FARMYARD MANURE 179 



a farm, as to how much farmyard manure 

 should be brought back to the holding, so 

 that its fertility may be maintained. 



Of the constituents of the food, the most 

 important, from the point of view of manur- 

 ing, is the nitrogen, of which, in the case of 

 fattening cattle, about 96 per cent, reappears 

 in the form of fertilizing material, some 23 

 per cent, being in the solid form in the 

 dung, and about 73 per cent, in solution in 

 the urine. The balance, namely 4 per cent., 

 is stored up in the animal's tissues in the 

 form of hair, flesh and bone. The nitrogen 

 of the urine is by far the most active and 

 valuable, hence the reason that it is so 

 desirable to prevent the loss of liquids. In 

 the case of a milk cow, however, where milk 

 is sold off the farm, only about 75 per cent, 

 of the nitrogen reappears in the manure, a 

 large proportion of the balance finding its 

 way into the milk in the form of casein and 

 albumen. In the case of growing animals, 

 also, a smaller proportion of the nitrogen 

 will reappear in the excreta, though the 

 proportion so returned is greater than in 

 the case of milk cows. As regards the 

 phosphates and potash, a very small quantity 

 is retained even by animals increasing in 

 weight, more, however, by young growing, 



