Property | Remarks | Effect on soil |
Colour | The typical dark colour of many soils is caused by organic matter. | May facilitate warming |
Water retention | Organic matter can hold water up to 20 times its weight. | Helps prevent drying and shrinking improves moisture retention in sandy soils. |
Combination with clay minerals | Joins soils particles into structural units called aggregates. | Permits gas exchange; Stabilizes structure; increases permeability. |
Chelation | Forms stable complexes with Cu2+, Mn2+ Zn2+, and other polyvalent cations. | Buffers the availability of micronutrients to higher plants |
Solubility in water | Insolubility of organic matter results partially from its association with clay; salts of divalent and trivalent cations with organic matter are also insoluble; isolated organic matter are also insoluble; isolated organic matter is partly soluble in water. | |
pH relations | Organic matter buffers soil pH in the slightly acid, neutral, and alkaline ranges. | Help maintain a unit form reaction (pH) in the soil |
Cation exchange | Total acidities of isolated fractions of humus range from 3,000 – 14,000 mmol kg-1 | Organic matter brings about a 20-70% increase in CEC in many soils. |
Mineralization | Decomposition of Organic Matter Yields CO2, NH4 – PO43- and SO42- | A source of nutrients for plant growth. |
Combination with organic molecules | Affects bioactivity, persistence, and biodegradability of pesticides. | Modifies the application rate of pesticides for effective control. |
Source: Adapted From Stevenson (1982-18)