It is quite annoying to spend hours gardening and planting only to wake up the next day to find all your hard work destroyed and Rover lying in freshly dug soil, chomping on a flower bulb. Dogs dig for many reasons: some dig out of natural instinct and others dig to find a cool area to lie down or a means of entering or escaping. Whatever the reason, the problem can be stopped naturally without physical force or dangerous chemicals.
Chili Pepper Powder
Chili pepper is known to be a very effective dog repellent. The capsicum in the pepper is very irritating to the area around the dog's nose and sprinkling this powder on soil in problem areas deters the dog from digging in or entering the area. If the area in question is a large one, the pepper can also be poured into very small sacks made from a material such as pantyhose and the sacks can be thrown around the problem area. Remove the sacks after a rain and before mowing the lawn.
Vinegar and Ammonia
Dogs have very sensitive snouts and don't forget the locations of irritating substances. Placing ammonia soaked cloths or cotton balls in the areas where a dog has been digging will certainly keep him from repeating the behavior. If there is an area of a fence line where a dog is entering, soak some wood chips in ammonia and place them all along the fence line. The wood will hold the scent for quite a while and eventually the dog will associate the fence line with the smell and give up.
Vinegar works the same as the ammonia, however, make sure not to pour it on or close to plants because it can kill them. It is not recommended to use vinegar on a fence line if grass or shrubs are planted there.
Placing a dog's own feces in problem areas may repel humans as well as dogs. This method, while unpleasant, does work well, especially for dogs that have a tendency to dig.