Oak trees only need fertilizing when they are young, as feeding or fertilizing mature healthy oak trees is not necessary. This is because decomposing fallen matter from the oak tree is usually sufficient enough to fertilizer around the roots. Give your young oak tree a jump-start in growth by feeding them in late winter and late spring.
Layer a 20 percent nitrogen fertilizer from your local gardening store. Use roughly 15 pounds per 1,000 square feet, but this amount may vary depending on your climate or the brand of fertilizer.
Use the trowel or small shovel to dig small holes that around 8 inches deep and about 6 inches in diameter. Dig a hole every 2 feet around the tree, in the same area as the drip line. The drip line is where rainwater drops off the tips of the branches and hits the ground. Add fertilizer into these holes, distributing it equally.
Backfill the holes with the dirt removed. Soak them each with water if no rainfall is coming within a couple of weeks. Water each fertilizer hole with about 20 gallons of water.
Apply fertilizer on top of the ground if you absolutely cannot dig holes around the tree. Add it around the tree in the same amount, and do this before a rainfall or with irrigation. Doing this will not work as effectively as digging the holes.