How is humus created in the soil

What is humus?

Humous topsoil

The top 10 to 30 cm of the soil usually contain a lot of humus. The dark-colored, humus topsoil contains many of the important nutrients for plants and forms a central habitat for the diverse world of soil organisms.

Organic matter

All of the dead organic matter in the soil is referred to as humus. The organic components of the soil are important for the supply of the plants with nutrients such as nitrogen or phosphorus, but also for the pore distribution and thus for the air and heat balance of the soil. Depending on the form of humus, these nutrients are released to varying degrees.


The nutrients contained in the litter are only available to the plants when the existing organic material, e.g. leaves, twigs and needles, is decomposed. The leaves lying on the ground are crushed by the larger and smaller organisms in the soil and converted into the mostly "dark-colored humic substances" by microorganisms. One speaks here of 'humification'. However, there are differences in the decomposition of leaves and needles. When leaf litter decomposes, the nutrient-rich black humins are more likely to arise, while the decomposition of needles and branches predominantly produces the reddish-brown, acidic fulvic acids.


Nutrients "bound to the humic substances" then have to be released by microorganisms. One speaks of the "mineralization". Only now can the plant absorb the nutrients.