SOIL COMPOSITION 



TABLE 15. FERTILITY IN ILLINOIS SOILS Continued 



TIMBER UPLANDS, UNDULATING 



TIMBER UPLANDS, FLAT 



SAND, SWAMP, AND BOTTOM LANDS 



A careful study of the mass of evidence recorded in Tables 15, 

 16, and 17 clearly reveals the fact that the most important and most 

 extensive areas of Illinois soils are poor in phosphorus. The only 

 soils well supplied with phosphorus are the black clay loams, the 

 bottom lands, and the clay and peaty swamp soils. On the other 

 hand, the supply of total potassium is very great in all of the soils 

 reported upon, with the exception of the deep peat and the abnor- 

 mal marly peat, which are markedly deficient in that element. 



It should be kept in mind that small bodies of peat soil surrounded 

 by normal upland soils rich in potassium are likely to have received 

 deposits of silt or clay by overflow from time to time, and as a rule 

 they are not deficient in potassium, and shallow peat bogs with clay 



