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Evaluation of silicate iron slag amendment on reducing methane emission from flood water rice farming

Ali, Muhammad Aslam, Oh, Ju Hwan, Kim, Pil Joo
Agriculture, ecosystems & environment 2008 v.128 no.1-2 pp. 21-26
Oryza sativa, rice, methane, gas emissions, greenhouse gases, flood irrigation, soil amendments, silicate minerals, iron, ion transport, pollution control, redox reactions, fertilizer rates, mineral fertilizers, iron oxides, grain yield, plant growth, root systems, rhizosphere, soil air, South Korea
Application of electron acceptors such as ferric iron oxides and hydroxides for controlling methane (CH₄) emission from wetland rice fields deserves special attention due to its dominant role over all other redox species in wetland soils. Silicate iron slag (hereafter, silicate fertilizer), a byproduct of steel industry containing electron acceptors, was applied in paddy field (Agronomy Farm, Gyeongsang National University, South Korea) at the rate of 0, 1, 2 and 4Mgha⁻¹ to investigate their effects on reducing CH₄ emissions from flood water rice (Oryza sativa, cv. Dongjinbyeo) farming during 2006-2007. CH₄ emission rates measured by closed-chamber method decreased significantly (p <0.05) with increasing levels of silicate fertilizer application during rice cultivation. Soil redox potential (Eh) showed a contrasting response to CH₄ emission rates. The concentrations of dissolved iron materials in percolated water, and the active and free iron oxides in soil significantly increased with the applications of silicate fertilizer, which acted as oxidizing agents and electron acceptors, and eventually suppressed CH₄ emissions during the rice growing seasons. Total CH₄ emission was decreased by 16-20% with 4Mgha⁻¹ silicate fertilizer application and simultaneously rice grain yield was increased by 13-18%. Silicate fertilization significantly stimulated rice plant growth, especially root biomass, root volume and porosity, which might have improved rhizosphere oxygen concentration, and then partially contributed to reduce CH₄ emission through enhancing methane oxidation. Therefore, silicate fertilizer could be a good soil amendment for reducing CH₄ emission as well as increasing rice productivity in wetland paddy field.