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This article in SSSAJ

  1. Vol. 65 No. 6, p. 1734-1735
    Received: Oct 28, 2000

    * Corresponding author(s): wrights@ba.ars.usda.gov
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A pressure cooker method to extract glomalin from soils

  1. S. F. Wright * and
  2. L. Jawson
  1. USDA-ARS-Sustainable Agricultural Systems Lab., Bldg. 001, Rm. 140, BARC-W, 10300 Baltimore Ave., Beltsville, MD 20705


Glomalin, a glycoprotein produced by arbuscular mycorrhizal fungi, is an important constituent of soil organic matter. Glomalin is insoluble in water or salt solutions commonly used in soil extractions. Solubilization of glomalin does occur in the presence of citrate at the temperature achieved by an autoclave (121°C, 103 kPa). Most soil-testing laboratories have access to all of the instruments required for glomalin analysis except an autoclave. Small (4-L) and large (14-L) pressure cookers were compared with a bench-top autoclave to test glomalin extraction from three soils using 50 mM citrate, pH 8.0 as the extracting agent. Glomalin concentrations, as measured by the Bradford protein assay, were identical for extracts from the autoclave and the 14-L pressure cooker when 103 kPa (121°C) was achieved in both vessels. The 4-L pressure cooker extracted less glomalin than the other vessels. A pressure cooker that will achieve 103 kPa is a low-cost substitute for an autoclave to extract glomalin from soils.

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Copyright © 2001. Soil Science SocietyPublished in Soil Sci. Soc. Am. J.65:1734–1735.