Quantification of volatile compounds produced during simulated biofumigation utilizing Indian mustard degrading in soil under different environmental conditions

One of the main pesticides used for soil fumigation is methyl bromide, a broad spectrum soil fumigant. Methyl bromide was listed in the 1993 Montreal Protocol as an ozone-depleting compound. Because of this listing, the production of methyl bromide will be frozen at 1991 levels until importation and production are completely halted in the year 2005 (U.S. Clean Air Act). Biofumigation and solarization are strategies that could be inexpensive solutions to control soil pathogens, nematodes and weeds. The objective of this research was to quantify the amount and composition of all volatile compounds, including isothiocyanates (ITC), produced from degradation of two Indian mustards (Brassica juncea L.) in a simulated biofumigation strategy under different environmental conditions. The environmental variables studied were soil texture, soil temperature, soil moisture, soil pH, and autoclaved and non-autoclaved soil. Higher concentrations of ITC were detected in biofumigation at higher soil temperature and lower soil moisture. Higher concentrations were also detected in sandy loam textured soils and at lower soil pH. Autoclaved soil had higher ITC concentrations than non-autoclaved soil. Thus soil microbes are implicated in the degradation of ITCs. This information is important in developing a field plan for testing a biofumigation and/or solarization strategy that would meet the requirements of an effective and viable soil fumigant for growers.