Performance and Safety Characteristics of Kentucky Bluegrass and Bermudagrass Athletic Fields Established On Sand- and Soil-Based Rootzones.

Bermudagrass (Cynodon spp.) and Kentucky bluegrass (Poa pratensis) athletic fields are often constructed on either sand- or soil-based rootzones. Side-by-side comparisons of the performance and safety of sand- and soil-based athletic field rootzones are limited, regardless of species. Therefore, a two-year study was conducted at the University of Tennessee Center for Athletic Field Safety (Knoxville, TN) in 2012 and 2013. Treatments were arranged in a randomized complete block, split-plot, design with three replications. Mature ‘Tifway’ hybrid bermudagrass (C. dactylon x C. transvaalensis) and a blend of Kentucky bluegrass (33% ‘Princeton 105’, 33% ‘Midnight’, 33% ‘Apollo’) was established over the following rootzones: 1) a Sequatchie silt loam; 2) a Sequatchie silt loam capped with 15 cm of sand meeting United States Golf Association (USGA) specifications; 3) a sand-based rootzone constructed to ASTM International specifications for athletic fields; and 4) a sand-based rootzone constructed to USGA specifications for golf course putting greens. Simulated traffic was applied to sub-plots with the CADY Traffic Simulator at rates 20 or six passes per week until 60 simulated traffic passes were applied each year. A non-trafficked sub-plot was included for comparison. Surface hardness [both with a Clegg Impact Soil Tester (CIST) and F355 apparatus], percent green cover, volumetric soil moisture content, and athlete-to-surface interaction data were collected. In 2012, no surface hardness differences were detected between turfgrass species or rootzones with the F355 device regardless of simulated traffic rate. However, when measured with a CIST, sand-based rootzones (3,4) measured lower in surface hardness than soil-based rootzones (1,2) regardless of traffic rate. Athlete-to-surface interaction testing revealed no differences in horizontal or vertical impact force due to turfgrass species or rootzone. Although, applying 20 passes per week with the CADY traffic simulator resulted in surfaces that exposed athletes to greater vertical and horizontal impact forces than those receiving six passes per week.