Make science-based decisions to protect your playing surfaces
By Dr. Jason Henderson, Brian Tencza and Dr. Karl Guillard
The mere thought of allowing a large vehicle to drive across one of your playing surfaces can inject a high level of trepidation in the most seasoned sports turf manager. Many current sports venues routinely host non-sporting events on their natural turf fields that often require a high volume of vehicular traffic over the playing surface to set up stages, seating, and other event-specific equipment. Retaining a playable surface throughout the event process poses a tremendous challenge to sports turf managers since many of these events occur during the season of play. Given the limited amount of time for re-establishing from seed, and the cost of resodding, there has been serious inquiry as to the most effective turfgrass cover protection system for maintaining the quality and integrity of the playing surface during the set-up, the event and the take down of non-sporting events.
Turf covers have been researched to enhance spring green up and turfgrass quality as well as extend the growing season in various regions. However, research on covers used to protect the playing surface from mechanical damage is lacking. Covers can be used to protect playing surfaces in several different types of situations and categorized accordingly such as static loads (chairs, stages or crane outriggers) and dynamic loads such as heavy vehicular traffic (trucks, forklifts or cranes), or light utility vehicles and foot traffic. This study focused on evaluating the effectiveness of different cover systems for protecting playing surfaces when subjected to heavy vehicular traffic. The objectives were to determine the effects of different cover types on turfgrass performance, soil physical properties, and surface displacement.
This study was conducted at the University of Connecticut Plant Science Research and Education Facility in Storrs, CT, during the 2010-2011 and 2011-2012 growing seasons. During the 2010-2011growing season, the study was performed on a mixed, 2-year old stand of Kentucky bluegrass and perennial ryegrass. During the 2011-2012 growing season, the study was performed on a 2-year old 100% Kentucky bluegrass stand. In both seasons, the study was initiated in June and repeated in August. The six turf protection systems evaluated were: 1) 0.75 in. Plywood only (2 layers), 2) Enkamat Plus and Plywood (2 layers), 3) Enkamat Flatback and Plywood (2 layers), 4) Supa-Trac (Rola-Trak North America), 5) TerraTrak Plus (Terraplas, Inc.), and 6) an uncovered control. Each turf protection system was evaluated over these cover durations: 3, 6, and 9 days. Treatments were subjected to two traffic events conducted on the first and last day of each cover period. Each traffic event consisted of 10 passes perpendicular to treatments with a loaded dump truck (GVWR = 20,000 lbs.).
The primary challenges associated with covering the turf system of an athletic field are minimizing any disruption to the surface and maintaining acceptable turf color, cover, and quality. The type of cover used will depend on the loads being applied to the playing surface and duration of the event being held. Given the load range tested, the plywood treatments provided the best protection against displacement, had the highest total porosity, and had the lowest bulk density values. There was little soil disturbance due to the plywood’s ability to displace the weight of the vehicle. There were no observed benefits when Enkamat Plus or Enkamat Flat was placed under the plywood for added protection. If covering turfgrass areas with plywood for more than 3 days, a considerable drop in percent green cover, turf color, and turfgrass quality should be expected. In addition to the limited cover period associated with plywood use, it can also be difficult to handle due to the size/weight of the individual 4 foot x 8 foot sheets and inevitably numerous wood splinters are likely to be left behind on the playing surface after the plywood has been removed.
TerraTrak Plus retained significantly better percent green cover and color, and had significantly higher turfgrass quality compared to all other cover treatments across all cover periods. Since TerraTrak Plus is made from a semi-translucent plastic, some photosynthetic light was able to pass through the cover enabling the turfgrass to maintain its green color. TerraTrak Plus retained better total porosity values, and displaced the load better than Supa-Trac, but not as well as any of the plywood treatments. Due to the thinness and/or the flex of Terra Trak Plus, the soil surface had some minor rutting at the load range tested.
Supa-Trac also did not perform as well as plywood and Terra Trak Plus regarding maintaining the integrity of the playing surface when subjected to a vehicular load. Supa-Trac is made out of a light, non-translucent plastic that has hinges along the surface allowing it to form to the undulations of the ground. This design did not allow Supa-Trac to displace the weight of the vehicle like the plywood treatments or TerraTrak Plus. This resulted in increased soil displacement, lower quality ratings and decreased total porosity values. Additionally, the underside of Supa-Trac was not flat. Instead, it had a raised rectangular grid pattern. When loaded by the vehicle, these raised ridges were forced into the ground and created a “honeycomb” impression on the soil surface.
Given the load range tested and the number of vehicular passes in this research, using two layers of 0.75 in. plywood resulted in minimal surface displacement. Although a single layer of plywood was not directly compared to two layers in this study, the top or bottom layer had a propensity to split during each traffic period. Therefore, a venue hosting an event subjecting the playing surface to heavy vehicular traffic (i.e. GVWR > 20,000 lbs. with similar tire size and number used in this study) should use a minimum of two layers of 0.75 in. plywood to resist compaction and soil displacement. However, the plywood should not be left down more than 3 consecutive days due to a reduction of turfgrass color and quality. Also, time must be allowed for cleaning up splinters left behind from the plywood.
If the playing surface is going to have lighter utility vehicle loads and foot traffic, a cover system like TerraTrak Plus may be a better alternative, enabling the sports turf manager to leave the covers on field for longer periods of time. Regardless of the cover type selected, athletic fields should be dried down before the cover period to reduce the amount of moisture that can accumulate at the soil surface/cover interface that would help reduce potential soil displacement. The optimal soil moisture content before applying covers is very difficult to specify since this range will depend heavily on the soil texture and organic matter content of the root zone material. For more information, the complete research article is published in Crop, Forage, & Turfgrass Management (DOI: 10.2134/cftm2014.0030). Tencza, B., J. Henderson, and K. Guillard. 2015. Protecting quality and integrity of turfgrass surfaces during non-sporting events with portable roadways. Crop, Forage and Turfgrass Management. 1(1):p. 1-11
Jason J. Henderson, PhD, is associate professor – turfgrass and soil sciences, University of Connecticut’s Dept. of Plant Science and Landscape Architecture. Brian Tencza is athletic field assistant at University of Connecticut; he was a graduate assistant at UConn when this study was conducted.