Influence That Soil Water Content Has On Putting Green Firmness.

Research in 2009 by PACE Turf comparing the Clegg Impact Soil Tester (Clegg) to the Trufirm device for measuring putting green firmness was the impetus for more closely analyzing over 1700 samples of green firmness measured with the Clegg on 52 golf courses from 2004 to 2008.  At least 3 greens were tested per course with either the 0.5 kg or 2.25 kg Clegg hammer.  Measurements were taken at 6 different sites per green.  Within 3 cm of each firmness measurement site, soil volumetric water content was measured using a Hydrosense 620 Water Content Sensor (12-cm probe rods).  For 2 golf courses, data were collected on multiple dates from every green on the course.  Data were categorized various ways such as sand-based, soil-based, combined, etc.  Regression was used to describe the relationship between green firmness and soil water content.  The R² values ranged from 0.19 to 0.63, with sand-based greens having the highest R² values.  Intuitively, green firmness is inversely related to soil water content.  Most golfers would agree that putting greens become softer after rainfall and firmer as they dry.  In this study, there was an inverse relationship between green firmness and soil water content, however, it was not as strong as expected.  The turf verdure, thatch, soil texture, and soil bulk density were likely the factors that impacted green firmness in addition to soil water content.