l own a 1/2 mile race track and l have been asked to turn it into dirt . l would like to leave the asphalt and just add clay over it . My concern is when l wet it for racingwill l be able to control moisture . Has this been done before????

Yes Fulton Speedway in NY has done it and they have one of the best surfaces on the East Coast. You should look up New Egypt Speedway in NJ and seek out the advice of their prep crew. Another good idea is go to Motorsports 09 in Atlantic City NJ in January as they will have a Promoter is Summit seminar for people that own and or run race tracks.

would not it be easier to add dirt on top of it?

This has been done at several tracks. The one most have heard of is Bristol. Back in 200 they put dirt over the pavement to run a WoO show. Contact them for more info on how to do it. Another track that did it was I-70 in MO.

You should talk with Bruce Richards,he owns and operates Albany-Saratoga speedway which is dirt over black top. CVRA web site

As others have said it is been done successfully. l just wanted to add that l applaud you for considering changing from asphalt to dirt. It will be a lot more work to prep the track (obviously), but you will have a much better show for your fans.
The next time l want to take an expensive nap with complete strangers l will pay to go to a race at a paved track.

Just rip the asphalt up and put dirt down.

Dirt is for Racing and Asphalt is for Gettin There!!!