Carbon in the soil - Soil Essentials: Managing Your Farm's Primary Asset - page 23

Interpretation of the soil tests
The soil test for carbon will give an indication of the biological activity in the soil
at a point in time, and is only indirectly related to the needs of plants growing in
that soil. However, this does not mean it is not important and, in fact, it is probably
the most important figure in the whole soil report.
Soil carbon levels relate directly to the biological health of the soil, which in
turn relates directly to how well plants can grow in the soil. Soil pore spaces can be
considered as 'houses' for soil microbiology, which in turn is the most vital part of
the living web of life on the planet. Soil microbiology is part of a whole series of
complex, integrated steps, from small simple life forms, to larger more complicated
forms, and ultimately to the largest, most demanding life forms on the planet.
Without these microscopic life forms in the soil, life as we know it on planet Earth
would be impossible.
Managing soil carbon
As already stated, soil carbon levels are directly related to soil microbiology, so to
modify soil carbon levels we need to modify soil microbiology and carbon is best
added to soil in conjunction with living plants.
Soil can be considered as a living entity in its own right.
Basically, soil microbiology has the same requirements as plants: food,
water, warmth, air (oxygen) and shelter. For soil microbiology, food can be
supplied in the form of decaying plant and animal matter and exudates from
living plants, plus essential nutrient elements. These nutrient elements may be
supplied in decaying plant and animal matter, in the inorganic components of
the soil or added to address any deficiencies present.
Water supplies need to be consistent, ideally not too dry and not too wet. Soil
temperature is important, and the microbiology is most comfortable at
temperatures we would find comfortable. As the microbiology is made up of living
organisms, a consistent oxygen supply is essential. This is normally supplied by
maintaining good open structure in the soil. Shelter for soil microbiology is also
provided by the pore spaces in the soil, and to a lesser extent by plant cover on top
of the soil. Plant cover has a modifying effect on the soil, keeping temperature and
moisture levels more even, which encourages microbial growth.