Fig. 3. Nitrogen nutrition index (NNI) of corn fertilized with various N application rates in an experiment conducted at three sites in each of 2 yr (2004 and 2005). The NNI is presented for the different sampling dates expressed in cumulative corn heat units (CHU). Vertical bars represent LSD values (P 0.10) at each sampling date; ND: LSD was not determined. 250s indicates 250 kg N ha^–1 applied at planting.