Study On Application Technology Of Several Soil Fumigants In Vegetable Fields

With the development of agricultural industry structure in China, greenhouse cultivationand planting of high-value crops industry model is evolving. While income of farmers hasbeen rising, providing favourable conditions for the spread of soil-borne diease. Now usingthe soil fumigants is the most efficient and the most direct way to control the soil-bornedisease. Methyl bromide（MB）is the most traditional soil fumigant which is recognized bythe world. But as a stratospheric ozone depleting compound, it should be phased out by2015in China based on “the Copenhagen Amendment to the Montreal Protocol”. To find thealternative of MB is becoming hot topics in recent years.In the paper, we ascertain the toxicity of chloropicrin, dazomet, metham-sodium,1,3-Dand the mixtures of the1,3-D and chloropicrin against Phytophthora capsici Leonian andMeloidogyne incognita. The dynamic recovery of mixture of1,3-D and choropicrin1:1on thefungi, bacteria, actinomycetes, Fusarium spp. and Phytophthora spp. in the soil were studiedthrough laboratory experiment. Via the field experiment of cucumber, tomato, pepper andginger, we evaluatived the control effect of the alternative of MB to the root-knot nematode,pepper blight, ginger blast, combined with different points of disease, disease index and yieldsurveys. The results were as follows:The laboratory result indicated that the EC₅₀values of soil fumigants chloropicrin,dazoment, metham-sodium and1,3-D to Phytophthora capsici Leonian were0.1213,2.43528.2986,8.4517mg·L^-1, respectively. The EC₅₀values of soil fumigants chloropicrin,dazoment, metham-sodium and1,3-D to Meloidogyne incognita were0.1789,0.2166,0.3025,1.2294mg·L^-1, respectively. The toxicity of the mixtures with the mixing ratio of1,3-D andchloropicrin as1:2,1:1,2:1against Phytophthora capsici Leonian were0.1442,0.2449,1.1316mg·L^-1, CTC1:2＞CTC1:1＞CTC2:1,1:1,1:2ratio had additive effect; The toxicity ofthe same mixing ratio against Meloidogyne incognita were0.6072,0.3212,0.1949mg·L^-1,CTC2:1＞CTC1:1＞CTC1:2,1:1,2:1ratio added significantly. The optimal matching ratio of1,3-D and chloropicrin was1:1, considering both the economic benefits and the principle oftreating a variety of disease.The dynamic recovery of mixture of1,3-D and choropicrin1:1on microbial number in the soil were studied through laboratory experiment. The results indicated that the bacteriawere inhibited at the beginning then decreased later on and finally became stimulating; theactinomyces were inhibited at the beginning then became stimulating at the14th day andthen became the strongest stimulus at the28th and finally decreased gradually; the fungalwere inhibited significantly then became the trend of strong irritation at high concentration.During incubation time, the effects of the mixture on Fusarium spp. and Phytophthora spp.were significantly inhibition. However, the mixture at high concertration tested hadinhibition-restoration-irritation effect on Fusarium spp. and Phytophthora spp., while thepromotion became more significant.1,3-D and the mixture with other fumigants was the best soil fumigant in controlroot-knot nematode. The nematode dedine rates of1,3-D30g/m²and1,3-D+dazoment45g/m²were above90%in cucumber and tomato crops. Under the treatment of1,3-D+dazoment45g/m²and1,3-D+chloropicrin40g/m²in pepper crops, the reducing rateswere78.62%and83.82%. The ginger field experiment results that the nematode dedine ratesof1,3-D45g/m²,1,3-D+chloropicrin40g/m²,1,3-D+dazoment45g/m²were above90%.The field trials in pepper show that chloropicrin and the mixture with other fumigantswere the best alternative fumigant to control pepper blight. The reducing rates of chloropicrin40g/m², chloropicrin EC40g/m², chloropicrin+1,3-D40g/m²were84.50%,87.61%,80.58%.The field tests in ginger show that chloropicrin and the mixture with other fumigantwere the best alternative fumigant to control ginger blast. The dedine rates of chloropicrin40g/m², chloropicrin EC40g/m², chloropicrin+1,3-D40g/m²were73.01%,73.92%,76.73%.According to the yield surveys, the fumigation were significantly higher than the blankcontrol. There were no significant difference in different fumigants, but with the increasing ofconcentration, yields increase. Taking account into the disease index, yield and economic cost,we recommend that use1,3-D+dazoment45g/m²to control nematode in cucumber andtomato crops and use1,3-D+chloropicrin40g/m²to control of the soil diease in pepper andginger crops.Combined laboratory experiment with field test, the paper evaluated control effect of different methyl bromide alternative fumigants to the vegetable root-knot nematodes, pepperblight, ginger blast and other soil-borne diseases which provided theory evidence for theapplication of methyl bromide alternative fumigants in China.