Evaluation of fumigation and surface seal methods on fumigant emissions in an orchard replant field.

Soil fumigation is an important management practice for controlling soil pests and enabling successful replanting of orchards. Reducing emissions is required to minimize the possible worker and bystander risk and the contribution of fumigants to the atmosphere as volatile organic compounds that lead to the formation of ground-level ozone. A field trial was conducted in a peach orchard replant field to investigate the effects of fumigation method (shank-injection vs. subsurface drip-application treatments) and surface treatments (water applications and plastic tarps) on emissions of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) from shank-injection of Telone C-35 and drip application of InLine. Treatments included control (no water or soil surface treatment); standard high-density polyethylene (HDPE) tarp, virtually impermeable film (VIF) tarp, and pre-irrigation, all over shank injection; and HDPE tarp over and irrigation with micro-sprinklers before and after the drip application. The highest 1,3-D and CP emission losses over a 2-wk monitoring period were from the control (36% 1,3-D and 30% CP) and HDPE tarp (43% 1,3-D and 17% CP) over shank injection. The pre-irrigation 4 d before fumigation and VIF tarp over shank injection had similar total emission losses (19% 1,3-D and 8-9% CP). The HDPE tarp and irrigations over subsurface drip-application treatments resulted in similar and the lowest emission losses (12-13% 1,3-D, and 2-3% CP). Lower fumigant concentrations in the soil-gas phase were observed with drip-application than in the shank-injection treatments; however, all treatments provided 100% kill to citrus nematodes in bags buried from 30 to 90 cm depth. Pre-irrigation and drip application seem to be effective to minimize emissions of 1,3-D and CP.