Soil gets organic matter primarily through the action of living organisms that break down and mix organic materials into the mineral soil.
Soil receives organic matter from various sources, primarily plant residues and animal waste (manures). However, it is the activity of the soil's inhabitants that incorporates these materials into the soil structure.
The Role of Soil Organisms
As highlighted in the provided reference, microorganisms, earthworms and insects feed on plant residues and manures for energy and nutrition, and in the process they mix organic matter into the mineral soil. This feeding and breakdown process is crucial.
- Feeding and Decomposition: Organisms like bacteria, fungi (microorganisms), earthworms, and insects consume dead plants (roots, leaves, stems) and animal manures. As they digest these materials, they break them down into simpler compounds.
- Mixing: While feeding, these organisms move through the soil, effectively dragging and mixing the partially and fully decomposed organic matter with the existing mineral soil particles. Earthworms, for instance, ingest soil and organic matter, digest the organic components, and excrete nutrient-rich castings, distributing organic matter throughout the soil profile.
Recycling Nutrients
Beyond incorporating organic matter, these organisms also perform another vital function mentioned in the reference: they recycle plant nutrients. As organic materials decompose, the nutrients they contain are released into the soil in forms that plants can absorb.
Enhancing Soil Structure
The activities of soil organisms also contribute to soil structure. The reference notes that Sticky substances on the skin of earthworms and other materials produced by fungi help bind particles together. This binding creates stable soil aggregates, improving aeration, water infiltration, and root growth.
In summary, soil doesn't just receive organic matter; it is actively incorporated and processed by a diverse community of organisms feeding on available residues and manures, mixing them into the mineral components and releasing nutrients.
