Aerating Your Lawn

An attractive lawn begins with a healthy root system. Roots growing in light airy topsoil can grow deep to be firm and robust. In a heavy clay or compacted soil, oxygen, water and nutrients do not enter the soil causing roots to be weak and prone to diseases and stress. Lawns that have a weak or shallow root system are thin and yellow-green in appearance. They do not hold up well to foot traffic or weather stress, and are slow to recover when damaged. Aerating improves rooting by loosening compacted soils and breaking up thatch. It allows water and other nutrients to seep into the soil, encouraging new root growth and establishing a stronger deeper root base for a lusher, healthier turf.

Thatch is a compressed, light brown organic matter that looks like peat moss and is located between the soil line and grass blades. As this layer gets thicker it will eventually stop air and water flow into the soil creating a shallow environment for root growth. To tell if thatch has reduced aeration, cut a small wedge of turf down to the soil with a knife. If the thatch layer is more than ½ inch thick, the turf needs to be aerated.

The frequency of aerating will depend on the type of soil and the amount of use your lawn receives. Clay soils with heavy use or lawns with excess thatch build-up need to be aerated twice a year. Other soils with less activity should be aerated only once a year. It will take three consecutive years of aerating for the yard to receive the maximum benefit.

Core aerifying can be done anytime the grass is actively growing. For cool season grasses such as bluegrass, fescues, and ryegrass, the best times are March, April, and September. Aerifying should be done before fertilizing, seeding or applying crabgrass preventers. Warm-season grasses such as Bermuda grass, buffalo grass, and zoysia grass, can be aerified from late May through July. It is important to allow at least four weeks of good growing weather for the plants to recover and fill the open aerator holes.

To aerify, use a core aerator with either hollow tines or metal tubes. Cores pulled from the soil let air and water filter in. These cores should be 3/4 inches in diameter, 2 to 3 inches deep, and 3 inches apart. This will require three or more passes over the turf with the machine. Soil moisture at the time of aerating is important. If it is too dry, the tines do not penetrate to a sufficient depth. If the soil is too wet, tines will clog and not deposit the cores on the soil surface. The weight of the machine can be adjusted for the soil conditions.

Lynn Loughary, LLoughar@oznet.ksu.edu
County Extension Agent, Horticulture
Wyandotte County, Kansas
Kansas State University Research and Extension