Estimation of soil organic matter composition according to a chemical separation of litter and humic compounds

Abstract

Two chemical reactions, sulfonation and acetylation, are combined in an extraction procedure as proposed by Springer (1): sulfacetolysis, in order to separate litter and humic compounds in soil samples. The non‐soluble organic matter after sulfacetolysis is defined as humic compounds. The difference between total organic matter and humic compounds is defined as litter compounds. Some 24 selected organic matter samples and 37 soil horizons were tested to evaluate the suitability of this simple method for dissolving the original biogenic organic matter without destruction of humic compounds. The results from the chemical extraction procedure appears to be sufficiently reproducible for organic matter samples. Two to three replicates are required to establish the degree of reproducibility. Normally, organic matter samples are dissolved to about 95–100%. However, the dissolution of organic matter is not complete for wood and needles (spruce and larch). In the organic layer horizons (L, Of, Oh) and organic fertilizers (dung and slurry) the low‐molecular humic compounds are probably of similar solubility as the original litter compounds. A quantitative estimation of litter and humic compound distribution in the organic layer is not possible. In the mineral horizons sulfacetolysis is no suitable chemical instrument in order to obtain information about composition and function of soil organic matter, because the removal of soil aggregates nivalidates results.