244 SOIL ACIDITY AND LIMING 



the heavier soils. It should be finely ground, water-slaked or 

 air-slaked before applying. When lump Ume is finely gi-ound 

 the term ^'ground Hme'^ is given it. 



Lump lime for agricultural use is more generally used in the 

 Eastern States than in the Middle West. 



Hydrated Lime. — When lump lime is treated with water or 

 steam, in the absence of air it becomes a powder quite like ground 

 lime in appearance, if the proper amount of water or steam is 

 used. The names '^hydrated Ume," ^'limoid^' and ^4imate'' are 

 given this product by manufacturers. It is finely divided and 

 ranks next to lump lime in concentration. This material is not 

 commonly purchased for liming. 



Land-plaster Cannot Correct Acidity. — Land-plaster, or gyp- 

 sum, is sulfate of hme, a material quite different from carbonate of 

 lime. Under certain conditions it supplies calcium and sulfur as 

 plant-food elements, but when pure it has no value in correcting 

 acidity. Usually common land-plaster contains a trace of car- 

 bonates as impurities, but not enough to give it any value 

 as a neutralizer. 



Comparative Value of Agricultural Limes. — The neutralizing 

 value of any material used in liming depends upon its content 

 of lime (CaO) or the equivalent in carbonates, and on its fineness. 

 Pure limestone, for example, contains fifty-six per cent lime (CaO), 

 or it is 100 per cent lime carbonate — ^forty-four per cent being 

 carbon dioxide gas (CO2). It is the calcium and magnesium or 

 their oxides (CaO and MgO) which produce the beneficial effect 

 in acid soils; and the finer the material, the quicker the action. 

 Accordingly, the comparative value of the different forms of lime 

 may be stated as follows: 



(a) On the basis of Hme content — one ton of lump hme equals 

 1.3 tons of hydrated hme equals 1.8 tons of carbonate of lime. 



(b) On the basis of neutralizing value when dry and of equal 

 fineness — one ton of lump lime equals 1.3 tons of hydrated lime 

 equals 1.8 tons of carbonate of lime. 



(c) On the basis of quickness of action, considering pulverized 

 limestone as it is commonly used — one ton of lump lime finely 

 divided is equal to about three tons or more of pulverized limestone. 



Finely pulverized limestone is much more effective than coarsely 

 crushed limestone. 



Best Material for Liming. — For first application to benefit 

 special crops like alfalfa, it is desirable to use finely divided 



