probably turf or grass
The Stadium has natural grass.
Grass
Turf
its turf
No, it is not. The new Yankee Stadium, like the old stadium, is natural grass.
FieldTurf
artificial turf
Yes, it is.
The playing surface at Ralph Wilson Stadium is Astroplay (field turf).
Yankee Stadium
Grass turf is natural grass. Astro turf is artificial and is a surface of synthetic fibers made to look like natural grass.