Abstract
Changes in methanogenic activity were determined in slurries of soil collected from a paddy field. Acetate or H2 added as a methanogenic substrate stimulated methane production in most samples. In soil collected when the field was continuously flooded, the two substrates affected production similarly, while in the samples collected when the field had been drained, H2 stimulated production more strongly than acetate. The effect of temperature on methane production in paddy soil was also investigated. In continuously flooded soil, the temperature optimum for production was 40°C, however, this shifted to 45°C during a period of intermittent irrigation accompanied by a marked decrease in activity. The temperature optimum during the non-cropping season was also 45°C. It was suggested that the dominant methanogens in the drained paddy field are H2-utilizers, different from the dominant groups in flooded paddy soil.
