|Qin, Ruijun - UC DAVIS|
|Ajwa, Husein - UC DAVIS|
Submitted to: International Conference on Methyl Bromide Alternatives and Emissions Reductions
Publication Type: Proceedings
Publication Acceptance Date: September 9, 2008
Publication Date: November 10, 2008
Citation: Qin, R., S. Gao, and H. Ajwa. Low permeable tarps reduce emissions from drip-applied inline in a strawberry field trial. Ann. Int. Res. Conf. on MeBr Alternatives and Emission Reductions, San Diego, Nov. 11-15, 2008. p. 114-1 to 114-4. Interpretive Summary: 1,3-dichloropropene (1,3-D) and chloropicrin (CP) are often used for soilborne pest control in strawberry production. However, their emissions raise high environmental concerns and great efforts are needed to minimize emission. In raised-bed strawberry field, tarping is an effective technique to control fumigant emissions. This research investigated 1,3-D and CP emissions in fields tarped with different plastic materials including standard polyethylene film (PE), virtually impermeable film (VIF), semi-impermeable film (SIF) over the beds, and PE plus water applications to furrows (PE/water). PE fields with or without water application to furrows had higher emissions than VIF and SIF fields. Fumigant concentrations under the VIF tarp were substantially higher than the other fields. These results suggest that VIF can reduce fumigant emission effectively and as well as improve fumigation efficacy by retaining fumigants under the tarp. Fumigant emissions from furrows were extremely low compared to from beds. Thereby, emission reduction efforts should focus on the performance of tarp placed over raised beds in drip-fumigated strawberry fields.
Technical Abstract: Plastic tarps are often used to reduce fumigant emissions in raised-bed strawberry fields. In September 2007 near Oxnard, CA, a field study was conducted to determine the emission reductions under four tarp treatments: standard polyethylene (PE), virtually impermeable film (VIF), semi-impermeable film (SIF), and PE tarp on the beds with water application to furrows following fumigation (PE/Water). InLine [60.8% 1,3-dichloropropene (1,3-D) and 33.3% chloropicrin (CP)] was drip-applied 3 cm under the soil surface. Following the application, emissions of 1,3-D and CP from top of the beds and furrows were measured using dynamic flux chambers. Fumigant gas-phase concentrations under the tarp were also determined over time. Emission flux was highest immediately following the fumigant application which took ~3.5 h and the emission rate decreased significantly with time. PE tarped fields had 30-40% higher emission fluxes and cumulative emission losses than VIF and SIF tarped fields. Emissions were primarily from the raised beds for all four treatments. Fumigant concentrations under the VIF tarp were substantially higher than the PE and SIF tarped fields throughout the trial. Similar fumigant concentrations were determined under the PE tarp and SIF tarp. The results indicate that VIF can significantly reduce fumigant emissions while retaining higher fumigant concentration in the soil that can benefit fumigation efficacy. Emissions from furrows were extremely low (<1% of from beds). The bed designs of the tested fields represented most currently used in growers’ strawberry fields in the west coastal area of California. This research confirmed that emission reductions efforts need to focus on the performance of tarps placed on the beds.