Ninety percent of the remaining dry material is made up of carbon, oxygen, hydrogen and nitrogen. Sulfur, phosphorus, potassium and calcium are the other important components. In fact, some of the very stable materials in the organic matter complex can remain in the soil for hundreds or thousands of years. These decompose rapidly and provide nutrients in excess of microbial needs. Residue from grain, grass and cotton are low in nitrogen but high in carbon and thus take longer to decompose.
Most soil microbes obtain the energy necessary to grow from carbon in the soil organic matter.
Since nitrogen is an essential for cellular components, micro organisms must obtain nitrogen from organic matter, other microbes or from the air. When organic materials with high carbon concentrations relative to nitrogen concentrations are added to the soil, soil microbes use most of the available nitrogen in the soil, thus creating deficiency conditions for higher plants. This is called nitrate depression, sometimes referred to as the 'priming effect,' which will persist until activity of the soil micro organisms decreases due to a lack of carbon. Hence, it is often necessary to add supplemental nitrogen fertilizer when carbon-rich organic materials are added to the soil. You are the 1476th person to access this page.