ALKALI SOILS 307 



tiveness. It is well known that a very sandy soil responds 

 quickly to the application of soluble manures, but that 

 the effect is confined mainly to one season; while a clay 

 soil, although not so quickly responsive to fertilization, 

 shows the effect of the application much more markedly 

 the second or third year than does the sandy soil. Me- 

 chanical absorption holds the nutritive material in a very 

 readily available condition, while absorption by zeo- 

 litic bodies renders these substances somewhat less 

 readily available. There are also other reasons why the 

 sandy soil is more responsive. 



It cannot be said that there is a relation between the 

 absorptive capacity of a soil and its productiveness when 

 manured or when nearly virgin, but soil long-cultivated 

 and unmanured frequently show such a relation. King, 

 in working with eight types of soil in different portions 

 of the United States, found that those soils removing 

 the most potassium from solution gave the largest yield 

 of crop. It would not be permissible, however, to adopt 

 this test as a method for determining productiveness 

 in soils. 



VI. ALKALI SOILS 



As already explained (page 14), soils are acted upon 

 by a great variety of agencies, which gradually render 

 soluble a portion of the particles. The soluble matter 

 is taken up by the soil water, and in humid regions 

 where a large amount of water percolates through the 

 soil and passes off in the drainage, the soluble matter 

 is found only in small quantity at any time. In arid 

 regions the loss by drainage is slight or entirely wanting, 



