Recent studies suggest that corn yields can be increased by using high clearance vehicles to apply extra (i.e., in addition to that normally applied by producers) fertilizer nitrogen (N) during the growing season. We conducted studies to determine the frequency of response to extra N applied in strips going the length of fields managed by producers. Extra (56 to 112 kg N ha-1) fertilizer N was applied (dribbled on the surface) in replicated strips at a total of 66 sites over 3 years. The extra N was either applied in late June or July. Yield responses were measured by using yield-monitoring combines. Although responses were greater to applications in June, mean yield responses to extra fertilizer N were not great enough to justify the expense of the fertilizer and application. The lack of yield response probably can be explained by near normal spring rainfall; the earlier studies showing responses to the extra fertilizer N were conducted following above-average spring rainfall. This finding indicates that application of extra N is not likely to be profitable in most years.