Greenhouse gas production and emission from a forest nursery soil following fumigation with chloropicrin and methyl isothiocyanate

Soil fumigation is commonly used to control soil-borne pathogens and weeds. Our aim was to examine the effects of soil fumigation with chloropicrin (CP) and methyl isothiocyanate (MITC) on CH4, N2O and CO2 production and emission. These effects on a SE USA forest nursery soil were examined in field and laboratory experiments. Following field fumigation, CH4 surface emissions and concentrations in the soil atmosphere were unaffected. Both fumigants increased N2O emissions rates significantly compared to non-fumigated controls, and the effects were still evident after 48 d. These findings are in contrast to fertilizer-induced N2O emissions, which generally return to background within 2 wk after application. Depths of N2O production were different for the two fumigants as determined by soil gas sampling, suggesting fumigant-specific stimulation mechanisms. CO2 emissions (0-15 d) were not altered significantly, although sub-surface CO2 concentrations did increase following fumigation with CP or MITC and remained elevated for CP treatment on d 48. CP-induced N2O production was also stimulated in aerobic laboratory incubation studies, with surface soils exhibiting 10 to 100-fold greater production rates. MITC and a combination of CP/MITC also stimulated N2O production, but the effect was significantly less than for CP alone. MITC suppressed and CP did not effect CO2 production in the laboratory incubation. By comparing sterilized to non-sterile soils, >95% of these effects appear to be of biotic origin.