f'j) Slag meal. This material is used primarily as a source of 

 ohosphoric acid, but it usually contains also from 40 to 50 per 

 cent of actual lime. A considerable proportion of this lime is in 

 combination, though about one-fourth of it is usually found in the 

 free form. About one-half of the lime present is believed to exist in 

 combination with phosphoric acid, and the balance is in combina- 

 tion with silica as a basic silicate of lime. The latter compound is 

 usually soluble and when applied to the soil must act in many 

 respects in a manner similar to free lime. It would probably not be 

 advisable to depend upon slag meal for the purpose of producing 

 that sharp change in mechanical condition which is needed in the 

 heavy, sour clays ; but by a rather free use of slag meal many of the 

 ordinarily looked for beneficial effects of liming may be expected to 

 follow ; and in any case, if soil has once been brought into satisfac- 

 tory condition by one heavy application of lime, we may doubtless 

 depend upon the lime in slag meal freely used as a source of phos- 

 phoric acid to hold the soil in a satisfactory condition as regards 

 that element. 



Different plants require varying amounts of lime, 



The relation some are extremely sensitive to and much injured 



of lime to by the presence of free acid. Others are compar- 



crops. atively indifferent to the presence of such acid, 



while still others appear to do better in soils con- 

 taining it. Among plants requiring large amounts of lime in the 

 soil are clovers, alfalfa, peas, beans and vetches. Grasses as a rule 

 require less lime than clovers; but timothy will not do well in soils 

 markedly deficient in lime On the other hand red top thrives in 

 sour soils. Neither corn nor millets are especially sensitive to acid. 

 They will often do well on soils which are sour. The same is true 

 of potatoes, although excessive acidity is undesirable even for these 

 crops. Cabbages and turnips and all the cultivated members of the 

 same family require large amounts of lime. Mangel wurtzels, sugar 

 beets, and table beets are usually benefitted by liming, as are also 

 onions, spinach, lettuce, and parsnips. Celery also is said to be 

 much benefited by liming. Among fruits, the apple, pear, peach, 

 plum, and cherry usually do best where lime is abundant. The black- 

 berry, on the other hand, does well in soils containing free acid and 

 some experiments indicate that the strawberry does not particularly 

 require liming. Lime should not be applied immediately preceding 



