| “Tow aquatics,double green"refers to the green concept of making full use of the paddy fields and water resources in the plain lake area,carrying out rice-fishery integrated systems,and making the coordinated development of"green rice"and"green aquatic products".Rice-crayfish integrated system is a representative of the"Tow aquatics,double green".It is an ecological agricultural model that makes full use of water,soil,light,biological and other resources to culture crayfish.It has been promoted for 1.3 million hm~2 in the middle of China.However,the ecological theory of rice-crayfish system is not well-prepared today,and the problems of unreasonable resource utilization and non-standard technology in production hinder the sustainable development of rice-crayfish system.The balance of physical-chemical factors and nutrients in water can reflect the material circulation and energy flow of agroecosystem,and is an important index to guide actual production.In this study,rice-crayfish integrated system under“Two aquatics,double green”,crayfish monoculture and rice monoculture were selected as the objects to monitor the changes of physical-chemical factors of water in different modes,analyze the impact of different modes on water environment,and compare the budgets of nutrients(N,P and C),also economic benefits of different modes.The purpose is to explore the advantages of nutrient circulation and resource utilization of“Tow aquatics and double green”rice-crayfish integrated system,optimize the water quality management and nutrient input of rice-crayfish integrated system,improve the resource utilization efficiency and economic benefits of rice-crayfish integrated system and provide theoretical basis and practical suggestions for the sustainable development of rice-crayfish integrated system.The main results and conclusions are as follows:1.From March 2021 to October 2021,this study dynamically monitored the water temperature,p H,dissolved oxygen,total nitrogen,total phosphorus,ammonia nitrogen,nitrite,nitrate,soluble phosphorus and total organic carbon of rice-crayfish system,crayfish monoculture and rice monoculture.The results showed that there was no significant difference in water quality between rice-crayfish system and crayfish monoculture;Fertilization has a great impact on TN,tan and TP of rice-crayfish system,but the change range is relatively small compared with rice monoculture,and the water environment is more stable;From July to August,the average TN and TP of crayfish intensive culture mode were significantly higher than that of input water,and there was a risk of nutrient loss.In conclusion,during the rice planting period,the water body of the rice-crayfish system is more stable,and the rice growth reduces the nutrient concentration of the field water,which is more suitable for the green and healthy breeding of crayfish.The rice-crayfish system has no significant effect on the water quality of paddy field,but attention should be paid to the management of field surface water after fertilization.2.In this study we recorded the feed and fertilizer input,calculated adult crayfish and rice yield,found that under the concept of"Tow aquatics,double green",compared with the crayfish monoculture,the rice-crayfish system reduces the feed dosage by46.8%,significantly reduces the feed coefficient rate(CM:1.16,RCI:0.91),and improves the feed utilization rate.Compared with rice monoculture,rice-crayfish system significantly increased the number of effective panicles and theoretical yield of rice,increased the actual yield by 12.7%,and promoted the C concentration and absorption of P and C by rice grains(P<0.05).To sum up,compared with crayfish monoculture,rice-crayfish system improves feed utilization efficiency and can effectively reduce feed input;Compared with rice monoculture,it increases rice yield and promotes the absorption and utilization of nutrients by rice.In conclusion,compared with the crayfish monoculture,the rice-crayfish system promotes the utilization of feed by crayfish,improves the yield of rice in paddy field,promotes the absorption of nutrients by rice,and helps to improve the efficiency of material circulation and energy flow.3.In this study,the nutrient input and output of the three models were quantified,and the nutrient budgets of different models was calculated through“farm-gate”method.The results showed that the surplus of N and P in crayfish-monoculture were 117.7%and 1250%higher than that in rice-crayfish system,respectively,and a large amount of nutrients were wasted and deposited in the environment;Compared with the crayfish monoculture,the rice-crayfish has higher nutrient use efficiency(RCI-N:62%,CM-N:39.8%;RCI-P:63.7%,CM-P:27.0%);Compared with the rice monoculture,the rice-crayfish increased the N surplus of 20.3 kg/hm~2 and the P surplus of 8.7 kg/hm~2,which was conducive to the sustainable production of rice field;Rice-crayfish belongs to carbon sink,which improves the carbon sequestration of rice grain compared with rice monoculture;The crayfish monoculture belongs to carbon source,and the use efficiency of C(11.7%)is lower than RCI(203.3%)and RM(518.2%).In conclusion,the rice-crayfish system reduces nutrient input,improves the use efficiency of nutrients in the system,increases the surplus of N and P in rice fields,and improves the carbon fixation capacity.It is an efficient,low-carbon and sustainable production planting and breeding model.4.This study calculated the economic expenditure and income of rice-crayfish system,crayfish monoculture and rice monoculture in the process of production:the results showed that the profits of rice-crayfish,crayfish monoculture and rice monoculture were 31868￥/hm~2,35918￥/hm~2 and 9660￥/hm~2respectively.The rice-crayfish system has significantly improved the economic benefits of paddy fields.Under the condition of reducing the cost input,the profit margin of rice-crayfish is similar to that of crayfish monoculture,and the profit difference is small,indicating that planting rice will not affect the income of crayfish breeding.In the rice-crayfish system,the income of rice and adult crayfish accounts for 41.5%and 58.5%respectively.We can further improve the added value of rice by building a high-quality rice brand,so as to achieve the coordinated development of rice and aquatic products.To sum up,rice-crayfish reduces the cost of crayfish culture and rice planting,can significantly improve the economic income of rice field,and has good economic benefits. |
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