Improving soil conditions for turf with fall aeration

Fall aeration improves growing conditions to develop a healthier stand of grass.

The summer of 2012 will long be remembered for extended hot and very dry conditions. In its wake are plants that barely grew, some damaged and others that did not survive. Lawns were not immune to these summer stresses. Grasses growing on compacted soils that are poorly draining develop shallow root systems less suited to withstand excessive heat and drought conditions. Improving these conditions this fall will lead to a healthier lawn that is less susceptible to future summer stresses.

Compacted soils are not unusual in regions of Michigan with clay soils. Along with compaction, we often see an associated problem with thatch buildup. Thatch is an organic layer made up of woody tissue from dead grass roots and stems. It is found under the grass plants right at the soil line. Normally, it breaks down just like leaves in a compost pile, but poor draining conditions inhibit the microorganism responsible for reducing the thatch layer. A layer of thatch greater than 0.5 inches reduces water infiltration. Grass growing in these conditions takes root in the thatch instead of the soil where roots are less protected from summer heat. A thick layer of thatch may feel spongy, or you may notice that water runs off the lawn without penetrating the soil.

A management tool to combat the buildup of thatch and also alleviate compacted soils is core aeration. Core aeration removes soil plugs out of the lawn, allowing air and water to penetrate down into the soil. The goal is to alleviate compaction to improve water and oxygen movement in the soil which will increase rooting. Grass roots growing down in the soil instead of in the thatch are less susceptible to excessive heat and fluctuations in available moisture.

Most core aerators are self-propelled machines with rotating hollow tines that push into the soil, removing plugs that are 0.75 inches wide and about 2 to 4 inches long. Depending on the type of aerator, holes are spaced from 2 to 6 inches apart. Aeration works best when there is good soil moisture. A dry soil may deter the tines from penetrating the soil. If conditions are dry, it will be necessary to water the lawn thoroughly a couple days before using an aerator. Avoid aerating in wet conditions that cause the soil plugs to stick inside of the tines. Late summer through early fall is a great time to aerate a lawn. Improved soil aeration will coincides well with the active growth period for lawns in the fall.

Is aeration need yearly? Lawns that have frequent foot traffic, especially those with a higher percentage of clay, would benefit from a yearly aeration to alleviate compaction. Lawns that are not compacted and where thatch is less than half thick will not need yearly aeration.

More information on aerating lawns can be found in the Virginia Cooperative Extension publication, Aerating Your Lawn.

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