Intensive use of mineral N fertilizers and organic amendments has resulted in higher N 2O emissions. A growing worldwide concern for these problems has motivated researchers, environmentalists, and policy makers to find alternatives to overcome such losses. Biological nitrogen fixation is one of many natural biological approaches to minimize the use of fertilizers and to possibly reduce N 2O emissions. A greenhouse study was performed by growing inoculated and noninoculated soybean seeds ( Glycine max (L.) Merr.) in PVC columns. The objective was to measure the contribution of Bradyrhizobium Japonicum and mineral-N fertilizer to promoting N 2O emission. A closed chamber technique was used for gas sampling. N 2O measurements were carried out shortly after nodulation. Bradyrhizobium Jopanicum induced N 2O cumulative (121.8 gkg -1) fluxes of inoculated seeds was significantly (alpha=0.05) higher than those of mineral N fertilized treatment (NIS) and the control (bare soil). Total nitrogen content of the roots and seeds was not affected by inoculation. Total carbon (42.10.1%), total nitrogen (3.10.1%), and crude protein (19.90.7%) contents of leaves of the inoculated seeds were significantly higher than those of noninoculated seed treatments. N 2O fluxes significantly increased with high dissolved organic carbon content (70.773.99 mg L -1) at R3 and at R8 stages when NO 3- (39.600.94 mg L -1) concentrations were high.
