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.
Issue link: https://read.dmtmag.com/i/282941
32 SportsTurf | April 2014 www.sportsturfonline.com M owing is one of the most important cultural practices for maintenance of a healthy turf. Proper mowing height increases turfgrass density and promotes deep root growth, both of which lead to a stronger turf that is more competitive against weeds and better able to persist under environmental stresses. Two important components of mowing are cutting height and frequency. Both of these factors depend on the turfgrass species, util- ity of the grass, cultivar, and the level of lawn quality desired. Other important considerations are clipping disposal, mowing equipment and mowing safety. MOWING HEIGHT The optimum cutting height is determined by the growth habit and leaf width of the turfgrass species. Grass species that have fine textured (narrow) leaf blades and that grow horizontally can usually be mowed shorter than an upright-growing grass with coarser (wider) leaf blades. For example, bermudagrass and creeping bent- grass are mowed at low heights because of their numerous narrow leaf blades and low growth habit (Figure 1). In contrast, St. Au- gustinegrass is mowed at higher heights because it has coarse-tex- tured leaf blades. Turfgrass undergoes physiological stress with each mowing event, particularly if too much leaf tissue is removed (Figure 2). Scalping, or removal of too much shoot tissue at one time, can produce long- term damage to the turf. This can leave turf susceptible to other stresses such as insects, disease, drought, and sunscald. Mowing also influences rooting depth, with development of a deeper root system in response to higher mowing heights. Advantages of the deeper root system are greater tolerance to drought, insects, disease, nematodes, temperature stress, poor soil conditions, nutrient deficiencies and traffic. Repeated mowing below the recommended heights for each species is a primary cause of turf injury and should be avoided. It is also important to not mow at higher than the recommended heights, as this may result in increased thatch. MOWING FREQUENCY Mowing frequency is determined by the growth rate and the utility of the grass. The growth rate is influenced by grass species, time of year, weather conditions, and level of management. In the south, grass may need year-round mowing, while many parts of the country only mow in spring, summer and fall. Grass that re- ceives repeated athletic use will need more frequent mowing to reduce potential injuries and to improve the playing surface, while low maintenance lawn areas would need less frequent mowing. Some species, such as bahiagrass, often require mowing for seedhead removal rather than for leaf blade reduction. Grass should be mowed often enough so that no more than 1/3 of the blade height is removed per mowing (Figure 3). For example, if recommendations call for a 2" mowing height, the grass should be mowed when it gets to 3" in height. It is impor- tant to always leave as much leaf surface as possible so that photo- synthesis can occur, particularly in a grass that is subject to environmental or site stresses. CLIPPING DISPOSAL The function that the grass serves will often determine whether clippings are left on the ground or removed. Grass clip- pings contain nutrients and organic matter that is broken down by soil microbes. The nutrients can be taken up by the turf and reused and the organic matter will contribute to the soil. Because they are readily decomposed by microbes, clippings do not gener- ally contribute to thatch. On some surfaces, such as athletic fields and golf greens, clippings are generally not desirable and are usu- ally bagged. In these cases, the clippings can be composted. THE IMPORTANCE OF MOWING Field Science | By Laurie E. Trenholm, PhD Figure 1. St. Augustinegrass (on the left) has coarse leaf blades and requires a higher height of cut. Bermudagrass (on the right) has much finer leaf blades and can be mowed at much lower heights. Credit: Claire Lewis Figure 3