Conservation management systems are usually suggested as alternative to restore the soil methane (CH 4 ) 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 CH 4 fluxes in a formerly degraded Acrisol in Southern Brazil. Annual CH 4 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 CH 4 analysis. Analysis of the historical dataset at this experimental site indicated improvements in soil quality under the NT system, especially in legumebased cropping system (V/M) that exhibited the highest annual biomass input. CH 4 fluxes ranged from −42 ± 2 to 38 ± 16 µg C m -2 h -1 , and annual CH 4 emissions ranged from −825 ± 117 (CT V/M) to 453 ± 185 g C ha -1 (NT O/M). Thus, the annual CH 4 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. Key words: Global warming, tillage systems, tropical soils, cropping systems
ResumoSistemas conservacionistas de manejo de solo são considerados usualmente uma alternativa para restaurar a capacidade de solos agrícolas degradados em oxidar metano (CH 4 ), mas escassa informação é disponível para solos tropicais e subtropicais. O objetivo do presente estudo foi avaliar o efeito de longo prazo (19 anos) do plantio direto (PD) nos fluxos de CH 4 em um Argissolo Vermelho (Classificação Brasileira) degradado da região Sul do Brasil, em comparação ao preparo convencional (PC). Fluxos anuais de CH 4 do solo foram avaliados nos sistemas PD e PC sob dois sistemas de cultura (aveia/ milho-A/M e ervilhaca/milho-E/M). Amostragem do ar foi conduzida utilizando o método da câmara