Eating Dirt

My 11 year old male lab/shephard mix has recently started digging holes and eating the dirt. Is there something wrong or is he just being a dog? He eats dry food only and occasional table food.

You dog is officially Senior, so have him checked at the vet for a vitamin or mineral deficiency that may be causing the dirt-eating.
   
Check for any other condition that causes sudden dirt-eating.
   
Give him vitamins, if you aren't already doing this (I like Pet Tabs)
   
If he's healthy, then he's just being a dog. Actually, dogs can be pretty disgusting, they do all kinds of awful stuff for fun (roll in dead things...)
   
You can decide how much to prevent him from doing this if it turns out that he's just doing stuff.