THE EARTH'S BOUNTY 



plant food it may contain. The chief factor 

 governing the physical condition of the soil 

 is the amount of humus or decaying vegetable 

 matter it contains. It is in this connection that 

 cover crops may be made to serve so impor- 

 tant a purpose. 



Cover crops are of two classes: Legumes, 

 which have the power of gathering nitrogen 

 from the air, so that when they are plowed 

 under and decay, the soil is actually richer in 

 nitrogen than it was before; and the non- 

 nitrogen-gathering plants, which, when they 

 become incorporated with the soil, leave it 

 little richer in plant food than it was before, 

 though the presence of the decaying vegetable 

 matter thus added to the soil improves its 

 physical condition and makes it more produc- 

 tive. 



Of the leguminous cover crops, the various 

 kinds of clover are, perhaps, of greatest value, 

 though the question of value is somewhat de- 

 pendent upon location and other conditions. 

 Other crops of this class, frequently used for 



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