IDEAL FERTILIZERS 15 



cal form being so much finer, allows quicker action and 

 the general application of air-slaked lime is about a ton 

 per acre, thus another application will be needed much 

 sooner than when crushed limestone is used. The eco- 

 nomical buyer does not purchase air-slaked lime, for 

 it costs as much per ton as the hydrated and the same 

 freight, yet it is really worth only three-fourths as much. 



Miscellaneous Forms Sulphate of lime, gypsum, or 

 land plaster, is not a base but is most valuable in in- 

 ducing chemical changes that bring latent plant food 

 (potash in particular) into availability. Superphosphate 

 and dissolved boneblack are about two-thirds sulphate 

 of lime, and one-third phosphate of lime. Sulphate of 

 lime combines with free ammonia, fixing it as sulphate 

 of ammonia. Unleached wood ashes contain about 35 

 per cent, carbonate of lime, and Basic Slag is popularly 

 believed to carry about 33^ per cent, of free lime, but 

 Dr. Van Slyke, Chemist of the Agricultural Experiment 

 Station of New York, says that though there is about 

 a 35 per cent, content of calcium, "generally less than 

 two and often less than one per cent, is present as 

 calcium oxide or so-called free lime, while the amount 

 of carbonate is insignificant." 



Free lime must not be mixed with fertilizer, as it 

 causes a waste of ammonia. Lime should not be used 

 on Irish potato land; it makes conditions favorable for 

 scab. Lime around cabbage, etc., keeps down club root, 

 and on sweet potato ground has been found most effective 

 in reducing soil rot of sweet potatoes. 



