Hyun Young Hwang

Beneficial effect of compost utilization on reducing greenhouse gas emissions in a rice cultivation system through the overall management chain

Livestock manure application can stimulate greenhouse gas (GHG) emissions, especially methane (CH4) in rice paddy. The stabilized organic matter (OM) is recommended to suppress CH4 emission without counting the additional GHG emission during the composting process. To evaluate the effect of compost utilization on the net global warming potential (GWP) of a rice cropping system, the fluxes of GHGs from composting to land application were calculated by a life cycle assessment (LCA) method. The model framework was composed of GHG fluxes from industrial activities and biogenic GHG fluxes from the composting and rice cultivation processes. Fresh manure emitted 30MgCO2-eq.ha-1, 90% and 10% of which were contributed by CH4 and nitrous oxide (N2O) fluxes, respectively, during rice cultivation. Compost utilization decreased net GWP by 25% over that of the fresh manure during the whole process. The composting process increased the GWP of the industrial processes by 35%, but the 60% reduction in CH4 emissions from the rice paddy mainly influenced the reduction of GWP during the overall process. Therefore, compost application could be a good management strategy to reduce GHG emissions from rice paddy systems.

Effective Suppression of Methane Production by Chelating Nickel of Methanogenesis Cofactor in Flooded Soil Conditions

Abstract BACKGROUND: Methane(CH 4 ) is considered as the secondmost potent greenhouse gas after carbon dioxide (CO 2 ). Methanogenesis is an enzyme-mediated multi-step process by methanogens. In the penultimate step, methylated Co-M is reduced by methyl Co-M reductase (MCR) to CH 4 involving a nickel-containing cofactor F430. The activity of MCR enzyme is dependent on the F430 and therefore, the bioavailability of Ni to methanogens is expected to influence MCR activity and CH 4 production in soil. In this study, different doses of EDTA(Ethylene Diamine Tetraacetic Acid) were applied in flooded soils to evaluate their suppression effect on methane production by chelating Ni of methanogenesis cofactor.METHODS AND RESULTS: EDTA was selected as chelating agents and added into wetland and rice paddy soil at the rates of 0, 25, 50, 75, and 100 mmol kg -1 before 4-weeks incubation test. During the incubation, cumulative CH 4 production patterns were characterized. At the end of the experiment, soil samples were removed from their jars to analyze total soil Ni and water-soluble Ni content and methanogen abundance. Methane production from 100 mmol application decreased by 55 and 78% in both soils compared to that from 0 mmol. With increasing application rate of EDTA in both soils, water-soluble Ni concentration significantly increased, but total soil Ni and methanogen activities showed negative relationship during incubation test.CONCLUSION: The decrease in methane production with EDTA application was caused by chelating Ni of coenzyme F430 and inhibiting methanogenesis by methyl coenzyme M reductase. Consequently, EDTA application decreased uptake of Ni into methanogen, subsequently inhibited Research Article Open Access

Importance of Harvesting Time of Winter Cover Crop Rye as Green Manure on Controlling CH4 Production in Paddy Soil Condition

Winter cover crop cultivation provides high amount of organic matter when applied as green manure in paddy soils but can adversely increase methane (CH4) production during rice cultivation. Main organic components (cellulose, hemicellulose, lignin,) concentrations of cover crops may vary according to the different harvesting dates and might affect differently CH4 production in the paddy soil when applied as green manure. In this study, aboveground biomass of rye (Secale cereale L.) was harvested over a week interval for 9 weeks (April 23 to June 19) and then mixed with dried paddy soil with the rate of 5 Mg ha−1 on dry-weight base for incubation test. The concentration of total C, cellulose, and lignin of rye biomass was steadily increased with crop maturing, but total N and labile C concentrations were reversely decreased. Methane production activity has very high positive correlation with labile C (water-soluble C, hot-water-extractable C) concentration of rye biomass but negative correlation with C/N ratio, total C, and lignin concentrations. Therefore, CH4 production activity was higher in soils treated with early-harvested rye to that of the late-harvested rye treatment. Rye that was harvested on the 2nd–3rd week after the 1st harvesting date had slightly lower labile C but very high amount of total N, which could be the optimum harvesting period to regulate CH4 production without compromising its ability to provide added N supply when used as green manure in paddy soil. Conclusively, selection of the optimum period of rye harvesting is considerable to regulate CH4 production and improve soil fertility during green manure application in paddy soils.