CHAPTER V 

 MANURING AND FERTILIZING 



L,AND is manured and fertilized either to increase or to 

 maintain its crop-producing power. Whether this is 

 secured by the direct effect of the chemical ingredients in 

 the manure or fertilizers, or by their influence upon the 

 physical properties of the soil, or both, is an unsettled 

 scientific problem, but all agree that under certain con- 

 ditions the addition of manures, fertilizers, and water 

 to the soil is profitable. Whether it will be profitable 

 on a particular farm or field, and the manure, fertil- 

 izer or combination of fertilizers which will be most 

 profitable to use, are questions the grower must settle 

 for himself by trial. No chemical examination of the 

 soil yet conducted has shown why two soils, apparently 

 identical in chemical composition, should not produce 

 similar yields of crops. Experience has shown that 

 the chemical composition of the soil is no guide to its 

 crop-producing power. Hence, all that can be given in 

 this chapter is to submit mixtures of fertilizers that 

 are used and the r61e the different important ingre- 

 dients are believed to play in the plant economy. 



In addition to water, which is treated elsewhere, 

 four elements are frequently applied in various chem- 

 ical forms as fertilizers nitrogen, phosphorus, potas- 

 sium, and calcium. The potato through its life re- 

 quires liberal supplies of the first three of these elements, 

 and its behavior in regard to these is similar to that of 



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