Stem height increase (A), number of emitted fronds per year (B), collar girth increase (C), annual length increase for leaf rank 17 (D), annual projected canopy increase (E) and annual leaf area increase (F) for oil palm progenies subjected to different KCl levels in Nigeria. The letters (a, b and c) explain the significant (P ≤ 0.05) differences between progenies observed at 7 years old, revealed by a Tukey test. YAP: year after planting.