SOIL COMPOSITION 77 



SOILS OF THE CENTRAL STATES 



The accompanying soil map of Illinois and Tables 15, 16, and 17 

 serve to illustrate in a very trustworthy manner both the uniform- 

 ity and variation that may be expected among the most important 

 soil types in the North Central States. This detailed information 

 from Illinois applies with almost equal value to similar soils in 

 many other states. With a north and south extension of nearly 

 400 miles in the center of the greatest agricultural region of the 

 United States, Illinois occupies a unique position. In latitude it 

 reaches almost from Vermont to North Carolina, Cairo being farther 

 south than Richmond, and Beloit farther north than Boston. 

 Cairo is within 35 miles of the Tennessee line, and 150 miles south 

 of Covington, Kentucky. From Cairo to Mobile on the Gulf is 

 no farther than from Beloit to the 49th parallel, which marks the 

 northern boundary of the United States. The soils of Illinois are 

 in large measure representative of the soils of the wheat belt, of 

 the corn belt, and, in part, of the cotton belt. Cotton growing has 

 been a commercial success in southern Illinois, and much spring 

 wheat has been produced in the north end of the state, while central 

 Illinois is the heart of the corn belt. 



Fourteen great soil areas are recognized in Illinois, including the 

 extensive unglaciated regions in the southern and northwestern 

 parts of the state, the lower, middle, and upper Illinoisan glacia- 

 tions, the pre-Iowan and lowan glaciations, the early and late 

 Wisconsin glaciations, with numerous moraines and intermorainal 

 tracts, the deep loess deposits, and the early and late swamp and 

 sand areas, and extensive and widely distributed bottom lands and 

 terraces. 



As already explained, the material called loess constitutes the 

 chief basis for nearly all of the upland soils of central United States. 

 The principal differences among these soils of loessial origin are due 

 to difference in age, topography, and climatic conditions. Some 

 additional or subsequent differences have been brought about by 

 variation in native vegetation and in systems of farming. 



Prairie and timber soils. The upland soils may be divided into 

 prairie soils and timber soils, according to the character of the 

 original vegetation; and with similar topography the difference in 



