Fig. 1. Changes in N concentration as a function of thermal time (cumulative corn heat units, CHU) of corn fertilized with various N application rates in an experiment conducted at three sites in each of 2 yr (2004 and 2005). 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.