Q. Do I fertilize my peach tree even though it looks like it's doing great? If so, what type of fertilizer and concentration would you use and how often?
A. You adjust your fertilizer application according to how the tree is growing. If your tree is growing well, then reduce the amount you apply but do not eliminate your fertilizer application.
If the growth is lush, then cut way back on the amount of fertilizer that you apply. If you're growth is skimpy, then increase the amount of fertilizer that you apply. By cutting back I would reduce it by half. If you're increasing the fertilizer, then increase it by half the amount.
You can increase the amount of fertilizer you give a tree by increasing the amount you give it in a single application or, a much better approach, apply it more often in smaller amounts. You can accomplish the same thing by switching to slow release fertilizers. They are more expensive but they release fertilizer more slowly over time and so require only one application each year.
Begin fertilizer applications in late January and continue them into July if you want to but use very small amounts of fertilizer at each application. You can apply fertilizer as a single application in late January and not fertilize again for the rest of the year if you want to. That will also work. Do not skip your iron applications regardless of your other fertilizer application.