Limited air movement isn’t just a southeast or transition-zone problem August 16, 2011 By Adam Moeller and Brett Chapin, USGA

 Fan height is usually 10 feet or less to maximize air movement across the surface of the green. 




Imagine yourself playing golf with friends or family on a warm summer day.  Everyone is enjoying their rounds and then you get to that one green.  Suddenly the air feels stagnant and hot, you start to sweat more, your clothes stick to your body, and you can’t wait to get to the next hole where there always seems to be a nice cooling breeze.   Now imagine staying on that green the whole day, throughout the entire summer, with endless hot, humid days without any relief from a cool breeze.  Pretty miserable, right?  Well that’s exactly what the putting green turf suffers through when it is located in a microclimate that has limited air movement. 

The microclimates in which putting greens are located play a major role in the superintendent’s ability to produce good golf conditions.  Many articles have been published in the Green Section Record about the negative effects that shade has on putting greens, but only a few articles discuss the consequences of poor air movement.   

            Research and field observations are very clear that putting greens can be greatly improved with the use of fans because of the cooling effect on the turf canopy, soil temperature, and increased newsContent development (Duff and Beard, 1966; Guertal et al., 2005).  Fans also help to dry the soil and reduce turf leaf wetness duration, both of which reduce pathogen pressure.  Using a fan to dry the surface improves putting green wear tolerance, too.  Oppressive heat and humidity makes it next to impossible to grow healthy creeping bentgrass or Poa annua putting greens during the summer in the Southeast Region and Transition Zone if air movement is limited.  As a result, most golf courses in the Southeast that have creeping bentgrass or Poa annua rely on fans to keep putting greens healthy during the summer (O’Brien, 2009).   

Farther north, the use of fans has slowly become more common in the past decade, but many facilities are still hesitant to install them.  So why is there still resistance to the use of fans in the Northeast? Cost of fan installation and operation is one reason.  The perceived disruption to the game of golf and their unattractiveness probably plays a bigger role.  Finally, many golfers still feel that fans are necessary only in the Southeast or Transition Zone and not important in the Northeast.  This couldn’t be further from the truth.  

            Obviously, the Northeast doesn’t experience periods of heat and humidity for the same duration as the Southeast or Transition Zone, but that has no bearing on whether a fan is necessary.  Instead, these conditions suggest that fans need not be operating for as long a period in the Northeast.  For instance, fans run in the Southeast from May through October, while the Northeast may need fans only during June, July, and August.  The bottom line is, restricted air movement leads to poor putting greens in all parts of the country.   It’s not just a Southeast or transition zone problem.       


Evaluating Air Movement Across Putting Greens 

            Some putting greens are obvious candidates for fans if they are encircled by dense vegetation, are pocketed, or are located in low-lying portions of the golf course.  Evaluating air movement is easy-to-do with the use of hand-held wind meters that measure wind velocity.  Next, determine air movement direction with a smoke bomb or similar device (Zontek, 1992).  Correlate this information with past green performance, and it should be easy to identify which microclimates are in most need for additional air movement.  Turf canopy thinning, algae, disease, and excessive moisture retention are common maladies of putting greens with poor air movement to look for during the evaluation process.  Keep in mind that fans are not a substitute for tree removal, but some microclimates could require the removal of hundreds of trees to improve air movement, which is why fans are so beneficial.   


Fan Placement is Key        

            Fan technology has remarkably improved since their early use.  Small, loud fans that improved air movement over a small area have been replaced with large, quiet fans that can improve turf conditions over a much larger area through slow oscillation.  Fans work similarly to automatic irrigation heads.  Air movement is greatest near the fan and declines gradually the farther away from the fan.  Consequently, fans can be misused when poorly placed.  Fans installed far away from putting greens to camouflage their existence usually benefit the rough near the green complex, but provides little, if any, improvements to the green.  Don’t fall into this trap.  Just because larger fans can improve air movement over bigger area doesn’t mean they should be placed farther away from the surface.  If the fan is farther than 20 feet from the green surface, it’s not likely to benefit the entire putting green.  Also, fans should be placed in the area that is most in need of air movement.  All too often, fans are hidden so players don’t see the fan from drive zone.  Sometimes this works, but, in most situations, a fan placed directly behind the green (in clear view) is most beneficial because the oscillation will allow for the entire green to benefit.  Portable fans installed on easily moveable trailers are a relatively new method to use fans when and where necessary.  Like permanent fans, though, they need to be close to the putting green to improve air movement significantly.     

            Fan height is usually 10 feet or less to maximize air movement across the surface of the green.  The angle of attack also should be considered to maximize the benefit of fans.  Seeing the moving flag on the flagstick is a good sign, but the air movement at the turf surface could still be stagnant.  During installation, place irrigation flags throughout the green so that the miniature flags are three inches above the turf surface.  Adjust the fan angle according to the movement of these flags.  In most instances, this requires the angle of attack to be pointed toward the turf more than you would have otherwise.  The ultimate goal with fans is to increase air movement by 3-5 mph across the entire putting surface.  If this isn’t achieved, adjust the fan placement, height, or angle as needed.   


Fan Use 

            Fan use is most needed during the summer months, but stressful weather in the spring has been common in the past few seasons, so don’t wait to get them set up.  Running fans 24 hours a day during periods of heat and humidity is common.  If fans can’t be used for 24 hours, operating them from the evening to early morning hours may offer the most benefits with respect to alleviating heat stress and increased newsContenting (Haung et al., 2001).   




            The summer of 2010 was extreme, and putting greens with poor air movement declined throughout the Northeast.  Many facilities learned the hard way that fans can make the difference between a good and terrible golf season.  The agronomic benefits of fans cannot be disputed.  The game of golf is played on grass, and fans may be necessary to produce healthy grass on golf courses, even in the Northeast.  You might even play better golf on that green that used to make you uncomfortably hot and sticky in years past.