FERTILIZERS 1 1 



SOMETHING ABOUT SOILS. 



13. Of more than seventy elements known to 

 chemistry, fourteen have been found to be essential 

 to plant life. Ten of these are soil derived, and four 

 are derived from the air : 



Air Derived. Soil Derived. 



Carbon Calcium 



Oxygen Silicon 



Hydrogen Iron 



Nitrogen Magnesium 



Manganese 

 Sulphur 

 Chlorine 

 Sodium 

 Potassium 

 Phosphorus 



These fourteen elements, in varying portions, are 

 peculiar to all plants so far as different species have 

 been examined. 



14. All soils, for convenience, may be considered 

 as composed of various portions of: 



Rock Powder } f Sand 



Silt I j 



Clay > or simply Clay 



Humus ) | 



Plant food j" Humus 



Sand is rock powder and may or may not contain 

 silt. Clay is a chemical compound and a very im- 

 portant element of soils, as it retains large amounts 

 of moisture. If too abundant, the soil is intractable 



