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Microorganisms have long been overlooked, but they play a major role in soil sanitation and structuring.
They are invisible to the naked eye. With a size of less than 10 µm, i.e. one hundredth of a millimeter, microorganisms fall into two large families. On the one hand, prokaryotes, which include all unicellular organisms that do not have a nucleus, and whose main representatives are bacteria and archaea. On the other hand, the fungi, which can be unicellular or multicellular. In this case, they are in the form of mycelium, that is to say, a vast filamentous underground structure.
Despite their microscopic size, micro-organisms represent between 75 and 90% of the living biomass present in the soil. Above all, they play a major role in the sanitation and structuring of the soil, but also in the process of decomposition of organic matter and in the absorption of nutrients by the roots.
Today, so-called conventional agriculture tends to reduce the organic matter content of soils. This leads to imbalances, particularly chemical ones, which threaten the proper biological functioning of the soil and, in the long run, its fertility. Thus, tillage (such as plowing) disturbs microbial populations, because it constantly upsets a soil that seems inert at first glance, but is in fact teeming with life. Overcultivation of a plot of land can also have negative consequences on its productivity, as the soil does not have time to regenerate between harvests. Finally, the use of phytosanitary products is a threat to the balance of a living soil, as they eliminate some of the effective microorganisms in the process.
Towards a change in agricultural methods
To recover a living soil capable of ensuring the sustainability of production systems, the only effective solution is to change agricultural practices. This is what the Belloeil farm in Saint-Mayeux, in the Côtes-d’Armor region, wanted to try. This farm of 190 sows produces part of the feed for its animals with a cropping system based on a short corn-cereal rotation. A few years ago, the farmers wanted to improve soil fertility without systematically using phytosanitary products, by maximizing the effectiveness of their manure. They opted for the use of microorganisms, in this case a composting additive called Bacteriolit, which can be added to the manure or spread directly on the fields.
The results are encouraging to say the least. Working the soil is made easier by the presence of microorganisms, and yields are more than satisfactory. Trials carried out on sandy soil, which is more easily leached by rainwater, also show that nitrogen losses are 30 to 35% lower when the plot has been fertilized with seeded manure.
Not to mention the production of humus, which is greatly enhanced (+117% of humic acids over a period of five months). Finally, the micro-organisms encourage the return of earthworms, which are essential for bringing nutrients to the surface. There are 700 to 1000 galleries/m2, compared to less than 300 galleries/m2 for a soil not sown with Bacteriolith. This difference allows a gain in soil oxygenation of more than 25%, as well as a better capillary rise.