This is a good question - lots of people wonder about this. When issues come up about a body that's been cremated, it's much different than one that hasn't.
Burying a cremated body, or ashes, is permitted on your own property in PA. If you want a grave marker or headstone, that's another issue according to the PA Cemetery Cremation and Funeral Association. They recommend that you contact your local township or borough office to ask about installing a marker on the property.
A word of caution about burying ashes - what happens if the property is sold or no longer belongs to family? If the ashes are in an impervious container, such as marble, bronze, or copper, they can be disinterred (removed from the ground) and moved to a new location. If they are however, buried loose or in a cardboard or other degradable container, they will be mingled with the surrounding soil and be unrecoverable.
You're wise to be thinking of this ahead of time - good for you.