Minimizing Emissions From Soil Fumigation By Surface Seal Methods.

Authors: Gao, Suduan; Trout, Thomas

Submitted to: Proceedings of the International Conference on the Future of Agriculture: Science, Stewardship and Sustainability
Publication Type: Proceedings
Publication Acceptance Date: 6/1/2006
Publication Date: 8/7/2006
Citation: Gao, S., Trout, T.J. 2006. Minimizing Emissions From Soil Fumigation By Surface Seal Methods.. Proceedings of the International Conference on the Future of Agriculture: Science, Stewardship and Sustainability. Proceedings for the International Conference on the Future of Agriculture: Sscience, Stewardship, and

Interpretive Summary: Soil fumigation is widely used to control soil pests and achieve high yields of many fruit, vegetable, and nursery crops. The increasing use of alternative fumigants to methyl bromide including Telone (1,3-dichloropropene or 1,3-D) products causes environmental concerns because they are volatile organic compounds (VOCs) and once released to the atmosphere react with nitrogen oxides under the sunlight to form harmful ground level ozone. The standard high density polyethylene (HDPE) tarp is not effective to control emissions of 1,3-D. In the last two years, we have conducted a series of soil column tests and two field trials and investigated the potential of water seals (water application to the soil surface by sprinklers) as a cost-effective method to reduce 1,3-D and chloropicrin emissions. Our research has demonstrated that water seals can be more effective to reduce 1,3-D emissions than HDPE tarp. This effectiveness was illustrated from sprinkler irrigation to the soil surface following fumigation as well as prior to fumigation and also from water applications with shank-injection as well as drip-application. Water seals can clearly reduce emission peaks and delay emission times thus reducing the risks to workers and by-standers during fumigation. Water seals cost substantially less than HDPE tarp and also there is no required material disposal. Practices involved with irrigation to the soil surface can be developed for field applications. The research also revealed that drip-application resulted in lower emissions than shank-injections. However, excessive water in soil can affect fumigant diffusion thus efficacy. Further research is needed to clearly define the optimum soil water content for different soil types for minimizing emissions while achieving adequate pest control.

Technical Abstract: Soil fumigation is an important management practice for controlling soil pests in many high value crops. Reducing atmospheric emissions can minimize the impact of soil fumigation on the environment. Water seals (sprinkling water on the soil surface) to reduce fumigant emissions is more cost-effective than plastic tarps. We have conducted a series of soil column tests and two small-plot field trials to determine the effectiveness of pre-irrigation and water seals following fumigation on reducing emissions of 1,3-dichloropropene (1,3-D) and chloropicrin (CP) in comparison with tarps (standard high density polyethylene, HDPE; and virtually impermeable film, VIF) in a sandy loam soil in the San Joaquin Valley, CA. Water application immediately following shank-injection of the fumigants reduced and delayed emission peaks. Intermittent water applications were more effective to reduce emission peaks and total emissions compared to single applications. Irrigation prior to shank-injected fumigation also effectively reduced emissions. Water applications before and after drip-application of fumigants also showed effectiveness to reduce emissions. Results consistently show that water applications to the soil surface can reduce emissions more effectively than HDPE tarp, especially for 1,3-D. An appropriate amount of water and application schedule, however, needs to be determined for different types of soil to ensure adequate fumigation efficacy while reducing emissions.