Golf Course Management

MAY 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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05.19 GOLF COURSE MANAGEMENT 73 CUTTING EDGE Teresa Carson Effects of organic amendments on dollar spot in bentgrass fairways Organic amendments offer an alternative tool for managing dollar spot (Clarireedia spe - cies). A two-year trial was initiated in late 2016 on 007 creeping bentgrass (Agrostis stolonifera L.) maintained as a golf course fairway to evaluate the impact of fertility and fungicide source on dollar spot development in a newly established fairway. We evaluated a municipal waste compost and a biochar applied at estab - lishment and as a topdressing applied biannu- ally; a vermicompost + fertility treatment; a standard fertility treatment; and no treatment. Nitrogen fertility levels for all treatments were ~4.2 pounds of nitrogen/1,000 square feet (205 kilograms/hectare) annually. Subplot fungicide treatments were applied as a 14-day contact, contact threshold, 14-day penetrant, penetrant threshold, and none. reshold treatments were made when more than two infection centers were counted on two of four replicates. e most consistent treatments for dollar spot reduction during periods of high pressure were the biochar, vermicompost and standard fertility treatments. Municipal waste compost treatments were more effective in the spring of each growing season. When consid - ering seasonal control of dollar spot, all fertil- ity treatments were similar in 2017. In 2018, the greatest reductions came from the biochar, vermicompost and standard fertility treat - ments. All fungicide treatments effectively re- duced dollar spot when applied at designated 14-day intervals. In 2017, the vermicompost + standard fertility treatment provided the longest duration of control for both threshold treatments. In 2018, amendments had little to no effect on residual fungicide control. Pre - liminary data suggests that nitrogen availabil- ity is the driving factor for fertility-mediated dollar spot suppression. — Cody Beckley and Joseph Roberts, Ph.D., University of Maryland, Col - lege Park, Md. Kentucky bluegrass water requirements under deficit irrigation Drought-resistant grasses and deficit ir- rigation can reduce water use without sac- rificing the quality of turfgrass systems. In addition, soil texture or irrigation frequency may affect the irrigation requirements. e objective of this study is to evaluate the ef - fects of cultivar selection, soil texture, irriga- tion frequency and volume on the quality and water use of higher-cut Kentucky bluegrass (Poa pratensis L.) turf. Two Kentucky blue - grass cultivars (Mallard and Geronimo), two soil textures (silt loam and loamy sand), two irrigation frequencies (one and three times weekly), and two irrigation volumes (40% and 80% reference evapotranspiration re - placement) were evaluated in a field lysimeter experiment. Lysimeters were weighed before each irrigation, and actual evapotranspiration was calculated as the loss in weight between successive lysimeter weighing events. Turf quality was determined by evaluating green turf coverage weekly. Lysimeters replacing 80% reference evapotranspiration three times weekly resulted in greater coverage in Sep - tember, whereas irrigation frequency affected coverage at 40% reference evapotranspiration replacement on two dates in September. Ly - simeters replacing 80% reference evapotrans- piration used 1.8 times more water than 40% reference evapotranspiration in late August and September. Water use was significantly affected by soil texture, with lysimeters con - taining silt loam using 2.4 centimeters per week and loamy sand using 2.3 centimeters; however, irrigation systems are not capable of irrigating at volumes as low as 0.1 centimeter. is could imply that higher-cut Kentucky bluegrass turf areas grown in varying soil tex - tures do not require separate irrigation rec- ommendations during periods of prolonged drought stress. Ongoing research this year will look to confirm the results from the first year. — Tyler Carr; Douglas E. Karcher, Ph.D.; Michael D. Richardson, Ph.D.; and Daniel P. O'Brien, University of Arkansas, Fayetteville Editor's note: Versions of these summaries were published 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 Joseph Roberts Photo by Tyler Carr Compost Biochar Photo taken 340 DAT (Oct. 16, 2016 – Sept. 21, 2017)

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