352 THE PRINCIPLES OF SOIL MANAGEMENT 



combination or remain as the carbonate, never being 

 present as the oxide. It is always desirable to have 

 present in the soil at least a small amount of calcium 

 carbonate. 



222. Caustic lime. Quicklime and water-slaked lime 

 have a markedly alkaline reaction, and hence neutralize 

 quickly any acidity that may exist in the soil. They act 

 also quickly in liberating plant-food, particularly nitro- 

 gen. Some soils respond more rapidly to quick- or water- 

 slaked lime than to carbonate of lime, especially when 

 the carbonate is in the form of marl or ground limestone, 

 in which cases it is never in such a finely pulverized con- 

 dition. The use of the caustic forms of lime has been 

 said to result in the loss of nitrogen by the decomposition 

 of organic compounds. 



Upon clays, the granulating effect of caustic lime is 

 more marked than that of the carbonate, and for this 

 reason the former has a distinct advantage for use on 

 heavy clay. An occasional moderate dressing is, for the 

 same reason, better than a heavy dressing given less 

 frequently. 



223. Carbonate of lime. Air-slaked lime has the 

 advantage of being in a finely divided condition, and 

 does not produce the injurious action upon organic 

 matter attributed to caustic lime. Its effect upon the 

 granulation of clay soils is probably less pronounced 

 than that of caustic lime. 



Marl differs from air-slaked lime principally in its 

 property of being in a less finely pulverized condition. 

 It acts less quickly than does caustic lime. Owing to 

 the fact that marl deposits differ greatly in the compo- 



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