Using Green Firmness Measured with a Clegg Impact Soil Tester to Predict Ball Mark Size On Putting Greens.

This study was conducted to determine if putting green firmness measured with a Clegg Impact Soil Tester was a good predictor of ball mark size.  As part of the study, it was determined if a golf ball launching device could be used to simulate ball marks made from actual golf shots.  A golf ball launcher designed by Rutgers University was adapted and calibrated to simulate the impact made by a golf ball hit from 91 m using a 56° wedge from the fairway.  Golf balls were hit into greens from 91 m with a 56° wedge from the fairway by a 5 handicap golfer to create “natural” ball marks.  Only ball marks created by well struck shots were used.  After the natural ball marks were made, the golf ball launcher was used to make a ball mark within 3 cm of the natural mark.  The depth of each ball mark was measured by firmly placing a graduated golf ball into the ball mark and estimating the percent ball below the surface.  Within 3 cm of each ball mark, green firmness was measured with 1 drop of a 2.25 kg Clegg and soil water content was measured with a Hydrosense 620 Water Content Sensor (12-cm rods).  Linear regression was used to describe various relationships.   The relationships between green firmness and launcher ball mark size (R² = 0.56) and between green firmness and natural ball mark size (R² = 0.52) were both moderate and inverse.  Thus, firmness measured with the Clegg was a moderate predictor of ball mark size.  The relationship between natural and launcher ball mark size (R² = 0.80) was strong and direct.  Thus, the launcher could be used to simulate ball marks made from actual golf shots.