224 THE CHEMISTRY OF THE FARM 



Under these circumstances the return in harley from 

 the nitrogen in the food is about 20 per cent, of that 

 yielded by the nitrogen of nitrate of sodium. This 

 return rises to 32 per cent, if the effect of the residue 

 of the farmyard manure during fifteen subsequent years 

 is taken into the account. 



Lawes and Gilbert, in their estimates of the manure 

 value of foods supplied to fattening animals, have first 

 deducted the nitrogen, phosphates and potash which 

 they estimate are retained by the animal, and then 

 reckoned one-half oi the remaining nitrogen, phosphates 

 and potash at the current values of these substances in 

 artificial manures. These estimates are more probably 

 too high than two low. 



The feeding of animals on the land is a plan which 

 has many advantages, and if carried out under favour- 

 able circumstances will yield the best return from the 

 manure constituents of the food ; the distribution of 

 the manure is apt, however, to be irregular, and in 

 autumn or winter some loss may occur from rain 

 and drainage. It is generally, however, not possible 

 to consume more than a small part of the food of the 

 farm in this way. The use of litter, and the prepara- 

 tion of farmyard manure, becomes, therefore, a neces- 

 sity. Farmyard manure should always be prepared 

 under cover. The precautions to be taken for diminish- 

 ing the losses which it suffers have been already noticed 

 on p. 51. 



