BACKGROUND: Emission of nitrous oxide (N₂O) from the soil is expected to depend on the types of nitrogen fertilizer used. Biochar has recently been proposed as a potential mitigation of climate change by reducing the N₂O emission. Although laboratory studies reported that biochar applications could reduce N₂O emission, the number of field-based studies is still limited. Therefore, a field experiment was conducted to investigate the effect of biochar on N₂O emission when different nitrogen fertilizers were applied in corn cultivated field. METHODS AND RESULTS: The field experiment consisted of six treatments: urea fertilizer without biochar (U), ammonium sulfate fertilizer without biochar (A), oil cake fertilizer without biochar (O), urea fertilizer with biochar (U+B), ammonium sulfate fertilizer with biochar (A+B), and oil cake fertilizer with biochar (O+B). Biochar was applied at a rate of 10 t/ha. Greenhouse gas fluxes were measured during growing seasons using static vented chambers. The cumulative N₂O emissions were 0.99 kg/ha in the U, 1.23 kg/ha in the A, 3.25 kg/ha in the O, 1.19 kg/ha in the U+B, 0.86 kg/ha in the A+B, and 1.55 kg/ha in the O+B. CONCLUSION: It was found that N₂O emission was related to application of both nitrogen fertilizer type and biochar. In particular, the N₂O reduction effect was the highest in the corn field incorporated with biochar when oil cake was applied to the soil.