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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18 SportsTurf | October 2016 www.sportsturfonline.com FIELD SCIENCE on plant health and may vary based on a particular setting. Without adequate photosynthesis the plant cannot maintain necessary metabolic functions. Athletic paint coating the pores (stomata) on turfgrass leaf surfaces compounds the issue. If the plant cannot freely lose water and take in carbon dioxide from these pores, then canopy temperatures can rise to become an additional stressor. The color of athletic paint can have a great effect on turfgrass transpiration. In unpainted bermudagrass, water loss increases with canopy temperatures, but it was just the opposite with painted leaves. We typically found that the darker colors affected transpiration to a larger extent. Turfgrass coated with lighter colors such as white, yellow, and orange had similar but slightly lower transpiration rates than the unpainted turfgrass. The darker colors including red, blue, and black showed much higher canopy temperatures and much lower transpiration rates. These results mirrored what we saw with total canopy photosynthesis in that the darker colored athletic paints have a greater negative effect on turfgrass physiological processes. SHADING NOT ALL BAD It is important to note that shading by paint pigments may not always be detrimental. Cool-season grasses grown in northern climates often do not use all of the light that is possible for photosynthesis. For example, ryegrasses have a relatively low light requirement and the daily light integral on athletic fields with little to no shade may be sufficient to drive adequate growth, even when accounting for shading effects by paint. Furthermore, regular use of the field and mowing may remove some of the paint from the leaf's surface. The plant will also generate new growth that is more efficient at utilizing the light. Of course, the next coat of paint may soon follow the emergence of this new growth. The result is that chronic paint use, especially darker colors, is even more damaging. We looked at application rates and timing in relation to mowing. The results indicate that earlier removal of the paint is beneficial to the plant. We found that one less mowing during the week provided faster recovery. Although a higher frequency of mowing would suggest that more of the paint is being removed from the turfgrass leaf blade, the area of the plant that is not coated with paint (new growth) is also being mown off. Allowing new tissue that is not coated with paint an extra day to expand will increase the leaf area that is able to actively photosynthesize and as a result, promote faster recovery. The timing of athletic paint application had a greater effect on the quality of the painted surface compared to recovery of the turfgrass over time. As expected, earlier applications of paint were of reduced quality compared to applications made later in the week (closer to game day). Furthermore, we found that paint applications made earlier in the week may minimally increase turfgrass recovery, but not to the degree that would merit sacrificing the overall appearance of the paint application. As mentioned before, an athletic field manager may need to balance plant health and quality of paint appearance. Also some limited work on binder concentrations looked very promising for alternative formulations that would be less damaging. Remember that binder is the ingredient in paint formulations that is responsible for the paint's ability to adhere to the leaf blade, so manipulating the concentration of binder can affect how long the paint will "stick" around. One issue that must be addressed when looking at alternative formulations in terms of binder concentration is the susceptibility of the paint to transfer onto an absorbent material, i.e., an athlete's uniform. This can be very problematic as this may result in increased staining of uniforms. The severity of this issue may be anywhere from minor laundry matter or as severe as a need for total uniform replacement. The painting of athletic fields is a ritual that has evolved tremendously as sports have become more and more popular over the years. Not only are athletic paints needed for boundary lines and other field markings for playability of the game, paints are also needed for advertising logos and brand marketing. Logos may not be required for successful completion of a sporting event, but at the time of high-definition television and major companies seizing opportunities to market their brand, athletic field painting will continue to be a major part of athletic field management. We have identified some of the underlying negative effects that athletic field paint has on natural turfgrass surfaces. While there is not much likelihood of teams changing their colors to help minimize turfgrass decline, there are ways to help combat the harmful effects. This article is reprinted with permission from Sports Turf Canada; it first appeared in the Summer 2016 issue of their Sports Turf Manager publication. Grady L. Miller, PhD, is professor and Extension turf specialist, Crop and Soil Sciences Department, North Carolina State University; Drew Pinnix is a graduate student in crop science at NC State; and Casey Reynolds, PhD, is an assistant professor and Extension turfgrass specialist, Texas A&M University. School-painted logo at football stadium.