like i said, I had a friend that said an old timer made bows like that,, so it has been done,, I think if you took off the sap wood, it would work better, I am just spit balling,, but it would act as a sealent to resist bugs and checking I think,,
I think leavingn the bark and sapwood,, will slow the process to much to be practical,, but with out the sap wood,, it might keep the bugs and checking at bay,, i have never tried this,, so am just speculating,,but am making a bow from a fence post,, so know it will hold up to being in the ground ,,,the guy I knew was from east Texas so the stave may have been buried in sandy soil,, aslo in TExas it was common for the old farm houses to be on osage pier and beam,, cause it did not rot, and the termites wouldnt eat it,,i actually owned a house builit like that,,
put a moisture meter on it before and after,, so you know how its working,, or worth the effort