Golf Course Management

APR 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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04.19 GOLF COURSE MANAGEMENT 87 CUTTING EDGE Teresa Carson Irrigation requirements of cool-season fairway species A two-year field study evaluated the total water needs of six cool-season fairway species: creeping bentgrass (Agrostis stolonifera: CB), colonial bentgrass (Agrostis capillaris: CLB), perennial ryegrass (Lolium perenne: PR), three Kentucky bluegrasses (Poa pratensis: KBG), two fine-leaf fescues (Festuca species: FF), and two tall fescues (Schedonorus arundinaceus: TF) maintained at two supplemental irriga - tion regimes on a silt-loam soil under a fixed- roof rainout shelter in West Lafayette, Ind. e supplemental irrigation regimes were: 80% evapotranspiration (ET) replacement, applied three times per week, and a green- color-threshold response approach using digi - tal image techniques. When an individual plot fell below the green-color threshold (55% green for year 1 and 65% green for year 2), 0.25 inch of water was applied for year 1, and 0.3 inch for year 2. For the 75-day study pe - riod in year 1, the 80% ET replacement re- ceived a total of 10.9 inches of supplemental irrigation. e color response-based regime required less water for all turf species, with the least irrigation, 2.8 inches, required by the TFs and one KBG, compared with CB, which needed 3.75 inches. For the 60-day study pe - riod in year 2, the 80% ET replacement re- ceived a total of 8.3 inches of supplemental ir- rigation. Similar species trends continued for the color-response-threshold regime; the TFs and one KBG required the least, only about 3.6 inches, and CB required 7.5 inches. is study demonstrates that significant supple - mental irrigation savings could be achieved by alternative irrigation strategies like a green- color-threshold response approach and/or maintaining species other than CB. — Jada Powlen (jpowlen@purdue.edu) and Cale Bigelow, Ph.D. (cbigelow@purdue.edu), Purdue University, West Lafayette, Ind. Effects of soil temperature on wetting agent efficacy Wetting agents are commonly applied to manage localized dry spot (LDS) occurrence. Preventive applications are often made regu - larly, at fixed intervals, throughout the grow- ing season as directed by product labels. is approach, however, may not provide the most efficient use of wetting agents since LDS de - velopment is most common in mid-summer dry periods. Wetting agents are also suscep - tible to microbial breakdown, which is influ- enced by soil temperature. e objective of this research was to assess the ability of wet - ting agents to reduce soil water repellency at different soil temperatures. Five wetting agent treatments were applied on a creeping bent- grass (Agrostis stolonifera) sand-based research green in St. Paul, Minn., in May, July and October 2017 on separate plots. Soil tempera - ture was logged in each plot, and soil water re- pellency was determined using water-droplet penetration-time tests. After a single applica - tion, wetting agent treatments varied in their abilities to reduce soil water repellency com - pared to an untreated control for the remain- der of the growing season. A growth chamber experiment was added to reduce fluctuations of soil temperature and to overcome spatial variability of field trials. e root zones of creeping bentgrass plugs were maintained in conetainers at three temperature treatments: 71 F, 82 F and 94 F (21.5 C, 28 C and 34.5 C). Following single wetting agent applications, soil water repellency and water retention were quantified over time. Results from these ex - periments will be used to develop recommen- dations for frequency of wetting agent applica- tions. — Ryan Schwab, Samuel Bauer and Brian Horgan, Ph.D. (bphorgan@umn.edu), University of Minnesota, St. Paul, Minn. Earlier versions of these summaries were pub- lished in the 2018 ASA-CSSA Meeting Ab- stracts, ASA and CSSA, Madison, Wis. Teresa Carson (tcarson@gcsaa.org) is GCM 's science editor. Photo by Jada Powlen Photo by Ryan Schwab

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