Determining optimum timing for nitrogen (N) fertilizer application is one of the key challenges that crop producers face. Three experimental sites were established in the spring of 2005 to evaluate the effects of delayed N fertilization on corn grain yield and nitrogen use efficiency (NUE). A randomized complete block design with three replications was employed for this study. Four pre-plant N rates (0, 45, 90 and 180 kg ha-1) and three top-dress N rates (45, 90 and 180 kg ha-1), applied at three growth stages (V6, V10 and VT) resulted in fourteen treatment combinations. This study will help determine how late N fertilization can be applied without reducing corn grain yields.