HYDRAULIC METHOD 91 



be standardised for any size of particle. To bring the elutriator 

 into line with the settling process, the fractions from the latter 

 may be placed in the apparatus, and the water-pressure necessary 

 to carry them over noted. 



CHAPTER IX 



Chemical Analysis of Soil 



The chemical analysis of a soil is carried out with a view to 

 ascertaining what quantities of the plant nutrients are present, 

 so that any actual deficiencies can be made good, or the amounts 

 so altered as to meet the requirements of particular crops. 



The most important constituents estimated are the carbonates 

 (representing the "available basicity" of the soil), the organic 

 matter, nitrogen, phosphorus, potassium, calcium, and magnesium. 

 Of lesser importance are sodium, iron, aluminium, manganese, 

 chlorine, and sulphur (as sulphate). 



69. Sampling. 



The "air-dried fine earth" passing through the 3 

 mm. sieve is prepared as previously described for the 

 mechanical analysis (64). About 100 grams of this 

 material are then further broken down in a steel 



