There is an old sentiment among golf course superintendents and greenkeepers: The golf course would be easy to maintain if it were not for the golfers! The putting green is the most intensively managed and scrutinized part of the golf course, and greens experience the most traffic. Everyone walks onto those greens, repeatedly.
Foot traffic can damage a green by causing physical wear and tear to the playing surface and by contributing to soil compaction, which leads to root injury. Root dysfunction means reduced water and nutrient uptake. This damage can lead to thinning turf, inconsistencies with the putting surface and a decline in overall quality and playability, especially in high-traffic areas around walk-on/walk-off sites.
Various agronomic practices are relied upon to maintain the best putting green conditions. The purpose of grooming is to promote upright turfgrass growth for a smoother, faster, more uniform playing surface. Grooming is defined as using brushes or shallow vertical blades to remove lateral growth and excess top growth without significantly disturbing the putting surface. Grooming is considered less invasive than verticutting. Several years ago, lightweight rolling was primarily used to alleviate frost heaving, prepare seed beds or increase green speed. Today, lightweight rolling is an accepted practice that contributes to maintaining healthy turfgrass and a playing surface golfers can appreciate. The practice of sand topdressing smooths and firms the putting surface and mitigates thatch. Nitrogen fertility influences turfgrass growth rate and putting green quality more than any other nutrient.
How does grooming, lightweight rolling, sand topdressing and nitrogen fertilizer affect surface wear caused by foot traffic on a putting green? A field study investigated the relationship among those four factors for their influence on the playing surface of a putting green. To put these four factors and their interactions to the test, this study was conducted from mid-spring through autumn for two consecutive years at two locations.
The Michigan site was 10-month-old Declaration creeping bentgrass (Agrostis stolonifera), and the Arkansas site was 9-month-old Pure Distinction creeping bentgrass. Both sites consisted of USGA-recommendation, sand-based root zones, mowed at 0.125 inch (3.2 millimeters) and irrigated to prevent drought stress. Grooming treatments consisted of none versus three times per week at a depth of 0.2 inch (0.5 millimeter). Lightweight rolling was none versus three times per week. Sand topdressing was none versus every 14 days at 14.75 gallons per 1,000 square feet (0.6 liters per square meter). Nitrogen was applied as liquid urea (46% nitrogen-0% P2O5-0%K2O) at none versus 0.12 or 0.24 pounds nitrogen per 1,000 square feet (0.6 or 1.2 grams nitrogen per square meter) every 14 days. Foot traffic was frequently simulated by several individuals wearing the same model golf shoe, and visible wear damage was measured among all test plots.
To say there was a “ton” of data collected is an understatement. The data revealed sand topdressing consistently decreased visible wear damage from foot traffic. The researchers indicated this was likely due to organic matter dilution. Overall, grooming helped to minimize visible wear damage. More visible wear damage was observed with the higher nitrogen rate; however, the nitrogen application rates in this study were higher than mature creeping bentgrass greens would normally receive because these greens were less than 1 year old.
Rolled plots had firmer surfaces at the Michigan site; however, rolled plots had more visible wear damage at the Arkansas site, and this was attributed to higher soil moisture content. While rolling can increase soil volumetric water content, the researchers of this study emphasize the importance of monitoring soil moisture during a frequent rolling program to assist in minimizing irrigation inputs, which can minimize visible wear damage.
This research demonstrated that cultural practices of grooming, lightweight rolling, sand topdressing and applying nitrogen fertilizer can affect visible wear damage from foot traffic on creeping bentgrass putting greens. These interactions are complicated, thus difficult to summarize due to many interconnected parts, and implies no simple solution exists. For the golf course superintendent and greenkeeper, it’s just another day working in harmony with nature … and golfer expectations.
Source: Nikolai, T.A., D.E. Karcher, A.D. Hathaway and D. O’Brien. 2021. Impact on putting green management on visible wear damage caused by foot traffic. Agronomy Journal 113:3771-3777.
Mike Fidanza, Ph.D., is a professor of plant and soil science in the Division of Science, Berks Campus, at Pennsylvania State University in Reading, Pa. He is a 24-year member of GCSAA.