Iowa State University Extension
Aerification is one of the most basic and essential tools used to manage lawns. There are many different types of aerification machines on the market today. The general premise behind aerifying is that holes, about the size of your finger, are poked in the ground to somehow make the lawn better.
The holes can be made with hollow tines that bring some soil and thatch to the surface or they can be made with solid tines that make holes without bringing material to the surface. A knife-type of tine also can be used to shatter dry soils and create many cracks in the ground that also serve for aerification. Most lawns receive a real benefit from solid, hollow and shatter tine aerification. The following discusses some of the situations where aerification is especially beneficial.
Heavy soils and compacted conditions – Iowa has some rather productive farm soils, unfortunately they don’t always end up directly under your lawn. Any situation where heavy clay soil is the major component can be improved by core aerification. Often the native topsoil is removed during construction and it is never adequately returned before lawn establishment. The clay and subsoil condition becomes very hard from the surrounding construction. Compacted and heavy clay conditions simply do not allow sufficient space in the soil to grow roots or store water and air. Lawns with compromised root systems usually fail during hot and dry conditions in the summer. In this situation the benefits from aerification are increased space for rooting and reduced compaction.
Sodded lawns -- Root systems on sodded lawns sometimes remain in the upper layer that was sodded instead of penetrating into the soil that is on site, especially when soil conditions exist as described above. Roots stay in the good soil from the sod farm and avoid the less desirable soil conditions on site. Sod may also come with a dense layer of thatch, especially if it is two years or older when harvested. Sod usually performs great for the first year, but may begin to suffer if it is not managed properly. Hollow tine aerification is an excellent way to break through the sod layer, remove thatch and mix the two soil types together. In this case the real benefits are thatch reduction and root penetration from the sod layer into the soil below. Deeper and more prolific rooting means better turf.
Worn areas – Intensely used areas first wear away the grass and then compact the soil, even on the most productive loam soils in Iowa. Lawn areas that are intensely used by people, vehicles and pets are prone to thin grass, exposed soil and hard conditions. The only way to turn this situation around is to use aerification to fracture the ground and then reestablish the grass. An aerifier hole makes a great environment to start grass even when traffic conditions continue. The grass that established in an aerifier hole has its crown protected below the surface of the surrounding soil and is more traffic tolerant. The tell-tale signs of beneficial aerification are often evident in areas of traffic and drought. The only grass growing in these areas will be in the aerifier holes. These benefits from aerification are visually convincing and it should be obvious that you need to do more of this “good thing.”
Thatch – Thatch is a layer of living and dead roots, crowns and lower shoots that forms between the soil surface and green vegetation. Moderate thatch formation is a normal development in lawns. However, problems can occur when the thatch layer is excessive. Thatch is seldom directly responsible for turf death; however, it usually leads to other disease, water and shallow rooting problems that eventually kill grass. Hollow tine aerification is the best method to keep thatch checked at less than one-half inch thick. The hollow tine physically removes some thatch, but more importantly it distributes soil cores on top of the grass and thatch.
Once the soil is dispersed on the surface it distributes soil and microbes that help decompose the thatch faster. This is the lawn care version of a farmer plowing the stubble into the ground to facilitate decay of plant residue. We can’t plow our lawn each year, but we sure can use hollow tine aerification to topdress soil over the surface and breakdown the organic layer developed from thatch build-up. Earthworms also do an excellent job of making holes, bringing up soil and managing thatch. Where worm activity is limited, aerification will certainly help.