30 THE HANDBOOK FOR PRACTICAL FARMERS 



shell is burned, about one thousand one hundred aild twenty 

 pounds 01 stone or burned lime is produced. When this is 

 slaked it takes up water until it weighs about one thousand 

 four hundred and eighty pounds and is known as hydrated 

 lime. When this is exposed to the air for some time it goes 

 back to the carbonate or limestone form and to the original 

 weight. Since all lime quickly reverts in the soil, the form in 

 which it is applied is of importance only in regard to its con- 

 centration and the fineness of the particles. Raw ground lime- 

 stone or oyster shell have only about half the strength of burned 

 lime and two-thirds that of the hydrated lime. 



Fig. 12. — Twelve bushels of wheat per acre with fertilizer alone; twenty bushels with 

 lime and fertilizer. The first step in building up fertility is to make sure that 

 the soil is supplied with lime. 



The value of any form of lime depends upon the total 

 percentage of calcium and magnesimn oxide contained. Ground 

 limestone or shell should contain about fifty per cent of total 

 oxide; hydrated lime about seventy per cent; and lump or 

 burned lime above ninety per cent. To compare the prices on 

 several kinds of lime divide the cost per ton of each, delivered, 

 by its percentage of oxide. This gives the cost per unit or per 

 twenty pounds of oxide or actual lime. 



Applying lime. — Crops that grow moderately well on sour 

 soil are potatoes, tomatoes, buckwheat, berries, carrots, water- 

 melons and red-top grass. Practically all other crops are bene- 

 fited by lime, but the most responsive crops are alfalfa, clover, 



