14 NATURE AND PROPERTIES OF SOILS 



Table I 



Comparison of the Chemical Composition op American 

 Surface Soils with that of the Lithosphere. 



(a) Average of 22 soils only, (b) Average of 13 soils only, 

 (c) Calculated from the organic matter. 



9. The soil and the plant. — As the soil considered agri- 

 culturally is essentially a medium for crop production, its 

 rational study has to do with the consideration and applica- 

 tion of such scientific principles as have a bearing on prac- 

 tical soil management. Anything that makes clearer the 

 relationships between soil and crop has a proper place. Un- 

 less a scientific phase has a crop relation, either directly or 

 indirectly, it need receive but scant consideration. The com- 

 position of the soil, its chemical and biological changes, its 

 physical peculiarities and its reaction to certain additions 

 must receive especial attention. More knowledge of the soil 



1 Soils contain many other elements, although in small amounts, such 

 as chlorine, barium, caesium, chromium, lithium, molybdium, rubidium, 

 vanadium, etc. Eobinson, W. O., The Inorganic Constituents of Some 

 Important American Soils; U. S. Dept. Agr., Bui. 122. Aug., 1914. 



