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Potassium availability, releasing power and uptake by chickpea and rajmash in different soil types of pulse growing regions of India.

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Title Potassium availability, releasing power and uptake by chickpea and rajmash in different soil types of pulse growing regions of India.
Potassium availability, releasing power and uptake by chickpea and rajmash in different soil types of pulse growing regions of India.
 
Creator ICAR_CRIDA
 
Subject equilibria ,AG0; enthalpy
 
Description Not Available
A large number of experimental studies have been conducted to probe the
dynamic nature of equilibria between different forms of soil potassium (K),
namely water-soluble K, exchangeable K, non-exchangeable K and the mineral
or structural K. Most of these studies have employed a batch technique; allowing
the system, namely soil K/solution K, to attain equilibrium at a constant
temperature (and pressure). The ensuing distribution ratio (Goulding, 1983) has
been related to the approximate thermodynamic equilibrium (K) constant. From
the latter, as well as from a study of its temperature dependence, a number of
thermodynamic parameters (such as standard free energy change, AG0; enthalpy
change, AH; and entropy change, AS) of K* exchange equilibria between soil
solid and solution phases, have been computed. The negative sign of AG at a
constant temperature and pressure of the ion-exchange reaction is taken to indicate
the spontaneity of the given ion-exchange reaction, or the relative preference of
the soil colloidal phase for K' ions over other exchangeable ions, notably Ca2 "
and Mg 2. Not withstanding the value of such thermodynamic studies, however,
it is worth noting that thermodynamic parameters such as a large negative AG
TY value merely suggests the formation of a large amount of product for the
forward direction of the given reaction at equilibrium. It offers no idea as to how
fast or how slow that equilibrium is attained at the given temperature. Although
the AG of the reaction, H2 (g) + /202 (g) = H 20(g), is strongly negative at 25°C
and I atm pressure, no detectable quantity of water vapour would be obtained
on keeping a mixture of hydrogen and oxygen gases at 25°C and I atm pressure
for a very long time. This is because the attainment of equilibrium of the forward
reaction, being characterized by a high activation energy, is extremely slow.
Indeed, for thermodynamic description of the rate processes, one has to have a
recourse to irreversible thermodynamics (Katchalsky and Curran, 1965; Sanyal,
1981; Nanda and Sanyal, 1995), but this branch of thermodynamics has seldom
been used in the description of soil processes. Thermodynamic considerations,
leading to equilibrium constant, are, strictly speaking, applicable only to a closed
system. Soil K being subject to fixation, release, leaching, plant uptake, and also
addition through fertilizers, irrigation water and crop residues, does not satisfy
the description of a closed system.
Not Available
 
Date 2020-02-25T06:48:41Z
2020-02-25T06:48:41Z
2003
 
Type Technical Report
 
Identifier Not Available
Not Available
http://krishi.icar.gov.in/jspui/handle/123456789/32672
 
Language English
 
Relation Not Available;
 
Publisher Srinivasa Rao, Ch.