SECTION II. SPECIAL SOIL IMPROVERS 



Lime. The exact dividing line between what constitutes a 

 fertilizer and what constitutes a soil improver is rather diffi- 

 cult to determine, but whilst farmyard manure is commonly 

 considered a fertilizer, since it contains nitrogen and potash, 

 yet lime is usually looked upon from a different point of view. 

 The lime is applied to the soil for the purpose of modifying 

 the soil. The standard article is quicklime, produced by 

 burning limestone. This is sometimes applied in big lumps, 

 called shell lime, but it is much better reduced to powder, 

 either by actual grinding, or by slacking with water, when 

 it crumbles down. A high quality burnt lime will contain 

 from 90 to 95 per cent, of lime, and this type of lime should 

 always be used for agricultural purposes. A low quality 

 lime, such as the following : 



TABLE 15. 



Lime . . . . . . . . . . . . 45 per cent. 



Magnesia .. .. .. .. .. ..23 



Carbonic Acid .. .. .. .. 4 



Water -'2 



Silica .. .. .. .. .. ..ii 



Oxides of Iron and Aluminium . . . . . . 16 



is of no use for agricultural purposes. I/ime is sometimes 

 employed to increase the ratio of lime to magnesia, for which 

 purpose the lime in Table 15 is very nearly useless. L,ime, 

 like other materials, should be distributed as evenly as 

 possible, although this may not be quite so critical a point 

 as it is in other fertilizers. One of the purposes for which 

 lime is necessary in a soil is to assist nitrification. Calcium 

 bi-carbonate in solution will rise and fall in the soil, according 

 to the dry or wet weather, though it will not diffuse laterally. 



