Study On The Cascade Flow Efficiency And Environmental Load Of Active Nitrogen At The Township Scale In Xiaoxing'anling

The research on active nitrogen cascade flow at town scale provides a theoretical basis for the targeted improvement of the utilization rate of active nitrogen and the reduction of the negative impact of reactive nitrogen on the ecological environment.China has a vast territory and large regional differences.Dailing District is located in the south of Xiaoxing'anling in the northeastern part of China.It has less industrial activities.The active nitrogen cascade flow in food production-consumption process is less affected by other human activities.Based on the material flow analysis method,this study studied the active nitrogen cascade flow efficiency and environmental load of the crop production system,livestock and poultry breeding system and household consumption system in the Dailing District from 2007 to 2015.The active nitrogen flow characteristics in the Dailing District were calculated from the three aspects of active nitrogen cascade flow flux,food nitrogen supply and demand balance and food nitrogen cost The active nitrogen flow was analyzed from the aspects of nitrogen utilization rate,nitrogen recycling rate and nitrogen cascade utilization.Reactive nitrogen environmental loss and reactive nitrogen cascade flow environment ratio;using analytic hierarchy process to evaluate reactive nitrogen use efficiency,driving factor analysis and parameter sensitivity for reactive nitrogen cascade flow efficiency sensitivity analysis,and using time series method to predict the environmental load of active nitrogen cascade flow in the future Dailing District.The main conclusions are as follows:(1)The flow of active nitrogen in crop production systems and livestock and poultry farming systems showed an upward trend from 2007 to 2015,and the flux of reactive nitrogen in household consumption systems decreased slightly.The consumption of plant food is 80±2 tN/a,and the consumption of animal food is 87±1 tN/a.Nitrogen in plant foods is at a loss,and animal food nitrogen has changed from a loss state to a surplus state after 2010.The nitrogen deficiency of plant foods is strongly influenced by the application rate of compound fertilizers.The nitrogen deficiency of animal foods is strongly influenced by the total meat production.The nitrogen cost of food production in the Dailing District is relatively high,and the nitrogen loss from the production unit quality product into the environment is about 6.03 kg.(2)The nitrogen utilization rate of the crop production system in Dailing District ranges from 52.6%to 70.8%,the nitrogen utilization rate of the livestock and poultry breeding system is stable at around 19%,and the household consumption nitrogen utilization rate is 2%.The nitrogen recycling rates of crop production,livestock and poultry farming and household consumption systems in the belt area were 55.4%,15.6%and 11.4%,respectively.The annual variation in the utilization of reactive nitrogen cascades is small.(3)From 2007 to 2015,the environmental nitrogen load in the belt area increased year by year,increasing by 847 t from 406 t,and the nitrogen load entering the water body and the atmosphere accounted for 56.5%and 43.5%of the environmental nitrogen load,respectively.Livestock and poultry manure produced in livestock and poultry farming is the most important source of nitrogen load.(4)The value of nitrogen utilization rate evaluation index of household consumption system is high,and the importance of environmental loss rate brought by livestock and poultry farming and household consumption increases year by year.The driving factors for the utilization of reactive nitrogen cascades are mainly productivity factors.There are no extremely sensitive parameters with sensitivity level IV in the model;sensitive parameters with sensitivity level ? are mainly nitrogen content in livestock manure,soybean yield,nitrogen fertilizer application rate and grain nitrogen content;sensitivity level is ?,The general sensitive parameters are mainly population indicators and fertilizer runoff loss rate;most of the parameters are insensitive parameters with sensitivity level I.It is predicted that the average annual intake of active nitrogen into the atmosphere,water bodies and soils will reach 625 tN,780 tN and 145 tN in 2025.