Since MeI is not a registered pesticide, however, there is virtually no information regarding its environmental behavior in agricultural soils. With the impending cancellation of MeBr and previous cancellation of other soil fumigants, it has become imperative to find and adopt methods for reducing emissions so that the remaining soil fumigants do not suffer a similar fate. Also, any decision to use alternative fumigants should be weighed in terms of the probable environmental consequences and the associated economic implications, and should be compared with methyl bromide. There is a great need for more information on the soil chemical parameters which characterize the fate and transport of MeI. Since MeI has a similar chemical structure to MeBr, one would expect similar environmental behavior. We have recently started to obtain basic information on MeI transport.
Soil degradation is the transport parameter which is least known.
Recent experiments indicate that the degradation half life for MeBr is approximately 10 days in a Greenfield sandy loam. Preliminary studies suggest that the MeI half life is approximately 50 days in this soil. For a Linne clay loam soil with higher organic matter content, the half lives were 5 and 10 days, respectively, for MeBr and MeI. A longer half life for MeI would promote an increased residence time in soils. This may cause delays in planting, if the soil needs venting to reduce phyto toxicity, and would produce a greater total emission into the atmosphere compared to MeBr. Also, if irrigation follows fumigation, MeI's high water solubility and long residence time coupled to the reduced air filled pore space after irrigation, will increase the probability of ground water contamination.