CLOVER AS SOURCE OF CARBON. 137 



one-year-old roots and stubs contain the large quan- 

 tities of fertilizing substances previously named; 

 and when plowed in, furnish to the next crop a 

 liberal supply of food in a most digestible form. 

 Thus, clover helps along the crop or crops following 

 it; of course, at the expense of the fertility of the 

 soil; and this again makes it plain why farmers like 

 to plant such crops as corn and potatoes on young 

 clover sod. 



Besides the three elements of plant food which 

 have a quotable money value, clover, like other 

 plants, collects and stores up carbon, the supply 

 being drawn largely, and if need be wholly, from 

 the air. By growing clover even for hay we can fill 



the soil with carbonaceous matter just 

 ^^TcaJboT''^ as effectively as if we cart coarse stable 



manure to the fields and plow it in. 

 It is a comparatively easy matter to supply the 

 soil with the needed minerals. Muriate of potash, 

 kainit, etc., are cheap enough sources of the one; 

 phosphatic rock, phosphate meal, bone black, etc., 

 of the other. These alone, however, if ever so 

 super- abundantly present in the soil, do not make it 

 rich. Such soil may possibly be inactive, without life, 

 for the lack of the needed plant food, nitrogen, and 

 of the mechanical action of carbon. Mtrogen also 

 can be provided, either together with phosphoric 

 acid by application of bones, fish, etc., or alone, by 

 application of sulphate of ammonia, or of nitrates, 

 etc., although this may be at an expense far too 

 large to make it profitable for common farm crops. 

 Thus we can feed a worn-out soil with the substances 

 generally named "chief elements of plant food." 

 In spite of greatest liberality, however, the soil may 

 remain sluggish, and refuse to respond with thrifty 



