| It is very important for us to quantitatively evaluate the environmental risk of non-point source pollution caused by fertilizers application, to accurately identify the high-risk areas of non-point source pollution, and to formulate some effective measures. Based on the statistical data of fertilizers application in Xi'an from 1991 to 2018, the temporal evolution and spatial differentiation characteristics of chemical fertilizer application in the whole city were comprehensively analyzed, and the environmental risk degree of non-point source pollution caused by fertilizers application was evaluated. The results showed that after the rapid growth from 1991 to 2014, the application rate of chemical fertilizer in Xi'an decreased in four consecutive years from 2015 to 2018; The proportion of nitrogen (N), phosphorus (P) and potassium (K) fertilizers application structure was gradually adjusted from 1∶0.24∶0.13 in 1991 to 1∶0.34∶0.37 in 2018; From 1991 to 2018, fertilizer intensity increased significantly,and the fertilizer intensity in 2018 was 3.60 times than in 1991; The overall increasing trend of environmental risk of chemical fertilizer application was obvious, and the risk of total fertilizer increased from " safe" in 1991 to "severe risk" in 2018. There were obvious spatial differences in environmental risk of non-point source pollution caused by fertilizers application in Xi'an. In conclusion，Chang'an District is a "low risk" area, Lintong District, Gaoling District and Huyi District are "medium risk" areas, Baqiao District, Yanliang District and Lantian County are "serious risk" areas, and Weiyang District and Zhouzhi County are "serious risk" areas. For ensuring crop yield, Xi'an should formulate effective control measures in the aspects of fertilization technology, research, related policies and regulations. |
