LABORATORY-SCALE MEASUREMENTS AND SIMULATIONS OF EFFECT OF APPLICATION METHODS ON SOIL METHYL-BROMIDE EMISSION

Methyl bromide (bromomethane, MeBr), which originates from the oceans, fumigation, and a few other sources, is reportedly contributing to th e ozone depletion in the stratosphere. Due to the heavy reliance on th is fumigant in the production of many crops, it is of particular impor tance to accurately quantify the atmospheric input of MeBr arising fro m agricultural uses, and develop feasible measures to minimize these e missions. In this study, we determined the effect of two important app lication variables, surface tarp and injection depth, on MeBr transpor t and transformation in the soil and its emission from the soil surfac e under controlled conditions. Following 20- and 30-cm injections, cov ering the soil surface with 1-mil (0.025 mm) high-density polyethylene film resulted in an average of 48% reduction in MeBr emission. Increa sing the injection depth from 20 to 60 cm caused a decrease in MeBr em ission of 54% under untarped conditions and 40% under tarped condition s. The influence of application methods on MeBr atmospheric emissions should be considered when estimating the contribution of agricultural fumigation to the overall atmospheric MeBr burden on a global scale. T he results also indicate that MeBr emission after soil fumigation may be substantially minimized by using surface tarpaulins and deep inject ions.