Evaluation Of Chloropicrin Alternated With Biofumigation Against Soil-borne Diseases In Strawberry And Effect On Soil Microbial Community Structure

Strawberry?Fragaria×ananassa Duch.?is a high-value crop,and its huge economic benefits have prompted farmers to grow more and more strawberries.In order to achieve annual strawberry fruit production,farmers often plant strawberries in the same land year after year.The land cannot be rotated or fallow.The soil-borne pathogens in the soil gradually accumulate,which harms strawberry growth and affects strawberry yield and quality.Soil-borne diseases such as strawberry root rot caused by Rhizoctonia solani and Fusarium,strawberry anthracnose caused by anthracnose have sharply reduced strawberry yield.At present,soil fumigation is the most direct,rapid and effective method for controlling soil-borne diseases,pests and weeds.After extensively banning the use of methyl bromide?MB?in the agricultural sector in 2015,fumigants such as chloropicrin and 1,3-dichloropropene have become effective chemical substitutes for MB.Biofumigation is a natural,eco-friendly,non-chemical alternative to MB.Under the policy of reducing the use of pesticides and fertilizers issued by the Ministry of Agriculture and Rural Affairs of People's Republic of China,this experiment designed a fumigation mode for chloropicrin alternated with biofumigation?denoted as CAB?,and the effects of this fumigation mode on the control of soil-borne diseases,soil physicochemical properties,strawberry fruit yield and quality,and community composition and diversity of soil bacteria and fungal microorganisms were systematically evaluated.The main research conclusions are as follows:?1?The mycelial growth inhibition rate of fresh chicken manure against Fusarium oxysporum,Phytophthora infestans,Pestalotiopsis spp.and Rhizoctonia solani was increased with the concentration of fresh chicken manure.When fresh chicken manure was added at a concentration of 62.469 g/kg,it could effectively inhibit the growth of four soil-borne pathogenic fungi by 90%.It is shown that fresh chicken manure can be used as a biofumigation material,which provides a theoretical basis for the operability of chloropicrin alternated with biofumigation.?2?The indoor test results of CAB treatment showed that Pic and CAB treatment had better control effects on Fusarium spp.,Phytophthora spp.and root-knot nematode.Moreover,the relative control effect of CAB40 treatment on Fusarium spp.was not significantly different from Pic treatment,and the relative control effect on root-knot nematodes was significantly higher than Pic treatment.The results of indoor pot experiments show that:CAB treatment was similar to Pic treatment in that it could significantly increase the plant height and fresh weight of strawberry plants.?3?The results of field evaluation of CAB treatment showed that:CAB treatment can significantly improve the physicochemical properties of the soil in long-term use of chloropicrin fumigation plots,and significantly increased the contents of NO₃^--N,available phosphorus and potassium and organic matter.And the control effect on Fusarium spp.is 92.23%-99.77%,the control effect on Phytophthora spp.is 66.90%-88.69%.Compared with the control treatment,the average marketable yield and total income of strawberries after CAB treatment can increase by 20.99%and 21.58%.CAB treatment significantly increased the content of chlorophyll in leaves and the content of soluble sugar and ascorbic acid in strawberry fruits,which indicated that CAB treatment improved the taste and quality of strawberry fruits.?4?Compared with the control,Pic and CAB treatment significantly changed the diversity of bacterial and fungal communities in the soil at the initial stage of fumigation.CAB treatment could restore the soil microbial community structure and composition to the control level at 30 days after fumigation.However,Pic treatment still had a significant effect on bacterial and fungal communities in the soil at the end of the sampling.At 0 day after fumigation,CAB significantly increased the relative abundance of Bacillus,Pseudomonas,Nitrospira,and Streptomyces in the soil,but 90 days after fumigation,they returned to the control level.At 0 day after fumigation,CAB treatment increased the relative abundance of Mycothermus and Thermomyces.And 90 days after fumigation,the relative abundance of Mycothermus was still higher than the control treatment.At 30 days after fumigation,the relative abundance of Chaetomium increased significantly after CAB treatment.And compared with the control,the relative abundance of Fusarium was significantly reduced in CAB and Pic treatments.These results showed that CAB treatment can effectively prevent soil-borne pathogens without disturbing the soil microbial community and can increase the relative abundance of beneficial microorganisms in the soil.Based on the above test results,CAB treatment can not only significantly improve the soil physicochemical properties of Pic treatment plots,reduce soil-borne pathogens,increase strawberry yield and quality,but also can quickly restore the diversity of soil bacterial and fungal microorganisms after fumigation.In addition,CAB treatment is also important for reducing the use of chemical fumigants,effectively using livestock manure,reducing environmental pollution and reducing planting costs.