Effect of Phospho-gypsum on reduction of methane emission from rice paddy soil

Abstract

Phospho-gypsum, a primary waste by-product in phosphate fertilizer manufacturing industry and a potential source of electron acceptors, such as mainly of sulfate and a trace amount of iron and manganese oxides, was selected as soil amendment for reducing methane (CH4) emissions during rice cultiva- tion. The selected amendment was added 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 plant was measured along with soil Eh and floodwater pH during the rice cultivation period. CH4 emission rates measured by closed chamber method decreased with increasing levels of phospho-gypsum application, but rice yield markedly increased up to 10 Mg ha -1 of the amendment. At this amendment level, total CH4 emissions were reduced by 24% along with 15% rice grain yield increment over the control. The decrease in total CH4 emission may be attributed due to shifting of electron flow from methanogenesis to sulfate reduction under anaerobic soil conditions.