Organic matter gets there primarily through the decomposition of dead plants, animals, and microorganisms, and their subsequent cycling by soil microbial communities.
Here's a breakdown of the process:
Sources of Organic Matter
Organic matter originates from various sources:
- Dead Plants: Fallen leaves, decaying roots, and entire dead plants contribute significantly to the organic matter pool.
- Animal Remains and Waste: Decomposing animal carcasses, feces, and urine add organic material to the environment.
- Microbial Biomass: Dead bacteria, fungi, and other microorganisms contribute their biomass to the soil organic matter.
- Organic Amendments: Humans introduce organic matter through compost, manure, and other organic fertilizers.
Decomposition and Cycling
The decomposition of organic matter is carried out by a complex community of soil microorganisms:
- Microbial Activity: Bacteria, fungi, and other microbes break down complex organic molecules into simpler compounds.
- Enzymatic Breakdown: These microorganisms secrete enzymes that catalyze the decomposition process.
- Nutrient Release: As organic matter decomposes, nutrients such as nitrogen, phosphorus, and potassium are released into the soil, making them available for plant uptake.
Transport and Distribution
Once decomposed, organic matter can be transported and distributed:
- Waterflow: Waterflow moves decomposed organic matter and dissolved organic compounds into the soil profile and eventually into streams, rivers, and other bodies of water.
- Soil Fauna: Earthworms and other soil fauna ingest and redistribute organic matter within the soil.
- Human Activities: Agricultural practices like tilling can redistribute organic matter across fields.
Examples
- Forest Floor: The forest floor is a prime example of organic matter accumulation, where fallen leaves and decaying wood create a rich layer of organic material.
- Agricultural Soils: Farmers enhance soil organic matter by incorporating crop residues, cover crops, and manure into the soil.
In summary, organic matter is generated from decaying organic material and moved through the decomposition process performed by soil microbial communities before being transported by waterflow, fauna, and human activities.
