No. 5. 



DEPARTMENT OP AGRICULTURE. 



181 



DIRECTOK MARTIN: Will you permit a question relative to 

 the hydra ted lime? What eflect, if any, would time have on hydra ted 

 lime if it were kept? 



PROF. McDowell : I was just about to speak of tliat. When 

 stone lime or water-slaked lime has been exposed to the air, it finally 

 takes from the air carbon dioxide, the material that was driven off 

 by burning the limestone. The 56 jjounds of burned lime would 

 increase in weight until it became practically 100 pounds. In gen- 

 eral, one ton of burned lime would require two tons of ground lime- 

 stone, or one and one-third tons of hydrated lime to furnish the 

 equivalent amount of lime. 



A Member: If you apply burned lime and carbonate of lime, will 

 they act the same? 



PROF. McDowell : if the limestone was finely ground it would 

 ict as quickly as the burned lime. An experiment has been in pro- 

 gress at the Experiment Station for two years for the purpose of 

 determining the relative value of burned lime and limestone, as well 

 as the value of limestone in different degrees of fineness. The value 

 of lime is based on these factors; solubility in water, efficiency in 

 correcting acidity, nitrification, and growth of plants. The follow- 

 ing figures show the solubility in carbonated water as compared with 

 distilled water: 



Burneil lime 



Ground limestouc (I'X) raesb), 



Ground linieKtone (20 mesh), 



Giuuud limestone (8 mesh), 



Limestone is practically insoluble in pure water, but when ap- 

 [)lied to the soil it is readily dissolved by the soil water. It will be 

 oberved, too, that the finer the limestone the more soluble it is. 



The first function of lime, after being dissolved in the soil, is to 

 correct the acidity thus making the soil sweet. A very acid soil 

 was treated with different forms of lime and after one month the 

 acidity was determined. The following figures show the relative 

 value in correcting acidity. These figures are stated in percentage 

 of total aciditv corrected. 



Burned lime 



Ground limestone (ICO mesh), 

 Ground limestone (60 mesb), 

 Ground limestone (20 mesh), . 

 Ground limestone (8 mesh), .. 



90.3 



80.fi 

 61.9 

 33.2 

 22.2 



These figures indicate that the finely ground limestone has prac- 

 tically the same value as the burned lime, the difference being about 

 10 per cent. In case of the 60 mesh there is a difference of over 30 



