Strength from the Ground Up: Measuring Sod Strength to Advance Turfgrass Research at Penn State

Welcome to The Turf Zone Podcast. This episode covers measuring sod strength to advance turfgrass research at Penn State. Written by Ava Veith, Zineb Alouani, Chase Straw and David Huff – Department of Plant Science, The Pennsylvania State University. Why Sod Strength Matters Long-term turfgrass stability is not controlled by a single factor, but rather by the interaction of turfgrass species, cultivar genetics, rootzone properties, and management practices. Turfgrass failure often becomes visible when the surface can no longer resist shear forces, whether during an athlete’s planting and pivoting movement, excessive divoting from golf play, or sod breaking apart during harvest and handling. In research plots, these weaknesses may appear as inconsistent performance from one area to another. Across athletic fields, golf courses, lawns, and sod farms alike, structural weakness limits turfgrass performance. At the center of these issues is sod strength. Sod strength refers to the resistance of the turfgrass–rootzone system to tearing or shearing forces. It reflects how effectively roots and other plant structures reinforce the turfgrass-root system. In other words, sod strength represents the physical integrity created by the interaction between turfgrass biology and the soil beneath it. Traditionally, turfgrass performance has been evaluated visually through percent cover, color, density, and recovery after wear. While those indicators are important, they do not directly measure structural stability. A surface may appear dense yet still lack strong structural integrity. Likewise, it may recover quickly but remain vulnerable to tearing under load. By directly quantifying structural integrity, objective measurements of sod strength allow turfgrass professionals to better connect turfgrass genetics, growth habits, and management practices with real-world durability. Expanding Turfgrass Research with Penn State’s New Sod Strength Tester With support from the Pennsylvania Turfgrass Council (PTC) Board of Directors, Penn State recently acquired a sod strength tester to expand its turfgrass research capacity. This equipment allows us to apply a controlled pulling force to turfgrass sod and directly measure the resistance of the turfgrass-rootzone system before tearing or shearing occurs. Unlike visual ratings or indirect indicators of performance, the sod strength tester generates objective and repeatable measurements of turfgrass structural integrity. It quantifies how effectively the turfgrass-rootzone system resists separation under load and how the turfgrass canopy holds together under stress. These measurements help translate turfgrass biology into measurable performance data. With this tool, Penn State can now evaluate structural stability across a range of systems, including athletic fields, golf courses, lawns, and sod production. Ultimately, PTC’s investment strengthens our ability to evaluate how turfgrass species, cultivar genetics, and management practices influence measurable durability in real-world turfgrass systems. Using the Sod Strength Tester in Turfgrass Research Several factors influence sod strength. Turfgrass species differ in growth habit and lateral spread, while cultivar genetics affect stolon and rhizome production, tillering capacity, and root mass. Rootzone composition influences the structural integrity of the turfgrass-rootzone system and moisture dynamics, and management practices such as fertility, irrigation, mowing height, traffic intensity, and cultivation further shape how the turfgrass system develops and responds to stress. By measuring sod strength, researchers can evaluate how these interacting factors influence structural performance under real-world conditions. At Penn State, the sod strength tester will be incorporated into multiple research initiatives led by faculty within the Department of Plant Science, including Dr