Fan information
The
use of fans on pocketed and air movement restricted bentgrass greens is greatly
beneficial to turfgrass health. Although
many new varieties of bentgrass can tolerate higher air temperatures, bentgrass
will still only grow best in around 65 to 80 degree air temperatures. At Hermitage there are many different
microclimates that include slopes that block air and significant tree stands
that block air and sunlight.
Canopy
thinning, algae and moss growth along with greater susceptibility to mowing
damage and high moisture retention are all signs we have seen that relate to
poor air movement across our greens. In
most situations we have trees in such great numbers that taking them all down
would not only be a huge cost,but would also create huge controversy within the
membership. Fans are certainly not
substitutes for cutting down trees but they can be a much better solution to
the air movement problem.
Our
fans will usually run from Memorial Day to Labor Day. Anytime the air temperatures are stretching
past 80 degrees, our fans will most likely be running. However, when humidity remains below 30% or
so, we will keep the fans off. As air
temperatures move past 80 and humidity soars past 30%, the fans are kept on 24
hours a day. The squandering heat makes
it very difficult to grow bentgrass in sheltered environments. Fans help reduce surface and soil
temperatures while helping to dry the soil and reduce leaf wetness. All of these benefits reduce disease
pressure, increase wear tolerance and allow the plant a better chance to
photosynthesize.
Fan position is
extremely critical. A fans effective
throw of air is just about 120 feet. If
there is an area that is out of range from the 120 foot throw, it will
obviously not benefit from the increased air movement nearly as much and if at
all as the turf directly in front of the fan and within the 120 feet. It is very important to evaluate the throw
capability of the fan and to position the fan so that the specific throw length
can generously cover all the turf on the green.
Fans
are most effective at short range (under 50 feet) and then the benefits tail
off from there. In the heat of the day
(~1:00 pm) within 20 feet of the fan we can see up to a 12 degree drop in
surface temperature and a 7 degree drop with soil temperatures. From twenty to eighty feet we can see up to a
5 degree drop in surface temperature and very moderate drops in soil
temperature. Towards 120 feet and out there
is just about no significant change in temperatures. By placing irrigation flags or even ping pong
balls on the green surface, you can easily see where the fan is effective and
where it is not. Studying the prevailing
wind with a wind vane beforehand will aid in fan placement so that the fan will
not be fighting the slight breeze that may also be helping the turf
periodically.
Soil
temperatures are sustained through the day with the fan running. Drops in surface temperatures are only
sustained when the fan is directly pointed towards an area. With the oscillation of the fan, it can cover
the entire green but surface temperatures will fluctuate unlike soil
temperatures. Directly in front of the
fan, the surface temperatures can rise up to 5 degrees while the fan is pointed
in a different direction. As the fan
returns, temperatures will again go down 10-12 degrees in comparison to surfaces
without fan coverage.
The fan works by moving air across the turfgrass canopy to aid the opening of the plants stomates and subsequently cools the grass plant. The plants are not able to do this with little to no air movement during the heat. The reasoning for the fans on our course is the result of having trees in close proximity to the greens surface. Morning sun is blocked and the plant is not able to perform photosynthesis for a long enough time to store enough carbohydrates to stay in the positive in times of stress. Once air temperatures are above 85 degrees, respiration will quickly exceed photosynthesis and stored carbohydrates start to be depleted. The shaded turf grows wide succulent leaf blades which results in a higher rate of mechanical injury as well as disease incidence. The fans aid in reducing leaf wetness in these areas and also allow the stomates to function properly. The layering in our greens amplifies the negative effects that heat has on bentgrass that holds water in the top profile. The cooling effects of the fan help cool the plant and allow it to survive. By reducing root zone and surface temperatures, we are able to maintain quality bentgrass surfaces.
