NITROGEN IN AGRICULTURE. 303: 



not, as a whole, escape into the air, as when it is set free by- 

 explosions, but it appears in the liquid and solid excrement 

 in certain forms of combination, which, to become fixed and 

 serviceable as plant-food, must receive intelligent care. The 

 proneuess of nitrogen to disassociate or free itself from its 

 combinations is seen in the changes which excrement under- 

 goes soon after leaving the animal organism. So long as 

 nitrogenous compounds are controlled by the vital forces of 

 animal life, they are held in check, and their equilibrium is 

 preserved ; but, as soon as the external air is reached, it 

 struggles to free itself from its environments. The highly- 

 organized compounds take on fermentative changes : hydro- 

 gen (another gaseous body) is evolved, and the nitrogen is 

 led into an alliance with this element in such proportions as. 

 to form ammonia. Ammonia is distinguished for its volatility, 

 or readiness of escape, whether it be free or in the form of a 

 carbonate. When nitrogen seeks to escape through this 

 agent, it must be fettered by forcing it into new and stronger 

 combinations. The sulphate of ammonia is a stable body, 

 capable of restraining nitrogen ; and hence if we apply to 

 fermenting manure-heaps sulphate of lime, or what is known 

 as plaster, sulphate of ammonia results through a process of 

 double decomposition, and we have a nitrogenous salt, per- 

 manent, and well adapted to the purposes of plant-nutriment. 



It has already been stated that nitrogen has no value for 

 farm purposes in its elementary, gaseous state ; but, when in 

 chemical union with oxygen or alkaline bases, it becomes a 

 factor in successful husbandry of the first importance. An 

 interesting inquiry arises at this point : Through what natu- 

 ral agencies is nitrogen fitted to become plant-food? How 

 does it happen that an element so sh}^ and indifferent is 

 found in soils in a combined state, so as to be assimilable 

 by growing vegetation ? 



Investigations made at my experimental farm in Essex 

 County during the past twenty-five years lead to the con- 

 clusion that the most prominent source of fixed nitrogen 

 found in soils comes from the atmosphere. I am quite cer- 

 tain that most chemists are in error in regarding as of com- 

 paratively small consequence this source of the agent. The 

 view that nitrogen and ammonia are simply accidental agents 

 in the air, and very sparsely diffused, is founded upon incor- 



