INTRODUCTION, 



TN YEARS gone by the farmer had little use for 

 agricultural chemistry. The virgin soil was so 

 well supplied with all the elements needed for plant 

 nutrition that the only thing for him to do was to 

 plant, and till, and reap a bountiful harvest. 



Times and conditions have changed. The land 

 does not respond any more quite so promptly to 

 merely scratching its back with plow and harrow. 

 It has grown weary and hungry. It now looks for 

 food, and coaxing, and petting, before it can be 

 made to smile with flowers, fruits, vegetables and 

 grains. 



The farming of our fathers was based upon the 

 almost unlimited generosity of nature, and the 

 original wealth of the soil. The farming of the 

 present day is changing more and more to a process 

 of manufacturing crops out of raw materials large- 

 ly supplied by man. The soil only serves us as a 

 medium and implement of manufacture. 



We find ourselves burdened with duties not im- 



