Lime, Its Value and Importance 1G75 



Oyster shells contain about 95 per cent, carbonate of lime and 

 if finely ground are as good as limestone for the soil. 



Wood ashes, often valued chiefly for their content of potash and 

 phosphoric acid, contain about 30 per cent, carbonate of lime, 

 which is equal in value to an equivalent amount of calcium car- 

 bonate in limestone. 



Marl is a loose deposit, mostly of small shells mingled with 

 clay. It varies greatly in composition and should be purchased 

 only on the l)asis of carbonate of lime present as determined by 

 analysis. Limestone and marl, carrying equal amounts of calcium 

 carbonate, are of equal value in soil improvement. 



Another material quite rich in lime is basic slag, commonly 

 known as Thomas slag. In commerce it is valued chiefly for its 

 content of phosphoric acid, which is about 16 per cent. It con- 

 tains free lime, has an alkaline reaction and is an efficient carrier 

 of phosphorus on some soils. It would not be economical to use 

 it to overcome acidity, since lime as such is much cheaper, but it 

 has a place in soil improvement. 



The advisability of using fresh burned lime, slaked lime, car- 

 bonate of lime or any of the by-products, depends upon many 

 factors. The chief factor is the cost of a given quantity of calcium 

 oxide, since lime is purchased and applied chiefly for its power 

 of correcting acidity. The value of the various forms, if con- 

 sidered from this point of view alone, must be comparable to the 

 amounts of calcium oxide or actual lime they contain. 



Bearing in mind the relationship previously brought out, it is 

 evident that the price of limestone per ton should be less than that 

 of quicklime, and the price per ton of slaked lime less than of 

 quicklime, but greater than that of limestone. Stated exactly, 

 56 pounds of quicklime, 74 pounds of slaked lime and 100 pounds 

 of ground limestone or marl should be purchased at approximately 

 the same prices, assuming equal purity, and thus purchased are 

 equally good bargains; acid correcting power alone being 

 considered. 



EXPENSE OF LIMING 



In much of southern ISTew York (the writer cannot give the 

 figures for other sections of the state) $4 per ton is the 

 average price for fresh burned lump lime delivered in car lots at 



