In healthy soil, plants feed through symbioses with microorganisms such as bacteria, protozoa and beneficial fungi.
In the early 20th century, the biologist RH France made the connections between microorganisms and humus formation accessible to a wider readership with his work: "The Edaphon - Life in the Soil".
He investigated the changes in the composition of microorganisms in relation to changes in environmental conditions and came to the conclusion that the greatest intact biological diversity prevails in soils that have not been worked. In addition, soil cultivation by ploughing even disrupts or prevents the formation of humus.
His works are still considered a cornerstone of biodynamic and regenerative agriculture.
In the early 1980s, Dr. Elaine Ingham, an American biologist, studied the relationships between microorganisms and coined the term "soilfoodweb."
The teachings of the soil food web form the basis for growing with Living Soil.
How the soil food web works and how we as gardeners influence soil life will be explained below.
In healthy soil, plants feed through symbioses with microorganisms such as bacteria, protozoa and beneficial fungi.
Already on the seed coat and even inside the seed there are bacteria whose metabolic products promote germination and as soon as the root comes into contact with the soil it is colonized by useful mycorrhiza fungi. Some of these also penetrate into the interior of the root and thereby help to transport nutrients to the root. Some, in turn, remain on the surface of the root and expand it with their widely branched mycelium. This expansion enables the plant to absorb more nutrients and is more resistant to environmental influences such as drought.
Plants control which microorganisms become part of this symbiotic relationship through root secretions, so-called exudates. Around 30% of the carbohydrates produced by the plant through photosynthesis are excreted through the roots.
Depending on which nutrients the plant needs, it excretes carbohydrates or individual nutrient molecules, thereby attracting microorganisms that absorb and metabolize these excretions.
Some of these metabolic products in turn form plant-available nutrients that are absorbed by the plant.
However, the majority of the exudates provided by the plant serve as an energy source for bacteria and fungi to reproduce and grow.
Only when these bacteria and fungi are metabolized by larger single-celled organisms (protozoa) do they form nutrients in a form that is available to plants.
Larger organisms such as nematodes, microanthropods or worms also hunt and eat bacteria, fungi and protozoa, thereby contributing to nutrient metabolism.
These microorganisms are present in large numbers in high-quality compost, especially if it was produced under aerobic conditions.
Just as the plant influences which microorganisms thrive in its environment, the composition of these microorganisms has a major influence on the nature of the soil and therefore on which plants thrive in it.
A distinction is made here between trophic levels. On the first trophic level, mainly grasses grow. The soil is rich in bacteria. On the next level, more complex plants such as perennials grow alongside grasses. As the diversity of vegetation increases, the ratio of bacteria to fungi increases. The last and highest trophic level is forest. Forest soil is rich in fungi.
In general, the more diverse the plant world, the more diverse the phytobiome, i.e. all the microorganisms involved in the plant's nutrient cycle.
As a gardener, you therefore have an influence on soil life. In order to promote soil connectivity and thus the production of permanent humus, it is sensible to keep the soil permanently covered with plants. The greatest possible diversity of plants should be chosen here in order to promote a high diversity of soil life. A living mulch layer (cover crop) is particularly suitable for this. This can fix nitrogen and provides additional organic material as food for soil life.
Environmental conditions should also be created that promote soil life. Soil life prefers a moist environment. If it becomes too dry, the reproduction rate of bacteria and the growth of fungi slow down. Protozoa and nematodes go into a kind of dormant state. The consequences are reduced nutrient conversion and reduced soil aggregation (humus formation).
Permanent planting and a mulch layer made of dead carbon-rich material (e.g. straw) protect the soil surface from drying out. But watering behavior also has a major influence on soil life and thus on nutrient conversion.
Since soils and substrates can vary greatly in terms of physical properties (water retention capacity), but site conditions (temperature, humidity, plant containers, etc.) also have a major influence, no generalized statement can be made about the "correct" watering behavior. A soil moisture value determined using a moisture sensor is only meaningful in conjunction with a check of soil life (bioassay)!
Once the optimal moisture level has been determined, it can be maintained constant through irrigation, thus promoting soil life, nutrient conversion and thus high growth rates.