Carbon in the soil - Soil Essentials: Managing Your Farm's Primary Asset - page 21

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Carbon in the soil
Background
Carbon is a chemical element and is written in chemical form as C. Carbon is not
usually found on its own in soil unless as charcoal from burnt animal or vegetable
material, but as carbon-based compounds including carbohydrates and proteins.
These compounds are the building blocks for all forms of life.
Unlike the inorganic chemicals in soil such as calcium, phosphorus, potassium
and so on, carbon 'cycles' in fertile soils depending on the biological actions of
living organisms above, on, and in the soil profile.
Carbon is present in greatest concentration in the upper organic layer, on or
close to the surface of the soil. It is present in decaying plant and animal matter, in
products like humus, and in the gaseous forms of carbon dioxide and sometimes
as methane in soil pore spaces.
Carbon is a vital component of all living things, including plants, animals,
fungi and bacteria, all of which play their part in creating and maintaining a
fertile, healthy living soil .
The carbon cycle
Green plants convert atmospheric carbon dioxide into carbohydrates by the
process of photosynthesis. These carbohydrates in the form of sugars and starches
are formed in the green leaves of plants, and are distributed to all parts of the plant
above and below ground level by sap f low. As the plants mature and die, these