RE: This is what gets me
I've an idea.......seems to me you would own a tractor or something that you use to cut your field, right? Leave it on the runway when you're not there!!
I'm not sure.........but it seems to me, if I was using your runway for touch and goes I'd think twice about doing so........heck, I wouldn't want to ruin my plane landing and hitting your "OBSTRUCTION"
Seriously though....I would just park something on the field that will keep someone from landing there. It's private after all. Hope I helped in some way. Good Luck