Integrated Application of Thiourea and Biochar Improves Maize Growth, Antioxidant Activity and Reduces Cadmium Bioavailability in Cadmium-Contaminated Soil

Cadmium (Cd) contamination of croplands jeopardizes sustainable crop production and human health. However, curtailing Cd transfer and mobility in the rhizosphere-plant system is challenging. Sole application of biochar (BC) and thiourea (TU) has been reported to restrain Cd toxicity and uptake in plants. However, the combined applications of BC and TU in mitigating the harmful effects of Cd on plants have not yet been thoroughly investigated. Therefore, this study attempts to explore the integrated impact of three maize stalk BC application rates [B(0) (0% w/w), B(1) (2.5% w/w), and B(2) (5% w/w)] and three TU foliar application rates [T(0) (0 mg L(–1)), T(1) (600 mg L(–1)), and T(2) (1,200 mg L(–1))] in remediating the adverse effects of Cd on maize growth, development, and physiology. Results demonstrated that Cd concentration in soil inhibited plant growth by reducing leaf area, photosynthesis activity, and enhanced oxidative stress in maize. Nevertheless, BC and TU application in combination (B(2)T(2)) improved the fresh biomass, shoot height, leaf area, and photosynthesis rate of maize plants by 27, 42, 36, and 15%, respectively, compared with control (B(0)T(0)). Additionally, the oxidative stress values [malondialdehyde (MDA), hydrogen peroxide (H(2)O(2)), and electrolyte leakage (EL)] were minimized by 26, 20, and 21%, respectively, under B(2)T(2) as compared with B(0)T(0). Antioxidant enzyme activities [superoxide dismutase (SOD) and catalase (CAT)] were 81 and 58%, respectively, higher in B(2)T(2) than in B(0)T(0). Besides, the shoot and root Cd concentrations were decreased by 42 and 49%, respectively, under B(2)T(2) compared with B(0)T(0). The recent study showed that the integrated effects of BC and TU have significant potential to improve the growth of maize on Cd-contaminated soil by reducing Cd content in plant organs (shoots and roots).