The Pennsylvania State University. The Graduate School. College of Agricultural Sciences AN EVALUATION OF THE TRAFFIC TOLERANCE OF

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1 The Pennsylvania State University The Graduate School College of Agricultural Sciences AN EVALUATION OF THE TRAFFIC TOLERANCE OF TURF-TYPE TALL FESCUE SEEDED IN LATE SPRING A Thesis in Soil Science by Michael A. Shelley 2012 Michael A. Shelley Submitted in Partial Fulfillment of the Requirements for the Degree of Master of Science August 2012

2 The thesis of Michael A. Shelley was reviewed and approved* by the following: Andrew S. McNitt Professor of Soil Science Thesis Advisor Peter J. Landschoot Professor of Turfgrass Science Michael A. Fidanza Professor of Plant and Soil Sciences Jack E. Watson Professor of Soil Science Interim Department Head of Crop and Soil Sciences *Signatures are on file in the Graduate School. ii

3 ABSTRACT Traffic from sporting events and other activities often causes major loss of turfgrass ground cover on high school athletic fields. These fields are used most heavily during the fall and spring seasons. In the northeast United States (US), this time period coincides with the active growing season for cool-season turfgrass species. Field renovations often occur during the summer months and while not ideal for cool-season turfgrass establishment, this is typically the only portion of the growing season when fields are not in use. Selecting appropriate turfgrass species, cultivars, and maintenance practices that maximize traffic tolerance during this summer establishment period have not been thoroughly investigated. In the northeast US, three turfgrass species are commonly used for athletic fields: Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.) and tall fescue (Schedonorus phoenix (Scop.) Holub) [formerly Festuca arundinaceae Schreb.]. However, the establishment time varies between these species: perennial ryegrass < tall fescue < Kentucky bluegrass. Although perennial ryegrass establishes quickly from seed, this species may not perform as well as other species during the summer in the northeast US. During the summer, tall fescue has a greater tolerance for heat, drought, and is generally more disease resistant when compared to perennial ryegrass. Tall fescue may offer field managers a more heat tolerant alternative to the established practice of overseeding with perennial ryegrass. New turf-type tall fescue cultivars are available that have greater tiller density and finer leaf texture compared to older cultivars. Increased tiller density has been correlated to increases in iii

4 traffic tolerance; however, the establishment time required for tall fescue cultivars to develop traffic tolerance has not been investigated. Researchers have reported that more rapid turfgrass ground cover can be achieved by increasing seeding and nitrogen rates. For example, seeding above the standard recommended rates has been reported to increase perennial ryegrass traffic tolerance when traffic is initiated within three months after seeding. The objectives of this research were to 1) compare the late summer/fall traffic tolerance of spring seeded perennial ryegrass and 11 tall fescue cultivars, 2) evaluate the influence of four seeding rates and three nitrogen regimes on the traffic tolerance of turf-type tall fescue 10 and 14 weeks after seeding, and 3) evaluate if the measurable turfgrass physiological characteristics, morphological characteristics, and shear strength can be used as a screening indicator to predict the traffic tolerance of tall fescue cultivars under various maintenance regimes. In Experiment I, 11 tall fescue cultivars and one perennial ryegrass cultivar were established on a silt-loam soil in 2010 and The cultivars included RK4, Falcon V, Rebel IV, ATF 1376, Turbo, Shenandoah III, Kentucky-31, Justice, Firecracker LS, Rembrandt, Faith, and Fiesta IV perennial ryegrass. All cultivar treatments were seeded on the same date in the late spring, regardless of the traffic treatment. Simulated traffic was applied from early August through late November using the Brinkman Traffic Simulator. Three traffic levels were used: 1) no traffic 2) traffic initiated 10 weeks after seeding, and 3) traffic initiated 14 weeks after seeding. Traffic was applied with 4 passes, three days per week. Both the 10- and 14-week traffic treatments ended on the same date in late iv

5 November. Thus the 10-week traffic treatment received 4 additional weeks of traffic compared to the 14-week traffic treatment. Percent ground cover differences due to cultivar treatments were observed weekly from August through November of each year. When traffic was initiated 10 weeks after seeding, perennial ryegrass had higher traffic tolerance than all tall fescue cultivars. However, when traffic was initiated 14 weeks after seeding, all turf-type tall fescue cultivars had greater or equal traffic tolerance compared to perennial ryegrass. Turbo was consistently among the top performing turf-type tall fescue cultivars. Differences in traffic tolerance were observed among the remaining 10 turf-type tall fescue cultivars, but these differences were small and not consistent from year to year. In Experiment II, seeding rate treatments consisted of four rates of turf-type tall fescue, which were applied in either late May or early June. The seeding rates were 294, 490, 686, and 882 kg ha -1. Three nitrogen regimes were evaluated: 98.0, 220.5, and kg N ha -1. All three regimes received approximately 98 kg N ha -1 at seeding due to the nitrogen released from Basamid. The nitrogen from the Basamid is the only nitrogen applied to one nitrogen regime treatment. This treatment is referred to as the 98 kg ha -1 nitrogen regime. In addition to the nitrogen from the Basamid, the and kg ha -1 nitrogen regimes received monthly applications of ammonium sulfate, which began 8 weeks after seeding when all plots had reached 100% ground cover. Simulated traffic was applied using the same method and intensity described in Experiment I. v

6 Seeding rate and nitrogen regime treatments influenced the traffic tolerance of turf-type tall fescue. The low nitrogen regime (98 kg ha -1 ) maximized traffic tolerance regardless of the seeding rate and traffic treatment. Seeding rates did not influence traffic tolerance when evaluated independently of nitrogen regimes and traffic treatments. However, during a dryseason, when the establishment period was limited to 10 weeks, traffic tolerance was affected by seeding rate and nitrogen regime combinations. A low seeding rate (294 kg ha -1 ) with a high nitrogen regime (343.0 kg ha -1 ) or high seeding rate (882 kg ha -1 ) with low nitrogen regime (98 kg ha -1 ) resulted in equally high traffic tolerance. The morphological characteristics, leaf angle, tiller density, and verdure correlated with traffic tolerance when turf-type tall fescue cultivars were maintained equally. However, a consistently strong correlation between any one these characteristics and traffic tolerance was not evident. When morphological characteristics such as tiller density and leaf angle were influenced by seeding rate and nitrogen treatments, traffic tolerance was not increased. In conclusion, limited research exists that evaluates the influence of seeding rate and nitrogen regime combinations on tall fescue traffic tolerance. The goal of this research was to determine if tall fescue is a viable option during summer establishment for athletic fields. Morphological and physiological characteristics that may explain traffic tolerance between tall fescue cultivars were also evaluated. Results of this study suggest that turf-type tall fescue is an acceptable alternative to perennial ryegrass when adequate summer establishment time exists prior to athletic field use. Generally, the seeding rates in this study did not positively or negatively influence traffic tolerance. The nitrogen fertility regime did have an influence on traffic tolerance; the lowest vi

7 nitrogen regime (98 kg ha -1 ), applied all at once before seeding, consistently resulted in greater late summer/fall traffic tolerance. Athletic field managers that have at least a 14 week establishment period in the summer should consider using turf-type tall fescue to maintain turfgrass ground cover on their fields during the fall sporting season. vii

8 TABLE OF CONTENTS LIST OF FIGURES...x LIST OF TABLES... xi ACKNOWLEDGEMENTS... xii INTRODUCTION...1 LITERATURE REVIEW...5 History of Tall Fescue...6 Evaluating Turfgrass Traffic Tolerance...8 Species Evaluation...8 Interspecies Wear Tolerance Mechanisms...10 Intraspecies Wear Tolerance Mechanisms...11 Traffic Intensity and Type...13 Athletic Field Establishment Practices...16 Establishment Time Prior to Traffic Evaluation...16 Role of Nitrogen in Turfgrass Growth and Traffic Tolerance...17 Impact of Nitrogen on Plant Growth...18 Nitrogen Applications during Turfgrass Establishment...19 Nitrogen Fertilization and Traffic Tolerance...19 Effect of Seeding Rate on Turfgrass Morphology and Traffic Tolerance...21 Seeding Rate Effects on Turfgrass Characteristics Shortly after Seeding...21 Influence of High Seeding Rates on Turfgrass Ground Cover when Traffic is Initiated Shortly after Seeding...23 JUSTIFICATION...26 OBJECTIVES...27 MATERIALS AND METHODS...28 Nitrogen Release from Basamid...29 Simulated Traffic Application...31 Criteria Used to Evaluate Treatments...32 Percent Ground Cover...32 Physiological Characteristics...32 Morphological Characteristics...34 Shear Strength...35 Experiment I: Traffic Tolerance Characteristics of Select Tall Fescue Cultivars...36 Cultivar Selection...36 Plot Establishment...36 viii

9 Plot Maintenance...37 Rating Dates and Statistical Analysis...39 Experiment II. The Effects of Seeding Rate and Nitrogen Fertility during Summer Establishment on the Traffic Tolerance of Turf-type Tall Fescue...41 Plot Establishment...41 Applied Treatments...41 Plot Maintenance...43 Rating Dates and Statistical Analysis...45 RESULTS...46 Experiment I. Traffic Tolerance Characteristics of Select Tall Fescue Cultivars...46 Percent Ground Cover during Grow-in...47 Percent Ground Cover after Traffic Initiation...56 Physiological and Morphological Characteristics of Tall Fescue...66 Experiment II. The Effects of Seeding Rate and Nitrogen Fertility during Summer Establishment on the Traffic Tolerance of Turf-type Tall Fescue...75 Percent Ground Cover during Grow-in...76 Percent Ground Cover after Traffic Initiation...83 Physiological and Morphological Characteristics of Tall Fescue DISCUSSION CONCLUSIONS BIBLIOGRAPHY APPENDIX: ADDITONAL MATERIALS ix

10 LIST OF FIGURES Figure 1. Clipping yields from plots established with Basamid and 3 nitrogen rates at 294 kg seed ha -1 in Figure 2. Mean turfgrass ground cover values for cultivar main effect during first five rating dates of 2010 grow-in...50 Figure 3. Mean turfgrass ground cover values for cultivar main effect during first five rating dates of 2011 grow-in...51 Figure 4. Mean turfgrass ground cover values for seeding rate main effect during first five rating dates of 2010 grow-in...79 Figure 5. Mean turfgrass ground cover values for seeding rate main effect during first five rating dates of 2011 grow-in...80 Figure 6. Average monthly rainfall for 2010 and x

11 LIST OF TABLES Table 1. Nitrogen application rates and dates for the 3 nitrogen regimes in Table 2. Cultivar main effect prior to traffic for turfgrass ground cover in Table 3. Cultivar main effect prior to traffic for turfgrass ground cover in Table 4. Cultivar main effect during first five grow-in dates for turfgrass ground cover in Table 5. Cultivar main effect during first five grow-in dates for turfgrass ground cover in Table 6. Cultivar and traffic treatment main effects and interactions for turfgrass ground cover in Table 7. Cultivar and traffic treatment main effects and interactions for turfgrass ground cover in Table 8. Mean ground cover values on 4 rating dates, 3 weeks apart, for cultivar treatments under traffic in Table 9. Mean ground cover values on 4 rating dates, 3 weeks apart, for cultivar treatments under traffic in Table 10. Mean turfgrass ground cover values for the traffic treatment main effect in Table 11. Mean turfgrass ground cover values for the traffic treatment main effect in Table 12. Mean values for cell wall components measured on 11 tall fescue cultivars and 1 perennial ryegrass cultivar in Table 13. Mean values for cell wall components measured on 11 tall fescue cultivars and 1 perennial ryegrass cultivar in Table 14. Mean values for measured characteristics on 11 tall fescue cultivars and 1 perennial ryegrass cultivar in Table 15. Mean squares and mean values for measured characteristics on 11 tall fescue cultivars and 1 perennial ryegrass cultivar in xi

12 Table 16. Pearson correlation coefficients (n=36) between tall fescue ground cover values (20 Nov.: 10-week treatment) and turfgrass characteristics in Table 17. Pearson correlation coefficients (n=36) between tall fescue ground cover values (17 Nov.: 10-week treatment) and turfgrass characteristics in Table 18. Seeding rate main effect prior to traffic for turfgrass ground cover in Table 19. Seeding rate main effect prior to traffic for turfgrass ground cover in Table 20. Mean turfgrass ground cover values for seeding rate main effect prior to traffic in Table 21. Mean turfgrass ground cover values for seeding rate main effect prior to traffic in Table 22. Traffic treatment, seeding rate, and nitrogen regime main effects and interactions for turfgrass ground cover in Table 23. Traffic treatment, seeding rate, and nitrogen regime main effects and interactions for turfgrass ground cover in Table 24. Mean turfgrass cover values for seeding rate main effect under traffic in Table 25. Mean turfgrass ground cover values for seeding rate main effect under traffic in Table 26. Mean turfgrass ground cover values for the traffic treatment main effect in Table 27. Mean turfgrass ground cover values for the traffic treatment main effect in Table 28. Mean turfgrass cover values for nitrogen regime main effect under traffic in Table 29. Mean turfgrass ground cover values for nitrogen main effect under traffic in Table 30. Mean turfgrass cover values for traffic treatment by nitrogen regime in Table 31. Mean turfgrass cover values for traffic treatment by nitrogen regime in Table Nov mean turfgrass ground cover values for the traffic treatment by seeding rate by nitrogen regime interaction...98 xii

13 Table Nov mean turfgrass ground cover values for the traffic treatment by seeding rate by nitrogen regime interaction...99 Table 34. Mean squares and mean values for plant characteristics in turf-type tall fescue in response to 4 seeding rates and 3 nitrogen regimes applied in combination in Table 35. Mean squares and mean values for plant characteristics in turf-type tall fescue in response to 4 seeding rates and 3 nitrogen regimes applied in combination in Table 36. Mean values for cell wall components in turf-type tall fescue in response to 4 seeding rates and 3 nitrogen regimes applied in combination in Table 37. Mean values for cell wall components in turf-type tall fescue in response to 4 seeding rates and 3 nitrogen regimes applied in combination in Table 38. Pearson correlation coefficients (n=36) between tall fescue ground cover values (8 Nov.: 10-week treatment) and turfgrass characteristics in Table 39. Pearson correlation coefficients (n=36) between tall fescue ground cover values (17 Nov.: 10-week treatment) and turfgrass characteristics in Table 40. Mean turfgrass ground cover for cultivar main effect in Table 41. Mean turfgrass ground cover for cultivar main effect in Table 42. Mean turfgrass ground cover values for cultivar treatment by traffic treatment interaction in Table 43. Mean turfgrass ground cover values for cultivar treatment by traffic treatment interaction in Table 44. Mean turfgrass ground cover values for seeding rate by nitrogen regime interaction under traffic in Table 45. Mean turfgrass ground cover values for seeding rate by nitrogen regime interaction under traffic in Table 46. Mean turfgrass cover values for traffic treatment by seeding rate interaction in Table 47. Mean turfgrass cover values for traffic treatment by seeding rate interaction in xiii

14 ACKNOWLEDGMENTS First, I would like to thank my family for supporting my decision to go back to graduate school. Your constant encouragement and financial support allowed me to leave a full-time job to take advantage of a once in a lifetime opportunity. Thanks to Tom Serensits and Dianne Petrunak. It was a pleasure to work with your on many different projects. Your willingness to help me on a moment s notice and answer all of my questions was appreciated more than you would believe. Thanks to all of the Penn State graduate students, professors, staff, and Valentine Research Center crew. I won t forget how much each of you contributed to the success of my stay at Penn State. Lastly, I d like to thank my thesis committee: Drs. Andrew McNitt, Peter Landschoot, and Michael Fidanza. Andy, thanks for giving me the opportunity to study and learn under your guidance. Pete and Mike, thanks for suggestions with this project and always being available to talk about anything. xiv

15 INTRODUCTION The growing popularity of sports in the United States (US) (NFHS, 2009) has increased the demand for athletic field use. At the high school level, athletic fields are used for sporting events and other activities throughout the school year. In Pennsylvania, the interscholastic sporting season begins in mid-august with football and soccer and continues through May with baseball, lacrosse, and track and field. These playing seasons coincide with the growing seasons for coolseason turfgrass. Intense use during these seasons reduces field playability and quality and doesn t allow for recovery during the summer and winter. In order to provide safe, playable, and aesthetically appealing fields, grounds managers have the option to install synthetic fields, renovate their existing fields with sod, or reestablish heavily trafficked areas with seed. However, due to the high costs of synthetic fields and sod, seeding is the only feasible renovation option for most high schools. Owing to the stringent fall and spring sporting event schedules, the time frame for athletic field renovations is limited to the late spring and late fall. Unfortunately, the short establishment period between May and August is not the optimum time to establish cool-season turfgrass species in the northeast US (Christians, 2007). Limited rainfall and high air and soil temperatures inhibit shoot and root growth during the short period between May and August (Turgeon, 2011). Also, disease pressure is high in the summer when high temperatures and humid environments favor pathogen growth (Vargas, 1994). In response to these challenges, turfgrass managers need to select the most appropriate turfgrass species and cultivars to quickly establish traffic tolerant athletic fields. 1

16 In the northeast US, three turfgrass species are commonly used for athletic fields: Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.) and tall fescue (Schedonorus phoenix (Scop.) Holub) [formerly Festuca arundinaceae Schreb.] (Sherratt et al., 2005). All three can provide adequate, although not equal, wear tolerance once a mature turfgrass stand is established (Youngner, 1961; Shearman and Beard, 1975b; Minner and Valverde, 2005b). These species vary in their germination and establishment rates (Puhalla et al., 1999). When short renovation periods exist, field managers often choose to seed perennial ryegrass because it quickly establishes turfgrass cover (Harkess, 1970). Although perennial ryegrass establishes quickly, this species sometimes does not perform as well as other species during the summer in the northeast US. Perennial ryegrass is less drought tolerant than tall fescue and requires moderate to high fertilizer inputs (Scheffer et al., 1987). During the summer, moisture from irrigation and high nitrogen fertility can exacerbate disease activity (Landschoot, 1995). Perennial ryegrass is particularly susceptible to gray leaf spot, pythium blight, and brown patch under conditions where management inputs are designed to promote rapid growth (Watschke et al., 1995). The challenges of establishing this species during the summer can make the renovation process more complicated and possibly more costly. Athletic field managers in the northeast US would benefit from a turfgrass species that establishes quickly and is better able to withstand summer conditions. 2

17 Tall fescue has a greater tolerance for heat, drought, and disease stresses when compared to perennial ryegrass during summer months in the northeast US (Turgeon, 2011). The germination period is similar to perennial ryegrass in which seeds germinate in 5-7 days; however, perennial ryegrass establishes 100% turfgrass ground cover faster than tall fescue. While mature stands of tall fescue have been shown to be more traffic tolerant than perennial ryegrass (Shearman and Beard, 1975b), young tall fescue stands are believed to require longer establishment periods to reach their maximum traffic tolerance and practitioners suggest waiting 4-9 months between seeding tall fescue and field-use (Puhalla et al., 1999; Sherratt et al., 2005; Stier and Koertz, 2008). Establishment practices can influence the speed to establishment and traffic tolerance of a turfgrass stand. Nitrogen fertilizer is commonly applied during seeding and throughout much of the growing season. Supplying adequate levels of nitrogen increases tillering and density. Higher density turfgrass stands have been shown to improve traffic tolerance in seashore paspalum (Paspalum vaginatum Swartz.), bermudagrass, and tall fescue (Trenholm et al., 2000, Park et al., 2009). Similar to nitrogen fertilization, increasing seeding rates initially results in a more dense turfgrass stand shortly after seeding (Madison, 1966). The effects of nitrogen rates and seeding rates on traffic tolerance have been evaluated separately (Canaway, 1984; Hoffman et al, 2010a; Crossley, 2006; Minner et al., 2008); however, the two practices have not been studied together. An optimum combination of nitrogen and seed rates may help to maximize the fall traffic tolerance of turf-type tall fescue athletic fields established in the summer. While high nitrogen and seeding rates have been recommended for perennial ryegrass (Hoffman et al., 2010a; Minner 3

18 et al., 2008), little information exists to suggest if this approach is appropriate for summer establishment or how these rates affect tall fescue traffic tolerance. Selecting turfgrass cultivars with specific growing characteristics may also influence traffic tolerance. Newer cultivars of turf-type tall fescue exhibit a finer leaf texture and increased density (Funk et al., 1981). The leaf orientation of a turfgrass plant may also affect how turfgrass stands distribute the forces of traffic (Brosnan et al, 2005). Brosnan et al. (2005) reported that wear tolerant cultivars of Kentucky bluegrass exhibited a more upright leaf angle compared to wear intolerant cultivars. Traffic tolerance among turf-type tall fescue cultivars may be described by a combination of these growing characteristics: leaf texture, tiller density, and leaf angle. Extensive research has focused on speeding establishment and maximizing traffic tolerance of athletic fields (Canaway, 1985; Stier et al., 2008; Vanini and Rogers, 2008). However, these studies have concentrated primarily on perennial ryegrass and Kentucky bluegrass. Turf-type tall fescue may be used in place of these species during a three month summer establishment period and therefore warrants further investigation. 4

19 LITERATURE REVIEW High school athletic fields are commonly subjected to traffic caused by sporting events, team practices, and other activities. The most common stress from these events is foot traffic (Minner et al., 1993), which adversely affects the visual and playing quality of the field (Carrow and Petrovic, 1992). Traffic, in this study, will refer to the combination of two stresses: wear and compaction. Wear is defined as the direct injury to plant tissues by pressure, scuffing, abrasion and tearing, while compaction is the pressing together of soil particles, which adversely alters soil physical properties (Carrow and Wiecko, 1989). Researchers should recognize that some studies focused only on turfgrass wear tolerance. In these studies any type of compaction forces were avoided. Although athletic fields always receive stresses from both wear and compaction, these researchers wanted to separate the two stresses and focus on wear. Turfgrass traffic tolerance differences may be due to species selection, fertility levels, plant maturity, and wear timing, intensity, and type (Gaussion, 1994; Bonos et al., 2001; Minner and Valverde, 2005a). This literature review is divided into two sections and will review research that has attempted to investigate the effects of each of these parameters. The first section will focus on how traffic tolerance varies among turfgrass species and cultivars. The second section will focus on nitrogen fertility and seeding rates and how these two cultural practices influence turfgrass growth and traffic tolerance. 5

20 History of Tall Fescue Tall fescue (Schedonorus phoenix (Scop.) Holub) [formerly Festuca arundinaceae Schreb.] (USDA, 2012) is a bunch-type turfgrass species that is used extensively where it has adapted in cooler regions and transition zone of the United States (Juska et al., 1969). The transition zone has been defined as an area where neither cool- or warm-season turfgrass performs well; the region is too hot for cool-season turfgrass species and too cool for warm-season species (Juska et al., 1969). Tall fescue performs well in areas receiving limited irrigation and fertilization (Sheffer et al., 1987; Walker et al., 2007). Lower maintenance is required to grow tall fescue compared to perennial ryegrass and Kentucky bluegrass, which makes it an adequate turfgrass species to use for forages, road sides, residential lawns, parks, and potentially for golf course roughs and naturalized areas (Samples et al., 2009). However, turfgrass managers that maintain athletic fields and golf courses avoid using tall fescue because it mixes poorly with other turfgrass species. Cultivars such as Kentucky-31 and Arid have a medium to coarse leaf texture, low shoot density, and light green color. During recovery from damage, these cultivars tend to form clumps due to its strong bunch-type growth, which are not desirable for sporting activities (Minner, 1993). In 1979, Rutgers University (North Brunswick, NJ) released a new tall fescue cultivar, Rebel (Funk et al., 1981). It was the first turf-type tall fescue cultivar that had improved aesthetic characteristics compared to older forage-types like Kentucky-31. Specifically, this cultivar exhibited a finer leaf texture, higher shoot density, and dark green color. These visual characteristics make turf-type tall fescue cultivars a compatible component in turfgrass mixtures 6

21 that contain Kentucky bluegrass (Gibeault et al., 1993). In addition to improved visual characteristics, turf-type tall fescue cultivars are more tolerant to lower cutting heights and show potential to be bred for improved disease resistance to brown patch (Rhizoctonia solani) (Watkins et al., 2009). 7

22 Evaluating Turfgrass Traffic Tolerance Species Evaluation Kentucky bluegrass (Poa pratensis L.), perennial ryegrass (Lolium perenne L.) and tall fescue are commonly used turfgrass species for athletic fields in the northeast US. All three exhibit good wear tolerance compared to other cool-season turfgrasses (Youngner, 1961; Shearman and Beard, 1975b). Youngner (1961) was the first to evaluate wear tolerance of cool-season and warm-season turfgrasses. He used an accelerated wear machine, which could apply two types of wear: a scuffing and abrasive type of wear from four corrugated feet or a punching and tearing wear from two spiked rollers. Treatments with the wear machine were applied to solid stands of turfgrass maintained with similar maintenance until no turfgrass remained. The results of this study showed that Alta tall fescue was the most wear tolerant to both scuffing and spiked wear, followed by Merion Kentucky bluegrass and perennial ryegrass. Shearman and Beard (1975b) also evaluated the tolerance of cool-season turfgrasses under the stress of wear. A mechanical wear simulator was created that applied two types of wear: wheel wear and sled wear (Shearman et al., 1974). Wheel wear was applied by a pneumatic tire that rotated around a pivot point to simulate wear from maintenance equipment. Sled wear was applied by a weighted sled that was connected by a tow arm and was designed to simulate the crushing and tearing from foot wear. The turfgrass species evaluated included Pennlawn red fescue (Festuca rubra L.), Cascade chewing fescue (Festuca rubra commutata L.), Kentucky- 31 tall fescue, Manhattan perennial ryegrass, Merion Kentucky bluegrass, Italian ryegrass 8

23 (Lolium multiflorum Lam.) and rough bluegrass (Poa trivialis L.). These species were seeded in early May and wear began on 20 Sept. Under wheel wear, perennial ryegrass was the most wear tolerant, followed by Kentucky-31 tall fescue and Merion Kentucky bluegrass. Under sled wear, Merion, Manhattan, and Kentucky-31 were equally wear tolerant when rated by visual quality. However, when the researchers used percent verdure (the amount of turfgrass tissue remaining after mowing) to determine wear tolerance, Merion was the most wear tolerant. Differences in the cool-season wear tolerance rankings were apparent between Youngner (1961) and Shearman and Beard (1975b). Youngner (1961) found Alta tall fescue to be the most wear tolerant under both spike and scuff wear, while Shearman and Beard (1975b) found Kentucky-31 tall fescue to be less wear tolerant than Merion Kentucky bluegrass under sled wear and equally wear resistant to Kentucky bluegrass and perennial ryegrass under wheel wear. Shearman and Beard (1975b) noted that differences in cultivars and environmental factors may explain the discrepancies between the wear rankings. Manhattan perennial ryegrass did not exist when Youngner (1961) conducted the study and this species may have an improved wear tolerance compared to the perennial ryegrass cultivar used by Younger (1961). Youngner s study was conducted in the transition zone in California, which may have favored tall fescue and resulted in its higher wear tolerance. These performance variations among species showed that characteristics specific to each turfgrass type may be useful to explain wear tolerance. 9

24 Interspecies Wear Tolerance Mechanisms Researchers have identified cool-season turfgrass species that have improved wear tolerance and would be appropriate species for use on athletic fields. In an attempt to identify and improve the wear tolerance of each of these species, specific plant characteristics have been evaluated and correlated to wear tolerance. Identifying these unique characteristics can provide more efficient screening techniques for breeders and researchers. However, plant characteristics that explain wear tolerance between turfgrass species do not always explain wear tolerance within species. The following two sections will discuss wear tolerant mechanisms at the inter and intraspecies levels. Shearman and Beard (1975c,d) were the first to correlate physiological, morphological, and anatomical characteristics of turfgrass species to wear tolerance. Shearman and Beard (1975c) found that total cell wall content (TCW), lignocellulose, cellulose, and hemicellulose, expressed as mg/dm 2, were significantly correlated to wear tolerance among seven cool-season species. The combination of all cell wall constituents accounted for 97% of the variation at the interspecies level. Shearman and Beard (1975d) further evaluated physiological, morphological, and anatomical characteristics associated with wear tolerance at the interspecies level. Physiological and morphological differences were observed in verdure, shoot density, load bearing capacity, leaf blade tensile strength and percent moisture, but none of the individual characteristics were significantly correlated to wear tolerance. Only the combined relationship between leaf tensile 10

25 strength and leaf width correlated significantly with wear tolerance. Anatomical characteristics were studied between a wear tolerant species, Kentucky-31 tall fescue, and an intolerant species, rough bluegrass. The improved wear tolerance was related to both lignified tissues and percent sclerenchyma. Intraspecies Wear Tolerance Mechanisms Characteristics of traffic tolerant turfgrasses have been studied at both the inter and intraspecies levels. Unfortunately, characteristics that explain traffic tolerance between different species do not always correlate to characteristics that explain traffic tolerance within a species. Research is limited in the number of turfgrass species that have been evaluated for either wear or traffic tolerance characteristics at the intraspecies level. Plant characteristics including shoot density (Youngner et al., 1961; Trenholm et al., 2000; Brosnan and Deputy, 2009), leaf width, and leaf strength (Shearman and Beard, 1975d; Trenholm et al., 2000) influence wear tolerance in coolseason and warm-season turfgrass species at the interspecies level. However, these plant characteristics do not appear important when evaluating intraspecies traffic tolerance among Kentucky bluegrass cultivars (Brosnan et. al, 2005). Intraspecies wear tolerance characteristics for tall fescue have been limited to visual quality ratings (Shildrick and Peel, 1980) and density evaluations (Park et al., 2009). When evaluating entries of the 2006 National Turfgrass Evaluation Program (NTEP) tall fescue trial and 2005 Cooperative Breeder s Test in North Brunswick, NJ, Park et al. (2009) found that density and turf quality were positively correlated to wear tolerance. The newest turf-type tall fescue 11

26 cultivars that were dense and rate highest in turf quality prior to wear had a greater wear tolerance than older turf-type cultivars that rated lower in these characteristics. In the 2001 NTEP tall fescue trial, Tar Heel II, Falcon IV, and Padre were among the most wear tolerant entries (Park et al., 2009), but in the trials, those cultivars performed worse than the newer cultivars. Density and visual quality ratings are good indicators of tall fescue wear tolerance, but only relying on these two characteristics may not be sufficient. In the 2001 NTEP tall fescue trial in East Lansing, MI, not every cultivar with high quality ratings performed well under traffic stress (Bughrara, 2007). Similarly, Park et al. (2009) observed cultivars that performed well under wear, but these cultivars only had average densities prior to wear. These results suggest that characteristics other than shoot density and quality likely explain the traffic tolerance among tall fescue cultivars (Park et al., 2009). Unique characteristics among Kentucky bluegrass cultivars could provide a starting point. Brosnan et al. (2005) evaluated traffic mechanisms between 10 traffic tolerant and 10 traffic intolerant Kentucky bluegrass cultivars. Leaf angle was the single most important factor explaining the difference in traffic tolerance among the genetically diverse genotypes. Plants with a more vertical leaf orientation exhibited greater traffic tolerance than those with a flat, horizontal leaf blade. Brosnan et al. (2005) hypothesized that the vertical leaf reduced the leaf area that was exposed to traffic stresses. 12

27 Other studies indicate that verdure could be an evaluation criterion for intraspecies wear tolerance. Trenholm et al. (2000) observed that seashore paspalum cultivars exhibiting greater shoot biomass and verdure were correlated to increased wear tolerance. Park et al. (2010) reported similar results that Kentucky bluegrass cultivars with less verdure had decreased wear tolerance. Both studies suggest that verdure is a useful characteristic to evaluate traffic tolerance. In response to nitrogen applications, intraspecies wear mechanisms have only been evaluated for perennial ryegrass (Canaway, 1984; Hoffman et al., 2010) and seashore paspalum (Trenholm et al., 2001). Hoffman et al. (2010) observed that shoot growth was the single most important factor negatively correlating to wear tolerance of perennial ryegrass: increasing shoot growth with excessive nitrogen decreased wear tolerance. In this study, cell wall components and shoot density were secondary factors compared to shoot growth and perennial ryegrass verdure did not correlate to wear tolerance. Traffic Intensity and Type The previous sections have discussed how plant characteristics correlate to wear tolerance at the inter and intraspecies level. Although screening for specific plant characteristics assist in improving breeding efforts and allow athletic field managers to search for turfgrass cultivars that exhibit these characteristics, results may be skewed depending on how research is conducted. The following section will address how the variation in wear and traffic protocols may influence how turfgrass cultivars respond to wear stress. 13

28 Researchers have observed conflicting results in the wear tolerance between the same turf-type tall fescue cultivars. Cultivars that performed well at one NTEP did not always perform as well at other locations. During the 2001 Tall Fescue NTEP trials, Justice was evaluated as one of the most traffic tolerant cultivars in Ann Arbor, MI, but ranked in the bottom half of the entries in North Brunswick, NJ. These differences may be caused by the climate, traffic application, fertilization practices, mowing heights, or other cultural practices at the specific locations. Standard protocols for the evaluation of turfgrass traffic tolerance do not exist. The type of traffic machine, timing schedule, and intensity depend on the research facility or NTEP location resources. During the 2006 Tall Fescue NTEP trial in North Brunswick, NJ, researchers applied wear and compaction treatments separately. Each treatment was intensively applied during short time periods and over multiple seasons. Wear treatments in late July 2007 were applied on two consecutive days, with eight passes each day. A modified Sweepster (Rutgers University, North Brunswick, NJ), equipped with rotating rubber paddles, was used to simulate wear (Bonos et al., 2001). Similar to wear treatments, compaction treatments were applied on one day, with ten passes in early August 2007 (Park et. al, 2008). Researchers at East Lansing, MI, applied traffic in a different manner. Evaluators used a differential slip wear machine, the Brinkman Traffic Simulator (Cockerham and Brinkman, 1989). Unlike the modified Sweepster, the Brinkman Traffic Simulator (BTS) produces wear and compaction at the same time. These traffic treatments with the BTS were dispersed throughout the entire year: four passes were applied three days per week. This practice more closely resembles how high school athletic fields are used. Athletic fields receive traffic from practices 14

29 and games several days per week. In the worst cases, fields do not receive any recovery time and they may be used nearly every day for the entire year. Since high school athletic fields consistently receive high levels of traffic throughout the playing season, turfgrass species should be evaluated under these conditions. Minner and Valverde (2005) found that both traffic intensity and periodicity affect turfgrass quality and ground cover. Their study reported that high levels of traffic were required for Kentucky bluegrass plots to show significant ground cover differences from no-traffic plots. Minner and Valverde (2005) also reported that dispersed traffic (all traffic applied 1 d wk -1 ) caused more severe and long-term injury compared to concentrated traffic (traffic split and applied 3 d wk -1 ). The concentrated traffic regime allowed turfgrass to recover between traffic applications compared to the dispersed traffic regime. 15

30 Athletic Field Establishment Practices Selecting an appropriate turfgrass species and cultivar is an important first step to establish and maintain a traffic tolerant athletic field. However, regular maintenance is required on these fields to ensure they maintain turfgrass cover during the playing season. Establishment practices for athletic fields have been identified that influence wear tolerant plant characteristics such as tiller density, verdure, and cell wall components. Both nitrogen fertilization and seeding rates have a significant impact on these characteristics. The following two sections will discuss how nitrogen fertilization and seeding rates influence plant characteristics and turfgrass traffic tolerance in the absence and presence of wear or traffic. Establishment Time Prior to Traffic Evaluation Most research on turfgrass wear tolerance has focused on mature stands of turfgrass (Shearman and Beard, 1975b; Cockerham et al., 1990; Minner and Valverde, 2005b). These stands were given at least 9-12 months to establish. Unfortunately, turfgrass managers establishing athletic fields in the summer are often required to establish or reestablish traffic tolerant athletic fields prior to the fall sport season. Tall fescue has good wear tolerance when the turfgrass stand is mature (Shearman and Beard, 1975b; Youngner, 1961). However, less research has been conducted on the wear tolerance of young tall fescue stands compared to young perennial ryegrass turfgrass stands. 16

31 Recent research has concentrated on evaluating different management techniques to improve turfgrass traffic tolerance in a short period after seeding with 30:70 mixtures of perennial ryegrass and Kentucky bluegrass. Vanini and Rogers (2008) recognized the need to speed athletic field establishment by providing high school turfgrass managers with feasible management techniques. They evaluated multiple mowing regimes and nitrogen treatments during a 70-day period in the summer. Vanini and Rogers (2008) found that a successful fertilizer strategy (product and rate) was more important than the mowing strategy. The results of this study indicate that proper management may help the early traffic tolerance of numerous turfgrass species during summer establishment. Role of Nitrogen in Turfgrass Growth and Traffic Tolerance Of all the plant essential nutrients, nitrogen has the greatest influence on turfgrass establishment (Guertal and Hicks, 2009) and may also impact turfgrass traffic tolerance and wear recovery (Hoffman et al., 2010). Suggested nitrogen fertilization rates vary between turfgrass species and cultivars (Gilbeault and Hanson, 1980; Dudeck et al., 1985). Of the cool-season turfgrasses used on athletic fields, Kentucky bluegrass requires the highest amount of nitrogen fertilization followed by perennial ryegrass and tall fescue (Turgeon, 2011). Although recommended nitrogen fertilization rates exist for non-trafficked turfgrass, the fertilization rates that maximize turfgrass traffic tolerance are influenced by the number of events athletic fields receive (Lawson, 1989). In a high school setting, fields are used most heavily from August until May. When natural turfgrass areas are limited, athletic fields may be used for 17

32 multiple purposes: sport practices, games, and school and community events. Overall, athletic fields typically receive far more traffic during a season compared to home lawns, and turfgrasses used on these fields have been shown to benefit from more nitrogen to overcome turfgrass injury and senescence (Trenholm et al., 2001; Hoffman et al., 2010a). Turf managers would benefit from more specific information on nitrogen s effect on wear tolerance depending on cultivars, use pattern, and season. Impact of Nitrogen on Plant Growth - Nitrogen is the plant nutrient required in the highest amount in turfgrass (Jones, 1980) and impacts plant growth and turfgrass stand characteristics. Moderate increases in nitrogen cause growth flushes in leaf biomass and help plants to recover from injury and senescence (Trenholm et al., 2001). In response to increased nitrogen fertilizer, turfgrass plants favor top-growth over root growth (Canaway, 1984b). Once the root system becomes saturated with nitrate (NO 3 -N), the roots translocate nitrate to the actively growing leaf tissue. Nitrate is reduced to ammoniacal nitrogen, which contributes to the production of simple sugars that are later converted to amino acids (Turgeon, 2011). This process limits the number of non-structural carbohydrates that are translocated to the roots and may limit the ability of the plant to survive during the summer stress period (Turgeon, 2011). These stresses include heat and drought stress. Excessive nitrogen fertilizer has also been shown to result in increased moisture in the leaf tissue (Leyer and Skirde, 1980; Canaway, 1985ab), which results in succulent turf that is susceptible to disease and wear damage (Beard, 1973; Shearman, 1988). Increased nitrogen fertilization promotes an increase in plant tillers per unit area (Leyer and Skirde, 1980; Shildrick, 1981; Canaway, 1984). In response to the nitrogen treatments ranging 18

33 from kg ha -1, Canaway (1984) observed tiller numbers ranged from 26,000-42,000 tillers m -2, respectively. Tillering increased with increasing nitrogen rates. High-tiller counts resulted in tillers that tended to be smaller than those receiving less nitrogen. With high density turfgrass stands however, the differences in tiller density were due to cultivars and it s not clear if high density turfgrass stands resulting from increased nitrogen applications are more or less susceptible to stresses caused by traffic and pests. Nitrogen Applications during Turfgrass Establishment - Turfgrass renovation is considered successful once turfgrass cover approaches 100% (Vanini and Rogers, 2008). Increasing nitrogen fertilization at the time of seeding can speed up establishment of the cool-season turfgrasses, Kentucky bluegrass, perennial ryegrass, and tall fescue (Vanini and Rogers, 2008; Hummel, 1980; Bigelow and Hardebeck, 2004). Rates of 97 kg N ha -1 have shown more rapid establishment compared to rates of 49 kg N ha -1 when establishing Kentucky bluegrass (Hummel, 1980). Tall fescue, although it requires less nitrogen fertilizer than Kentucky bluegrass, also has been reported to establish faster with increasing amounts of nitrogen fertilization (Bigelow and Hardebeck, 2004). During a summer seeding (24 July) of tall fescue in West Lafayette, IN, plots receiving two applications of urea at 49 kg N ha -1, four weeks apart, had less cover two weeks after seeding than using UMaxx (47-0-0) (J.R. Simplot Company, Boise, ID) and UFlexx (46-0-0) (AGROTAIN International LLC, St. Louis, MO) nitrogen treatments of 74 kg N ha -1 ; percent ground cover was 74% vs. 83% and 85%, respectively. Five weeks after seeding, plots receiving a total of 98 kg N ha -1 had greater coverage than plots receiving 74 kg N ha

34 Nitrogen Fertilization and Traffic Tolerance - Nitrogen fertilization during establishment has been reported to speed the establishment period and increase turfgrass density. However, these observations were made on turfgrass that was not being stressed by wear. When athletic fields are subjected to traffic, too much or too little nitrogen fertilization can negatively influence traffic tolerance. The following section will discuss how nitrogen fertilization impacts wear tolerance of cool-season turfgrass under wear stress. Canaway (1984a) evaluated the wear tolerance of nitrogen treatments of 0, 25, 100, 225, 400, and 625 kg ha -1, on a 1-year old stand of perennial ryegrass. The nitrogen applications were broken into 8 equal applications applied at 3-4 week intervals starting in late-march. Before wear, ground cover increased rapidly with increasing levels of nitrogen. However, when wear treatments started, the plots receiving higher levels of nitrogen deteriorated faster than those receiving intermediate levels. In a subsequent trial, Canaway (1985) evaluated the same nitrogen application timings and rates on perennial ryegrass that was seeded in May and only given until September to establish. Their goal was to mimic a typical renovation process that is used on a deteriorated soccer field in the UK. The results were similar to those found by Canaway (1984a): plots that received higher amounts of nitrogen lost ground cover more quickly than those that received intermediate levels. Apparently, optimum nitrogen levels exist since insufficient and excessive nitrogen levels result in the greatest turfgrass deterioration. These two studies concluded that in order to optimize ground cover, 264 kg N ha -1 and 289 kg N ha -1 are required for perennial ryegrass fields given 3 months and 1 year to establish, respectively (Canaway, 1985). 20

35 A review of the research literature reveals that nitrogen has a vital role in increasing the speed to 100% ground cover and improving traffic tolerance for turfgrass stands in perennial ryegrass. However, information is limited on nitrogen rates required for establishing tall fescue high school athletic fields. The recommended nitrogen rates that exist today are for turfgrass species when traffic stress is absent. Turfgrass managers must sometimes establish fields within 2-3 months from late-spring through the summer and then maintain adequate turfgrass coverage throughout the fall season. Effect of Seeding Rate on Turfgrass Morphology and Traffic Tolerance Past research has determined optimum seeding rates for most turfgrass species. These rates maximize seedling survival and promote healthy, mature stands of turf. The suggested rate for Kentucky bluegrass is kg ha -1. The suggested rates for perennial ryegrass and tall fescue are both kg ha -1 (Turgeon, 2011). These rates are the acceptable rates for turfgrass stands that have 9-12 months to establish; however, these rates have not been shown to maximize turfgrass density or speed to 100% ground cover when establishment periods are shorter than 9 months. Seeding Rate Effects on Turfgrass Characteristics Shortly After Seeding - Seeding rates significantly affect turfgrass stand characteristics in the period just after seeding. Researchers have reported that both monostands and mixtures established turfgrass cover more quickly and 21