In temperate climates, a significant fraction of annual emissions of nitrous oxide (N2O) from agricultural land occurs during soil thaw. The objective of this study is to determine the impact of conversion of long-term fallow grassland to perennial grass bioenergy crops on N2O emissions during spring-thaw, and to identify field-scale features that influence emissions. We measured mid-afternoon fluxes daily from March 27th to April 7th 2013 from fallow and reed canarygrass over a short topological gradient using static chambers. Soil temperature, volumetric water content, and above-ground biomass were also observed, as were hourly air temperature and precipitation. Hot-moment analysis, non-parametric statistics and modeling results show that in the reed canarygrass, the topologically low subplots exhibited significantly elevated emissions compared to the fallow. Our results suggest that conversion of fallow grassland to perennial grass cropping systems for bioenergy or other uses could increase spring-thaw N2O emissions in wetness prone areas.