Application conditions influence turf colorant performance

When painting and athletic field are mentioned in the same sentence, we most commonly think of those freshly painted lines and logos that athletic field managers spend countless hours perfecting for the next sporting event. However, painting fields may be about nothing more than making the surface green. Painting bermudagrass athletic fields with turf colorants has become a common practice to enhance winter color of heavily trafficked overseeded athletic fields as well as low-use non-overseeded fields.

The use of turf colorants rather than overseeding reduces agronomic inputs and can result in a more predictable spring green-up. Whether turf colorants are used to accentuate the natural green color of an actively growing turf or simply to provide color during winter months, it is important to apply these products at the ideal time to maximize product functionality while minimizing the potential for problems.

Types of products for specific uses

Generally, colorant products fall into three categories: paints, “pigments,” or dyes. In simple terms, the difference among these categories involves the amount of binder and pigment ingredient in the product. Binder creates adhesion of pigment to turfgrass leaf blades, suggesting its importance in regard to product longevity. The extended life of paints can be attributed to increased levels of binder, which are typically resin based. Paints have binder amounts that usually comprise between 10 to 40% of the concentrated product, whereas the pigments have much lower amounts of binder. Paints contain mostly insoluble pigments designed for opacity compared to pigments and dyes that have soluble organic pigments that provide color with very little opacity. These products between paints and dyes are often termed “pigments” by the turfgrass industry. The term “pigments” thus refers to low-binder products that have the opacity characteristics of paints. The products with a higher percentage of binder (but less than that of paint) are often termed as “colorants” by the turfgrass industry. There are many different products on the market and knowledge of product formulation can be very beneficial to athletic field managers when selecting a colorant for application.

Air temperature at colorant application

Our research has identified great variability in measured color parameters and physical properties among turf colorants. For example, vast differences in fluid viscosity of turf colorants suggest colorant formulation may influence colorant performance. During some of our earlier trials, we found certain products were prone to tracking as well as extensive off-target staining during the application process. Athletic field managers have enough field issues to worry about without the concern for staining of athlete uniforms. To better characterize products for staining potential, we developed techniques that allow us to evaluate turf colorant transfer onto absorbent materials similar to athlete uniforms.

Throughout the past few years, we have screened more than 30 products for colorant transfer potential. As expected, results have varied substantially among the products tested. Some products transfer non-discernable amounts of colorant one day after colorant application, while two products stained cloth at unacceptable levels up to 6 weeks after application. Elevated levels of colorant transfer multiple weeks after colorant application has been the exception as even the poor-performing products produced acceptable transfer levels by 14 days following application. Considering those results, a product that has increased colorant transfer potential can still be a viable option for field managers if applied far enough in advance of a sporting event. If the product is applied well in advance of an event, the additional time under traffic may risk reduced quality of color. However, the reduced paint quality may be a necessary sacrifice for most field managers in order to minimize the risk of excessive uniform staining.

Our most recent colorant transfer trials have focused on air temperature at the time of colorant application. During an earlier product evaluation trial, we observed colorant transfer levels that were much higher for all products tested during year 1 compared to year 2. The temperatures during year 1 were much cooler, which led us to believe that air temperature may influence colorant transfer. After further investigation, our research has shown that air temperature during colorant application can greatly influence the product’s ability to adhere to the turf foliage. Specifically, when applied at temperatures below freezing, colorant transfer from leaf tissue onto absorbent material more than doubled compared to when colorant was applied at 45°F.

If transfer is a concern, a field manager may not want to apply these products when frost is present or air temperature is less than 45°F as severe staining of athletic uniforms can have significant cost ramifications. This causes a bit of a dilemma for athletic field managers because most turf managers that have used turf colorants agree that visual paint quality is increased when there is frost present during colorant application. However, the lower temperatures required to produce frost can promote greater colorant transfer. For most products, once the air temperature warms the colorant further dries and has increased adherence to the turfgrass. Turf managers also risk producing tire marks when applying colorants when frost is present. We have yet to test the influence of frost on subsequent visual paint quality, but recognize that it is very popular among golf course superintendents. We caution athletic field managers to plan applications far enough in advance of sporting events to minimize transfer potential if frost is desired at application.

Leaf wetness at colorant application

During the previous two winters, we tested wetting the dormant leaf blade prior to colorant application to evaluate any influence leaf wetness may have on colorant quality and coverage. The results have varied, and have been mostly product dependent. We have found that the quality of colorant-treated turf following the application of products with lower viscosities is not greatly influenced by leaf wetness at the time of application. Conversely, we have seen where leaf wetness can improve quality of the colorant application when using products that are of higher viscosity. Products with lower viscosities spread more evenly across the dormant leaf blade, whereas higher viscosity products almost have a speckled look when examining at a microscopic level.

Although the speckled look is not visible at eye level, you are able to see improved colorant coverage and quality when applying a light application of irrigation before treating with higher viscosity colorants. Something else to keep in mind is that as the turfgrass becomes more dormant, the leaf tissue becomes drier. Supplemental water (irrigation) will increase leaf moisture and the added moisture will reduce the applied colorant from absorption into the leaf tissue. This can increase the colorant’s coverage and improve color. While leaf wetness is usually accomplished with a quick syringe cycle from the irrigation, some people have waited to apply the colorant after a light rainfall or even early in the morning with the presence of dew. Be aware that too much irrigation or rainfall can cause puddling that can dilute the application and result in an undesirable appearance.

Maximizing colorant functionality

Making timely applications should be a primary concern for all athletic field managers who use turf colorants. Choosing the best product is difficult since not one product has significantly outperformed the rest in all our evaluations. However, one can mitigate product shortcomings by applying them under the ideal environmental conditions. For example, managing colorant transfer can be difficult for athletic field managers, especially those who maintain fields at the recreational level. Applying products in warmer air temperatures will help prevent elevated levels of colorant transfer onto athlete uniforms. We would also recommend using products that are of higher viscosity. The increased binder in these products will help retain colorant pigment on the leaf blade rather than dislodging onto an athlete’s uniform. Keep in mind that products higher in viscosity often do not produce the best paint coverage. Applying a quick irrigation cycle prior to colorant application or applying when there is dew present can help mask coverage deficiencies.

As mentioned before, there are a number of colorants now available. Some are more appropriate for specific uses, while others can be considered general use products. The best way to identify how to use these products requires a bit of experimentation by the turf manager under each unique situation. However, applying colorants under the conditions mentioned in this article can help improve the quality of the painted surface while enhancing the functionality of the colorant treated field by decreasing the risk of colorant transfer onto athlete uniforms.

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Drew Pinnix is a graduate research technician, and Grady Miller, PhD, is professor and Extension turfgrass specialist at North Carolina State University in Raleigh.