CHAPTER VI 



THE CHEMICAL ANALYSIS OF SOILS 



Necessary Conventions as to the Material to be Analysed 

 Methods Adopted Interpretation of Results Distinction 

 between Dormant and Available Plant Food Analysis of 

 the Soil by the Plant Determination of "Available" Phos- 

 phoric Acid and Potash by the Use of Weak Acid Solvents. 



The chemical analysis of a soil aims at ascertaining the 

 amount which the soil contains of the various elements 

 necessary to the nutrition of the plant, with a view of 

 either making good the general deficiencies of the soil or 

 of adjusting the supply of plant food to such special 

 requirements of a particular crop as may have been 

 indicated by previous experiment. 



The analysis of plants grown under ordinary con- 

 ditions shows that a comparatively limited number of 

 elements enter into their composition ; in the main they 

 are composed of water and certain combustible com- 

 pounds of carbon, hydrogen, nitrogen, and sulphur. In 

 the mineral residue that is left after the combustible 

 material has been burnt off, will be found potassium, 

 sodium, calcium, magnesium, and a little iron among 

 bases ; and phosphorus, chlorine, sulphur, and silicon 

 among non-metallic elements. Manganese in very small 

 quantities occurs in nearly all plants : other elements 

 like lithium, zinc, copper, are found in traces under 



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