Effect of Soil Moisture On Fumigant Emissions From a Loam Soil.

Emissions of soil fumigants must be minimized in order to protect air quality in California. Soil moisture is an important factor that can be managed at a relatively low cost prior to soil fumigation to reduce emissions. A previous study indicated that increasing soil water content up to field capacity reduced emissions from a sandy loam soil. Due to smaller pore size, this effect is likely to be more pronounced in fine textured soils. The objective of this study was to determine the effects of soil water content from 30 to 100% field capacity on the emission and distribution of the fumigants 1,3-dichloropropene (1,3-D) and chloropicrin (CP) in columns packed with a loam soil. After injecting equal amounts of cis-1,3-D, trans-1,3-D, and CP, emission and gaseous fumigant distribution in the columns was monitored for 12 days. With similar response to soil water content, the emission of the three compounds followed an order as cis-1,3-D > trans-1,3-D > CP. Increasing soil water content significantly reduced emission peak flux and delayed its occurrence. This effect is more significant than from the previously tested sandy loam soil. Corresponding lower cumulative emissions were measured from treatments with higher soil water content. Furthermore, higher gaseous fumigant concentrations were found in high soil water content treatments reflecting the ability of soil moisture to reduce fumigant transport to the soil surface.