MOYKMENTS OF SALTS IN SOILS. 



89 



narrow a margin that the movements can be measured by the 

 methods only with great difficulty. 



There are given in the next table the mean amount of phos- 

 phates recovered from the) eight soil types after the capillary 

 periods of 20 and 50 days. 



Mean amounts of phosphoric acid (HPO 4 ) recovered from different 

 sections of soil columns after capillary movement has taken place. 



From these data, there appear to be real differences between 

 the amounts of phosphoric acid recovered at the close of the 

 two capillary periods, but they are very small. Larger mean 

 values are, also, found for the phosphoric acid after than be- 

 fore the treatment, as indeed must be expected unless complete 

 absorption or precipitation occurs. 



The probable relation of these two sets of data may be more 

 clearly seen from the graphic representation, Fig. 4-, p. 90. 

 From this it will be seen that both curves, where they represent 

 the conditions in the lower portions of the soil columns, show a 

 tendency to develop the same features possessed by the potash 

 curves in Fig. 3, p. 83. This is especially marked in the 50 

 day curve and the differences shown may be interpreted as in- 

 dicating that, after a sufficient amount of movement, the form 

 of the potash curve would be reproduced. In other words, 

 there is a strong absorption of the phosphoric acid as it enters, 

 the soil but slowly it is moved forward by the water, thus re- 

 ducing the amounts between and increasing that above, which 



