Organic matter
/ɔrˈɡænɪk ˈmætɚ/
Definition
Organic matter refers to carbon-based material from living or once-living organisms in soil or growing media, such as decomposing leaves, roots, compost, and microorganisms. In plant contexts, it is a soil component rather than the mineral particles of sand, silt, and clay. As it breaks down, it forms humus, the stable dark fraction that influences soil structure, water holding, nutrient retention, and biological activity around roots.
Practical Relevance
- Soil structure and root growth: In mineral soils, organic matter helps bind particles into stable aggregates. This improves aeration, reduces compaction, and makes it easier for roots to spread and take up water.
- Water and nutrient buffering: Organic matter increases the soil’s ability to hold moisture and retain plant nutrients such as potassium and calcium. That buffering effect can make growing conditions more even between watering or rain.
- Support for soil life: As organic matter breaks down, it feeds bacteria, fungi, and other soil organisms. Their activity releases nutrients into forms plants can use and helps build a more active root zone.
- Use in beds and containers: Gardeners often add compost to raise organic matter in planting beds and potting mixes. This is especially useful in sandy soils that drain too quickly and clay soils that stay dense and poorly aerated.
Related Terms
Manure
Manure is animal dung, sometimes mixed with urine, bedding, or plant litter, used in gardening and horticulture as an…
Leaf mould
Leaf mould is partially to fully decomposed fallen leaves, used in gardening as a soil-conditioning organic material…
Green manure
Green manure refers to a cover crop grown mainly to be cut and turned into the soil while still green, rather than…
Soil amendment
Soil amendment refers to a material added to soil to change its physical or chemical properties, such as structure…
Mulch
Mulch refers to a layer of material spread on the soil surface around plants or over planting beds. It is a gardening…
Loam
Loam is a soil type defined by a balanced mix of sand, silt, and clay, usually with some organic matter. This…
No-dig gardening
No-dig gardening is a soil-management technique in which beds are not turned, double-dug, or rototilled. Instead…