I once had a food plot that had an area that was not too sandy or too much clay. Just regular looking brown soil in the middle of a plot. I could not get weeds to grow there, ryegrass would not even grow in that spot as I tried it out of curiosity. I even spread some topsoil out of a bag over it and got germination that only lasted a few days then died. All I can guess was this spot was once under a machine that was dripping when they were clearcutting. I used T&M on this plot though with success everywhere, but there.