To address the soil compaction and stressed roots, Paul shows Allison how to use an auger, like you would use to plant bulbs, to drill holes in the soil. They drill dozens of holes, each about a foot apart. If they hit a tree root they just reverse the drill and try somewhere else. After drilling the holes, Paul helps Allison fill them with a composted product that contains beneficial fungus known as mycorrhizae. It dramatically increases the roots' ability to take up nutrients and fight disease. In return, the roots feed the fungus. This symbiotic relationship results in improved plant growth, prolonged life, less need for fertilizers and, hopefully, a much healthier tree. Its a natural way of promoting the health and vigor of the tree, but it takes a while so dont expect overnight results.
One more thing is crucial to a healthy tree: deep, thorough watering. Try for 30 minutes, and watch for runoff so you dont waste water. A good watering should get way down into the subsoil. It will help the tree, and also help get the beneficial fungi growing actively.