I bet the Ag farm he was talking about is the WVU land I have heard about. I believe it is in the area of Keedysville but I don't know for certain. The Frederick City watershed has lots of public land that should keep you busy for a while. You can get there by driving through Gambrill State Park and continuing until you enter the watershed. The other entrance is through the community of Mountaindale just off Rt 15N.
Good Luck...