79 



tive manures, and contain one, two or all three of the es- 

 sential fertilizing ingredients previously referred to. 



The proportions in which these ingredients are supplied, 

 and the forms in which they occur in commercial manures 

 exhibit considerable variations, and are largely dependent 

 upon the manufacturerer's ideas as to the requirements of 

 any particular crop or soil. These commercial manures 

 are commonly divided into two classes, viz: "complete" and 

 "partial manures," the former containing, as the term im- 

 plies, all three of the chief essential fertilizing constituents 

 of value (phosphoric acid, nitrogen and potash) while the 

 latter contain only one or two of these ingredients. 



The former are designed for general use and for direct 

 application to soils and crops, frequently, of widely differ- 

 ent characters ; the latter are either to be employed as in- 

 gredients of home made mixed manures or composts, or 

 else to supply some particular element, in a concentrated 

 form, to some specific crop. 



Partial manures may be advantageously considered un- 

 der the following subdivisions : 



(1.) Phosphoric acid manures. 



(2.) Nitrogen manures. 



(3.) Potash manures. 



(4.) Manures containing phosphoric acid and potash. 



(5.) Manures containing phosphoric acid and nitrogen. 



(6.) Manures containing potash and nitrogen. 



The following matter with reference to the composition, 

 characteristics and sources of commercial manures is repro- 

 duced from the fertilizer bulletin published by the Depart- 

 ment of Agriculture in August 1894 : 



(1) PHOSPHOKIC ACID MANUR.^S. 



Formerly the chief source of supply of this valuable fer- 

 tilizing element was bones, either raw or chemically treated, 

 and while "bone meal" and raw bone superphosphates still 

 have a large consumption, by far the largest proportion of 

 phosphoric acid for artificial fertilizers, is derived from phos- 



