Geoff Bennett:

As the FIFA World Cup approaches this summer, a key question: What does it take to create the perfect pitch, or field, for soccer's biggest stage?

Amna Nawaz:

Our correspondent Paul Solman put his body on the line to find out.

Paul Solman:

A soccer ball fired at an unarmed reporter to introduce a global mega-event close to home starting in June, Canada, Mexico and the U.S....

Announcer:

It's Lionel Messi.

Paul Solman:

... hosting the FIFA Men's World Cup.

John Sorochan:

The single biggest sporting event there is. The last Men's World Cup final, 20 percent of the world's population tuned in to the final.

Paul Solman:

So there better be no screw-ups.

University of Tennessee turf grass guru John Sorochan has been tasked with ensuring the playing surfaces at this summer's 16 North American venues are pitch-perfect.

What are the stakes here?

John Sorochan:

It's on the world's biggest stage. You don't want the field to come into play where the ball's going to bounce wrong or hit something that it compromises or jeopardizes the outcome of the game or heaven forbid a player gets hurt from it.

Paul Solman:

A divot in the natural grass that might cost a team its star, its country, a national depression. So, the goal:

John Sorochan:

How do we make these surfaces consistent and uniform, knowing that Miami's at sea level and is what we call warm season grass, Bermuda grass, to inside a dome in Vancouver, which would be a cool season grass?

Paul Solman:

Not greener grass, then, just tried, true and unvarying, which has taken years of research.

To test it, Sorochan's team invented a so-called flex machine.

John Sorochan:

What it does is, it simulates an athlete's foot striking the surface. So how does it work? So you basically have a 3-D-printed foot inside there. You see the foot's retracting so we can measure the speed as it's lowering down, and you can see that's an acceleration condition of a 168-pound athlete.

Paul Solman:

The machine minutely measures how the pitch and player interact.

John Sorochan:

What the body's going to feel and what the compliance of the surface is. How much is that surface giving away, what loads is it putting back on the athlete?

Paul Solman:

The perfect pitch must also have the perfect bounce.

John Sorochan:

From two meters, the ball has to bounce and come back up between 0.6 and one meter.

Paul Solman:

Hence, the ball blasts.

John Sorochan:

You can see this soccer ball goes through.

Paul Solman:

Then -- whoa.

John Sorochan:

And it hits. And we measure that ball hitting the surface, the speed it comes in, the angle, and then the angle and the velocity it comes out at. And we can come up with a coefficient of restitution to get consistency and uniformity of all the surfaces.

Paul Solman:

Now, World Cup games are played on natural grass. But half the host arenas have artificial turf.

John Sorochan:

So those eight stadiums have to get converted temporarily to natural grass. And of those eight stadiums, five of them are indoors, so dome stadiums that -- no sunlight. And grass needs sunlight to grow.

Paul Solman:

To make sure it does, different lights for different sites.

John Sorochan:

So this is the grass that's going to be used in all the five dome stadiums. And it's been in here for 15 weeks. And so right now, we're in here, and we have got the normal lights on. So it's -- quote, unquote -- "nighttime." So, at 3:00 p.m., the lights come on. So the sun comes up.

And then this is the light that grows the grass.

Paul Solman:

Oh, wow.

John Sorochan:

We have mostly red light because it's going to be using less electricity. So it's more energy-efficient.

Paul Solman:

As for the grass itself?

John Sorochan:

So what they do is they grow the sod over impermeable plastic layer. So it's being grown on a -- outside, over top of plastic. And you roll it off with the plastic and deliver it to the stadium.

Paul Solman:

The grass is installed over a layer of sand and reinforced with plastic fibers.

John Sorochan:

And it basically acts like rebar to stabilize that surface. And you see these are spaced 20 millimeters apart, a little less than one inch.

Paul Solman:

Sorochan's team ran almost 200 experiments to prepare for the World Cup. But even the perfect bounce was way too much for me.

For the "PBS News Hour," Paul Solman in Knoxville, Tennessee.

Geoff Bennett:

We got a full education there. That was a great story.

(Laughter)