Posted: 06/08/2015 at 13:22
I can't agree that a rotovator only stirs up weeds and the top few inches..... Even my little Mantis will go down 8 to 9 inches, admittely I'm not on clay. A professional rotovator will get in deeper than that. One problem can be the formation of 'pan' in the clay below the rotovator dig depth, but I wouldn't think that would be a major problem if the rotovator is only used once.
It would certainly be sensible to remove as much weed growth as possible before using a rotovator, but that's really no different to doing the same if hand digging.