Effect of Calcium Silicate-biological Humus Fertilizer Composite on Uptake of Cd by Shallots from Contaminated Agricultural Soil

Abstract

The safety of vegetable production is a key link in reducing cadmium consumption through the food chains. Field experiments were conducted to investigate the effects of composite materials (calcium silicate-biological humus fertilizer) on the growth of shallots and the uptake of Cd by shallots from contaminated agricultural soil. Four treatments (T1: 0.5% calcium silicate+0.5% biological humus fertilizer; T2: 0.5% calcium silicate+1.0% biological humus fertilizer; T3: 1.0% calcium silicate+0.5% biological humus fertilizer; and T4: 1.0% calcium silicate+1.0% biological humus fertilizer) and a control group (CK) were adopted. The changes in soil pH, DTPA-extractable Cd, biomass of shallots, and cadmium concentrations in shallots over time under different treatments were analyzed. The results show that the application of composite amendments decreased the concentrations of DTPA-extractable Cd in the soil. In particular, after T3 treatment, the concentrations of soil DTPA-extractable Cd decreased by 60.71%, 49.54%, 44.63%, and 58.94% after 14, 28, 42, and 56 d, respectively. The biomass of the shallots aboveground increased significantly by 107.99% and 107.19% after T3 and T4 treatment, respectively. The composite amendments exhibited different effects on the uptake of Cd by the shallots from the soil, and the T4 treatment was the most effective in immobilizing Cd and inhibiting translocation of Cd into the shallots. The cadmium concentration in the shallots decreased by 43.80% after 56 d with the T4 treatment. In conclusion, T4 is the optimum treatment for soil cadmium immobilization.