368 NATURE AND PROPERTIES OF SOILS 



Suppose that slaked lime carrying 70 per cent, of calcium 

 oxide (CaO) sells in carload lots at $8.00 a ton and that pul- 

 verized limestone of a fair degree of fineness costs in bulk 

 $4.50 and analyzes 50 per cent, of calcium oxide. Assume the 

 freight as $3.00 a ton and the cost of hauling to the farm and 

 applying to the land as $1.00 more. 



The application of 1 ton of the agricultural slaked lime 

 would cost $8.00 + $3.00 + $1.00 = $12.00. It would be 

 necessary to apply 1.4 tons of the limestone to every ton of 

 slaked lime. This would amount to $6.30 + $4.20 + $1.40 

 = $11.90. The difference in this case is very slight be- 

 tween the two forms. Lessening the freight or shortening 

 the haul would give the advantage to the limestone, while in- 

 creasing these would favor the use of slaked lime. 



It is obvious from such calculations that a flat recommenda- 

 tion cannot be made in a county or community regarding the 

 lime to use. Each individual case should be calculated, con- 

 sidering the cost items already mentioned. 



200. Amount of lime to apply. — The possibility of an 

 application of lime paying and the form to purchase can usu- 

 ally be determined with considerable assurance. Such is not 

 the case, unfortunately, regarding the amount of a given kind 

 of lime to apply to the acre. So many factors, of which soil 

 reaction is only one, are active in determining crop growth 

 that acre applications are at best estimates and often admit- 

 tedly guesses. Not only the degree of acidity but the texture 

 and the structure of the soil, the crops grown in rotation, the 

 length of the rotation, the fertilizers used, the amount of farm 

 manure added in a given period, and similar conditions must 

 be considered. In ordinary practice, it is seldom economical 

 to apply much more than a ton of limestone or its equivalent 

 to the acre, unless the soil is very acid and the promise for 

 increased crop yield exceptionally good. In many cases, it 

 seems unnecessary entirely to correct the acidity of a soil in 

 order to promote normal crop growth. The following figures, 



