Suwanwaree, P. and G.P. Robertson
Presented at the All Scientist Poster Reception (2006-05-09 )
Methane oxidation in soils is a small but significant sink of atmospheric methane; previous work has shown oxidation to be lower in agricultural than in native forest or prairie soils. We examined methane oxidation in two corn-corn-soybean-wheat cropping systems in southwest Michigan, one managed organically with compost and cover crop vs. one managed conventionally. Fluxes were measured once per month (non-growing season) or twice per month (growing season) with static chambers, and daily oxidation rates ranged from -20 to 17 µg CH4-C/m2/h (negative fluxes indicate methane production, which occurred in some soils following heavy rainfall.) Overall we found little difference in overall oxidation rates between the two management systems. Rates of methane uptake varied somewhat by crop but only in organic cropping systems. Uptake rates were highest during the end of summer for both rotations, except during the transition of organic wheat into red clover. Average uptake was lowest in organic soybeans and organic wheat. Seasonal differences in oxidation rates may be related to differences in soil nitrogen availability.
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