SIXTEENTH CHAPTER. 



WHERE CAN WE GET OUR NITROGEN? 



jDESIDES the complete manures considered in the 

 foregoing chapters, there are an endless num- 

 ber of other substances available for manurial pur- 

 poses, and many of these are often a much cheaper 

 source of plant food, in certain localities, than either 

 the city stable manure, or the concentrated manures 

 found in our markets. Some of these substances 

 contain only a single element of the three chief ones 

 under consideration, others have a combination of 

 two, others are perhaps complete, but more or less 

 one-sided; and altogether there is choice enough, so 

 that we can purchase just what element, or combi- 

 nation of elements we may need, without having to 

 buy one we do not want or require 



We will try to ascertain the true value of the 

 leading substances available for these purposes. 



As stated once before, tons and tons of nitrogen, 

 in an uncombined and free elementary state, only 



