My one horse that I owned preferred to roll in a sandy soil pit that I made for him. The second you turned him out, he would jog over and drop and roll in his rolling pit, as I called it.
How true, as soon as I brush my horses, they go and roll in a dirty area. They seem to all like the dirt to roll in.
my horses love to roll right after they get groomed all my hard work gone mine like grass and the dirt
Of course horses will pick dirt to roll in over anything else; it makes the most work for us humans. ;)