Humic Acids

are the water soluble organic acids naturally present in soil organic matter. Humic Acids are not a single compound, but rather a collection of different molecular weight compounds with similar characteristics. They are usually defined by the process through which they are isolated, rather than by a particular chemical structure. Humic Acid provides a source of soil building carbon.

Soil Organic Matter Can Exist As:

Living Plant and Animal Matter.
Identifiable Dead Tissue – Detritus.
Decomposed – Non Living, Non Tissue Humus.
Close-up of dried, cracked earth.

Not All Organic Matter is Humus! Four Ways to Identify Humus Are:

  • Origin or parent material cannot be identified.
  • All sugar, fiber, cellulose, lignin, gums, protein, etc, have been decomposed.
  • The material resists further decomposition.
  • It is highly concentrated and a condensed form of the parent material.

Humus Can Be Further Classified

  • Humic – the soluble portion of humus.
  • Non humic – the insoluble portion called humin.

The Soluble Humic Acid Have Three Major Fractions:

  • Humic Acid – A long chain polymer of high molecular weight that is dark brown to black that is soluble in alkaline solutions.
  • Ulmic Acid – Also known as Hymatomelanic acid, is an alkaline extractable, alcohol soluble minor fraction of humic acids.
  • Fulvic Acid – A short chain polymer of low molecular weight that is yellow in color and soluble in both acid and alkali.