Rebuilding the linkage between livestock and cropland to mitigate agricultural pollution in China

An increasing disconnect between livestock production and croplands has been observed in many world regions, including China, which has the world's largest livestock production sector. Here we propose a cropland-based livestock production system to rebuild the linkage between livestock and cropland from both agriculture production and human consumption perspectives for China. In 2015, the total excretion nitrogen (N) generated by livestock production operations was 14.6 Tg N, and it would grow to 15.0 Tg in 2030 by extrapolating current trends. The optimal demand of total N by crops in China was estimated to be 23.0 Tg N in 2030, suggesting that Chinese livestock would be within the carrying capacity of cropland on national level, but substantial variations were found across provinces. The carrying capacity of cropland with regard to N input from manure would be exceeded in 74% provinces, under the assumption that manure providing half of the N supply for crops. Furthermore, from the perspective of domestic feed supply for livestock production, about 51% of feed N needs to be imported. If following the optimized dietary structure of China to manage livestock sector, livestock production could be reduced by 37% in excretion nitrogen, which would not only benefit the food security and human health, but also mitigate the agricultural pollution. Accordingly, policy regulations on reduction and spatially reallocation of livestock production on a regional scale could substantially reduce manure N loss from 10.5 Tg yr(-1) to 1-1.2 Tg yr(-1) under different recoupled scenarios.