CHAPTER IV 



STERILE SOILS 



" Agri non omnes frugiferi sunt." — Cicero. 



" The exhaustion of soil by plants means their having consumed 

 all the nutritive particles that it contains." — Lindley. 



Although the fertility of a soil is greatly 

 influenced by its physical properties, as already 

 stated, but independently of these conditions, the 

 fertility depends upon the chemical constituents of 

 which the soil is composed. All cultivated soils 

 should contain the necessary foods for plant- 

 nutrition and growth. 



It is frequently argued that most soils contain a 

 plentiful supply of the minor constituents found in 

 the ashes of plants ; therefore, it is unnecessary to 

 add the minor plant-foods to the soil. We shall 

 see that this is a great mistake. In most soils the 

 minor constituents are to be found in the form of 

 insoluble compounds, which are only partially 

 rendered soluble during the production of the 



