The influences of chemical fertilizers and a nitrification inhibitor on greenhouse gas fluxes (N(2)O and CH(4)) in a corn field in Indonesia were investigated using a closed chamber. Plots received 45+45 kg-N ha(-1) of nitrogen fertilizer by split applications of urea, a single application of controlled-release fertilizer (CRF-LP30) or urea+dicyandiamide (DCD; a nitrification inhibitor), and no nitrogen application (control). Cumulative amounts of N(2)O emitted from the field were 1.87, 1.70, 1.06, and 0.42 kg N(2)O-N ha(-1) season(-1) for the urea, CRF-LP30, urea+DCD, and control plots, respectively. The application of urea+DCD reduced the emission of N(2)O by 55.8% compared with urea. On the other hand, the soil acted as a sink for CH(4) in the CRL-LP30, control, and urea+DCD plots with value of -0.09, -0.06 and -0.06 kg CH(4)-C ha(-1) season(-1), respectively. When the viability of AOB (ammonia-oxidizing bacteria) and NOB (nitrite-oxidizing bacteria) were monitored, AOB numbers were correlated with the N(2)O emission. These results suggest that 1) there is a potential for reducing emissions of N(2)O by applying DCD, and 2) corn fields treated with CRF or urea+DCD can act as a sink for CH(4) in a tropical humid climate.