25 



form of nitrogen. On open porous sandy soils, deficient in organic 

 matter and humus, it would probably not be good economy to use 

 too large a proportion of mineral nitrogen, as a serious loss from leach- 

 ing would be likely to occur. 



In the complete commercial fertilizers analyzed, it was found 

 that in the low grades 37.5% and in the high and medium grades 

 47.3% of the total nitrogen was from mineral sources. 



The quality of the organic nitrogen in the various grades of fer- 

 tilizer may be indicated from the following data: 



In the low grade fertilizers 62.5% of the total nitrogen was 

 present inorganic form. In the high and medium grade fertilizers 

 52.7% of the total nitrogen was from organic sources. Twenty-six 

 cases were found in which there is reason to question the quality of 

 the organic nitrogen; thirteen, or 50% of the whole number, were 

 from low grade fertilizers, (that is, valuing commercially less than 

 $18.00 per ton.) Five out of the 26 were from medium grade and 8 

 were from high grade goods. The above facts indicate that, as a 

 general rule, the organic nitrogen in the cheaper grades of fertilizer 

 is not derived from as high grade sources as in the better grades. 



The organic nitrogen has been reported in the present bulletin 

 in the same manner as heretofore, namely: — Water soluble organic 

 nitrogen, active water insoluble organic nitrogen and inactive water in- 

 soluble organic nitrogen. The data furnished by each detailed analy- 

 sis is considered sufficient to enable anyone to readily detect cases in 

 which at least a portion of the organic nitrogen has been derived 

 from inferior sources. 



It is our purpose, during the winter, to test, by vegetation ex- 

 periments in pots, the actual availability of the water insoluble nitro- 

 gen in those samples which hdve shown a low activity by the labo- 

 ratory method. 



As has been pointed out in a previous bulletin, in judging the 

 quality of the organic nitrogen in any fertilizer, three things should 

 be considered: — 



1. The proportion of the organic nitrogen soluble in water. 



2. The percentage activity of the water insoluble organic 

 nitrogen. 



3. The excess of nitrogen which has been furnished over the 

 guarantee. Wherever a considerable quantity of organic nitro- 

 gen is present it may be said, in general, that cases should be viewed 

 with suspicion which show the following characteristics: — 



(a) Small amount of water soluble organic nitrogen. 



(b) The inactive water insoluble organic nitrogen equaling 

 or exceeding the active water insoluble organic nitrogen. 



(c) The total nitrogen found not much in excess of guarantee. 



