Submitted to: Chemosphere
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/14/2008
Publication Date: 5/27/2008
Citation: Qin, R., S. Gao, J.A. McDonald, H. Ajwa, S. Shem-Tov, and D.A. Sullivan. 2008. Effect of plastic tarps over raised-beds and potassium thiosulfate in furrows on chloropicrin emissions from drip fumigated fields. Chemosphere. 72:558–563. Interpretive Summary: As a high-value cash crop, strawberry is heavily dependent on soil fumigation for controlling soil pests to achieve profitable yields. Most soil fumigants are defined as volatile organic compounds (VOCs) and their emissions must be minimized to reduce their detrimental impact on humans and the environment. Fumigation through drip-irrigation has been developed and commonly practiced in strawberry fields with raised bed designs. This research determined the effectiveness of low density polyethylene (LDPE) and virtually impermeable film (VIF) tarps over raised-beds and applying potassium thiosulfate to furrows on chloropicrin emission control in a large strawberry field trial at Santa Maria of California. Field data indicated that VIF reduced emissions slightly more than LDPE and emissions were mainly from the beds and minimal from furrows, which indicates the importance of minimizing emissions using low permeability tarps. This research provided information on techniques that can be used to minimize fumigant emissions from soil fumigation for strawberry production and further research needs.
Technical Abstract: Plastic tarps are commonly used in raised bed strawberry production to minimize emissions of preplant soil fumigants and are left in place throughout the growing season as part of the standard cultural practices. Use of tarps with lower permeability or soil amendments with chemical such as thiosulfate can reduce fumigant emissions. A field study was conducted near Santa Maria, CA to determine the effects of low density polyethylene (LDPE) and virtually impermeable film (VIF) over raised beds and applying potassium thiosulfate (KTS) in furrows on reducing chloropicrin (CP) emissions from a strawberry field trial. Four fields (or treatments) were tested treated with 224 kg ha-1 CP drip-applied 3 cm under the soil surface. The CP flux from bed tops and furrows and gas-phase concentrations under the tarps were monitored for 5 d. The CP emission flux and concentration under tarp were highest immediately following the CP application. Diurnal temperature change affected CP concentration and emission fluxes (higher values during the day and lower at night). Slightly higher CP emission occurred under LDPE tarp (19%) compared to VIF (17%). The KTS application to furrows did not reduce emissions, partially because CP emissions were extremely low from the furrows (<0.2% of total emission loss) compared to the beds. This study suggests that VIF tarps were slightly more effective in reducing CP emissions than the LDPE tarps. Reduction of CP emissions should focus on the raised beds where emissions were dominant rather than on furrows.