270 Irrigation and Drainage 



sea, where there are low -lying lauds periodically in- 

 undated by high tides, white deposits are again left 

 when the surface becomes dry, and are injurious to 

 cultivated crops when they have accumulated to suf- 

 ficient strength, and these are sometimes spoken of 

 as "alkali lands." 



In the wide application of the term, then, "alkali 

 lands" are those upon which soluble salts have ac- 

 cumulated in sufficient quantity, through evaporation 

 and capillarity, to attract attention by their usually 

 white appearance and their injurious effects upon 

 vegetation . 



Hilgard states that "alkali lands must be pointedly 

 distinguished from the salt lands of the sea margins 

 or marshes, from which they differ both in their 

 origin and essential nature;" and, in the sense he 

 wishes to be understood, the distinction should be 

 made ; but there are important advantages, as will 

 appear, in treating them all under one head. 



CAUSE OF INJURIES BY ALKALIES 



When the soil water about the roots of plants or 

 germinating seeds becomes sufficiently strong with 

 salts in solution, the osmotic pressure is so modified 

 that a discharge of the cell contents into the soil takes 

 place to such an extent as to produce what is equiva- 

 lent to wilting. The cells are not maintained suffi- 

 ciently turgid to permit normal growth, or they may 

 have the pressure so much lowered as to cause death. 

 The case is * like placing the plump strawberry or 



