New Trial to Suppress Methane Emission using the Precursor of Ethylene as a Methanogenic Inhibitor Under Rice Cropping Systems

다국어 초록 (Multilingual Abstract)

Ethylene which is a regulator of plant growth and ripeness is known to have the strong inhibition effect on methanogenesis. However, since ethylene is gaseous form and has very low water solubility, it has not been developed as soil amendment to suppress methanogenesis in flooded rice paddies. To develop ethylene as a prospective soil amendment for reducing methane (CH₄) emission in flooded soil conditions, ethephon (2-Chloroethylphosphonic acid), a precursor of ethylene, was selected, and its application effect on CH₄ production was compared with specific inhibitors (2-Bromoethanesulfonate, 2-Chlomoethanesulfonate, 2-Mercaptoethanesulfonate) of methanogenesis under flooded soil condition. The application of ethephon at a rate of 1mg kg<SUP>-1</SUP> significant decreased total CH₄ emission by 43% compared to the un amended control, and its suppression effect was comparable with the specific methanogenic inhibitors. However, most of ethephon was hydrolyzed into ethylene within 10 days of incubation. To slow down the release of ethylene from ethephon and enhance its effect on suppressing methanogenesis, ethephon was mixed with cellulose based biodegradable polymers [sodium carboxymethyl cellulose (CMC), methyl cellulose (MC), hydroxyethyl cellulose (HEC), and cellulose acetate CA)] (10% of ethephon). Polymer mixtures significantly retarded the hydrolysis of ethephon and increased suppression of CH₄ production. In comparison, CA and CMC were most effective with approximately 25% higher reduction of CH₄ emission than no-polymer mixed ethephon.To determine the effect of ethephon amendment in rice cultivation and CH₄ emission, ethephon was mixed with the selected biodegradable polymer (CA) and gypsum. Ethephon amendment retarded the hydrolysis of ethephon to 90 days. And the CH₄ emission was decreased as maximum 89% than the control. The rice growth and yield did not show significant changes. The abundance of mcrA gene was decreased by 28-47% in ethephon amendment treatments compared to the control. In conclusion, ethephon, a precursor of ethylene, can be used as an effective additive to suppress CH₄ emission in rice paddy soil.