Minerals & Soils

• Testing the soil can reveal mineral deficiencies that must be corrected for proper plant growth. Andrew Dernie/Photodisc/Getty Images

  Soil is a complex combination of minerals, organic matter and living microorganisms. It's not known how all the pieces fit together, but the interactions among the three provide the nutrients and proper conditions for plants to grow. Some soil, such as that primarily from limestone, has a poor mix of minerals. According to the University of California at Santa Barbara, the debris resulting from volcano eruptions has many necessary minerals that easily break down into usable compounds and rich, productive soil.

Feldspar

• Feldspar is the most common mineral in the Earth's crust, according to the Encyclopædia Britannica. Its weathering provides the basic components for soil. Feldspar contains additional minerals such as sodium, potassium, calcium and iron within its structure. As it breaks up it releases these into the soil.

Silicon and Aluminum

• The silicon from feldspar makes up 27 percent of the soil, with aluminum following at 8.1 percent and iron at 5 percent, according to microbiologyprocedure.com. Heavy rainfall, such as happens in the tropics, can easily leach away the aluminum, leaving a dense clay soil. Aluminum can also release toxic ions which turn the soil acid. Organic matter binds these ions into an inert form.

Trace Minerals

• Calcium, magnesium, potassium, phosphorus and sulfur are also present in soils. These are important to healthy plant growth, but are often bound up in chemical compounds. It is the work of soil microorganisms to digest the compounds and release the minerals in a form that plants can absorb. Adding these microorganisms may be necessary to bring the soil to optimum growing conditions.