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This article in SSSAJ

  1. Vol. 24 No. 6, p. 472-477
    Received: Mar 8, 1960
    Accepted: Apr 18, 1960

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Chemical Nature of the Nitrogen in the Fulvic Fraction of Soil Organic Matter1

  1. F. J. Stevenson2



A study of the forms of N in the fulvic fraction of soil organic matter showed that about one-half of the N occurred in compounds which deaminated readily by acid and base hydrolysis. About one-fourth of the N existed in amino acids; about one-tenth in amino sugars.

Through a modification of Forsyth's selective adsorption technique, the fulvic extract from a Brunizem soil was fractionated into several components, a number of which were pigmented. All of the components contained amino acids; several contained amino sugars. The N compounds which formed NH3 by hydrolysis occurred primarily in association with pigments. A physicochemical study of the colloids of fulvic extracts showed that the colloids were heterogeneous with respect to both charge and particle size.

A consideration of possible mechanisms for the formation of fulvic pigments in soil prompted the author to postulate that the pigments originated through the condensation of carbonyl compounds with amino derivatives, by mechanisms similar to those proposed for browning processes in natural products.

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