A closer look at organic matter

Organic matter is a soil's most important component. It increases moisture retention, contributes to chemical and biological properties, and improves its physical qualities.

It consists of three parts:

  • 10-15% easily decomposable organic matter, made of living and dead organisms,
  • 40-45% moderately decomposable organic matter, half-life 20-40 years and is protected in soil clods and clay particles, and
  • 40-45% very stable organic matter, also called humus, and it is very old, about 1000 years.

How organic matter forms is a question that has intrigued Dr. Ines Fritz from the Institute for Environmental Biotechnology at the University of Natural Resources and Life Sciences in Vienna. Her video Building humus shows organic matter being made over 365 days. Beginning with rocks and stones, Dr. Fritz introduces soil micro flora and fauna, eventually becoming capable of sustaining plants.

Watching the microscopic organisms in the video reminded me of something that Edward Russell wrote in The Fertility of the Soil, published in 1913. At the time he was the Director of the Rothamsted Experiment Station and he reflected:

"We shall find the study of the soil very unsatisfying and uninspiring if we become too much absorbed in its utilitarian aspects and forget to stop and reflect on the infinite wonder of its honeycombed structure and its dark recesses, inhabited by a teeming population so near to us and yet so hopelessly beyond our ken that we can only form the dimmest picture of what the inhabitants are like and how they live."

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