LIMING THE SOIL. 49 



The minerals, calcium and magnesium are the essential ele- 

 ments in neutralizing acids. Oxygen and carbon combine with 

 calcium and magnesium and are rendered into usable forms. 



It therefore follows that burning and slaking do not change 

 the power to neutralize acids, and thus 100 pounds of pure ground 

 limestone, 56 pounds of quicklime, 74 pounds of water-slaked 

 lime, and 100 pounds of air-slaked lime are equal in their power 

 to neutralize acids. 



Some of the important effects of using lime on the soil may 

 be stated in the following important points : 



1. Ground limestone and air-slaked lime are less destructive in 

 their action on the soil than quick-lime or water-slaked lime and 

 are therefore to be preferred. 



2. Calcium and magnesium have similar effects in their action on 

 the soil. 



3. Calcium and magnesium are equally necessary as plant foods, 

 therefore lime considered as a source of these elements may be 

 considered as a plant food. 



4. Lime used on the soil should be from a limestone containing a 

 high per cent of calcium and a low percentage of magnesium. 



5. To be beneficial the application of lime will vary according to 

 conditions from one to three tons or even more per acre. 



6. Equivalent Weights. 



2,000 pounds of burned lime is equal to : 

 2,702 pounds of hydrated lime. 

 3,572 pounds of ground limestone or marl. 

 2,702 pounds of air-slaked lime (new). 

 3,572 pounds of air-slaked lime (old). 

 About 3,000 pounds of hardwood ashes. 



Sources of Lime. 



The term ''Agricultural Lime" may be very misleading, and 

 unless the purchaser understands the composition of the mixture 

 offered for sale the term "agricultural lime" is indefinite and 

 does not signify anything as to composition or value. 



A few of the sources of lime with the percentage of lime 

 contained is given here to furnish some very desirable informa- 

 tion.* 



* Send for Circular 123; Ohio Experiment Station. 

 4 



