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[B-2.4.2 Emission of Trace Gases Contributing Greenhouse Effect from Grassland]

[Contact Person]

Katsumi Yamamoto
Section Director, Department of Environment
National Grassland Research Institute
Ministry of Agriculture, Forestry & Fisheries
768 Senbonmatsu, Nishinasuno, Tochigi 329-27 Japan
Phone +81-287-36-0111(Ext.304), Fax +81-287-36-6629

[Total Budget for FY1990-1994]

15,199,000 Yen (FY1994 3,372,000 Yen)

[Abstract]

　We measured the fluxes of for methane(CH₄) and nitrous oxide(N₂O) in grassland in relation to fertilization and influences of animal excreta. Grassland showed the function as a sink for atmospheric CH₄, and N₂O emission through the year. The fluxes of CH₄ uptake and N₂O emission were calculated for forest-floor, unfertilized and fertilized grasslands as 449.5, 106.8 and 100.0 CH₄-C mg/m²/yr, 45.9, 47.4 and 190.1 N₂O-N mg/m²/yr, respectively. Surface application of cattle slurry or fresh feces to grassland resulted remarkable emission of CH₄ and N₂O. The emission of CH₄ decreased remarkably by injecting. Cattle slurry into the soil(about 15cm of depth) with nitrification inhibitor (thiourea, at rate of 0.5% slurry-N) restrained release of CH₄ and N₂O remarkably. However, the N₂O emission was still larger than the case of cattle slurry applied to the surface soil without the nitrification inhibitor.
　Then, we estimated of the size of source or sink for CH₄ and N₂O of grassland in the world and Japan. The uptakes of atmosphere CH₄ by grassland were estimated as 3,586 and 0.8 CH₄-C Gg/yr in the World and Japan, respectrvely. The amounts of N₂O emission from grassland were estimated as 1,979 and 1.2 N₂O-N Gg/yr in the world and Japan, respectively. Additional emissions of N₂O and CH₄ from livestock manure that reduced to grassland were estimated as 189 N₂O-N Gg/yr and 1,626 CH₄-C Gg/yr in the World, 14 N₂O-N Mg/yr and 116 CH₄-C Mg/yr in Japan, respectively.

[Key Words]

Grassland, Nitrous Oxide, Methane, Greenhouse Gas, Animal Excreta