Turf & Rec

Features Agronomy
Little margin for error when managing NFL fields


December 6, 2012
By Mike Jiggens


Topics

Managing a National Football League franchise’s field is arguably the
highest pinnacle a sports turf manager could ever hope to achieve, but
when demands for pristine conditions are made every day, there is
little margin for error.

Thomas Serensits, manager at the Center for Sports Surface Research at Pennsylvania State University, spoke to the Sports Turf Association in September of the challenges he faced during his three years as assistant groundskeeper for the NFL’s Philadelphia Eagles during the early part of the millennium.fieldweb

Upon his graduation from Penn State in 2001, Serensits was hired by the Eagles organization for their grounds crew at the club’s training camp facilities at Lehigh University in Bethlehem, Pa. The position led to his promotion to assistant groundskeeper shortly afterwards.

The year of his inaugural camp was hot and dry. Most of the turf on the fields at Lehigh is poa annua and none is irrigated, prompting the use of water wheels “which makes it difficult to schedule because you have two practices a day. They like to practise early in the morning and later in the afternoon.”

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The water wheels, he said, had a tendency to get stuck, requiring him to go in at 2 or 3 a.m. to ensure they could be moved.

The facilities didn’t boast the best of conditions, Serensits said, noting the wear was intense when players were on the fields twice a day during extremely hot weather.

“They pounded those fields.”

Overseeding was attempted in an effort to restore as much turf on the fields as possible. Disease pressures were triggered by the season’s drought, and the fields’ bowl-like setting caused humidity “to just hang there. We had a lot of pythium blight.”

Spraying was done regularly with some success, but there was still some turf kill in spots, he said.
“It was a baptism of fire for me. Just being out of school, we learned about these diseases in class, but, when you actually live them, you learn a lot more about how to control them and see the real world situation.”

Once training camp had finished, the job took him to the Eagles’ practice facility at the NovaCare Training Complex in Philadelphia. The $37-million complex, which is also home to the football team’s front office, was a state-of-the-art practice facility when built in 2001. The quality of its grounds was a significant upgrade from that at Lehigh University.

The site of a former navy hospital, the NovaCare facility features three full-sized practice fields. The uncrowned fields have sand-based root zones consisting of 85 per cent sand and 15 per cent soil.

“The reason it was made flat was so the fields could be rotated,” Serensits said.

If one area incurred heavy wear, the field could be rotated simply by painting new fields and trying to spread out the wear. Because of the abundance of sand, the uncrowned fields were not considered a drainage concern.

In addition to the practice fields, the NovaCare facility included an experimental field where trials could be conducted in anticipation of the opening of Lincoln Financial Field, the new home of the Eagles. Primarily, the football club wanted to test a system of removable trays. A similar system had been tried at Giants Stadium, but with less than satisfactory results.

Serensits said the Eagles’ system was a little different. It was a grass tile system with only two inches of root zone which was reinforced with shredded carpet atop a small drainage pad on porous asphalt.

“The idea behind putting that carpet in there was to try to make more of a divot-resistant surface.”

The removable trays measured seven feet by seven feet with the idea being that if a middle section of the field became worn, it could be removed for a newer piece to ensure the turf would always be in the best condition possible.

“It created certain management challenges because you had only two inches of root zone. You couldn’t aerify as deep as you typically would. You didn’t want to pull cores and use hollow tines because you’d be pulling all that shredded carpet out.”

Such limitations meant using solid tines and going in shallower to prevent reaching the asphalt layer. Because of the shallow root zone, the field wasn’t equipped with an irrigation system, prompting the use of water wheels. The shallow root zone, however, tended to dry out quickly and required two passes of the water wheel down each side of the hash marks. In the heat of summer, watering was done every couple of days.

Serensits said there were ultimately too many management challenges to adopt the removable tray system at Lincoln Financial Field. Additionally, when attempts were made to change the pieces, the tiles tended to fall apart. Although the idea was abandoned for the new stadium, it remains in place at NovaCare Complex.
When Serensits initially joined the Eagles’ grounds crew, the team was still playing its home games at Veterans Stadium, but, because it was city-run, he had few responsibilities there. The quality of its turf was substandard, he said.

“The turf was perennially bad. It always seemed to be voted the worst playing field in the NFL. Teams didn’t like to come there because the field was so bad.”

The Eagles hold the distinction of being the only NFL team to have ever had a home game cancelled due to poor turf conditions when a pre-season contest against the Baltimore Ravens at Veterans Stadium was called off several years ago.

The Eagles shared Veterans Stadium with Major League Baseball’s Philadelphia Phillies which often led to a number of issues on the field. Serensits said the Eagles-Ravens game took place the day after a Phillies game, requiring the second-base cutout area to be amended for football. Framed by wood, the cutout area is normally filled with clay and tamped in place to make it playable for football. The night before the Phillies game, however, it had rained and, after packing the clay, it dried out overnight, shrunk and produced a lip at the wood frame. Concerned about the potential for injury, game officials cancelled the game.

Serensits said the solution to prevent any further occurrences was to put in temporary asphalt into the cutouts each time the field was converted from baseball to football. This required removing the dirt from the skinned area and replacing it with asphalt.

“When it came time to convert it back for the Phillies, they had to jackhammer all that asphalt out and put the dirt back in.”

The labour-intensive process was fairly short-lived as the new Lincoln Financial Field drew closer to its August 2003 opening. The $512-million stadium was built exclusively for football, concerts and other events. The Phillies moved into a new ballpark of their own.

Construction at Lincoln got underway in 2001. In September of 2002, work began on the stadium’s sub-grade, and drainage went in later in the month. A six-zone irrigation system was installed in early October, drainage gravel went in a week later, and a sub-surface heating system was established to heat the root zone and keep turf growing as work progressed later into the year. In total, 28 miles of pipe were installed beneath the field to keep it heated. The pipe was positioned a sufficient depth below the surface to prevent it from being compromised during aerification. The system covers six different zones which can be regulated separately.

“It is turned off several days before a game to try to harden up the field. If you left that on, it would make the field too soft and not be very playable and cause divoting.”

Contrary to what some may believe, the heating system is not meant to melt snow on the playing surface, Serensits said.

The root zone was put in place in November at a composition of 85 per cent sand and 15 per cent soil at a depth of 10 inches. The silica sand was supplied by a quarry in New Jersey. Laser grading began later in the month.

The 100 per cent Kentucky bluegrass sod was also obtained from New Jersey at a farm which supplies several other NFL franchises. The medium-thickness sod was laid in on Nov. 26. Left to sit all winter, it effectively rooted in the spring and was being regularly maintained by the end of April 2003.

A DD GrassMaster system was adopted for the field. Used on several European soccer fields and by both the Denver Broncos and Green Bay Packers, the system provides an artificial root zone to help increase surface stability.

“As you start to lose turf coverage throughout the season, you have these fibres in the field that help create a more stable surface.”

The nylon fibres are vertically sewn a depth of seven inches into the root zone, spaced three-quarters of an inch apart. Serensits said “a big sewing machine” is used to sew in a total of 22 million fibres throughout the field, making it about three per cent artificial. Two sewing machines worked 24 hours a day for two weeks to complete the field.

“It’s almost a security blanket for your turf. As you start to lose turf, you know you’re still going to have pretty good footing because you have this system.”

Serensits noted, however, there are some disadvantages to the system as well as advantages. Although it increases stability and reduces divoting, cores cannot be pulled. For a sand-based field, there is a need to remove organic matter, but the GrassMaster system requires more vertical mowing to prevent pulling up any of the artificial fibres.

Resodding also can’t be done in season.

“You can’t just come out there and cut out the centre of the field and put new sod down because you’d be cutting all your GrassMaster fibres out.”

Over time, the nylon fibres have a tendency to lay over and they can be buried through excessive topdressing.

In recent years, bermudagrass has been introduced into the field, making Lincoln Financial Field the NFL’s northernmost bermudagrass playing surface.

“It’s really the optimum athletic field grass if you have enough warmth to grow it. It spreads so quickly with rhizomes and stolons. It’s quick to recover itself.”

The problem with bermudagrass is that it goes dormant once temperatures become colder, even though some newer varieties are more cold tolerant. The Kentucky bluegrass field had struggled during the heat of summer, so it was recently decided that bermudagrass would form the playing surface for the first half of the season until colder weather set in and then the field would be sodded over with Kentucky bluegrass for the season’s second half.

Bermudagrass will quickly recover, but shuts down when it gets cold. Grassing from one type to another cannot be achieved by simply cutting out the bermudagrass and replacing it with Kentucky bluegrass. The GrassMaster system blocks such a strategy, forcing the sodding over with Kentucky bluegrass once colder weather sets in.

Once the season has concluded, the Kentucky bluegrass cover will be “ground out” so that resprigging with bermudagrass can be done in the spring.

During the period of Kentucky bluegrass cover, the field is mowed at 11/4 inches while the height is adjusted to just under an inch with bermudagrass.

Before the Eagles ever took to the field for their first home game in the new stadium, an elite soccer game between Manchester United and Barcelona was played, giving the grounds crew a chance to change up mowing patterns and do a lot less field painting.

A Bruce Springsteen concert was also held at the stadium prior to the Eagles’ first home game. With three concerts performed over the course of four days, the field experienced some turf kill in spots.

Serensits said the field was verticut to get rid of as much as the dead grass as possible,  and then the grounds crew “seeded the heck out of it” with perennial ryegrass to have conditions ready for the Eagles’ first pre-season home game.

Temple University also plays its home games at Lincoln Financial Field.

Serensits used the second half of his presentation to suggest practices his audience could adopt to better manage high-use fields.

Mowing frequency is often an issue at the municipal level. Some sports turf managers can only afford to send an operator out once a week. Although Lincoln Financial Field is mowed a minimum of three times a week for the Eagles, he acknowledged that level of frequency may not be possible when budgets are tight, but suggested if a field is mowed only once, perhaps an effort can be made to cut twice a week, and if another is cut twice, maybe three times can be the aim.

“The more times you mow, the better turf quality you’re going to get. You’re really going to notice a difference in density and overall quality. You don’t want to be mowing once a week where you’re going to be getting clumps of grass lying on the surface.”

Mow at the proper height and stick with it, Serensits recommended. Sometimes it’s suggested that during the summer a field be left to grow longer and then the mowing height can be lowered in the fall in time for football season.

“We don’t tend to recommend that. When you do that, the grass is used to being mowed at a certain height and then when you drop the height, that’s a stress on the grass right before you’re going to have a whole lot more stress on the grass.”

He advised consistency with mowing heights, preferably between two and three inches, but added lower heights can be achieved if the field is irrigated.

Blades should be kept sharp at all times to ensure a clean cut which will help the grass blades heal themselves and reduce the chance of any pathogens getting into the cut.

Nitrogen is needed for a field to recover from damage, but Serensits recommended a soil test be conducted first to get a better understanding of nutrient and pH levels. A fertility program can then be tailored accordingly.

“What we recommend for high-use fields in Pennsylvania is a minimum of found pounds of nitrogen per 1,000 square feet per year.”

He admitted many may find that to be a large amount, but it’s required for the field to recover from heavy damage as well as to get new grass up and growing.

Overseeding is a key necessity to help build up the seed bank within the soil, Serensits said.

“You want to have that seed there, ready to pop open and germinate once the turf gets ripped out. Build up your seed bank before you get to a situation where you get thinning turf.”

He suggested a good strategy is to “manage the field within the field,” meaning that whatever is done to the centre of a field doesn’t necessarily have to happen to the outside areas.

“If the centre is your main problem area, use all your seed there if you need to, or the vast majority of your seed. You don’t need to treat the entire field the same way.”

The more times a sports turf manager can overseed, the better, Serensits said, with the goal being to get as much seed down as possible.

If a field is grown to Kentucky bluegrass, it should be overseeded with perennial ryegrass, especially in season, he suggested. Kentucky bluegrass takes too long to germinate and, even once it does, it tends to just sit there. Perennial ryegrass will germinate in five or six days and will mature that much more quickly. If time allows, however, Kentucky bluegrass overseeding can take place in the spring as long as there are no events scheduled for the field until fall.

Sand-based fields, although superior for drainage and porosity, don’t necessarily perform better than native soil fields, Serensits said. Sand-based fields tend to be preferred because they are less prone to an unexpected disaster such as monsoon-like weather which can render a soil field unplayable.
“On a sand-based field, you’re not going to have that disaster.”

Native soil fields provide better footing in many cases and are less divot-prone because of the cohesion between the soil particles.

Aerifying sand-based fields is a different undertaking than it is on soil fields. On sand-based fields, it is important to remove organic matter because it can clog up the system and drainage won’t be as effective. When aerifying, the cores should be removed and the surface topdressed with sand in an effort to dilute the organic matter. Aerifying native soils is done to relieve compaction, to get more air into the system and to reduce surface hardness.

Hollow times are more effective on native soil fields, allowing for soil removal and soil bulk density reduction. Drainage and surface hardness issues are both addressed.

When there can’t be as much surface destruction, solid tines will work well, helping to increase oxygen levels and infiltration. They’re not as effective in relieving compaction because no soil is being removed.

Another option is deep tining, but soil moisture levels must be taken into account.

“You want the soil to be almost too dry to get the machine in there. At that point, when it goes down in there and it kicks out, it’s going to shatter the soil and create cracks in the soil, and that’s where you’re going to get your biggest benefit from a deep tine machine.”

If deep tining is done when the soil is too wet, it’s simply going to move the soil around and won’t produce the desired cracking.

The fate of pulled cores is dependent on the type of field, Serensits said. For sand-based fields, the cores should be removed entirely so as not to reintroduce organic matter into the soil. On native soils, cores can be dragged back in unless sand topdressing is to be done.

The more organic matter present in a native soil field, the better, he said. Soil bulk density is reduced and cation exchange is increased. When soils are tested, organic matter should also be analyzed, Serensits said. Three per cent is OK, four per cent is good and five per cent is excellent.

If a native soil field’s organic matter is low, it can be built up by topdressing with compost, he said. If weeds can be controlled first, a quarter-inch of compost can be spread onto the field. Core aerating will help mix the compost into the native soil when using the closest spacing possible. Once everything is dragged back, it represents an ideal time to seed and fertilize, he added.