Aerification timing.

It was pointed out to me that I should explain why we close the course to aerify right at the end of summer when the weather is beautiful and the course is in great shape. To give you a more complete answer I will give a bit of background first, and then cover why we aerify when we do.

First off, the goal of aerification is to reduce the layer of organic matter(thatch) by physically removing it through the process of coring the greens. Thatch is the layer of organic matter above the soil and below the green tissue of the living canopy (Christians). This accumulates through the growing season, the more the grass grows, the more the thatch layer grows.If you have healthy, well maintained greens you will have thatch. Now, there are some benefits to thatch: it's a good media for beneficial macro and microorganisms, serves as a natural filter to reduce the movement of pesticides into the groundwater and it can moderate the effects of summer heat stress (Christians). However, too much thatch can cause problems as well, such as: being a good media for turf pathogens and insects that attack turf, causing a green to be puffy, resulting in scalping, and it acts as a barrier to water and air movement, increasing disease pressure and causing the playing surface to be wet (Christians). So, we need to maintain a small amount of thatch, but doing that requires cultural practices to reduce excess organic matter.

Before I cover our aerification process, I should tell you that we have putting greens that are built to the United States Golf Association's (USGA) specifications. This means that below the grass there is a 12" layer of sand on top of 4" of gravel below. Underneath this gravel is 4" drain pipe bedded in gravel. By using sand, water can move freely through the sub-grade, which means that once the sand below the green is saturated, any excess water will flush into the 4" gravel layer and eventually into the drainage. USGA greens drain far better than "push up" greens, which are grown on whatever native soil is present. Because we have sand based greens when we aerify the goal is simply to remove the thatch between the grass and the sand below; we do not need to pull the sand out as it is the desired growing media. This is slightly different when aerifying "push up" greens because often these greens are built on poor soil, so you want to pull out as much of the old soil with the thatch and add good, quality sand in its place.

Things we do to control the amount of thatch in greens include: use of plant growth regulators (PGRs), sand topdressing, vertical mowing, solid tine aerification and core aerification. Core aerification is the most disruptive process and the one that we do the week after Labor Day. As I covered in an earlier post, our core aerification consists of; pulling plugs from the greens, collecting the plugs, topdressing with sand, and then dragging the sand into the holes. Aerification opens the thatch layer and allows moisture and oxygen in, which increases microbial activity that is responsible for thatch breakdown. Filling the holes with topdressing sand firms and smooths the playing surface and also speeds recovery (Christians). Along with all the plant health benefits, this is also an integral step to keep greens firm and fast all year long.

Because aerifying is such a stressful process we wait until after the heat of summer to minimize any mechanical damage we may cause. However, a sufficient amount of time should be allowed for recovery from fall aerification before winter dormancy and by aerifying while the grass is still actively growing the greens are able to quickly heal in (Christians). This means that the ideal time is early September. While this does seem early, keep in mind that we are in northern Ohio and cool temperatures can quickly set in by late September or early October. Furthermore, the later we get in the year the shorter the growing days and that coupled with dropping temperatures slows down plant growth as it prepares for winter. We are 13 days removed from aerifying greens and are almost completely healed in. Sunday morning it was 37 degrees at the course and we already are having cooler than average temperatures, I wouldn't have wanted to wait a day longer with the way this summer has gone already.

I hope this answers most of your questions but if you have any more, please feel free to ask! Thanks.

All the citations are from: Fundamentals of Turfgrass Management. Second Edition. Nick Christians.

Ian