DOMESTIC, EXOTIC, AND EMERGING DISEASES OF CITRUS, VEGETABLES, AND ORNAMENTALS (DEED)
Location: Subtropical Plant Pathology Research
Title: Soil Fate of Agricultural Fumigants in Raised-Bed, Plastic-Mulch Crop Production Systems
Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: July 1, 2011
Publication Date: July 1, 2011
Citation: Chellemi, D.O., Ajwa, H.A., Sullivan, D.A., Alessandro, R.T., Gilreath, J.A., Yates, S.R. 2011. Soil Fate of Agricultural Fumigants in Raised-Bed, Plastic-Mulch Crop Production Systems. Journal of Environmental Quality. 40:(no page).
Soil concentrations and degradation rates of methyl isothiocyanate (MITC), chloropicrin (CP), 1,3-dichloropropene (1,3-D), and dimethyl disulfide (DMDS) in the vapor and nonvapor phase were determined under fumigant application scenarios representative of commercial raised bed, plastic mulched vegetable production systems. Concentrations of volatile organic compounds (VOC) in the soil atmosphere also were measured using portable photo-ionization detectors. In three 0.4 ha trials conducted in Florida, MITC and CP were detected at concentrations = 0.66 and 1.74 µg cm-3, respectively, in the soil atmosphere 5 days after their application. In three 0.4 ha trials conducted in Georgia, CP and MITC in the soil atmosphere were = 0.05 µg cm-3 of air at 5 days after application. Ranked in order of impact on the persistence of fumigants in soil were soil water content (moisture), field preparation (tilth), plastic film type, and soil texture. Fumigants were readily detected 13 days after application when applied in uniformly compacted soils with water contents 2x field capacity and covered by a virtually impermeable or metalized film. By contrast, 1,3-D and MITC had dissipated 5 days after application in soils with numerous large ( > 3mm) clods and water contents below field capacity that were covered by low density polyethylene. Soil degradation of DMDS and CP was mainly due to biological activities while degradation of 1,3-D was principally abiotic. Soil degradation of MITC was both biotic and abiotic and varied from site to site. This study demonstrates improved soil retention of agricultural fumigants can be obtained under commercial application conditions through the use of good agricultural practices.