Q: We are facing an urgent issue with our football field. Over the last few years, our field has gradually declined in quality, but this year it has reached a critical state. After we sprayed out the winter ryegrass, there has been very little bermudagrass regrowth. The field looks extremely poor, and we are unsure how to proceed. We have received conflicting advice and we are concerned about making the wrong decision. We have 75 days before our first scheduled game (mid-August).
A: Upon visiting the high school field, I found the conditions consistent with the description provided via email. Bermudagrass coverage was minimal, with only a few semi-healthy patches visible. The extra water and fertilizer they were adding were mostly encouraging algae rather than turfgrass recovery. Typically, bermudagrass fields that were previously overseeded should exhibit at least 80% coverage by this time of year. The few existing patches were attributed to sod inlays used to repair damaged areas a couple of years ago.
It is well documented that perennial ryegrass overseeding can delay bermudagrass green-up. A common strategy to mitigate this is to chemically remove the ryegrass as the bermudagrass begins to emerge from dormancy. This reduces competition and typically accelerates bermudagrass recovery. In this case, the ryegrass had been appropriately removed; however, bermudagrass growth remained negligible, indicating a deeper underlying issue.
I noted the field’s unusually soft surface and extracted soil samples for closer examination. The field’s soil profile had an excessively thick organic thatch layer. While an acceptable thatch layer is generally no more than half an inch, most sampled areas exhibited layers between one and three inches. Living rhizomes and healthy white roots were difficult to locate.
Excessive thatch significantly increases the risk of winterkill and spring dead spot disease in bermudagrass. It also leads to shallow rooting, making the turfgrass more vulnerable to environmental stress. Additionally, a thick thatch layer creates a spongy surface that retains excess moisture – encouraging algae and disease. When this layer dries, it can become hydrophobic, impeding water infiltration and further stressing the turfgrass.
According to the coaches and the school administrator, the field has deteriorated gradually over several years. The rapid accumulation of thatch is typically the result of management practices that both encourage its formation and fail to control its buildup. Effective thatch management usually involves a combination of vertical mowing, aerification and sand topdressing. Following the retirement of the previous field manager, the school began contracting with a local landscape company for basic maintenance. It appears that the contracted scope of work did not include any thatch management practices.
Given the extent of turf loss and thatch accumulation, a full field renovation is likely necessary to restore optimal playing conditions. While fraise mowing can be used to remove moderate thatch levels, the depth of removal required in this case will likely eliminate viable rhizomes. As a result, replanting the field with sod or sprigs will be necessary. Sprigging is the most cost-effective option, but it will need to be initiated quickly to ensure the field is ready for the first game.
Grady Miller, Ph.D.
Professor and Extension Turf Specialist
North Carolina State University
Questions?
Send them to Grady Miller at North Carolina State University, Box 7620, Raleigh, NC 27695-7620, or e-mail grady_miller@ncsu.edu
Or send your question to Pamela Sherratt at 202 Kottman Hall, 2001 Coffey Road, Columbus, OH 43210 or sherratt.1@osu.edu