I would not recommend burying the skull for two of the reasons mentioned here. One is, he skull could be dragged off, the second it takes a long time ( it may have to be burried for a year or longer). Another reason against burial, is the leach out the calcium in the bone. At the same time minerals like iron (give the bone a rusty coloration) will soak into the bone and can discolor it permanently. If you want a nice white skull, I would suggest maceration or beetles. Stay away from simmering/boiling the skull, as this also removes calcium out of the bone and can make the skull brittle. Best to take it to an experienced taxidermist who knows what he/she is doing. Ask them prior on how they clean their skulls though. You don't want to end up with someone just throwing your skull in a pot and cooking it.