344 Reading-Course for Farmers. 



FERTILIZER QUESTIONS. 



By G. W. Cavanaugh. 



Shall we buy commercial fertilizers, and, if so, what kind? 



There are some successful farmers who do not employ commercial 

 fertilizers of any kind, while many others say that they find much 

 benefit in their use. We sometimes hear that fertilizers tend only to 

 stimulate the soil, and to leave it poorer and more exhausted ; while, 

 on the other hand, it is said that their moderate use helps to maintain 

 the fertility of many soils. In view of the conflicting opinions as to 

 the advisability of their use, and the still greater confusion as to the 

 choice of the proper kinds, it would seem that we might with profit 

 inquire into a few of the fundamental principles that underlie their 

 composition and their action in the soil. 



Why are fertilizers or manures applied to soils f 



Probably the original idea of applying manurial substances to the 

 soil was to furnish material that the roots could absorb into the circula- 

 tion of the plant and there serve as food. Of the many substances 

 used as manures, but few are directly taken up and used in the forms 

 in which they are applied. A few of the constituents of commercial 

 fertilizers are in the proper form to be used directly, while practically 

 all of the constituents of animal manures must first undergo changes 

 before they are available as plant foods. These changes in manures are 

 brought about by different agencies in the soil, some being bacterial and 

 some chemical. The products that are formed in the soil from the 

 decay of stable manure are often identical with those that are applied 

 in the commercial fertilizer. So it is possible to apply fertilizers in one 

 case and manure in another, but have the same kind of materials fur- 

 nished to the plants in either case. Usually the materials in the fertilizers 

 are more nearly ready to be used by plants than those in manures. 

 Further, the fertilizers are concentrated and compact, while the manures 

 are bulky and contain much less plant-food. To balance this deficiency 

 in amounts of plant-food, manures have some valuable properties not 

 found in fertilizers. But from the point of view of furnishing plant- 

 food, it is not a question of what each supplies, but of the cost, conven- 

 ience and the form of the materials. 



What do commercial fertilizers contain? 



The materials used in making commercial fertilizers can be divided 

 into three groups: (i) those containing some form of nitrogen; (2) 



