Aerate clay, sandy or loamy soil in spring or fall at least every other year for an improved lawn. Aeration is the best way to combat compacted soil, such as under playground equipment or well-trod pathways through the lawn. It's also a good method to help revitalize a tired lawn and remove thatch. Thatch limits root growth and increases chances of disease, and aeration is the most effective way to manage it. The result is a healthier grass root system.
Core aeration is recommended for clay and loamy soils. When aerating the lawn, the ground should not be frozen or too wet. An aerator pulls 3 inch plugs from the ground, coring in the soil. The plugs decompose naturally in a couple of weeks, adding nutrients to the soil as they do. The holes in the soil allow nutrients to reach the roots. You can rent an aerator or hire a lawn care company to do the job. Criss-cross the soil with the aerator to ensure you completely cover the area.
Aeration also can be performed on sandy soils. However, instead of pulling plugs from the ground, the machine's spikes are plunged into the soil, leaving 3 inch deep holes, allowing nutrients to reach plants' roots.