Entomopathogenic Nematode And Microbe Community Variation In Strawberry Continuous Cropping Soil And The Soil Amendiment Effects

Many negative respects were caused by the continuous cropping problem,and it has serious effects on entomopathogenic nematode and soil microorganism,particularly.In strawberry planting,the problem of continuous cropping also affected the normal growth of plants and the stable of soil ecology.This study contrasted the different physicochemical properties,soil microorganism community,soil nematode communtiy and soil enzyme activity of strawberry soil.Firstly,the research aimed at figuring out the most obvious period of effect after the replantation of strawberry.Secondly,confirming the year when the continuous cropping factors changed and the year when deteriorations of them stopped.Thirdly,the paper analyzed the variation trend of major elements among the different factors in continuous cropping.Finally,the paper verified the possible reasons of restrain and the effectiveness of restoration for continuous cropping soil of strawberry by experiments.Main results are as follows:1.The harvest stage of strawberry was the most obvious period in the continuous cropping of strawberry.2.With the increase of continuous cropping years,the proportion of bacteria-feeding nematods(insect nematode)in continuous cropping soil constantly decreased,proportions of plant-feeding nematodes,fungal-feeding nematodes constantly increased.The changes stared in the 2nd year as well as the deteriorate.The changes of soil nematode food network were most obvious after continuously cropping for 8 years,the main reason consist:1)the ratio of bacterial-feeding nematode and fungal-feeding nematode which was directly related to entomopathogenic nematode to plant-feeding nematodethe were decreased.Change of the proportion of insect nematode,plant-feeding nematodes and fungal-feeding nematodes;2)The nematode of 1-2 cp value replaced the nematode of 3-5 cp value.Redundancy analysis indicates that the rapidly available phosphorus had the most significant positive correlation with the Acrobeloides and the most significant negative correlation with Tylenchus.Soil pH,available nitrogen(AN),ammonium Nitrogen(NH4+-N),available potassium(AK)and organic matter(SOM)had the maximum positive correlation with Aphelenchus,and the maximum negative correlation with Diploscapter;Pratylenchus might have a positive effect on soil restoration,the increase of Diploscapter and Cephalobus might intensify the continuous cropping effect.3.The diversity of soil bacteria began to change obviously in the 4th year for continuous cropping,and the changes started to stay stable in the 10th year.The main bacteria genus that have the significant difference in continuous cropping are Bacillus,Sphingomonas,Nitrospira,negative correlation with physicochemical property,and Sphingomonas,Nitrospira and Flavobacterium have positive correlation with physicochemical property.The 16S functional gene prediction results showd no difference.Bacillus might have some effect on the restoration of soil function.However,the secondary metabolite(terpene)of Flavobacterium could produce the continuous cropping effect.4.The diversity of soil fungi began to change obviously in the 2nd year for continuous cropping,and the changes tend were to be stables in the 10th year.The main fungi that had the significant difference in continuous cropping were Pseudallescheria,Aspergillus,Acremonium,Fusarim,Mortierella,Gibberella,Guehomyces and Humicola.Correlation analysis indicated that Acremonium,Artrobotrys and Microascus had positive correlation with physicochemical property.And Fusarim,Gibberella and Guehomyces had the negative correlation with physicochemical property.5.With the increase of continuous cropping years,the contents of SOM,AN,NH4+-N,AK,and pH were declined,and content of AP was increased in soil.The effect of physicochemical property began in the 2nd to 4th year.After cropping continuously for 8 years,all physicochemical property indicator did not change no longer,except pH and organic matter declined continuously.6.The fresh weight of strawberry stem and leaf began to decline in the 4th year after continuous cropping,and the dry weight of strawberry stem and leaf began to decline in the 8th year.The fresh/dry weight of strawberry root begins to decline in the 2nd year.By comparing the root gene expression between continuous cropping strawberry and non-continuous cropping strawberry,there were 88 up-regulated genes and 108 down-regulated genes.The main function of up-regulated genes were related to protein metabolism,signal transduction,and the synthesis,transport and decomposition of secondary metabolites.The main function of down-regulated genes were post-transcriptional modification and protein metabolism.7.The experiment of terpenoids on soil and the growth of strawberry indicated that three kinds of terpenoids(Geraniol,Citronellol,Myrcene)had the effect to restrain the growing of entomopathogenic nematode,meanwhile terpenoids have the ability to restrain the strawberry growing and weaken the soil enzyme activity.The results of soil amendmented by the insect metabolite and entomopathogenic nematode preparation soil amendment(SA),organic fertilizer and Bacillus shown that SA has the highest restoring effect on promoting the weight of fresh strawberry roots,the activity of soil invertase and soil urease,promoting the growing of soil bacteria community and enhancing the proportion of insect nematode.Organic fertilizer had the best restorative effect in promoting the growth of root,stem and leaf,and improving the activity of alkaline phosphatase.Bacillus had the best restorative effect in improving the activity of Invertase.