104 



FIRST YEAR SCIENCE 



face in large patches. The white crust usually tastes like 

 Epsom salts and the brown like salsoda. The salts form- 

 ing these patches have 

 been dissolved out of 

 the soil by the soil 

 water and left on the 

 surface when it evapo- 

 rated. 



Such substances are 

 not found in wet regions 

 because they are carried 



ALKALI SOIL. 



Few plants can grow here because of the 

 excess of alkaline salts. 



away by the water which 

 runs into the streams. 

 About the only way soil 

 of this kind can be treated to make it productive is to 

 irrigate and drain it, thus washing the salts out of the 



RECLAIMING ALKALI SOIL IN THE SAHARA. 



soil. This is just what is done by nature in well-waterecl 

 regions. Sometimes if there is not much alkali deep 

 plowing or the planting and removal of certain plants 



