Humus Article

This is a very technical and complex field. Without an adequate foundation in Chemistry, Botany and Nutrition, the reading of most articles that one finds on the INTERNET is about as informative reading as how to garden in Greek. Either there is too much technical mumbo jumbo, or the information is replete with hype-- or worse, full of misinformation. The only place appropriate for that kind of BS is perhaps in fertilizer compost itself!

The average gardener, houseplant enthusiast, or farmer, should not have be a soil scientist to comprehend how to employ basic soil-building principles. The writer certainly wasn’t when he started to try to figure out what the chemists and fertilizer purveyors were attempting to put across. However, before one can convincingly re-articulate techniques in simpler terms, one truly needs to understand what he or she is talking about, first. Unfortunately, most of us were sufficiently intimidated by High School Chemistry class that, that is where it all stopped.

For those of you who would still like to try to build upon your knowledge, but one brick at a time, this article might be ticket. To the extent that it is accurate, it may save you tons of reading of the kinds of articles with which I had to grapple, in order to glean the following gems.

Montmorillonite. If you forget everything you read after this but that word, you will have picked up a gardening tip and agricultural term that will prevent or overcome a multitude of mistakes. For the best source of this natural mineral complex go to:

That is not merely a self-serving opinion of my own, but was articulated by one of the Godfathers of Trace Mineral Research. He said:

The most outstanding form of Montmorillonite, is the brown source from Panaca, Nevada…The Panaca Montmorillonite is superior to all other known deposits. All other deposits of which I am aware were formed by volcanic action, which means that most of the ingredients present are in their elemental state and are not readily assimilated by animals and humans… In order for minerals to be more readily metabolized, they must first be chelated. [Melchior T. Dikkers PhD DSc, retired professor of organic-chemistry, Loyola University, scientist and research Bio-Chemist.] (Faust, 1986). Refer to www.montmorillonite.org

The term "humus" dates back to Roman times when the term was commonly used to designate the soil as a whole. The modern connotation has been applied exclusively to the completely decomposed organic matter of soils and composts, although it is still loosely used with reference to different fractions of this organic matter, as well as, to complexes formed by the action of chemical reagents upon a variety of organic substances. More precise terms for developing humus or its by-products can be found by consulting the paragraphs written about humic substances, organic matter, humates, humic acid and fulvic acid, inter alia.

In 1761 Wallerius first defined "humus" in terms of decomposed organic matter. However, the prevailing ideas concerning the chemical nature of humus and the mechanism of its formation at that time were still very vague. Most often it was considered as a complex formed in soils, in bogs, or in composts, from plant residues, by a special process of "humification".

The famous work of De Saussure, "Recherches Chimiques Sur La Vegetation", devotes considerable attention to humus. He reasoned that it is not a homogeneous substance, but that it consists of various readily removable complexes. Thaer differentiated between "mild humus", formed in the presence of sufficient oxygen, and "acid humus" or peat, formed with limited admission of oxygen.

Thus, the term "humus" came into general use at a time when organic chemistry was still in its infancy. We now regard most organic and inorganic compounds as more complex substances rather than of simple in chemical composition. [Humintech website]

Humus is formed by the decomposing action of soil microorganisms (e.g., bacteria and fungi), which break down animal and vegetable material into elements that can be used by growing plants. According to Waksman, this decomposition may take place “under aerobic and anaerobic conditions, usually in soils, composts, peat bogs, and water basins". Technically, humus itself, should be distinguished from the by-products it forms that are active constituents of organic fertilizer. Because of its low specific weight and high surface area, humus has a profound effect upon the physical properties of mineral soils with regard to improved soil structure, water intake and reservoir capacity, ability to resist erosion, and the ability to hold chemical elements in a form readily accessible to plants. [The Columbia Encyclopedia]

Simple Definition: HUMUS is the organic portion of the soil remaining after prolonged microbial decomposition [National Safety Council website].

Generally speaking, humus is recognizable as a brown to black complex and possessing cellular organization in the form of plant and animal bodies. It is the major component of organic matter in the soil, making up between 65% and 80% of the total. An interesting fact is that humus also assumes an important role as a fertility component of all soils, far in excess of the percentage contribution it makes to the total soil mass. However, the most important function of humic substances within the soil is their ability to hold water, and available water is without doubt the most important component of a fertile soil. Soils that contain high concentrations of humic substances hold water for crop use during periods of drought. Growers who routinely apply humate-based fertilizers, and conscientiously integrate production practices that preserve humic substances, can frequently harvest a crop even during periods of dry weather.

Complex carbohydrates synthesized by bacteria function together with humic substances, silt, and clay to form soil aggregates. As the humic substances become intimately associated with the mineral fraction of the soil, formation of colloidal complexes of humus-clay and humus silt, occurs. These aggregates, formed by electrical processes, increase the cohesive forces that cause clay components and the very fine soil particles to become attracted to one another. Once formed, these aggregates help create a more “friable” topsoil, or “crumb structure”. Soils with good crumb structure have improved tilth, and more porous openings (open spaces). These pores allow for gaseous interchange with the atmosphere, and for greater water infiltration. Humus adds to the soil structure by coating these mineral particles and holding them together; and thus serves as a major reservoir of plant nutrients.

In summary, although humus generally makes up only a small percentage of the total soil mass, its value to the overall picture cannot be overrated. Without humus, soils would be largely unproductive and merely increasing the amount of conventional fertilizers would soon reach the point of diminishing returns. On the other hand, organic farming which actively employs humus and fosters its retention, has proven to be a cost-effective alternative to chemical treatments, besides the fact that increasing humus actually improves soils long-term while simultaneously increasing nutrition and decreasing the effect of pollutants.

non-humic substances such as carbohydrates (a major fraction of soil carbon), fats, waxes, alkanes, peptides, amino acids, proteins, lipids [Petit]

Carbohydrates constitute 5 to 25% of the organic matter in most soils. Plant remnants contribute carbohydrates in the form of simple sugars, cellulose, and hemicellulose, but these are more or less decomposed by actinomycetes, bacteria, and fungi that synthesize polysaccharides and other carbohydrates of their own in turn.

Carbohydrates (CHO) are sugar-base molecules. Complex carbohydrates are chains of sugar molecules and are found in plant foods everywhere. Starch is a polymer or long string of glucose molecules… [S J Gislason]

Three major groups of carbohydrates

1. Monosaccharides: aldehyde and ketone derivatives of the higher polyhydric

2. Oligosaccharides: a large group of polymeric carbohydrates consisting of a

· Polymeric molecules of various sizes and shapes which are attached to clay and/or humic colloids very strongly

Sugar	% of Organic Matter
Amino Sugars	2-6%
Cellulose	< 15 %
Hexose sugars	4-12%
Pentose sugars	&lt5
Uronic acids	1-5%
Others	trace

Soil Lipids

Rather than a specific type of compound, the class of organic compounds designated as lipids represents a convenient analytical group. Lipids are comprised of a diverse group of materials ranging from relatively simple compounds such as fatty acids to more complex substances such as chlorophyll, fats, polynuclear hydrocarbons, resins, the sterols, terpens, and waxes. So-called fats, resins and waxes constitute the bulk of the soil lipids. In normal aerobic soil it is believed that the presence of lipids is largely attributed to the remains of plant and microbial tissues.

Lipids are physiologically active. Some compounds act as growth hormones whereas others have a depressing effect on vegetative growth. Waxes and similar substances may be responsible for the water-repellent condition of certain sands.

Three major groups of carbohydrates

Sugar

Soil Lipids