Answer: I wouldn't worry too much about the exact placement of the fertilizer over the dripline. Trees and shrubs tend to have feeder roots in a wide band around the circumference of the trunk, not just at the drip line. Spreading the fertilizer in a fairly wide band will ensure that it reaches these roots. You might take into consideration the age and size of the tree. If it's a mature plant, the feeder roots probably extend out farther than a fairly young one. For a mature plant that has been pruned regularly, I would center the band of fertilizer at the pruned dripline, and spreading it in a band a foot or so wide for a shrub, and in a larger band for a tree. If the tree/shrub was pruned back severely--say, it was 5' in diameter when you acquired it, and it you have now pruned it back to 3' and kept it that way, I would extend the fertilizer out to the 5' mark. The shrub would have established roots all the way to that point and they would still be there.
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