I don't recall what it is but it's a time release fertilize I got from The Wildlife Group down around Montgomery, AL. I mostly just used this though for the 1st few years after planting. Now that my trees are 10 years old I really don't bother anymore. What Chapman said above agrees with what I've read for established trees.
Composted manure, top soil (it can be the Cheap stuff) and manure tea. All of these add back to the soil what is needed while commercial fertilizers tend to damage or kill native microorganisms plants need.
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