Fig. 3. Harvest index (HI) and nitrogen harvest index (NHI) of wheat culms for 12 unique wheat genetic backgrounds. Values are least squares means (n = 36) of three replications across 2 yr, two production systems, and three subpopulations. The HI bars with the same lowercase letters and the NHI bars with the same uppercase letters are not significantly different according to Tukey–Kramer mean comparison test at P = 0.05.