|Allen, Leon - Hartwell|
Submitted to: Journal of Environmental Science and Health
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/6/2006
Publication Date: 1/1/2007
Citation: Ou, L., Thomas, J.E., Allen Jr, L.H., Vu, J.C., Dickson, D.W. 2007. Emissions and distribution of methyl bromide in field beds and applied at two rates and covered with two types of plastic mulches. Journal of Environmental Science and Health. 42:15-20. Interpretive Summary: Methyl bromide (MBr) in agriculture will be phased out since it has ozone depletion potential. However, through critical use exemptions, MBr still can be used for soil fumigation and post harvest treatments. Efforts to reduce emission losses and application rates are key components for granting critical use exemptions. USDA-ARS and University of Florida scientists compared the efficacy of two plastic covers, polyethylene film (PE) and virtually impermeable film (VIF), on surface emissions and subsurface distribution of MBr, which was applied at rates of 392 (high) and 196 (low) kg/ha. The results from this study show that VIF was a better barrier for reducing surface emissions of MBr from field-bed surface and for retaining adequate MBr concentration in the root zone for a longer period, as compared to the PE cover. In addition, if volatilization leaks from the bed edges could be blocked, MBr emission loss from the VIF-covered beds into the atmosphere would be negligible. Furthermore, since MBr concentration in the root zone of both PE and VIF-covered beds of low application rate was 3.6 to 6.1 times less than those of high application rate, the application of MBr at low rate may not provide adequate pest control, even if VIF is used.
Technical Abstract: Field experiment was conducted to compare two plastic mulches, polyethylene film (PE) and virtually impermeable film (VIF), on surface emissions and subsurface distribution of methyl bromide (MBr), applied at rates of 392 (high) and 196 (low) kg/ha. Within 30 min after injection to a 30 cm depth, MBr diffused upward to soil surface in all beds. However, MBr volatilized from the PE-covered bed surfaces into the atmosphere and this was greater with high application rate, while MBr volatilization from the VIF-covered beds was negligible. Volatilization loss also occurred from the edges of all beds, and was greater with high application rate.