WCTA Funded Research - OSU Releases Frost Study Year 1 Report
Effects of Equipment Traffic on Turfgrass During Frost Conditions
Alec Kowalewski, Chas Schmid, Brian McDonald, Cole Stover, Zach Hamilton
Oregon State University
October 15, 2023 (Year 1 report)
Key Preliminary Findings:
• Cart traffic and rolling applied after mornings with freezing soil temperatures resulted in unacceptable turfgrass quality.
• Cart traffic and rolling applied in the morning and afternoon reduced turfgrass quality compared to no traffic or rolling on days when the soil temperature was below freezing.
• When morning soil temperatures are below freezing, traffic and rolling applied in the morning resulted in greater turfgrass quality reductions than traffic or rolling applied in the afternoon.
• Soil temperature was the greatest predictor of traffic injury and suggest that cart traffic and rolling should be avoided on days when soil temperatures are below freezing.
Background:
Cool-season (C₃ carbon fixation) turfgrass species such as annual bluegrass (Poa annua), creeping bentgrass (Agrostis stolonifera) and perennial ryegrass (Lolium perenne) are prominent on golf courses in northern climates (Bertrand et al., 2013; Tompkins et al., 2000; Tompkins et al., 2004). Classically, winter injury is associated with freezing temperatures and snow cover, or extremely cold and dry conditions with no snow cover. These conditions lead to turfgrass injury in a variety of ways such as direct freeze damage, crown hydration, desiccation, anoxia, and snow mold. In 2022 a USDA-SCRI grant in the amount of $8 million was award to Dr. Eric Watkins at the University of Minnesota and collaborators from 7 other universities in the United States, and Norway, to explore solutions to crown hydration, anoxia, and freezing temperatures (University of Minnesota Department of Horticultural Science, 2022). A cool weather concern not included in this exploration is the effects of traffic during frost conditions.
Frost is a concern on northern and transition zone U.S. golf courses in the fall, winter and spring (Ackerson, et al., 2015), and in places with moderate winter conditions like the coastal Pacific Northwest and southern U.S which allow for play in the winter months, which is 10,004 golf courses according to the 2017 Golf Course Environmental Profile (GCSAA, 2017). This concern has become more of an issue recently with the surge in golf over the past couple years, and the high demand for tee times, even during winter months. The United States Golf Association (USGA) currently has conservative recommendations with respect to frost delays, suggesting significant delays on mornings with frost due to the fact that it is not well understood what causes turfgrass injury, and the environmental conditions necessary for damage (USGA, 2015; USGA 2018; USGA Green Section Record, 2021). Current recommendations are to delay the start of golf until after the frost has melted. However, there has been significant pushback from golfers who are skeptical as to whether these delays are truly necessary. It is also poorly understood how turfgrass species, mowing height and source of traffic (foot traffic, cart traffic or maintenance equipment) affect injury during frost. Frost delays translate to significant reductions in revenue and valuable maintenance time which is often early in the morning prior to golfer arrival.
In response to these questions a series of preliminary studies were conducted at Oregon State University, Corvallis, OR in February of 2022 at the request of USGA Agronomy and Research staff. Results from these initial explorations determined that foot traffic, equivalent to 16 golfers on a putting green, applied during eight frost events in February did not produce visual annual bluegrass damage, or reductions in normalized difference vegetation index (NDVI) values. Findings from this initial work determined that as little as one cart pass on a creeping bentgrass fairway during a frost event produced noticeable damage. Considering these intial results, further exploration into the effects of golf cart, and golf maintenance equipment traffic, during frost is warranted.
Objectives:
• Evaluate the effects of daily winter cart traffic applied to a creeping bentgrass, annual bluegrass, and perennial ryegrass fairway.
• Evaluate the effects of daily winter rolling applied to an annual bluegrass putting green.
Year 1 Results:
Effects of daily winter cart traffic on creeping bentgrass
On the creeping bentgrass fairway, frost was observed on January 10, 11, 16, 30 and 31, and daily from February 1 to 17, 2023. On these dates frost was observed at 8:00 am and not 1:00 pm. Frost events were followed by reductions in creeping bentgrass quality when cart traffic was applied at 8:00 am and 1:00 pm (Figure 1, Image 1). On a few events in mid-February when the bentgrass was showing improved turfgrass quality, the afternoon traffic resulted in higher turf quality than the morning traffic. In late February no differences were observed between the 8:00 am and 1:00 pm traffic treatments. A series of correlation analysis comparing turfgrass quality to atmospheric temperature, soil temperature, and soil moisture content collected in the morning (8:00 am) and afternoon (1:00 pm) determined that morning soil temperature was the most effective parameter for predicting bentgrass cart traffic injury (Figure 2). More specifically when morning soil temperatures are less than 32 F, traffic applied in the morning or afternoon will result in bentgrass injury at unacceptable levels.
Effects of daily winter cart traffic on annual bluegrass
On the annual bluegrass fairway, frost was observed daily from January 30 to February 17, 2023. On these dates frost was observed at 8:00 am and not 1:00 pm. Frost events were followed by reductions in annual bluegrass quality when cart traffic was applied at 8:00 am and 1:00pm (Figure 3, and Image 2). From January 25 to Feb 13 the 8:00 am cart traffic regularly reduced annual bluegrass turfgrass quality compared to the 1:00 pm cart traffic. Again, correlation analysis determined that morning soil temperature was the most effective parameter for predicting annual bluegrass cart traffic injury (Figure 4). Again, when morning soil temperatures are less than 32 F, traffic applied in the morning or afternoon will result in unacceptable injury.
Effects of daily winter cart traffic on perennial ryegrass
On the perennial ryegrass fairway, frost was observed on January 16, and January 30 to February 17, 2023. On these dates frost was observed at 8:00 am and not 1:00 pm. Frost events were followed by reductions in perennial ryegrass quality when cart traffic was applied at 8:00 am and 1:00 pm (Figure 5). From January 25 to Feb 13 the 8:00 am cart traffic regularly reduced perennial ryegrass turfgrass quality compared to the 1:00 pm cart traffic. Again, correlation analysis determined that morning soil temperature was the most effective parameter for predicting perennial ryegrass cart traffic injury; however, with perennial ryegrass, traffic applied after morning temperatures of 35 F or less will result in unacceptable injury (Figure 6).
Rolling an annual bluegrass green
Effects of daily winter rolling on annual bluegrass
On the annual bluegrass putting green, frost was observed on January 9 and 10, and daily from January 30 to 17, 2023. On these dates frost was observed at 8:00 am and not 1:00 pm. Frost events were followed by reductions in annual bluegrass quality when rolling was applied at 8:00 am and 1:00pm (Figure 7). From January 25 to Feb 17 the 8:00 am rolling regularly reduced annual bluegrass turfgrass quality compared to the 1:00 pm rolling. Again, correlation analysis determined that morning soil temperature was the most effective parameter for predicting annual bluegrass rolling injury (Figure 8). With annual bluegrass, rolling applied after morning temperatures of 32 F or less resulted in unacceptable injury.
Future Research:
Morning and afternoon cart traffic treatments will be applied to the creeping bentgrass, annual bluegrass and perennial ryegrass fairways again from January 2 to February 28, 2024, and 2025. Rolling applications on the annual bluegrass putting green will also be repeated. Weather data will be collected in 2024 and 2025, and compared/correlated with turfgrass injury.
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