Fig. 6. Quadrant chart with deviations from the regression (of N treatment grain protein content at a given environment against the mean grain protein content of all treatments at that environment) on the y axis (computed as the error mean square), and the regression coefficient (b value) on the x axis for each of the 25 N treatment combinations. The amount of N fertilizer applied at growth stage 25 and 30 (rounded to the nearest kg ha^–1) are indicated for the treatment combinations falling in the lower left quadrant.