MANUKES, THEIE KINDS AND USES. 49 



and is lost. We may see this take place, if we heat de- 

 caying vegetable matter with lime, or witness it if we 

 mix guano and quick-lime together in the palm of the 

 hand, and smell the escaping ammoniacal gas. A good 

 soil may, without any recent manuring, contain three 

 thousand or more pounds of nitrogen per acre in the first 

 six inches of depth, or as much as is contained in three 

 hundred and thirty-three tons of fresh horse manure, and 

 yet require a fresh application of soluble nitrogenous 

 manure to bring a satisfactory crop to maturity. The rea- 

 son is, that the above large amount of nitrogen is locked 

 up in the soil, existing in unassimilable combinations, in 

 short, is unavailable. Professor Johnson found only 

 sixty-three pounds of available nitrogen in four thousand 

 six hundred and fifty-two pounds of a soil per acre, at 

 the depth of twelve inches. 



Every arable soil contains a sufficiency of lime for the 

 direct needs, as plant food, of any crop; and while the 

 cereals, or grain plants, contain less of lime, both in 

 grain and straw, than any other crop, they especially re- 

 quire nitrogenous manure, and to these the general agri- 

 culturist applies it freely. Now, a simple dressing of 

 lime has been known to double the yield of grain on a 

 soil containing unavailable nitrogen. 



It would require too much space to mention the chem- 

 ical changes lime undergoes from its condition as carbon- 

 ate of lime in rock or shells, until, as caustic lime, it 

 exerts its strange power, or to attempt an explanation of its 

 extraordinary effects, not yet fully understood, upon the 

 various constituents of the soil. 



Suffice it to say: First. It renders stores of wealth in 

 the soil available to crops. Second. It neutralizes acids 

 in the soil which might be injurious to vegetation. 

 Third. It rapidly decomposes vegetable matter in the 

 soil, and renders its elements fit for plant food. Fourth. 

 It amends the physical texture both of heavy clays and 



