Suppression of Methane Emission from Rice Paddy Soils with Fly ash Amendment

Abstract

Fly ash, a by-product of the coal-burning industry, and a potential source of ferro-alumino- silicate minerals, which contains high amount of ferric oxide and manganese oxide (electron acceptors), was selected as soil amendment for reducing methane (CH4) emission during rice cultivation. The fly ash was applied into potted soils at the rate of 0, 2, 10, and 20 Mg ha -1 before rice transplanting. CH4 flux from the potted soil with rice plants was measured along with soil Eh and floodwater pH during the cropping season. CH4 emission rates measured by closed chamber method decreased gradually with the increasing levels of fly ash applied, but rice yield significantly increased up to 10 Mg ha -1 application level of the amendment. At this amendment level, total seasonal CH4 emission was decreased by 20% along with 17% rice grain yield increment over the control. The decrease in total CH4 emission may be attributed due to suppression of CH4 production by the high content of active and free iron, and manganese oxides, which acted as oxidizing agents as well as electron acceptors. In conclusion, fly ash could be considered as a feasible soil amendment for reducing total seasonal CH4 emissions as well as maintaining higher grain yield potential under optimum soil nutrients balance condition.