118 AMERICAN MANURES. 



nothing but the mineral or inoryanic elements 

 in the form of ash; the carbon, oxygen, hydrogen, 

 and nitrogen, passing off in a gaseous form ; on the 

 contrary, the slow combustion that takes place 

 under the ordinary processes of decay, is limited 

 by the small amount of oxygen that can come 

 in contact with the carbon. A part of this 

 oxygen is furnished by the decomposition of the 

 water present ; the oxygen thus liberated unites 

 with the carbon to form carbonic acid, and the 

 hydrogen unites with nitrogen to form ammonia. 

 Inasmuch as the decomposed remains of all 

 the parts of any plant contain all the inorganic, 

 with a portion of the organic elements originally 

 contained in it, these remains would furnish a 

 most efficient manure for the production of other 

 plants of the same species. But if we desire to 

 grow another kind of plant, requiring a larger 

 amount of one or more of the elements, the de- 

 ficiency must be supplied, or, if a part of the 

 plants be removed from the soil, the elements 

 contained in that part must be renewed by a 

 manure. Wheat serves as an example. The 

 grain, which contains the largest amount of the 

 most valuable elements of fertility, is removed ; 

 and even should all the straw be returned to the 

 soil in a decomposed state, it would evidently 

 lack the amount of the elements contained in the 

 grain. Hence the necessity of applying, in a 



