grassland restoration network

By Kevin Scheiwiller, Restoration Manager, Barrington Illinois

While attending the 2019 GRN Workshop in Madison, I was particularly impressed with the prairie restorations the Madison Audubon Society was undertaking. Young restorations of old brome fields already had a great display of matrix prairie species after just three years of planting. They had first burned and then sprayed glyphosate before seeding in the sod. After listening to how they approached these restorations, I was inspired to try a variation on their technique on some brome fields Citizens for Conservation recently acquired. In the past, we commonly would seed heavily into brome fields and rely on fire to eventually knock out the Eurasian grass sod. Anecdotal results using this approach for the last 10 years has had some positive results, but often a dense sod of brome will remain with only scattered clumps of native matrix species starting to break through. We decided to compare the two methods side by side and track the progression of each and make a quasi-experiment out of it.

Hypothesis:

Mow, then spray then seed Vs. Seed only: Stimulating growth of Hungarian Brome (Bromus inermis) through a late summer mowing followed by treatment of 3% Glyphosate in the Fall to set back the brome grass sod (as typically one spraying does not kill the sod but weakens it) will increase germination rates of prairie seedings over areas where brome is left intact.

Site Description:

The study site is an old hay meadow with the dominant species being Bromus inermis. There is scattered Tall Goldenrod (Solidago altissima) mixed in some of the study plots, but not in numbers that will drastically alter species composition.

Methods:

The site has been separated into 10 plots, 5 received Treatment 1 and 5 plots received Treatment 2. The study site is approximately 100’ by 170’. The plots were created by “eyeballing” the center point of the field on an East-West axis and creating study blocks every 30’ on the North-South axis. Figure 1 shows the study plots. A recent updated photo from Google maps reveals that the “eyeballing” techniques left plots rather uneven in shape and size. The center of each plot was staked with a wooden post for subsequent monitoring.

Treatment 1 – Mow, glyphosate, seed:

• Areas mowed with a Gravely brand brush mower at a 4” depth on August 30, 2019. The mowing is meant to stimulate the growth of this cool season grass thereby increasing the uptake of herbicide. Madison Audubon Society uses late Summer burns for the same effect. Due to smoke concerns in a highly residential area, mowing was substituted for this experiment.
  • A 3% Glyphosate solution (4oz/gal of RoundUp Custom with 1oz/gal of non-ionic surfactant and turf marker) was applied a few weeks later on September 20, 2019.
  • Each plot seeded with 5 gallons of Dry Prairie Mix and perlite on November 20, 2019. The mix consisted of 9.3 ounces of 33 species of hand picked and processed (aka chaffy) seed mix. We seeded at an approximate rate of 17 pound per acre. See attached seed list for species and approximation of the weight distributed.  

Treatment 2 – Seed only:

• Each plot seeded with the same 5 gallons of Dry Prairie Mix and perlite on November 20, 2019

Results after one Growing Season:

Plots were surveyed on September 13^th, 2020 and a colleague, Karen Glennemeier, graciously crunched the data. The comparison between the two treatment types are as follows:

Management Implications and Ongoing Monitoring

As observed through the Madison Audubon’s restorations, the pre-treatment of Brome with mowing (or fire) and initial Glyphosate treatment produced a much more diverse assemblage of plants the following growing season. This treatment was not too intensive for the small plots but scaling up would require a large amount of time and/or equipment. The big question moving forward now is will the “Business as Usual” plots catch up to the treated plots? If both plots end up evening out in species abundance and distribution over the next decade, then is it worth the effort to pretreat the brome? Time will tell and data will continue to be collected.

Figure 1 –  Study Area: Plots 1,4,5,8,9 received mow, spray, and seed; Plots 2,3,6,7,10 received seed only

Figure 2 – Pretreatment August 30, 2019

Figure 3 – August 30, 2019 after mowing. 5 plots were mowed, sprayed with glyphosate 21 days later and then seeded. 5 plots were left unmowed but seeded same day as treatment

Figure 4 – November 20, 2019 Seeding each plot with ~5 gallons of Dry Prairie Mix

The author forgot to take a picture during the growing season of 2020 which would have been helpful for the sake of this article. The same error will not be repeated in 2021.

Dry Prairie Seed Mix broadcast on November 20, 2019