Effect of chemical fertilizer and manure application on N2O emission from reed canary [Phalaris arundinacea] grassland in Hokkaido, Japan

We evaluated the effect of chemical fertilizer and manure applications on N 2 O emission from a managed grassland by establishing three treatment plots of chemical N fertilizer (chemical fertilizer), manure combined with chemical N fertilizer (manure) and no N fertilizer (control) at the Shizunai Experimental Livestock Farm in southern Hokkaido, Japan. The N 2 O fluxes from the soils were measured using a closed-chamber method from May 2005 to April 2008. Soil denitrifying enzyme activity (DEA) in the root-mat layer (0-2.5 cm) and in the mineral soil layer (2.5-5 cm) of each treatment plot was measured using an acetylene inhibition method after treatment with NO 3 − -N addition, glucose addition, both NO 3 − -N and glucose addition or neither NO 3 − -N nor glucose addition. Annual N 2 O emission ranged from 0.6 to 4.9 kg N 2 O-N ha −1 year −1 , with the highest emission observed in the manure plot and the lowest in the control plot. The chemical fertilizer induced emission factor (EF) (range: 0.85-1.32%) was significantly higher than the manure-induced EF (range: 0.35-0.85%). The denitrification potential of the soil horizons was measured with the addition of both NO 3 − -N and glucose, and was significantly higher in root-mat soil than in mineral soil. Soil DEA in the root mat with the addition of NO 3 − -N with and without the addition of glucose had a significantly positive correlation with soil pH (P