THE COMPOSITION OF FERTILE AND BARREN SOILS. 



ANALYSES OF CLAY SOILS, BY DR. VOELCKER. 



A fertile soil is one that contains all the substances which our 

 cultivated plants require for coming to perfection which con- 

 tains them in abundance, and in such a state that they are readily 

 assimilated by the growing plants. I am speaking chemically, 

 not forgetting that the physical condition of the soil greatly in- 

 fluences its agricultural capabilities ; but, not having time now to 

 discuss the physical properties, I pass them by, observing that, 

 although I am a chemist, I attach very great importance to the 

 physical condition of soils. 



To ascertain the character of good soils, we cannot do better 

 than examine those remarkable for their fertility. Such soils 

 have been carefully analysed, and I will direct your attention to 

 the above diagrams, which may illustrate the subject. On the 

 diagram headed " loamy soils," you have two soils from the 

 Lothians, remarkable for producing large crops of wheat. Then 

 you have, under the head " clay soils," the analyses of three 

 different soils, one from the valley of Evesham, in Gloucester- 

 shire, likewise remarkable for their fertility. You observe that 

 a great number of substances enter into the composition of these 

 soils. You find silica, which is the chief constituent of all soils. 

 We don't always find it in an uncombined state, in which it is 

 familiar to you under the name of " sand " this being a form of 

 silica; but we find the same substance in combination with 

 alumina, constituting the chief ingredient in clay soils, and in 

 this form it is called a silicate of alumina : or, in ordinary lan- 

 guage, sand and clay are two chief component parts of soils. 

 You will also find lime amongst the component parts of those 

 (fertile) soils not in very large quantities, still in quantities 

 sufficient to meet the needs of agricultural crops. Few soils are 



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