Methane production and its fate in paddy fields IV. sources of microorganisms and substrates responsible for anaerobic methane oxidation in subsoil

Abstract

A percolation experiment was conducted using soil columns to analyze the sources of microorganisms and organic materials responsible for anaerobic CR4oxidation in the subsoil of rice paddies. A glass column packed with plow layer soil and rice straw was connected to a column with sterilized or heated (550°C, 12 h) subsoil. Leachate was periodically collected from the bottom of the subsoil and analyzed for the contents of CR4, ferrous iron, and carbon in the water soluble organic materials (TOC). Methane concentration in the leachate decreased by percolation into the subsoil. Sterilization and removal of organic materials from the subsoil did not affected appreciably the CH4content in the leachate from the subsoil column. Sterilization of the subsoil enhanced the leaching of TOC and ferrous iron from the subsoil and production of ferrous iron in the subsoil. Removal of organic materials from the subsoil decreased ferrous iron production in the subsoil. These observations suggested that CR4was oxidized in the subsoil by microorganisms which were leached from the plow layer soil. Methane-oxidizing microorganism(s) appeared to use organic materials which were also leached from the plow layer soil. Microorganisms and organic materials in the subsoil contributed to ferric iron reduction but not to CR. oxidation. © Taylor & Francis Group, LLC.