Aeration is a remedy for compacted soil.
A layer of soil as thin as .25 or .50 inches can severely retard water infiltration. Compaction also interferes with the necessary escape of carbon dioxide from the soil and the capture of oxygen by the soil. Compacted soils are associated with acceleration of thatch accumulation. For best results, run the aerator over the lawn, then make a second run perpendicular to the path of the initial run. Slightly moist soil is desirable since the tines will penetrate farther than under dry conditions, which may cause the tines to ride on the surface or only slightly pierce it.