38 THE SOILS AND CROPS OF THE FARM. 



ing the soil or other methods of in>proving its fertil- 

 ity. A chemical analysis, however, will not show with 

 certainty whether the substances of which the soil is 

 composed are in condition to be available as plant food. 

 Often it gives very little help to an understanding of 

 whether or no the soil is in good physical condition. 

 The chemist is able to state not only the actual and 

 relative quantity of each element found in the soil but 

 also the percentage of this which is soluble in water 

 and soluble in acids. This information helps greatly 

 in estimating the quantity of each which is probably 

 in suitable condition to be taken up and used by plants. 



Uses of the Soil. — So far as plant growth is con- 

 cerned the soil has three important uses. It furnish- 

 es a home for plants. The roots penetrate it and 

 thus are enabled to hold the plant firmly in place. It 

 also is a store-house of plant food; both of the large, 

 but relatively small quantity which is available for 

 immediate use by the plant, and the vastly greater 

 quantity which is capable of being made available. 

 It is also a laboratory in which tKe work of prepara- 

 tion of available plant food is continually going on. 

 The soil is not to be thought of as a finished product; 

 as containing simply a fixed supply of food for plants. 

 Soil formation is still going on. The forces of nature 

 are every day making available plant food in the soil 

 of materials which, heretofore, were unfitted for use 

 by plants. 



Fortunately the farmer can help the soil to be better 

 for his purpose. He can so treat it that roots may 

 more readily penetrate it, and more readily find ac- 

 cess to its store of available plant food, and he can 

 aid the "weathering" forces of nature in increasing 

 the supply of such food. 



