A Comparative Research On The Environmental Efficiencies Of Crawfish Production Systems

As an important source of human animal protein,aquaculture has developed rapidly in recent years.But it also puts pressure on the environment to pollute with nitrogen.Identifying the potential for improvement of nitrogen pollution in current aquaculture processes is of great significance for formulating relevant environmental standards and policies.Procambarus clarkii is an important and economical aquaculture product and has been growing rapidly in recent years.It is of great significance to analyze the potential and mechanism of nitrogen pollution improvement in the cultivation of Procambarus clarkii.In this paper,the improvement potential of nitrogen pollution load in rice-crayfish culture and pond culture was evaluated by using the concept of environmental efficiency.The main research contents of this paper include: firstly the nitrogen input and output in the models of rice-crayfish culture and pond culture are identified,and the nitrogen pollution load characteristics are calculated and analyzed;secondly based on the data envelopment method,the environmental efficiency evaluation model are constructed,and the improvement potential of nitrogen pollution load in different farming modes are analyzed;thirdly the nitrogen pollution load and improvement potential of the two cultures are compared and analyzed.The research results of this paper are as follows:(1)The average environmental efficiency of rice-crayfish farmers is 0.28,the improvement potential of nitrogen pollution load is great,and the difference between farmers is also large.The average nitrogen pollution load of rice-crayfish farmers is 0.12t/ha,the difference between actual nitrogen load and nitrogen redundancy is the theoretical minimum nitrogen pollution load.The nitrogen redundancy of farmers is 0.08t/ha,and the theoretical minimum nitrogen pollution load is 0.02t/ha.(2)The average environmental efficiency of pond farmers is 0.42,the improvement potential of nitrogen pollution load is great,and the difference between farmers is also large.The average nitrogen pollution load of pond farmers is 0.14t/ha,the difference between actual nitrogen load and nitrogen redundancy is the theoretical minimum nitrogen pollution load.The nitrogen redundancy of farmers is 0.07t/ha,and the theoretical minimum nitrogen pollution load is 0.06t/ha.(3)From the total nitrogen pollution load of farmers,the nitrogen pollution loads of rice-crayfish farmers and pond farmers are 0.26 t and 0.15 t respectively,the nitrogen pollution load of rice-crayfish farmers is significantly higher than that of pond farmers.As for the pollution load per unit nitrogen output,the nitrogen pollution loads of ricecrayfish farmers and pond farmers are 1.31 t and 1.88 t respectively,the nitrogen pollution load of rice-crayfish farmers is significantly lower than that of pond farmers.This results show that the nitrogen utilization efficiency of rice-crayfish culture system is higher than that of pond culture system.(4)There is great potential to improve nitrogen pollution load in rice-crayfish culture and pond culture.Technical efficiency loss is the main cause of excessive nitrogen input in two farming systems.The ratio of technical efficiency loss and allocation loss of nitrogen input in rice-crayfish cultivation is 58.30% and 41.70%,respectively.The ratio of technical efficiency loss and allocation loss in pond culture is 74.25% and 25.75%,respectively.It shows that the production process of rice-crayfish system is more complex,and farmers have more preference and dependence on the input of nitrogenous production materials such as bait.