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Issue link: http://gcmdigital.gcsaa.org/i/255121
02.14 GOLF COURSE MANAGEMENT 105 Iron and potassium affect velvet bentgrass performance A feld trial was conducted in North Brunswick, N.J., to evaluate the effect of iron and potassium nutrition on performance of velvet bentgrass subjected to traffc. The trial was initiated in 2010 on 6-year-old Greenwich VBG turf mowed daily at 0.11 inch. Traffc levels were 0 or 200 rounds per day applied by students walking in golf shoes with soft spikes. Iron sulfate was applied at 0 or 0.4 ounce of iron/1,000 square feet every two weeks. Po - tassium sulfate was applied at N:K of 1:0, 1:0.4, 1:0.8, 1:1.7 and 1:3.3 every two weeks in combination with N applied at 0.1 pound N/1,000 square feet. Foot traffc reduced turf quality and color compared to no foot traffc, especially during high-temperature stress. Bi - weekly iron sulfate applications increased turf color during the growing season; turf quality improvement was more subtle. Biweekly ap - plications of potassium sulfate at N:K ratios of 1:1.7 and 1:3.3 lowered turf quality and color July−October compared to lower ratios or no potassium application. The negative ef - fect of potassium applications is likely due to supraoptimal soil K levels (>160 milligrams/ kilogram) in the thatch-mat region. Results indicate that biweekly applications of iron sul - fate can mask discoloration of VBG caused by foot traffc, and biweekly applications of higher rates of potassium reduced turf per - formance. — James A. Murphy, Ph.D. (murphy@ aesop.rutgers.edu), and Charles J Schmid, Rutgers University, New Brunswick, N.J. Pre-emergence control of crabgrass in putting greens The objective of this study was to evaluate the effcacy and safety of a new herbicide, me - thiozolin (not yet approved by the U.S. EPA), for pre-emergence control of crabgrass (Digi - taria species) on creeping bentgrass greens. Field plots were established in Columbia, Mo., in 2012 and 2013. Treatments were: an untreated control; methiozolin (0.446, 0.669 or 0.89 pound ai/acre) as single or sequential applications at 14- or 28-day intervals; pre- emergence herbicides bensulide (12.49 pounds ai/acre), dithiopyr (0.499 pound ai/acre), in - dazifam (0.07 ounce ai/acre), pre-packaged bensulide + oxadiazon (12.04 + 3.03 pounds ai/acre) and siduron (3.03 pounds ai/acre) as single or sequential applications at 28-day in - tervals. Data included turf quality, normalized difference vegetation index, phytotoxicity and percent crabgrass cover. All treatments, with the exception of siduron, reduced crabgrass cover by 60% or more at 8 weeks after ini - tial treatment (WAIT) in 2012. At 21 WAIT, crabgrass control was 93% (bensulide), 94% (dithiopyr) and 90% (two applications of me - thiozolin [0.89 pound ai/acre] at 28-day in- tervals). In 2013, crabgrass control was ≥76% for all treatments except siduron at 8 WAIT. In both years, the only treatment that caused signifcant phytotoxicity was the pre-packaged bensulide + oxadiazon, but turf phytotoxicity was still ≥6 on a 1-9 turf quality scale. — John B. Haguewood, Reid J. Smeda and Xi Xiong, Ph.D. (firstname.lastname@example.org), University of Missouri, Co - lumbia, Mo. Teresa Carson (email@example.com) is GCM 's science editor. CUTTING EDGE Teresa Carson Photo by James A. Murphy Photo by John Haguewood 094-105_Feb14_TechwellCuttingEdge.indd 105 1/17/14 11:48 AM