Methods used to determine water content in soil

 Methods used to determine water content in soil

a). Pycnometer Bottle Method 

w =( M2-M3)/(M3-M1)×(G-1/G)×100

M1 = Mass of empty pycnometer bottle 

M2 = Mass of empty pycnometer bottle + Soil

M3 = Mass of empty pycnometer bottle + soil + water

M4 = Mass of empty pycnometer bottle + Water only

The method is used for coarse soils only

 

b). Oven Drying Method

%w = (Mw/Ms)×100

%w = (M2-M3)/( M3-M4) ×100

M1 = Mass of empty container 

M2 = Mass of Empty container 

Oven Drying (24 hours @ 105°C-100°)

M3 = Mass of empty container + dry soil 

i. This method is the most accurate method. 

ii. For inorganic soils, the temp should be 105-110°C

iii. For the organic soils, the temp should be 60°C

iv. For the soil containing Gypsum (CaSO.2H2O), the temp should not be more 

than 80°C

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c). Sand Bath Method

M1 = Mass of empty container 

M2 = Mass of empty container + soil

After heating the soil @ 30 min to 45 min 

M3 = Mass of empty container + dry soil

%w =( M2-M3 )/ (M3-M1)×100

I. This method given the rough value of water content. 

II. There is no control of temperature in this method.

III. This method is used for inorganic soils.

d) Alcohol method

Methylated Spirit

 It gets evaporated when it comes in contact with oxygen

M1 = Mass of empty container 

M2 = Mass of empty container + Soil 

Add methylated spirit 

M3 = Mass of empty container + Soil 

%w =( M2-M3 )/(M3-M1)

i) This method is used for inorganic soils.

ii). this method given fairly accurate results

e). Calcium carbide method.

(CaC2) 

CaC2+H2o -------> Cao +C2H2 

I. 5-10min∴ this is the least time consuming method 

II. It can be used for any type of soil. 

III. The results are fairly accurate

IV. This is also a field method 

f). Radiation method

I. This method is an on –site or in-situ method 

II. in-this method, the collection of sample is not Required

III. This method is very costly method. And have uneconomical 

IV. In this method, the water molecules present in soil gets disturbed. 

V. In this method, the results are higher than expected. 

In this, neutrons get emitted & react with water, then there is loss of energy. Then 

detector detects this

g). Torsion Balance method

 It is used for fine soil.