Fans are often
used to cool the turfgrass canopy on putting greens, typically cool-season
species such as creeping bentgrass and Poa
annua, but occasionally they are used on tees during periods of heat
stress. Air movement across a turf canopy has a very strong
influence on the overall health of the turf, especially in cooling of the plant
during hot and humid weather.
Research
shows that air currents of at least 3 miles per hour, but preferably closer to 6,
are needed across the playing surface to effectively cool turfgrass canopies.
Plants have a built-in cooling system whereby water transpires through small openings,
called stomata, in leaves and collects on leaf surfaces. This is similar to how
we perspire when sweat forms on our skin through pores. In the presence of air
movement, the moisture evaporates and cools the surface, the same for turf as a
golfer’s skin. Reduction in turfgrass canopy temperatures when airflow is
sufficient can be as much as 10°F or more, and soil temperatures are
consequently lowered as well.
Cool-season
turfgrasses generally perform best when soil temperatures are between 60 and 75°F. When soil temperatures reach 80°F or more, root and shoot growth is severely
restricted and at 86°F
or above root death begins. During stretches of extreme summer heat it is not
uncommon for soil temperatures to rise well into the 90s or above. Such
temperatures are simply too high for cool-season turfgrasses to endure for very
long and the turf goes into physiological decline.Left untreated or if a natural
cooling event does not occur, the turf will eventually die.
Keep in mind
that prevailing summer winds are usually from the south or southwest, so trees,
buildings or mounds blocking predominant summer airflow patterns can be devastating
to turf. Trees, shrubs and brush surrounding greens and tees should be removed
for this reason. However, when doing so still doesn’t allow for enough air
movement to maintain healthy turf through the summer or in the case of
buildings or surrounding topography that cannot be changed, the use of a fan to
mechanically generate air movement makes sense.
For more
information on fans, visit Using Fans in
the Northeast and The
Costs of Blowing Wind.