Key Takeaways

• Foot traffic on a frost-covered annual bluegrass putting green did not cause a reduction in turfgrass quality.
• Daily golf cart traffic on frost-covered creeping bentgrass, annual bluegrass and perennial ryegrass fairways consistently reduced turf quality compared to the no-traffic control. When morning temperatures were below freezing, repeated cart traffic in the afternoon also caused damage, even if frost wasn’t present.
• Rolling annual bluegrass putting greens on the mornings of frost events led to a reduction in turf quality.
• Analysis determined that morning soil temperature was the most effective parameter for predicting annual bluegrass rolling injury, with unacceptable injury occurring when morning temperatures were less than 32 degrees F.
• Regardless of whether frost was present or not, the most-accurate predictor of traffic injury during cold weather was morning soil temperature. These findings suggest that cart traffic and rolling should be avoided on days when soil temperatures are below freezing.

These results suggest that allowing a limited number of golfers to putt while frost is still present wouldn’t result in any injury to an annual bluegrass green in this environment. This finding runs contrary to long-standing recommendations to implement frost delays to protect putting greens from foot-traffic damage. However, it is important to note that this finding applies only to foot traffic and only to annual bluegrass putting greens. The impact of foot traffic on creeping bentgrass and perennial ryegrass is currently being investigated and it’s possible that other species may not have the same level of tolerance. As we discuss next, there are also implications from cart traffic and maintenance equipment that need to be considered. However, if no putting green maintenance was planned on a frosty morning and a limited number of golfers were going to walk and not take carts, a frost delay may not be necessary. We recommend testing the impact of foot traffic on frost-covered turf at your specific location before making any changes to your frost delay policy.

Effects of Daily Cart Traffic on Fairways in Winter and During Periods of Frost

Research was conducted in January and February of 2022 to investigate the effect of daily winter cart traffic on a creeping bentgrass fairway, including during periods of frost. In 2023, the study was expanded to include annual bluegrass and perennial ryegrass fairways and will be ongoing through 2025. Cart traffic is applied using a Club Car Turf Carryall 2 utility vehicle driving onto individual plots either one or seven times. Frost was observed on the fairways in January and February when cart traffic was applied in the morning (8:00 a.m.), but frost was never observed when traffic was applied in the afternoon (1:00 p.m.).

2022 Results

It was found that as little as one pass of cart traffic during a frost event produced noticeable damage on a creeping bentgrass fairway. Seven passes with the cart on a frost-covered bentgrass fairway resulted in significantly more visual injury that persisted for over two weeks. Interestingly, even without frost, seven passes of the golf cart still reduced creeping bentgrass quality (Table 1). This highlights the importance of managing cart traffic in the winter since fairway turf has a reduced ability to recover from wear and tear.

2023 Results

In 2023, annual bluegrass and perennial ryegrass were added to the study to further investigate the effects of daily winter cart traffic on fairway turf. The research was again conducted in January and February and frost was observed on multiple mornings.

On the creeping bentgrass fairway, reductions in turf quality resulted when cart traffic was applied at both 8:00 a.m. and 1:00 p.m. (Figure 1). In general, both cart traffic treatments caused a similar reduction in turf quality compared to the no-traffic control plots. Correlation analysis between turfgrass quality and environmental factors determined that morning soil temperature was the most effective parameter for predicting cart traffic injury on bentgrass. When morning soil temperatures are less than 32 degrees F, traffic applied in the morning or afternoon will result in bentgrass injury at unacceptable levels. The presence or absence of frost, afternoon soil temperature, morning or afternoon air temperature, and morning or afternoon volumetric water content were poorly correlated with turfgrass quality and thus not good predicters of cart traffic injury. When compared to the no-traffic control, cart traffic had more of an impact on creeping bentgrass turf quality than on annual bluegrass and perennial ryegrass.

On the annual bluegrass and perennial ryegrass fairways, frost events were followed by reductions in turf quality when cart traffic was applied at 8:00 a.m. and 1:00 p.m. From January 25 to February 13 the 8:00 a.m. cart traffic regularly reduced annual bluegrass turfgrass quality compared to the 1:00 p.m. cart traffic. Again, correlation analysis determined that morning soil temperature was the most effective parameter for predicting annual bluegrass cart traffic injury. When morning soil temperatures were less than 32 F, traffic applied in the morning or afternoon caused injury to annual bluegrass fairways. However, with perennial ryegrass, unacceptable injury occurred when traffic was applied with morning temperatures less than or equal to 35 F. The lowest quality ratings of any species during the study came from ryegrass, with a turf quality of 4.0 on February 6th and 8th.

Effects of Daily Rolling on Annual Bluegrass Putting Greens in Winter and During Periods of Frost

As part of the ongoing research project, a study was conducted from January 2 to February 28, 2023, to investigate the effects of daily rolling applied to an annual bluegrass putting green. Rolling treatments were applied with a Tru-Turf 48-inch roller.

Results

On the annual bluegrass putting green, frost events were followed by reductions in annual bluegrass quality when rolling was applied at 8:00 a.m. and 1:00 p.m. From January 25 to February 17 the 8:00 a.m. rolling reduced annual bluegrass turfgrass quality when compared to the 1:00 p.m. rolling. As with cart traffic on fairways, correlation analysis determined that morning soil temperature was the most effective parameter for predicting injury from rolling. With annual bluegrass, unacceptable injury occurred when rolling was applied at morning temperatures less than or equal to 32 F.

Years 3 and 4 (2024 and 2025) Research Objectives

The results in this article are an update on the ongoing research project at Oregon State University. In 2024 and 2025, cart traffic treatments on the three cool-season grasses will continue and rolling applications on the annual bluegrass putting green will also be repeated. Of note is the addition of daily morning and afternoon foot-traffic studies on creeping bentgrass and perennial ryegrass. This is important since foot traffic on these species was not evaluated in the 2022 trial and it is vital for golf course superintendents to know if other species besides annual bluegrass are tolerant of foot traffic during frost conditions. The type of shoes used to apply traffic has also been expanded to include slip-on waterproof work shoes. Weather data will also be collected in 2024 and 2025 and correlated with turfgrass injury. Early results from this next round of research indicate that morning and afternoon foot traffic applied on days with freezing soil temperatures in the morning produced slight damage to creeping bentgrass, but no damage to perennial ryegrass.

Conclusions

The finding that foot traffic on an annual bluegrass putting green during frost conditions did not produce visual turfgrass injury is significant. Although this could have implications for when golfers begin play, it’s critical to remember that this research shows that cart traffic does injure frost-covered or frozen turf, so cart restrictions would still be needed. Further complicating matters is the finding that maintenance equipment damages the greens during frost. Based on this, mowing, rolling and other practices would still have to be delayed even if golfers could potentially walk on the surfaces safely. Reconciling this issue requires either an adjustment to the level of putting green preparation or to the timing of that work – or both. It is ultimately up to each individual superintendent to make the right decision for their unique situation.