Spatial-temporal evolution and influence factors of China's agricultural non-point source pollution discharge intensity in recent 40 years

The excessive use of agricultural chemicals and the unreasonable use of agricultural wastes are the main problems encountered by China's agriculture department. However, the comprehensive study on the discharge intensity of China's agricultural non-point source pollution (ANPSP) under the long-term series has not been fully explored. On the basis of our previous research, the spatial-temporal characteristics and influence factors of ANPSP discharge intensity in China from 1978 to 2017 were analyzed. The results showed that the discharge intensity from 1978 to 2017 was on a declining curve and roughly underwent four stages, including the free development stage, reform promotion stage, market regulation stage, and policy incentive stage. In this process, the discharge intensity of COD, total nitrogen (TN), and total phosphorus (TP) was, respectively, declined to 1829.1 tons/10(8) yuan, 758.3 tons/10(8) yuan, and 100.1 tons/10(8) yuan. The regional discharge intensity has varied obviously in space as time goes by, showing the characteristics of spatial agglomeration, agglomeration weakening, spatial differentiation, and differentiation aggravation. The influence factor analysis indicated that under the background of implementing the traditional farming mode, increasing farmers' incomes, adjusting the plantation structure, and remaining the stable agricultural product prices, China's ANPSP discharge intensity could be reduced effectively.