1913] Lime on Soils 59 



TABLE OF EQUIVALENTS 



Dolomite 



CaCoa 



MgCO 



100 lbs. of pure limestone will produce when burned, 56 

 lbs. of quicklime which, when air-slaked, becomes 100 lbs. of 

 finely powdered lime carbonate. If the 56 lbs. of quicklime be 

 water-slaked, it unites with 18 lbs. of water to form 74 lbs. of 

 hvdrated lime. 100 lbs. of ground limestone contains the same 

 amount of lime as 167 lbs. of 60% marl; one ton of hydrated 

 lime is equal to three-quarters of a ton of quicklime and to two 

 and one-fourth tons of 60% marl. If a given amount of ground 

 limestone (one ton for example) is worth $1.00, the same quant- 

 ity of 75% marl is worth (by weight) $.75, and of hydrated 

 lime, $1.35. This however does not indicate the relative values 

 of their effects on the soil. 



ADAPTATION OF FOEMS 



Gypsum. — This form of calcium does not neutralize the 

 acidity of the soil but on the other hand tends to increase it 

 and should not therefore be used except on neutral or alkaline 

 soils and then only in small quantities. It frequently changes 

 some of the potash of the soil to the soluble form and sometimes 

 makes more phosphorus available for the use of the plant. 



In its effects on soil structure it decreases the rate of move- 

 ment of capillary water and consequently reduces evaporation 

 from the surface (in sandy soils 27%, King, The Soil, p. 177). 



Gypsum accelerates the process of nitrification more than any 

 other known substance. Its relation to lime in this respect may 

 be seen in the following figures: lime carbonate, 13.3; gypsum, 

 100 (Hilgard, Soils, p. 147). It should be used on soils for 

 this purpose only. 



Dolomite. — This rock when ground very fine and applied to 

 the soil has much the same effect as the lime carbonate especial- 

 ly on the first two or three crops following its application. 



