Sod Research at Purdue (2019-2022 summary)
Aaron Patton and Ross Braun
Sod is an important specialty crop in the northern U.S., representing over $549 million in combined sales from the Northeast, Midwest, Plains, and Northwest regions of the US, and this value is expected to increase. Sod is important for new construction to prevent soil erosion and increase ecosystem services from turfgrass in urban and suburban areas. Recent genetic improvements in low-input turfgrass species now provide sod farms new options besides Kentucky bluegrass when selecting what to plant. Since the selection of turfgrasses (either low or high-input) by sod farms ultimately impacts the level of input required by those receiving sod installations (homeowners), decisions made by sod farmers and landscape contractors can have a tremendous impact on the environment and efforts to manage turf sustainably.
Since 2018, Purdue University and the University of Minnesota have been investigating sod production in research funded by the USDA. We wanted to learn more about producing both tall fescue as well as fine fescue sod. Strong creeping red fescue (Festuca rubra ssp. rubra), because of its rhizome system, performed well in our study. Results from this sod research also shows us that there is much variability in horizontal spread between genotypes of strong creeping red fescue. This indicates there may be potential differences among cultivars within a fine fescue species or subspecies which we are studying in 2022-2023.
Additionally, preliminary results from a The Lawn Institute-funded experiment in 2020 at Purdue University is showing that strong creeping red fescue is producing the highest strong strength, slender creeping red fescue (F. rubra ssp. littoralis) is the next highest, and then Chewings fescue and hard fescue (Festuca brevipila) is the lowest sod strength among fine fescues. Preliminary results from this experiment is also demonstrating that plant genetics and not nitrogen fertilization has the greatest impact on sod strength.
Our team continues to research how to produce the best turfgrass sod possible in the Midwest. Here is a list of some key takeaways from our research projects:
- Increasing seeding rate or N fertilizer rates provides negligible benefits in producing sod.
- Higher annual N fertilizer rates are likely required for Kentucky bluegrass sod to promote faster establishment (i.e., shorter sod production period) and increase sod strength.
- Strong creeping red fescue consistently provided highest sod strength and handling.
- Chewings fescue provided less sod strength than strong creeping red fescue at both sites, but, at times, similar as Kentucky bluegrass, especially in Minnesota likely because of the cooler climate.
- Tall fescue sod with no netting consistently provided poor sod strength and handling, therefore, plastic netting is strongly recommended for tall fescue sod.
- Strong creeping red fescue, Chewings fescue, and tall fescue were able to establish to 100% turf cover faster, therefore, may have shorter sod production time periods compared to Kentucky bluegrass, which has slower establishment and may require an additional 2 to 4 months.
- Seeding rate had no effect on growth rate or transplant success of sod.
- Reduced growth rates were measured in fine fescues, especially Chewings fescue, thus lower mowing requirements (i.e., less annual mowing events)
- After 24 or 72-h storage, all species provided successful sod transplant.
- Annual mowing events below is based on fully-established turfgrass during growing season; however, during first year of establishment, fine fescues may need to mowed 1 to 2 times during fall (i.e., first 3 months of establishment), tall fescue would need to be mowed 2 to 3 times during fall (i.e., first 3 months of establishment), and Kentucky bluegrass may 0 to 1 mowing event during fall establishment period due to slower establishment.
- Most seed mixtures evaluated in our studies produced high quality sod similar to the standard comparison of 100% Kentucky bluegrass sod.
- Sod mixtures containing fine fescues generally produced greater sod strength and handling if the mixture contained at least 33% strong creeping red fescue due to its rhizomatous growth habit. This includes strong creeping red fescue mixed with Kentucky bluegrass or other fine fescue species.
- Sod mixtures containing tall fescue, including “rhizomatous tall fescue” consistently resulted in the weakest sod strength across sod harvest timings.
Our work shows that Kentucky bluegrass is and continues to be the dominant cool-season turfgrass species choice for northern United States sod farms because it produces high-quality turf, producers are more acquainted with its production cycle. Sod farms in central and northern Indiana may be hesitant to try a different turfgrass species, such as strong creeping red fescue but our research shows it is a viable option.
Our future sod research in the coming years will focus on which fine fescue cultivars make the best sod. Also, we will be evaluating new, cold-hardy zoysiagrass cultivars for their sod strength. If you have any questions about this work, don’t hesitate to contact me at firstname.lastname@example.org.