Soil methane oxidation in a long-term no-tillage system in Southern Brazil

Resumo

Conservation management systems are usually suggested as alternative to restore the soil methane (CH4) oxidation capacity of degraded soils; however, little information is available on tropical and subtropical soils. Our objective was to evaluate the long-term (19 years) effect of no-tillage (NT) versus conventional tillage (CT) management systems on CH4 fluxes in a formerly degraded Acrisol in Southern Brazil. Annual CH4 fluxes of two cropping systems [O/M-black oat (Avena strigosa)/maize and V/M-vetch (Vigna sativa)/maize] were measured in NT and CT soils. Static chambers were used for air sampling, while chromatography was used for CH4 analysis. Analysis of the historical dataset at this experimental site indicated improvements in soil quality under the NT system, especially in legume-based cropping system (V/M) that exhibited the highest annual biomass input. CH4 fluxes ranged from ?42 ± 2 to 38 ± 16 ?g C m-2 h-1, and annual CH4 emissions ranged from ?825 ± 117 (CT V/M) to 453 ± 185 g C ha-1 (NT O/M). Thus, the annual CH4 oxidation capacity of the soil was not related to the soil quality produced by the soil management systems. On the basis of our results and published literature, we postulate that conservation management systems improve the methane oxidation and soil quality in distinct soil layers, which result in a slow effect of these management systems on the methane oxidation capacity.