FEATURESTORY
by Judith Fitzpatrick, Ph.D.
T
The Importance of
Soil Organic Matter
wo hundred years ago the soil contained 3000 gigatons of carbon,
now half the carbon in the soil has been released into the atmosphere
as carbon dioxide. Why is this important? It is a contributing factor in
the earth’s loss of 60% of its soil. The current 1500 Gt of carbon in the
soil is double the 750 Gt of carbon in the atmosphere as carbon dioxide.
To understand how the carbon in the soil was lost we need to understand the carbon in
the soil. The carbon in the soil is stored as soil organic matter (SOM). SOM is actually the
remains of dead microbes. It contains all the mineral nutrients needed by plants and is
carbon rich. The plants don’t need carbon, they get their carbon from the carbon dioxide
in the air, but the plants need the minerals in the SOM and they get those minerals from
the microbes that feast on the SOM. The SOM is the inheritance, as the microbes feed on
it, they deplete it and they feed the plant. The inheritance is supposed to be repaid when
the plant dies and the microbes digest the dead plant and then die and become SOM. In a
grazing system similar to the world as it was 2000 years ago, an animal eats the plant and
the animal feces and dead bodies are returned to the system. Now some of the corn being
harvested is sent from Iowa to other places around the nation or world and the inheri-
tance is not repaid; the microbes disappear as their food disappears; and the plant is not
being fed.
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www.GardenandGreenhouse.net
June 2018