Effect of By-Product Gypsum Fertilizer on Methane Gas Emissions and Rice Productivity in Paddy Field

Rice cultivation in paddy field affects the global balance of methane (CH₄) as a key greenhouse gas. To evaluate a potential use of by-product gypsum fertilizer (BGF) in reducing CH₄ emission from paddy soil, CH₄ fluxes from a paddy soil applied with BGF different levels (0, 2, 4 and 8 Mg ha -1 ) were investigated by closed-chamber method during rice cultivation period. CH₄ flux significantly decreased (p -1 of BGF addition in soil reduced CH₄ flux by 60.6% compared to control. Decreased soil redox potential (Eh) resulted in increasing CH₄ emission through a CO₂ reduction reaction. The concentrations of dissolved calcium (Ca) and sulfate ion (SO₄ 2- ) in soil pore water were significantly increased as the application rate of BGF increased and showed negatively correlations with CH₄ flux. Decreased CH₄ flux with BGF application implied that SO₄ 2- ion led to decreases in electron availability for methanogen and precipitation reaction of Ca ion with inorganic carbon including carbonate and bicarbonate as a source of CH₄ formation under anoxic condition. BGF application also increased rice grain yield by 16% at 8 Mg ha -1 of BGF addition. Therefore, our results suggest that BGF application can be a good soil management practice to reduce CH₄ emission from paddy soil and to increase rice yield.