COMMERCIAL FERTILIZERS 77 



izers. The relative rate of availability of a constituent in one carrier as 

 compared with its availability in another is the point at issue. This 

 determines the advantage or disadvantage of purchasing one or the other 

 at ruling market prices. As yet definite relative values for all fertilizing 

 materials have not been worked out. Furthermore, it is recognized that 

 they never can be worked out for conditions in general, because of the 

 wide latitude in the conditions which affect availability. This problem 

 is attacked by what is known as vegetative tests; that is, tests which 

 show the actual amounts of the constituents taken up from various sub- 

 stances by plants when grown under identical conditions. With nitrog- 

 enous fertilizers, for example, the results so far obtained indicate that 

 when nitrogen in nitrate of soda is rated at 100 per cent, that in blood 

 and cottonseed meal are equal to about 70 per cent, that in dried and 

 ground fish and hoof meal at 65 per cent, that in bone and tankage at 60 

 per cent, and for leather and wool waste may range from as low as 2 per 

 cent to as high as 30 per cent. 



The Composition of Fertilizers. — In the purchase of mixed fertilizers 

 consumers should demand that they be accompanied by a guarantee. 

 This is essential because the purchaser is unable to determine the kind 

 and proportion of the different materials entering into the mixture, either 

 by its appearance, weight or smell. 



At present most of the states have on their statutes, laws regulating 

 the manufacture and sale of commercial fertilizers. These require that 

 the composition be plainly stated on the original packages of fertilizer. 

 The law also provides for the analysis of samples collected at any point 

 and the publication of these analyses either by the state departments or 

 by the state experiment stations. Such publications set forth the name 

 of the brand of fertilizer and the name of the dealer or manufacturer, 

 together with a statement of the analysis as given by the manufacturer 

 as compared with that found by the official analysis. Infringements of 

 the law relative to its provisions call for punishment generally by fines. 

 Under such a system of regulation there is now little danger of the farmer 

 being cheated in the purchase of fertilizers so far as their composition is 

 concerned. 



What Analyses of Fertilizers Show. — The difference between a good 

 and inferior fertilizer is shown by a chemical analysis, providing it is 

 carried far enough to show both the amount and form of the constituents 

 present. An analysis of a fertilizer which shows that the nitrogen is 

 present chiefly as nitrates, the phosphorus as acid phosphate and the 

 potash as muriate of potash at once stamps such a fertilizer as being 

 made up of high-grade materials. On the other hand, if the nitrogen is 

 found largely in an organic form and the phosphorus in an insoluble form, 

 it is evident that the materials used are low-grade forms, and result in 

 a slow-acting and sometimes unsatisfactory fertilizer. 



Commercial vs. Agricultural Value of Manures. — Agricultural value 



