Eight (8) roles of soil organic matters.

The following are importance/Roles of soil organic matter:

Organic Matter creates a granular condition of soil which maintains favorable condition of aeration and permeability.
Water holding capacity of soil is increased and surface runoff, erosion etc., are reduced as there is good infiltration due to the addition of organic matter.
Surface mulching with coarse organic matter lowers wind erosion and lowers soil temperatures in the summer and keeps the soil warmer in winter.
organic matter serves as a source of energy for the microbes and as a reservoir of nutrients that are essential for plant growth and also hormones, antibiotics.
Fresh organic matter supplies food for earthworms, ants and rodents and makes soil P readily available in acid soils.
Organic acids released from decomposing organic matter help to reduce alkalinity in soils; organic acids along with released CO2 dissolve minerals and make them more available.
Humus (a highly decomposed organic matter) provides a storehouse for the exchangeable and available cations.
It acts as a buffering agent which checks rapid chemical changes in pH and soil reaction.