THE ANALYSIS OF VIRGIN SOILS. 



The data extant on this subject are rather scanty, and thus 

 far have all been obtained at the California Experiment Sta- 

 tion. 1 But they seem to be very cogent in proving that the 

 growth of crops removed from the soil causes a rapid deple- 

 tion of the nitrogen in the humus-substance, and that so soon 

 as the nitrogen-percentage in the same falls below a certain 

 point, the soil becomes " nitrogen-hungry; " so that the applica- 

 tion of nitrogenous fertilizers is needed and is very effective. 

 The data in the table below, as well as the figure of a culture 

 experiment (Xo. 52 below), illustrate this point. 



ADEQUACY A\D INADEQUACY OF NITROGEX CONTENTS OF HUMUS. 



Nos. 6 and 1679 show the usual humus- and nitrogen-percentages in 

 the "black adobe" or "prairie" soils of California. Nos. 1842 and 

 1841 represent the same soil as 1679, upon which, however, ramie and 

 ray grass had respectively been growing, without fertilization, for about 

 ten years ; showing that while the humus-content of the soil has increased, 

 the nitrogen-content of the humus has decreased 'in the case of ramie by 

 72.78%, in that of the grass by 76.78% ; reducing the land to figures 

 commonly found in the humid region. In the case of the ramie, the 

 partial return through the leaves has resulted in a higher humus-content, 



1 The Supply of Soil Nitrogen, Rep. Cal. Expt. Station, 1892-93, page 68 ; ibid., 

 1894-95, page 28 ; Tlie Recognition of Nitrogen Hungrinessin Soils, in Bull. 47, Div. 

 of Chemistry, U. S. Department of Agriculture, 1895 > Landw. Presse, No. 53, July 

 1885. See also for detailed data chapter 8, page 135. 



2 Calculated upon the true humus substance (matiere noire), not by determining 

 total (incl. unhumified) nitrogen in the soil. 



