CHAPTER XII 

 KINDS *OF SOIL 



Soil may be classified in various ways. Thus we may 

 classify it on the basis of its origin, that is, on the basis of 

 how it was formed. Or we may classify it on the basis 

 of the materials which principally compose it and give it 

 a certain character. Both of these methods of classi- 

 fication are important. The former is much simpler, but 

 the latter is more important when it comes to considering 

 agricultural possibilities. 



As to method of origin, the kinds of soil are compara- 

 tively few, for the ways in which soil is formed are com- 

 paratively few. But as to the nature of its contents, the 

 kinds of soil are very many, for, as you have seen, soil is 

 a mixture, and the substances which enter into this mix- 

 ture are numerous and their proportions are various. 



You have learned that the various inorganic substances 

 of which soil (and rock) is composed are called min- 

 erals. Thus clay is largely composed of the mineral called 

 feldspar, while sand is chiefly made up of quartz. There 

 are many different kinds of minerals and each kind has a 

 definite nature of its own. One kind may have a very 

 beneficial effect upon the fertility of soil, while another kind, 

 if present in large quantities, may have an injurious effect; 

 or the mineral nature of the soil may make it favorable to 

 the growth of certain kinds of plants, but unfavorable to 

 the growth of other kinds. 



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