Tips on clearing brush and roots from field leaving top soin pretty much in place?

If the brush isn't too, too thick, it usually works well to bushhog everything low to the ground, then run through with a root rake on your dozer (See here (http://dozerrakes.com/), for example), then bushhog again to cut off anything left sticking up out of the ground. If you want it really smooth after that, I think a skid-steer-mounted power rake would finish it off nicely.

If you're trying to get rid of every last stump and stem sticking out of the ground (for example, to put horses on it right away without having to wait a season for things to rot away), you may need to do something more rigorous. The forums at TractorByNet.com | Compact Tractors | John Deere, Kubota, New Holland (http://www.tractorbynet.com) offer a wealth of information on this subject matter.