266 Irrigation and Drainage 



common salt, sal soda and Glauber's salt or sodium 

 chloride, carbonate and sulphate respectively to 

 make it advisable to use them for the purposes of 

 irrigation. 



These salts are a part of the waste products of 

 soil production which ordinary vegetation is unable to 

 use with profit, and which in countries of heavy rain- 

 fall are washed out of the soil nearly as rapidly as 

 formed. Where these salts, however, do accumulate 

 to any notable extent, it is designated an alkali soil, 

 and will not produce normal crops of many of the 

 forms grown in plant husbandry. The general sub- 

 ject of alkalies and their treatment is discussed in 

 the next chapter, but we cite below the composition 

 of waters which have been regarded as safe and as 

 unsafe, without treatment, for purposes of irrigation: 



Table of safe and unsafe alkali waters* in parts per 1,000 



> Safe water - Unsafe water 



It is very unfortunate that after an analysis of a 

 sample of water has shown accurately the amounts of 

 various elements it may contain, it has not been pos- 



*Computed from Bull. 29, p. 4, Oklahoma Exp. Sta. 



