Removal of Cd from Actual Soils Polluted with Cd and Zn and Cd-added Soils by Brassica juncea and Zea mays

We have alternated the 3-week cultivation of corn (Zea mays L.) and that of Indian mustard (L~rassica juncea (L.) Czern) in a pot with the sequential rotation, corn-Indian mustard-com-Indian mustard, in order to remove Cd from two actual soils polluted wlth Cd and Zn, one (low Cd polluted (LP)) containing 6.5mg Cd kg~ * and 715mg Zn kg~ * and another (high Cd polluted (HP)) wlth 13.6 mg Cd kg~1 and 836 mg Zn kg~*. Fertilizer applications to soil in a rotational cropping can inhibit the decrease in the phyioextraction efficiency. As the total of the all cultivations, the Cd removal from the soils was 2.10/0 of the total soil Cd amount in the LP plot and 1.00/0 in the HP plot, whereas the Zn removal was lower than the Cd cases, 0.570/0 in the LP plot and 0.170/0 in the HP plot, respectively. The Cd absorptions by both plants were significantly greater in the metal-added soils than in the actual polluted soils in all cultivations (p<0.05). This would be caused by the high concentrations of exchangeable Cd in the added soils. These results indicated that the use of metal- added soils is likely to overestimate the efficiency of some plants in phytoextraction experiments involving actual polluted soils with its variation by the experimental conditions