each climate scenario, manure amendment could alleviate the negative influences of future climate change on crop growth and nitrogen utilization, given that manure applied treatments had higher soil organic matter and persistent supply of nutrients, which resulted in a more stable crop yield and N removal by wheat and maize than other treatments. In addition, the highest and most stable annual NUE (38.70-52.78%), crop yields and N removal were found in hNPKM treatment until 2100. The results could provide a reference for nitrogen fertilization in study regions to improve crop yield and nitrogen use efficiency and minimize environmental risks in the future.