METHANE PRODUCTION IN 2 INDIAN RICE SOILS

In a study on methane production from two rice soils (alluvial and aci d-sulfate) differing in physicochemical characteristics, methane produ ction in both soils was negligible under nonflooded conditions. Submer gence enhanced the production of methane in alluvial soil, especially upon its incubation after leaching. However, methane production was no t extensive in organic-matter-rich, acid-sulfate (Pokkali) soil even u nder submergence and despite favorable conditions of near neutral pH a nd low redox potential. Addition of calcium sulfate or leachate from a cid-sulfate soil inhibited the production of methane in flooded alluvi al soil. Addition of molybdate, a known inhibitor of sulfate-reducing bacteria, marginally enhanced the production of methane in acid-sulfat e soil but retarded it in alluvial soil. The findings suggest the invo lvement of not only sulfide but also other factors such as salinity in inhibiting methane production in acid-sulfate soil.