Increase and Maintain the Soil Organic Matter Content

Technical articles

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Organic matter

To increase and maintain the amount of organic matter (OM), it is necessary to maximize OM inputs and minimize outputs, or at least keep them stable.

While it is impossible to stop harvesting to increase the OM rate, several solutions can help preserve it.

Points of attention to keep a stable OM rate

• Maintaining a (quasi-) permanent plant cover : it provides structural and light protection for the surface horizons as well as a future potential source of organic matter.

• Beware of the "Nitrogen hunger" phenomenon : often a consequence of adding organic matter that is too fresh or too lignified, because to degrade these components whose C/N ratio is high, the soil microorganisms need to mobilize the soil's mineral nitrogen . In the short and medium term, this metabolism therefore results in a deficit of mineral nitrogen available for the crops followed by a gradual return to balance. This phenomenon is worsened if such inputs are made during periods or conditions of low mineralization (soil too cold, hydromorphic, or pH too low, etc.).

• Time needed before reaching optimal production : in addition to the nitrogen hunger phenomenon, the development of soil biological activity, until reaching an optimum, can take several years with a definite impact on yields. This is therefore an Economic aspect to consider in the short term.

• Management of crop residues in arable farming :
  • By leaving the residues of the previous harvest on the plot after harvesting.
  • By adding animal excreta through grazing or spreading manure, slurry, compost or other carbon amendments.
  • By accelerating biomass degradation by burying it in the soil through tillage such as plowing which will distribute the organic matter evenly over the entire depth of worked soil. Conversely, no-till under cover crops will promote accumulation of organic matter on the soil surface which leads to better stability and water infiltration.

Techniques to increase OM rate

Increasing the organic matter content of your soil is a long-term effort that can take up to 10 years by adopting appropriate practices:

• Avoid humus-consuming crops.
• Limit soil tillage.
• Apply organic amendments: manure, slurry, vinasse, compost,...