Golf Course Management

NOV 2016

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

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11.16 GOLF COURSE MANAGEMENT 79 causes preferential flow, ultimately leading to plant death in the affected area (see photo). Application of wetting agents is the pri - mary strategy used to improve water infil- tration into water-repellent soil. The wetting agent molecules are am i ilic compounds containing a hydrophobic group that can ad - here to hydrophobic sand surfaces, and a hy- drophilic group that can "hold on" to water molecules. By attaching to the hydrophobic sand surfaces, wetting agents can alter soil hy - drophobicity and subsequently improve water infiltration into water-repellent soil. Despite the wide use of wetting agents by superintendents, the No. 1 question that re - mains unanswered is which wetting agent is the best. A number of factors currently pre - vent us from answering this question. One of these is variation in field conditions, such as the level and the consistency of soil hydro - phobicity. At the University of Missouri, a turf spe - cialist, a soil physicist and a soil chemist have formed a collaborative team with the objective of improving our understanding of soil hydro - phobicity and wetting agents. In the past three years, our team has made two major break - throughs related to the effect of wetting agents on soil infiltration. The first breakthrough was to artificially treat sand that meets USGA recommenda - tions for greens construction in order to make it water-repellent. The treated sand demon - strated steady and consistent water repellency, and the level of hydrophobicity was deter - mined to be severe, because the water drop- lets never penetrated into the sand layers and eventually evaporated. Artificially developed hydrophobic sand avoids the difficulties as - sociated with inconsistent levels of hydropho- bicity across space and time in naturally oc- curring hydrophobic sand, which experiences changes in hydrophobicity as soon as it comes in contact with water. The second breakthrough was the deter - mination of a relationship between measur- able properties of a given wetting agent, such as surface tension, and its effect on infiltration into hydrophobic sand. This was conducted by using a piece of sophisticated equipment called a tensiometer, which allows us to pre - cisely evaluate a wetting agent solution's sur- face tension as a function of its concentra- tion. For example, our research found that the wetting agent Cascade Plus at concentrations ≥3,000 mg/liter (less than half the suggested label rate) maintained a surface tension that is lower than the 90-degree surface tension at 31.3 milliNewton/meter determined for the artificially made hydrophobic sand. This re - sult means that Cascade Plus at this concen- tration or higher can spontaneously wet the water-repellent sand. In comparison, wetting agent Surfside 37 showed a higher surface tension even at 5,000 mg/liter. This means that Surfside 37 at this concentration will not infiltrate the hydro - phobic sand unless a certain depth of solu- tion (ponding head) exists above the sand sur- face in order to force the liquid into the sand layers. In another words, Surfside 37 at this concentration will not wet the hydrophobic sand. These results were corroborated by an infiltration study in which the infiltration rate of Cascade Plus was more than twice that of Surfside 37 at the tested concentrations. This is an ongoing project. Our objective for this experiment is to test approximately 50 commonly used wetting agents for their surface tension at various concentrations, and relate their physical properties to infil - tration. The ultimate goal is to develop a research-based guide for wetting agents by grouping them into categories in terms of their efficacy in facilitating water infiltration into hydrophobic soil. Xi Xiong (xiongx@missouri.edu) is an associate profes- sor in the Division of Plant Sciences, Steven Anderson is a William A. Albrecht Distinguished Professor in the Depart - ment of Soil, Environmental and Atmospheric Sciences, and Keith Goyne is an associate professor in the Depart - ment of Soil, Environmental and Atmospheric Sciences and associate director of the School of Natural Resources at the University of Missouri, Columbia, Mo. (report) Performance and recovery of four turfgrass species subjected to golf cart traffic during prolonged drought Ross Braun Dale Bremer, Ph.D. Jared Hoyle, Ph.D. One of the biggest challenges facing golf course superintendents is decreasing water available for irrigation. Increasingly, state and local drought restrictions may be imposed on turf managers, with no regard for damage to turfgrass (1). During periods of severe drought and water shortages, turfgrass may receive little to no irrigation for extended spans of time (2). Traffic damage is another management issue superintendents commonly face. Traffic, such as that near cart paths where golfers tend to either walk or drive carts into fairways and roughs, may cause significant wear to turfgrass and also compact the soil. These factors result in, among other things, reduced tolerance to heat and drought stresses (3). In fact, when the soil is compacted, more-frequent irriga - tion is often required to compensate for the detrimental effects of compaction on root and shoot growth. Significant research has been conducted separately into the issues of drought resistance and traffic tolerance in turfgrass. Results have indicated that turfgrasses vary widely in their ability to resist drought and tolerate traffic. However, little research has been conducted to investigate the combined effects of drought and traffic in turfgrasses. Given the increasing likelihood of irrigation restrictions for turfgrass at operational golf courses with areas of high traffic, conducting such research is imperative. Therefore, the objective was to evaluate the combined effects of golf cart traffic on both warm-season (C 4 ) and cool-season (C 3 ) turf- grass species maintained at fairway or rough mowing heights during a simulated drought period and a subsequent recovery period (with - out traffic).

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