Abstract
Methane (CH_4) emission from flooded paddy soils to the atmosphere through rice plant was suppressed to 58-2% of control by percolation at the rate of 1 liter/2 weeks (26 mm of water column/week). Dissolved gases in he leachate were composed mainly of CO_2, being larger in the early and late stage of flooding. Dissolved CH_4 increased in the middle stage and decreased by interruption of flooding in the late stage. Both dissolved CO_2 and CH_4 increased by amendment of rice straw. Organic acids such as acetic and propionic were found sometimes in the leachate, but the amounts were small in comparison with dissolved CO_2 and CH_4. Dissolved O_2 and nitrate in the leachate decreased quickly to negligible amounts. Effect of percolation was not markedly found on soil Eh (5 cm). Mechanism of suppression to CH_4 emission by percolation was, probably, mainly due to removing dissolved CO_2 in the leachate.
