Compacted soils are difficult for roots to penetrate and are prone to drought. They typically have lower nutrients and organic matter creating an inhospitable place for your tree to grow. The tree may respond by creating roots that are at and above the soil surface.
There are a number of possible treatments including tree-hole soil replacement, compressed air treatments, radial trench soil replacement and soil cultivation. But the easiest method is mulching. Apply composted yard waste or bark mulch in a layer 2-4” thick from near the trunk to (preferably) the drip line. Never put the mulch directly against the trunk. Annually reapply mulch as necessary to ensure adequate thickness. In the long term, this will protect against additional compaction and provide organic matter to aid in soil-structure development.
For more information on this and other methods of treating soil compaction, go to: