200 



SOILS AND FERTILIZERS 



PHOSPHORIC ACID 



P 2 5 



PER ACRE 

 LBS. 



Wheat, 20 bu. : . 



Straw, 2000 Ibs. . . 



Total . . . 



Barley, 40 bu. . . 



Straw, 3000 Ibs. . . 



Total . . . 



Oats, 50 bu. . . . 



Straw, 3000 Ibs. . . 



Total . . . 



Corn, 65 bu. . . . 



Stalks, 4000 Ibs. . . 



Total . . . 



Peas, 3500 Ibs. . . 

 Red clover, 4000 Ibs. 



Potatoes, 150 bu. . 



Flax, 15 bu. . . . 



Straw, 1800 Ibs. . . 



Total 



12.5 

 7-5 



20.0 

 15 



_5 



20 



12 



6 



7s 



18 

 _4 



22 



25 

 28 



20 



J 



18 



227. Amount and Source of Phosphoric Acid in Soils. 



To meet the demand of growing crops for about 25 

 pounds of phosphoric acid per acre, there are present in 

 soils from 0.03 to 0.25 'per cent. This is equivalent to 

 from 1000 pounds and less to 9000 pounds per acre, of 

 which, however, only a fraction is available as plant food at 



