|Spokas, Kurt - UNIV OF MINNESOTA|
|Wang, Dong - UNIV OF MINNESOTA|
Submitted to: Journal of Soil Biology and Biochemistry
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: August 21, 2004
Publication Date: March 3, 2005
Citation: Spokas, K., Wang, D., Venterea, R.T. 2005. Greenhouse gas production and emission from a forest nursery soil: Effects of fumigation with chloropicrin and methyl isothiocyanate. Journal of Soil Biology and Biochemistry. 37:475-485. Interpretive Summary: Agricultural pesticides that are applied in gaseous form may subsequently escape to the atmosphere and have various environmental impacts. Several of these so-called 'fumigants' are currently being evaluated as replacements for methyl bromide (MeBr), which has been slated to be phased out due to it's potential role in stratospheric ozone depletion. The current study examined the effect of two potential MeBr alternative fumigants on the production and emission of greenhouse gases from soil to the atmosphere. The effects of chloropicrin (CP) and methyl isothiocyanate (MITC) on emissions of methane (CH4), nitrous oxide (N2O), and carbon dioxide (CO2) were examined in a forest nursery soil. Following field fumigation, emissions of CH4 and CO2 were unaffected. However, both fumigants increased N2O emissions rates significantly compared to non-fumigated controls. Production of N2O was also stimulated by CP in aerobic laboratory incubation studies. The current findings suggest that these particular MeBr alternatives, while potentially mitigating impacts on stratospheric ozone depletion, may have other important consequences. The potential of these fumigants for causing increases in emissions of N2O, which is a very potent greenhouse gas, may need to be considered by policy-makers and scientists in their evaluation of MeBr alternatives.
Technical Abstract: 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 rates 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 in both treatments 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.