MANAGEMENT OF SPECIAL SOILS 277 



of an accumulation of soluble salts of different kinds. 

 In the process of weathering through long periods of 

 time chemical changes in the soil result in the develop- 

 ment of certain chemical compounds which are soluble. 

 Some of these are useful to plants but some are harm- 

 ful. In humid climates the excess is removed by drain- 

 age through the soil. In semi-arid and arid climates an 

 accumulation of the toxic salts occurs because there is 

 insufficient rain to wash them through the soil. The 

 result is they are slowly moved to the low spots by soil 

 water as it seeks the lower levels, where, on the evapora- 

 tion of the water the salts remain as "alkali" on or near 

 the surface of the ground. 



This condition is found chiefly in countries having a 

 low precipitation, and occurs in areas where the drain- 

 age is poor and the evaporation high. It is a condition 

 that is not general in Western Canada, but is found 

 usually in small patches here and there over the whole 

 West. These patches are invariably found (1) along 

 the edges of old storage basins, (2) in low places where 

 moisture accumulates and evaporates, and (3) in 

 "springy" places below higher ground where salt im- 

 pregnated water oozes from the surface and evaporates. 

 Alkali frequently "rises" and often with serious conse- 

 quences where too much water is applied in irrigation. 



According to Shutt* the compounds known collective- 

 ly as alkali comprise chiefly sodium sulphate (Glauber's 

 salts), sodium carbonate (washing soda), sodium 

 chloride (common salt), magnesium sulphate (Epsom 

 salts), and occasionally the chlorides of calcium and 

 magnesium. 



• *In bulletin on "Alkali Soils", published by Dominion De- 

 partment of Agriculture. 



