Methane production in two Indian rice soils

In a study on methane production from two rice soils (alluvial and acid‐sulfate) differing in physicochemical characteristics, methane production in both soils was negligible under nonflooded conditions. Submergence enhanced the production of methane in alluvial soil, especially upon its incubation after leaching. However, methane production was not extensive in organic‐matter‐rich, acid‐sulfate (Pokkali) soil even under submergence and despite favorable conditions of near neutral pH and low redox potential. Addition of calcium sulfate or leachate from acid‐sulfate soil inhibited the production of methane in flooded alluvial soil. Addition of molybdate, a known inhibitor of sulfate‐reducing bacteria, marginally enhanced the production of methane in acid‐sulfate soil but retarded it in alluvial soil. The findings suggest the involvement of not only sulfide but also other factors such as salinity in inhibiting methane production in acid‐sulfate soil.