156 MANURES. 



quantities of some kind of bulky manure ; as manure 

 from the yard, or better, this composted with 2 or 3 

 times its bulk of peat or swamp mud. If land, that 

 has been ploughed so long as to have become deprived 

 of its organic matter, is still to be kept under the 

 plough, it must receive great quantities of bulky ma- 

 nure. It will not do in such cases to rely upon any- 

 thing else. 



OBJECT OF APPLYING MINERAL MANURES. 



291. If we look again at Professor Johnstone's analy- 

 ses of soils (Table IV.), we shall find among their con- 

 stituents all the bases mentioned in Table III., and 

 several of the acids. These do not exist in soils separ- 

 ately, but in combination with each other as salts. 

 For instance, phosphoric acid and lime are found as 

 phosphate of lime ; carbonic acid and lime, as car- 

 bonate of lime ; sulphuric acid and lime, as sulphate of 

 lime ; and so each of the acids may be combined with 

 other bases, forming various salts. Chlorine and soda 

 are more usually found in combination, as common 

 salt. 



292.. When we apply mineral manures, it is for the 

 purpose of adding these salts to the soil. It often hap- 

 pens that a soil containing a good supply of organic 

 matter, and otherwise in an apparently high condition, 

 will not produce a particular crop, because it lacks one 

 or two mineral ingredients, which that crop requires. 

 In the ashes of clover is found a considerable quantity 

 pf both sulphuric acid and lime; consequently that 



