APPROACHING A PURE BALANCE

The main principles of the natural mechanism

In fact, if we observe that 25% of all known species live underground, it is estimated that they represent more than 75% of all global biodiversity. We are talking about billions of billions of organisms in the soil.

These organisms are both plants, flora, and animals, fauna. Among animals we distinguish megafauna, macrofauna, mesofauna and microfauna.

On the flora side, these are the macroflora and the microflora.

Depending on their size, soil organisms have different functions. Large ones stir, aerate and mix organic matter to create an environment capable of supporting smaller life forms. They have mechanical and chemical actions. Small organisms break down organic and mineral elements in the soil to make them available to other organisms and plants. Their actions are essentially chemical.

Soil life should be considered as an association between the soil itself and the plant. Soil organisms feed mainly on plant and animal organic matter, and this life is due to the presence of the soil-plant couple. Without soil, there is no plant, and without plant, there is no natural or cultivable soil. In most works on soil life, the authors describe it starting with the functions of the smallest organisms and ending with the largest. However, the process of degradation of organic matter begins with its fragmentation and incorporation by the larger organisms before its humification and mineralization by the smaller ones.

Megafauna

It is composed of moles, shrews, hedgehogs, voles (their populations are regulated by weasels, stoats, foxes, cats, and diurnal and nocturnal birds of prey), birds, salamanders, newts, toads, tree frogs, slow worms and lizards. All these "large" animals have the following functions: Mixing and decomposing organic matter with their legs as they move; Fragmentation of organic matter which then becomes usable by smaller organisms; Regulation of populations; Aeration of the soil; Production of organic matter through their excrement and corpses.

Macrofauna

These are organisms whose dimensions vary from 4 to 80 millimeters. The best known are earthworms. They disappeared (only a few scattered species remain) from Canada 12,000 years ago, but were imported to the continent by Europeans. Contrary to what is often reported, they are half as numerous on North American soils as on European soils. In Europe, there are 300 to 1,000 earthworms per square meter, while in North America there are 100 to ± 500, the average being 200 to 300, for the same surface area. We distinguish:

Epigeal worms: they transform twigs, debris, dead leaves and work to decompose organic matter. Present on the surface, they do not form galleries; Endogenous worms: they consume buried organic matter that they reject in the form of soil in the castings. They live deep in horizontal galleries;

Anectic worms: They feed on fragments of organic matter after having excreted their excrement. They move from top to bottom and from bottom to top. They stir up the soil horizons, burying surface organic matter and bringing up mineral matter. Woodlice decompose dead leaves, dead wood, algae, hyphae or dead insects. They then feed on this decomposing organic matter. Vegetarian species of myriapods, or millipedes, cut leaves and plant debris. Carnivorous species are predators of small animals.

Three types of insects are involved in soil life: Flies, such as black soldier fly larvae, live in fresh or decomposed organic matter. The larvae break down organic matter, which accelerates decomposition; Beetles, such as geotrupes and some species of beetles, which recycle organic debris. Carnivorous, they feed on mollusks, insects and arthropods. Exclusively plant pests, they destroy crops.

Hymenoptera are mainly represented by ants. They participate in the mixing of soil, organic matter and its mineralization. Slugs feed on soft plant matter and accelerate the rotting of organic matter by grinding. They facilitate the work of bacteria and fungi. Snails feed on living or dead plant debris, carrion, fungi, moss and insects. Slugs, snails and slugs dig more or less deep underground paths in the soil and facilitate the circulation of air, water and roots.

Mesofauna

These are organisms ranging in size from 0.2 to 4 millimeters. The mesofauna is composed of arachnids: spiders, mites, oribatids and pseudoscorpions; proturans, diplurans, nematodes and springtails. The main functions of the mesofauna are to continue to mechanically fragment organic matter. This fauna: Segments organic matter into smaller particles; Increases the surface area of ​​exchanges usable by microorganisms on organic matter; Contributes to the formation of humus; Causes changes in pH.

Microfauna

These living organisms measure less than 0.2 millimeters. They are protozoa and amoebae that develop in water or in very humid environments. They move in the soil by contractile fibers, vibrating cilia for ciliates, or whip-shaped filaments for flagellates. The functions of these microorganisms are to: Consume bacteria, fungi, sometimes other protozoa, algae and organic matter; Produce waste containing carbon and mineralized nutrients available to the plant; Live near the roots to which, through their digestion, they mainly provide nitrogen. Indeed, 80% of the nitrogen required by a plant is provided by the waste of protozoa.

Macroflora

Very often forgotten, it is mainly composed of plant roots. When they are alive, they produce rhizodeposits which are organic secretions such as cells detached from the root, lysates, mucilages and exudates. Rhizodeposits serve as a chemical relay between plants and soil microorganisms. Their production has effects closely linked to the microflora. When they are dead, the roots add organic matter to the soil. All roots, including those of spontaneous weeds, play a role in soil life.

Microflora

Spherical or oval, rod-shaped (bacilli) and spiral bacteria are invisible to the naked eye. It is estimated that there are between 10 million and 1 billion bacteria per gram of soil. The functions of non-pathogenic bacteria are to: Solubilize mineral substances released during humification and thus make them available to plants; Modify the pH of the soil; Produce antibiotics that protect plants. Different from bacteria by the composition of their cell walls, their food sources and their genetic heritage, archaea or archaeobacteria: Actively participate in the nitrogen and carbon cycles; Help make nutrients available to the plant; Produce specific antibiotics. Intermediate organisms between bacteria and fungi, actinomycetes: Break down cellulose and chitin; Humify and mineralize organic matter of all origins in order to make nutrients available to plants; Develop certain humic acids and water-soluble organic acids. Fungi, also non-pathogenic, develop in the form of long filaments, called hyphae. The union of several hyphae forms a visible mass, the mycelium. The functions of fungi are to: Transform organic matter into humus; Transform nitrogen into proteins. It is one of the rare organisms on earth that degrades these materials; Form mycelia that participate in soil stabilization; Act favorably on the structure of the soil; Absorb mineral elements and trace elements to make them available to plants; Fix nutrients in the soil.

There are four types of soil fungi:

• Basidiomycetes, decomposers of cellulose and lignin from dead leaves.
• Myxomycetes, which feed on manure and decaying matter.
• Oomycetes that break down carbohydrates, cellulose and chitin.
• Ascomycetes, nitrogen-fixing bacteria that release phosphorus from plants and produce antibiotics.

Present in 100% of woody plants and 95% of herbaceous plants, mycorrhizal fungi or mycorrhizae live in symbiosis with the plant at the root level. They receive carbon and carbohydrate substances from plants, mainly from rhizodeposit exudates. They provide plants, after extraction from the soil, with nitrogen, phosphorus, copper, zinc and other trace elements. This symbiosis promotes the development and interactions between microorganisms in the microflora. It boosts biodiversity. For more information, listen to the program Biostimulants and mycorrhizae: allies for soil and plant health.

Microscopic algae have several functions: They cause chemical erosion of the bedrock by generating carbonic acids. Mineral elements and dead algae lead to the creation of soil; They fix atmospheric nitrogen; They solubilize calcium; They limit leaching by transforming soluble mineral components into organic complexes retained by the clay-humic complex; They act as binders and aggregators between soil particles. They increase the cell mass of the roots and strengthen the defenses of plants.

Slime molds, or blobs, are slimy materials that live in moisture, on rotting wood, leaves, manure, lawn thatch, decaying fungi, and other organic matter. They feed on bacteria and yeast, but also insect larvae, earthworms, and some beetles. They participate in the soil's nutrient cycle, and the slime they produce binds soil particles together.

A complex environment where all actors are interdependent This brief portrait shows that each actor in soil life needs the one that preceded it and the one that followed it. Each has functions that depend on the presence of other organisms. Each form of life acts as a regulator, both of pathogenic organisms, but also to prevent the proliferation and therefore the imbalance of one of the organisms.