104 A YEAR IN AGRICULTURE 



ten residual soils from ten different geological formations in 

 the eastern part of the United States, two million pounds of 

 surface soil were found to contain: 



Potassium 37,860 pounds 



Magnesium 14,080 



Calcium 1,810 



Phosphorus 1,100 



He further states that in the common type of the great soil 

 area of Illinois' corn belt, two million pounds of the sur- 

 face soil contain as an average : 



Potassium 36,250 pounds 



Magnesium 8,790 



Calcium , 11,450 



Phosphorus 1,190 



In the older clay silt loam soil of southern Illinois, he states 

 the content for the same number of pounds to be: 



Pptassium 24,940 pounds 



Magnesium 4,680 " 



Calcium 3,420 



Phosphorus 840 " 



It will be seen by these figures that these soils are rich in 

 potassium and poor in phosphorus. These figures bear some 

 relation to the composition of the earth's crust, which con- 

 tains in two million pounds, 49,200 pounds of potassium and 

 2,200 pounds of phosphorus. 



Plant-food required for crop growth. Quotations from 

 Bulletin No. 123 of the Illinois Experiment Station give the 

 following interesting data : 



