An overview of the latest traffic tolerance and other pertinent information on commercially available and experimental cultivars of the four main species used on athletic fields: Kentucky bluegrass, perennial ryegrass, tall fescue and bermudagrass.

NTEP traffic testing results

At any one time, the National Turfgrass Evaluation Program (NTEP) is evaluating more than 600 cultivars and experimental selection in nationwide tests. Data collected and summarized from these trials can be found on our website, Our data is also published on a CD, in exactly the same format as the NTEP website, which can be purchased. 

NTEP collects data on overall turfgrass quality, appearance characteristics like color and texture, disease and cold tolerance and many other traits. In recent years, however, NTEP has focused more on testing specific performance traits, such as traffic tolerance and saline irrigation performance. This article provides insight on NTEP testing and an update on improved cultivars of the most commonly used species for athletic fields. 



2010 cultivar update

The following is an overview of the latest traffic tolerance and other pertinent information on commercially available and experimental cultivars of the four main species used on athletic fields – Kentucky bluegrass, perennial ryegrass, tall fescue and bermudagrass.

Kentucky bluegrass                                                

This year we have data from the fifth and final year of the 2005 Kentucky Bluegrass Test. Since bluegrasses may take several years to develop significant levels of thatch and disease, the fourth and particularly the fifth year of a bluegrass trial can yield interesting results. We have witnessed this phenomenon with 2010 data, as disease, drought and heat have taken their toll on these grasses. Therefore, 2010 data is very useful for understanding how these grasses withstand these stresses. We advise that you investigate closely this fifth year of data, which is available on the NTEP web site, as well as the 5-year final summary report, which will be available later this year.                 

For those field managers that irrigate with salty water, salinity tolerance evaluations are now in the fifth year at the Las Cruces, NM site. The site irrigates the 2005 NTEP Kentucky bluegrass trial with saline water (Sodium Adsportion Ratio (SAR) =2.06 in 2010). In previous years, this moderately low saline level did not produce large cultivar separation. In 2010 however, much great entry separation was noted with ‘Hampton’ leading the way. Other entries in the top statistical group include, ‘Gladstone’, ‘Barrister’ and ‘Emblem’, and five other entries.

Traffic tolerance was evaluated at three locations in 2010, using different types of traffic simulators. The North Brunswick, NJ location (Rutgers University) applied traffic in May 2010, nine months after the last traffic ‘season’, using the “Slapper,” which causes leaf abrasions but not soil compaction. The entries that rated 6.0 or higher (scale is 1-9; 9=best) after the May simulation include ‘Greenteam’, ‘BAR VV 0709′, ‘Bariris’, ‘BAR VV 9630’, ‘Sombrero’, ‘Emblem’ and ‘Julia’. Canopy fullness, expressed as a percentage, was evaluated after the initial 36 passes of wear on May 6th. All of the above entries plus ‘CPP 822’ and ‘Barduke’ had the highest canopy fullness ratings (51.7 to 71.7%). 

Compaction was applied to the Rutgers trial on May 6, and percent ground cover was rated 8, 22 and 49 days after the compaction and wear treatments. ‘Greenteam’ had the highest canopy fullness ratings eight days after traffic, with ‘BAR VV 0709’ having the highest canopy fullness ratings 22 and 49 days after treatment.

Traffic tolerance was also evaluated at East Lansing, MI in 2010. Michigan saw much damage from the traffic, applied in fall 2009 and again in late summer 2010, using the Brinkman simulator, which compacts the soil as well as causing plant shearing. Cultivar separation as shown in overall turf quality ratings was not that large, with just over one-half of the entries performing statistically equivalent to the top entry, ‘BAR VV 0709’. However, as in the Rutgers trial, ‘BAR VV 0709’ exhibited outstanding traffic tolerance by finishing with the highest percent ground cover in five of seven rating dates. Entries also showing high percent cover ratings on one or more dates include ‘Skye’, ‘Washington’ and ‘Washington II’.

The Madison, WI location used a pull-behind cart of water-filled drums with golf cart tires to impose traffic stress. This led to excellent cultivars differences, led by ‘SW AG 514’, ‘Harmonie’, ‘Sombrero’, ‘Greenteam’ and ‘Dynamo’. Interestingly, most of the traffic tolerant grasses were also the best performers where no traffic was applied.

Poa annua is a weed problem in Kentucky bluegrass, particularly on athletic turf. Cultivars that can withstand Poa annua are valued by sports turf managers, golf course superintendents and lawn care operators in northern states. After 5 years, plots are often damaged or thinned such that Poa annua can invade. In 2010, two trial locations were able to rate percentage Poa annua invasion. In both Amherst, MA and Madison, WI, the range of ratings was quite large, from 0.3 – 33.3% Poa annua (LSD=15.9) at Amherst and from 2.3 – 81.7% Poa annua  (LSD=23.8) in Madison. ‘CPP 822’ and ‘Washington II’ had the least Poa annua in Amherst and ‘Harmonie’ had the smallest percentage of Poa annua in Madison.

Tall fescue                            

This is the fourth year of data collected on the current NTEP tall fescue trial. This is a large trial with 113 entries established in 2006. Year one data typically reflects establishment rate, year two data usually reflects broader cultivar performance, while years three and four often allows us to determine if trends seen in year two are still viable.

Tolerance to stresses, such as traffic, shade, drought and saline irrigation, are being evaluated by NTEP in this tall fescue trial. Intensive traffic is applied, suing the “Slapper” on the tall fescue trial at North Brunswick, NJ. Wear and compaction were applied in July, with turf quality and percent canopy fullness rated multiple times. When considering the final turf quality rating, many of the top performing entries from last year finished in the top statistical group in 2010, 83 days after traffic was applied. ‘LS 1200′ finished with the highest quality score at the 83 day mark with sixteen other entries in the top statistical group. Entries such as ‘Traverse’, ‘Bullseye’, ‘Faith’, ‘RK 5′, and ‘Cannavaro’ were again in the top turf quality statistical group 83 days after traffic, however, only ‘LS 1200’ and ‘Falcon V’ completely recovered their canopy fullness by 83 days after traffic to pre-traffic fullness levels. 

Data from 2010, unlike the past 2 years, exhibited larger performance differences in tall fescue entries for salinity tolerance at the Las Cruces, NM location. In particular, where potable vs. saline irrigation (SAR=5.41) were compared, there was 1) more cultivar separation when using saline irrigation, and 2) cultivar performance varied under the two irrigation regimes. For instance, of the top twelve entries for turf quality under saline irrigation, only three (‘LS 1010’, ‘Gazelle II’ and ‘Xtremegreen’) were in the top twelve when using potable water. The top entry in the saline irrigation trial, ‘Justice’, ranked significantly lower under potable irrigation, although it was not statistically significant. And one entry, ‘Sidewinder’ had the second lowest turf quality score under potable irrigation but finished in the top dozen entries under saline irrigation. 
As tall fescue use increases in the northern tier states, so do problems such as Poa annua. Our trial in Puyallup, WA has evaluated Poa annua invasion for the last several years, and has documented the increasing percentage of Poa annua. In 2009, poa invasion, evaluated in September, varied in entries from a low of 15% for ‘3rd Millenium SRP’ to 73.3% for ‘Ky-31′. In 2010, the Puyallup site rated Poa annua four times and the percentage overall increased from last year. ‘3rd Millenium SRP’ again performed well, with some of the lowest overall Poa annua invasion scores (46.7 – 60.0%). ‘Essential’, ‘Shenandoah Elite’ and ‘LS 1200’ each had the lowest percentage of Poa annua on one rating date, while ‘Catalyst’, ‘SR 8650’ and ‘Hemi’ tied ‘Shenandoah Elite’ and ‘Essential’ for low percentage (43.3) on one date. The percentage of Poa annua in northern tier trials is most likely a reflection of density differences, damage from cool weather diseases, and possibly winter injury. A reduction in growth during cooler temperatures may also play a part in Poa annua invasion.

Perennial ryegrass                          

Perennial ryegrasses are a mainstay in many athletic field situations, because of positive attributes such as fast germination, better establishment under low and high temperatures and traffic tolerance. Our latest perennial ryegrass trial was planted in fall 2010, and new data is not yet available. Therefore, we must consider the four years of data compiled and summarized from our 2004 trial of perennial ryegrass. The 2005-2009 data show many new grasses with improved quality compared to the top performers in the previous NTEP trial, ‘Mach I’ and ‘Pizzazz’.

Grey leaf spot is a potentially devastating disease of perennial ryegrass that can destroy entire turf stands in a short period of time. Several locations submitted data on grey leaf spot during the testing period. Statistically significant performance differences were observed with some of the top performers being ‘Fiesta 4’(9.0 rating, scale is 1-9; 9=no disease), and ‘Exacta II GLSR’, ‘Soprano’, ‘SR 4600’, ‘Dasher 3’, ‘Defender’ and ‘Allstar 3’ (all having an 8.9 rating).

Traffic tolerance of the perennial ryegrass entries was evaluated at several locations over the four year test period. In the final summary, very few differences were noted at the Ithaca, NY and East Lansing, MI traffic sites. The Mead, NE trial (using a Brinkman) finished with a large group of entries in the top statistical group, led by ‘Chivalry’. The Puyallup, WA location, also using a Brinkman unit, showed the largest cultivar separation in turf quality averaged over the four years, with eleven entries in the top group, led by ‘Uno’, Derby Xtreme’ and ‘Zoom’. Overall wear tolerance ratings, averaged over the Amherst, MA and North Brunswick, NJ sites, have ‘Keystone 2’ in the top spot. However, about 50 entries performed statistically equal to ‘Keystone 2’.


Our latest bermuda trial, established in 2007, contains 25 seeded entries and six vegetative entries. Many of these entries are experimental cultivars or new commercial cultivars. NTEP evaluates warm-season grasses by comparing seeded and vegetative entries, and also by separately comparing seeded vs. seeded and vegetative vs. vegetative.       

The Fayetteville, AR location applied traffic in summer and fall but fewer statistical differences were observed than at that the Raleigh, NC location. The Raleigh, NC trial evaluated wear tolerance in seven rating dates through August and September. ‘Latitude 36’ was at the tops for wear tolerance ratings at six of the seven rating dates, with each rating finishing well within the top statistical grouping. The only other entries to finish in the top statistical group for each rating date were ‘North Bridge’, ‘Premier’ and ‘Tifway’. 

Entries were tested for the third consecutive year under the saline irrigation treatment (SAR=5.41) imposed at Las Cruces, NM. ‘Tifway’, the highest turf quality performer in 2008 and 2009, was the highest scoring entry again in 2010 with the vegetative entries ‘Latitude 36’ and ‘North Bridge’ being statistically equal to ‘Tifway’ for turfgrass quality. The seeded entries ‘Princess 77′, ‘SWI-1113′, ‘SWI-1122’and ‘PSG 9Y2OK’ also performed statistically equivalent to ‘Tifway’. Additional testing on salt and traffic tolerance should be reviewed before making purchasing decisions based on these traits.                                                         

Kevin Morris is executive director of the National Turfgrass Evaluation Program (NTEP), Beltsville, MD,


Traffic simulation    

For any turf evaluation, applying a stress uniformly is necessary to obtain consistent, and thus accurate data. Consistent application is particularly important for traffic data, since research efforts on in-use athletic fields almost never produce consistent results. In addition, there are many different types of ‘traffic’, i.e. damage caused by golf spikes or cart use is different from damage caused by a soccer goalie, or a large-bodied football lineman. 

“Traffic” can be separated by its various factors, as described by Dr. James Beard in his seminal textbook, Turfgrass Science and Culture. Beard writes the following about turfgrass wear: “Direct pressure on the turf tends to crush the leaves, stems and crowns of the plant. Damage is greatly accentuated by the scuffing and tearing action frequently associated with traffic.” Beard also discusses another aspect of traffic, compaction: “The mechanical pressure applied by human and vehicular traffic results in varying degrees of soil compaction.” Compaction results in restricted air and water movement through the soil profile. Both wear and compaction require evaluating to determine effective cultivars and strategies to minimize traffic damage.

Since necessity is the mother of invention, the turf research community has developed equipment to simulate wear, traffic and/or compaction on trial areas at universities. Each machine simulates somewhat different aspects of traffic stress. A particular NTEP species trial may therefore, receive different traffic damage at different locations. 

The most popular traffic simulator in the US is the “Brinkman,” developed at UC-Riverside. The Brinkman is pulled by a small tractor and consists of two rollers that are fitted with cleat-like spikes. The rollers can be filled with water to add compaction stress and can be set to travel at different speeds from each other, thus enabling a ripping and tearing action in the turf. Two passes with the Brinkman have been correlated to approximate the number of cleat marks created during one NFL game between the hash marks at the 40-yard line. The Brinkman offers a relatively quick and easy method to apply traffic stress. However, the Brinkman design has been criticized because, 1) the tractor pulling the apparatus causes additional compaction and damage and has to be disregarded when evaluating plot damage, and 2) the Brinkman does not produce the compressive force needed to adequately replicate an athlete’s force and pressure at the playing surface.

To compensate for the Brinkman deficiencies, Michigan State University developed the “Cady” traffic simulator. The Cady is a modified Jacobsen Aero King 30 aerator (a self-propelled unit) that has had the steel aerating tines removed and replaced with cleat-fitted pieces of rubber tires (to simulate a cleated foot). Since the aerator consists of four shafts connected to a cam that delivers a vertical action, the Cady features more vertical downward pressure than the Brinkman. A Ryan GA-30 aerator has also been used in modifications to produce a Cady simulator.

Other simulators have been developed that either offer variations on the Brinkman and Cady, or simulate other traffic such as golf cart wear. The Europeans have long used the Differential Slip (DS2) machine, which is a cleated walk-behind unit. Also being used in Europe is the SISIS unit, as well as a unit developed by the Sports Turf Research Institute in England to simulate damage from tennis players at Wimbledon. The University of Georgia modified a Brouwer T224 ride-on roller by adding cleats to the roller drums.  Iowa State and Ohio State have each modified and used a Brouwer roller simulator as well. Scuffing units, which consist of a brush on a frame that is dragged across the plots, are being used in some locations, simulating the scuffing damage that occurs on a golf course putting green. 

A new machine, recently developed by Rutgers University and nicknamed the “Slapper,” modifies a Toro Sweepster unit by replacing the wire brush with rubber “fingers,” or paddles from a potato harvester. The Slapper bruises and damages leaf tissue (simulating wear only), therefore a roller must be used along with the Slapper to provide compaction stress. Each of these units, and others that have been developed, play a different role in simulating and evaluating traffic tolerance.  

Testing procedures

NTEP trials are established at university locations and evaluated for 4-5 years. Species such as Kentucky bluegrass, perennial ryegrass and bermudagrass have been tested by NTEP for more than 25 years. Each new trial includes recently developed cultivars, experimental entries that may become commercialized, and well-known standard cultivars. With each trial, NTEP and an industry advisory committee develops testing protocols and important characteristics to be evaluated. Trials are established at locations that are important use areas for that species, or where a disease, insect or other problem is prevalent, such that NTEP can adequately evaluate the test entries for that problem. Also, NTEP establishes tests where particular stresses can be evaluated, i.e. a location that can impose simulated traffic, saline irrigation or consistent drought stress. 

Evaluation procedures are developed for each of the traits, in some cases these procedures are very detailed. For instance, when testing traffic tolerance, we must consider the species being tested, its typical use patterns, the region of the country, the traffic simulation equipment available and other factors. Only then can NTEP decide how and when to impose simulated traffic and the best data collection procedures and timing for that trial.