Submitted to: Journal of Environmental Quality
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/26/2010
Publication Date: 7/29/2010
Citation: Wang, D., Gao, S., Qin, R., Browne, G.T. 2010. Lateral movement of soil fumigants 1,3-Dichloropropene and Chloropicrin from treated agricultural fields. Journal of Environmental Quality. 39:1800-1806. Interpretive Summary: California is a major grape and tree fruit producing state in the U.S. Each year, a significant portion of old and non-productive vineyards and orchards is removed and replanted with new vines and trees. After planting, the growth and establishment of young vines and trees can be impacted by a complex of soil physical, chemical, and biological problems, commonly known as the “Replant Disease”. To ameliorate this “Disease”, soil fumigation, among other non-chemical cultural techniques, is often used by the growers to control the replant problems of biological origin, e.g. soil-borne plant pathogens and parasitic nematodes. The objective of the study was to measure lateral fumigant movement in the soil vadose zone away from the treated fields with or without a tarp cover. The goal was to provide in-situ evidence for making risk assessments on crop and environmental safety. Two side-by-side field trials were conducted in 2007 and repeated in 2008 at the USDA-ARS San Joaquin Valley Agricultural Sciences Center located near Parlier, CA. Four sets of soil gas probes were installed, for each fumigation treatment, at preselected lateral distances up to 6.1 m from the treated area. The study clearly demonstrated that fumigant gases were capable of moving beyond the treated fields to lateral distances that could be considered unsafe for adjacent existing crops or water bodies, e.g., 3 m for vineyard fumigation and 6 m for orchard. The beneficial use of VIF tarp for reducing emissions on treated fields could inadvertently enhance lateral gas transport in the soil away from the treated fields.
Technical Abstract: Fumigant 1,3-dichloropropene (1,3-D) and/or chloropicrin (CP) are often used for controlling soil-borne plant pathogens and parasitic nematodes before old and nonproductive vineyards and orchards are replanted. To help evaluate crop safety and environmental risks with the replant fumigation, four field trials were carried out, over two years, to measure 1,3-D and CP lateral movement in the soil away from the treated fields. Shank injection with a virtually impermeable film (VIF) cover or without cover was used for two vineyard experiments and a spot drip application without tarp cover was used for the orchard fumigation experiments. Results clearly showed that 1,3-D and CP gases moved laterally at least 3 and 6 m from the treated field when the fumigants were applied by shank injection. The VIF tarp appeared to have enhanced lateral gas transport. 1,3-D and CP gases moved at least 1.5 m from the center of spot drip application. Future experiments may focus on bioassay of possible phytotoxicity caused by lateral fumigant gas transport and fumigant concentrations in nearby water systems.