Why do dogs lick soil, the floor, the ground, etc?

Previously it was suspected that dogs suffered from a mineral deficiency if they licked the ground or other things. Now it is known that this is not the case. There are several reasons why a dog may overzealously lick things. Some do it for the flavour, but some do when they have digestive problems. In these cases the dog will have other symptoms such as a poor appetite, vomiting or loose stools. Dogs can also suffer from obsessive compulsive disorders which can result in excessive licking.