In linguistic usage there is confusion about the meaning of the terms "humus" and "compost". Although both substrate forms have similarities, there are subtle differences in their formation and composition. Because of the similarities, compost is ideal for soil care.
Humus is the top layer of soil
Humus as a homogeneous soil layer
Humus is the top layer of soil in natural habitats, which consists of decomposed organic residues. Soil organisms process animal and plant remains and produce a homogeneous substrate rich in nutrients. The soil fauna needs moisture, air and heat for the conversion of the substances. If the conditions are not right, rot will form. A layer of humus on the ground stores water and provides nutrients to the plants.
Humus soils do not occur everywhere. Soil fauna is influenced by the carbon-nitrogen ratio. There is an imbalance in favor of carbon on the soils of coniferous forests. Needle litter acidifies the soil, which is why there are hardly any soil creatures here. In deciduous forests, the ratio is balanced and the soil fauna produces a thick layer of humus.
Compost as a heterogeneous composition
In contrast to humus, the compost soil has not yet completely decomposed. The substrate is a composition of plant waste, which is first processed into humus by the action of soil organisms. In common usage, mature compost soil is also referred to as compost. The compost substrate often contains unrotted and woody parts of plants, so that only parts of it contain homogeneous humus with a fine crumb structure.
While humus is created in natural habitats without human intervention, compost is actively produced. There is fresh compost that contains small amounts of decomposable organic residues. This substrate stimulates the activity of soil organisms. Finished compost contains large amounts of pure humus and small parts of substances that are difficult to decompose. It is slowly processed by soil fauna and provides a slow-flowing nutrient source.
use of compost
Humus has a balanced ratio of calcium and iron, potassium and aluminum, magnesium and manganese, phosphorus and sulphur, nitrogen and carbon. A well matured compost that has been stored for at least one year is comparable to pure humus. Not only does it serve as a fertilizer, it also has a positive effect on the soil.
Compost causes these effects:
- Promotion of the crumb structure
- Improvement of the water and air balance
- Increase in buffering capacity
- Maximizing aggregate stability