Figure 2. Main effects for perennial ryegrass overseeding on trafficked ‘Tifway’ bermudagrass, Knoxville, TN LSD (0.05) = ns LSD (0.05) = 6.5 LSD (0.05) = 5.8LSD (0.05) = 3.6 Abstract : Bermudagrass (Cynodon spp.) athletic fields are often overseeded with perennial ryegrass (Lolium perenne) to improve aesthetic and functional quality during late fall and early winter. Data outlining the effects of mowing and overseeding on the traffic tolerance of ‘Tifway’ hybrid bermudagrass is limited. A study was conducted at the University of Tennessee (Knoxville, TN) in 2007 and 2008 to investigate the effects of mowing and overseeding on the traffic tolerance of ‘Tifway’ hybrid bermudagrass. The experiment was arranged as a split-plot design with three replications. Mowing practice (reel mower equipped with groomers set to a depth of 1.9 cm, reel mower without groomers, and a rotary mower) served as the whole plot treatment. All mowers were set to a height of 2.2 cm, and mowing treatments were applied three times per week. Overseeding rate served as the sub-plot treatment. Five different rates of perennial ryegrass were evaluated: 0 kg ha -1, 224 kg ha -1, 448 kg ha -1, 672 kg ha -1 and 897 kg ha -1. Plots were subjected to a minimum of 17 games of simulated traffic applied with a Cady traffic simulator in both years. Digital image analysis was used to quantify percent cover, turfgrass color, and turfgrass quality. Trend analysis was used to separate overseeding treatment means. Overseeding rate had a significant linear effect on turfgrass cover under simulated traffic After 17 games of simulated traffic in 2007, percent cover for plots overseeded at 0 kg ha -1 measured 72% compared 93% for plots overseeded at 897 kg ha -1. A similar response was observed in A significant mower treatment by year interaction was reported for percent cover data on 15 out of 17 rating dates. These data suggest that increases in overseeding rate can improve the cover of Tifway hybrid bermudagrass athletic fields under simulated traffic. Objectives: 1.Determine if mowing practices have an affect on overseeding. 2.Determine what rate of overseeding will provide the most percent green cover under simulated traffic. Materials and Methods: A two year field study was conducted from 2007 to 2008 at the East Tennessee Research and Education Center at the University of Tennessee in Knoxville, TN. Research was conducted on established ‘Tifway’ bermudagrass overseeded with Ph.D. brand perennial ryegrass (32.28% ‘All Star 2’ perennial ryegrass, 32.84% ‘Derby Xtreme’ perennial ryegrass, 32.82% ‘Top Hat’ perennial ryegrass). The statistical design was a split-plot design with three replications with the whole plot treatment consisting of a 2.2 cm height of cut using a reel mower, a reel mower plus groomer (set at a 1.9 cm height), and a rotary mower. Mowing treatments were done three times a week during the growing season using a Jacobsen walk behind reel mower with 7 blades and a grooming attachment, and a Toro Sidewinder rotary mower. Subplot treatments were perennial ryegrass overseeding rates of 0, 224, 448, 672, and 897 kg ha -1, respectively. Plots were fertilized with 292 kg of N ha -1 yr -1, 49 kg of P ha -1 yr -1, 146 kg of K ha -1 yr -1, respectively. Irrigation was applied as needed throughout the study. Plots were trafficked using the Cady Traffic Simulator beginning 26 Aug 2007 and 2008 through 21 Nov 2007 and Data was collected using digital image analysis. Turfgrass percent green cover was rated on 0 to 100% scale. Mowing and overseeding practices affect the traffic tolerance of ‘Tifway’ hybrid bermudagrass athletic fields in the transition zone. A.W. Thoms*, J. C. Sorochan, J. T. Brosnan, T. J. Samples, and B. J. Horvath Dept. of Plant Sciences, University of Tennessee Introduction: Bermudagrass (Cynodon Spp.) is the most common species used for athletic fields in the transition zone because of its aggressive rhizomatous and stoloniferous growth habit, and ability to tolerate close mowing (Puhalla et al., 1999). Unfortunately, portions of football and baseball seasons take place when bermudagrass is dormant where recuperation from wear is limited. To overcome this, perennial ryegrass overseeding is done to improve turfgrass color and playing surface uniformity (Puhalla et al., 1999). Currently, suggested rates of overseeding with perennial ryegrass range from 250 kg of perennial ryegrass ha -1 to as high as 1250 kg of perennial ryegrass ha -1 (Miller and Cisar, 1990; Powell and Bergstrom, 2005; Bruneau et al., 2004). These seeding rates can have a significant affect on athletic field manager’s budgets, which are often very small. Finding an optimal overseeding rate that tolerates traffic on athletic fields while not wasting seed could be a real savings to many athletic field managers’ budgets. Bermudagrass athletic fields are typically mown with a reel or rotary type mower. Grooming is a cultural practice often done in conjunction with reel mowing to increase turf vigor. The evaluation of mower types including grooming practices, and how they facilitate overseeding establishment on athletic fields warrants investigation. Results: Conclusions: Treatments mown with a reel mower and a reel mower plus grooming yielded the highest percent cover in 2007 (Table1). In 2008, reel mowing alone yielded the highest percent green cover (Table 1). In 2007, unseasonably high late fall temperatures maintained active bermudagrass growth throughout the study preventing dormancy (Figure 2). Whereas in 2008 bermudagrass dormancy began in late October (Figure 3). Overseeding with perennial ryegrass provided greater percent green cover compared to non-overseeded plots regardless of the overseeding rate (Figure 2 and 3). As traffic events increased differences between perennial ryegrass overseeding rates decreased in 2008 (Figure 3). No differences occurred, throughout the study, for percent green cover when perennial ryegrass was overseeded at 672 and 897 kg ha -1 (Figures 2 and 3). This suggests that the 897 kg ha -1 overseeding seeding rate is not necessary. References: Bruneau, A. H., C. H. Peacock, R. J. Cooper, and E. J. Erickson Cynodon Spp. management programs for the upper transition zone in the southeastern United States. Acta Horticulturae. 661:p Miller, G.L., and J.L. Cisar Maintaining Athletic Fields. Bul Rev. ed. Univ. of Flordia IFAS Ext. Serv., Gainsville. Powell, A.J., and D. Bergstrom Overseeding Bermudagrass Sports Fields. Univ. of Kentucky Coop. Ext. Serv., Lexington. Puhalla, J., J. Krans, and M. Goatley Sports Fields: A Manual for Construction and Maintenance. John Wiley and Sons, New Jersey. Figure 1. Mowing and overseeding study under simulated athletic traffic. Knoxville, TN Figure 3. Main effects for perennial ryegrass overseeding on trafficked ‘Tifway’ bermudagrass, Knoxville, TN LSD (0.05) = ns LSD (0.05) = 5.4 LSD (0.05) = 6.4 LSD (0.05) = 8.1 LSD (0.05) = 11.0 Results Continued: Table 1. Percent green cover † for mowing treatments on trafficked ‘Tifway’ bermudagrass overseeding study, Knoxville, TN. Year Date (Simulated Traffic Event) 21-Aug (0) 21-Sep (5) 26-Oct (10) 12-Nov (15) 29-Nov (20) 26-Aug (0) 26-Sep (5) 31-Oct (10) 6-Nov (15) 11-Nov (20) 18-Nov (26) Mower TreatmentMeans Reel mowing plus grooming97.1 a80.4 b72.1 a85 a87.8 a93.1 a80.0 a67.1 b54.2 b33.7 b33.1 b Rotary mowing97.0 a86.0 a59.0 b78.6 b83.4 b90.1 a75.1 b70.3 b51.2 b33.6 b33.9 b Reel mowing96.5 a74.5 c72.1 a84.7 a88.6 a92.0 a76.1 b79.8 a60.7 a45.3 a41.6 a † Percent green cover based on Digital Image Analysis (1 to 100%) *Plots were overseeded with perennial ryegrass on 1 Oct 2007 and 22 Sep 2008