Cadmium Phytoremediation by Corn as Affected by Organic Residues (Wheat and Alfalfa) application in a Calcareous Soil

Phytoremediation is a technique for removal of heavy metals including cadmium (Cd) from soils; which is less expensive compared to other methods. Due to the fact that this method is time consuming with low efficiency, hence, other methods are proposed to increase the efficiency of phytoremediation. One method is the application of organic residues to the soils. A greenhouse experiment was conducted to study the effects of the application of wheat or alfalfa residues on phytoremediation of Cd-contaminated calcareous soil by corn. The experiment was a factorial 2×3×3 arranged in a completely randomized design. Treatments consisted of the two types of the organic residues (wheat and alfalfa) in three levels (0, 1, and 2% by weight) and three levels of Cd application (5, 15, and 25 mg kg-1) with three replications. Results indicated that increasing the Cd levels, significantly increased the Cd concentration in soil and in the corn shoots, but decreased the dry weight of the corn and bio-accumulation factor (BAF) of Cd. Increasing the levels of wheat and alfalfa residues significantly increased the Cd concentration in the corn shoots and BAF. Addition of the wheat residues resulted in a higher Cd concentration in the corn aerial parts and BAF compared to those with addition of the alfalfa. However, the corn mean shoot dry weight was significantly higher in the soil amended with the alfalfa residues compared to those amended with the wheat residues. Influences of the wheat or alfalfa residues addition on the Cd uptake by corn were similar. Phytoremediation efficiency of the corn at low Cd levels was higher than that at high rates of the applied Cd.