Evaluation of TIF to reduce fumigant emissions and the potential to use reduced rates

Authors: Gao, Suduan; QUI, RUIJUN - University Of California; AJWA, HUSEIN - University Of California; SULLIVAN, DAVE - Sullivan Environmental; Wang, Dong

Submitted to: Proceedings of International Research Conference on Methyl Bromide Alternatives
Publication Type: Proceedings
Publication Acceptance Date: 9/6/2010
Publication Date: 11/1/2010
Citation: Gao, S., Qui, R., Ajwa, H., Sullivan, D., Wang, D. 2010. Evaluation of TIF to reduce fumigant emissions and the potential to use reduced rates. Proceedings of International Research Conference on Methyl Bromide Alternatives. p.12-1 - 12-4.

Interpretive Summary: Achieving low emissions from soil fumigation would help maintain the future availability of soil fumigants to important commodity groups such as the strawberry group who depend on soil fumigation for their production. A new low permeability tarp named totally impermeable film (TIF) was tested in large field applications for its tarping potential to reduce emissions from broadcast application of 1,3-dichloropropene and chloropicrin in comparison with the standard polyethylene film. The field data show that not only can this film effectively reduce emissions, but also higher concentrations are retained with a more uniform distribution of fumigants in soil, which can lead to improved efficacy and the potential for using reduced rates. After tarp-cutting, however, surges of emissions occurred from both tarps with much higher emission rates from the TIF tarp than the standard film. Thus, a proper waiting period needs to be determined to minimize potential exposure risks. This research provides important information on what can be encountered when using the TIF tarp in soil fumigation in terms of increasing fumigant use efficiency and reducing negative environmental impacts.

Technical Abstract: Strawberry growers in California rely heavily on soil fumigation to assure profitable berries and high yields. However, the adverse impact on air quality from fumigant emissions threatens the availability of fumigants for agricultural use. The objective of this research was to determine the performance of a new low permeability film (Vapor SafeTM, also called totally impermeable film or TIF) to reduce fumigant emissions and to improve fumigant distribution in soil that may lead to the usage of reduced rates. A large field trial was conducted in Ventura, CA in 2009. Continuous emissions (including before and after tarp-cutting) of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) were measured from shank injection of a 50/50 mixture from two large separate fields that were tarped with either standard polyethylene (PE) film or TIF. Other measurements included concentrations under the tarp, fumigant distribution in soil profile, and residual fumigants in the soil by the end of the trial. Emission flux of 1,3-D and CP from the TIF-tarped field was substantially lower than that from the PE field during a tarp-covering period of 6 days. The total emission loss was 2% of total applied for 1,3-D and <1% for CP before the tarp was cut, as compared to 43% for 1,3-D and 12% for CP from the PE field. Upon tarp-cutting, however, surges of emissions occurred with fluxes much higher from the TIF field due to the much higher concentrations retained under the TIF tarp than the PE tarp. Chloropicrin emissions after tarp-cutting were very low. A more uniform and higher concentration profile in the soil gas-phase was also observed at or above injection depth under TIF compared to the PE tarp, indicating that there is great potential for using reduced rates under TIF while still maintaining satisfactory pest control. The surge of emissions of 1,3-D following tarp-cutting presents a high potential exposure risk that must be addressed for the safe use of TIF in soil fumigation.