LIMING THE SOIL 



369 



while merely tentative, serve in a general way as guides in 

 practical liming operations for a four- or five-year rotation 

 with average soils. The general degree of acidity may be 

 estimated from a qualitative test. 



Table LXXXII 



SUGGESTED AMOUNTS OF AVERAGE PULVERIZED LIMESTONE THAT 



SHOULD BE APPLIED TO THE ACRE UNDER 



VARIOUS CONDITIONS. 1 



201. Changes of lime in the soil. — When calcium oxide or 

 calcium hydroxide are added to the soil, they undergo a very 

 rapid transformation, especially if the soil is moist. The 

 oxide takes up water and becomes the hydroxide, while the 

 latter almost as quickly changes to the carbonate. The reac- 

 tions are as follows : 



CaO + H 2 = Ca(OH) 2 

 Ca(OH) 2 + C0 2 = CaC0 3 + H 2 



It is generally supposed that when once the carbonate is 

 formed in the soil or added as pulverized limestone, it is more 



1 The equivalent amounts of burned or slaked lime may readily be 



calculated from the chemical equivalents already quoted. Calculate for 



example the amount of slaked lime, carrying 65 per cent, of CaO and 



5 per cent, of MgO, necessary to equal an application of 2000 pounds of 



adequately pulverized limestone containing 48 per cent, of CaO and 2 



per cent, of MgO. The 5 per cent, of MgO in the slaked lime and the 



2 per cent, of MgO in the limestone are equivalent in neutralizing capacity 



to 6.9 and 2.8 per cent, of CaO, respectively. The slaked lime and the 



limestone, therefore, carry the equivalent of 71.9 and 50.8 per cent, of 



2000 X 508 

 CaO, respectively. =-^ == 1413 pounds, the amount of slaked 



lime necessary to equal 2000 pounds of the limestone. 



