306 LUTHER BURBANK 



few of them knew the reasons for any of the 

 operations. 



In order to understand how to select soils and 

 how to secure the best results from them, one 

 must know the underlying principles of produc- 

 tive ability of soils and the methods used by 

 plants to secure food from them. 



Farming is now considered a manufacturing 

 process. As a matter of fact, a farmer uses more 

 kinds of raw materials and produces more kinds 

 of finished products than any other manufac- 

 turer. It is just as necessary that he select his 

 raw[ materials with extreme care as it is that the 

 manufacturer of machinery select the most 

 durable kinds of wood and the strongest kinds of 

 metal. 



Farmers have sometimes been criticized for 

 not using more fertilizers, but this is not always a 

 just criticism. Fertilizers are valuable in some 

 cases, but often a better physical condition of the 

 soil would make it possible for the plants to se- 

 cure enough food materials to increase the yield 

 materially without adding fertilizers, and too 

 often the crop produced would not repay for 

 the purchase of fertilizers. 



Profit in crops depends upon the location of 

 the crops grown, the use to which the crops are 

 put, and the cost of fertilizing when fertilizing is 



