Impact Assessment of Spatial Mismatch Between Grain Production and Consumption on Non-Point Source Pollution and Carbon Emissions from Grain Production in China

The spatial mismatch between grain production and consumption (SMGPC) significantly affects the non-point source pollution and carbon emissions from grain production (NPCE). Based on provincial panel data in China from 2000 to 2023, this study explored the direct impact and transmission mechanism of the SMGPC on the NPCE using fixed-effect and mediating-effect models. The results showed that China’s SMGPC intensified significantly during 2000–2023. The average SMGPC degree increased with fluctuations, with positive mismatch strengthening in the northern region and negative mismatch deepening in the southern region. All four NPCE indicators—non-point source pollution per unit sown area (NPA), carbon emissions per unit sown area (CEA), non-point source pollution per unit yield (NPY), and carbon emissions per unit yield (CEY)—peaked in 2016 and declined thereafter. The NPA and CEA showed net increases, whereas the NPY and CEY exhibited net decreases, presenting a similar spatial pattern of “high in the eastern region, low in the central and western regions”. The SMGPC degree drove NPCE indicators with obvious heterogeneity: it increased all NPCE indicators in the negative mismatch region but increased the NPA and CEA while reducing the NPY and CEY in the positive mismatch region. Moreover, cultivated land management scale and chemical fertilizer application intensity significantly mediated the relationship between the SMGPC and the NPCE. The findings offer guidance for optimizing grain production layout and promoting a green agricultural transformation.