NITEOGEN IN AGRICULTURE. 171 



Nitrogen in Agriculture. 



Bj' Hon. James J. H. Gregory, Marblehead. 



What is nitrogen ? The air mass surrounding the earth to a 

 depth of nearl}' fifty miles is composed of about four-fifths nitrogen 

 in combination with one-fifth ox3'gen gas. There are always right 

 at hand unnumbered thousands of tons of nitrogen. But this vast 

 store of potential wealth is unfortunately never available to the 

 agriculturist. His chemistry has never ^-et mastered the problem 

 of drawing upon atmospheric nitrogen for plant food. 



He has tcr depend for his supply wholly on that which has been 

 incorporated into the structures of plants or animals. His sole 

 resource consists in the wastes of these organic structures ; in the 

 form of excrements, or of dead remains, either from land or sea. 

 The ammoniated liquor from the gas works is waste produced from 

 the remains of ancient forests now consumed as coal. 



The same is true of animal life as of plant life. While over 

 three-fourths of the air we breathe is nitrogen, and while it enters 

 so largely into the composition of our bodies, it appears totally 

 inert in respiration, and enters the system solel}' through the 

 organs of nutrition and in the form of vegetable or animal sub- 

 stances used as foods. As the product of animal decay, in drinking- 

 water it is sometimes prejudicial to health, causing ' dangerous 

 fevers. 



Combined with h3'drogen, in the proportion of 82 parts to 18 

 of the latter, it becomes ammonia ; one of the most common forms 

 in which, from the waste of both animals and plants, nitrogen is 

 fed to our crops. It is well to fix in the mind that in changing 

 nitrogen to ammonia, in any manure analysis, we must add about 

 one-fifth to the quantity given. The other most important form of 

 nitrogen is nitric acid. This is a combination of nitrogen with 

 oxygen ; and nitrates, of which we see frequent mention in all 

 works on manures, are a combination of nitric acid with soda, 

 potash, and other materials, which are called bases. 



It appears to be a settled conviction among men of science, as a 

 result of many experiments, that plants cannot take up pure nitro- 

 gen directly from the air. The theory is that they are able, to a 

 greater or less degree, to get their supply through the water that 

 carries it in some form in solution into the soil ; and also, indi- 

 rectly, from the air which permeates the soil and under its influences 

 yields up its nitrogen. Also there is nitrogen latent in the soil, 



