PURCHASE AND USE OF FERTILIZERS 343 



is even to some extent true of the easily soluble fertilizers, like 

 nitrate of soda, for which the soil has little power of fixation, but 

 still more so for the less soluble acid phosphates. In the case of 

 organic nitrogenous materials, the particles become centers for 

 the production of ammonia and nitrates, which may eventually be 

 taken up by the rootlets as fast as they are formed. The well 

 known fact that moderate applications of fertilizer are more 

 effective when applied in the vicinity of the plant or seed than 

 when applied broadcast, is evidence that the plant food does not 

 become rapidly and uniformly distributed through the soil mass. 



The Practice of Fertilization. 1 There is such a variation in the 

 needs of crops and soils for fertilizers, in the effect of climatic 

 conditions, and previous treatment, upon their behavior towards 

 fertilizers, that it is impossible to lay down specific rules for fer- 

 tilization. The fertilizer which produces heavy yields of potatoes 

 in the North, would not necessarily be suitable for the warmer 

 climate, lighter yields, and earliness, associated with the same 

 crop in the South. Onions grown on the sandy soils of Long 

 Island, New York, require different treatment from those grown 

 in the warmer climate and much richer soils under irrigation at 

 Laredo, Texas. Applications suited to crops grown under favor- 

 able conditions of moisture may be unsuited to crops which may 

 have to endure a period of drouth or mature on a moderate 

 amount of moisture. The best that can be done is to lay down 

 general principles, and to give the applications which have proved 

 successful under certain stated conditions. The individual farmer 

 must study his own conditions, with the help of his State Experi- 

 ment Station, and learn by his own experience the most profitable 

 applications for him to make. A few brief notes are made below 

 on fertilizers for various crops. 



Field Crops. Rotation of crops, including legumes, to be 

 turned under or fed and the manure saved, is essential to mainten- 

 ance of fertility for ordinary field crops. Only in this way can 

 nitrogen be secured cheap enough. Phosphates and potash may 

 1 See Voorhees, Fertilizers ; Van Slyke, Soils and Fertilizers ; Bulletins 

 of Bureau of Soils and of State Experiment Stations. 



