CHAPTER XXI 

 THE FERTILIZING VALUES OF FEEDINGSTUFFS 



In addition to the direct products of feeding, such as meat 

 or milk, the feeder also has the manure as a more or less 

 valuable by-product. It is not onh' of interest but also of 

 practical value to know the fertilizing value of manure from 

 the various feedingstuffs, and the factors which may affect 

 its value. 



Ordinarily four mineral elements must be suppUed or 

 made available to conserve the fertihty of the soil; viz., 

 nitrogen, potassium, phosphorus, and calcium, all of which 

 are contained to a certain extent in the excreta of our farm 

 animals. However, inasmuch as the amount of calcium 

 in manure is small, only the nitrogen, potassium, and phos- 

 phorus w\\\ be considered in this connection. In addition to 

 the mineral elements, a certain amount of organic matter 

 must be present in the soil to assist in making some of the 

 mineral elements available and to improve the physical con- 

 dition of the soil. 



The principal source of the fertilizing constituents of the 

 excreta is, of course, the feed of the animal. It has already 

 been shown that the animal does not chgest all the ration, 

 any undigested material passing off in the feces. It also 

 was stated that, if a surplus of protein is fed above the de- 

 mands of the body for repair, growth, and milk production, 

 the excess is used for energy or fat production. In either 



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