Phosphorus flow characteristics and its influencing factors on the crop-livestock system of Jiangsu Province

To provide a theoretical basis for the sustainable development of the crop-livestock production system in Jiangsu Province, this study explored phosphorus flow and its influencing factors. Literatures research, data analyses, combined with the NUFER model (NUtrient flow in the Food chain, Environment, and the Resource use) were used to quantitatively analyze phosphorus flow and its influencing factors in the crop-livestock production system of Jiangsu Province from 1998 to 2018. The total phosphorus inputs of the crop-livestock production system from 1998 to 2018 decreased from 423.19 Gg to 382.86 Gg, and the main reduced inputs were chemical fertilizer and exogenous feed. The fertilizer input per unit cultivated area decreased from 78.78 kg·hm^-2 to 67.27 kg·hm^-2, and the supply of exogenous feed phosphorus decreased from 58.07 Gg to 46.54 Gg. The total output of phosphorus increased from 194.24 Gg to 255.06 Gg. The dominant output items were main crop products and animal by-products; the main crop products increased from 77.53 Gg to 131.86 Gg. The phosphorus utilization rate of the agricultural production subsystem increased from 31.82% to 52.46%, and the livestock production subsystem remained between 27.67% and 35.31%. The results showed that the phosphorus utilization rate of the crop-livestock production system was consistent with that of the agricultural production subsystem, which increased from 16.55% to 32.24%; phosphorus loss per unit of crop-livestock products decreased from 0.26 kg(P)·kg^-1 to 0.12 kg(P)·kg^-1. From 1998 to 2018, crop-livestock husbandry in Jiangsu Province developed rapidly, the total phosphorus input decreased annually, the output of crop-livestock products increased annually, and the total phosphorus loss to the environment (runoff, erosion, leaching, and manure loss) decreased annually. Reductions in chemical fertilizer input, fertilization based on soil testing formula, and planting and breeding structure adjustments led to a slightly higher utilization rate of phosphorus in the crop-livestock production system compared to the national level. Thus, nutrient management had achieved preliminary results, but there was still some room for improvement. To promote the sustainable development of crop-livestock husbandry in Jiangsu Province, it is necessary to further control phosphate fertilizer input, increase the input of organic fertilizer and local feed, improve the comprehensive utilization rate of straw and livestock manure, adjust the planting structure and breeding layout, develop planting, and restrict breeding.