Rule And Regulation Of Dimethyl Disulfide Atmospheric Emissions,Soil Distribution

Dimethyl disulfide(DMDS)has good control effect on soil borne diseases and insect pests in various crops and has no Ozone Depletion Power which has been the most promising alternative to Methyl bromide.It’s atmospheric emission,soil distribution and soil residual are of great influence on its efficacy.So,it is important to clarify the above-mentioned environmental behavior,which has the important significance on scientific use of DMDS.In this paper,using soil columns in the laboratory to study the effects of soil types,soil moisture content and covering film on environmental behaviors of DMDS,which provided technical support and theoretical basis for scientific use of DMDS.The main research results are listed as follows:1.Systematically studied the rules of DMDS emission,vertical distribution and residual environmental behavior under three soil types.The results showed that there were significant differences in the trends of DMDS emission,distribution and residual environmental behavior under the three soil types.The cumulative emission loss of DMDS in sandy loam soil and red loam soil is significantly higher than that in black soil.In addition,DMDS is relatively slow and continuous emission process under red loam soil;DMDS distribution ability is the strongest under sandy loam soil,followed by black soil and red loam soil;The order of DMDS residue decline in the soil was: black soil> red loam soil> sandy loam soil.2.Systematically studied the rules of DMDS distribution and residual environmental behavior under three soil moisture contents.The results showed that soil moisture content had a great influence on the distribution and residual environmental behavior of DMDS.The distribution ability of DMDS was negatively correlated with soil moisture content.The distribution ability decreased with the increase of soil moisture content.The order of DMDS residue decline in the soil was: 6% soil moisture content > 12% soil moisture content > 18% soil moisture content.3.The barrier properties of four plastic films to DMDS were systematically evaluated.The results show that the plastic films of different materials have significant differences in barrier properties of DMDS,and the barrier stability is also different.PVDC and EVOH have significantly better barrier properties to DMDS than PE and PVC.The film barrier properties of different materials decrease with the increase of temperature.The order of influence is as follows: PVC > PE > EVOH > PVDC;the affect of humidity on the barrier properties of different materials are inconsistent,EVOH is most affected,PE is less affected,PVC and PVDC are basically unaffected.4.The effects of covering films on the emission,distribution and residual environmental behavior of DMDS were systematically evaluated.The results showed that the film significantly affected the DMDS emission,distribution and residual environmental behavior.Covering film significantly reduced the DMDS atmospheric emission loss,and TIF film was superior to PE film;The gas concentration with a DMDS dose of 40 g·m-2 within 5 cm of the top of the column at 6 h was about 5.5 times higher than the concentration of 25 cm and similar higher concentrations of DMDS5 cm and 25 cm deep when films were used,therefore covering film the significantly increased distribution ability,especially the DMDS gas concentration in the deep soil;The total DMDS soil residues remaining in the soil,as a percentage of the initial DMDS dose at 40 or 80 g·m-2 were,respectively,0.47 and 0.47 with bare soil,0.91 and 1.18 with PE,1.17 and 5.58 with TIF,this result show that the soil residual concentration have significantly increased with covering fimls.By comparing the above environmental behavior differences between the two application doses under mulching,it is clear that covering film has the potential to achieve the effect of reducing the dose of DMDS and increasing efficiency.Therefore,the recommended amount of DMDS is 50 g·m-2,and the recommended soil moisture content is 12%~15%.After the application of DMDS,recommended treatment of soil surface covered with film(PE film,TIF film)for at least 15 days.When TIF film is used,the dosage should be appropriately reduced,the open air time should be extended,and the safety test should be carried out before planting.The safety open time required for sandy loam soil,red loam soil and black soil was: 7 d,21 d,14 d.Thus,DMDS can reduce the dose of use and the harm to environmental and non-target organisms under reasonable and appropriate application conditions.