460 



SOILS. 



by means of deep furrows, the alkali salts may be either kept 

 at a low level continuously, or if the land be at all pervious, the 

 alkali may ultimately be permanently leached out into the sub- 

 drainage by farther flooding. When the alkali has not accumu- 

 lated near the surface to any great extent, irrigation by deep 

 furrows may, alone, afford all the relief needed. 



In the case illustrated by figures 71 and 72, irrigation by 

 shallow furrows with water too strongly charged with salts 

 had so far added to the natural alkali-content of the land that 



FIG. 71. Lemon Orchard Affected by Alkali ; Before Deep Irrigation. 



the lemon trees were being defoliated. Upon the advice of the 

 California Station the deep-furrow system was adopted, and 

 within two years the results were as shown in figure 72, 

 the salts having been carried down and diluted so as to be- 

 come harmless. 



Undcrdrainagc the Final and Universal Remedy for Alkali. 

 When we underdrain an alkali soil, we adopt the very means 

 by w-hich the existence of alkali lands in the humid regions is 

 wholly prevented ; the leaching-out of the soluble salts formed 

 in soil-weathering as fast as they are formed. The long and 

 abundant experience had with underdrainage in reclaiming 



