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Nitrogenous matters are rarer and more costly 

 than other organic substances, but at the same 

 time they are of the first importance in their 

 application to agriculture. Nitrogen, then, is 

 the element most desirable in the manure ; or in 

 other words the organic matters most advanta- 

 geous in the production of manure are just 

 those which give birth, by their decomposi- 

 Hon, to the greatest proportion of soluble or 

 volatile nitrogenous bodies; we say, by their 

 decomposition, because the mere presence of 

 nitrogen in a matter of organic origin is not 

 sufficient to characterize it as a manure. Coal, 

 for instance, contains nitrogen in very appre- 

 ciable quantities, and yet it has no ameliorant 

 action upon the soil; for the reason that it re- 

 sists the putrefactive action of the atmospheric 

 agents, which always produces ammoniacal 

 salts and other nitrogenous compounds favour- 

 able to the growth of plants. 



For like reasons the activity of manures is 

 proportional to the rapidity of their decompo- 

 sition. Those which decompose quickly, cease 

 their fertilizing influence after a year, whilst 

 the action of those which decompose slowl}^ 

 is prolonged for several years and more. This 

 duration of action is a matter for serious con- 



