In this study, the soils with or without earthworms (Eisenia fetida) were treated with one of the two following nitrification inhibitors (NIs): dicyandiamide (DCD) or 3,4-dimethylpyrazole phosphate (DMPP); then, the soils were incubated for 90 days in laboratory mesocosms. The cumulative nitrous oxide (N 2 O) emission increased from 74.08 μg N 2 O-N kg −1 in the control to 384.69 μg N 2 O-N kg −1 in the earthworm-treated soil. The addition of NI decreased the cumulative N 2 O emissions from soils by 67.1 % in the DCD treatment and 73.4 % in the DMPP treatment without earthworms and by 79.0 and 81.0 % with earthworms, respectively. After 90 days, the richness of nirK gene in the soil decreased in both DCD and DMPP treatments compared with control, and the abundance of denitrifying bacteria in the gut of earthworm declined to less than 1/1000 or 1/100 of those without NIs. At 7 and 90 days, N 2 O production by denitrification in earthworm gut homogenates in both NI treatments decreased compared to those without NIs. Therefore, this study provided a fundamental evidence for that the application of NImitigated N 2 O emission induced by earthworm (E. fetida).

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