A flat expanse of green grass stretched under the evening sky in Moses Lake, in central Washington state, on the first night harvesting sod for the World Cup stadium in Seattle.
A crew of teens and young adults gathered alongside more seasoned workers at Desert Green Turf farm, one of several across the country growing grass for the tournament. Long strips of sod almost 4 feet wide had already been cut. A tractor revved up and slowly moved forward, dragging three tubes behind. Several people followed, curling the strips around the tubes into fat spirals of dirt and grass.
When the grass gets rolled up, it can start to decompose under anaerobic conditions created by heat and weight. To prevent that, they harvested through the night, taking advantage of the cooler temperatures. It was then shipped in refrigerated trucks to Seattle and rolled out over infrastructure — aluminum, gravel, sand, and a system to control water — built on top of the stadium’s artificial turf.
That night marked the beginning of the end after researchers spent years developing the grass for this World Cup. FIFA said it invested more than $5 million into the effort. The goal is for each pitch across the United States, Mexico and Canada to feel the same to play on. And that matters because players say the field affects them — and the ball.
Usually, professional soccer games in the U.S. are played on either natural or artificial grass. But for this tournament, FIFA commissioned a special type of pitch made up of both.
These fields are almost all natural grass, which is often preferred by players. But they also have a small amount of synthetic blades to help withstand the foot traffic of the games.
“Everything you look at is grass, but just below the canopy there's about 5% composition of those synthetic fibers that help stabilize — or act as rebar — for the sand root zone to make it so you don't get big blowouts or big divots,” said John Sorochan, a professor of turfgrass science at the University of Tennessee who was part of the research team working on the grass for FIFA.
Even as the grass gets worn the field should stay even, he said, which makes it safer and more playable.
Pitch play
“The first thing I do is go to the field, to the pitch, and just look at the playing surface, just so I know what to expect,” said Gabrielle Carle, a defender with the Washington Spirit, a professional team out of D.C.
Carle looks at how long the grass is and scans for bald spots, divots and dry patches. She grew up playing on artificial turf, but as she has gotten older, she said, natural grass has become her “gold standard.” Switching between softer grass and harder turf can take a toll.
“Physically for the body, sometimes just that adjustment back and forth can be a bit tough,” she said.
Kenny Cooper, a retired Major League Soccer player who now works for FC Dallas, said on artificial turf the ball “can maybe just keep bouncing” while on a natural field “there might be a little bit more give, and the ball might just generally stay in play more.”
Cooper actually liked the traction he got from artificial turf. But that can also grab cleats and lead to injuries, such as twisting a knee during a sharp turn.
“Cutting, changing direction — I think it can be safer to be on grass,” he said. “Falling to a surface, I think the grass with the soil can be a lot softer than turf and whatever’s under the turf."
Those concerns were echoed by Lu Barnes, a former defender for the Seattle Reign who is a soccer ambassador with the local World Cup committee.
“Playing on turf is a lot harder on your knees, ankles, and joints, so the impact of that is just not as natural,” she said.
A few years ago, Barnes played on a hybrid field in Sweden, which she said was able to stand up to harsh weather. And she said it felt good: “You would never be able to tell. It definitely felt like natural grass.”
In the field
There are different methods to create hybrid pitches.
In one, a big sewing machine stitches artificial grass into the natural field. Giant needles stick fibers into the root zone — as was the case for the grass that went to Seattle. Alternatively, farmers seed natural grass onto a carpet with artificial blades. Grass then grows above the carpet and the roots stretch below.
One of the owners of Desert Green Turf, Kurtis Cox, paced the field under a beating sun the day after the harvest began, taking moisture measurements to ensure the watering that day was accurate.
“You can't even tell that the artificial’s down there now,” he said, bending to examine a carpet field destined for the World Cup stadium in Los Angeles. “If you get down and start pulling on these, every so often, you'll get on a piece that won't rip, and that's the artificial pieces that are in there.”
These fields required more exacting work than what Cox was used to. The sod was grown on huge sheets of plastic, which forced the roots to grow sideways and mat together. That preserves the root system so that once the grass is installed, it can be played on sooner than if it had to recover from the shock of its roots being cut during harvest. The farm team also graded the fields so they were level. And they used a big machine to clean debris out from between the blades.
“This is not something sod farmers typically do,” said Trey Rogers, a professor of turfgrass research at Michigan State University, another member of the team hired by FIFA to work on the World Cup grass.
Touching grass
A major challenge was the scope of the tournament. The research team had to figure out how to get fields to thrive in a huge range of climates and conditions for games in the U.S., Mexico and Canada
“I mean, 16 stadiums across three countries, half of the stadiums don't have natural grass in them, ever, and five of those eight stadiums are domed,” Rogers said, referring to venues with roofs that block out sun.
Rogers and his team identified which species would grow well in each climate. They used a mix of Kentucky bluegrass and perennial ryegrass for cooler areas and bermudagrass for warmer ones.
From there, they conducted experiments to establish growing and maintenance practices for the farms and stadiums, which included measuring the grass, monitoring moisture, watering, and getting the grass light in shady stadiums.
Testing for the grass included ball bounce and surface resistance.
As part of that, researchers used a machine with a disembodied soccer cleat attached to it to “simulate a soccer cleat hitting the surface and measure what the traction is, the displacement, and the forces that the athlete's feeling,” said Sorochan, who helped develop the device.
Much of this comes down to predictability, Rogers said: “If they can't predict how the ball is going to bounce or how it's going to roll or how smooth it's going to be — now we've got a problem.”
Problems did seem to crop up last year, when FIFA installed temporary fields for a club tournament in the U.S. For instance, one coach criticized the pitch as dry and bouncy; another player said the ball didn’t bounce enough. FIFA wouldn’t address those specific comments, but spokesperson Adam Geigerman said last year's games were a “dress rehearsal” for this World Cup, where the fields will have custom infrastructure and more time to be installed.
FIFA’s requirements include a sand-based root zone that drains well but still retains some moisture and nutrients for the plant, Sorochan said, along with ventilation and vacuum systems.
Irrigation systems will wet the surface of the grass before the match and at halftime for the “playability of the game.”
“It's not for the grass itself, it's for where the ball interacts with the grass,” Sorochan said.
What's ahead
This work has caught the attention of others in the field of turfgrass research. Ambika Chandra, a professor of turfgrass genetics and breeding at Texas A&M University, is not involved with the World Cup, but has been watching their progress over the past few years.
“All those elements that have gone into it to ensure that these surfaces are consistent and uniform, regardless of their environment that they will be in, that just amazes me,” she said.
The emphasis on the pitch for this World Cup may change how people think about the game, Chandra said, leading to more focus on how surfaces impact athletes and their performance. "I'm hoping that this will eventually trickle down to all those levels of sports, in different types of sports."
After the tournament ends in July and many people have turned away from the pitch, Chandra will be among those watching to see if more hybrid fields come to the U.S.
