Golf Course Management

SEP 2013

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

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cutting edge Research in progress tions of fenarimol (2 pounds ai/acre), fenarimol + zinc (19.62 and 80.29 pounds zinc/acre), and prodiamine (1 pound ai/acre). Zinc applied at 159.70 pounds/acre controlled annual bluegrass 80% throughout the season. Prodiamine, which is currently not labeled for putting greens, controlled annual bluegrass 90%; applications of fenarimol controlled annual bluegrass only 40%. These data indicate that by applying 80.29-159.70 pounds zinc/acre, it is possible to greatly reduce annual bluegrass populations. However, the environmental and long-term impact of such zinc applications requires further study. — Caleb Bristow III; J. Scott McElroy, Ph.D. (jsm0010@auburn.edu); and Elizabeth A. Guertal, Ph.D., Auburn University, Auburn, Ala. Photo by C.M. Baldwin Application timing and perennial ryegrass glyphosate tolerance In an established stand under optimal growing temperatures, perennial ryegrass cultivars JS501 and Replay can tolerate a maximum glyphosate rate of 22 ounces/acre using a 4.17 pounds/U.S. gallon formulation. The objectives of this research were to determine seedling tolerance and low-temperature response following a late-season glyphosate application to both cultivars. Field trials were in Idaho and Oregon. For the low-temperature response trials, glyphosate (4.17 pounds/gallon) was applied at rates of 0-96 ounces/acre from late September to early October. For the seedling tolerance trial, glyphosate was applied at the 1- to 4-leaf stage at rates of 0-16 ounces/acre. Results suggest avoiding glyphosate applications >4 ounces/acre as minimum air temperatures approach 32 F and avoiding rates >8 ounces/acre at the 3- to 4-leaf stage. — C.M. Baldwin, Ph.D. (cmb907@msstate.edu), Mississippi State University, Mississippi State, Miss.; A.D. Brede, Ph.D., and J.J. Mayer, Jacklin Seed, Post Falls, Idaho; and R.C. Golembiewski, Ph.D., Bayer Crop Science AG, Columbus, Ohio. Response of annual bluegrass to zinc in bermudagrass Photo by Phil Bruner Teresa Carson 90 GCM September 2013 Annual bluegrass (Poa annua L.) is one of the most problematic weeds in turfgrass. Initial research shows that zinc, which is commonly applied as a micronutrient, negatively affects annual bluegrass when applied at non-agronomic rates. Field studies were conducted at the Auburn University Turfgrass Research Unit from 2009 to 2011. The study was conducted on a non-overseeded bermudagrass putting green. Treatments included four zinc rates (19.62, 40.14, 80.29, 159.70 pounds/acre), single and multiple applica- Photo by K.R. Hivner Field evaluation of enhancedeffciency nitrogen fertilizers Atmospheric loss of nitrogen from urea fertilizer applied to turfgrass is due to urease activity in soil, thatch and verdure. In the presence of water, urease hydrolyzes the urea molecule into ammonia (NH3), ammonium (NH4 +), and bicarbonate (HCO3-). Hydrolysis of urea at the soil/thatch/ leaf surface incites volatilization of the ammonia counterpart. Volatilization may account for >30% urea-nitrogen loss and is favored by elevated temperatures, soil pH levels and limited moisture/ humidity. Superintendents' concern over the fate of fertilizer nitrogen necessitates feld evaluation of currently available stabilized/enhanced urea fertilizers and urea-additives (each containing urease- and/or nitrifcation-inhibitors). Direct measurements of volatilization loss and fertilizer use effciency resulting from Umaxx, Ufexx, urea and coated-urea fertilizer treatments were initiated in July on Kentucky bluegrass and creeping bentgrass systems. Additional treatments included Nutrisphere-N, Hydrexx and dicyandiamide (DCD) additives to urea (each applied at label rates). Study results will be made available in 2014. — Maxim J. Schlossberg, Ph.D. (mjs38@psu. edu); Derek T. Pruyne; and Kyle R. Hivner, Penn State University, University Park, Pa. GCM Teresa Carson (tcarson@gcsaa.org) is GCM's science editor.

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