Explain the importance of humus for soil fertility. Why the more humus, the more fertile the soil?

The fertility of the soil is explained by the presence of useful elements in it. They ensure the growth of plants, saturate them with vitamins, cause active growth and resistance to diseases. The key to soil fertility is the presence of humus in it. The importance of humus for soil fertility can be explained as follows:

humus is formed as a result of the decay of organic objects. These can be dead animals, birds, plants, their waste products. For example, in desert soils, the humus content does not exceed one hundredth of a percent. And in the chernozem layer, it can be more than 15%;
humus contains all the nutrients. Therefore, only the soil rich in humus will be fertile. Without this, it will be simply impossible to grow cultivated plants;
humus contains nutrients, acids and alkalis. They have been forming over the years. The more varied life in a particular area, the more fertile the soil there will be.
Thus, thanks to humus, the soil becomes fertile and suitable for growing cultivated plants. Accordingly, depending on the humus content, the value of the soil is determined.

Where is humus in the soil
Humus is the topmost soil layer. It is in it that the seeds of plants fall and grow into trees or shrubs. As indicated above, this layer is formed due to humification (decay) of the remains of animals and plants. Since they cannot get into the deep layers of the soil in any way, humus forms at the surface of the earth.

Below the humus layer there are less fertile layers. But the roots of many plants reach these layers. However, they get all the nutrients from the humus layer.