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. 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.