Sorption and availability of zinc in Diaralands of Bihar
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Date
2010
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Rajendra Agricultural University
Abstract
The present investigation on “Sorption and availability of zinc in Diaralands of Bihar” was conducted to elucidate the relative influence of soil properties on available zinc, critical limit of zinc in soil and plant, distribution of zinc fraction in soil, zinc adsorption, kinetic of adsorption and desorption and solubility relationship of zinc in diaraland soils of Bihar under laboratory and pot condition.
One hundred twenty six cultivated soils of low, medium and upland physiography were collected for zinc delineation. Based on available zinc and organic carbon content 24 bulk soil samples were collected for evaluation of critical limit taking maize as test crop. Out of these 24 soils, 10 soils were selected for adsorption, kinetics of adsorption, desorption and solubility relationship of zinc. Soils were neutral to slightly alkaline in reaction having 78 per cent deficiency in available Zn. The extent of Fe, Mn and Cu deficiency was 30, 11 and 4 per cent respectively. The chemical fractionation of zinc in soil indicated that a very small portion of total zinc was distributed in comparatively more soluble forms and most of the zinc remained as residual fraction.
The critical limit of available zinc was 0.75 mg kg-1 whereas the critical concentration of zinc in 45 days old maize plant tissue was 22.5 mg kg-1. The dry matter yield, Zn uptake and zinc concentration in maize plant increased with graded level of zinc.
Step down multiple regression analysis and path analysis suggested that water soluble + exchangeable zinc, crystalline oxide bound zinc and amorphous oxide bound zinc are the major pool of soil zinc which contributed towards available zinc, dry matter yield of maize and Zn uptake by maize.
Adsorption isotherm studies indicated that most of the soils produced L-type adsorption behaviour whereas a few soils produced S-type of adsorption isotherm. Out of several sorption model tested, freundlich adsorption model was found best fit for adsorption data.
Kinetic of Zn adsorption could be best explained through Elovich kinetic model, however, the kinetics of desorption was diffusion controlled.
The estimated stability constant is very much close to the theoretical value of Zn-soil but slightly higher than that of Zn (OH)2, hence Zn (OH)2 along with Zn-soil control the solubility of Zn in these soil.
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Keywords
Soils, Zinc availability, Bihar