Research On Agricultural Nitrogen Balance And Its Impact On Water Environment In The Yangtze River Economic Belt

The Yangtze River economic belt is a major national strategic development area,plays an important role in China’s agricultural development.However,with the development of agricultural economy,in order to ensure the increase of yield,it depends too much on chemical nitrogen fertilizer.Due to the backward fertilization technology,low nitrogen utilization rate and backward nitrogen management,the proportion of agricultural nitrogen loss increases,which leads to a series of problems of agricultural nitrogen pollution and water resource pollution.Therefore,carrying out the evaluation of agricultural nitrogen balance and agricultural water pollution in the Yangtze River economic belt,and using the methods of "nitrogen balance model",correlation analysis and Moran index to explore the temporal and spatial evolution law and spatial agglomeration characteristics of farmland nitrogen balance in the Yangtze River economic belt and its impact on Agricultural water environment is conducive to analyzing the potential causes of agricultural pollution and ensuring the supply of safe agricultural products in the Yangtze River economic belt,Provide guarantee for emission reduction measures and ecological sustainable development,promote the macro management of agricultural nitrogen pollution and water environment pollution by relevant environmental protection departments,and provide data support and scientific basis for the formulation of agricultural environmental policies.The main conclusions are as follows:(1)From 1990 to 2018,the farmland nitrogen in the Yangtze River economic belt was in an unbalanced state,the total nitrogen input increased year by year,the growth trend of nitrogen output was not obvious,and the nitrogen surplus showed an increasing trend year by year;The growth trend of total nitrogen surplus is highly consistent with the change trend of total nitrogen input.The main source of nitrogen input is chemical fertilizer,followed by human and livestock excreted nitrogen input.The overall nitrogen use efficiency of the Yangtze River economic belt is not high,and the nitrogen use efficiency is less than 50%.(2)There are regional differences in the growth rate of agricultural nitrogen surplus in the Yangtze River economic belt.The growth rate of nitrogen surplus in the central region decreases,and the change rate of nitrogen surplus in the eastern and western regions shows the characteristics of "first increasing and then decreasing";Yunnan Province and Jiangsu Province have the most serious nitrogen surplus,which has the greatest impact on the total nitrogen surplus of the Yangtze River economic belt;Nitrogen surplus showed a large spatial autocorrelation,showing a form of spatial agglomeration,and the degree of agglomeration decreased;On the whole,the Yangtze River economic belt is in the state of "high nitrogen surplus intensity".The nitrogen surplus intensity in the western region is higher than that in the central and eastern regions,and the nitrogen surplus intensity shows a strengthening trend.(3)Nitrogen surplus shows a high correlation with agricultural gray water footprint,while nitrogen surplus shows a negative correlation with gray water footprint of planting industry and a high positive correlation with water pollution brought by animal husbandry;The higher nitrogen use efficiency,the lower agricultural gray water footprint and the lower agricultural nitrogen pollution to water;From 1990 to 2018,the agricultural grey water footprint of the Yangtze River Economic Belt experienced two stages of change,showing a trend of "increase decrease increase decrease";In terms of spatial distribution,the regions with the largest contribution to agricultural grey water footprint are Sichuan Province,Hunan Province,Hubei Province and Jiangsu Province.