240 HANDY-BOOK OF HUSBANDRY. 



The analysis of the ashes of all agricultural plants shows that 

 they contain the following substances : — 



Potash, Soda, Lime, 



Magnesia, Sulphuric acid. Phosphoric acid, and 



Silicic acid. Oxide of iron. Chlorine. 



Of these the following are always found in abundant quantity 

 in every even tolerably fertile soil, — probably in every soil that it 

 will pay to attempt to cultivate : — 



Soda, Sulphuric acid. Chlorine, and usually 



Oxide of iron. Silicic acid. Magnesia. 



These, then, need never be taken into consideration in any 

 case where the only object is the supply of the materials which 

 the plant requires. 



With the other elements, however, the case is quite different, 

 and 



Phosphoric acid. Lime, and occasionally 



Potash, Magnesia, 



require the utmost care on the part of the farmer, and a constant 

 vigilance to prevent their waste, and to restore always at least so 

 much of them as is taken away by the crops.* 



The analysis of any tolerably fertile wheat soil will show that It 

 contains, within a foot of the surface, an amount of phosphoric 

 acid sufficient to supply the needs of probably a hundred times as 

 many bushels of wheat as could be grown upon it in a hundred 



* Probably the analysis of every cultivatable soil in the world would show the presence 

 of a large proportion of lime ; and the rule which requires the use of lime as manure is 

 by no means a definite one. Whether the lime supplied acts only as a plant-food, or 

 whether its chief benefit depends on its action in developing plant-food already con- 

 tained in the crude soil, is not absolutely known. Probably, however, the latter 

 proposition is the true one, inasmuch as we find that soils which are formed almost 

 exclusively by the crumbling of limestone rocks are quite as much (and often more) 

 benefited by the application of very small quantities of burned lime, as are those in which 

 analysis shows only a trifling proportion of lime ; therefore the above is to be understood 

 as being such a statement of the case as seems most necessary for practical purposes, 

 although not in all respects scientifically correct. 



