CHAPTER IX. 



SOIL ANALYSIS AND ITS INTERPRETATION. 



WHEN an agricultural chemist is asked to analyse a soil he is 

 expected to give some information about the crops to which 

 it is best suited, and the manures that must be applied ; he 

 has, therefore, a much more complex problem than the 

 mineralogical or geological chemist who simply has to report 

 on the actual constituents he finds. It has been shown in the 

 last chapter that the vegetation relationships of soils are not 

 determined solely by the nature of the soil, but also by its 

 position, subsoil, climate, and other circumstances, so that it 

 is manifestly impossible for the chemist to make a satisfactory 

 report on a sample of soil on the basis of analytical data only. 

 He cannot even give a complete account of the soil itself, 

 since he has no method of estimating the compound particles 

 on which the water and air supply, the temperature and the 

 cultivation properties depend, but he can only get at the ulti- 

 mate particles out of which they are built. 



Soil analysis is, therefore, restricted to: (i) comparisons 

 between soils, showing which are fundamentally identical and 

 in what respects others differ ; (2) the tracing of such corre- 

 lations as exist between the chemical and physical properties 

 of the soils of a given area and the crops and agricultural 

 methods generally associated with them. In order to carry 

 out either of these satisfactorily it is necessary to make a 

 systematic soil survey, a task that is certainly laborious but 

 by no means impossible, since each agricultural chemist usually 

 confines his attention to a definite region a county or so 

 and is not called upon to deal with outside soils. 



In planning a soil survey it must be remembered that the 



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