Managing Thatch

Recently received a couple of questions about managing thatch.

One question was concerning the recent trend in the industry to not core putting greens and only use solid tines. 

Non-coring programs rely on topdressing to dilute the organic matter (thatch) that accumulates, thus forming a mat layer as opposed to a thatch layer. Turgeon defines mat as a tightly intermingled layer composed of living and partially decomposed stem and root material and soil from topdressing or other sources that develops between the zone of green vegetation and the soil surface. A mat layer is a more desirable growing medium for turf because the physical properties are much better than a thatch layer.

Routine topdressing with sand and re-incorporation of sand/soil cores after aeration produced this well-developed mat layer in a Kentucky bluegrass sports turf.

Thus, a non-coring program may be successful IF thatch is sufficiently diluted into a mat layer that no longer exhibits the detrimental conditions of a thatch layer. A non-coring program has an increased risk of failure when a topdressing program is inadequate and the concentration of organic matter (thatch) becomes excessive.

A second question asked whether there is a simple way to help with the acceleration of decomposing organic matter.

Unfortunately, there is no simple process to accelerate decomposition of excessive thatch. The species of grass, climate, soil conditions and management control how rapidly thatch will develop and accumulate.

Kentucky bluegrass, creeping bentgrass and hard fescue are examples of cool-season grasses that can produce excessive thatch, especially when improperly managed. Over-fertilization with nitrogen and over-watering stimulate growth of thatch. Acidic soil pH will reduce the decomposition of thatch. Cultivation (vertical mowing and aeration) practices that mix soil with the thatch will increase organic matter decomposition and/or modify that thatch into a mat layer. Read more details on thatch management at https://njaes.rutgers.edu/pubs/publication.php?pid=FS740

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