GCM

Mixing tall fescue with Kentucky bluegrass and perennial ryegrass

Fifteen years of research at University of Missouri show the benefits of turfgrass mixtures.

John H. Dunn, Ph.D.

Key Points

{short description of image}Turfgrass mixtures will have greater genetic diversity and be more disease resistant and more tolerant of pests and environmental stresses than a single species.

{short description of image}Species mixtures must be balanced, or dominance of one species will negate the benefits of the mixture.

{short description of image}Perennial ryegrass is best left out of mixtures for golf course fairways and roughs.

{short description of image}Additional research is needed, but tall fescue seeded 50:50 with Kentucky bluegrass remained competitive after three years.

Mixing turfgrass species may be advantageous because a mixture will have greater genetic diversity and exhibit greater tolerance of pests and environmental stresses than a single species.

Many turfgrass managers use mixtures of tall fescue (Festuca arundinacea) and Kentucky bluegrass (Poa pratensis L.) to provide the best of both species for athletic fields. Tall fescue, which has been used extensively for athletic fields in the transition zone for many years, has excellent traffic tolerance, but once damaged it is slow to recover. Kentucky bluegrass has rhizomes, which may enhance the healing process of a tall fescue + Kentucky bluegrass mixture once injury occurs.

Enhanced disease resistance
Mixtures may also be more resistant to disease. When Kentucky bluegrass in our plots was infested by dollar spot (Sclerotinia homoeocarpa), which is not a serious disease in tall fescue, mixtures retained better quality than Kentucky bluegrass alone. Because tall fescue is more susceptible to brown patch (Rhizoctonia solani) than Kentucky bluegrass, mixtures retain better quality than tall fescue alone in response to this disease.

Many golf course superintendents in the transition zone have attempted to grow Kentucky bluegrass in rough areas, but summer patch (Magnaporthe poae), perhaps the most serious disease of Kentucky bluegrass in the transition zone, makes this choice problematic.

The problem becomes exacerbated in the secondary rough where soil moisture may become less consistent than it is in the fairways or in the rough adjacent to fairways, and alternating wetting and drying worsens summer patch. In this situation, compatible Kentucky bluegrass + tall fescue mixtures may provide a viable alternative. In shaded or partly shaded rough, mixtures can be formulated that might include the inherently shade-tolerant tall fescue species and Kentucky bluegrass cultivars selected for shade tolerance.

We have had good success with Kentucky bluegrass + tall fescue mixtures cut at 5/8 to 7/8 inches during a 10-year interval and subjected to brief, but intensive, simulated traffic. Nevertheless, our studies lack the day-to-day stress found on the golf course, and superintendents should experiment, perhaps by renovating part of a fairway to Kentucky bluegrass + tall fescue mixtures, before making a long-term commitment.

Successful mixtures
To be successful, species mixtures must be balanced, or dominance of one species will negate the benefits of the mixture. Previously, it was not possible to mix tall fescue and Kentucky bluegrass because the fescue tended to segregate into patches in the established mixture. The newer, more aggressive turf-type tall fescues increased the probability that balanced mixtures could be attained.

The long-term objective of our three research projects, which began in 1985, is to determine the practicality of maintaining turf-type tall fescue in mixture with Kentucky bluegrass and perennial ryegrass (Lolium perenne L.) under varied management conditions.

Ten years of research at the University of Missouri have shown that after three to five years, perennial ryegrass will dominate in mixtures with tall fescue or Kentucky bluegrass at high (2-inch) and low (5/8- to 7/8-inch) mowing heights, with or without irrigation, and regardless of nitrogen rates of 1 to 4 pounds per 1,000 square feet per year. Because the dominant perennial ryegrass is highly susceptible to gray leaf spot, it is best left out of mixtures for golf course fairways and roughs. In the transition zone, perennial ryegrass is best used for overseeding athletic fields because it germinates and establishes more quickly than other species.

Long-term studies
The objective of our first study (1985-1989) was to determine whether compatible mixtures of tall fescue, Kentucky bluegrass and perennial ryegrass could be maintained at close mowing heights and under three nitrogen regimes. This research was the basis for K.L. Hunt's Ph.D. dissertation.

Results showed that selected, blended tall fescue cultivars under nonirrigated conditions can adapt to close mowing and remain competitive in mixture with selected, blended Kentucky bluegrass cultivars for several years. Under these same conditions, perennial ryegrass dominated both species in mixtures. Nitrogen and cutting height had little effect on botanical composition and had only occasional, minor effects on turfgrass quality.

The objective of the second study (1990-1995) was to determine the influence of several management factors on tall fescue, Kentucky bluegrass and perennial ryegrass growing in mixtures. Results showed that selected, blended tall fescue cultivars may be competitive in mixture with selected, blended Kentucky bluegrass cultivars under varied management conditions, including irrigation or no irrigation, close mowing and brief but intense traffic. The study also confirmed our earlier observations that perennial ryegrass will dominate in mixtures with tall fescue and Kentucky bluegrass. Disease incidence was a principal influence on turfgrass quality, and the advantage of mixing species for disease resistance was apparent.

Tall fescue is more susceptible than Kentucky bluegrass to brown patch (Rhizoctonia solani).
brown patch

Our latest study
Our most recent study (1995-present) attempted to determine the influence of seeding rate and Kentucky bluegrass blend composition on the competitiveness of tall fescue in mixture with Kentucky bluegrass.

Three Kentucky bluegrass blends - A (SR 2000 + SR 2010), B (Blacksburg + Midnight + Glade + Baron) and C (Limousine + Princeton 105 + America) - and a tall fescue blend (Houndog V + Jaguar III + Falcon II + SR 8210 + Rebel III + Mustang II) were seeded in September 1996. Mixtures of each of the three Kentucky bluegrass blends with the tall fescue blend were also seeded, with tall fescue comprising 90 percent (H), 50 percent (M), and 20 percent (L) of each mixture by seed weight for a total of nine mixture combinations.

The test was planted in two adjacent locations, one irrigated and the other not. Turf was mowed at 2 inches as needed and received 3 to 4 pounds N per 1,000 square feet per year, with most of the fertilizer applied in the fall.

In October 1999, blends and mixtures were recovering from summer drought. The Kentucky bluegrass blends shown here are dormant; the green plots are tall fescue blends and tall fescue + Kentucky bluegrass mixtures.
summer drought

Nonirrigated location
Tall fescue was the dominant species of mixture H at 71 percent after one year and 63 percent after three years. Mixture M consisted of 42 percent tall fescue at one year and 57 percent after three years. Kentucky bluegrass was the dominant species of the L mixture after one year, but declined by 30 percent from the first to the third year so that Kentucky bluegrass and tall fescue were evenly mixed at three years after seeding. Mixture A consisted of an average 58 percent tall fescue and 41 percent Kentucky bluegrass. Mixtures B and C were evenly balanced between the two species.

Irrigated location
Trends for mixture composition according to seeding rate were similar to that of the nonirrigated location except that Kentucky bluegrass appeared tobe more competitive in the irrigated location at three years after seeding, especially at the L (90 percent Kentucky bluegrass) seeding rate. Although tall fescue was the dominant component of mixture A in the nonirrigated location, the species were more evenly balanced in the irrigated location at one and three years after seeding. Mixtures B and C also showed good balance after three years with a difference between species of 10 percent or less.

The advantage of mixing species was evident on several occasions. For example, average summer 1999 quality rating for irrigated tall fescue was 5.5 (9 = best) and 5.0 for Kentucky bluegrass blend B; however, quality for the mixture of tall fescue + blend B was 6.3.

Results
Both seeding rate and Kentucky bluegrass blend composition affected mixture composition three years after seeding, depending on irrigation management. Tall fescue was competitive in mixture with Kentucky bluegrass at all seeding rates and in combination with all three Kentucky bluegrass blends.

Three to five years of additional research will be needed. For example, seeding date may be critical to success with mixtures. Late August, and September are often cited as the best times for establishing tall fescue and Kentucky bluegrass. Seeding in October and November may result in loss of seedling turf over the winter; therefore, it is difficult to predict what the balance of tall fescue to Kentucky bluegrass, in a late-seeded mixture, would be after five years.

How much seed should be used? In our earlier studies, we suggested 90 percent tall fescue by seed weight because we thought that tall fescue would need an early edge with the more aggressive Kentucky bluegrass. However, our most recent studies showed that a blend of tall fescue seeded 50:50 with Kentucky bluegrass by seed weight would remain competitive after three years. Still, we want to reserve judgment until we complete our five-year population counts in 2001.

Conclusions
In summary, the proven compatibility of newer turf-type tall fescues with Kentucky bluegrass in mixture gives golf course superintendents an option for turf in rough areas that was not practical 15 years ago. Furthermore, tolerance of many cultivars of both species to close mowing suggests that tall fescue-Kentucky bluegrass mixtures may have potential for transition zone fairways where alternatives to warm-season grasses are needed. On-site testing for a period of three to five years under fairway management conditions is needed to determine whether this is feasible.

Acknowledgments

The author thanks Ken Hunt, Ph.D., and Brad Fresenburg, University of Missouri-Columbia; Suleiman Bughrara, Ph.D., Michigan State University; and Erik Ervin, Ph.D., Virginia Tech University, for their participation in this research. The author also thanks the Mississippi Valley GCSA and the Heart of America GCSA for grants-in-aid to support parts of this research.

Literature cited

  1. Brede, A.D. 1993. Tall fescue/Kentucky bluegrass mixtures: effect of seeding rate, ratio, and cultivar on establishment characteristics. International Turfgrass Society Research Journal 7:1005A-1005G.
  2. Davis, R.R. 1958. The effect of other species and mowing height on the persistence of lawn grasses. Agronomy Journal 50:671-673.
  3. Hall, J.R. 1977. Effect of cultural factors on tall fescue-Kentucky bluegrass sod quality and botanical composition. p. 367-377. In: J.B. Beard (ed.), Proceedings of the 3rd International Turfgrass Research Conference, Munich, Germany. ASA, Madison, Wis.
  4. Harkess, R.D. 1970. Competition between tall fescue and perennial ryegrass in pure and mixed swards under simulated field condition. Journal of Applied Ecology 7:497-506.
  5. Hsiang, T., K. Carey, B. He and J.E. Eggens. 1997. Composition of mixtures of four turfgrass species four years after seeding under non-wear conditions. International Turfgrass Society Research Journal 8:671-679.
  6. Hunt, K.L., and J.H. Dunn. 1993. Compatibility of Kentucky bluegrass and perennial ryegrass with tall fescue in transition zone turfgrass mixtures. Agronomy Journal 85:211-215.
  7. Laycock, R.W., and P.M. Canaway. 1980. A new optical point quadrat frame for the estimation of cover in close mowed turf. Journal of the Sports Turf Institute 56:91-92.
  8. Sellmann, Mark. 1998. Kentucky bluegrass comes back to fairways. Golf Course Management 66(5):58-62.

John Dunn, Ph.D., is a professor of horticulture in the college of agriculture, food and natural resources at the University of Missouri-Columbia