1 68 SYSTEMS OF PERMANENT AGRICULTURE 



In commenting on these results, Director Patterson of the Mary- 

 land Experiment Station says: " It will be noted that the car- 

 bonate of lime gave decidedly better results than the caustic lime." 



Neuffer, of Heilbronn, Germany, has published a book entitled, 

 " Das Kalksteinmehl im Dienste der Landwirtschaft " (The Use 

 of Ground Limestone in Agriculture), in which he advises that 

 ground limestone, and " not burned lime," should be used in the 

 improvement of soils deficient in lime. 



Porter and Grant, in a recent Farmers' Bulletin issued by the 

 Agricultural Department of the County Council of Lancaster, 

 England, report experiments on manured and unmanured meadow 

 lands, showing that ground limestone is more profitable as an 

 application to grass lands than burned lime, and that it can be 

 economically used on grass lands which are in need of lime. 



No trustworthy investigations support the use of burned lime 

 in preference to ground limestone; although we have ample in- 

 formation showing that on many soils a moderate use of burned 

 lime in connection with a liberal use of farm manure and green 

 manures yields profitable returns, which would, no doubt, be still 

 more profitable if the burned lime were replaced with ground 

 limestone. 



The most abundant impurity of limestone is magnesium car- 

 bonate, which sometimes occurs in equal molecular proportion with 

 calcium carbonate, in what is called dolomite (CaCO 3 MgCO 3 ). 

 Limestones containing considerable amounts of magnesium car- 

 bonate are also called magnesian limestones, even though the 

 proportion of magnesium may be less than in dolomite. 



Dolomitic limestone is usually slightly heavier than ordinary 

 limestone, and it is scarcely attacked by cold hydrochloric or acetic 

 acid, while pure calcium carbonate is rapidly decomposed, the 

 carbon dioxid being liberated as a gas. 



The molecular weights are 100 for calcium carbonate and 84 for 

 magnesium carbonate, and consequently 84 pounds of the latter 

 has the same power to correct soil acidity as 100 pounds of the 

 former; or 92 pounds of dolomite will correct as much soil acidity 

 as 100 pounds of pure ordinary limestone. 



To determine the amount of limestone present in the soil, or to 

 determine the value of a sample of limestone for use on acid soils, 



