The science behind the beautiful grass on 16 World Cup pitches

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The science behind the beautiful grass on 16 World Cup pitches

The first World Cup kicks off on June 11 at the Estadio Azteca in Mexico City, kicking off a spectacle that will span the summer of three countries and attract a global audience.

As for the grass they will play on, it all started years ago in North Carolina. Or in Colorado. Or in Canada. Any sod farm assigned to grow a specific, important part of the competition.

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Across North America, FIFA’s pitch experts have spent years trying to make 16 new stadiums in three countries feel like a single playing field – inside and outside, in heat and shade, at sea level and altitude, inside pitches that weren’t always made of grass in mind.

Along the way, the playgrounds that will serve as the arena for this summer’s tournament have made an unexpected journey: from research areas to soda farms, from refrigerated trucks to stadium floors, from a live trial to a major soccer exhibition.

The most difficult question may not be answered until it is too late to do anything about it: Can a living field thrive for weeks inside a stadium, under artificial light, in a temporary environment – and hold up when the best football players in the world ask every jump, roll and blade under it to behave?

For the World Cup organizers and their team of turf experts, each venue presented unique challenges.

Several venues normally use artificial turf, and eight stadiums required a temporary natural grass pitch to be installed over, or in place of, the existing artificial turf. Five are covered or covered. Mexico City brings the highs. Vancouver, Seattle and Boston bring cooler, cooler conditions. Miami and Monterrey bring the heat. Houston brings … rodeo to town, presenting its own challenges.

But for players, the ball has to roll the same way, the foot of the plant has to hold the same and the pass has to jump the same way.

Preparation for the field began about five years ago when FIFA partnered with turfgrass experts at the University of Tennessee and Michigan State.

At that time, researchers did not know the full map of the tournament or the exact nature of the challenge. As these areas began to focus, so did the scale of the job, which FIFA described as a multi-million dollar job.

John “Trey” Rogers, a Michigan State professor and turfgrass expert, recalled the success with each new site announcement.

“‘There are three domes. No, there are four. No, there are many,'” he said.

The question was not just which grass would look best to millions of viewers around the world. It was something that could be planted, transported, installed and maintained across North America – and then asked to perform under the pressure of a World Cup.

“It was hard to understand how big it was,” said John Sorochan, a turfgrass scientist in Tennessee.

The project also brought together two turfgrass scientists whose work spans decades.

Rogers helped develop the temporary natural grass field used inside the Pontiac Silverdome during the 1994 World Cup. Sorochan was his student at the time.

Until then, a World Cup match had never been played indoors on natural grass before. “The holy grail has always been: Can you do something inside?” Rogers said. They pulled it off, helping to prove that natural grass can be brought indoors and survive a few World Cup games.

Science has evolved since then. Covered indoor arenas have grow lights, ventilation systems, carefully designed root zones.

“There are many, many tools in the toolbox,” Sorochan said.

For this World Cup, Sorochan said the researchers looked at individual stadiums, then combined them with the challenges they presented: domes, outdoor synthetic-turf conversion, existing grass areas and the height of Mexico City.

All the extra grass can make consistency difficult. So the World Cup sites were narrowed down to two main systems: Bermuda grass for warm climates and a mixture of Kentucky bluegrass and perennial ryegrass for cooler ones.

“If you add another grass,” Sorochan said, “that adds another variable.”

Together, the stadiums cover a total of 88 square miles of natural turf.

The fields were planted with plastic.

In a normal field, the roots grow into the soil and are cut when the sod is harvested and transported to the field. But the variety of venues available at World Cup stadiums requires a different approach.

Growing with plastic changes root behavior. The roots grow down, hit the plastic barrier and turn to the sides, forming a dense mat.

That allows the sod to be harvested with most of its root system intact. Once the sod is moved to the field and placed in the sand, the roots start to grow down again.

The World Cup stadiums started at one of nine soy farms: six in the United States, two in Canada and one in Mexico.

Some grasses are sown about a year before installation. Rogers said a field of Kentucky bluegrass/perennial ryegrass planted in plastic can be ready in nine to 11 months.

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“Now we can cut it like a pizza and roll it up,” Sorochan said.

A typical sod plot is 3½ feet wide and 30 to 45 feet long. Rolls are loaded onto refrigerated trucks, similar to grocery store produce.

“It takes a lot of trucks,” Sorochan said.

The grass then went on a long journey.

The finals moved from the Carolina Green Turf Farm in North Carolina to the Meadowlands in New Jersey. Grass from Colorado is now in Atlanta, Dallas and Houston. In Mexico, soybeans grown north of Monterrey faced a 10-hour journey to Guadalajara.

Time is important because the material is alive. Extreme heat, weight or time can stress the sod before it reaches the field.

When the sod arrives, the workers don’t just roll out the green carpet.

In some places, artificial grass was coming out and the field was built on cement. In others, the existing area was protected, covered and layered: drainage, geotextile fabric, sand, irrigation and reinforced sod.

The advantage of plastic-grown soybeans is that they arrive mature and stable, not as fragile new planting material. Rogers said fans may be surprised at how quickly it can be installed and used.

“You’d be surprised how many National Football League games you’ve watched on Thursday and a game on Saturday or Sunday,” he said.

He likens the installation process to a delicious meal that moves from the ingredients to the kitchen.

“Finally, we’ll pass it on to the chefs,” he said, “and then we’ll go.”

For the turfgrass scientist, the magic is underground.

FIFA’s detailed specifications call for 100 percent natural grass, which is usually grown in a sand-based root zone designed for drainage and stability. The grass is reinforced – either with woven synthetic fibers or a hybrid backing – to handle cutting, sliding and running at an elite level.

For permanent systems, that would mean 12 inches of sand over a 6-inch drainage layer. In temporary systems, the profile is very shallow, usually with 6 to 10 inches of sand and a plastic drainage module underneath. Some systems also include vacuum and ventilation components that remove excess moisture and move air through the profile.

Grass is the visible part. A field is a subsystem.

In controlled areas, landscapers should change the sun.

That means turn up the lights – sometimes a lot of them. Some stadiums can light up the entire stadium at once. Others may need to light one part, move the equipment, and then light the other. In Dallas, the lighting system is suspended from the ceiling and lowered near the stadium.

Lights don’t just keep the grass green. They help the plant produce energy, recover from aging and handle weeks of World Cup traffic.

In Tennessee, Sorochan’s team used a soccer ball launcher, high-speed cameras and video analysis to study how the ball behaves when hit. In one experiment, he said, the researchers shot balls into the grass at 55 kilometers per hour and at a 17-degree angle, and measured that the bounce remained low enough for the player to control it – well, not higher than the knees.

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Long passes should hit high and rise predictably. It shouldn’t jump over the player’s control in one city and skate differently in another.

The goal, says Sorochan, is simple: “We don’t want the overhead to jeopardize the gameplay.”

When the games start, most of the fans will watch the players.

Rogers will watch the ball roll.

In American football, he said, a ball that hits the ground usually means the game is dead. In soccer, the field is part of every game. The pitch is in every pass, every touch, every cut, every slide. Throughout the tournament — on the same pitches on 16 different pitches — Rogers hopes his pitches are so good that no one feels the need to talk about them.

“Silence is gold to me,” said Rogers.