EXPERIMENT STATION BULLETINS. 



490 



is the imion of the lime and silicates to form calcium silicates or the 

 correction of so-called soil acidity. When hydrated lime is added to the 

 soil some of it goes to form air-slaked lime or tlie carbonate and some 

 the calcium silicate. 'Now, the lime or magnesiuiu carbonate thus formed 

 or added to the soil as marl or ground limestone li'cewise passes to the 

 silicates. 



It is now understood that the immediate efficiency of the various forms 

 of lime is dependent upon the rate at which they pass over to the 

 silicate. The hydrate is quite rapid and the carbonates are governed 

 mainh^ by their mechanical state or the size of their particles as well 



*< 3 



:^hMjr ^• 



r 



Figure 3. The More Finely Ground Limestone Reacts More Quickly With the Soil. 



1. No Lime. 2. Lime requirement as 10-20 mesh limestone, o. Lime refiniromont as 40-60 mesh 

 limestone. 4. Lime requirement as 60-80 mesh limestone. 5. Lime requirement as marl. 



as the thoroughness of mixing with the soil mass. Particles of lime- 

 stone approximating 1/100 of an inch in diameter or so-called 100 mesh 

 lime are about as rapid in correcting soil acidity as the hydrate or 

 2,000 pounds of it approximates 1,500 pounds of tlie hydrate in this re- 

 spect, as exemplified by table II. 



TABLE II.— EFFECT OF FORMS AND FINENESS OF LHIE ON THE YIELDS OF RYE 

 ON CASS COUNTY EXPERIMENTAL PLOTS. SANDY SOIL. 191S. 



Trcatinciit. 



Bushels per 

 acre. 



Hydrated lime and acid phosphate and nitrate of soda 



Marl and acid phosphate and nitrate of soda 



Limestone passing SO mesh sci-pon. and acid phospliatf and nitrate of soda. . . . 



Limestone, 40-60 mesh, and acid phosphate and nitrate of soda 



Limestone, 10 20 mesh, and acid phosphate and nitrate of soda | 



No treatment 



21. GO 

 18.40 

 21.28 

 18.36 

 14.40 

 12.82 



Some limestone deposits contain calcium or lime carbonate, and also 

 magnesium carbonate. If the amount of the latter is rather high they 

 are popularly spoken of as magnesium limestones. The larger particles 

 of magnesium limestones are somewhat slower in their .action than the 

 non-magnesium limestones as illustrated by results reported by the 



