LIMING THE LAND IOI 



per cent, of lime, you should not substitute it for ordi- 

 nary lime for correcting acidity in soils. Its effect is 

 rather stimulative, aiding in setting free other plant 

 foods, notably potash. 



Lime is found, also, in earthy shell deposits known as 

 marls. These occur only in lake and ocean regions, and 

 for this reason they are little used outside of the immedi- 

 ate locality in which they are found. In composition, 

 marls vary greatly : from 10 to 50 per cent, of lime being 

 available. 



Oyster shells, also, are lime makers. They contain 

 about ninety per cent, of lime, which, when burned, is 

 comparatively pure. Gas lime, now sold extensively as an 

 agricultural lime, occurs in this way : quick lime is used 

 in gas works for the sole purpose of taking from the gas 

 its many impurities. When saturated, and hence no 

 longer useful, it is sent away under the name of gas lime, 

 to be used as a fertilizer for soils. Gas lime contains, on 

 an average of about forty per cent, of lime. Since gas 

 lime is often poisonous, it is not desirable for the land. 



What lime does in the soil. When applied to land, 

 lime acts in these ways: it induces chemical activity, 

 causes physical change, usually favorably, and supplies a 

 plant food element calcium. In reference to the last, let 

 this be said : little evidence points to any conclusion that 

 lime is lacking in most soils to such an extent that any 

 additional supply is needed for food requirements. While 

 it is true that some investigators have been led to believe 

 the reverse of this, still their contention is far from being 

 proved, and, until fully demonstrated, we shall look for 

 the explanation of its beneficial qualities as being in the 

 direction of the chemical and the physical changes that 

 take place, occasioned by its presence in the soil. 



How lime acts chemically. First in importance are its 



