It was shown in previou' publications that the acid-soluble organic nitrogen in Iowa soils as well as in Michigan peat soils is composed chiefly of acid amides, monamino acids and diamino acids. Following those publications, and also before, other papers appeared, dealing with the isolation of organic nitrogenous compounds from soils. Thus Schreiner and Shorey succeeded in isolating from various soils, in addition to a number of non-nitrogenous bodies, the diamino acids, arginine and histidine, as well as the pyrimidine derivative, cystosine and the purine bases, xanthine and hypoxanthine. Prior to that Shorey extracted from Hawaiian soils a compound which he was able to identify as a pyridine derivative, picoline carboxylic acid, and which he was inclined to believe, existed in the form of a lime salt in the soil. Among the decomposition products of Michigan peat the two monamino acids, leucine and isoleucine, were isolated and identified by Robinson who also quantitatively determined the amino nitrogen in the peat by Van Slyke's nitrous acid method.
Jodidi, S. L.
"The chemical nature of the organic nitrogen in the soil: influence of various factors on decomposition of soil organic matter,"
Research Bulletin (Iowa Agriculture and Home Economics Experiment Station): Vol. 1
, Article 1.
Available at: http://lib.dr.iastate.edu/researchbulletin/vol1/iss3/1