FARM- YARD MANURE. Ill 



often these are particularly rich in nitrogen, potash, and phos- 

 phates, and of those eaten by the animals of the farm only a 

 portion is voided as excrement the animal has to build up its 

 body out of the materials supplied in its food. This consumes 

 large quantities of nitrogen and phosphates particularly. 

 Then, too, the production and sale of milk removes large 

 quantities of manurial ingredients from the soil, and though 

 butter contains little other than carbonaceous material, cheese 

 is highly nitrogenous. 



It will be advisable to briefly consider the chemical nature 

 of the raw materials which go to form the average farm -yard 

 manure. The ingredients of this substance may be first 

 divided into two groups : 



I. Animal excrements, both solid and liquid. 



II. Litter and waste food materials. 



The excreta of animals consist of the undigested parts of the 

 food consumed by them, together with excretions consisting of 

 effete matters resulting from waste of their tissue and the 

 water drunk by them w r hich they have not exhaled as vapour 

 from their lungs or skin. 



The chemical nature and the total quantity of the excreta 

 depend very largely upon the character and quantity of the 

 food supplied. This is especially true of the solid portion, 

 which consists mainly of the undigested matter of the food, 

 but contains also certain products derived from the digestive 

 fluids, e.g., the bile, pancreatic juice, &c. 



The liquid portion of the excreta, on the other hand, consists 

 mainly of water, holding in solution substances produced by 

 the wear and tear of the muscles, &c., of the animal, these 

 waste products being separated from the blood stream of the 

 animal by appropriate organs. Of course these matters origi- 

 nally came from the food, but they are not the immediate 

 products, as are most of the constituents of the solid excreta. 



Both the liquid and solid portions of the excreta contain 

 large quantities of substances of little or no value as fertilisers 

 directly ; but, inasmuch as they readily undergo putrefactive 

 changes resulting in the liberation of carbon dioxide and other 

 gases and the production of bulky carbonaceous substances 



