Chemical equilibrium and E value of Zn (ZnE) in inceptisols and entisols of tropical india
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The chemical equilibrium and E value for Zn was calculated in 9 soils of Haryana (India) which represented mainly entisol and inceptisols. The rate of isotopic exchange between65Zn and native soil Zn was quite rapid and radioactivity reduced to about 0.2 per cent of initial activity after 3 days but total Zn concentration in soil solution did not decrease. In 5 out of 9 soils equilibrium was established in 2 to 3 days. In typic ustochrepts having high clay content (3,4) equilibrium was attained in two days. In typic udipsamments (2), typic camborthids (8) and aquic vertic ustichrepts (9) it took 3 days to set equilibrium. Typic ustochrepts (5) took 5 days for equilibrium whereas typic ustipssaments (6) and typic camborthids of high O.C. did not attain equilibrium even in 7 days. This indicated that the chemistry and availability of Zn in soil would depend on soil types.
When ZnE was estimated by applying activity after equilibrium with carrier Zn and by applying activity with carrier Zn before equilibrium was set, there was no agreement in ZnE in two methods. Increasing ZnE with increasing Zn dose was observed by both methods only in alkaline typic ustochrept (4). In some soils higher E values than added amounts were observed, whereas, in soil 8 negative E values were obtained. The E values become erratic and are over estimated where complex reactions take place due to high pH, high O.C. and high complex forming elements.
Key wordsAdsorption Chemical equilibrium E value Entisols Inceptisols Isotopic exchange ZnE value
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