| How to effectively use the limited soil and water resources,and further to reduce the negative impact on the environment in agricultural production,which is a major challenge in the global agricultural countries.Rice-crawfish system are used to breed crawfish in paddy fields,it can make full use of the light,heat,water and biological resources,the combination of planting rice and farming crawfish in the same paddy fields has the double benefits of reducing farmland emission and increasing the income to farmers,the social,economic and ecological benefits are remarkable,and the application prospect is broad.In this experiment,the effects of feeding and straw application on the growth of rice and crawfish and the dynamics and transformation of nitrogen in paddy field were studied through farming crawfish in interior laboratory and straw application and feeding experiment,which provided theoretical basis and technical support for farming crawfish in paddy field to be used for nitrogen fertilization.(1)the laboratory test of crawfish feeds is conducted at the Institute of Fisheries Practice Base,Huazhong Agricultural University(114°29?E,30°28?N)during April to July,2016;setting four feeds with different nitrogen content,i.e.,corn(9.86 mg/g),peanuts(17.34 mg/g),compound feed(22.22 mg/g),soybean(37.98 mg/g),to study the effect of feed treatments on crawfish growth,and then conclude that the correlation between the rate of nitrogen in feed and excretion of crawfish;(2)a field experiment was conducted to study the effect of straw application and feeding treatment on rice yield and composition factors,crawfish production,soil physical and chemical properties,soil nitrogen dynamic variety as well as nitrogen use efficiency in the rice-crawfish system at Qianjiang Houhu Management Zone of Huazhong Agricultural University Rice-Crawfish Test Base(112°71?E,30°39?N),Hubei province in 2016 and 2017;The rice cultivar Taiyou 390 and crawfish variety Procambarus clarkii is selected for experimentation.A randomized complete block design is employed for six treatments with 3 replicates each,i.e.,straw application and feeding(S+F),straw application and no feeding(S+NF),straw no application and feeding(NS+F),straw no application and no feeding(NS+NF),straw application in rice monocropping(CK+S),straw no application in rice monocropping(CK+NS).The main results are as follows:(1)Effects of feeding different feeds on growth dynamics,feed uptake andassimilation of crawfish show that,and feeds to crawfish significantly increase the weight,the carapace length and the carapace width of crawfish.Among treatments have significantly difference,the weight of crawfish before stocking and after harvest,result is showed as follows: feeding compound feed > feeding soybean > feeding peanut > feeding corn > no feeding;the total length of crawfish show the trend: feeding compound feed >feeding soybean > feeding peanut > feeding corn > no feeding;in addition,there is no significant difference in the carapace length and the carapace width of crawfish in all treatments.Feeding compound feed lead to the maximum nitrogen assimilation in crawfish,and treatments cause the varieties of nitrogen assimilation in crawfish,as follows: feeding compound feed(337.18 mg)> feeding corn(299.39 mg)> feeding soybean(294.11 mg)> feeding peanut(216.26 mg)> no feeding(66.65 mg).The total amount of nitrogen in feces is shown as follows: feeding compound feed > feeding corn >feeding soybean > feeding peanut > no feeding;crawfish have significant difference in the utilization ratio of forage nitrogen,in particular: feeding corn > feeding compound feed > feeding peanut > feeding soybean.Feeding compound feed can not only benefit to the growth of crawfish,but also can improve the utilization rate of nitrogen in feed,the crawfish of feeding compound feed has high total amount of nitrogen in feces,and can reach the goal of nitrogen fertilizer compensation and fertilizer-reducing and increasing efficiency in paddy field.(2)The effect of straw application and feeding to crawfish on rice yield is reported as follows: NS+F>S+F>NS+NF>S+NF;compared to other treatments,feeding have a positively impact on grain yield,whereas straw application has no significant effect on rice yield,feeding can significantly increase grain yield,spikelets per panicle,setting percentage and the panicle number,but having no significant impact on 1000-grain weight.The effect of treatments on crawfish yield in rice-crawfish system show the trend as follows: S+F>NS+F>S+NF>NS+NF;compared to other treatment,feeding significantly increase crawfish yield,and the straw application had no significant impact on crawfish yield.(3)Effects of straw application and feeding on soil nitrogen indicate that the total nitrogen content in the soil is relatively stable,and there was no significant difference among treatments during two growth seasons,but the total nitrogen content had the highest value in S+F treatment,and reached to 2.0338 g/kg in the harvest period,and increased by 18.8% compared with CK+S.The rice-crawfish system can increase the total nitrogen content of the soil,and the same trend of ammonium and alkali nitrogen contentduring whole growth stage in all treatments,they firstly increased and then decreased,and the content of ammonium nitrogen in NS+F treatment was significantly higher than that in other treatments.Farming crawfish in paddy field increased the content of ammonium nitrogen and alkaline nitrogen in the soil.In the rice–crawfish system,the content of nitrate nitrogen in whole growth season firstly decreased and then increased,and the nitrate nitrogen content was lower in rice–crawfish system than that in CK.(4)The effect of straw application and feeding on nitrogen utilization,as follows:farming crawfish in paddy field increases Nitrogen Partial Factor Productivity,Nitrogen Harvest Index and Grain Harvest Index.In rice–crawfish system,the value of the Nitrogen Partial Factor Productivity is as follows: NS+F>S+F>NS+NF>S+NF,feeding and the straw no application raises the Nitrogen Partial Factor Productivity;about Nitrogen Use Efficiency,the trend of all treatments is: S+NF>NS+F>NS+NF>S+F,the value of the Rice Harvest Index is: S+F>S+NF>NS+NF>NS+F,indicating that S+F treatment will increase the Rice Harvest Index,which can achieve a great yields,but causing a low Nitrogen Use Efficiency or increasing nitrogen loss and waste,which will also cause environmental pollution,Therefore,in the rice-crawfish system it should be reasonable straw application and appropriate feeding feed.(5)Effects of straw application and feeding on nitrogen balance in rice-crawfish system showed that the cumulative output of nitrogen and the ratio of nitrogen output/input in four different treatments showed as follows: S+F>NS+F>S+NF>NS+NF,S+F treatment is more beneficial to the input of nitrogen into rice grains and crawfish.In the rice-crawfish system,the transformation rate of nitrogen is low,between 21.2%-58.7%,the loss of nitrogen main to the environment,resulting in the waste of resources. |
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