Dirt consists of much more than mere minerals. That's why the most important parts of the plants we grow may be the underground root systems we rarely see. .

A soil profile such as this offers rarely seen information about how itstexture and content can become stratified and vareid.

The addition of microbes and fungi does more than provide nutrients for the plants, explains David Perkins, a San Francisco-based farm and garden consultant. It actually modifies the structure of the soil itself.

For serious gardeners and growers, Perkins adds, understanding soil biology offers myriad benefits.