TOPIC 1: Living soil as basis for healthy food also in a changing climate

TOPIC 1: Living soil as basis for healthy food also in a changing climate

In this topic you will get a lot of information on the matter of soil. You will learn about the three-phase system, the different components and the importance of soil as the basis for the healthy growth of plants in gardens. 

Soil is the most important resource and is mainly responsible for the healthy growth of plants in gardens. As gardeners and garden enthusiasts, it is necessary to have a basic knowledge of the matter soil. It is essential to be familiar with the properties of the soil in order to make the right choice of plants and processing and, if necessary, improvement measures.

Soil is called a three-phase system, after the matter soil is composed of the three components soil air, soil water and soil solids. Depending on the soil type and use, the three phases are present in the soil in different proportions.

Total soil solids consist of mineral matter (stones, gravel, sand or clay of various sizes and types) and organic matter (humus, plant roots and soil organisms).

Humus is the part of the soil that is formed from dead organic matter. These are dead plant parts as well as decomposed animals, fungi and bacteria. As an essential component of organic matter, the humus content is a crucial factor for nutrient availability and thus for soil fertility. 

Good to know:
➤ Humus has the essential property of absorbing water and storing nutrients.
➤ For example, a sandy soil with a high humus content can absorb and store much more water than sandy soil with a low humus content.
➤ The essential characteristic for determining the humus content of a soil is its color. Here, the principle “the darker the soil, the higher the humus content” applies.
➤ The soil organisms need the humus as a basis for life and in return provide nutrients for the garden by making them available to the plants.

Soil structure

Fertile soils have a crumbly, loose structure that ensures good water retention and at the same time also good aeration of the soil. A loose, crumbly soil structure and so a nutrient-rich, fertile soil can be maintained mainly by adding nutrients, for example by mulching, as well as by careful soil cultivation (see Topic 5).

pH value: Depending on the type of rock, soils are more or less acidic or basic. The pH value influences the availability of nutrients. On very acidic soils (low pH), humus accumulates, but the activity of microorganisms is strongly limited, which is why fewer nutrients are available for plants. On alkaline soils (high pH), little humus is built up and nutrients such as iron and phosphate, in turn, cannot be taken up by plants.


The pH value can be determined using test strips or special measuring devices. The pH value can also be derived or estimated from indicator plants. Most plants do well with a pH value between 5.5 and 7.0.

Indicator plants:

Indicator plants can help provide an initial impression of soil conditions. They only grow if the soil has certain properties. The presence of different species of wild plants can be used to draw conclusions about the characteristics of a soil.  Both lager accumulations of one species, as well as the occurrence of several species with the same site requirements, can provide clues. If, for example, nutrient-loving plant species are found in greater numbers, it can be concluded that the soil has a higher nutrient content.

Soil types and their characteristics:

Light soil (sand and loamy sand): is easy to work and well aerated. Water and nutrient content are low.

Medium soil (sandy loam or clay): Loamy soils are very fertile soils. The sand content provides good aeration and workability. The clay part allows nutrients to be stored well.

Heavy soil (clay loam, clay): Due to the high clay content, these soils have low water permeability and are therefore often poorly aerated. Clay stores nutrients but releases them only to a small extent due to its high cohesiveness.


Ö Zeigerpflanzen, 10.06.2023

Plantura: Humus, 10.06.2023