"Read" the soil to know how to fertilize
Most roots grow and "feed" in the top 12-18 inches of the Earth.
If the soil below that layer is much paler than what's above, the
Earth is telling you that nutrients leach very readily from the
Below where a backhoe has just cut away a bank and left the tree
roots sheared or hanging, two blue lines mark the top layer.
In such a place, be sure to fertilize a little bit at a time,
frequently, or use only slow release organic fertilizer. Anything
else would be mostly wasted as it dissolves and flows down out of
the roots' reach.