Not likely due to the soil...
If the holes are round, it could be a fruit borer, a type of caterpillar. If the holes are ragged, it could be insects or animals, several possibilities. You could use Dipel Dust or Thuricide, same peoduct under diff. brand names. It's a bacterial insecticide and is non-toxic to anything but caterpillars. Is there any way you could show pics?
