MANURES 



97 



Consequently manures are usually valued according bo the 

 quantities of these ingredients present in them, although in 

 many cases other constituents may exert an important in- 

 fluence upon the soil. 



Farm -yard Manure.— This, formerly the only important 

 manure, is still the most popular. 

 It consists essentially of : 



1. The excreta of the animals of the farm. 



2. The litter and waste food. 



The exci'eta of animals consists of undigested parts of their- 

 food, together with various waste products from the tissues 

 of their bodies. The composition of the excrement varies 

 greatly, some of the factors determining it being : 



1. The kind of animal. 



2. The character and quantity of the food. 



8. Whether the animals are growing, fattening, work- 

 ing, or milking. 



Considerable discrepancies are therefore not surprising in 

 analyses of the excreta of animals. 



The following table gives the average proportions of the 

 chief manurial ingredients found in the excreta of various 

 animals, according to American analyses : — 



