How can I train my dog to use one area of the yead as his bathroom area? He is on a 50' dog run and manages to use every inch of that area as his bathroom. My last dog would only use one area of the yard. How can I train this dog to do the same?

One thing that I have been meaning to try myself that a friend does is to make a designated potty area.

Just buy some garden edging from a gardening store and make a little box out of it on the lawn.
Leave a gap for him to walk through.

You then go through the potty training process again but keep him on leash and take him into the box.
Eventually move onto offleash but stand next to the box.

Always remember to praise good behaviour :)