General Properties of Humus

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)

Muhammad Ramzan Rafique
Muhammad Ramzan Rafique

I am from a small town Chichawatni, Sahiwal, Punjab , Pakistan, studied from University of Agriculture Faisalabad, on my mission to explore world I am in Denmark these days..

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