242 



SOIL ACIDITY AND LIMING 



FiQ. 158. — This farmer found a good outcrop of excellent limestone. Most of his soils are 



strongly acid. 



Fig. 159, — A soil derived from limestone and underlaid by crumbled limestone. This 

 soil is acid to a depth of three and one-half feet, within two inches of the rotten limestone. 



Air-slaked Lime. — This is formed when lime used in making 

 plaster and mortar is exposed to the air. On exposure, the carbon 

 dioxide gas of the air is absorbed and this action converts the lime 



