FUNCTIONS OF ORGANIC MATTER IN SOIL

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What is Organic Matter

Soil organic matter consists of a variety of components. These include, in varying proportions and many Intermediate stages: 
raw plant residues and microorganisms(1 to 10 per cent)
"active" organic traction (10 to 40 per cent)
resistant or stable organic matter (40 to 60 per cent) also referred to as humus.


Organic Matter in Virgin and Cultivated Soil


Soils in Alberta are divided into soil groups (zones) based on the amount of organic matter they contain. They occur in geographic zones from the southeast to the northwest and are identified as the Brown, Dark Brown, and Black Chernozemic (prairie) soils.

The Brown soils have the least amount of organic matter because of the relatively small inputs of plant residues contributed by the short grass prairie vegetation under which these soils developed. Black soils developed under cooler and wetter conditions which allowed for more grass growth and thus a greater accumulation of organic matter. 


Why Soil Organic Matter


Soil organic matter contributes to a variety of biological, chemical and physical properties of soil and is essential for good soil health.


Soil health is important to optimise productivity in agricultural systems.
Healthy, productive soil is a mixture of water, air, minerals and organic matter.
In turn, soil organic matter is composed of plant and animal matter in different stages of decay, making it a complex and varied mix of materials.



Human interventions that influence soil organic matter


Various types of human activity decrease soil organic matter contents and biological activity. However, increasing the organic matter content of soils or even maintaining good levels requires a sustained effort that includes returning organic materials to soils and rotations with high-residue crops and deep- or dense-rooting crops

Soil organic matter levels can be maintained with less organic residue in fine textured soils in cold temperate and moist-wet regions with restricted aeration.