Set of practices used to increase or maintain the quantity (and/or quality) of organic matter in agricultural soils through the management of organic compounds, whether entering (biomass inputs within the soil) or outgoing (through degradation and/or loss).
The main origins of biomass inputs are the restitution of crop residues, the introduction of cover crops in rotations and the provision of animal waste through grazing. These inputs can also be produced outside the field as manure, compost and other sources of carbon.
The degradation of soil organic matter (SOM) is influenced by agricultural practices especially soil tillage. Practices such as ploughing generally lead to an acceleration of SOM degradation and its homogeneous distribution in the soil profile. Conversely, conservation tillage techniques, such as reduced or no-tillage, lead to a slower degradation of SOM and its progressive accumulation onto the soil surface.
In a short term, a sustainable management of SOM enhances the plants’ mineral nutrition by the mineralization of biomass. In a longer term, the increase in SOM contributes to the improvement of soil structure, of its porosity which participates in the transfer of water to the soil but also in the soil’s chemical fertility.
Thus, the management of organic matter in agricultural soils aiming to increase its stock is an agroecological practice, and an essential component of conservation agriculture.