Impact Of Combination Of Dimethyl Disulfide And Chloropicrin On Microbial Communities In Continuous Cropping Soil And Dynamics Of Recovery

Fumigants are widely used to protect high-value cash crops to prevent and control soil-borne diseases. However, as a broad-spectrum agent, fumigants also have effects on non-target organisms. Traditional plate method, BIOLOG and molecular biology methods have been adopted after soil treated with mixture of DMDS and chloropicrin 1:1 to identify effects on soil microbial community structure after fumigantionFusarium spp. and Phytophthora spp. were inhibited as the soil treated with concentration of 68.34 mg﹒kg^-1 untill the day after 112 d .95% of pathogens were inhibited after treated with concentration of 683.36 mg·kg^-1 untill the day after 28 d when colony increased obviously because of soil microbial community structural is damaged by high dose,which resulted in dominant population increased significantly. Therefore, appropriate dose should be adopted when fumigation is used to inhibit the growth of pathogenic fungi.Bacteria, fungi and actinomycetes is obviously inhibited as the soil treated with concentration of 68.34 mg﹒kg^-1 with method of traditional plate culture. Bacterial communities recoveried after 3 days, while fungi and actinomycetes flora did after 28 days. Colonies of fungi increased most significantly after 28 days ,while bacteria and actinomycetes did after 49 days. Therefore, high dose of fumigation has more important effects on fungal community than bacteria and actinomycetes.The growth of soil microorganism has been inhibited and its diversity has been damaged as treated with dose of 68.34 mg﹒kg^-1,when BIOLOG ECO Microplate was used. McIntosh index was significantly lower than the control, while the Shannon index and Simpson index have no difference with control. AWCD values increased significantly when soil microorganism was treated with the dose of 683.36 mg﹒kg^-1 after 49 days,which has no significant difference with control. McIntosh index has no significant difference with control when soil microorganism incubation after 112 days, indicating that the using of carbon source species is no significantly differert. Therefore, mixed of DMDS and chloropicrin could reduce the ability using carbon sources and inhibit the growth of microorganisms. The methods of using carbon sources has been changed when treated with the concentration of 136.67 mg﹒kg^-1. Impact of fumigation on soil microorganism would be no significantly differert with control after a long of time.Functional diversity of bacterial community has been analysised by PCR-DGGE technique after treaded 0 d,49 d,112 d.The result is that soil bacterial community structure was inhibited with dose of 68.34 mg﹒kg^-1,but the effect had been reduced after 49 d,which was no significantly differert with control after 112d. Evenness of soil bacterial communities had no significant change in the recovery phase after fumigated.