Emissions of 1,3-Dichloropropene and Chloropicrin after Shank Fumigation Under Field Conditions.

Soil fumigation is an important agronomic practice in the production of many high-value crops.  The use of soil fumigants can lead to unwanted atmospheric emissions and information is needed for developing best management practices that protect human and ecosystem health.  A large-scale field experiment was conducted to obtain emission rates for two commonly-used fumigants, 1,3-dichloropropene (1,3-D) and chloropicrin.  Over the course of the experiment, the daily peak volatilization rates ranged from 12 – 30 μg m^-2 s^-1 for 1,3-D and 0.7 – 2.6 μg m^-2 s^-1 for chloropicrin. Total emissions of 1,3-D and chloropicrin, respectively, were approximately 16 – 35% of the total 1,3-D and 0.3 – 1.3% of the total chloropicrin applied.  A soil incubation study showed that the low chloropicrin volatilization rates were due to high soil degradation rates at this field site.  To further verify this observation, a mathematical model was used to predict total emissions as a function of soil properties, injection depth, shank fracture, soil degradation, and surface resistance to volatilization.  It was found that the low chloropicrin emission rate could be attributed to soil degradation (i.e., t_1/2 = 2.9 h), with the model predicting total chloropicrin emissions less than 1%.