Technical Abstract: The current study was conducted to test the hypothesis that microbial-based inoculants known to promote root growth and nutrient uptake will reduce emission of nitrous oxide in the presents of nitrogen fertilizers under controlled condition. The microbial based treatments were SoilBuilder (SB), a metabolite extract of SoilBuilder (SBF), and a mixture of four strains of plant growth-promoting Bacillus spp. Experiments included two different N fertilizers: urea, and urea ammonium nitrate 32% N (UAN) and a no-fertilizer control. Measurement of N2O and CO2 were determine from the soil incubations and analyzed with gas chromatography. After 29 days of incubation, cumulative emissions of N2O were reduced 80% SB and 44% SBF in soils fertilized with UAN. Treatment with Bacillus significantly reduces nitrous oxide production at 1 and 2 days of incubation in soils fertilized with UAN. In the un-fertilized treatment, cumulative emissions of N2O with SBF were significantly reduced by 92% and emissions at 2, 4, and 8 days of incubation were significantly reduced by SB and Bacillus. Microbial-based treatments did not reduce N2O emissions associate with urea application. Microbial-based treatments increased CO2 emissions from soils fertilized with UAN, indicating a possible increase in microbial activity. Overall, the results demonstrated that microbial-based inoculates can reduce emissions of N2O associated with N fertilizer application, and the response varied with the type of microbial inoculant and fertilizer.