Uptake and leaching of Cu, Cd, and Cr after EDTA application in sand columns using sorghum and pearl millet

In a greenhouse experiment using sand columns, sorghum and pearl millet were grown and spiked with metal solutions of Cu, Cd, and Cr in two concentrations. The chelating agent EDTA was applied to one-month-old plants and metal mobilization was observed through uptake by the plants or leaching through the columns during a period of one month. Growth was much better in pearl millet than sorghum under metal stress. Metal uptake was significantly higher in sorghum and was in the order root>shoot>leaves in both the plants. Metals were differentially mobilized in the order of Cu>Cr>Cd as shown by plant uptake and leaching through the columns. The root to shoot translocation of Cd was significantly improved after EDTA application, and to some extent for Cu but not for Cr. The leaching of metals was the maximum in the second week of application and was almost negligible by the fourth week conforming to the amount of EDTA detected in the leachate. Leaching of Cr differed in the maximum amount at the time of chelant application, while Cu and Cd showed maximum leaching after 7 days. As compared to sorghum, pearl millet was better at controlling leaching because of its extensive root system.