Increasing food and feed self-sufficiency and avoiding manure N surplus in eastern regions of China through a spatial crop-livestock optimisation model

As the largest emerging economy globally, China is facing crop-livestock disconnection, which causes unnecessary synthetic fertiliser use, local food and feed unsatisfied demand, and manure nitrogen (N) surplus. We investigated how crop-livestock regional integration combined with inter-regional transportation of food, feed, and manure, can contribute to food self-sufficiency of easter China (whole and regional level) while avoiding manure N excess. We also investigated how this could increase the local soybean production without harming the self-sufficiency of other food commodities. We proposed an optimisation model of integrated crop-livestock production in eastern China, including the production of food, feed, and livestock manure N in each region and the demand for food (according to healthy diet recommendations), feed and manure N. We optimised the supplier cost-benefit balance considering food and feed production, domestic transportation, and foreign trade, taking food and feed demand satisfaction and manure N surplus avoidance as constraints. This optimisation exercise was performed under different scenarios: optimisation without soybean subsidies (scenario O), optimisation with increasing soybean subsidies (scenario OS+). The two scenarios were compared with the baseline scenario B (non-optimised without soybean subsidies) using balance indices (BI, the gap between production and demand divided by demand) of food, feed, and manure N and transportation indices. Results showed that, for the whole of eastern China, BI were positive for cereals (1.523), vegetables (2.789), meat (0.002), eggs (0.002), milk (0.102), and maize (0.244), and negative for manure N (−0.016) in scenario O. This indicated that most of the food and feed items except soybean were self-sufficient and manure N surplus was avoided after optimisation. Some regions lowered their self-sufficiency for some commodities. As soybean subsidies increased from 0 Yuan ‧ ton-‍1 to 6000 Yuan ‧ ton−1, the BI of soybeans increased by 66.37%. Our results suggested that crop and livestock can be integrated in China for an improved level of food self-sufficiency and manure N surplus avoidance. However, regional self-sufficiency could not be achieved in all regions for all items, and transportation is necessary. In particular, three strategies seem relevant for policy-making: (i) decreasing livestock quantity, for strengthening feed self-sufficiency and avoiding manure N surplus; (ii) increasing soybean production through subsidies; (iii) reducing regional-level self-sufficiency and increasing the transportation for meat and eggs, which would avoid manure N surplus in densely populated regions, while decreasing the maize transportation.