LindaB220 - you must've been the chickeneer I was referring to on this thread about putting mothballs inside pantyhose to hang around the coop. Glad I brought up the subject again to get your expertise on the snake subject! My DD's city property butts up against a little wildlife preserve and unfortunately she gets deer, skunks, oppossums, hawks, coyotes, rabbits, rats, raccoons, bobcats, once a bear and once a mountain lion (cougar) and many rattlesnakes every year. Because of her big loopy kooky Pitbull mix she can't set up any mothballs around her fence - the dog is just too dang curious. I bet the ammonia treatment would work at the perimeter dirt base of her iron bars fencing in the backyard because the dog would probably be repelled by the smell.
How often do you do the ammonia treatment and how does it affect the chickens who forage in the treated areas? Rattlesnakes are plentiful during Spring and hot weather and seem to disappear to hibernate in the Winter. So I imagine treatments would only be in Spring and Summer months - but how often?