Technical Abstract: The study was conducted on two soils to: i) compare nitrous oxide (N2O), carbon dioxide (CO2) and methane (CH4) fluxes from swine slurry and fertilizer nitrogen (N), ii) determine N loses through N2O emission, and iii) assess global warming potential (GWP) of treatments. The soils used were loamy sand and clay which had 790 and 216 g kg-1 of sand and 10.6 and 26.5 cmolc kg-1 of cation exchange capacity (CEC), respectively. The pots, containing 12 kg of soil without vegetation, were incubated for 8 weeks. The treatments were: i) control (no N), ii) fertilizer N as a urea-ammonium nitrate (UAN) solution, and iii) swine slurry, injected at the 5 cm depth at the rate of 200 kg N ha-1. Cumulative emissions of N2O, CO2 and CH4 were higher from sand than from clay. Fertilizer N and swine slurry enhanced N2O emission on the sand with no difference between N sources. For the clay, the N2O emissions ranked slurry > fertilizer N > control. Enhanced CO2 and CH4 fluxes were observed from slurry in both soils. The N2O-N losses from fertilizer amounted to 3.3 and 0.2% from the sandy and clayey soils, respectively. The N2O-N losses from the slurry accounted for 2.7 and 1.8 % of applied N for sand and clay, respectively. N2O losses from the sand were higher than the Intergovernmental Panel on Climate Change (IPCC) emission factor of 1.25%. This study showed that sand with low CEC emitted more GHGs than clay with high CEC. The N2O production from fertilized N was the main source of GWP (59%) on sandy soil. The N2O emission from the slurry N largely contributed to GWP on sandy and clayey soils (41 and 36%, respectively).