Tillage and land use effects on methane oxidation rates and their vertical profiles in soil

The effect of land use and different soil tillage systems on CH(4) oxidation was tested in a laboratory incubation study. Intact soil cores were collected from the topsoil (0-12 cm) of a field site with ploughed, direct-drilled and set-aside treatments. and from an adjacent undisturbed forest site. CH(4) oxidation rates were 4.5 to 11 times higher in the direct-drilled than in the continuously ploughed treatment, in the set-aside soil they were intermediate. The oxidation rates in the forest. soil were II times the highest rate measured at the field site, pointing to a distinct land use effect. Vertical profiles of CH(4) oxidation activity revealed a very clear zonation in all treatments. CH, oxidation increased significantly below the plough layer (0-25 cm), and showed a subsurface maximum under direct-drilling (5-15 cm) and under forest (5-10 cm). The vertical zonation under set-aside was comparable to that under ploughing. Generally, the maximum CH(4) oxidizing activity was in the zone nearest to the soil surface, unless various constraints prevented this.