Adam W. Thoms

Efficacy of Flazasulfuron for Control of Annual Bluegrass (Poa annua) and Perennial Ryegrass (Lolium perenne) as Influenced by Nitrogen

Abstract Certain sulfonylurea (SU) herbicides are used to remove overseeded cool-season species from bermudagrass. The effects of nitrogen (N) on the efficacy of a new SU herbicide, flazasulfuron, have not been determined. Field and laboratory studies were conducted in 2008 and 2009 evaluating the efficacy of flazasulfuron for control of overseeded perennial ryegrass contaminated with annual bluegrass. Flazasulfuron was applied at rates of 4.4, 8.8, and 17.5 g ha−1 alone, and in between sequential applications of N fertilizer at 73 kg N ha−1. N was granularly applied immediately prior to herbicide treatment and 4 wk later. In both years, the level of annual bluegrass control with flazasulfuron and two applications of N at 73 kg N ha−1 was significantly greater than following treatment with flazasulfuron alone. This response was observed for all application rates of flazasulfuron on every rating date. The level of annual bluegrass control with flazasulfuron at 4.4 g ha−1 and two applications of N at 73 kg ha−1 was greater than flazasulfuron at 17.5 g ha−1 alone each year. No significant differences in perennial ryegrass control were observed for flazasulfuron with and without N fertility. In laboratory studies with annual bluegrass, treatment with N fertilizer at 73 kg N ha−1 increased translocation of 14C flazasulfuron (and any potential metabolites) from treated annual bluegrass leaves to other shoot tissues by 18% at 1 h after treatment and 22% at 4 h after treatment compared to plants not treated with N fertilizer. This increase in translocation may explain the increased level of annual bluegrass control observed in the field. Nomenclature: Flazasulfuron; annual bluegrass, Poa annua L. POAN; bermudagrass, Cynodon dactylon (L.) Pers. CYNDA; perennial ryegrass, Lolium perenne L. LOLPE.

Exploring Relationships in Surface-Hardness Data Collected With Different Instruments

Two instruments are used to measure impact attenuation on athletic field playing surfaces: the F355 Apparatus A (F355) and the Clegg Impact Soil Tester (CIST). Although both devices use weighted missiles equipped with accelerometers to measure impact attenuation, Gmax, little information is available in the peer-reviewed scientific literature comparing data collected with these devices on natural and synthetic turf athletic field playing surfaces. A 2-year field study was conducted at the University of Tennessee Center for Athletic Field Safety in 2012 and 2013 to determine whether data collected with a CIST could be used to predict values with the F355. Ten different synthetic turf and four natural turfgrass surfaces constructed over four root zone types were subjected to 30 simulated traffic events at two rates (three events wk−1 and 10 events wk−1). Three impact attenuation samples were collected with both devices on all surfaces for each rate of simulated traffic. Two regression analyses were conducted: one using all 252 data points collected annually and a second that incorporated blocking to account for within surface sampling. In both years, associations between impact attenuation data collected with the CIST and the F355 were weak. CIST values only explained 9 % of the variability in F355 data in 2012 (R2 = 0.09) and 24 % in 2013 (R2 = 0.24). When accounting for surface sampling, CIST values only explained 46 % of the variability in F355 data in 2012 (R2 = 0.46) and 56 % in 2013 (R2 = 0.56). Residuals around these best-fit regression lines were ±25 Gmax, indicating that the CIST cannot accurately predict impact attenuation values with the F355 within this range. Future research should continue to explore relationships between the F355 and CIST across diverse playing surface types and environments.

A New Device for Simulating Athlete-to-Surface Interactions on Natural and Synthetic Turf

Non-contact athletic injuries are the result of forces generated during athlete-to-surface interactions. Associations between playing surface conditions and injury incidence have been reported and numerous devices have been used to measure the vertical and horizontal forces occurring during athlete-to-surface interactions. However, nearly all of these instruments evaluate horizontal and vertical force separately. The objectives of this research were to (1) develop the Tennessee Athletic Field Tester (TAFT), an instrument for evaluating natural and synthetic playing surfaces that simultaneously generates realistic, peak vertical and horizontal forces that occur during athlete-to-surface interactions; (2) compare the simultaneous, peak vertical and horizontal forces measured by TAFT to values measured by an in-ground force platform at three simulated athlete weights and rates of horizontal velocity; and (3) determine the optimal rate of horizontal velocity for each simulated athlete weight to facilitate comparisons to force platform data. Peak vertical and horizontal force data were collected while operating TAFT on a force platform. The experimental design was the factorial combination of three athlete weights (75 kg, 85 kg, and 95 kg) and three horizontal velocities (500 mm s−1, 750 mm s−1, and 1000 mm s−1). At 1000 mm s−1, peak vertical force values with TAFT were greater than or equal to those captured by the force platform and similar to those reported using human subjects of similar weight. All TAFT configurations generated peak horizontal forces greater than those measured on the force platform and higher than have been observed in human subject trials. TAFT is a new instrument that generates peak vertical and horizontal forces that occur during athlete-to-surface interactions that may allow researchers to better characterize the safety of natural and synthetic turf playing surfaces.