114 ILLINOIS STATE DAIRYMEN'S ASSOCIATION. 



In other words, the soil must give up 207 pounds nitrogen, 

 82 pounds phosphorus and 157 pounds potash to produce feed 

 enough to sustain an animal making 8,000 pounds of 3.8 per 

 cent milk a year. Part of these elements is used for the main- 

 tenance of the animal, some for the making of milk and the 

 rest is returned to the soil in the form of manure. For practical 

 purposes, it is safe to say that 25 per cent of the elements is 

 used in the manufacture of milk and the other 75 per cent is used 

 by the animal and returned in the manure. Upon this basis we 

 may make the following table : 





Lbs. 



Lbs. 



Lbs. 





Nitrogen. 



Phosphorus. 



Potash. 



ility returned to manure 



.... 155 



.62 



117 



ility used in milk 



.... 5i 



20 



. 40 



If it were possible to preserve all the elements in the ma- 

 nure and if leeching and fermentation could be prevented, it 

 would be possible to return the above amount of fertility to the 

 land, but every practical man knows that this is not possible 

 under ordinary conditions. It has been found by investigators 

 that if a person returns 60 per cent of the fertility in the ma- 

 nure provided by the cow, he is doing splendid work. If butter- 

 fat is sold from the farm and the skim-milk returned for feed- 

 ing, we get much of the fertility back. In the feeding of skim- 

 milk there is also loss and we cannot expect to return more than 

 60 per cent of the fertility or the elements required to make the 

 milk, for there is a waste in handling skim-milk. The calf or 

 animal to which it is fed takes some of the elements for growth 

 and the fertility in the manure from the animals gives up some 

 of its fertility to leeching and fermentation. If we assume that 

 60 per cent of the fertilizing elements in the manure and skim- 

 milk is returned to the land, we get the following table: 



