Our project addresses two critical needs: to update existing MnDOT turfgrass recommendation lists and to develop a new process to keep lists continually updated in a fair manner with data-driven recommendations. We evaluated the current list of MnDOT-approved turfgrass varieties and found underperforming varieties that should be removed. We then found new, improved varieties that should be considered for inclusion on the MnDOT lists. To facilitate a process to keep lists updated for the future, we first conducted a survey of seed distributors. Using their input, we developed a new process that MnDOT can use to approve turfgrass varieties for inclusion as official seed mixtures. Ultimately, this will lead to a more nimble, consistent, and clear process so that existing and new seed vendors can have complete confidence in data-driven decision making by MnDOT.
Analysis of genetic diversity and population differentiation determines how diverse natural populations are and how closely related they are to one another, which can provide clues concerning adaptation for restoration projects. This research analyzed the genetic diversity of three native species across their range in Minnesota. Using Amplified Fragment Length Polymorphisms, the genetic diversities of three species-prairie cordgrass (Spartina pectinata), purple prairie clover (Dalea purpurea), and spotted Joepye weed (Eupatorium maculatum)-were examined. The diversity for all the species had more disjunct relationships rather than displaying geographic or ecological patterns. The genotypic variation may be due to ecotypic variation or to genetic drift as a result of habitat fragmentation. The species had Gst values, a measure of how much populations differ, that ranged from 0.18 up to 0.27, indicating clear population differentiation. Analysis of molecular variance results concurred. The natural populations of all these species showed moderate levels of genetic diversity. This information is helpful in ensuring adequate diversity in seed sources for restorations. Additional research on these populations by performing common garden and reciprocal transplantation experiments would be a useful supplementation to the molecular marker data. For restorations in Minnesota, the best option may be to use seed that is as close as possible.
Roadsides are a challenging environment for successfully establishing turfgrass. Site-specific stresses demand multi-site testing of grasses and grass mixtures. This study evaluated 60 entries that varied by cultivar; species; or mixture by establishing on-site trials in MI; MN; NE; NJ; and WI. The entries tested included 50 individual cultivars and 10 standard mixtures; two from each participating state based on their current specifications. One location in each state was along an urban or suburban street with a curb; while the second location was along a rural highway without a curb having a ditch that slopes away from the road with a daily traffic volume of at least 30;000 vehicles. Plots were seeded at most sites in late summer 2016; and data were collected through spring 2018. Turfgrass performance was assessed by counting living turf cover; weed cover; and bare soil using the grid intersect method in the spring and fall of each year. Species and cultivar performance varied among locations. Several species showed potential for inclusion in effective mixtures. Other species performed well at some locations and poorly at others. Performance of standard mixtures was also inconsistent across locations. This research demonstrates the need for locally generated data on roadside turfgrass performance.
Our project was based on the need to water new roadside installations more efficiently to ensure that the turfgrasses; especially the new salt-tolerant mixes; establish more successfully with a predictable and uniform amount of water during the establishment period. The first objective of this project was to do a preliminary investigation of alternative means of irrigating new installations of salt-tolerant seed and sod mixtures. We completed the testing of four drip-tape-style irrigation systems placed both above and below sod; two above-ground sprinkler system configurations; and eight water truck nozzles. We then evaluated these new irrigation methods compared to current practices. We also developed an online voluntary training and education program for installers of roadside turf. And finally; we developed online maintenance training for homeowners to maintain new roadside turf installations. Based on our research; we recommend the use of 18-inch (45.7-cm) irrigation tape laid above the germination blanket (when seeding); or above sod when using a hydrant adapter with a programmable irrigation system as this system is easier and cheaper to install; can be removed and possibly reused after establishment; and results in reduced water use.
Current MnDOT specifications for roadside turfgrasses suggest statewide planting of mixtures that are grouped into five broad categories such as low maintenance turf and high maintenance turf. The objective of this research was to identify turfgrasses that possess traits necessary to survive in the harsh roadside environments found throughout Minnesota. We investigated the impacts of possibly the three most limiting environmental conditions (heat; salt and ice cover) on multiple cultivars from up to fifteen individual turfgrass species. Salt stress screening revealed several species with good levels of adaptation including alkaligrass and tall fescue. In the heat stress trial; we found cultivars and selections of Canada bluegrass; tall fescue; Kentucky bluegrass; strong creeping red fescue and slender creeping red fescue were among the top performers. Finally; in our ice cover screening; tall fescue and Chewings fescue did well; however; these results did not correlate well with our typical field observations. For each of these stresses; we identified top-performing cultivars that will be evaluated in field studies with the goal of identifying optimized mixtures for stakeholders in Minnesota.
Our goal was to develop seed mixture recommendations to improve establishment and development of roadside vegetation in Minnesota. We selected 14 research sites across Minnesota and seeded 40 turfgrass mixtures. Turfgrass coverage was assessed at each site twice a year and the weed seed bank was examined. We found that greater seeded turfgrass species richness was important for increasing and stabilizing roadside turfgrass coverage across space. We also found differences in the type and density of the weed seed bank at many sites, but its impact was relatively low on weed coverage over time. We considered soil and weather variables and found three significant seeding clusters for Minnesota consisting of two geographical seeding clusters (north and central/south) and one non-geographical cluster for sites with poor soil quality. Three new mixtures for each cluster were recommended for Minnesota. Implementing these mixtures will reduce soil erosion, improve aesthetics, save local communities’ financial resources, and improve the overall environment we occupy. As a complement to the field research, we developed cost prediction models that were incorporated into a detailed enterprise budget tool to calculate the roadside establishment costs that include labor, water, seed, sod, fertilizer, and other factors. This Excel-based tool can be used by local and state officials in determining budgets for roadside installations and which types or combinations of turfgrasses would be most cost effective, while also generating optimal performance.