31 



II. EXPERIMENTAL: A STUDY OF THE NITROGEN 

 DISTRIBUTION IN DIFFERENT SOIL TYPES. 



A. The Problem. 



It has been shown in the historical study above that a number 

 of investigators have studied the organic nitrogen distribution in 

 the soil by applying either Hausmann's (1899) or Van Slyke's (1910, 

 1911) method of protein analysis. It has been demonstrated by 

 Potter and Snyder that various plots on a single soil type under 

 different fertilizer treatments gave, with Van Slyke's method, es- 

 sentially the same results. 



I have taken up the problem at this point and made a similar 

 study of the organic nitrogen distribution in different soil types in 

 an attempt to see whether the forms in which nitrogen occur 

 differ from locality to locality and from soil type to soil type. 1 

 am concerned with the problem of distribution of the organic nitro- 

 gen in the soils and soil extracts studied. 



B. The Material. 



The study was made using two peats, one muck, seven mineral 

 surface soils, and one subsoil. All were from the State of Min- 

 nesota. The origin and type names are in accordance with the 

 surveys of the Bureau of Soils of the U. S. Department of Agri- 

 culture when such surveys were available. Almost all of the soils 

 used are portions of the identical samples employed by Gortner 

 (1916 a, and 1917) in his soil studies. The samples used in this 

 study were all air dry soils. The moisture was determined by 

 heating the soils to a temperature of 100 C. for 12 hours and then 

 weighing. 



The descriptions of the soils follow : 



1. Calcareous black grass-peat. This sample was selected 

 from a large bulk sample taken to a depth of 8 inches from a 

 grass bog near the Agricultural Experiment Station Farm, St. Paul. 

 The peat was black and well decomposed. The peat was ground 

 to a powder in a ball mill before using. The air dry material con- 

 tained 6.40 per cent moisture. 



2. Sphagnum-covered peat. This sample of very strongly acid 

 peat was prepared from a large bulk sample taken from a bog on 

 the Experimental Farm near Grand Rapids. The superficial layer 

 of sphagnum and shrubs was first removed and a sample of the un- 

 derlying peat taken to a depth of 8 inches. The peat was poorly 

 decomposed. The sample was prepared by grinding to< a powder in 

 a ball mill. The air dry soil contained 5.90 per cent moisture. 



3. Acid "muck" soil. A sample of this strongly acid soil was 

 obtained from a bog about two miles from the farm of the Agri- 



