82 



SCIENCE AND SOIL 



TABLE 15. FERTILITY IN ILLINOIS SOILS 

 Average Pounds per Acre in 2 Million Pounds of Surface Soil (o-6f Inches) l 



PRAIRIE LANDS, UNDULATING 



PRAIRIE LANDS, FLAT 



TIMBER UPLANDS, ROLLING OR HILLY 



1 The numbers given in Table 15 represent the total amount contained in 2 

 million pounds of the surface soil on the dry basis, with the exception of deep peat 

 swamp soil, for which the amounts in i million pounds are used, because its spe- 

 cific gravity is only one half that of ordinary soil, and of sand soil for which 2 \ million 

 pounds are used, because it is about one fourth heavier than ordinary soil. 



