Low Permeability Tarps to Reduce Emission and Improve Fumigant Distribution in Soil From Deep Shank Injection of Telone C35.

The San Joaquin Valley (SJV) of California is a highly productive region for perennial crops such as tree fruits, tree nuts and grapes. Preplant soil fumigation is often used in replanted orchards to control soil-borne pests which can increase establishment success and long-term orchard productivity. Air quality issues (ground-level ozone) in the SJV have focused development of techniques to reduce fumigant emissions from soil. Techniques that more effectively contain fumigants or improve fumigant distribution in soil have been suggested as means to increase efficacy with reduced fumigant rates.  In fall 2011, a field trial was conducted in a sandy loam soil to evaluate three rates of nitrogen-pressurized or carbonated Telone C35 (1,3-dichloropropene plus chloropicrin) shank-injected to 45 cm depth and sealed with polyethylene (PE) or totally impermeable film (TIF). Emission data showed that TIF reduced emissions >95% relative to bare soil, a significant improvement over the ~30% emission reduction by PE. TIF also increased fumigant concentration or concentration-time (CT) exposure indices at 15 cm depth compared to the PE film. Improvement on fumigant distribution in soil by carbonation is inconclusive and more field tests are needed. Correlations between efficacy data (nematode, pathogen, and weed) and fumigant CT index will be examined. This research continues to develop management strategies to maximize fumigant efficiency while reducing negative environmental impacts.