Aeration is a cultural practice that does not need to be done often but can provide immense benefits for your lawn.
Soil is comprised of minerals, organic matter, and the spaces in between those particles. The spaces in between the particles hold water and air. Ideally, soil will have a relatively equal number of small pores that hold water and larger pores that hold oxygen. When soil is crushed, the spaces in between the particles get smaller, and the soil becomes compacted. Parking your vehicle on the lawn, heavy rainfall events, and even persistent walking by pets can lead to soil compaction. Heavy clay soils are easily compacted, but even lighter sandy soils can develop compaction.
Soil compaction negatively affects turfgrasses. It limits the amount of oxygen accessible to the root system. Soil oxygen is needed to break down the sugars created by photosynthesis and generate energy for growth. Reduced soil oxygen also impacts water and nutrient uptake. Centipede and St. Augustine do not tolerate compaction and become thin and patchy. Zoysia and Bermuda are more tolerant of compaction, but all warm-season grasses can develop diseases associated with compacted soil conditions.
Core aeration is the practice of pulling 2–3-inch cores out of the soil. Solid-tine aeration is not as beneficial because it pushes soil to the side and below the solid tines and increases compaction. Core aeration offers several benefits for home lawns. It reduces soil compaction, fuels turfgrass growth, helps limit the development of large patch and other diseases, and can also help control thatch.
Thatch is the layer of dead plant parts between the soil and the actively growing grass, and it needs to be managed in some turfgrasses. A thatch layer that is up to ½ inch thick can benefit lawns. It provides cushion and resiliency, but it can be detrimental to turfgrasses when the thatch layer becomes thicker. For more information on thatch, please see HGIC 2360, Controlling Thatch in Lawns.
Thatch accumulates more quickly on compacted soils. Core aeration increases the activity of soil microorganisms that feed on the thatch, plus the cores can be left and watered back into the grass to introduce those microorganisms to the top of the thatch layer. Core aeration should be done during the growing season at least once a year for heavy soils and as needed for lighter soils. For more information on aeration, please see HGIC 1200, Aerating Lawns.