Humus: What is it and How is it Formed?

Secrets of Fertile Soils

Humus forms as a result of the complicated interplay of inorganic conversions and the life processes of the microbes and tiny creatures living in the soil — the soil ecosystem. Earthworms play a particularly important role in this process. Humus formation is carried out in two steps. First, the organic substance and the soil minerals disintegrate. Next, totally new combinations of these break down products develop, which leads to the initial stages of humus. Humus formation is a biological process. Only 4-12 inches (10-30 centimeters) of humus-containing soil are available in the upper earth crust. This thin earth layer is all that exists to provide nutrition to all human life. The destiny of mankind depends on these 12 inches!

Cultivated soils with 2 percent humus content are today considered high-quality farmland. What makes up the remaining 98 percent? Depending on the soil type, soil organisms constitute about 8 percent, the remains of plants and animals about 5 percent, and air and water around 15 percent.

The remaining 70 percent of soil mass is thus of purely mineral origin. The mineral part of the soil results from decomposition and the erosion of rock. The dissolution of these components is carried out by the lithobionts, which can be seen as the mediators between stone and life. It was Raoul H. Francé who coined the term “lithobiont,” which means “those who live on stone.” The lithobionts are the group of microbes that begin the formation of humus. They produce a life-giving substance from the nonliving mineral. On the basis of this process, living matter, earth, plants, animals and human beings can begin, step by step, to build.

Only soils with an optimal structural state of tilth have a humus content of 8-10 percent. Untouched soils in primeval forests can, at best, reach 20 percent. A tropical jungle can’t use up all its organic waste, so humus can be stored. All forests accumulate humus, but real humus stores only emerge over the course of millennia. Once upon a time accumulations of humus known as chernozem (Russian for black earth) could be found in the Ukraine.

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Almost all plant communities (except for leguminous plants and untouched forests) use up more humus than they can produce. Strictly speaking, each harvest and each growth of cultivated plants is accompanied by a loss of humus. The lost humus cannot be replaced by any kind of mineral fertilizer. Both deciduous woods and mixed forests can provide their own humus because they are able to make use of their own discarded leaves. Even in nature, without human influence, humus is only produced in deciduous forests and on undisturbed land.

Humus is favorably disposed toward the vegetable rather than the animal metabolism. This is why manure, with its high proportion of animal excrement, cannot support natural humus formation. Manure has to be turned into humus before it can be used for fertilization.

Why is this? The microbes living in the soil are more favorably disposed toward the decomposition of pure cellulose than the disintegration of animal excrement, which leaves the intestines in an anaerobic state. This fact was unfortunately not recognized by earlier generations.

Rather than being subjected to aerobic decomposition, manure was simply buried in the field. When introduced to the soil in this way, the rotting anaerobic matter remains an alien element for quite a long time. The substances are disintegrated by specific rot microbes, whereas the microbes inherent to the soil, living under aerobic conditions, are driven out. The question of whether anaerobic or aerobic microbes predominate, and therefore whether rot or decomposition occurs is crucial for susceptibility or health of the plants grown in a soil. The following example reveals how little humus is produced when manure is used: if a dose of 400 quintals (roughly 88,000 pounds) of stable manure is applied to each hectare of soil (on light soils), then after half a year, half of the amount of the manure can be found, after one year only a fifth, and after two years practically nothing of the manure is left. The organic matter in the soil is quickly consumed and assimilated then mineralized without the production of humus.

Typical manure cultivation has been practiced in Germany for the last 200 years, which, if manure cultivation were effective, would mean that this country has soils very rich in humus. But that’s not the case. Manure is only the remains of the substances that served the animal as nutrition. All the highly nutritive proteins, carbohydrates, fats and so on that were produced by the plant have been taken away from the soil, and the excrement is poor in nutrients.

In spite of these shortcomings, the custom of manure spreading is still widely practiced. Here is an example; several years ago a renowned child specialist wanted to find out whether the quality of vegetables grown for babies and young children was influenced by fertilization. How did he go about it? He tested the influence of: a) only manure; and b) manure plus mineral fertilizer.

The result: The vegetables fertilized exclusively with manure proved to be not only inferior, but actually dangerous for health because many of the children in this group were diagnosed with hypochromic anemia. The report about the influence of stable manure on the quality of vegetables even referred to humus-fertilized soils. Such misinformed ideas about humus can still be found everywhere. Apparently researchers failed to notice that manure is a rot product that contains poisonous substances like indole, skatole, putrescine and toxic phenols, and that as a result the quality of soil products is bound to be influenced in a harmful way.

The question, “What is humus?” is not easy to answer, as we will see. A German layman, if asked, would probably check the Brockhaus Encyclopedia for an answer. There he would find the following definition: “Humus, black-brown matter in the topsoil, produced by the putrefaction of vegetable and animal matter. Humus is rich in carbon and generally acidic as a result of its humic acid content. It increases the water storage potential of the soil and produces carbonic acid, which disintegrates minerals.” Even if this statement is quite basic, one can glean from it some important functions of humus. Today we know that plant remains decompose down to their most basic components and plasma residues. Only after the total disintegration of all substances into the elements carbon, nitrogen, potassium, phosphorus and magnesium can construction begin on what today is generally called humus.

Researchers have proven that plants can take in the final forms of plasma (matter that is not decomposed to the state of mineralization) up to a certain molecular weight. This plasma is then included in their systems. This brings us back to the cycle of living substances, which has already been mentioned.

Humus cannot be regarded as a real substance but rather as a process, a formation, built from a multitude of constantly changing factors. In order to define humus, the living substance factor has to be taken into consideration. The law of harmony, that is, the law of balance, reigns over all living things.

We know all too well the consequences of a disturbed harmony in the soil, this harmony being the precondition for a normal soil life. One could also say, “Harmony equals balance through well-functioning regulative systems in the soil.”

Humus and soil are subject to the same laws as all other living things. But modern agriculture refuses to work in the same way, and the results of ignoring these laws can be seen in our ailing fields with their depleted soils and damaged structures, and in our disease-prone cultivated plants. Dead soils eventually become barren desert land.

Up until now, humus could not be analyzed using the usual chemical methods. Acids, bases, salts and so on had to be used for chemical investigations, but those substances destroy life and its functions. Incineration did not reveal anything about the structure and the capillary system of the former humus, and without this information, nothing would have been discovered about the organisms, how they related to each other and the harmony in which they worked.

We can discern one key to determining the value of humus from the relationship between carbon and nitrogen, if this can be calculated. Highly fertile soils should show a carbon/nitrogen relationship of 10:1. Biological investigations, however, are far more interesting because they refer to the living milieu, and in order to form an idea of the world of little creatures one has to study the life processes of the symbiosis of the living communities.

Clay-Humus Complex

Even with the above factors, the definition of humus has not yet been exhausted. In this “primitive tissue,” the very finest soil particles, the colloids, play a particularly important role. In humus, different nutrients are bound together with clay minerals through adsorption processes. This association of organic fragments such as humic substances with inorganic particles such as clay minerals is usually called the “clay-humus complex.”

Without minerals, a true humus formation would not be possible. Clay and humus colloids are able, mainly due to their electronegative qualities, to take up the bases present in the soil, hold them tight and absorb them. Thus, clay and humus together are generally referred to as adsorption complex.

Humus as the clay-humus complex, in other words as the living organic matter in the soil, also has a buffering effect. Nutrients are only given to the plant if they are required, so an overdose is impossible. However, plants growing on soils lacking in humus take in more nutrients than are needed for the accumulation of plant matter when mineral fertilization occurs. Because organic fertilization prevents superfluous consumption, it can be seen as an energy saving measure.

We should bear in mind, that which has, until today, been referred to as humus (our ancestors also used the term to mean the “Primeval Force” of soil) is not matter according to most recent knowledge, but a biological performance. This performance is typical of Mother Earth, and such performances cannot be found anywhere else.

Secrets of Fertile Soils: Humus as the Guardian of the Fundamentals of Natural Life by Erhard Hennig is available from Acres U.S.A. For more information, follow the link above, visit or call 800-355-5313.

By Erhard Hennig. Excerpt from Secrets of Fertile Soils: Humus as the Guardian of the Fundamentals of Natural Life by Erhard Hennig, published by Acres U.S.A.


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