By Dominic Christensen

The information contained in this blog post represents the views and opinions of the author. The view expressed herein does not represent the views or opinions of the Turfgrass Science Research group or the Department of Horticultural Science nor does publication of this post constitute an endorsement.

I write this final blog post as a farewell, a summary of the last chapter of the project toward which I dedicated three years, and briefly reflecting through a Christian lens. When I first arrived at the University of Minnesota – Twin Cities in 2014 I studied Environmental Sciences, Policy, and Management. During my undergraduate degree I focused on soil science and hydrology. After completing my undergraduate program, I started a master’s degree in Applied Plant Sciences in the department of Horticultural Science, co-advised by Drs. Jacob Jungers and Eric Watkins. Previously, I wrote a brief overview of my thesis research, but I have not expanded and reflected on the last chapter of my thesis.

One of my central goals was to develop new roadside seed mixtures for the State of Minnesota that were regionally based, which is why I selected 14 sites across Minnesota from International Falls near the Canadian border to Worthington in the far southwest part of the state (Figure 1). I studied this because the Minnesota Department of Transportation recommends only a few statewide turfgrass seed mixtures. I hypothesized that roadside seed mixtures for one corner of the state, such as Duluth, should be different from ones used in Marshall (about 300 miles away). These mixtures may differ by species, cultivars, or seed ratios.

After much thought, I determined that the original hypothesis was focused too narrowly on climate, and it was missing two key factors that influence turfgrasses: soils and site management, which both highly influence the growth and distribution of turfgrass in parks and lawns (Mintenko et al., 2002; Watkins et al., 2011) and on roadsides (Duell & Schmit, 1975; Friell et al., 2012; Hopkinson et al., 2016). Among these three factors, interactions exist suggesting that one factor can affect the other two. For instance, if a roadside is mowed at a lower height of cut than typical, one would hypothesize that more sunlight reaches the soil surface, which would result in a warmer than typical soil temperature, and soil temperature is in part contingent upon the amount of sunlight that a site receives influenced by the latitude. Therefore, an assessment of the climate alone would be limited.

After I distinguished these three factors, I determined it would be difficult to account for management in the analysis, because most sites were maintained at a mowing height-of-cut of 3.25 inches every few weeks. Nonetheless, accounting for soil and weather variables is still better than weather variables alone. Furthermore, based on the results of one chapter of my thesis, the data suggests that roadside turfgrass seed mixtures containing more species will have more coverage, and that coverage is more spatially stable. Therefore, whether the management is preferable or not, including more species provides additional coverage.

The analysis I performed with soils and weather variables was an agglomerative hierarchical cluster analysis (Milligan & Cooper, 1987). To do this, I collected 21 variables that are thought to influence turfgrass performance. Then I removed variables that were highly correlated and was left with 12 variables. The results of this analysis suggested three optimum groupings for restoring roadsides in Minnesota. The three groupings were distinguished by two geographical groupings of a northern grouping and a southern/central grouping, and a third which was primarily affected by soils denoted as a poor soil quality grouping. I learned that the poor soil quality sites often contained both the warmest and coolest soil temperatures in mid-summer and one of the coldest in the winter; these abiotic conditions can be stressful on plants, which is one reason why I found low coverage for sites classified in this grouping (Figure 2). I also learned that there are commonly differences in individual species coverage between the geographical groupings and the poor soil quality grouping and some differences among the geographical groups.

My results show that developing better roadside seed mixtures in Minnesota needs to consider both soils and weather variables to improve turfgrass establishment and long-term persistence. The statistical analysis also showed that future research should foremost focus on amending and developing better mixtures for sites with poor soil quality. I defined a poor soil quality site as either (1) exceeding at least two of the following: soil sand content > 55%, organic matter <= 2.2%, and bulk density >= 1.6 g/cm³; or (2) exceeding at least one of the following: soil sand content > 70%, organic matter <= 1.7%, or bulk density >= 1.8 g/cm³

Throughout the course of my plant science studies and research experience, I have often thought about the connections to my Christian faith. One interesting connection can be found in the Parable of the Sower from Chapter 13 of the Gospel of Matthew. Jesus analogizes man as a seed and groups man (seed) into four categories. The parable begins with a sower sowing seed and discusses that some fall on the path, some in the rocky places, others surrounded by thorns, and finally others on the good soil. Jesus identifies and discusses these areas in the spiritual life for his largely agrarian audience. In my research, the poor soil quality may represent the rocky places where it was difficult for the species of turfgrass I planted to survive (Figure 3).

As I reflect on restoring roadsides and turfgrass seed mixtures I consider that not until seed becomes a vegetative turfgrass plant will it bring benefit as roadside vegetation; similarly,  until man decides to become one who develops then produces fruit for the kingdom will he then become what his creator designed him for, for we were made for greatness. Let us be the ones who seek the good soil far from the path and thorns, or if we have little root, let us be open to the Word and willing to accept the amending we need. God clothes the grass and flowers of the field wonderfully indeed, but how much more will he clothe those in his kingdom.

References

Duell, R. W., & Schmit, R. M. (1975). Better Grasses for Roadsides. New Jersey Department of Transportation, Article FHWA/NJ-75-013-7726. https://trid.trb.org/view/1499659

Friell, J., Watkins, E., & Horgan, B. (2012). Salt tolerance of 75 cool-season turfgrasses for roadsides. Acta Agriculturae Scandinavica, Section B — Soil & Plant Science, 62(sup1), 44–52. https://doi.org/10.1080/09064710.2012.678381

Hopkinson, L. C., Davis, E., & Hilvers, G. (2016). Vegetation cover at right of way locations. Transportation Research Part D: Transport and Environment, 43, 28–39. https://doi.org/10.1016/j.trd.2015.12.011

Milligan, G. W., & Cooper, M. C. (1987). Methodology Review: Clustering Methods. Applied Psychological Measurement, 11(4), 329–354. https://doi.org/10.1177/014662168701100401https://doi.org/10.2135/cropsci2002.2018

Mintenko, A. S., Smith, S. R., & Cattani, D. J. (2002). Turfgrass Evaluation of Native Grasses for the Northern Great Plains Region. Crop Science, 42(6), 2018–2024. https://doi.org/10.2135/cropsci2002.2018https://doi.org/10.1016/j.trd.2015.12.011

Watkins, E., Fei, S., Gardner, D., Stier, J., Bughrara, S., Li, D., Bigelow, C., Schleicher, L., Horgan, B., & Diesburg, K. (2011). Low-Input Turfgrass Species for the North Central United States. Ats, 8(1), 1–11. https://doi.org/10.1094/ATS-2011-0126-02-RS