Ability of soils to provide the essential elements (mainly nitrogen, phosphorus and potassium) to plant growth through the action of living organisms (animals, insects, fungi, parasites) which have complex interrelations with one another and who feed on plant residues or animals. All of these organisms contribute to the degradation of organic matter which leads to the release of nutrients required by plants. An easily degradable fraction of organic matter contributes to soil fertility by feeding the microbial biomass, which itself participates in the nutrition of plants in nitrogen, phosphorus … Another fraction referred to as “stable” plays mainly a role in soil structuration. The balance of the ratio between degradation and stabilization of organic matter determines the biological fertility of soils.
This biological fertility promotes water availability thanks to the formation of micropores which retains water in the soil. The emblematic organisms of this biological activity are earthworms, whose presence is a bio-indicator of the soil’s fertility. They also contribute to the stability of soil structure and promote access to water and nutrients for the plants.
Furthermore, soil fertility contributes to the protection of plants: indeed, fertile soil is soil which possesses an important diversity of living organisms that can help with the biological control of the agricultural ecosystem.
Soil biological activity influences soil structure and is encouraged by practices such as crop rotation or the establishment of cover crops which limit erosion during winter. In terms of agroecology, conservation practices are based on reduced-tillage or no-tillage and help to maintain, and/or to promote this biological fertility with the perspective of a sustainable management of organic matter.