Not so long ago, to fertilize a tree we would make holes in the ground with a crowbar and fill them with granular fertilizer. This did help the trees but we have made great progress since those days.
Today, we think of fertilizing as a method of adding soil amendments. These amendments might be kelp extracts, fish emulsions, yucca extracts or mycorrhizae. By amending the soil with the right materials we do a better job of helping the trees while being better environmental stewards.