Leaching 
The rate diffusion of herbicides may be calculated from Fick's 

diffusion equation: 
(] 
m= D°q Sos 
m = mass of herbicide 
D = diffusion coefficient 
q = surface of herbicide 
Co= solubility of herbicide in water 
C'= final concentration of dissolved herbicide 
6 = thickness of diffusion layer 
t = time in seconds 
The reader is also referred to a discussion of 'Leaching of 
Pesticides from Granular Formulations" by Furmidge, Hill and Osgerby (513). 
487 
