Study On Carrying Potential Of Livestock And Poultry Based On Balance Of Nitrogen And Phosphorus In Farmland In Chengdu Plain

The problem of agricultural soil nutrient surplus caused by the irrational use of large-scale livestock and poultry manure is a major component of agricultural non-point source pollution,especially in soils with high density of livestock and poultry farming,high planting density and continuous tillage.In order to ensure crop yields,the problem of soil nutrient surplus caused by excessive fertilization is particularly prominent.This paper takes the agricultural development of Deyang City as the research object,analyzes the current planting scale and breeding scale by analyzing the balance between the nutrient and actual fertilizer applied to the aquaculture and planting industries in the study area.The surplus of nitrogen and phosphorus in the soil of agricultural land in the region,the consistency between the measured value and the estimated values of the soil fertility and the total nitrogen content of groundwater;the study of the balance of farming and township in each township,and then the cultivation according to different townships different potentials,reasonable planning of the type and quantity of farming in each township,in order to achieve a balanced farming.The result show that:(1)Calculate the amount of livestock manure production,the amount of pollutants produced,and the nitrogen and phosphorus load in the study area in the past three years through the sewage coefficient method and the pig equivalent nuclear algorithm.The results show that nitrogen and phosphorus load in livestock manure in the study area are increasing year by year,with the average nitrogen load increasing from 80.5 kg/hm~2 in 2015 to 137 kg/hm~2 in 2017.The phosphorus load increased from 20.9 kg/hm~2 in 2015 to 36 kg/hm~2 in 2017.Combined with the spatial distribution of ArcGIS,the increase of nitrogen and phosphorus load in each township has a spatial distribution consistency.Although the increase is not synchronized,it is closely related to the number of livestock and poultry farming and the area of agricultural land in each township.(2)Through the nutrient balance theory,the input and output of nutrients in the agricultural land of the unit are calculated separately,and then the surplus of nutrients in the agricultural land of the unit is calculated.The input amount in this study is the nutrient content of livestock manure,the nutrient content of soil accumulation and the amount of fertilizer applied to crop growth,and the output is the consumption of crop growth.The maximum nitrogen and phosphorus surplus in Donghu Town is 679.94kg/hm~2 and 258.17 kg/hm~2 respectively;the minimum nitrogen and phosphorus surplus in Xiaogan Town is 22.9 kg/hm~2 and 15.08 kg/hm~2 respectively.(3)This paper measures the total nitrogen content in groundwater by continuously monitoring and sampling the groundwater in the study area,and uses it to verify the applicability of the nutrient balance model.So as to further the potential of livestock and poultry breeding in each township.By comparing the theoretical carrying capacity and actual carrying capacity of livestock and poultry breeding in the study area,it indicates that there are livestock and poultry breeding potentials in most townships in the study area,but the quantity of livestock and poultry farming should be limited in Donghu Town,Hexin Town,Xinzhong Town and Tianyuan Town.