CHAPTER XXIII 

 THE PRINCIPLES OF FERTILIZER PRACTICE 1 



The use of commercial fertilizers has increased so rapidly 

 within the last decade that specific knowledge is needed re- 

 garding the various materials offered for sale in order that 

 the most economical results may be attained. The greater 

 the general knowledge, both practical and theoretical, that a 

 person possesses as to the effects of the different nutrient con- 

 stituents on plant growth, the more rational will be the fer- 

 tilizer use. Fertilizer inspection and control, principles of 

 buying and home-mixing, methods of application, mixtures for 

 special crops, are a few of the many phases of economical 

 fertilizer practice. The final and vital consideration is re- 

 garding the financial return from fertilizer application. A 

 fertilizer should always pay. 



As all fertilizers exert, either directly or indirectly, a resid- 

 ual effect, the problem necessarily broadens into a study of 

 the systems of applying them to a series of crops or to a rota- 

 tion, rather than a study of the effects of one particular fer- 

 tilizer application on one particular crop. 



265. Influence of nitrogen on plant growth. 2 — Of the 

 three elements carried in an ordinary complete fertilizer, 



1 Hall, A. D., Fertilizers and Manures; New York, 1921. 

 Halligan, J. E., Soil Fertility and Fertilizers; Easton, Pa., 1912. 

 Van Slyke, L. L., Fertilizers and Crops; New York, 1912. 

 Fraps, G. S., Principles of Agricultural Chemistry; Easton, Pa., 1913. 

 "Discussions of the effects of the various elements on plants may be 

 found as follows: Eussell, E. J., Soil Conditions and Plant Growth, 

 Chapter II, pp. 19-50; London, 1912. Also, Hall, A. D., Fertilizers and 

 Manures, Chapters III, IV and VI; New York, 1921. 



471 



