Super Science: On-site testing for overseeded bermudagrass fairways

Entries were established in 100-square-foot plots, replicated three times where fairway traffic is evident and outside of landing zones. (Photo: David Gardener, Ph.D.)

Overseeding bermudagrass fairways is a common practice throughout the southern half of the United States. Golf courses purchase millions of pounds of seed sown each autumn on golf courses in this region. Golf course owners, managers and superintendents seek grasses that establish quickly, exhibit exceptional playability, are aesthetically pleasing and require fewer inputs. This project evaluates new and established cultivars for overseeding bermudagrass fairways at golf courses in the Southern and Western U.S.

The United States Golf Association (USGA) Green Section and the National Turfgrass Evaluation Program (NTEP) jointly sponsored this trial. This project’s information is valuable to the golfing industry because it determines the adaptation of grasses for golf course use. Information obtained from on-site testing will be of particular value to plant breeders, researchers, extension educators, USGA agronomists, golf course architects and superintendents who need to select the best-adapted cultivars for overseeding in a particular regional climate.

This project focuses on the use of saline water or sites that reduce water use by irrigation with lower evapotranspiration (ET) replacement rates.

The trial consists of not only single cultivars but also blends and mixtures of various species. Therefore, the test has 22 entries that consist of 10 ryegrass blends, nine single perennial ryegrass cultivars, one intermediate ryegrass, one annual ryegrass and one Poa trivialis. Three standard entries are in the trial (perennial ryegrass, intermediate ryegrass and Poa trivialis).

Trial sites were located on golf courses near a land grant university with a turfgrass research program or a metropolitan area accessible to a university turfgrass scientist (Table 1). The tests were maintained by the golf course superintendent at each location using management procedures common to their golf course and the geographical area and in consultation with the research cooperator. There were no unique management practices other than irrigation as these trials receive real-world golf course conditions and stresses.

The research cooperators established 100-square-foot plots, replicated three times where fairway traffic is evident and outside of landing zones. Trials were planted in fall 2016 and reseeded in fall 2017 with the same entries at the same physical location. Each year, the researchers recorded the establishment rate, turfgrass quality and color.

Table 1

Winter ratings focused on percent cover of overseeding grass, color, turfgrass quality, texture and growth rate. Spring and summer ratings consisted of color, turfgrass quality, texture and growth rate.

Additional spring ratings included the density and percentage of green cover of bermuda and overseeding grass during the transition back to 100 percent bermuda.

This article only presents the mean turfgrass quality for each trial location and year. The data for all the characteristics, years and sites can be accessed online at https://www.ntep.org/onsite/ost.htm.

Turfgrass quality is a measure of aesthetics (i.e., density, uniformity, texture, smoothness, growth habit and color) and functional use. Assessing turfgrass quality is a visual rating system based on the judgment of the turfgrass evaluator. The visual ratings collected on NTEP trials are based on a 1 to 9 rating scale.

A turfgrass quality value of 9 is considered outstanding or ideal turf, while a rating of 1 is lowest or dead. A rating of 6 or above is regarded as acceptable turfgrass. It is an excellent first impression of whether a cultivar or blend will work in your situation. You can spend more time evaluating the other characteristics recorded for a trial location in your region.

Table 2

As in past overseeding trials, entry performance varied significantly from one location to another. However, perennial ryegrass (PR) cultivars or blends performed the best across the nine test sites. We calculated the number of times an entry was equal to the top-performer using the LSD0.05 value for that location. For example, Stellar 3GL, Black Pearl (PPG-PR-308), Champion GQ, LCP-186 and Ringles were not significantly different from the top performer.

Considering only the five ET-based locations, SPR Spreading Ryegrass Overseeding Mix, Stellar 5GL, Black Pearl and Allsport 5 had mean turf quality ratings in the top statistical group at each site for both years.

For the three saline irrigation-based locations, the entries in the top statistical grouping at each site for both years include Champion GQ, Natural Knit, LCP-186, Futura 3000, Ringles and Stellar 3GL.

Entries with intermediate ryegrass (IR), Poa trivialis and annual ryegrass did not do as well as the best performers. Entries containing anywhere from 30 to 100 intermediate ryegrass or annual ryegrass did not perform well overall, with a few exceptions.

Futura 2500, a mix containing 30 percent intermediate ryegrass and 70 percent perennial ryegrass, performed well at the Las Cruces, N.M., and Lubbock, Texas, locations. The intermediate ryegrass entry Transist 2600 was a good performing entry with turf quality in the top statistical group at Stillwater, Okla.

It is also notable that one of the main selling points for annual or intermediate ryegrass is a better spring transition back to bermudagrass. Therefore, less than top turfgrass quality ratings may not be the only determining factor for choosing one of these entries.

Often overseeding results in fair to poor bermudagrass recovery in the spring or summer. Consider the following overseeding plan that avoids aggressive practices, which may injure the bermudagrass before winter dormancy (4):

• Do not verticut, but if verticutting is employed, set the blade depth to a quarter-inch above zero or higher. The higher depth will avoid damage to bermudagrass stolons and crowns.
• Increase mowing heights by 25 to 35 percent two weeks before overseeding preparations begin.
• One week before overseeding preparations, spray Turflon Ester Ultra (triclopyr) at 16 ounces per acre to slow bermudagrass growth. An alternative is to apply Primo (trinexapac-ethyl) at 10 to 15 ounces per acre. In general, when overseeding preparations begin at cooler temperatures, chemical growth regulation is not required due to decreased bermudagrass competition.
• Scalp bermudagrass at or just below the summer mowing height.
• Leave clipping debris on the surface as mulch for the incoming ryegrass.
• Continue irrigation to maintain adequate soil moisture and to avoid soil drying.
• At this point, the bermudagrass will still be green, but it is ready for overseeding. Once the seed is applied, use reel mowers set at the same scalping height to mow the seed into the turf canopy. The use of steel drag mats also helps the seed move into the bermudagrass understory.
• Following the first or second mow on the new ryegrass, spray Primo to promote ryegrass tillering and increase density.

More on NTEP

The National Turfgrass Evaluation Program (NTEP) develops and coordinates uniform evaluation trials of turfgrass varieties and promising selections in the United States and Canada. Test results are used by national companies and plant breeders to determine the broad picture of the adaptation of a cultivar. Also, the information is useful to assess cultivar adaptation to a local area or level of turf maintenance.

Briefly, the NTEP is a self-supporting, nonprofit program, sponsored by the Beltsville Agricultural Research Center, and the National Turfgrass Federation Program policy is made by a policy committee consisting of one member from each of the four Regional Turfgrass Research Committees in the United States, one member from the Lawn Seed Division of the American Seed Trade Association, one member from the United States Golf Association Green Section, one member from the Golf Course Superintendents Association of America, one member for the Turfgrass Producers International, one member from the Turfgrass Breeders Association, one member from the Oregon Seed Association and an executive director. The program does not recommend varieties. However, Extension specialists and others use the data from tests for making recommendations.

The policy committee is responsible for determining program policy including, (1) requirements for submission of entries, (2) scheduling tests, (3) evaluation methods, (4) selecting standard or control test entries, (5) setting entry fees, (6) coordinating tests in their respective regions, (7) establishing guidelines for publication and data distribution and (8) scheduling committee meetings.

Research takeaways

• This trial focused on the cultivar, blend and mixture performance of 25 entries, primarily under reduced (ET-based) water rates or saline (low-quality) irrigation water.
• Nine golf course sites, chosen based on geographic location and maintenance characteristics, were established in fall 2016 and 2017 in large plots on golf course fairways.
• Entries containing perennial ryegrass had the best overall turfgrass quality in the fall and spring for both trial years.
• There was some variation in the performance of entries at the ET-based reduced irrigation locations versus the saline irrigation locations.

Kevin Morris is the executive director of the National Turfgrass Evaluation Program. You can contact him at kmorris@ntep.com. Mike Kenna, Ph.D., is the research editor for Golfdom and can be reached at mpkenna@gmail.com.

References

1. Morris, Kevin. 2017. On-site testing of grasses for overseeding of bermudagrass fairways. Turfgrass and Environmental Research Program: 2017 Research Summaries. p. 315-318.

2. Morris, Kevin. 2017-18 On-site Overseeding Bermuda Data. Posted 1/28/18.

3. Morris, Kevin. 2016-17 On-site Overseeding Bermuda Data. Posted 12/8/17.

4. Whitlark, Brian. 2013. A New Era for Overseeding Preparation Strategies. Green Section Record. Vol. 51(19):1-5.