56
of P per ml). From this, a 2-ppm solution is
made. For preparation of standard curve, different concentrations of P (1, 2, 3, 4, 5 and
10 ml of 2-ppm solution) are taken into 25-ml
volumetric flasks. The colour is developed by
following Dickman and Bray’s method and
the reading taken with the help of a KlettSummerson Photoelectric colorimeter against
660 nm. The standard curve is plotted by considering the colorimeter reading in the Y-axis
and the amount of P (in ppm) in the X-axis.
7. The concentration of phosphorus in the soil
water is extrapolated from the standard curve.
4.5.5 Available Potassium (AK)
The readily exchangeable and water-soluble
potassium (K) determined in neutral ammonium
acetate extract represents the available potassium
in the soil. The estimation is done with the help
of a flame photometer (Jackson 1973).
4.5.5.1 Principle
The amount of potash is estimated with the help
of a flame photometer by comparison with a standard curve of known potassium oxide concentration determined by the same photometer.
4.5.5.2 Main Materials Required
1. Flame photometer
2. Digital pH meter
3. Neutral normal ammonium acetate: Equal
volumes of 2(N) acetic acid and 2(N) ammonium hydroxide be mixed and the pH adjusted
to 7.0 with acid or ammonia.
4. KCl (AR grade)
4.5.5.3 Procedure
1. 5.0 g of soil be shaken with 25 ml of neutral
normal ammonium acetate (pH 7.0) for 5 min
and the contents be filtered immediately
through a dry filter paper.
2. First few ml of the filtrate be rejected.
3. K is estimated in the extract with the help of
flame photometer after necessary calibration
of the instrument.
Preparation of Standard Potassium Curve:
1. A stock solution of 1,000 ppm K be prepared
by dissolving 1.9084 g of AR grade KCl
(dried at 60 °C for one hour) in DW and the
volume be made up to 1 l.
2. Required portions be diluted with the ammonium acetate solution to give 10–40 ppm of K.
3. After attaching the appropriate filter and
adjusting the gas and air pressure, the flame
photometer reading be set at zero for the blank
(Ammonium acetate) and 100 for 40 ppm K.
4. The curve be obtained by plotting the readings
of the flame photometer against the different
concentrations (10, 15, 20, 25, 30, 35 ppm)
of K.
5. Potassium content in the sample be estimated
through extrapolation.
4.5.6 Consumption, Decomposition
and Elemental Cycling
All living beings are composed of a similar type
of chemical elements. If populations of organisms are to grow, multiply (reproduce) and survive, and, also, in order to maintain a constant
biomass, there should preferably be a continuing supply of all the chemical elements which
are essential constituents of protoplasm. It is,
perhaps, known that if the supply of any one
essential element is depleted, this may limit the
growth of a population. Further, the supply of
elements may also limit the growth as well as
may shape the structure of the entire community. It may be noted here that the supply of
essential elements to populations and communities may come from outside the system, such
as terrestrial run-off into streams, stream input
into lakes and estuaries, river input into oceans
or vertical advection of deep water to the surface of the ocean. Nevertheless, much of the
flow of energy and materials is said to occur
through the detritus food web. Also, the supply
of elements through recycling is intimately
involved with the fate of detritus. On the other
hand, populations of denitrifying bacteria in
the anaerobic sediments of estuaries and other
coastal waters are, perhaps, major sinks for
available nitrogen.
4 Lentic Soil or Mud (Physico- chemical Characteristics of Soil)
of P per ml). From this, a 2-ppm solution is
made. For preparation of standard curve, different concentrations of P (1, 2, 3, 4, 5 and
10 ml of 2-ppm solution) are taken into 25-ml
volumetric flasks. The colour is developed by
following Dickman and Bray’s method and
the reading taken with the help of a KlettSummerson Photoelectric colorimeter against
660 nm. The standard curve is plotted by considering the colorimeter reading in the Y-axis
and the amount of P (in ppm) in the X-axis.
7. The concentration of phosphorus in the soil
water is extrapolated from the standard curve.
4.5.5 Available Potassium (AK)
The readily exchangeable and water-soluble
potassium (K) determined in neutral ammonium
acetate extract represents the available potassium
in the soil. The estimation is done with the help
of a flame photometer (Jackson 1973).
4.5.5.1 Principle
The amount of potash is estimated with the help
of a flame photometer by comparison with a standard curve of known potassium oxide concentration determined by the same photometer.
4.5.5.2 Main Materials Required
1. Flame photometer
2. Digital pH meter
3. Neutral normal ammonium acetate: Equal
volumes of 2(N) acetic acid and 2(N) ammonium hydroxide be mixed and the pH adjusted
to 7.0 with acid or ammonia.
4. KCl (AR grade)
4.5.5.3 Procedure
1. 5.0 g of soil be shaken with 25 ml of neutral
normal ammonium acetate (pH 7.0) for 5 min
and the contents be filtered immediately
through a dry filter paper.
2. First few ml of the filtrate be rejected.
3. K is estimated in the extract with the help of
flame photometer after necessary calibration
of the instrument.
Preparation of Standard Potassium Curve:
1. A stock solution of 1,000 ppm K be prepared
by dissolving 1.9084 g of AR grade KCl
(dried at 60 °C for one hour) in DW and the
volume be made up to 1 l.
2. Required portions be diluted with the ammonium acetate solution to give 10–40 ppm of K.
3. After attaching the appropriate filter and
adjusting the gas and air pressure, the flame
photometer reading be set at zero for the blank
(Ammonium acetate) and 100 for 40 ppm K.
4. The curve be obtained by plotting the readings
of the flame photometer against the different
concentrations (10, 15, 20, 25, 30, 35 ppm)
of K.
5. Potassium content in the sample be estimated
through extrapolation.
4.5.6 Consumption, Decomposition
and Elemental Cycling
All living beings are composed of a similar type
of chemical elements. If populations of organisms are to grow, multiply (reproduce) and survive, and, also, in order to maintain a constant
biomass, there should preferably be a continuing supply of all the chemical elements which
are essential constituents of protoplasm. It is,
perhaps, known that if the supply of any one
essential element is depleted, this may limit the
growth of a population. Further, the supply of
elements may also limit the growth as well as
may shape the structure of the entire community. It may be noted here that the supply of
essential elements to populations and communities may come from outside the system, such
as terrestrial run-off into streams, stream input
into lakes and estuaries, river input into oceans
or vertical advection of deep water to the surface of the ocean. Nevertheless, much of the
flow of energy and materials is said to occur
through the detritus food web. Also, the supply
of elements through recycling is intimately
involved with the fate of detritus. On the other
hand, populations of denitrifying bacteria in
the anaerobic sediments of estuaries and other
coastal waters are, perhaps, major sinks for
available nitrogen.
4 Lentic Soil or Mud (Physico- chemical Characteristics of Soil)