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 enters 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 



