In Decks and porches, Wood contact with soil or ground that happened on posts mostly, considered as a Defect. The proper way would be locating the same post on a metal piece and concrete for wood protection.
Recommendation, if posts are in contact with soil or ground and are in good condition, you can clean the area that is in contact with soil and use some wood preservatives to increase its service life. Besides, make sure woods are pressure-treated ones (for outdoor). Otherwise, it should be replaced by a new one.