400 SOILS 



Much of the potash in our soils is insoluble, being 

 "locked up" in compounds with silica. Lime 

 attacks the silica and sets free the potash. It also 

 prevents the loss of soluble phosphoric acid in the 

 soil. The practical effect of this is that liming may 

 be equivalent to fertilising, for a time. But since 

 lime supplies no potash, phosphoric acid, or nitro- 

 gen, the soil is eventually made less productive. 

 This is the basis for the old adage, "Liming makes 

 the father rich and the son poor." 



The most important function of lime in modern 

 agriculture is to sweeten sour soils. A soil that 

 contains free acid is "sour," or acid. Such soils, 

 though they may be rich in plant food, usually 

 produce inferior crops ; but if this acid is neutralised 

 by adding lime, they become productive. There 

 are thousands of acres of sour soils in the United 

 States, notably in Rhode Island, Massachusetts, 

 New Hampshire, Connecticut, New York, Illinois, 

 Maryland, Virginia, and Alabama. The applica- 

 tion of lime to such soils may do more to make them 

 productive than the use of large amounts of com- 

 mercial fertilisers. 



THE SOILS THAT NEED LIMING 



Contrary to the popular notion, soils containing 

 a large amount of humus are not more likely to be 

 sour than upland soils. Soils are sour because the 

 rocks from which they were formed were deficient 

 in lime. Sour soils are very apt to have an abun- 

 dance of sorrel or "sourgrass. ' When this plant 

 comes into the field and crowds out other plants, it 

 is a fairly reliable indication that lime is needed, 

 although sorrel often grows well on sweet soils. 



Practically all farm crops, except watermelon, 



