30 



*Certain observed facts indicate that this figure is perhaps too low. 



In interpreting the results given in the above table it must be 

 remembered that the activity of the nitrogen in the various materials 

 as determined by the alkaline permanganate method is based upon 

 the actual amount of ammonia liberated by the various reagents and 

 heat, and anything testing around 50 or lower is regarded with sus- 

 picion. 



In case of the vegetation tests the increase in A'ield of dry matter 

 over the no nitrogen pots obtained with unzvashed dried blood is 

 placed at 80 and the increases in yield of dry matter due to the other 

 nitrogen sources (derived from the water insoluble portion of the 

 various fertilizers) are compared with it. 



A study of the table suggests the following conclusions: 



1. In case of the sheep manure and ground tobacco stems, the 

 large amount of organic matter necessary to furnish the correct 

 amount of water insoluble organic nitrogen seemed to have some in- 

 jurious effect. A much less yield of dry matter, accompanied by a 

 much reduced root growth, was obtained than on the no nitrogen pots. 



2. All of the brands of complete fertilizer showing a questionable 

 nitrogen activity by the alkaline permanganate method gave a rela- 



