COURSE CARE
365 Days With The TruFirm: Four Things I’ve Learned October 15, 2013 By Chris Hartwiger

The USGA TruFirm is a device that measures the firmness of a putting green. 

A peek into a USGA Green Section agronomist’s trunk at the end of a golf season can yield some interesting discoveries. There is always a variety of golf equipment, agronomic tools, a Stimpmeter or two, and recently, a device for testing putting green firmness called the USGA TruFirm. This device was introduced in 2005 by Dr. Matt Pringle, Technical Director in the USGA’s Equipment Standards Department. 

Historically, we have used the TruFirm to quantify the firmness of the putting greens at our USGA Championships and manage it throughout the championship. In 2012 – 2013, I decided to take the TruFirm on the road and use it during most Turfgrass Advisory Service visits. My goal was to test a green or two on each visit and see what I learned. Below are a few interesting discoveries that I made. Please be advised that these were not scientific studies, but were in the field measurements taken by a curious agronomist. 

 

Four Things I’ve Learned  

  • Firmness Changes Seasonally

The firmness of both creeping bentgrass and ultradwarf bermudagrass changes seasonally. Generally, the period of maximum firmness for both grasses is in the spring and the least firm period is late summer. 

  • Bentgrass vs. Ultradwarf Bermudagrass:  Which One is Firmer?

There was a view that ultradwarf bermudagrass putting greens always are firmer than creeping bentgrass putting greens. Not true! Both the firmest and softest putting greens I have ever measured were ultradwarf bermudagrass putting greens. 

  • Moisture and Topdressing Volume Dictate Firmness

Firmness is not necessarily related to the grass type. Instead, soil moisture and the annual volume of sand topdressing seem to govern firmness. The best way to promote firmer greens is to increase the amount of sand topdressing applied annually. 

  • Approach Firmness Often Does Not Match Putting Green Firmness

Ideally, approach firmness should be close to the putting green firmness so that golfers with a lower trajectory ball flight can land balls in the approach and have them run onto the putting green. This is particularly desirable for front hole locations. Unfortunately, most approaches I measured were significantly softer than the putting greens. 

I have enjoyed measuring putting green firmness on numerous golf courses in the southeast. As I gain more knowledge, I look forward to sharing this information with staff and course officials on Turfgrass Advisory Service visits. 

Source: Chris Hartwiger (chartwiger@usga.org)

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