Saturday, 15 July 2006

Remediation of Soil Cadmium Toxicity Using Cd-Zn Interaction for Sustainable Agriculture.

D. Mazumdar, SS Das and SK Patra, Bidhan Chandra Krishi Viswavidyalaya, Mohanpur, Nadia-741252, West Bengal, India

The heavier-textured agricultural soil of Dankuni basin is congested by heavy metal pollution especially of cadmium by anthropogenic activities. It is a highly toxic element in the environment and becomes a potential hazard to the biospheres. To develop a suitable remediation measure for alleviating soil Cd toxicity for sustainable agriculture, an incubation experiment involving mutual interactions of cadmium and zinc each at four levels of Cd (0,1,2 and 5 mg/kg) and Zn (0,5,10 and 20 mg/kg) was designed and extended for a period of 0, 7, 15, 30 and 60 days. The different statistical analysis viz. simple linear model technique, Duncan's test and LSD tests were employed to compare the main effects of Cd, Zn and days of incubation as well as their two order and three order interaction effects on bioavailable concentrations of soil Cd. There was a significant and progressive build up of soil extractable Cd with increasing level of Cd application, whereas a gradual but significant depression of Cd in soil was occurred either due to increasing Zn levels or advancement of days. The interactions of Cd vs. day and Zn vs. day also registered the progressive but significant decline of soil extractable Cd from 33.3 to 56.2 per cent and 44.6 to 59.3 per cent, respectively due to increasing Cd application from 0 to 5-mg/kg soil. However, the combined effect of applied Zn and days of incubation was found more effective in alleviating Cd toxicity from contaminated soil than applied Zn alone. Based on calculated days vs. Cd vs. Zn means for estimated Cd availability, a simple regression equation via curve estimation technique was developed using the applied doses of Cd, Zn and days of incubation as regressed variables and the observed Cd as dependent variable. In this model, it will be possible to predict the number of days likely to be required to maintain the standard permissible level of soil Cd for planning sustainable agriculture. The different options of Zn doses with varying elapse period can be obtained from this ready reckoner to make soil free from Cd toxicity. Alternatively, this study was also found useful for simultaneous alleviation of Zn toxicity as well as maintaining prescribed Zn concentration in soil with the addition of varying Cd levels compared at different elapse period. However, it will not be realistic in view of severe Cd toxicity development in soil.

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