166 Fertilizers 



monia, dried blood, superphosphates and potash com- 

 pounds should be mixed, as the manufacture of these does 

 not improve or change the quality of the constituents 

 it consists chiefly in simply grinding, mixing and bag- 

 ging. There are, however, advantages and disadvantages 

 in both methods of purchase, the chief of which are stated 

 below. 



The advantages in the purchase and use of raw materials 

 are: 1 



1. A better knowledge of the kind and quality of 

 plant-food obtained. That is, these products as a rule 

 possess characteristics which distinguish them from 

 others and from each other, and they are more likely to 

 be uniform in composition than mixtures. 



2. It enables the use of one or more of the constituents 

 as may be found necessary, thus avoiding the expense of 

 purchasing and applying those not required for the par- 

 ticular crop or soil. The farmer is also enabled to adjust 

 the forms and proportions of the various ingredients to suit 

 what he has found to answer the needs of his soil or crop. 



3. A saving in the cost of plant-food, since in their 

 concentrated form, the expenses of handling, mixing and 

 rebagging are avoided. 



The chief disadvantages are: 



1. The materials are not generally distributed among 

 dealers, and thus not so readily obtained. 



2. It is difficult to spread evenly and thinly products 

 of so concentrated a character, particularly the chemical 

 salts, which, unless great care is used, may injure by com- 

 ing in immediate contact with the roots of plants. 



3. The mechanical condition or degree of fineness is 

 less perfect than in the manufactured products. 



1 " First Principles of Agriculture." 



