CHAPTER TWELVE 



SUPPLYING SOIL NEEDS 



What Nature asks, that Nature also grants. 



JAMES RUSSELL LOWELL 



Soil needs AN Illinois farmer, who had spent his life in an un- 

 successful attempt to raise profitable crops, wept when 

 he was shown that the addition of one fertilizer (potash) 

 would have made his fields fertile. Every farmer should 

 find out whether or not his land is naturally lacking in 

 any of the essential plant-food materials and how he 

 can remedy such lack (Fig. 133). He should also find 

 out what necessary elements his fields are losing and how 

 he can replace the loss (Chapter Four) . 



Commercial The three elements most commonly needed as fer- 

 tilizers are, as we have already seen, nitrogen, phos- 

 phorus, and potassium. These are all found in manure. 

 They are often supplied, either singly or mixed, by 

 fertilizer dealers, who get them, not from manure, but 

 from certain minerals or from slaughter-house refuse. 

 When supplied in this way they are called " commercial 

 fertilizers," and a mixture of all three of these necessary 

 plant foods is called a " complete " fertilizer. (Exp. i.) 

 TWO other plant-food elements, calcium (contained in 

 lime) and sulfur, are sometimes necessary. 



Commercial Nitrogen, phosphorus, and potassium are most corn- 

 names monly used in compounds known as " nitrates," " phos- 

 phates " (or " phosphoric acid"), and " potash"; and 

 fertilizers containing the three elements are often loosely 

 referred to by these names of their compounds. 



To show how many pounds per acre of the three 



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