Lime and Calcium Compounds 151 



its immediate action. The fineness of ground limestone 

 is entirely arbitrary with the manufacturer. The finer 

 it is, the quicker and more complete will be the action. 

 A guarantee of the size of particles is important and should 

 be insisted upon before purchase. Ground limestone ca- 

 pable of passing at least 75 per cent through a 100-mesh 

 screen or sieve gives prompt action and is suitable for use 

 in most cases. A still finer product is more prompt and 

 a coarser product less prompt in action. If conditions are 

 such as to warrant the use of the coarsely ground limestone, 

 it has the advantage of costing less. 



Peculiar conditions often exist or arise which help to 

 determine the form of lime to use regardless of the fore- 

 going suggestions relating to purchase. Crops sensitive 

 to alkaline soil conditions are injured less and thrive better 

 when the slower acting carbonate is used. This has 

 already been referred to in greater detail. For quick- 

 growing crops requiring a soil rich in organic matter and 

 available plant-food, burned lime is preferable because it 

 brings about chemical changes of the organic plant-food 

 more quickly, causing a rapid and succulent growth. 

 One point of importance in this matter is the solubility 

 of the different forms. The burned lime which is changed 

 to the hydrated form by slaking is more soluble in water, 

 and hence becomes distributed throughout the soil more 

 readily than the carbonate. It is true that slaked lime 

 changes to the carbonate form, but this change requires 

 some time even under the most favorable conditions and 

 during this period the slaked lime is more active chemically. 



Distribution of lime. (See Fig. 13, Plate VI.) 



Lime, no matter in what form, should be evenly dis- 

 tributed and when possible uniformly worked into the 



