ELEVENTH ANNUAL YEAR BOOK— PART VIII 411 



6 to 8 weeks, she will not require very much, if any, grain if she has all 

 the silage and clover hay she will consume. For the purpose of illustrat- 

 ing what I wish to bring out. I have not permitted the cow any pasture, 

 but have fed her prepared feeds and it is fair to say that the amount of 

 feed she would need in a year would be about 6 tons of silage, 2 tons of 

 clover hay, 1,000 pounds of corn stover, 1,500 pounds corn chop, 1,000 

 pounds of bran and 300 pounds of oil meal. It is common knowledge 

 that a certain amount of fertility has been taken from the soil to produce 

 these feeds and that the soil does not contain an unlimited supply of some 

 of these elements. 



Dr. Hopkins of the University of Illinois, the best soil authority in the 

 country, says that most Illinois soils lack in phosphorus and nitrogen, 

 but that they are well supplied with all the other elements. It is gener- 

 ally held that there are 3 important elements of plant food, namely, nitro- 

 gen, phosphorus and potash. It will be interesting, I am sure, to know 

 just how much of these elements is required to produce the amount of 

 feed that I have assumed the cow r w r ould eat in producing 8,000 pounds of 

 milk testing 3.8 per cent and maintain her body. It is not difficult now 

 to obtain tables showing the amount of fertilizing elements in 1,000 pounds 

 of the different feed stuffs and so I have calculated and given in the fol- 

 lowing table the amount of nitrogen, phosphorus and potash taken from 

 the soil to produce the feed which a cow will consume in a year. The 

 following table shows the different amounts of elements in the different 

 amounts of feeds: 



Lbs. Lbs. Lbs. 



Name and Amt. of Feed Nitrogen Phosphorus Potash 



6 tons corn silage 52 13 44 



2 tons clover hay 80 22 - 75 



1,000 lbs. corn stover 6 4 11 



1500 lbs. corn chop 24 10 8 



1000 lbs. bran 25 27 15 



300 lbs. oil meal 20 6 4 



Total 207 82 157 



In other words, the soil must give up 207 pounds nitrogen, 82 pounds 

 phosphorus and 157 pounds of potash to produce feed enough to sustain 

 an animal making 8,000 pounds of 3.S per cent milk a year. Part of these 

 elements is used for the maintenance 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 



Fertility returned in manure 155 62 117 



Fertility used in milk 51 20 40 



