Reposition your camera to face your salt lick. Try and get him to see you are "replacing" the salt lick and hopefully he will get caught on camera. I would then approach him in an adult manner and ask that he remain on his own property and that he shouldnt be trespassing. If he plays dumb let it be, you know he will cross the line again and get caught on camera again. Once that happens, immediately inform law enforcement about someone trespassing on your property and have them come out and speak with him.