A field study was established in 1959 on a Brookston clay loam soil in SW Ontario to evaluate the effects of fertilization and crop rotation on crop yields, soil and environmental quality.  There were two fertilizer treatments (fertilized and not-fertilized) and six cropping treatments which have been maintained for 51 years. The crop rotation treatments included continuous corn, continuous Kentucky bluegrass sod and a 4-yr rotation of corn-oat-alfalfa-alfalfa with each phase present each year.  We measured N₂O emissions, inorganic N and plant N uptake over 3 growing seasons (2007-2009) in the corn phase (i.e. fertilized and not fertilized continuous corn and rotation corn). Nitrous oxide emissions varied over the 3 years as a result of the seasonal variation in precipitation quantity, intensity and timing in addition to the differences in crop growth and N uptake. The fertilized continuous corn lost, on average, 7.00 kg N/ha from N₂O emissions whereas the unfertilized continuous corn lost only 0.36 kg N/ha.  When corn followed plow-down of alfalfa, the fertilized rotation corn lost 5.49 kg N/ha which was 22 % lower than fertilized continuous corn. The not-fertilized rotation corn, on the other hand, emitted about half as much N₂O (2.50 kg N/ha) as the fertilized rotation corn. The dramatic differences in N₂O emissions between fertilized and unfertilized treatments were somewhat reduced when yield specific N₂O emissions were determined.  The fertilized rotation corn treatment had corn grain yields that averaged 9.85 t/ha over the 3 years followed by fertilized continuous corn at 5.51 t/ha.  The unfertilized rotation corn treatment had yields that were 60 % lower (3.96 t ha^-1) than fertilized rotation corn, whereas the unfertilized continuous corn had yields that were 74% lower (1.44 t/ha) than fertilized continuous corn treatment and 85% lower that fertilized rotation corn. This study demonstrated that N₂O emissions could be dramatically affected by long-term management practices and that crop rotation treatments had lower emissions in the corn phase of the rotation even though the N input was greater due to fertilizer addition and legume N fixation.  These N₂O emission and yield results were due to the differences in N uptake and soil quality between the treatments.