“Crumb Rubber Particle Size and Topdressing Depth to Improve Bermudagrass Athletic Field Performance”.

Crumb rubber (CR) is an amendment used to reduce surface hardness and increase wear tolerance on athletic fields. Turf managers can topdress several CR particle sizes to highly trafficked portions of athletic field turf; however, optimal particle size and topdressing depth combinations for use on bermudagrass athletic fields have yet to be determined. Therefore, research was conducted in 2011 and 2012 at the University of Tennessee Center for Athletic Field Safety (Knoxville, TN) to determine the optimal CR particle size and depth to maximize performance of hybrid bermudagrass (C. dactylon (L.) Pers. x C. transvaalensis Burtt-Davy, cv. ‘Tifway’) athletic field turf established on a Sequatchie silt loam soil. The experimental design was a randomized complete block with four replications. Treatments included the factorial combination of five CR particle sizes (0.25 mm, 0.50 mm, 0.50-1.00 mm, 1.00 mm, and 2.00 mm diameter) and three topdressing depths (0.64, 1.27 and 1.90 cm). All plots were subjected to 25 simulated traffic events with the CADY traffic simulator.  In 2011, surface hardness (SH) were lowest (44 Gmax) for the 1.90 cm depth, greatest for the 0.64 cm depth (52 Gmax), with the 1.27 cm depth ranking intermediate (48 Gmax). However, these differences were not observed in 2012. In 2011, CR particle sizes of 0.50 – 1.00 mm, 1.00 mm, and 2.00 mm at 0.64 cm depth measured higher in volumetric soil moisture content (VMC) than 2.00 mm CR at a 1.90 cm depth. However, these differences were not observed in 2012. The lack of differences for SH and VMC in 2012 may be a result of the bermudagrass being one year older; where, more thatch and sand topdressing accumulation occurred.  In conclusion, CR depth is more important then CR particle size.