28 Fertilizers 



viously outlined, than definite knowledge of the true 

 principles which govern in the profitable use of com- 

 mercial fertilizers. Yet, notwithstanding all the good 

 results thus obtained, and their great practical importance 

 to agriculture, much still remains to be done, particu- 

 larly in the establishment of fundamental principles. 



While it is desirable that in a work of this kind scien- 

 tific discussions should be avoided as far as possible, and 

 the subject made as plain as is practicable to those using 

 fertilizers, it is necessary to their right use that those who 

 apply them to their land should have a very clear concep- 

 tion of the underlying principles, so far as they are known, 

 in order that they may intelligently increase their pro- 

 duction, and thus reap a profit. Definite knowledge is 

 an important factor in determining their profitable use. 



THE NEED OF ARTIFICIAL FERTILIZERS 



The considerations in the previous chapter explained 

 in part, and in a broad, general way, the necessity for the 

 use of commercial fertilizers. The conditions of farming 

 in this country have greatly changed in the past thirty 

 years, and these changes have, perhaps, a still more 

 important bearing in showing the need of imported fer- 

 tility than the conditions already discussed. The first 

 direction in which important changes have taken place 

 is in the increased cost of farm labor and in the relatively 

 low prices now received for the staple crops, the cereal 

 grains, cotton and tobacco. 



The cost of production to a unit of income is increased. 



The cost of labor is increased because proportion- 

 ately higher wages are now paid, and because the labor 



