Spatial characteristics of phosphorus flow in crop-livestock production systems in Shanxi, China

A quantitative understanding of phosphorus (P) flow, loss and use efficiency is critical for improving the productivity and sustainability of agriculture while minimizing environment impact. However, most studies have focused primarily on either crop systems or livestock systems. Hence the analysis of P flow in integrated crop-livestock production systems has been largely lacking and the spatial characteristics of P flow has not been entirely known. Here, we quantified P flow, loss and use efficiency (PUE) in crop-livestock production systems in Shanxi Province, China, using the NUFER (nutrient flows in food chain, environment and resources use) simulation model and ArcGIS. We collected the data from a statistical database in 2011, consisting of 11 municipalities in Shanxi Province, to explore the spatial characteristics of P flow in the crop-livestock systems and propose scientific regional nutrient management. Our results showed large variations in P input and loss under crop/livestock systems in different cities of Shanxi Province. P input under crop production system was within 22.5–83.0 kg.hm^-2 and P loss under crop-livestock system was within 2.7–8.8 kg.hm^-2. Both P input and loss were significantly higher in the southeast than in the northwest regions. For crop systems, surplus P was within 9.4–48.4 kg.hm^-2, which largely varied with region. PUE under crop systems (PUEc) in Shanxi was 45.6%, significantly higher than the national average (37.0%). Then PUE under livestock system (PUEa) was low (7.6%), mainly because of the large amount of draught cattle in livestock systems (581×10³ heads). As a result, PUE under crop-livestock systems (PUEc+a) was relatively low (30.3%). This was mainly due to the separation between crop and livestock systems and the resulting low recycling rate of P (< 60%) from animal excreta and crop residues to croplands. Spatially, the southeast region had the largest potential risks of environmental pollution. Hence there was an urgent need to improve P management in crop-livestock production systems in the province. Large amounts of animal manure were not recycled and reused in Jincheng and Jinzhong, which could be used as nutrient input in croplands. In conclusion, PUE in crop-livestock systems in Shanxi Province was relatively low. This was in part due to the separation and de-coupling of crop and livestock systems within regions. It also related to the specialization of crop and livestock production in various regions, which resulted in large spatial variations. P loss under crop production systems was large in the south than in the north. There was also a large room for animal manure recycling. Hence significant improvements in P management were realizable via optimizing P flow between crop and livestock systems, and also via improving P flow among regions. P management needed optimization in crop-livestock production systems and among regions to significantly improve PUE at large scale and production system scale. This significantly reduced the risk of environmental pollution and ensured sustainable development.