Don't know about the soap--------but from what the guy told me, and it seems reasonable-----the smell of the corn is what causes the deer to be attracted at the front end.  I would assume there is some learning curve also after they get a taste of it----------so, maybe if the smell can be distorted, such as with garlic, this hot stuff you got, etc etc. then it might cut down on the damage..........but it all will have to wear off eventually.  Maybe by that time they'll move to Sam's down the rode!  :<)