138 SOILS AND FERTILIZERS 



The amount of nitrogenous waste matter in the 

 urine is nearly the same whether an animal be gaining 

 or losing in flesh, consequently the urine is more con- 

 stant in both composition and quantity than the solid 

 excrements. 



The amount and composition of the solid excre- 

 ments vary with the amount and kind of food con- 

 sumed. If the food is indigestible the solid excrements 

 contain a larger part of the nitrogen as indigestible 

 protein. When an animal is properly supplied with 

 food for all purposes, normal conditions exist, and the 

 amount of nitrogen voided in the liquid and solid ex- 

 crements is equal to that supplied in the food con- 

 sumed, except in the case of growing and milk pro- 

 ducing animals. 



Experiments at the Rothamsted station have shown 

 that from 57 to 79 per cent, of the total nitrogen in 

 the food of farm animals is voided in the liquid ex- 

 crements, and from 16 to 22 per cent, is voided in the 

 solid excrements. Nearly all of the mineral elements 

 in the food is voided in the excrements, less than four 

 per cent, being retained in the body ; in the case of 

 milk cows about 10 per cent, of the ash in the food 

 is recovered in the milk. 



172. Manural Value of Foods. The manurial 

 value of a fodder is determined by the amount of nitro- 

 gen, phosphoric acid, and potash present in the 

 material. Timothy hay, for example, has a manurial 

 value of $5.30 per ton, which means that if the nitro- 



