Golf Course Management

AUG 2019

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08.19 GOLF COURSE MANAGEMENT 73 CUTTING EDGE Teresa Carson Polyethylene glycol effects on zoysiagrass root growth in a hydroponic system Historically, drought tolerance in turf- grasses has been tested using field evaluations under drought conditions. However, periods of drought are unpredictable and variable, which can hamper breeding programs fo - cused on drought responses. In this study, we aim to identify drought-tolerant zoysiagrass genotypes using a polyethylene glycol (PEG) screening method in hydroponic systems. We grew 13 zoysiagrass (Zoysia species) genotypes (including entries germinated in PEG) in hy - droponic culture without PEG (control) or with an increasing concentration of PEG over the course of four weeks. e hydroponic cul - tures (no PEG and PEG) were split into the 13 genotypes comprising four commercial cultivars (Zeon, Icon, Palisades and Empire) and nine experimental lines. During treat - ment, plants were evaluated for growth and morphological characteristics, including root emergence, root length density, root surface area, average root diameter, wilting and new leaf production. Analysis of two trials of this experiment resulted in no differences between PEG treatments. Genotypes were different for several characteristics, but there was no genotype × PEG interaction. Genotypic dif - ferences were seen with root length, root surface area, average root diam - eter, number of shoots and leaves produced, root emergence, and wilting. e lack of an interaction between genotypes and PEG treatment indicated that the PEG concentrations used in this study were not suf - ficient to cause differences in plant responses; however, the study does provide supportive ev - idence that a hydroponic system is an effective means for identifying differences in root and shoot responses between genotypes. — Kath- erine Cox; John Erickson, Ph.D.; Esteban F. Rios, Ph.D.; and Kevin E. Kenworthy, Ph.D. (kenworth @ufl.edu), University of Florida, Gainesville, Fla.; and J. Bryan Unruh, Ph.D., University of Florida West Florida Research & Education Center, Jay, Fla. Shallow soil compaction following fraze mowing Fraze mowers are aggressive tractor- mounted implements that can remove plant and soil material from depths of 0 to 2 inches (5 centimeters). Compaction from routine traffic in turfgrass systems is usually confined to the surface 3 inches (7.6 centimeters) of the soil profile, which overlaps with fraze mower functional depths. is study was conducted to evaluate fraze mowing as a viable cultiva - tion method to remove surface compaction beneath Tifway hybrid bermudagrass. A trial was conducted in 2018 on a sandy soil in Jackson Springs, N.C. Plots were subjected to increasing levels of simulated traffic (0 = untreated; 20 passes = 40 American football games; or 30 passes = 60 games) with a modi- fied Baldree traffic simulator. All plots were then fraze-mowed at depths of 1 or 2 inches (2.5 or 5 centimeters), and measurements were made following traffic simulation and fraze mowing. Soil hardness increased with the number of simulated games. All traffic levels had similar soil hardness values after fraze mowing. Trafficked treatments (20 and 30 passes) had lower soil hardness values after fraze mowing, and non-trafficked control treatments had a 29% increase in soil hard - ness after fraze mowing. However, volumetric water content was 43% less at sampling after fraze mowing, which may have increased non- trafficked control soil hardness values. Satu - rated hydraulic conductivity (Ksat) decreased 32% after fraze mowing at the 1-inch depth and remained static at the 2-inch depth (2.2 inches or 5.6 centimeters/hour) after fraze mowing. Lower soil hardness values follow - ing fraze mowing in trafficked plots indicate the potential for compaction relief. However, lower Ksat rates at 1-inch fraze mowing depth may indicate potential soil crusting. is study is being repeated in 2019. — Raymond McCauley, Grady L. Miller, Ph.D. (grady_miller@ ncsu.edu), and Drew Pinnix, North Carolina State University, Raleigh, N.C. Editor's note: Earlier versions of these summaries were published in the 2018 ASA-CSSA Meeting Abstracts, ASA and CSSA, Madison, Wis. Teresa Carson (tcarson@gcsaa.org) is GCM 's science editor. Photo by Katherine Cox Photo by Drew Pinnix

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