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Extraction of Soil Organic Matter

Jul 23,2013

The properties of soil organic matter, and especially humic substances, can be studied only in free state, that is, when freed of inorganic soil components. Therefore, the first task of the researcher is to separate organic matter from the inorganic matrix of sand, silt, and clay.

A variety of techniques have been employed, depending upon the nature of the material to be examined. Thus nonpolar compounds like fats, waxes, resins, etc. can be extracted with such organic solvents as hexane, ether, alcohol-benzene mixtures, and others. Hydrolysis prosedures have been used for isolating individual monomers, such as amino acids and sugars.

The ideal extraction method is one which meets the following objectives:

· the method leads to the isolation of unaltered material

· the extracted humic substances are free of inorganic contaminants, such as clay and polyvalent cations

· extraction is complete, thereby insuring representation of fractions from the entire molecular-weight range

· the method is universally applicable to all soils