Oxidation of methane and total water soluble organic carbon (TOC) in the subsoil, which percolated from the plow layer, was investigated in a column experiment. The amounts of both methane and TOC in the leachate decreased
by percolation in the subsoil. Fe ~§ percolated from the plow layer was nearly completely retained in the
subsoil. The decomposition of methane and TOC in the subsoil was considered to result in the coupling with the formation of Fe 2+. Methane was estimated to contribute ca. 19-21~o to the total amount of Fe 2§ formed in the subsoil by the
organic materials in the leachate.