Homeowners have likely heard of core aeration as a way to relieve soil compaction in the lawn. While that is certainly true, coring has several more benefits for the grass plant, soil profile, microbial activity in the ground, and thatch management.
When the soil beneath the lawn is compacted, grass roots grow poorly, staying nearer the surface and more readily impacted by droughts. Coring allows the soil to relax and expand into the vacated core. This allows deeper roots. To encourage deeper roots, the core allows more soil oxygen into the profile along with water. Both of these promote deeper rooting of your lawn grasses. Deeper root systems allow better disease resistance, for example.
Another benefit is the increased ability of the lawn to remain green and actively growing during a brief drought. If any topdressing is done with quality black dirt or using well-composted organic matter, this material will find its way into the core as well, improving the soil profile. Any kind of organic matter also will support the microbial life in the ground, improving the symbiotic relationship between the grass root system and the microbes in the soil. Research shows that if the soil is in good health with teaming microbial activity, that, in turn, supports good grass growth by providing critical elements to the grass plant.
Core aeration also will assist the homeowner with maintaining thatch levels under a half-inch. Homeowners hearing the word “thatch” often think the worst. In fact, having some thatch benefits to the lawn. Thatch acts as insulation, protecting the crown of the grass plant from quick changes in the weather, such as a sudden drop in temperature. Thatch also provides a cushion from foot traffic, again protecting the grass plant crown from being crushed or damaged. Coring breaks through the thatch layer opening up those opportunities for air and water movement already mentioned.
When the core is ejected by the machine, there is a plug of soil that is left on the surface. That soil containing those microbes can now begin to break down the thatch layer from the top down. When the thatch layer is well more than a half-inch in depth, using the typical de-thatching machine often will result in the loss of the entire lawn. Coring is a way to recover the lawn without such a drastic measure. This will not happen in one season and other management activities such as high rates of fertilizers should be modified.
Core aeration alone will benefit the health of the lawn. Combining topdressing with any reseeding or over-seeding with regular watering for at least three weeks will really turn the lawn around. Bluegrass lawns have two peak growing cycles in our climate. The greening and rapid growing in the spring is the first one. The second flush, or growth, is more about the root system expanding and storing food reserves in the cooler temperatures of fall. There is still growth above ground and mowing, with a sharp mower blade, should continue well into late fall.
Richard Hentschel is a Horticulture Extension educator with University of Illinois Extension, serving DuPage, Kane and Kendall counties. Questions about your yard or garden? The Kendall County Master Gardener Help Desk is still open this season. Trained volunteers are available to help with your tree, garden, lawn and other horticulture questions at 630-553-5823.