308 



THE PRINCIPLES OF SOIL MANAGEMENT 



and under such conditions the soluble materials accumu- 

 late in the soil, being transposed downward with the 

 percolating water and upward again with the capillary 

 rise of water during the dry period. The lower soil may 

 at one time contain considerably more soluble salt 

 than the upper soil, while at another time the upper 



Fig. 102. Bare spot, marking the first appearance of injurious quantities of 

 alkali salts in the surface layer of soil. Utah. 



soil may contain more of these salts, in which case the 

 solution in contact with plant-roots may, and often 

 does, contain so much soluble matter that vegetation 

 is injured or destroyed. This excess of soluble salts may 

 or may not have a marked alkaline reaction, but in 

 any case produce what are termed alkali soils. 



