Glomalin is a "procedurally-defined" fraction of soil organic matter obtained through soil extraction with citrate solution at high pH using microwave or heat energy. Organic matter recovered from soil in this way has been reputed to be derived from, and thus was named for, arbuscular mycorrhizal (AM) fungi (Glomus). The gene product of glomus sp. recovered by this technigue makes up just a portion of the organic matter. Glomalin recovered in the extract is commonly estimated using the Bradford protein or enzyme-linked immunosorbent (ELISA) assays. The Bradford assay is not specific for the glycoprotein produced by Glomus whereas ELISA is somewhat more specific. Other glycoproteins, associated carbohydrates and humic substances are recovered using this extraction procedure. As is true for other measures of soil organic matter, including humic acids, glomalin is positively related to soil aggregation and can be enhanced by using soil improving practices. This fraction has been found to be positively related to organic matter inputs to soil but not to AM fungal abundance.

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