For a stand of turfgrass, the thatch layer is similar to the fat layer in the human body. In fact, it might even be perceived the same. People often think of the body’s fat as a negative. And, indeed, if that layer gets too thick, it surely can be. But a level of fat is actually a needed component of the human body. Fat has been linked to increased longevity, absorbing and storing vitamins, providing and storing energy for muscles, protecting our fragile organs, as well as insulating us against the cold.
Although we spend enormous chunks of time and effort in trying to get rid of fat, we certainly wouldn’t want to go cold turkey.
The same can be said for those pesky thatch layers in golf course greens.
There are many known negatives to an extensive thatch layer in greens. Here’s a quick rundown of a few of them:
- Soft, spongy, bumpy surfaces, resulting in slow green speeds and bouncing balls.
- A breeding ground for many turfgrass diseases as well as some harmful insects.
- Restricts air and water from reaching the roots.
- Restricts fertilizers and other beneficials from reaching the roots.
- Nutrients aren’t as readily available and can even be lost into the atmosphere.
- Can tie up chemicals, reducing their effectiveness.
- Your roots may end up taking hold in the thatch layer, which is a poor medium for growing good turf.
- Reduces drought resistance.
- Balls plug on saturated greens.
Excessive thatch prevention and, ultimately, excessive thatch removal are necessary cultural controls for any golf course management program.
Thatch prevention includes carefully monitoring pH levels; avoiding shallow, frequent irrigation; a regular verticutting and topdressing program; aeration; not overfeeding; as well as minimizing compaction (granted a tough one for golf course managers).
Thatch removal includes aeration (removing the cores) combined with topdressing, as well as the use of extensive thatch-removal machines.
But remember, we want to keep some thatch there. Ideally, somewhere around 0.5 to 0.75 inch is considered acceptable in the industry.
Here are a few of the positives of a beneficial thatch layer:
- Buffers soil temperatures, acting somewhat like an insulator.
- Actually helps reduce compaction to the soil — just imagine if there was nothing between your grass blades and the soil beneath them.
- Although not so much a factor in golf course greens, thatch can help reduce seed germination in your tee, fairway and rough areas by keeping the weed seeds from coming in contact with bare soil.
- Moisture retention, which can be a good thing from time to time, but also falls in the negative category when the water can’t reach the roots.
While these are good things associated with the 0.5- to 0.75-inch thatch layer, it’s not easy to keep it in that optimal range. One of the ironies of all the state-of-the-art maintenance practices superintendents use on golf course greens is the fact that these practices often greatly increase the thatch layer. In fact, irrigation and chemical and fertilizer applications all contribute to building thatch.
One thing to keep in mind is that thatch buildup occurs when new plant tissue develops at a rate greater than the rate of decomposition. Unfortunately, for a high-end playable golf course green, we’re often in the business of encouraging that new plant tissue.
Another factor in our little story of thatch is the role microorganisms play in the drama. Microorganisms decompose organic matter in the thatch. The fungicides we use may kill the diseases on our greens, and the insecticides we apply may kill harmful insects, but both reduce the number of beneficial microorganisms that were helping with the thatch breakdown.
Safe to say it’s a constant battle. We giveth and we taketh away. Two steps forward, one step back.
It wouldn’t be any fun if it was easy, right?