Nitrous oxide emission was monitored for three years in plots conventionally and organically managed.  Both systems had a four-year rotation, strip tillage and fertilizer applied based on spring soil test results. The conventionally-managed system received nitrogen-containing fertilizer during the corn and wheat phase. Although not certified organic, the organically- managed treatments followed certification standards to the greatest extent possible.  The organically-managed system had manure added only during the nitrogen phase.  The corn phase of the rotation released the most nitrous oxide in the conventionally-managed system all three years and in two of three years in the organically-managed system. In both systems nitrous oxide emission was associated primarily with spring thaw and fertilizer application. The two systems did not differ in the amount of nitrous oxide emission or methane measured during the three-year study.  However, because the organically-managed system was less productive, there was more greenhouse gas emission per unit of biomass produced in two of the three years.