Increased nitrous oxide fluxes from continuous corn-planted soils of Penn State's long-term Hunter Rotation Experiment in central Pennsylvania have been observed in midseason when corn enters the tassel development stage. Peak N₂O fluxes up to a fiftyfold higher than background fluxes occurred at similar times in replicated plots fertilized with inorganic fertilizers or liquid dairy manure. However, N₂O fluxes from inorganically fertilized plots were significantly greater than from manure-fertilized plots. Although molecular analyses revealed differences in soil microbial community structures for the two fertilization treatments, simultaneous occurrence of high N₂O fluxes from plots under both treatments suggested that plant growth stage, possibly mediated through effects of root exudates, exerted a stronger influence on N₂O emissions than did soil microbial composition. Alternative explanations for N₂O emission increases will be discussed, along with experimental approaches for assessing relative contributions of nitrifiers and denitrifiers to N₂O emissions from soils.