Many courses with bermudagrass fairways in Southern California do not overseed with perennial ryegrass, a strategy that is expanding into the Coachella Valley, southern Arizona and southern Nevada. This strategy allows for more-consistent playing conditions from late fall into the spring. However, superintendents must consider the potential damage from driving golf carts on dormant or semi-dormant bermudagrass during the winter months. In this update, I will address a few commonly asked questions about the impacts of traffic and overseeding on bermudagrass with the help of a research article published by Texas A&M University.
What are the impacts of golf cart traffic on overseeded and non-overseeded bermudagrass?
Traffic that was applied four times per week injured the non-overseeded bermudagrass at a rating ranging from 22% to 28% over two years. The peak injury in both years occurred from January through March. These ratings indicate that roughly 25% of the bermudagrass leaf blades were shredded from traffic. For reference, 100% injury would indicate bare soil. By comparison, turfgrass injury to the overseeded ryegrass was significantly lower – averaging 10% to 15% – with damage increasing as temperatures rose in March and April of each year.
Did traffic influence the amount of green color in the turfgrass canopy?
Routine traffic reduced green cover by about 15% in year one but only by around 3% in year two – when temperatures were warmer and the bermudagrass retained greater than 30% green cover through the winter. Other research has suggested greater deterioration of bermudagrass green cover due to routine traffic stress. Not surprisingly, overseeded areas had 65% to 80% green cover from January through March, significantly higher than the non-overseeded areas.
What other impacts are there from traffic?
Areas receiving traffic had slightly lower water content in the soil compared to non-traffic areas. This indicates that traffic was likely causing compaction, decreasing the soil's ability to hold water and increasing runoff.
How did traffic and overseeding affect bermudagrass recovery in the spring?
Routine traffic reduced the ability of bermudagrass to emerge from winter dormancy by about 10% in the non-overseeded areas. By comparison, overseeding with either perennial or annual ryegrass reduced bermudagrass spring emergence by 40% to 50%! This demonstrates the severe damage that overseeding can have on the understory of bermudagrass. Interestingly, overseeding with ryegrass also reduced the water content of the soil by about 5% compared to non-overseeded areas. This indicates that the overseeded turf, even during the low evaporative demand of winter, requires more water and results in greater water lost from the soil.
Ultimately this research demonstrates that traffic increases soil compaction and damage to bermudagrass leaf blades and slightly reduces the bermudagrass’ ability to emerge from winter dormancy. The study also confirms the severity of the damage that overseeding imposes on the understory bermudagrass and that even during the winter months, overseeded areas require more water inputs than non-overseeded bermudagrass.
While this update is not meant to encourage courses to restrict golf carts to paths all winter long, it should help to shed light on the damage imposed by golf carts. Any methods to reduce cart traffic on turf during the winter months – such as limiting foursomes to using two carts – should be strongly considered, especially if the turf is not overseeded.
West Region Agronomists:
Brian Whitlark, regional director – bwhitlark@usga.org
Ross Niewola, agronomist - rniewola@usga.org