126 



THE PRINCIPLES OF SOIL MANAGEMENT 



Wabash silt loam is the much-prized deep, dark silt 

 loam of the stream bottoms in the North Central states. 

 It is a close competitor of the Miami black clay in the 



production of corn 

 and grass. 



The proportion of 

 organic matter is the 

 chief distinction be- 

 tween soils and sub- 

 soils. It will be noted 

 from the table that 

 in all of the humid 

 sections this differ- 

 ence is very marked, 

 and agrees well with 

 the color differences 

 generally observed. 

 But in the arid re- 

 gions this distinction 

 between soil and sub- 

 soil is not so obvious. 

 The difference in or- 

 ganic content is even 

 less marked than the 

 figures indicate, for the reason that several of those 

 for the soil extend to a depth of two feet or more and 

 those of the subsoil extend often to six feet. 



55. Some physical properties. The physical prop- 

 erties of the organic constituents of the soil are different 

 in value from those of the mineral constituents. Though 

 usually present in small amounts their properties 



Fig. 38. A soil of loamy texture in good tilth. 



