摘要：Growing evidence indicates that climate change has significant impacts on crop production. However, the spatial variability and extent of the impacts on N concentrations in crops have yet to be explicitly described, although N concentration is a critical element of both the nutritional value of food and the planning of appropriate field management procedures. We present multi‐tiered evidence showing that warming increases N concentration in rice and reduces internal N use efficiency (iNUE), thereby increasing N uptake in crops and encouraging greater N fertilizer use. First, we mapped current N concentrations and iNUE for single‐season irrigation paddy rice production in 975 counties across China using data from 1,637 on‐farm experiments and Random Forest regression modeling. Current N concentrations in rice grain and straw have increased with increasing temperatures from northern to southern China. The global meta‐analysis provided further direct evidence that warming increases N concentration in rice. Future warming projections indicate that N concentrations in grain will increase by 5%–9.6% and that iNUE will decrease by 9%–14% under scenarios RCP4.5 and RCP 8.5 although higher CO2 and other factors may also affect N concentrations. Overall, these data demonstrate that N uptake by rice will need to increase by 7.8%–13.6% to maintain current grain yields across China based on warming alone. Our findings indicate that warming associated with increase in N concentration and reduction in iNUE would be expected to encourage N application, raise the urgency of measures to prevent excessive N application, and stronger counteracting measures need to be enacted.
