If you have trouble finding out who owns the land go to your county offices and check with the county recorder. Ask for a plat map of the area--you'll have to know pretty exactly what area you're interested in. The plat map will have the private property boundaries and the office folks can tell you who owns which piece.
Then just call and ask permission. I've called several local landowners and always been told "have a ball!" Fact is, a couple of them encouraged me to ride their land to help spread fertilizer!