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Effective Cover Crop and Water Management to Decrease Methane Emission and Sustain Soil Organic Carbon Stock in Rice Paddy 원문보기

  • 저자

    모하마드모자멜하끄

  • 학위수여기관

    경상대학교 대학원

  • 학위구분

    국내박사

  • 학과

    응용생명과학부

  • 지도교수

  • 발행년도

    2014

  • 총페이지

    p.18, p.119

  • 키워드

    CH4 CO2 N2O emission Water management Winter cover crop biomass Rice paddy soil Carbon balance Global warming potential;

  • 언어

    eng

  • 원문 URL

    http://www.riss.kr/link?id=T13534187&outLink=K  

  • 초록

    Rice paddy soil is regarded as an important source of methane emission. However, mono rice paddy soil in the temperature zone is flooded less than 100 days a year and then it could be methane emission source for only this season. However, paddy soil is maintained under the dried upland soil condition over 200 days a year. Therefore, a certain level of methane might be oxidized in this period, but its potential was not evaluated still. In this study, (1) it could be a CH4 sink during fallow season, and it might be significantly increased by high level of cover crop biomass amendment. In order to make the management strategy of rice paddy soil which can effectively reduce CH4 emission budget, CH4 balance which means the difference between CH4 production and consumption should be analyzed during the flooded and dried paddy soil condition. (2) Cover crop cultivation during the fallow season can increase CH4 oxidation potentials. However, its biomass is mostly removed for producing livestock forage in Korean paddy soil, and then it might result in declining soil organic matter level and deteriorating soil quality in a long-term base. Therefore, the methodology which can evaluate the carbon balance should be developed to sustain soil organic matter level and maximize biomass production. (3) However, cover crop biomass recycling to sustain soil organic matter level but this can significantly increase greenhouse gas CH4 emission. Therefore, agricultural practices which can decrease effectively CH4 emission during rice cultivation should be developed. Water management (intermittent drainage) is regarded as a key soil management to reduce CH4 emission and global warming potential during rice cultivation. A. Contribution of greenhouse gas emissions during cropping and fallow seasons on total global warming potential in a mono-rice paddy soil The influence of cover crop cultivation and incorporation as a green manure on greenhouse gas emission and GWP were evaluated for a whole year period. Results indicated that NPK treatment, the annual GWP value was 14.2-16.0 Mg ha-1, in which around 51-60% was affected by the seasonal GWP value during the fallow season. Cover crop cultivation during the fallow season and its biomass addition as a green manure for rice cultivation significantly increased total GWP value to 60.5-60.7 Mg ha-1, in which about 79-81% was weighted by the seasonal GWP value during rice cultivation, mainly due to significant increase in CH4 and CO2 emissions. Carbon dioxide was the most influential GHG on increasing the growth scale of total GWP during the dried fallow season, but CH4 influenced most strongly total GWP scale during the rice cropping season, irrespective with soil management condition. The contribution of CH4 to the annual GWP value was significantly increased by cover crops biomass addition from 25-30% in NPK to 58-60% in NPK+Cover crop biomass. In conclusion, dried fallow season contributed to around 20-60% of total GWP scale by the GHG emissions. Therefore, proper soil management strategy should be developed to decrease GHG emission during the fallow and rice season in mono-rice paddy fields. B. Estimation of Optimum Recycling Ratio of Cover Crop Biomass as a Green Manure using Soil Carbon Balances in Rice Paddy The optimum recycling rates of cover crop biomass which can sustain soil organic C stock and maximize biomass removal for other industrial purposes were estimated through carbon balance approach. Applied organic carbon was lost mainly by mineralization (80-87% of the organic carbon output) through CH4 and CO2 losses, but leaching and erosion organic carbon losses were comparatively small. However, seasonal CH4-C and CO2-C fluxes proportionally and significantly increased with increasing biomass recycling ratios during rice cultivation. The negative SOC balance which implies that the soil fertility is at risk from a decreasing SOC stock was observed in total above ground biomass removal. Soil OC balance significantly increased with increasing biomass recycling level and then met the zero value at around 16-20% of biomass recycling, indicating that the present SOC level could be sustained. Therefore, more than 20% of cover crop biomass (7-9 Mg ha-1 on fresh weight) should be recycled as a green manure to sustain SOC level in mono-rice cultivation system under chemical fertilization. C. Effect of Intermittent drainage on suppressing CH4 emission and Global warming potential under cover crop biomass amendment during rice cultivation The suppressing potential of CH4 emission and GWP by intermittent drainage was evaluated under cover crop biomass applied condition. Methane, CO2 and N2O emission rates were significantly (p


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