Turf aeration

One of the questions that I frequently get is "how often should I aerate my turf grass?"

The answer is simple. Whenever it needs it. Okay, a little background. Aerating turf means puncturing the thatch and top soil layer to allow water and air to better access the root zone. In most landscape, and for a variety of reasons which shall be addressed in another post (if ever) root zones are fairly shallow perhaps 3-5" in depth.

There are different ways to aerate turf including spiked shoes (no joke), tined hand tools (think pitch-fork) and the most common, commercial aerating machines. But as to the question of frequency...

The first consideration is soil composition. Southern Utah soil is naturally sandy or contains significant amounts of clay and non-loamy material.

Sandy soil allows water to penetrate but does not retain water at an optimal root zone depth (say 8" to 24" below ground). Soil that is too sandy acts as a sieve and water is quickly lost into the ground.

On the other hand, clay soil inhibits water penetration and surface irrigation tends to stand or run off. That is bad for the grass and bad for the water budget. Normally the longer the water sits on the ground, the better depth of absorption can be achieved. Super high clay content is the opposite problem of sandy soil and will cause the water to stand too long leading to fungus, root rot and other problems. So examine a fist full of soil. If the soil has fine grainy sand, you are probably losing water and minerals. If the soil balls up like silly putty when you squeeze it in your hand you have clay. "Good soil" will hold together lightly and crumble in a nice loam.

Another method is to observe the water delivery. Allowing for slope of terrain, if the sprinkler water runoff is excessive, you probably have a high clay content in the soil and aeration may help the water penetrate and provide better water retention.

Next factor is thatch. Thatch is nothing more than a build up of organic material above the root zone. Most commercial landscapers do not use mulching mowers; instead bag and remove clippings each time the turf is cut which reduces accumulation of thatch zone. Even so, over time residual clippings may buildup faster than nature can break them down and the thatch zone may divert water laterally rather than allow for surface penetration and root zone watering. A simple way to check for thatch is to brush your fingers through the turf at the soil line. If more than an inch of thatch is present throughout, aeration can help punch holes to let the water and air do their thing.

Finally, the overall maintenance schedule has relevance for if/when to aerate. While aeration can be done in any season, I recommend late winter or early fall. The reasons are twofold. There is less mechanical watering taking place and the likelihood for damage to sprinkler heads or pipes is less severe than at other times of the year.

Also, when pre-emergent chemicals are applied, usually in mid springtime and or autumn, aeration should be avoided for 90-120 thereafter. The nature of aeration simply punctures the pre-emergent barrier and reduces the efficacy of the chemical.

So accounting for soil composition, watering and chemical schedule and thatch buildup I recommend most southern Utah lawns be aerated at least one time per year. Happy humus!