Official Inspections 93. 67 



information beyond that obtained at a glance. It is particular- 

 ly worth while to know the kind, character and amounts of the 

 nitrogen. 



Phosphoric Acid. In fertilizers phosphoric acid is usually 

 present in three forms, water soluble, weak organic acid soluble, 

 and insoluble. The water soluble and weak organic acid soluble 

 together make up the available phosphoric acid. Other than 

 that the water soluble is a little better distributed in the soil 

 there is no choice from the standpoint of plant growth between 

 the water soluble and the weak organic acid soluble. For very 

 soon after its introduction into the soil the water soluble is 

 changed to organic acid soluble form. 



The insoluble phosphoric acid is readily found by subtract- 

 ing the available phosphoric acid found from the total found. 

 Thus in sample A above the insoluble phosphoric acid is .74 

 (10.72 less 9.98) per cent. Such small amounts as 1 per cent 

 of insoluble phosphoric acid in the amounts in which fertilizers 

 are applied per acre have no appreciable agricultural value. Its 

 declaration serves no very useful purpose. But as in the meth- 

 ods of analysis in order to know the available, the total phos- 

 phoric acid must be determined, and from the fact that in the 

 days in which financial values of fertilizers were calculated 

 credit was given for the insoluble phosphoric acid, it continues 

 to appear in the fertilizer laws and consequently in the reports. 

 It is really a column that contains little information of value 

 to the user of commercial fertilizers. 



Potash. This column of potash found gives the amount of 

 water soluble potash the goods carry. Until Germany declared 

 war on civilization practically all of the world's potash was de- 

 rived from mines in the German Empire. It was mostly in the 

 form of muriate or sulphate and was of reasonable purity. With 

 the war shutting off all sources of imported potash the United 

 States had to look within its own borders for potash for muni- 

 tion and for growing crops. This lead to the opening up of 

 new, untried, and very unusual sources which because of the 

 price that could be had were developed as under old conditions 

 they could not. Up to 191 6 about all that one had to think of 

 relative to potash was how the analysis compared with the 

 guaranty. For with the exception of tobacco and a few other 

 special crops there seemed to be little to choose between muri- 



