Issues and Management In Using Low Permeability Tarps to Reduce Emission From Broadcast Soil Fumigation.

Emission reduction from soil fumigation is required in the San Joaquin Valley, California. Several field tests have shown that the low permeability tarp, such as TIF, can reduce emissions more than 90% compared to standard polyethylene tarps while the tarps are in place. This effectiveness, however, can be offset by surging emissions after tarps are cut for removal because this surge could increase exposure risks to workers and by-standers. The objective of this research was to develop strategies for the safe use of TIF tarp in soil fumigation for both emission reduction and effective pest control. An extended tarp-covering time period can reduce the surge in fumigant emission and increase fumigation efficacy, but could also delay crop planting. Because fumigant retention time in soil is increased when using TIF, reduced fumigant application rates could still result in sufficiently high exposure for satisfactory control on soil-borne pests. Field trials have been conducted to determine the potential of TIF tarp to reduce emissions and to lower fumigant application rates for perennial crops. The studies revealed that fumigant emission was substantially reduced and pest control efficacy was improved by TIF tarp compared with standard tarps. Some reduced rates when sealed with TIF offered similar pest control as the full rate under standard tarp. Delayed tarp-cutting time to avoid surging emissions can be projected based on fumigant concentrations remaining under the tarp and in the soil. Continuous research is to determine the proper tarp-cutting time associated with application rates, application methods and soil/environmental conditions.