Clanad, I don't think you can get medicinal sulphur in the Uk, easier just to get worm tablets.Does he always eat it from the same place? In that case, it may be tht it tastes good! There is one place in the New Forest near us where our dogs have always enjoyed eating the soil and we have seen other dogs doing it too. If its in your garden, have you used cocoa by products ? They are sold as a n alternative to peat and also as soil improver, dogs like to eat it but it is poisonous to them. The other thing i ave seen my dogs want to eat is soil treated with fertilisers containing seaweed, or blood, bone and fish meal. Don't let your dog eat soil treated with any of these.