The organic fraction is the portion of a material made up of carbon-based matter that comes from living or once-living sources. In gardening and soils, this usually means plant residues, compost, manure, mulch, peat, bark, roots, and microbial biomass rather than sand, silt, clay, or gravel.
In soil, the organic fraction improves structure, water-holding capacity, drainage balance, nutrient retention, and biological activity. In composting or waste management, it refers to biodegradable materials such as food scraps, leaves, and yard debris that can decompose into stable organic matter.
The term fraction simply means a separated part or component of a larger whole. “Organic fraction” specifies the biologically derived component.
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