There are huge uncertainties (40%) associated with using the current Intergovernmental Panel on Climate Change (IPCC) Tier I emission factor for nitrous oxide (N₂O), an important greenhouse gas. However, the development of emission factors for N₂O is complicated by its large spatial and temporal variability. A field experiment was conducted in Ottawa, Ontario, Canada. Canola was planted on May 5^th, 2004 and urea fertilizer was applied at a recommended rate (112.1 kg N ha^-1) and a limited rate (67.2 kg N ha^-1). Surface flux chambers were placed at different topographic positions within an east to west transect of the field, to measure spatial N₂O variability. Two stationary and two mobile flux towers were used to assess the temporal and spatial N₂O variability respectively, using tunable diode lasers and the flux-gradient technique. One mobile tower and one stationary tower were located in each of the recommended and limited fertilization areas. All towers showed significant (1 – 2.7 mg N₂O-N m^-2 h^-1) emissions following rainfalls, for the period May 25^th to June 4^th because of the high soil moisture and available N, however, emissions later decreased because of the decline in soil moisture and soil N. The highest chamber fluxes occurred at the mid topographic position probably due to differences in the micro-topography of each sampling site.  Results will be used to test the ecosys mathematical model of natural and managed terrestrial ecosystems, to simulate emissions at different spatial scales. Ecosys has the unique capability of integrating spatial scales ranging from mm to km in 1, 2 or 3 dimensions allowing scaling up from microscale to landscape level.  Results will be used to develop a methodology for scaling up emissions from site to landscape scale in order to make regional predictions of N₂O, and refine emission factors for an IPPC Tier II methodology.