Wooden fence posts take abuse from rain, snow, hail and the sun. All of the effects from the elements can gradually deteriorate wood, causing rotting. According to Old and Sold, the leading factor in post decay is decomposing sap inside of the wood. When exposed to water, decomposition hastens the rot of the wood post. To protect your post from decomposing and rotting, it is important to treat both the post above ground and the wood post below ground. The post at ground level and below comes into the most contact with water and is the most susceptible to rot.
Remove the wood fence post from the ground. If your fence posts are set in cement, dig under the cement to form a pocket beneath the bottom of the wood post.