138 Fertilizers 



lime, though the commercial product seldom contains 

 more than 52 per cent and varies from 42 to 54 per cent 

 of actual lime. 



The action of this material is dependent in large meas- 

 ure upon the fineness of division. Products are upon the 

 market which vary from coarse pieces to a very find pow- 

 der, 85 per cent of which will pass through a 200-mesh 

 screen. The very coarse material acts very slowly and 

 should be avoided except perhaps for use upon very light 

 soils. In general, 75 per cent ground limestone should 

 pass through a 100-mesh screen for profitable agricul- 

 tural use. 



Calcium-magnesium lime. 



What is termed "marble lime" is made from pure lime- 

 stone, and the burned lime thus obtained is practically 

 pure oxide of lime. Limestone, so called, is not always 

 pure. Sometimes it is a mixture of lime and magnesia, 

 in which case it is the mineral "dolomite" and is termed 

 "magnesian limestone." A very large quantity of the 

 lime used in the eastern states is the magnesium form. 

 The burned lime from the magnesian limestone contains 

 from 50 to 60 per cent of calcium oxide, and 20 per cent 

 or more of magnesium oxide. Similar ground products 

 contain 25 to 30 per cent of calcium oxide, and 10 per 

 cent or more of magnesium oxide. In some instances, 

 the magnesium oxide is of value, though it is rather 

 inert in its effect, and is less useful than the lime. It 

 is believed to have a beneficial effect upon the bacterial 

 activity of soils. A safe method in the purchase and 

 use of lime is to adjust the price to the proportionate 

 percentage of actual lime present, practically in the ratio 

 of 10 to 7. 



