13 



1 Dried blood 3 A to 4 C inclusive received their nitrogen from unwashed material. 



2 Composite made by equal weights of 14 brands and 48 samples. 

 ' Composite made by equal weights of 16 brands and 48 samples. 



Note. — The insoluble nitrogen activities, as taken from the 1922 inspection data on the above mentioned 

 two grades of mixed fertilizer, as determined by the alkaline permanganate method, varied from 46 to 54 per cent. 

 The activities given in the table were determined on the washed and dried residues prepared for this vegeta- 

 tion test. 



A study of the table suggests the following conclusions: 



1. Both grades of fertilizer which, upon individual analysis of the thirty brands of 

 which the two grades were composed, showed water insoluble nitrogen activities 

 ranging from 46 to 54 per cent, actually showed an average nitrogen availability, 

 measured by their crop producing power, of less than 24 per cent, the 2-8-2 averag- 

 ing 26.90 and the 2-8-3, 20.53. 



2. On these thirty particular brands, it apparently would have worked no injustice 

 upon the manufacturer had the passing mark or standard been set at 55 instead of 

 50 for the alkaline permanganate method. Had the standard been 55, the water in- 

 soluble nitrogen in each case would have been graded "inferior," a fact which is cer- 

 tainly borne out in this experiment by their actual crop producing power as com-' 

 pared with dried blood. 



3. The neutral permanganate method was quite as effective as the alkaline method 

 in grading the nitrogen supplied by the blood and the two grades of mixed fertilizer, 

 although the latter method gave insoluble nitrogen activities which more nearly cor- 

 respond to the availabilities as established by the vegetation test. 



4. Judging from this experiment, there is ample justification for raising the standard 

 of the alkaline method to 55. 



Nitrogen in Mixed Fertilizers. 



The following graphs have been prepared to show the average make-up and quality 

 of the nitrogen found in mixed commercial fertilizers sold in Massachusetts during 

 the season. In this study the fertilizers were divided into five groups according to 

 the guarantee of ammonia, as follows: brands with less than 2 per cent ammonia 

 (30 samples); between 2 and 3 per cent (170 samples); between 3 and 4 per cent 



