58 The Sugar-Beet in America 



kinds : those that overlie the rock from which they were 

 formed, and those formed in place largely by the accumu- 

 lation of organic matter, as in swamps. Transported soils 

 vary with the agent used in carrying the materials of which 

 they are composed. Those transported by running water 

 are called alluvial; by ice, glacial; by wind, seolian; 

 and by the ocean, marine. Each of these kinds of soils 

 has its own peculiar properties, although the composition 

 is dependent largely on the rock from which it is formed. 

 Probably more sugar-beets are raised on the alluvial soils 

 than on any other group, although good beet sections are 

 found on all the groups. 



In addition to classification according to origin, soils 

 are sometimes classified by their chemical composition, 

 by the native vegetation growing on them, by the crops 

 to which they are suited, by the size of particles com- 

 posing them, and by a number of other properties. For 

 our purpose the classification according to the crop adap- 

 tation is probably most interesting. 



SOIL AND SUBSOIL 

 (Plates VI and VII) 



For practical purposes, the soil layer is divided into 

 the surface soil and subsoil, the subsoil being the part 

 below the plowed zone. Soils vary greatly in their general 

 make-up; some are but a few inches deep and overlie 

 rock, whereas others are hundreds of feet deep and fairly 

 uniform throughout. Every gradation between these two 

 is found, including clay surface soil with gravelly subsoil 

 or gravelly surface with clay below. In arid regions the 



