Effects Of Rice-crayfish Farming On Biodiverity Of Paddy Field

The Rice-crayfish farming(RC)is a new eco-agricultural model realizing through food chain,niche and interspecific mutualism theory to combine rice planting with crayfish farming.Light,heat,water and biological resources of paddy were full used in RC.What's more,it has potential ecological,economic,social benefits and wide application prospects.In RC ecosystem,rice provides shelter,suitable water temperature,oxygen and food for crayfish.Meanwhile,the crayfish alleviates pests and weeds of paddy field by feeding insects and weeds,thus reducing the use of herbicides,pesticides and other pesticides.In order to clarify the effect of RC on the damage of paddy by Chilo suppressalis and ascertain the influence of RC on plant diversity and insect diversity in paddy.This study was conducted by setting up field tests and survey experiments.The research taking field tests in Junken Team of Houhu Farm,Qianjiang City,Hubei province during 2015-2016,and taking survey experiments in Bailuhu Farm,Jiyukou Town,Houhu Farm of Qianjiang City to compare weeds diversity and insects diversity between the conventional paddy(CK)and the different years paddy of RC(RC1?RC2?RC3?RC4?RC9)in 2015,and taking survey experiments in Houhu Farm to compare insects diversity between CK and RC1?RC2?RC5?RC10 in 2016.And investigation on the effect of RC on the damage of paddy by Chilo suppressalis in Bailuhu Farm,Jiyukou Town,Houhu Farm between 2015-2016 were carried out simultaneously.The main results were as follows:1.Analysis of the effect of RC on the damage of paddy by Chilo suppressalis showed that: The RC significantly reduced the source of Chilo suppressalis of paddy in the second year by covering water in winter and spring,thus affecting the yearly development progress of Chilo suppressalis.Compared with CK,the overwintering cardinal larvae number of Chilo suppressalis decreased by 100%,the second generation larvae number of Chilo suppressalis decreased by 46.6%,the third generation larvae number of Chilo suppressalis decreased by 71.8%,the dead heart rate decreased by 40.6% and the moth peak of Chilo suppressalis is about 10 days late in RC paddy,which indicated that RC significantly reduced the harm of Chilo suppressalis and delay the development progress of Chilo suppressalis.2.Analysis of the effect of RC on insect diversity of paddy presented that: the total number of insects decreased by 41.0%,the phytophagous insects decreased by 42.5%,the predatory insects decreased by 47.0%,the neutral insects decreased by 37.7%,and the parasitic insects decreased by 57.1% after a year of RC farming.(and the number of phytophagous,predatory,insects,neutral and parasitic insects reduced 42.5%,47.0%,37.7% and 57.1% after a year of RC farming,respectively.)The results of the survey exhibited that the number of insects of paddy decreased first and then increased with the increase of RC's conducting years.Survey data in 2016 showed that the total number of insects and the number of all kinds of insects in RC1 paddy was the least.However,it is RC2 from the 2015 survey data.the least one is RC2 in survey of 2015.Alongwith the conducting years of RC,the phytophagous insect pests increased,but the predators also increased,and the range of increasing was greater,so pests decreased accordingly.3.Analysis of the effect of RC on plant diversity of paddy revealed that: weed species,amount of individuals and coverage of interior and margin in paddy significantly decreased after a year of RC farming.The interior decreased by 54.5%,50.5% and 62.6% respectively,and the margin decreased 33.3%,50.6% and 28.4% respectively.Data from the 2015 survey show that the diversity of plants decreased and then increased with the longer years of RC.Weed species and amount of individuals are the least in RC4 field.In conclusion,RC changed the dominant species of weeds and affected plant diversity of rice field.In short,compared to CK,RC can significantly reduce the harm of Chilo suppressalis and changed the composition and structure constitution of the community of weeds and pests in paddy.Their biodiversity decreased along with the increase of RC conducting years RC.