Fertilizing trees can be very complicated when researching. There are just too many variables. Your main priority should be fertilizing to promote root growth on newly planted trees.
When fertilizing newly planted trees, I only use a high phosphate fertilizer. That's the big middle number. This encourages roots to grow. It will mean that the top half of the tree pretty much sits there, but the tree needs to get it's roots spread out more.
In the planting year apply 1 tbsp of high phosphate fertilizer (i.e. 10-50-10) per pot size gallon (if the tree comes in a 2 gallon pot, use 2 tbsp's) and water the tree in very well. The fertilizer will spread to however large the area you're watering is, so don't let the water get more than 2 feet away from the newly planted tree or its a waste.
Each year after the planting year, in the fall apply a tbsp of slow release balanced fertilizer per foot of tree height.
Once the trees have been in place for more than 3 years and are pretty established, I really haven't found the need to continue fertilizing. I'm sure soil tests could be valuable to see what you're soil is deficient in, if you are so inclined.