Cadmium Uptake and Translocation of Tomato in Response to Simulated Irrigation Water Containing Elevated Concentrations of Cadmium and Zinc in Clayey Soil

Accumulation of metals in cultivated crops is considered one of the primary constraints to irrigated agriculture. A greenhouse pot experiment was carried out to study the effects of irrigation with elevated cadmium (Cd) and a combination of cadmium and zinc (Zn) levels on Cd uptake, translocation, and productivity of tomato (Solanum lycopersicum) plants. Tomato seedlings were grown in 3-kg pots irrigated for three months until maturity. Treatments were as follows: pots irrigated with fresh water containing Cd concentrations (0, 0.01, 0.04, 0.16, 0.64, 2.54 mg L⁻¹), and pots irrigated with a combination of Cd + Zn concentrations (0 + 0, 0.01 + 2, 0.04 + 8, 0.16 + 32, 0.64 + 128, and 2.56 + 256 mg L⁻¹). Cadmium and Zn concentration in soil and plant parts (root, shoot, and fruit) increased with increasing metal dose in irrigation water. Results also showed that Cd accumulation in the fruit was much lower than in the shoot indicating lower Cd transfer from soil to the fruit. Tomato biomass was not affected by treatments even at the highest metal dose. The uptake of Cd in tomato fruit ranged from 0.5 to 2.0 and from 0.3 to 1 mg kg⁻¹, in single and combination treatments, respectively. Cadmium in fruit exceeded the permissible limit at 0.04 and 0.16 + 32 mg L⁻¹ in Cd and Cd + Zn treatments, respectively. Therefore these levels could be considered as a threshold for tomato cultivation in clayey soil.