ALKALI IS INJURIOUS 



259 



become unproduc- 

 tive. Other lands in 

 the arid and semi- 

 arid sections are so 

 saturated with alkali 

 salts naturally that 

 they are barren, and 

 are not fit lands for 

 irrigation. The per- 

 manent remedy con- 

 sists in removing the 

 injurious salts by 

 means of tile drains, 

 scraping it off, and by 

 flooding. The grow- 

 ing of alkali-resisting 

 crops, such as salt 

 grass, has been sug- 

 gested as a means 

 of avoiding injury. 

 Sweet clover grows 

 well when alkali is 

 quite abundant. As 

 a general rule, deep 

 rooted plants can 

 tolerate alkali soils 

 better than those 

 that are shallow 

 rooted. Land-plaster 

 is sometimes used 

 to neutralize black 

 alkali, the most 

 harmful of the alkali 

 salts (sodium car- 

 bonate). Retarding 

 evaporation by 

 mulching and shad- 

 ing, and deep plow- 

 ing may retard the 

 accumulation of salts 

 at the surface. 



FIG. 164. Club-root of cabbage, showing swollen and dis- 

 torted roots and.undeveloped head. (Vermont Station.) 



