Oregon State's Elaine Ingham has been studying microbes for years. What follows is a summary of her findings. The web beneath the soil is amazingly complex, but it is possible to understand important principles without soil science training. Plants' Roots Put simply, plants consist of roots and shoots. The shoots obtain energy from the sun and the roots obtain nutrients and water from the soil.
Roots help shoots grow and vice versa.
Dead plant shoots and roots therefore make it possible for living plants to get inorganic nitrogen. Plant roots also get nitrogen from mycorrhizae, a type of fungus that lives on plant roots such as corn, peas, apples, and citrus, and feeds these plant roots nitrogen and phosphorous in return for energy. Mycorrhizae can be very long, so plants with these fungi get nutrients that the roots could never reach. Micro-organisms in the Food Web Bacteria consume the easily digested materials such as grass while the fungi consume the harder to digest woody materials. Prairies and lawns, therefore, have mainly bacterial decomposers, while forests have saprophytic fungi.