NITROGEN DISTRIBUTION IN ILLUVIAL ORGANIC MATTER

Abstract

Organic matter (O.M.) was extracted with 0.5 N NaOH under N₂, from samples of the Bh horizon of a Podzol soil. The NaOH-soluble O.M. from one sample was partitioned into "classical" humic and fulvic acids. The O.M. extracted from other samples was passed over an H-resin and purified fulvic acid" was prepared from the eluate. The O.M. retained on the resin was eluted with base. After hydrolysis a sample of the original soil the NaOH-insoluble residue and the various O.M. preparations were analyzed for amino acids, amino sugars and ammonia.Eighty percent of the amino acids in the original soil were accounted for in the NaOH-insoluble residue plus the purified fulvic acid and the NH₄OH eluate. Most of the soil amino acids were recovered in the NaOH-insoluble residue plus classical humic plus classical fulvic acid fractions. Qualitatively, the amino acid distribution in all fractions was similar to the distribution or amino acids in an "average" protein. Amounts of amino sugars were small consisting of two-thirds glucosamine and one-third galactosamine. Recoveries of amino sugars were low, possibly due to the effect of alkali.Slightly more than 50% of the soil-N was accounted for as amino acids plus NH₃ plus amino sugars. The behavior of the fraction on the exchange resin suggested that the organic C- organic N-system extracted from the soil was not uniform, and that at least portions of the ammo acids and amino sugars were either adsorbed on or physically mixed with organic matter.