College of Agriculture & Natural Resources Department of Plant, Soil and Microbial Sciences

Crop and Soil Science Ph.D. Degree Final Thesis Defense: Ryan Bearss

August 17, 2026 9:00AM - 10:00AM

"From Farm to Field: Production, Reinforcement, and Management Strategies for Temporary Natural Turfgrass Systems"   

Members of the Examining Committee and their Department:

1. Trey Rogers–Plant, Soil and Microbial Sciences
2. John Stier–University of Tennessee, Plant Sciences
3. Emily Merewitz-Holm–Plant, Soil and Microbial Sciences
4. Kevin Frank–Plant, Soil and Microbial Sciences

 ABSTRACT  

Natural turfgrass playing surfaces used for high-profile sporting events must withstand intensive use while meeting strict performance standards. For some events, host venues may be required to provide a natural grass playing surface that meets tournament requirements. These temporary conversions require rapidly produced sod, reinforcement within the sod or root zone, and management that facilitates immediate use under tournament play. However, the methods used during production, establishment, and maintenance—and their effects on system maturity and performance—remain inadequately defined.

Sod grown on plastic (SOP) is a specialized solution that accelerates production and provides lay-and-play functionality, although premature harvest may limit vegetative maturity in some species. Mat-hybrid systems compensate by reinforcing the sod and playing surface; however, conventional cultivation practices may damage or bury their synthetic components, necessitating specialized maintenance practices, called hygiene. Post-installation management may also include plant growth regulators to reduce mowing requirements, although the effects of fixed weekly applications typical of tournament management programs on turfgrass aesthetics and traffic recovery remain unclear. Accordingly, three studies evaluated SOP production, hybrid hygiene during establishment, and fixed weekly trinexapac-ethyl applications to Kentucky bluegrass maintained over a temporary playing surface.

In 2023 and 2025, seven-month-old Kentucky bluegrass SOP was compared with 18-month-old conventionally grown sod for strength, maturity, growth, and rooting. Despite the 11-month age difference, SOP exhibited 52% greater tensile strength in 2023 and comparable strength in 2025. Sod on plastic also provided greater water infiltration. Post-transplant rooting varied between years and was not consistently influenced by sod production method. Limited rhizome development indicated that accelerated production enabled early harvest with the tradeoff of potentially sacrificing recuperative capacity.

Low-intensity cultivation programs were evaluated using weekly or monthly grooming, surface raking, or both during establishment of mat-hybrid-stabilized Kentucky bluegrass-perennial ryegrass SOP. Weekly programs reduced organic matter within the upper 44 mm by 9.6-16.7% relative to the nonhygienic control, whereas clipping collection had no consistent effect. Post-transplant performance responses were limited and varied between supporting profiles, which influenced surface characteristics more consistently than establishment hygiene. Combined weekly hygiene produced the greatest visible fiber cover but reduced tiller density by 27% in one run and green cover in both runs, indicating that moderate hygiene was sufficient during establishment.

Post-installation PGR management was investigated by evaluating the effects of six trinexapac-ethyl rates (0.0, 0.32, 0.64, 1.27, 2.55, 5.09 L ha^-1) applied weekly to Kentucky bluegrass maintained as a temporary playing surface. Thermal accumulation between applications ranged from 67.5 to 214.2 growing degree days, causing clipping suppression to vary significantly between applications. The three highest rates maintained >60% clipping reductions and occasionally increased chlorophyll or tiller density, reinforcing mowing management as TE’s primary practical value. Rates >1.27 L ha⁻¹ reduced quality and green cover, whereas rates ≤1.27 matched the nonregulated control for cover, quality, traffic recovery, and traction.

Collectively, these studies demonstrate that temporary natural playing surfaces can be produced rapidly and managed for immediate use, although accelerated production and intensive maintenance create tradeoffs among sod maturity, canopy preservation, and growth suppression. Moderate hybrid hygiene and weekly TE rates ≤1.27 L ha⁻¹ best balanced maintenance objectives with turfgrass quality and performance, while the supporting profile remained a primary determinant of post-installation surface behavior.