54
4.5.1 pH
Main materials required: pH meter, soil sample,
buffer tablets, beaker, stirrer, DW
4.5.1.1 Procedure
1. 20 g of powdered soil sample be taken in a
100-ml beaker.
2. 40 ml of DW be added to it.
3. The suspension be stirred at regular intervals
for 30 min.
4. The electrodes of the electronic digital pH
meter be dipped into the supernatant (suspension) just above the soil in the beaker, and care
be taken, so that the electrode does not touch
the soil below the supernatant.
5. The pH value be recorded.
6. The suspension be stirred well every time just
before the electrodes are immersed.
The data be recorded in the following table:
Locality:
Date:
Time:
Sample no.
Soil pH
Average soil pH:
4.5.2 Conductivity
Main materials required: conductivity meter,
beaker, KCl, DW, soil sample
4.5.2.1 Procedure
1. 20 g of powdered soil sample be taken in a
100-ml beaker.
2. 40 ml of DW be added to it.
3. The suspension be stirred at regular intervals
of one hour. Alternatively, the soil suspension
in the beaker be kept on an electrical shaker
for one hour.
4. The conductivity cell of the electronic digital conductivity meter be dipped into the
supernatant (suspension) just above the soil
in the beaker, and care should be taken so
that the electrode does not touch the soil
below the supernatant.
5. The conductivity value be recorded.
6. The suspension be stirred well every time just
before the electrodes are immersed.
The data be recorded in the following table:
Locality:
Date:
Time:
Sample no.
Conductivity (micromhos/cm)
Average value of conductivity (micromhos/cm):
4.5.3 Organic Carbon (OC)
4.5.3.1 Method of Walkley and Black
Walkley and Black (1934) had devised a method
for the estimation of OC in soils.
Principle
The OC is estimated by titration, in which the
organic carbonaceous matters are oxidised by a
known volume of a standard dichromate solution
and then titrating back the volume of dichromate
left unused with a standard solution of ferrous
(ammonium) sulphate using diphenylamine as
indicator.
Main Materials Required
1(N) Potassium dichromate (AR) solution: 49.4 g
of AR grade K 2 Cr 2 O 7 be dissolved in 1 l of DW.
0.5 (N) (approx.) ferrous ammonium sulphate:
196 g of the hydrated salt be dissolved in 1 l of
DW containing 20 ml of H 2 SO 4 .
Diphenylamine indicator: 0.5 g of diphenylamine
indicator be dissolved in 20 ml of DW and
100 ml of conc. sulphuric acid.
Concentrated sulphuric acid (sp.gr. 1.84) containing 1.25 % silver sulphate.
Orthophosphoric acid (85 %).
Required glasswares like beakers, conical flasks,
volumetric flasks, measuring cylinders,
burettes, pipettes, test tubes.
Procedure
1. 1.0 g of the soil (ground and sieved through
0.2-mm sieve) be taken in a dry 500-ml conical
flask.
4 Lentic Soil or Mud (Physico- chemical Characteristics of Soil)
4.5.1 pH
Main materials required: pH meter, soil sample,
buffer tablets, beaker, stirrer, DW
4.5.1.1 Procedure
1. 20 g of powdered soil sample be taken in a
100-ml beaker.
2. 40 ml of DW be added to it.
3. The suspension be stirred at regular intervals
for 30 min.
4. The electrodes of the electronic digital pH
meter be dipped into the supernatant (suspension) just above the soil in the beaker, and care
be taken, so that the electrode does not touch
the soil below the supernatant.
5. The pH value be recorded.
6. The suspension be stirred well every time just
before the electrodes are immersed.
The data be recorded in the following table:
Locality:
Date:
Time:
Sample no.
Soil pH
Average soil pH:
4.5.2 Conductivity
Main materials required: conductivity meter,
beaker, KCl, DW, soil sample
4.5.2.1 Procedure
1. 20 g of powdered soil sample be taken in a
100-ml beaker.
2. 40 ml of DW be added to it.
3. The suspension be stirred at regular intervals
of one hour. Alternatively, the soil suspension
in the beaker be kept on an electrical shaker
for one hour.
4. The conductivity cell of the electronic digital conductivity meter be dipped into the
supernatant (suspension) just above the soil
in the beaker, and care should be taken so
that the electrode does not touch the soil
below the supernatant.
5. The conductivity value be recorded.
6. The suspension be stirred well every time just
before the electrodes are immersed.
The data be recorded in the following table:
Locality:
Date:
Time:
Sample no.
Conductivity (micromhos/cm)
Average value of conductivity (micromhos/cm):
4.5.3 Organic Carbon (OC)
4.5.3.1 Method of Walkley and Black
Walkley and Black (1934) had devised a method
for the estimation of OC in soils.
Principle
The OC is estimated by titration, in which the
organic carbonaceous matters are oxidised by a
known volume of a standard dichromate solution
and then titrating back the volume of dichromate
left unused with a standard solution of ferrous
(ammonium) sulphate using diphenylamine as
indicator.
Main Materials Required
1(N) Potassium dichromate (AR) solution: 49.4 g
of AR grade K 2 Cr 2 O 7 be dissolved in 1 l of DW.
0.5 (N) (approx.) ferrous ammonium sulphate:
196 g of the hydrated salt be dissolved in 1 l of
DW containing 20 ml of H 2 SO 4 .
Diphenylamine indicator: 0.5 g of diphenylamine
indicator be dissolved in 20 ml of DW and
100 ml of conc. sulphuric acid.
Concentrated sulphuric acid (sp.gr. 1.84) containing 1.25 % silver sulphate.
Orthophosphoric acid (85 %).
Required glasswares like beakers, conical flasks,
volumetric flasks, measuring cylinders,
burettes, pipettes, test tubes.
Procedure
1. 1.0 g of the soil (ground and sieved through
0.2-mm sieve) be taken in a dry 500-ml conical
flask.
4 Lentic Soil or Mud (Physico- chemical Characteristics of Soil)