The Role of Microorganisms in Soil
Plant life, our basic food supply, is dependent upon the trillions and trillions of microbes that exist in the soil, degrading organic matter, recycling nitrogen and carbon, and producing new soil in forms plants can use directly. Thus, good soil, far from being dead, should be described as "living soil," because of its content of living microorganisms. In fact, the rhizosphere, the area surrounding the roots of most plants, contains a wide variety of microorganisms that help the plant to absorb minerals and other plant nutrients. Some plants, such as legumes, have nodules on their roots that contain nitrogen-fixing bacteria, which take nitrogen from the air and produce nitrogen compounds the plants use in the synthesis of amino acids and protein; these are an important protein source in the human diet.