THE FERTILIZING VALUES OF FEEDINGSTUFFS 321 



case the nitrogen of the protein molecule is split off and ex- 

 creted through the urine. Also small amounts of mineral 

 matter, including potassium and phosphorus, are excreted 

 in the urine, while larger amounts are excreted in the feces. 

 In other words, all the nitrogen, potassium, and phosphorus 

 of the ration which is not permanently stored in the body 

 (or used for milk production) is ultimately excreted and may 

 be returned to the soil for fertilizer. Also, all the undigested 

 organic matter of the feces may be returned to the soil to 

 supply the humus. 



The amount of manure, both Hquid and sohd, is quite 

 variable for the different farm animals under different con- 

 ditions. According to Van Slyke ^ the amounts of manure 

 produced for 1000 pounds of live weight by the different 

 farm animals in one year are as follows : 



Of primary importance in this connection is a knowledge 

 of the proportion of each fertilizing constituent of the feed 

 which may be recovered in the manure. At the Ilhnois 

 Experiment Station,^ Mumford, Grindley, Emmett, and Bull 

 fed eight two-year-old steers for a period of 37 weeks. The 

 consumption and excretion of nitrogen and phosphorus 



Fertilizers and Crops," p. 294. 



Unpublished data. 



