It is easy to think of soil as just dirt. In fact, soil is a living, dynamic entity that consists of organic material with living organisms and inorganic minerals. Both play an essential role in plant health.
Although the term "organic" is mentioned often in gardening and with different meanings, the definition of "organic" that you learnt in chemistry class applies when you are talking about soil. Organic soil components contain carbon, while inorganic components do not.
Soil contains organic material, both living and dead. Living microorganisms break down compounds, releasing nutrients in a form that plants can use. Soil also contains organic matter, which primarily consists of dead plant material, such as fallen leaves, grass clippings or old plant roots. According to the Iowa State University Extension, organic matter should form 5 per cent of your soil. Organic material helps soil to retain water and nutrients around plant roots where they are needed.
Soil also contains minerals, defined as inorganic because they do not contain carbon. Plants need nutrients for many of their life functions and absorb them from the soil using their roots. Although plants need 13 mineral nutrients, nitrogen, phosphorus and potassium are the most important.