In theory, mixtures of warm- and cool-season grasses seem practical because the optimum growth conditions for each species should complement one another, with cool-season grasses growing well in spring and fall and warm-season grasses growing best in the summer.2 However, the consequence of these mixture attempts often is a patchwork quilt appearance that results in undesirable turfgrass uniformity and quality.
Research was initiated to study the potential of overseeding fine-leaved fescues into established buffalograss turf and to improve turfgrass color and quality. The first studies investigated species, seeding rate and date, and core cultivation effects on overseeding establishment and buffalograss performance with turfs maintained as golf course roughs. Recent studies investigated overseeding effects when turfs were maintained under fairway conditions.
ROUGH OVERSEEDING STUDIES
Overseeding date and rate studies were conducted for two years on buffalograss turfs maintained as roughs at the University of Nebraska John Seaton Anderson Turfgrass Research Facility located near Mead, Nebr. Three fine-leaved fescues (SR 3100 hard fescue, SR 3200 blue fescue, and SR 5100 chewings fescue) were used in both studies. Fall, spring, and fall-spring seedings were compared in the seeding date study.
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| Figure 1. Turfgrass quality ratings for overseeded buffalograss when blue fescue was seeded in fall, fall/spring, or spring (i.e., 1-9 visual rating scale with 1 = poorest and 9 = best). |
In the seeding rate study, seed rates of 2.0, 4.0, and 6.0 lbs. of pure live seed/1,000 sq. ft. were compared. The fine-leaved fescues were overseeded into mature stands of buffalograss that were mowed down to one inch with mowing debris removed. The turfs were core cultivated prior to applying seed. After seeding, the cores were broken up and a starter fertilizer was applied at 1.0 lb. N/1,000 sq. ft. Turfs were irrigated sufficiently to maintain a moist soil to enhance fine fescue seedling establishment. After establishment, turfs received 2.0 lbs. N/1,000 sq. ft. and were mowed weekly at 2.5 inches with clippings returned.
FAIRWAY OVERSEEDING STUDIES
A second set of buffalograss overseeding trials was conducted in 2004 and 2005. Buffalograss cultivars maintained as fairway turfs were overseeded with Bighorn blue fescue at 1.0 and 2.0 lbs./1,000 sq. ft. in early September. Bighorn blue fescue was selected as the overseeding species based on its drought resistance, low-fertility performance, and its grayish, blue-green color. Establishment procedures were the same as those described for the seeding rate and date trials except for the mowing height and frequency differences. Buffalograsses were mowed three times per week at 0.63 inches and received 2.0 lbs. N/1,000 sq. ft. per season and 1.0 inch water per month, either as irrigation, rainfall, or both.
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| Figure 2. Turfgrass color ratings for overseeded buffalograss when blue fescue was seeded in fall, fall/spring, or spring (i.e., 1-9 visual rating scale with 1 = straw brown and 9 = dark green). |
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| Figure 3. Turfgrass species composition (i.e., percentage of each species) when blue fescue was seeded in fall, fall/spring, or spring. |
RESULTS OF SEEDING RATE AND DATE STUDIES
In the seeding date studies, fall overseeding gave the best turfgrass quality and color, and highest shoot density ratings compared to spring or fall-spring plantings (Figures 1, 2, and 3). Spring overseeding had the lowest shoot densities, and fall-spring seeding was mostly intermediate in response. Fine fescue shoot density was highest in May and declined gradually through September, when it began to increase with the onset of cooler soil temperatures. Buffalograss composition increased during the summer months, as expected.
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| Figure 4. Percentage of turfgrass species composition based on fine fescue seeding rates of 2.0, 4.0, and 6.0 lbs./1,000 sq. ft. (10, 20, and 30 g/m2). |
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| Figure 5. Turfgrass quality ratings for overseeded buffalograss when fine fescue was overseeded at 2.0, 4.0, or 6.0 lbs./1,000 sq. ft. (10, 20, and 30 g/m2) (i.e., 1-9 visual rating scale with 1 = poorest and 9 = best). |
Fall overseeded blue fescue had the highest ratings for turfgrass quality and color throughout the study (Figures 1 and 2, respectively). The blue-green color of blue fescue blended well with buffalograss, giving a better season-long performance compared to the other fine-leaved fescue species studied. Buffalograss mixed with chewings or hard fescues exhibited more summer stress than the blue fescue mixtures, but all turfs expressed a decline in turfgrass quality during the summer stress period (Figure 1).
Fall overseeded blue fescue-buffalograss mixtures maintained acceptable quality ratings during summer stress periods. Research conducted in Utah reported similar findings with blue fescue and buffalograss mixtures.3 In our studies, Chewings fescue overseeding treatments gave unacceptable turfgrass quality when buffalograss was dormant, due primarily to the lack of uniformity in turfgrass appearance.
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| Figure 6. Mean turfgrass quality ratings for buffalograss cultivars overseeded with Bighorn blue fescue in fall 2004 compared to those same buffalograss cultivars not overseeded with Bighorn blue fescue. |
There was a linear response for increased shoot density and turfgrass quality and color ratings as seeding rates increased from 2.0 to 6.0 lbs./1,000 sq. ft. (Figures 4 and 5). Turfgrass quality and color ratings followed similar trends. Turfgrass quality ratings were highest for the 6.0 lbs./1,000 sq. ft. treatment (Figure 5). In Utah, fine-leaved fescue seeding rates of 2.0 and 4.0 lbs./1,000 sq. ft. in a buffalograss overseeding study resulted in similar shoot density and quality responses.3 Shoot density seemed to stabilize around a 3:1 ratio of fine fescue to buffalograss shoots when overall seeding rates and the entire growing season were considered (Figure 4). Fine-leaved fescue composition was highest in May and decreased while buffalograss increased from late spring to early fall.
Recent trends in developing more aggressive, high-temperature-tolerant cool-season turfgrass cultivars may decrease the competitive advantage of warm-season turfgrasses during summer stress periods.5 Two years after establishing these studies, fall overseeded blue fescue comprised 75% and buffalograss 25% of the turfgrass stand. This composition was slightly less than the > 80% fine fescue reported in the Utah study.3
FAIRWAY OVERSEEDING RESULTS
Overseeding buffalograss cultivars maintained under fairway mowing heights with Bighorn blue fescue resulted in improved turfgrass quality when compared to non-overseeded grasses (Figure 6). The Bighorn blue fescue seemed to blend well with the buffalograss from a color perspective. Turfgrass color and quality ratings were higher for turfs overseeded with 2.0 versus 1.0 lbs./1,000 sq. ft. of Bighorn blue fescue. Turfgrass quality ratings over the growing season differed by cultivar, with Prestige having the highest mean quality rating for the season (Figure 6). Prestige is a tetraploid cultivar that is planted vegetatively and has demonstrated earlier spring green-up when compared to the other cultivars tested in this trial. It also tends to hold its green color longer into the fall season.
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| Figure 7. Turfgrass color rating of buffalograss cultivars overseeded with blue fescue and compared to those same buffalograss cultivars not overseeded. Ratings were made in November 2005 (i.e., 1 to 9 visual rating scale with 1 = straw brown and 9 = dark green). |
Turfgrass color ratings taken in November 2005 demonstrated the benefit of overseeding buffalograss with blue fescue (Figure 7). The non-overseeded buffalograss color ratings ranged from 1.0 to 2.9 and represent the typical color of dormant buffalograss turfs, while the overseeded turfs had color ratings ranging from 5.0 to 7.1.
The results from the seeding rate and date studies and those from the fairway buffalograss trials indicate that buffalograss turfs overseeded with blue fescue in the fall provide improved quality and color and extend the green appearance both earlier and later in the growing season. Spring overseeding resulted in poor turfgrass establishment, lack of uniformity, and lower turfgrass quality ratings than fall or fall-spring overseedings. Turfgrass quality, color, and shoot density responded linearly to fine fescue overseeding rates for buffalograss maintained at rough heights of cut.
In the later fairway study, lower seeding rates of 1.0 to 2.0 lbs./1,000 sq. ft. of blue fescue provided satisfactory turfgrass quality ratings and extended turfgrass green cover well into November. Blue fescue overseeded in the fall extended the green cover response by more than two months in the rough-height-of-cut study. The results obtained in these trials support the use of blue fescue and buffalograss mixtures as a means of enhancing turfgrass color retention and prolonging the green cover response compared to non-overseeded buffalograss turfs.
ACKNOWLEDGEMENTS
The United States Golf Association, Nebraska Turfgrass Association, and University of Nebraska Agricultural Experiment Station provided funding in support of this research. Special appreciation is expressed to Leonard A. Wit for his supervision of the care and maintenance of these research trials.
Editor's Note: A complete report of this study and other research can be found at USGA Turfgrass and Environmental Research Online (http://usgatero.msu.edu). The specific URL for this report is http://usgatero.msu.edu/v05/n09.pdf.
LITERATURE CITED
1. Beard, J. B. 1973. Turfgrass: science and culture. Prentice Hall, Englewood Cliffs, N.J.
2. Davis, R. R. 1958. The effect of other species and mowing height on persistence of lawn grasses. Agron. J. 50:671-673.
3. Johnson, P. G. 2003. Mixtures of buffalograss and fine fescue or streambank wheatgrass as a low-maintenance turf. HortScience 38:1214-1217.
4. Shearman, R. C., T. P. Riordan, and P. G. Johnson. 2004. Buffalograss. Pp. 1003-1026. In L. E. Moser, B. L. Burson, and L. E. Sollenberger (eds.). Warm-season (C-4) grasses. Agronomy Monograph No. 45. Am. Society of Agronomy. Madison, Wis.
5. Turgeon, A. J. 1991. Turfgrass management. Prentice Hall, Englewood Cliffs, N.J.
R. C. Shearman, Ph.D., Professor, Agronomy and Horticulture, University of Nebraska, Lincoln, Nebr.; S. Severmutlu, Western Mediterranean Agricultural Research Center, Antalya, Turkey; T. P. Riordan, Ph.D., Director, Professional Golf Management Program, University of Nebraska, Lincoln, Nebr.; U. Bilgili, Ph.D., Assistant Professor, Department of Field Crops, Faculty of Agriculture, Uludag University, Bursa, Turkey.
