having planted literally thousands of trees(for both the state and for myself), I feel more important than adding any fertilizer, is keeping moisture levels adequate. If you look at the growth ring of a tree, you'll see some lines are big, some are small. This is due to good moisture years and bad moisture years. For the most part trees can get enough nutrients out of their soil without adding any(unless you live in very sandy soil). One would do better to ensure moisture levels were good to get best/fastest growth. With acorn producing oaks, you can see the difference in dry years and wet years. It takes alot of moisture to get acorns much less any fruit to develop. Take a 55 gallon barrel filled with water to your trees once a month to ensure good moisture. A trick to help water is to take a few gallon jug, fill and tip over so the nozzle end is in the soil. This allows a slow drain of the water and lets you leave instead of staying around till water is gone. Taz