1 6 AGRICULTURE. [en. 



importance. It is never found in the soil in large 

 proportion : in our richest soils it barely reaches .5 per 

 cent., that is, in 100 Ibs of soil there is rarely as much as 

 \ Ib. of phosphoric acid. 



26. We here give a list of the more important bodies 

 usually found in cultivated soils, so that the student 

 may have the opportunity of making himself ac- 

 quainted with their properties from his textbook on 

 chemistry. 



INORGANIC MATTERS IN SOILS. 



Silica. 



Phosphoric acid. 

 Carbonic acid. 

 Sulphuric acid. 

 Chlorine. 



Alumina. 



Lime. 



Ammonia. 



Potash. 



Soda. 



Magnesia. 



Oxide of iron. 



27. In addition to the inorganic matters of soils we 

 have a second group of substances existing in them as 

 organic matter. This matter consists of substances 

 which may have grown under the influence either of 

 vegetable or of animal life, and have consequently 

 been organized as part of some living plant or animal. 

 The process of decay in the soil brings these 

 vegetable or animal remains into such a condition that 

 they again become available for yielding nourishment 

 to vegetation. Any inorganic matter which had 

 formed part of the structure of the vegetable or ani- 

 mal, becomes an addition to the mineral matter of the 

 soil, whilst the organic matter forms a series of sub- 

 stances which practically yield to the soil 



Carbon, with the elements of water (Oxygen and 

 Hydrogen), in various forms of combination ; 

 also 



Ammonia and other nitrogenous matters. 



28. The inorganic and organic substances in the 

 soil constitute a very large number of bodies, but by 

 the aid of chemical analysis the composition of soils 



