Studies on the Carbon and Nitrogen Cycles in the Soil. VIII. The Nature of the Organic Nitrogen Compounds of the Soil: “Non-Humic” Nitrogen

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Abstract
1. From an examination of the compounds remaining in solution when humic matter is removed from alkaline extracts of Rothamsted soils by acidification, it is concluded that 30–40 per cent. of the nonhumic nitrogen is present in the form of peptides (proteoses, peptones and polypeptides), with 5 per cent, of free amino nitrogen and 12 per cent. of ammonia. The peptides are largely colloidal, and precipitated by basic lead acetate and by phosphotungstic acid. The remaining 40–50 per cent. of the non-humic nitrogen is mainly precipitated by basic lead acetate and is mainly non-basic.