118 BOARD OF AGRICULTURE. [Pub. Doc. 



""words, a pound of nitrogen from nitrate of soda or a pound 

 of nitrogen from sulphate of ammonia lias a value which does 

 not depend upon the original source of supply, — one pound 

 of nitrate is just as good as another from whatever source 

 derived. The same is true in the case of ammonia ; if it is 

 actually ammonia, one pound is as good as another, and this 

 will probably prove true in the case of the new products, not 

 yet fully investigated. 



In the case of organic products, on the other hand, the 

 value of a pound of nitrogen will vary widely, depending 

 upon its source of supply ; the farmer in buying a commercial 

 fertilizer, in which nitrogen exists both in soluble and insol- 

 uble forms, can absolutely depend upon the nitrogen in the 

 soluble form, but, unless some special tests are made, cannot 

 depend uix)n tlie forms of the organic nitrogen, as they will 

 vary widely in their rate of availability, the rate ranging, 

 say in dried blood and leather, from 75 or 80 per cent in 

 dried blood to practically nothing in some forms of leather, 

 when compared with the standard or nitrate form. The 

 farmer, therefore, in purchasing his supplies should know 

 not only how mucli nitrogen is contained in the brand, but in 

 what form it exists, and then purchase that brand which con- 

 tains the forms in such kinds and proportions as, in his 

 judgment, will best meet the requirements of his crop. 



The same considerations in a general way apply to the 

 phosphates. All farmers know that animal bone is a good 

 source of supply of phosphoric acid. They also know that 

 the availability of the phosphoric acid will differ in different 

 samples. They are also familiar with the fact that other 

 sources of supply of phosphoric acid in their original and 

 untreated forms will vary widely in their rate of availability, 

 and, therefore, in the usefulness of the materials for different 

 purposes for wliich they are used. They also know that 

 ground bone is likely to give up its phosphoric acid to plants 

 much more quickly than the gi'ound phosphate rocks of 

 Florida, South Carolina and Tennessee, even when ground 

 to the same degree of fineness. They understand, moreover, 

 that ground bone is an organic substance, and, even in its 



