First off I have not grown in soil but have done some reading on the subject so I may not be qualified to comment, but since no one else is commenting I will throw in my limited knowledge.
For most that grow in soil they buy a standard potting soil and amend it from there(adding things like bat guano, bone meal ect.), or they use concentrated organic nutrients to add to water for their feedings.
There is a search function near the top on the right hand side, I would recommend using the search function to search for soil building or another term you are looking to understand. Click the magnifying glass and a new window will open which will search the entire website and return results based on your search criteria.
420, COorganic are members whom I see a lot of posts regarding soil grows, not that they are the only ones but they seem to have a lot of exposure on this site.