Golf Course Management

JAN 2019

Golf Course Management magazine is dedicated to advancing the golf course superintendent profession and helping GCSAA members achieve career success.

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01.19 GOLF COURSE MANAGEMENT 119 CUTTING EDGE Teresa Carson Measuring putting green firmness Firmness is an important attribute of healthy putting greens, affecting both play - ability and durability, but it is often discussed in subjective terms ("want firmer greens" or "greens are too soft"). Underlying factors asso - ciated with firmness include volumetric water content (VWC), organic matter (OM) and bulk density (BD), and are managed through irrigation, aerification, topdressing, verticut - ting and rolling. Understanding the extent to which measurements reflect each of these underlying factors may allow superintendents to improve the efficiency and precision with which they manage firmness. is research sought to examine relationships between firm - ness measurements and ground-truth data for VWC, OM and BD, and to compare variabil - ity among measurement devices. e experi- mental area was a Penn A-1 creeping bentgrass green with a USGA sand-based root zone. Measurements were taken using the Clegg Im - pact Soil Tester (Lafayette Instruments), Field- Scout TruFirm turf firmness meter (Spectrum Technologies), and FieldScout TDR 350 mois - ture meter (Spectrum Technologies). Com- binations of irrigation, rolling and cultural practices were used to create individual plots. Samples were extracted at the site of each mea - surement to calculate ground-truth VWC, OM and BD. Device comparisons were based on 24 adjacent measurements within plots. All devices had significant relationships with VWC, OM and BD: TDR 350 had the stron - gest correlation with VWC; across all devices, OM had the weakest correlations; and Tru - Firm was correlated most closely with BD. ese results indicate that superintendents implementing proper maintenance practices should consider the different capabilities and limitations of devices used to measure firm - ness. — Daniel P. O'Brien; Douglas E. Karcher, Ph.D. (karcher@uark.edu); and Michael D. Richard - son, Ph.D., University of Arkansas, Fayetteville, Ark. Wetting agents affect soil moisture, water infiltration Wetting agents, amphiphilic molecules that contain both a hydrophobic tail and a hydrophilic head, are used to alleviate soil hy - drophobicity on putting greens. Once a wet- ting agent has moved into the root zone, the hydrophobic tail adheres to the hydrophobic sand grain, allowing water molecules to attach to the hydrophilic head, thus promoting wet - ting. Ideally, a wetting agent would maintain a balance between adequate water retention and fast infiltration, thereby promoting a firm playing surface. Our previous experiments showed that various wetting agents reduce the surface tension of water by 36% or more, resulting in enhanced water infiltration into water-repellent soil. In 2018, we performed a field experiment on a 007 creeping bentgrass USGA green where soil hydrophobicity was observed. Six wetting agents (H2O Maxi - mizer, Capacity, Aqueduct, Infiltrix, TriCure AD and Primer Select), representing differ - ent capacities for reducing the surface tension of water, were applied to replicate field plots on a monthly basis. Compared with the un - treated control, H2O Maximizer maintained 3% higher volumetric water content through - out the growing season and resulted in 60% less localized dry spot (LDS). Control plots with no wetting agent application displayed a decreased infiltration pattern in summer. Like H2O Maximizer, Capacity maintained a steady infiltration rate. Aqueduct led to el - evated infiltration in the first two months, but like Capacity, it resulted in 61% less LDS for - mation. e other wetting agents tested main- tained a higher infiltration rate than the USGA recommendations as well, and reduced LDS by 50%. Collectively, our results suggest that sur - face tension alone does not predict overall wet- ting agent performance, but head-to-tail ratio likely contributes to a product's effectiveness in balancing water retention and maintain - ing a firm playing surface. — Matthew Fleet- wood; Stephen H. Anderson, Ph.D.; Keith Goyne, Ph.D.; and Xi Xiong, Ph.D. (xiongx@missouri.edu), University of Missouri, Columbia, Mo. Teresa Carson (tcarson@gcsaa.org) is GCM 's science editor. Photos by Daniel O'Brien Photo by Matthew Fleetwood

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