We have a lot of land, only cut about 3 acres, so I just trained my dog to relieve himself in the tall grass that doesn't get cut.

Many people train their dog to use the same spot as a toilet, it doesn't take much, just some supervision and persuasion and a few "good boy's" when done correctly, by that I mean for you to take your dog outside, watch him sniff around, if he's about to go where you don't want give him a firn no and walk him to where you do want him to go, keep him there until he does his business, after several times of doing this, he will know that this spot is his toilet and will go there automatically.
If you want, designate a small corner of your yard as his toilet, put a couple of boards as an edge and fill inside with round 3/4" gravel don't use crushed gravel, it hurts their pads and they won't like going on it.