Sod Strength Characteristics of 51 Cool-Season Turfgrass Mixtures.

Successful establishment of turfgrass sod in low-maintenance applications often necessitates the use of species mixtures not typically used for sod production. Evaluation of mechanical characteristics of sod produced using such mixtures is necessary to determine if these mixtures have sufficient strength for harvest and handling. The objective of this work was to evaluate the shear and tensile properties of sod grown from seed mixtures of nine cool-season turfgrass species. Three replications of 51 mixtures were established in a randomized complete block design at both St. Paul and Rosemount, MN. Plots were seeded during September 2012 at a rate of 2 pure live seeds cm^-2 and maintained at 7.6 cm mowing height. Tensile testing of sod harvested in July 2014 revealed that a seed mixture of 40% strong creeping red fescue (Festuca rubra ssp. rubra), 40% Chewings fescue [Festuca rubra ssp. fallax (Thuill.) Nyman], and 20% alkaligrass [Puccinellia distans (L.) Parl.] produced sod with the highest maximum tensile load to tear of 507.7 Newtons, but was statistically similar to 11 other mixtures. In the top statistical grouping, seven mixtures contained strong creeping red fescue, seven contained hard fescue [Festuca trachyphylla (Hack.) Krajina], and six contained slender creeping red fescue (Festuca rubra ssp. litoralis). Those three species were seeded in more mixtures in the top statistical grouping than any other species in the trial. An assessment of the final species composition showed that there was no alkaligrass in plots of the 12 mixtures in the top statistical grouping, indicating that sod with the highest tensile strength and two other mixtures in the top grouping, were composed entirely of fine fescue species. These results show that sod produced using alternative species mixtures can match the strength characteristics of sod of commonly used species like Kentucky bluegrass.