MANURES. 237 



a variety of complex circumstances that any figures given 

 with reference to its composition can only be regarded 

 as approximations. Its constituents are made up of (a) 

 the solid excreta, (b) the liquid portion or urine and (<?) 

 the material employed as litter. It is evident therefore 

 that its ultimate value will largely depend on the pro- 

 portion in which these three different classes of substances 

 are present. 



THE SOLID EXCRETA. 



The solid excrements of the different farm animals vary 

 very much in composition, that is to say, in the propor- 

 tion of nitrogen, phosphoric acid and potash which they 

 contain. For example, the solid excrement of the sheep 

 differs very considerably from that of the bullock and so on. 



Other conditions, however, influence the composition of 

 the excrement of any class of animal. A mere consider- 

 ation of the nature of the solid portion will show that this 

 must of necessity be the case. Roughly speaking, it is 

 the undigested part of the food, that is to say that part of 

 the food which has passed through the digestive system 

 of the animal without being acted upon to any extent. 

 Consequently, the nature of the food influences the com- 

 position of the resulting manure. We cannot therefore 

 expect manure of equal value from an animal fed on a 

 poor diet as from one fed on richer food, other conditions 

 being equal. Thus, the value of the manure produced in 

 Egypt by animals fed on a dry diet consisting of beans 

 and straw is greater, weight for weight, than that produced 

 when feeding; on green berseem. In other words the more 



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