Estimation of global warming potential from upland cropping systems in central Hokkaido(Soil Chemistry and Mineralogy)

概要

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Seven upland cropping systems in Central Hokkaido, Japan, were investigated during the growing season in 2003 to evaluate the magnitude of N_2O emission, CH_4 uptake and soil carbon sequestration, and their net effect on the global warming potential (GWP). N_2O and CH_4 fluxes were measured from field soils planted with crops and CO_2 fluxes were measured from bare soils in attached plots at each site using the closed chamber method. Cumulative N_2O emissions ranged from 0.02g N m^<-2> to 0.62g N m^<-2> for different soil types, which accounted for 0.35-4.44% of the applied fertilizer nitrogen. Cumulative CH_4 uptake rates ranged from -0.08g C m^<-2> to 0g C m^<-2>. Soil carbon sequestration, defined as the difference between the net primary production and carbon loss through harvest and soil microbial decomposition, ranged from -410 to -193g C m^<-2>, indicating that the carbon loss from soils could not be compensated by the carbon input through plant photosynthesis. The net GWP from the investigated cropping systems ranged from 749 to 1790 g CO_2 equivalents m^<-2>. CO_2 emission contributed to 84-99% of the net GWP and N_2O contributed 1-16%.