Nine less brands showed serious commercial shortages than for the previous 

 season. 



Mixing Efficiency. 



Assuming that the tonnage sold, minimum guarantees made, and results of 

 inspection, give a fair representation of the composition of the tonnage of each 

 grade counted, the following table gives the average margin of overruns over the 

 minimum guarantee as furnished by each manufacturer having four or more brands 

 registered and sampled. 



Mixing Efficiency Table. 



Note — Figures for the Wilcox Fertilizer Co. were not computed as the tonnage report had not been 

 received from this firm. 



The above table shows that 25 of the 29 manufacturers listed had an overrun 

 in all three elements; 28 showed an overrun and 1 a shortage in nitrogen; 27 

 s'^howed an overrun and 2 a shortage in both available phosphoric acid and potash. 

 The average marginal overrun of plant food allowed by the manufacturers in 1927 

 was more liberal than during the previous season: .15 per cent more for nitrogen, 

 .14 per cent more for available phosphoric acid, and .12 per cent more for potash. 



Nitrogen in Mixed Fertilizers. 



The average total nitrogen of all of the mixed complete fertilizers analyzed was 

 3.98 per cent, which was .32 per cent higher than for 1926. The nitrogen derived 

 from mineral and organic sources was 2.47 per cent and 1.51 per cent, respectively, 

 which was about the same proportion as for 1926. The average total nitrogen 

 showed an activity of 79 per cent, and the water insoluble nitrogen an activity of 

 55 per cent, determined by the alkaline permanganate method. These latter 

 figures do not include the brands used for tobacco: in these brands the organic 

 portion of the nitrogen is relatively high and derived largely from vegetable sources. 



The activity of the water insoluble nitrogen in this class of products is measured 

 by the neutral permanganate method, the passing mark of which is 80 instead of 

 50 as in the case of the alkaline method. 



