Why Are the Top 4 Inches in Topsoil the Most Important Gift for Life on Earth?
“Everything is connected to everything else. Everything must go somewhere. Nature knows best. There is no such thing as a free lunch. If you don’t put something in the ecology, it’s not there.” Barry Commoner: The Closing Circle, Making Peace with the Planet
No trick question: You have a choice between a box of fertile topsoil and a bag of gold coins. What would you choose? Maybe you’ll change your mind after reading this answer.
First, look at Nature’s Big Picture and see two main facts as clearly as possible:
- Only 4–12 inches (10–30 centimetres) of soil that contains humus is found on the Earth’s upper crust. This thin layer of earth is all that exists to provide nutrition to all plants, animals and human life. It can be said that human destiny is dependent on these 12 inches.
- Humus formation is a biological process of the ecosystem where the energy flow starts with the sun through photosynthesis to help plants make food that is consumed by animals. The last stage is decomposition of organic waste matter in order to release carbon back to the air and convert dead biomass back into mineral nutrients like nitrogen compounds, phosphorus, sulfur, calcium, potassium, and magnesium.
Humus is often associated with beginning leaf litter around trees. Its formation can be called an “organic pre-digestion” for plants; providing a pantry of living nutrients to be absorbed by plants for continued growth with sufficient water and sun.
Amazingly, nature’s infinite organization provides order here, too. The metabolism of dead and living material has its own food cycle web. It starts with microorganisms like bacteria, fungi, protozoa, and nematodes. It is followed by macro-organisms like springtails, mites, millipedes, daddy long legs, woodlice, earthworms, snails and slugs.
There are many irreplaceable functions of good humus.
(Please note it is impossible to duplicate the process with any man-made fertilizers).
- Maintains crumbly soil structure
- Regulates water retention
- Recirculates oxygen and accumulates carbon
- Decomposes organic matter into mineral elements
- Suppresses pests, parasites and diseases
- Controls plant growth
- Recycles nutrients for plant roots, microorganisms, bacteria, fungi and litter-feeding insects (larvae, crickets, ants, termites)
In basic terms, topsoil formation is the movement of living material from the waste material of living things into plants, to return to the living material into Mother Earth.
As living matter, you may well ask how can we manage and protect, not deplete humus?
In fact, according to the UN’s Food and Agriculture Organization, a third of the world’s soil is now moderately to highly degraded.
There are four main reasons why humus may be depleted in our soils:
- Over use of chemical fertilizers which are generally harsh salts that can oxidize living carbon-based matter
- Mechanized rough tillage of soil upsets fragile soil structure
- Failure to protect microbes… misunderstanding their importance. Microbe life can be nurtured by using cover crops and feeding them with fish emulsions
- Failure to build organic matter after using chemical fertilizers. Important to add various crop covers to maintain organic matter in the soil for abundant micro-life and strengthen vigorous roots.
In summary, humus is natural decay when leaves and other plants material are decomposed by soil microorganisms into the most basic chemical elements and nutrients that depend on soil for life, such as plants.
We must never take soil and humus for granted and preserve its creation by life, out of life, for life.
The more you learn about nature’s infinite bio-systems, the more impressed you must be that Nature is a dynamic living system where soil, water and energy; plants, animals and people are part of a complex web of relationships and networks, interconnected and interdependent.
Just think, a box of dirt will at least grow some food … a bag of gold is useless if there is no food.
“Soonday’s smile widened like a rippled puddle. Birchum, you should be proud. You have made a real actual humus garden here. You have a host of bacteria, fungi and protozoa partially eating and softening the leaves so that a crew of mites, sow bugs, silverfish and more insects can continue to digest and release the minerals. Along with water, these nutrients are taken in by your tree’s roots and then carried up to become part of your trunk, branches, twigs, buds and leaves … you are part of this total picture … be proud.” Excerpt from Ecological Succession of Birchum Birch