Fig. 1. Nitrogen rate effect on (A) grain protein, (B) starch, and (C) oil concentrations of the Illinois Protein Strain hybrids and a commercial hybrid grown at Champaign, IL, in 2001 and 2002. Closed symbols represent data from the 2001 growing season and open symbols correspond to the 2002 growing season. In each case, FR1064 was used as the female in the hybrid. The best regression model was fitted (solid and dashed lines for 2001 and 2002, respectively) and used to describe how the respective parameter was influenced by N rate. For parameters where a significant regression model could not be fitted, the regression line was not included. The fitted equation parameters are presented in Table 2. For each year, main effect LSDs (P 0.05) are included (when significant) as bars to compare a hybrid across N rates (LSD N) or to compare different hybrids at a given N rate (LSD G).