October 2017

SportsTurf provides current, practical and technical content on issues relevant to sports turf managers, including facilities managers. Most readers are athletic field managers from the professional level through parks and recreation, universities.

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Page 13 of 51

www.spor 14 // October 2017 T opdressing is the process of applying a thin layer of sand, soil, or some other fi nely granulated material such as compost to the surface of an established turf area. While topdressing has generally been practiced on golf course greens to provide the best putting surface, it can be a useful practice on sports fi elds as well. Topdressing can be an effective way of improving the turf surface, but it is very diffi cult to do properly. In fact, it is done wrong far more often than it is done right. The biggest problem with topdressing is forming layers in the soil that act as barriers to grass rooting (Figure 1). Once these layers are formed, they can be nearly impossible to remedy, short of reconstruction. The proper application of topdressing has many positive benefi ts. It can reduce an existing thatch layer or prevent thatch from building up. Thatch is broken down by microbial activity. For microbes to work on thatch, there has to be enough moisture and oxygen in the layer. Topdressing opens the layer up to moisture and air movement and contributes microbes to the process. It is one of the most effective ways of controlling thatch. Additions of a very light topdressing of sand during the season can help manage the slick layer that forms on the playing fi eld surface. This can be especially useful in overseeded bermudagrass athletic fi elds, where a slick layer can develop near the soil surface. Topdressing is a great way to smooth the surface for sports turf managers who want a more uniform playing surface. Sometimes the soil on which the original turf area was constructed is just not suitable. Clay soils make a terrible media for managing sports fi elds. The addition of a coarser particle's over the more fi nely textured particle can help to improve water infi ltration and playability during periods of high moisture. It is possible to build up a new rootzone of sand with topdressing, but it has to be done right. Finally, topdressing can be used to cover seed or stolons, or to fi ll in spaces between sod rolls. It can be a very effective way of growing-in a new turf area. Rules There are some basic rules to follow when developing a topdressing program. Generally, choose a topdressing that matches the underlying media. This assumes, of course, that the underlying media is suitable for growing grass. If the fi eld is sand-based, or sand- capped and the drainage is good, try to match the sandy media of the fi eld. Never seal off the fi eld with a layer of fi ne material, particularly a clay based soil or a smaller, particle-size sand (Figure 2). Layering of fi ne particles over a coarser material can result in a "perched" water table and water will not drain from the fi ne material into the coarser layer unless the layer of fi nes is saturated. This will prevent rooting into the coarser layer. Some fi elds with a history of poor topdressing practices can develop a series of layers of fi ne and coarser material one on top of another. Solving this problem may require reconstruction. If the fi eld is soil based and drainage is good, it would not be wrong to use a soil of similar texture to that in the fi eld. If the media in the exiting fi eld is unsuitable and the plan is to build up a new sand layer on top of it, be sure to have physical tests performed on the proposed media before the process begins. Also, make sure the sand is not rounded and has good gradation of sizes. First, it is important to have suitable surface drainage. If there is a THE ART OF TOPDRESSING // By ADAM THOMS, PHD AND NICK CHRISTIANS, PHD Figure 1. Buried sand layer can form a barrier to rooting. HERE IS THE MOST IMPORTANT RULE OF TOPDRESSING: ONCE YOU BEGIN, YOU CAN NEVER STOP. ONE OF THE MOST COMMON ERRORS IN TOPDRESSING IS TO START AND STOP AND THEN START AGAIN.

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