Non-Humic substances

• The term non-humic substances refer to the group of identifiable biomolecules that are mainly produced by microbial action and are generally less resistant to breakdown.
• It accounts 20-30 % of the organic matter in soils.
• They include carbohydrates, proteins, peptides, amino acids, nucleic acids, purines, pyramidines, waxes, resins, pigments and other low molecular weight organic substances.
• These substances are easily degraded in soils and have short life span in soil.
• They are less complex.

Humic substances

• They comprise about 60 to 80 % of the soil organic matter.
• They are comprised of huge molecules with variable, rather specific, structures and composition.
• They are amorphous, dark colored, partly aromatic, hydrophilic, chemically complexed, molecular weights varying from 2000 to 300,000 g/mol.
• Because of their complexity, they are the organic materials most resistant to microbial attack.