Putting green management impact on golf cleat damage

Since the demise of metal spikes in the mid-1990s, some superintendents and golfers have protested that newer golf cleat and sole designs are too aggressive on their putting surfaces. Trade journal articles have quoted individuals claiming that some of these designs are worse than banned spikes from the past (5). Conversely, some golf courses in similar regions have not reported any putting surface disruption caused by any of the cleat or sole designs.

Given this problem, there is a need for scientific evidence regarding how putting green management may affect the visual wear damage (VWD) caused by foot traffic. We conducted a two-year study to quantify the impact of putting green management on wear damage caused by foot traffic. The objectives of the research were to identify putting green management practices that minimize or increase wear damage caused by golf shoes. Common putting green management practices that may affect VWD are grooming, rolling, sand topdressing and nitrogen fertility. We used golf shoes made with thermoplastic elastomer outsoles and a cleat arrangement suggested as damaging to putting greens (25).

Grooming uses a series of lightweight vertical blades that reach down to no more than 10 percent of the height of cut to remove horizontal runners, leaf blades and other organic matter (28). It has grown in popularity because it is less invasive than verticutting, yet shares the goal to encourage vertical growth in the plant. However, research validating the practice of grooming is limited.

A combination of vertical mowing and grooming that followed core cultivation resulted in a decrease in organic matter buildup on creeping bentgrass putting greens by 19 percent (16). In Tennessee, reel mowing in combination with grooming reduced the percentage of green cover on the majority of rating dates in one year of the study (23). While grooming blades may help encourage upright growth, some believe grooming leads to scalping compared to other practices that could promote upright growth (27). Even though putting green mower manufacturers offer groomers, it appears there is minimal data to substantiate their impact on wear damage caused by foot traffic.

In 1901, greenkeeper Walter Travis wrote, “From May until October, each green should be rolled daily with a light roller, rather than once or twice a week with a heavy one” (26). For the next quarter of a century, numerous publications addressed roller frequency, weight, compaction and soil texture (1, 10, 13) without coming to any definite conclusions. Shortly after that, the practice of frequent rolling ceased as turfgrass research showed a link between high levels of soil compaction and turf root growth (7, 11).

Lightweight rolling enjoyed a limited resurgence in the late 1980s because it was an effective way to increase green speed for tournament play (6). However, concerns that regular rolling would increase compaction, leaf bruising and disease still limited its use (2). Frequent rolling on greens did not become a common practice until research concluded that greens rolled three times per week decreased dollar spot, localized dry spot and broadleaf weeds, with no measurable negative effects (17). However, it remains questionable if frequent rolling has an impact on wear damage caused by foot traffic.

Old Tom Morris of Saint Andrews, Scotland, was first to suggest the practice of sand topdressing. He observed healthier turf after a windblown sand dusting or a spilled wheelbarrow of sand on a putting green (3). Historically, sand topdressing was applied once or twice per year with shovels, often following core cultivation.

The combination of lower cutting heights on newer cultivars was the impetus for sand topdressing equipment that could precisely apply small quantities of sand every one to two weeks. Light, frequent sand topdressing helps smooth the putting surface, control thatch and provide a firm playing surface (21). Research indicates that frequent sand topdressing can enhance the recovery from anthracnose (14) or lessen the severity of dollar spot (9). Since sand topdressing provides a firmer playing surface, the practice could decrease wear damage from foot traffic.

Nitrogen fertility influences putting green quality and growth rate more than any other nutrient (22). It was once customary to apply granular nitrogen every month at amounts as high as 1.0 pound per square foot (20). In the 1990s, concerns about picking up granular fertilizers on putting surfaces grew amidst decreasing cutting heights, which eventually led to an increase in foliar fertilization (15).

A survey in 2016 indicated that 99 percent of golf course superintendents in the United States used foliar fertilizers as part of their fertilization program on putting greens (24). In a fertilizer carrier study, foliar fertilizer treatments did not deplete soil nutrient levels following three years of applications. Furthermore, the biweekly use of foliar fertilizers resulted in better turf quality than monthly granular fertilizer applications (29). While higher nitrogen rates are known to increase recuperative potential, it is questionable if nitrogen rates have an impact on wear damage immediately following foot traffic.

It is not clear how these cultural practices affect wear damage from foot traffic on intensively managed putting greens. Therefore, the main objective of this research was to determine how current putting green management practices such as frequent grooming, sand topdressing, rolling and foliar nitrogen fertility affects wear damage resulting from foot traffic with aggressive golf shoes.

Materials and methods

We managed the research putting greens at Michigan State University (MSU) and the University of Arkansas (UARK) under identical cultural and mechanical practices. Management treatments included the following:

• Grooming (none vs. three times weekly at a depth of 0.04 inches)
• Lightweight rolling (none vs. three times weekly) with Tru-Turf greens roller
• Sand topdressing (none vs. every other week at the rate of 0.12 cubic yard per 1000 ft²)
• Nitrogen (N) fertility (low N vs. high N) spray applications urea every 14 days at the rates of 0.12 to 0.24 pound per 1000 ft².

The experiment was a four-factor, split-strip plot design with three replications. We subdivided the main plot factor (grooming) into strip plots for nitrogen fertility, sand topdressing and rolling treatments.

Nitrogen rates in this study were higher than would typically be applied to mature creeping bentgrass golf greens due to the lack of maturity of the putting surfaces and root zones at both sites. In 2015, we seeded creeping bentgrass at both locations into a USGA root zone. The experiment at MSU was on a 10-month-old Declaration creeping bentgrass green, whereas a nine-month-old stand of Pure Distinction creeping bentgrass was at UARK.

The treatments started in May of 2016 at both sites. Visible wear damage caused by foot traffic was evaluated monthly three to five times at each location during both years of the study. In a predesignated 1-square-meter area within each plot, we provided foot traffic. Each of the predesignated traffic areas had traffic by individuals simulating rounds of golf by mimicking a golfer retrieving a ball from the bottom of a cup (12).

Foot traffic was applied in random order by several individuals at each site, and each plot received 20 simulated rounds of golf. The golf shoe tested had thermoplastic elastomer outsoles with a cleat arrangement known to cause wear damage to golf green surfaces (25).

Following traffic, VWD was rated by up to four individuals using the following scale (19):

1 = Excellent; no visible traffic
2 = Very good; I think I see foot traffic
3 = Good; some visible foot traffic, but I would not mind putting on the surface
4 = Fair; visible foot traffic that would likely deflect my putt
5 = Poor; terrible putting conditions, and I recommend banning the cleat/sole from our golf course

Other data collection included monthly surface firmness measured with a Tru-Firm (Spectrum Technologies) and volumetric moisture content (VMC) obtained from a 1.5-inch depth using a TDR 300 equipped with turf rods (Spectrum Technologies).

Summary of results

There were significant interactions among treatments and locations and years, so the wear data were analyzed and are presented separately for each location and year. Rolling increased VWD damage significantly at UARK in both years and MSU in 2017 (Table 1).

Sand topdressing consistently decreased VWD from foot traffic and is most likely the result of an organic matter dilution that occurs with the practice. The results indicate grooming can be beneficial in minimizing VWD (Table 2).

Nitrogen fertility, and perhaps increased growth that derives from higher nitrogen rates, interacted with grooming in this study, which complicates the recommendation to groom for minimizing VWD (Tables 2 and 3). However, nitrogen rates in this study were higher than what mature, cool-season putting greens would usually receive due to the immaturity of the research greens in this experiment. Perhaps, on older putting greens with lower nitrogen rates, grooming might consistently result in decreasing VWD as it occasionally did in this study.

Regarding the nitrogen rate affecting VWD, when significant differences occurred, the higher rate resulted in more visible wear than the lower amount. As a result, it seems pertinent to recommend using cleatless golf shoes on immature putting surfaces because the research shows they result in the least VWD (25), and immature putting surfaces should be receiving higher rates of nitrogen (4).

A compelling result from the study was the increased VWD on rolled plots. At MSU, rolling resulted in significantly firmer surfaces during both years of the research, but there were no significant differences at UARK regarding surface firmness in either year. A closer look at the data suggests the increased VWD on rolled plots was most likely due to an increase in VMC at the sites (Table 1).

Volumetric moisture content was higher in both years in rolled plots at UARK and increased visible wear. At MSU, rolling resulted in no significant differences in VMC or VWD in 2016 but result in significant differences for both in 2017.

Previous research has concluded that rolling increases VMC, which decreases localized dry spot and dollar spot (8, 20). Therefore, the increase in VWD on rolled plots in this study may be due to the experimental design that did not allow for decreased irrigation on rolled plots.

These results emphasize the importance of utilizing a moisture meter during a frequent rolling program to help minimize irrigation afforded by the practice, which, in turn, can reduce VWD.

Additionally, even though irrigation was not a treatment in this study, there was a positive correlation with VWD and VMC in the top 1.5-inch depth of the root zone.

This research demonstrates that cultural practices can affect VWD on highly managed creeping bentgrass putting greens. These results will help golf course superintendents maximize golfer satisfaction. It would be beneficial to conduct similar research on other common types of intensively managed putting green surfaces, such as annual bluegrass (Poa annua) and ultradwarf bermudagrass (Cynodon dactylon x C. transvaalensis).

Research Takeaways

• Damage from golf cleats has become more noticeable with smoother putting green surfaces.
• Regular sand topdressing and grooming reduced visible damage from golf cleats.
• Higher nitrogen fertility and rolling increased visible damage from golf cleats.
• When rolling led to an increase in volumetric moisture content, it increased visible damage from golf cleats, which stresses the importance of monitoring soil moisture with sensors (or TDRs).
• There was a correlation between visible wear damage from simulated golfer traffic and the volumetric moisture content in the surface of the putting green root zone.

Thomas Nikolai, Ph.D., is a senior turfgrass academic specialist in the Department of Plant, Soil and Microbial Sciences, Michigan State University, and can be reached at nikolait@msu.edu. Doug Karcher, Ph.D., is a turfgrass soil specialist and professor in the Department of Horticulture, University of Arkansas, and can be contacted at karcher@uark.edu.

Acknowledgments

This research was funded in part by the U.S. Golf Association Green Section Research Program.

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