KINDS OF SOILS— THEIR CHARACTERISTICS 57 



ences between soil and subsoil: The soil is usually darker 

 in color because it contains more organic or vegetable matter. 

 It is more easily worked and less compact than the subsoil 

 (Fig. 32). Air and moisture usually circulate in the surface 

 soil better, and its plant-food is more available. The subsoil 

 serves as a storehouse for moisture and with some plants is 

 penetrated by the roots. Its character materially affects 

 the crops grown on the soil. When the underlying rocks 

 have rotted they make the subsoil. When the subsoils have 

 rotted they are more of the nature of the surface soil. 



Fia. 33. — Teachers and students taking soU samples and studying soil, 

 (Agricultural Education,) 



Names of Soils. — In the following list the soils are ar- 

 ranged with reference to the fine and coarse particles they 

 contain: Clay, heavy clay loam, clay loam, loam, sandy 

 loam, light sandy loam, fine sand, medium sand, coarse sand, 

 gravel. 



The list omits peat and other organic matter. If humus 

 is present in these they are usually of a dark color or black. 

 Lime also darkens the color of soils in presence of vegetable 

 matter. Otherwise the color will vary a great deal. 



