Methanogens in paddy rice soil

The population, methanogenic activities and dominant species of methanogenic bacteria in paddy rice soils under different conditions were studied. Application of fertilizer, especially organic manure and submergence with deep water increased the population and methanogenic activities of methanogenic bacteria in rice soils. No large differences was observed among the population of methanogen in rice soils from different depths of 0-5, 5-13 and 13-18 cm. Soils, which developed from different parent material and had various use history, had notably different cell numbers and activities of methanogenic bacteria. Methanogenic activities in soils developed from fluvo-aquic soil were obviously higher than those in soils developed from quaternary red soil and coastal saline soil, and those in upland soil were pronounced lower than those in rice soil. The methanogenic bacteria that survived in air-dried rice soil could form methane after addition of water and incubation. The dominant species of methanogens were Methanobacterium formicicum, Methanobrevibacter sp., Methanosarcina mazeii and Methanosarcina barkeri.