Study On The Carrying Capacity Of Livestock And Poultry Breeding In Liaoning Province Based On Farmland Nitrogen And Phosphorus Nutrient Balance

As a big province of livestock and poultry breeding,Liaoning Province produces more and more waste,and its threat to the ecological environment is becoming more and more remarkable.In order to reduce the threat of livestock and poultry breeding industry to the environment in Liaoning Province,this paper,based on the actual situation of Liaoning Province,conducts annual monitoring of feces and its main pollutants produced by livestock and poultry breeding in Liaoning Province,estimates the single daily pollution coefficient of feces and its pollutants of each livestock and poultry at different growth stages in Liaoning Province,and further estimates the nutrient load of feces of livestock and poultry in Liaoning Province in 2019.On this basis,combined with the existing scale of planting and breeding industry in Liaoning Province,and based on the balance of nitrogen and phosphorus nutrients,this paper analyzes whether the nitrogen and phosphorus nutrient components in cultivated soil in Liaoning Province pose a threat to the environment.Then quantitative comparison of the breeding balance in the study area,so as to optimize the structure and scale of livestock and poultry breeding in Liaoning Province according to the calculated environmental carrying capacity and breeding potential of livestock and poultry in different regions,hoping to achieve breeding balance and provide reference for promoting the sustainable development of livestock and poultry breeding in Liaoning Province.The main results are as follows:（1）The total amount of manure production in Liaoning Province in 2019 was 46.54 million tons,and the amount of manure production accounted for 36.18%of the total production.In general,the total amount of livestock and poultry manure was in the order of pig,cattle,sheep,poultry,which were 19344thousand tons,19306 thousand tons,3529.5 thousand tons and 4362 thousand tons,respectively.The livestock and poultry manure pollution in Liaoning Province mainly comes from pig urine and cow urine,accounting for 28.70%and 28.65%of the total production respectively,and the production of livestock and poultry manure in different regions is quite different.The total production of COD,TN,TP and ammonia nitrogen in livestock and poultry manure were 1817.4 thousand tons,5689 thousand tons,84.9thousand tons and 266.6 thousand tons,respectively,accounting for 66.38%,20.78%,3.10%and 9.74%of the total pollutant production.（2）In 2019,the average equivalent load of pig manure per unit area of cultivated land in Liaoning Province was 11.04 t·hm^-2,and the total nitrogen and phosphorus loads of livestock and poultry breeding per unit cultivated land were 134.91 kg·hm^-2and 20.13 kg·hm^-2,respectively.（3）The environmental carrying capacity of livestock and poultry breeding in some urban areas of Liaoning Province has been overloaded to a certain extent.The total number of livestock and poultry breeding in Liaoning Province in 2019 was 10.82 million pigs equivalent,and the actual carrying capacity of livestock and poultry breeding in unit farmland was 25.65.The theoretical maximum breeding amount was 33.53 pigs equivalent and 90.62 pigs equivalent,respectively,based on the nutrient balance of nitrogen and phosphorus.The nitrogen and phosphorus in Liaoning Province did not exceed the environmental carrying capacity.（4）In 2019,the environmental risk levels and breeding potential of 14 cities in Liaoning Province were different.Based on phosphorus balance calculation,all cities were not overloaded.With nitrogen balance calculation,Dalian and Benxi belong to high-risk areas,livestock and poultry breeding has been seriously overloaded,should be timely control,reduce feeding.Dandong and Hulu Dao have high risks and obvious overloads;Chaoyang city environment has belonged to the middle risk level,livestock and poultry breeding slightly overload;livestock and poultry breeding in these areas were not overloaded.Liaoyang City and Panji City had no risk to the environment,and also had great breeding potential.Half of the remaining cities were low-risk areas.Livestock and poultry breeding still had certain potential.The load of livestock and poultry manure is similar to the distribution density of livestock and poultry.Each city should make full use of livestock and poultry manure resources according to the actual situation.The areas with higher risk levels should control the total amount of livestock and poultry breeding,while control and prevention of pollution.