QUANTITATIVE RELATIONSHIPS OF 

 CARBON, PHOSPHORUS AND 

 NITROGEN IN SOILS* 



BY ROBERT STEWART 



(A) HISTORICAL RfiSUMfi 



The literature on carbon, nitrogen and phosphorus in soils^ is 

 voluminous. The resume given herewith by no means attempts to 

 include all that pertains to these elements in the soil, but it is con- 

 fidently believed that it fairly represents the literature pertaining 

 to this particular phase of the subject. 



i. CARBON IN SOILS 



Carbon may exist in soils as inorganic and organic carbon. The 

 agricultural value of organic carbon, or organic matter, of soils 

 has long been recognized by the practical husbandman, and the 

 scientific man early recognized its value when the applications of 

 science were made to agricultural problems. 



Mulder (i) in 1844, made an elaborate study of the organic 

 matter of the soil, and seems to have been the first one to suggest 

 that it consisted of other elements than carbon, hydrogen and 

 oxygen. He separated the organic matter into various supposed 

 pure organic compounds of an acid nature, which were analyzed 

 and studied by the usual organic method. 



Wolff (2) determined the organic matter of the soil by calcu- 

 lation, by use of the factors 1.724 or 0.471 : he multiplied the or- 

 ganic carbon by the former factor, or the total organic carbon 

 dioxid by the latter. The factors were derived from the concep- 

 tion that "humus" contained 58 percent carbon. 



Detmer (9) attempted to isolate "pure" humic acid from the 

 soil and to study its properties. He obtained a fairly pure product 

 which he studied and submitted to analysis. 



A little later Grandeau (10) developed his well known method 

 for determining the matiere noire of soils, which he regarded as 

 of great importance. He stated that soils owed their color and 



*Submitted to the Faculty of the Graduate School of the University of Illinois 'in partial 

 fulfillment of the requirements for the degree of Doctor of Philosophy, June, 1909. 



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