Nuances Of World Cup Turfgrass

As part of a multimillion-dollar research project funded by FIFA, the researchers studied grass species to identify the highest performers and developed customized seed blends for sod farmers based on World Cup host cities’ temperature. The grasses had to reach a certain height too, to meet FIFA specifications.

The researchers explored how to grow grass in indoor stadiums that lack plant-sustaining sunlight, collecting data in a shade structure FIFA constructed at the University of Tennessee to replicate conditions of a domed stadium.

They investigated the best ways to lay natural pitches over artificial turf, a conversion required at eight World Cup stadiums, including Lumen Field in Seattle. And they tested how soccer cleats interact with natural grass using a machine with a 3D-printed foot and ankle fitted with a cleat to mimic a player’s movements.

“Behind the scenes, there’s a lot of technology that's going into getting grass to perform at this level,” Sorochan said in an interview. His research concentrates on optimizing turfgrass performance for sports fields, golf courses and other high-traffic areas.

Alan Ferguson, FIFA’s senior pitch management manager, first approached Sorochan in 2019 with an ambitious proposal. For the first time, Ferguson wanted scientists to help develop, through evidence-based research, the perfect pitch for a tournament watched by a fifth of the world, by some estimates.

“Besides my jaw dropping on the floor and having to pick it up, I was excited,” Sorochan said.

Once Sorochan signed on, he immediately asked Rogers, his mentor while a student at Michigan State University in the 1990s, to be a co-principal investigator. Both recruited their own undergraduate and graduate students, plus research assistants and technicians, for the large-scale project.

Rogers is known for helping develop a system that makes temporary fields portable. For the 1994 World Cup, he and Sorochan worked together to install a temporary indoor grass field at Michigan’s Pontiac Silverdome.

The fields beneath the 2026 World Cup players’ cleats are far more than a simple layer of grass. (Grass aficionados, take note: Players at stadiums in warmer host cities such as Miami and Kansas City will race around on Kentucky bluegrass with a little perennial ryegrass mixed in, while cooler locales like Boston get bermudagrass alone.) The grass is mixed with plastic green fibers for extra stability and firmness.

That’s not the only place plastic shows up. The scientists grew the sod on plastic fiber “carpets” that allow the roots to spread laterally and intertwine, remaining intact. That way, when the sod is moved, the roots can reestablish themselves quickly.

The sod-on-plastic gets placed atop a sandy zone for the turfgrass root system, and beneath that is a drainage layer with gravel. Then there’s a vacuum and ventilation layer that removes extra water and ensures airflow. The whole system can be driven from sod farms to stadiums hundreds or even thousands of miles away.

“We can pack it, roll it up tight, put it in a refrigerated truck and it’s gone,” Rogers said in an interview. The rolls measure up to 40 feet by 3.5 feet, with 10 to 15 of them fitting in each truck, and the system arrives “ready to play on,” he said.

Sorochan has also built a reputation as a turfgrass innovator. Several years ago, Sorochan and UT research scientist Kyley Dickson invented the Flex (short for “foot lower extremity”). It’s the portable machine that pairs motion sensors with a mechanical foot and ankle attached to a cleat to mimic the movements of a 170-pound player’s foot striking natural grass. Software developed at the university collects and interprets the sensor data.

In other tests of turfgrass surfaces for the 2026 World Cup, the researchers used a machine that drops a ball from 6 feet.

Most World Cup players, spectators or members of the media won’t leave a game talking about the pitch, and that’s more than OK with Sorochan. If a pitch is the focus, it means it didn’t perform the way it should have.

“If it did what it was expected to do, people are gonna talk about the game,” he said. Rogers, of course, is one of the exceptions. He’ll definitely be talking about the grass.