Sod Strength Characteristics of 51 Cool‐Season Turfgrass Mixtures

CORE IDEAS: Turfgrass seed mixtures containing fine fescue species can produce sod that achieves equal or greater strength than those containing large amounts of Kentucky bluegrass when harvested 22 mo after establishment. Change in proportion of fine fescues from each initial seed mixture to the resulting final plant community was negatively correlated with sod strength characteristics. Thatch development was only weakly correlated with either maximum tensile load or work required to tear sod. Mixtures with different seed compositions, but resulting in similar or identical final species compositions, often possessed very different mechanical properties. Successful establishment of turfgrass on roadsides often necessitates using species mixtures not typically used for sod production. Evaluating mechanical characteristics of sod produced using such mixtures is necessary to determine if they possess sufficient strength for harvest and handling. The objective of this work was to evaluate tensile strength and work required to tear sod of mixtures of nine cool‐season turfgrass species previously determined to perform well on Minnesota roadsides. Three replications of 51 mixtures were established in a randomized complete block design at St. Paul and Rosemount, MN. Plots were seeded during September 2012 and harvested in July 2014. Tensile testing revealed that plots seeded with 40% strong creeping red fescue (Festuca rubra ssp. rubra Gaudin), 40% Chewings fescue [F. rubra ssp. fallax (Thuill.) Nyman], and 20% alkaligrass [Puccinellia distans (L.) Parl.] resulted in a final plant community comprising 99% fine fescues (Festuca spp.) and produced sod with the highest maximum tensile load to tear of 507.7 Newtons. At St. Paul, maximum work required to tear sod was 16.57 Nm for a final plant community comprising 98% fine fescues and 2% Kentucky bluegrass (Poa pratensis L.). At Rosemount, maximum work required to tear sod was 38.86 Nm for a final plant community comprising 90% fine fescue, 9% creeping bentgrass (Agrostis stolonifera L.), and 1% weed cover. Mixtures currently used on Minnesota roadsides containing high Kentucky bluegrass content were consistently among the weakest in the trial and sod comprising alternative species can match or improve the strength of those mixtures.