How virgin? My 5' disc will basically just roll over heavy sod. I always have to run through it with a 1-bottom plow I have to loosen it up initially. After that the disc will work okay as long as I put enough weight on it.
I think if you just run over it with a disc it will still be "never turned or tilled". :lol:
That is just my opinion. Like I said, I can pull my disc behind my tractor over a grass field next to my garden, and it basically chews the grass up. It definitely doesn't prepare it for any type of planting.