352 SOILS: PROPERTIES AND MANAGEMENT 



Fig. 55. — Curves showing the absorption of P0 4 in parts to a million 

 by various soils from a solution of monocalcium phosphate, contain- 

 ing 200 parts to a million of P0 4 . The volume of the percolate is 

 used as the abscissas. 



Note. — The law which appears to govern absorption of phos- 

 phates and potash by the soil may be expressed mathematically 

 as follows: — 



dy 

 dv 



K{A - y) 



in which K is a constant, A the maximum quantity possible 

 for the soil to absorb, and y the quantity actually fixed when v, 

 volume of the solution, has percolated through. 



A short discussion of the mathematics of this law may be 

 found in the following publication : Schreiner, O., and Failyer, 

 ?t ?• ^ The Absor P tion of Phosphates and Potassium by Soils! 

 U. S. D. A., Bur. Soils, Bui. 32, pp. 23-24, 37-39. 1906 



