168 Fertilisers [pt.iii 



solid and liquid excretions from the animals together with 

 the litter. It is the oldest and the commonest of all the 

 fertilisers : indeed in the "sixties " and "seventies" beasts 

 were kept on the farm solely for the value of the manure 

 they made, and the practice still persists to some extent. 



About half of the bulky food supplied to the animal 

 (hay, straw, etc.) and nearly all the concentrated food 

 (corn, cake, etc.) can be broken down by the digestive 

 fluids in its body; the remainder cannot, and simply 

 passes out as solid excreta or faeces. The digested por- 

 tion enters the circulation and is used by the animals, 

 most of the nitrogen and potash then finds its way into 

 the urine. The compounds in the urine thus represent 

 the easily decomposed part of the food, and in the soil 

 they readily change to ammonia and other useful sub- 

 stances. On the other hand the solid excreta, which 

 could not be broken down in the body, prove somewhat 

 resistent in the soU. Hence the urine is the most valu- 

 able part of the manure. 



The richest manure is therefore that which contains 

 the most and the richest urine. Now the richness of the 

 urine clearly depends on the food, for, as we have just 

 seen, the urine gathers up most of the digested nitrogen; 

 hence the more digestible nitrogen the food contains, the 

 richer will be the manure 'produced. Concentrated foods 

 like cake, which are rich in digestible nitrogen, therefore 

 improve the dung. But it does not follow that the 

 richest cake gives the richest manure: richness of cake 

 depends on the oil present, while richness of the manure 

 depends on the nitrogen. A linseed cake containing 

 7 per cent, of oil gives richer manure than a more costly 

 cake containing 10 per cent., and decorticated cotton 

 cake gives a richer manure still. 



