Organic matters and their importance

• Soil organic matter (SOM) is defined as all organic materials found in soils irrespective of origin or state of decomposition. (University of Minnesota, 2002).
• Soil organic matter is that fraction of the soil composed of anything that once lived.
• It includes plant and animal remains in various stages of decomposition, cells and tissues of soil organisms, and substances from plant roots and soil microbes.
• Or the sum total of organic carbon containing substances in soil is referred as soil organic matter. It varies from < 1% in desert soil to 100% in organic soil.

Classification of soil organic matter components

a. Living Organism

b. Identifiable dead tissues : detritus

c. Non-living/ non tissues : Humus

I. Humic

i. Insoluble organic : Humin ( Highly condensed complexed with clays)

ii. Soluble organic:

• Humic acid ( Dark brown to black, medium molecular wt. (up to 300,000 g/mol) )
• Fulvic acid ( Yellow to red, lower molecular wt. (2,000 – 50,000) )

II. Non-humic