Stable Organic Matter - Humus
Humic substancesNon-humic substances Fulvic acidHumic acidHumin i.e. polysaccharides, proteins, lignins, etc. In their natural or transformed states soluble in acid soluble in alkali insoluble in acid soluble in alkali insoluble in acid insoluble in alkali Humus Sparks (2002) Stable Organic Matter - Humus
Fulvic AcidHumic AcidHumin Light yellow Yellow brown Dark brown Black Grey black decrease in degree of solubility increase in molecular weight increase in carbon content 45% 62% decrease in oxygen content 48% 30% decrease in exchange acidity 1, meq 100 g -1 meq 100 g -1 Sparks (2002) Stevenson (2002) increase in nitrogen content 0.8% 5.0% Stable Organic Matter - Humus
Carboxyl Alcoholic OH Carbonyl (ketone) Amine Acidic groups Phenolic OHQuinone Neutral groups Basic groups Polyfunctionality Soil Organic Matter - Composition
Probable structures can be estimated using the dimer concept ? Soil Organic Matter - Composition
Carboxyl dimer Alkyl chain Phenolic - OH Carbonyl Amine
Soil Organic Matter - Composition