Effect Of Soil Activation After 1,3-Dichloropropene Fumigation On Soil Microbial Community Structure And Tomato Growth

Tomatoes are China's main economic crops.Most of China's tomatoes are produced under protective agriculture such as plastic greenhouses or greenhouses,which increases the spread of soil pathogens and soil-borne diseases.Soil-borne diseases are one of the most important limiting factors for plant growth.The continuous cultivation of high-value crops on the same land,such as tomatoes,strawberries,cucumbers,ginger and notoginseng,can lead to accumulation of soil-borne disease pathogens such as Fusarium,Phytophthora infestans and root knot nematodes,which will cause soil damage.The nutritional structure and even the micro-ecological balance are destroyed,which may reduce crop yields and even lead to crop failure.Although soil fumigant is one of the most direct,fast and effective methods to prevent and control soil-borne diseases,but it usually affects non-target soil microorganisms.Microbial fertilizers or organic fertilizers have been reported to be beneficial to the soil ecological environment.This article defined it as "soil activating substance".Adding substances such as microbial fertilizers and organic fertilizers after fumigation is expected to reshape the healthy soil microbial community.At the same time,using microbial fertilizers or organic fertilizers to biologically activate the soil after fumigation may promote the prevention and control of soil-borne diseases.The soil fumigant 1,3-Dichloropropene(1,3-D)is widely used because of its effective treatment of pathogenic nematodes and weeds.In this experiment,1,3-D fumigated tomato soil was used.After fumigation,Bacillus Subtilis and Trichoderma Harzianum(singly or in combination)or humic acid organic fertilizers were added;The changes in soil physical and chemical properties,soil enzyme activity,tomato growth and yield,and soil microbial community composition and diversity were monitored in various aspects.The main conclusions were as follows:(1)Fertilizer activation treatments after indoor fumigation promoted the increase of soil p H and electrical conductivity;after treatments,the soil urease,soil urease and soil catalase activities were all improved to varying degrees;similar results were also found in pot and field experiments.Field test results found that due to the inhibition of nitrification by the fumigation treatment,the fumigation treatment reduced the concentration of nitrate nitrogen,but the concentration of nitrate nitrogen increased by 14.3%-151% after fertilization activation,and the p H value of the soil increased significantly from 1.20% to 4.40 %;It shows that fertilization activation can effectively relieve or alleviate the inhibitory effect of fumigants.The experimental results found that the abundance of soil bacteria and fungi was affected by soil physical and chemical properties and enzyme activities,but different types of bacteria or fungi have different effects on soil physical and chemical properties and enzyme activities.(2)Field results showed that soil fumigation biological activation treatments significantly reduced the population density of tomato Fusarium(control effect 15.9%-94.3%)and Phytophthora(control effect 3.10%-88.7%).The application of microbial fertilizer after fumigation can further inhibit soil-borne disease pathogens.Significant changes have taken place in the community structure of soil bacteria and fungi.At the same time,we have discovered the diversity of soil bacteria and fungi and beneficial microorganisms(such as Sphingomonas,Bacillus,Mortierella and Trichoderma).The abundance increased significantly within a short period of time after the fumigation organisms were activated,and both were significantly positively correlated with the inhibition of soil pathogens,which may enhance the ability of soil or plants to inhibit Fusarium and Phytophthora.The activation treatments after indoor fumigation stimulated the growth of Actinobacteria(27.2%),and increased the relative abundance of the biocontrol microbacteria such as Sphingomonas,Pseudomonas,Bacillus and Lysobacter.When the Bacillus subtilis fertilizers were mixed with the Trichoderma harzianum fertilizers,the relative abundance of these beneficial microbacteria was significantly increased.These results indicate that fertilization activations after fumigation can increase the population of beneficial microorganisms in the soil in a short time.(3)The pot experiment found that the application of microbial fertilizers after 1,3-D fumigation promoted the growth of tomatoes.The addition of microbial fertilizer activations after fumigation increased tomato plant height(14.7%-18.8%),stem thickness and fresh weight(20.6%-38.8%)to varying degrees.At the same time,field experiments had also obtained consistent results.Fumigation and fertilization activation significantly increased tomato yield(7.50%-24.5%).In summary,the reduction of soil-borne pathogens may be due to the direct effect of soil fumigation and microbial fertilizers,or by optimizing the soil microbial community structure to improve soil non-biological factors(such as soil p H,fertility structure,etc.),and enhance soil ecological functions,thereby inducing plant system resistance,promoting tomato growth and increasing tomato yield.