Humus: its Chemical, Physical and Biological properties that are essential for life

by Glenn David Morris

Because of its complex and dynamic nature, humus is one of the least understood living forms on earth.  Despite this, the fact remains that there is probably no other living matrix on the planet that offers as much hope for reversing global warming, restoring abundant water cycling and delivering maximum health benefits to all life. We can achieve extraordinary things if we restore a solid, soil humus foundation in our landscapes.

My research on the subject of humus over the past twenty years has given me some appreciation of the way humus forms and the immense value it has to the project of restoring healthy landscapes and ecosystem processes.

This article offers a small insight into the subject of humus and its importance as we navigate away from a degraded environment and planet towards a fully regenerated earth. It is informed by the research of world-leading chemists, biologists and soil scientists like Selman Waksman, Alexander Humbolt, Kevin Handreck, Rainer Maier and others.

While always trying to gain a better understanding of humus and its properties, we should keep in mind that respect and a ‘reverence for life’ is of far greater importance to our future than thinking we can ever fully analyse all the processes of nature.(1)

Description of Humus

Firstly, humus is an amorphous body, meaning it has no defined form, though it sometimes takes a spherical shape (2).  Another way to put this is to say that every formation of humus is unique to its specific local site and that humus occurs in an infinite number of forms.

This image was found at the website of the  International Humic Consortium for Carbon Sequestration   http://ihccs.org/humic4.htm

This image was found at the website of the International Humic Consortium for Carbon Sequestration http://ihccs.org/humic4.htm

Humus occurs not in a definite solid or liquid state but is often described as having a plasma or gel–like consistency. (3) Organic and inorganic colloidal particles are fixed apart in a gel-like matrix, a formation sometimes referred to as floccules of humus.

Humus is also described as a macro-molecule. The components of organic residues that have been broken down in the soil cluster to form a residual chain framework, like a mesh fence, for the gel-like materials to bond to. Carboxyl group compounds like quinines and phenolic acids attach to each other, amino acids and other compounds. This process leads  to the formation of the humus macro-molecule.(4)

Humus is also sometimes referred to as a ‘living milieu’ in which the breakdown products from organic matter like lignin (45%) combine with living root exudates and other microbial compounds like glomalin, which derive from Mycorrhizal fungi and bacterial glues.(5)

As well as storing vast amounts of carbon, humus also contains large amounts of nitrogen, largely in the form of true protein and amino acids. (6) As Stevenson (1989) states, “Proteinacous substances are attached to the central core of the humus molecule.” (7)

Raina M. Maier (2009) refers to the initiation of humus formation as a two-stage process:

In the first stage there is the “formation of reactive monomers [quinones and phenolic acids] during the degradation of organic matter, followed by the polymerization of some of these monomers into the humus molecule.”(8)

The mesh-like structure formed from Carboxyl type compounds (COOH), combined with the colloidal gel-like qualities, means we can describe this medium as a living macromolecular body. It also has high electronegative properties, allowing strong bonding with ions and clay to form ‘Stable Humus” or the Clay / Humus complex.

The electro bridging effect of ions (both negative and positive) and the complex adsorption (different to absorption) of colloidal clay particles then give even greater permanence to the humus body within the soil matrix.

This is only a very brief description of how amazing and complex the humus body can be.

I will now list a few of the properties humus has which are essential for life.

“Humus Properties Essential for Life”

Just one hundred grams of humus has a surface area of over eighty thousand square meters, providing the primary structure for soil life. (9) This means humus is the foundation for the web of life on earth. Some people have estimated that one hundred grams of humus can provide a home for over two hundred and fifty billion microbes. (10)

Landscapes with good levels of humus provide the biggest reservoir for fresh water supplies on the planet. This is due to the large surface area, the super sponge-like qualities of the humus plasma and the overall effect this has on the entire structure of the soil matrix. This reservoir, when fully hydrated, is responsible for ensuring regular functioning of local water cycles as well as providing the source of water for perennial river flows across the earth.  Just one hectare of soil at thirty centimetres of depth with ten percent humus can hold over 1.6 million litres of water.(11)

Humus is a source of true health for animals and humans. Humus contains over five hundred thousand different organic compounds and it has five times the nutrient storage of clay.(12) Such is the importance of the high nutrient storage of humus and its impact on the soil matrix that just three percent humus in the soil can be responsible for half of the nutrient storage in the soil. These nutrients and health compounds include essential amino acids, minerals, vitamins and vital secondary metabolites and phytonutrients.

One of the real dilemmas facing the world is that there is too much carbon in the atmosphere and to little carbon in our soils.  There is already enough carbon dioxide in the atmosphere to keep heating the earth for centuries, while at the same time, many of our agro-ecosystems are deteriorating as a result of having insufficient carbon. Building humus offers a real solution for reversing global warming and restoring a stable climate. If we were able to regenerate one hectare of land with ten percent humus we could sequester over 822 thousand kilograms of carbon dioxide equivalent, out of the atmosphere and back into the soil.(13)

Revegetating landscapes and building humus soils also offers an immediate solution for reducing land surface temperatures. The cooling effects of vegetation combined with the rehydrated landscape can reduce temperatures by as much as six degrees centigrade compared with bare ground.

Andrea Wulf has recently written, “Alexander Humbolt [ described as one of the most influential scientists in history] realized that nature is intricately interconnected in ways which surpass human knowledge. And he saw that living systems, and indeed the whole of the planet, are highly vulnerable to disturbances by human beings.” (14)

If we are going to respect humans and future life on earth we must regain a respect for humus, and adopt a ‘reverence for life’. This is something the Nobel Peace Prize winning humanist, musician, philosopher and scientist Albert Schweitzer argued when he spoke of ‘the universal ethic of the feeling of responsibility in an ever-widening sphere for all that lives.’ In his view ‘The great fault of all ethics hitherto has been that [people] believed themselves to have to deal only with the relations of man to man. In reality, however, the question is what is his or her attitude to the world and all life that comes within his or her reach.

Now more than ever, with so many challenges facing the earth’s ecosystems there is a need to adopt a greater ‘reverence for life’ and show respect for the remarkable complexity of natural processes such a humus formation.

 

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References

12. Albrecht, W.A. 1975, The Albrecht Papers Volume II: Soil Fertility and Animal Health, 1st edn, Acres U.S.A, Kansas City, Missouri, U.S.A.

 15. Bromfield, L. 1956, From my Experience, The Pleasures and Miseries of Life on the Farm Cassell & Co LTD 37/38 St. Andrew’s Hill, London

9. Handreck, K.A. 1938, Organic Matter and Soils (Discovering Soils No. 7) Commonwealth Scientific and Industrial Research Organisation.

5. Hennig,E. 2016 Secrets of Fertile Soils: Humus as the Guardian of the Fundamentals of Natural Life.  Acres USA.

10. Luebke, A. 2008  Organic fertilizer Seminar. Playhouse Hotel, Queen Street, Barraba. Available 
www.breakitdown.com.au/compost-seminars.html 

8. Maier, R.M. 2009 Biogeochemical Cycling in Environmental Microbiology (second edition).

 https://www.sciencedirect.com/topics/earth-and-planetary-sciences/humus

11,13 Morris G. D. 2004, ‘Sustaining national water supplies by understanding the dynamic capacity that humus has to increase soil water-holding capacity’. “Unpublished master’s dissertation” submitted for Master of Sustainable Agriculture, University of Sydney, July 2004.

14. Schweitzer, A  (1932) ‘Out of My Life and Thoughts’, George Allen and Unwin Ltd, cited in Bromfield, L. 1956, From my Experience, The Pleasures and Miseries of Life on the Farm Cassell & Co LTD 37/38 St. Andrew’s Hill, London

2,3,4,7.  Stevenson,F.J. and Olsen R.A. 1989, ‘A Simplified Representation of the Chemical Nature and Reactions of Soil Humus’, J. Agron. Educ.,  Vol. 18, no.2,

1, 6. Waksman, S.A. 1936, Humus: Origin, Chemical Composition and Importance in Nature, 1st edn, Bailliere, Tindall and Cox, Covent Garden, London.

14.  Wulf  A 2018, cited in ‘Drawdown - The Most Comprehensive Plan Ever Devised to Reverse Global Warming’ edited by Paul Hawken, Penguin Books, Great Britain.