AGRICULTURE 



General principles must be adapted to suit 

 the varying conditions of soil and climate, and 

 also care must be exercised in mixing to see 

 that no chemical action takes place which 

 minimises the value of the manure. The 

 most important constituents of soils are- 



Silica 

 Alumina 

 Lime 

 Potash 



Soda 

 Iron 



Phosphoric acid 

 Sulphuric acid 



Chlorine 



Nitrogen 



Magnesia 



These are present in varying degrees ac- 

 cording to the nature of the soil. The chief 

 manures are Green manures, either ploughed 

 in or fed off, Farmyard manure, Artificial 

 manure. 



Farmyard manure is undoubtedly the most 

 important of these, because if properly pre- 

 served it contains all the constituents removed 

 from the soil by the crop. And it has an 

 advantage over artificial manure in that it 

 affects the soil mechanically as well as chemi- 

 cally, by reason of the large quantity of 



