I have a sheep farm on my survival world and the sheep will be sheared and eat grass to re grow their wool but the grass doesn't turn to dirt. This doesn't happen all time.

How to re create 

1.  Put a bunch of sheep in a 1 by 1 hole and if you automatically sheer with a dispencer they will eat the grass to regrow their wool but won't turn the grass to dirt.

This may take a few tries.