298 



THE PRINCIPLES OF SOIL MANAGEMENT 



some calcium chloride or sodium chloride, or both, and 

 some potassium chloride. The more dilute the solution, 

 the larger the proportion retained. Peters treated 100 

 grams of soil with 250 c.c. of a solution of potassium 

 salts, and found that the potassium of different salts was 

 retained in different proportions, and that the stronger 

 solutions lost relatively less than the weaker. 



The same bases are not always absorbed to the same 

 extent by different soils; one soil may have a greater 

 absorptive power for potassium, while another may retain 

 more ammonia. They seem to be interchangeable, as any 

 absorbed base may be released by another in solution. 



159. Time required for absorption. The amount of 

 absorption depends upon the time of contact between the 

 soil and the solution. While a large part of the dis- 

 solved base is taken up in a short time after being in 

 contact with the soil, the maximum absorption is only 

 effected after considerable time. Ammonia, according 

 to Way, reaches its maximum absorption in half an 

 hour, while Henneberg & Stohmann found that phos- 

 phorus required twenty-four hours to reach the same 

 degree of absorption. 



