Sand-based Athletic Fields - Aeration and Topdressing For Proper Thatch Management

Aeration and Topdressing For Proper Thatch Management

Aeration on a sand-based system is used more to control the thickness of the thatch layer than to relieve compaction. A thick thatch layer on a sand-based athletic field can be detrimental. These layers prevent essential nutrients and water from reaching the plant. Further, fertilizers, fungicides, and insecticides can not penetrate the surface and reach the soil. This can obviously be devastating if a field is consumed by a soil borne disease or insect. Water penetration can also be deterred by a thick thatch layer. When there is a thick mat of organic matter near the surface of a field a second perched water table will form. This will cause roots to stay in the top couple of inches of soil because they do not need to search for water at greater depths. Without a deep root system, a field can become unsafe due to footing issues.

Core aerification is the most conventional way to control thatch. Taking up plugs and removing them from the surface eliminates much of the organic matter that is in the soil. The most common aerificaiton tines used are usually a half inch in diameter, normally penetrate about four inches, and are hollow. If the holes are on 2 inch center, 36 holes will be punch per square foot. After a field is aerified, the cores can either be raked up and removed, or left on the surface to break down. Solid tines will punch holes into surface but are only a temporary solution. This is because they do not reduce the organic layer, but merely displace it. Another common method of reducing thatch is vertical mowing. This consists of vertical blades tearing into the soil and pulling out organic matter. It is very effective at reducing thatch, but is also very disruptive. This can lead to a long recovery time for the turf. Reducing the amount of thatch at the surface allows nutrients and pesticides to penetrate into the soil more effectively. Collecting grass clippings will not reduce the formation of a thatch layer. Thatch layers are made up of decomposed vegetative parts of grass plants like stolons and rhizomes.

Once a field is aerified, and there are holes in the surface, a field should be topdressed with the same sand that was used in the construction of the field. Refilling the aerification holes with sand improves the macroporosity of the soil and allows better penetration of water. This will allow the turf manager to water deeper and therefore improve the root system. Introducing sand into the thatch layer allows the growth media to be suitable for play. Without sand mixed with the thatch layer, divots would readily kick out and the field would not be safe for any type of sport.