10 



Average Proportion and Quality of the Different Forms of Nitrogen Found 



in Mixed Fertilizers. 



From the figures given in the above table under the heading "Percentage com- 

 position of total nitrogen," it appears that in those brands with a minimum guaran- 

 tee of 3 per cent of ammonia somewhat less mineral nitrogen was used than in 1926. 

 This may be due to a more general use of base goods mixtures in these grades. 

 However, a part of this apparent difference may be attributed to the employment 

 of more reliable methods, recently adopted by the Association of Official Agricul- 

 tural Chemists, for measuring the different forms of nitrogen in mixed fertilizers, 

 particularly the water soluble organic nitrogen which is easily converted to the 

 ammoniacal form. 



Fertilizer Brands Showing Inferior Insoluble Organic Nitrogen. 



Note. — Other brands showed the presence of substances containing low grade organic nitrogen, but 

 were pas.sed as the minimum nitrogen guarantee was met by the more active forms of nitrogen. 



The two products put out by the Uniform Produces Co. are somewhat different from the average mixed 

 fertilizer in that a considerable proportion of each comes from ground tobacco stems which are known to 

 have a low nitrogen activity on account of the large amount of woody fibre present. Exclusive of these 

 two products the brands showing a low activity of their water insoluble organic nitrogen were three less 

 than were noted for 1926. 



Explanation of Tables of Analyses. 



The column headed "Grade of Fertilizer" gives the minimum guarantee of 

 ammonia, available phosphoric acid and potash, alwaj^s stated in this order. To 

 convert ammonia to equivalent nitrogen, multiply hy the factor .82. 



In the table headed "Mixtures Showing a Commercial Shortage of $1 or More 

 Per Ton," under the heading "Approximate Commercial Valuation Per Ton," 

 is found the sum of the valuation of each plant food element calculated on the basis 

 of analysis and trade values adopted for 1927, which appear on a preceding page of 

 the bulletin. 



In the same table, under "Approximate Commercial Shortage Per Ton," is shown 

 the commercial valuation of the deficiencies or tests found below the guarantee, 

 per ton of fertilizer, the value of overruns being used in all cases to offset valuation 

 of shortages. 



