Impact of gypsum application on the methane emission from a wetland rice field

Methane emission from Philippine rice paddies was monitored with a closed chamber technique during the 1991 and 1992 wet season. The methane emission from plots amended with 6.66 tons.ha −1 gypsum was reduced by 55–70% compared to non‐amended plots. Although CH 4 emission from fields with a high input of fresh organic matter was strongly enhanced, the experiments showed that the relative reduction in CH 4 emission upon gypsum application was independent of organic matter addition. The reduced CH 4 emission upon gypsum application was most likely due to inhibition of methanogenesis by sulfate‐reducing bacteria. Observed SO 4 2− concentrations in the soil solution of gypsum‐amended plots were well above minimum concentrations reported in the literature for successful competition of sulfate‐reducing bacteria with methanogens. The data provide a base for reducing the estimates of CH 4 emissions from rice grown on high‐sulfate containing soils or gypsum‐amended soils.