Ecophysiological response of early stage Albizia lebbeck to cadmium toxicity and biochar addition

Cadmium (Cd) toxicity is among the most prominent issues regarding land degradation. Traditional approaches for soil remediation are not effective. However, phytoremediation is described as the most efficient, economical, and sustainable approach to combat with terrestrial heavy metal pollution. Moreover, if phytoremediation is used in combination with soil amendment, its effectiveness can be increased several folds. Among soil amendments, biochar is considered the best amendment due to its potential for remediation and plant growth. The objective of this study was to determine the phytoremediation potential of Albizia lebbeck in Cd-contaminated and biochar-amended soils. A pot experiment was planned to test the ecophysiological response and Cd uptake of 3-month-old uniform-sized Albizia lebbeck seedlings. Cadmium was induced in soil through irrigational water at the rate of 25 mg/L. Two concentrations of biochar were used: B1 (3%) and B2 (6%). A total of six treatments were applied: Cd0B0 (T1), Cd0B1 (T2), Cd0B2 (T3), Cd1B0 (T4), Cd1B1 (T5), and Cd1B2 (T6), where, Cd0 and B0 designate the control treatment. The plants were harvested after 4 months of growth in the soil with amendments. The maximum growth and gas exchange characteristics were showed by the plant of T3. Cadmium toxicity reduced the growth and gas exchange characteristics to a great extent. Plants of T4 showed the minimum growth compared to the other amendments. The addition of 6% biochar in Cd-contaminated soil (T6) resulted in the decent increase in the growth of plants. The maximum root length (67.18 cm) and shoot length (80.06 cm) were observed in the plants of T3, whereas, the minimum root length (13.94 cm) and shoot length (35.03 cm) were observed in the plants of T4. This study suggests that biochar can be used to enhance the growth of agroforestry tree species like Albizzia lebbek in Cd-contaminated soils.