Sulfur application combined with water management enhances phytoextraction rate and decreases rice cadmium uptake in a Sedum plumbizincicola - Oryza sativa rotation

Background and aims Soil cadmium (Cd) contamination threatens food safety and human health. Increasing Cd phytoextraction efficiency by hyperaccumulators and growing safe products during remediation remain challenges. Methods A pot experiment was conducted to explore the effects of different rates of sulfur (S) associated with alternating drying and wetting on a Sedum plumbizincicola-Oryza sativa rotation in Cd-contaminated neutral and calcareous soils. Results The oxidation of added S under aerobic conditions significantly decreased soil solution pH and increased soluble sulfate (SO42-), Cd and iron (Fe) concentrations in both soils. During the rice growing season the soil solution redox (Eh) decreased to < -200 mV and the solution pH increased to neutral during the first few days of flooding. Soluble SO42- and Cd in the S treatments decreased significantly with increasing duration of flooding. Sulfur addition promoted shoot Cd concentrations of S. plumbizincicola by 1.7-5.5 times on calcareous soil and 1.7-2.3 times on neutral soil compared to the controls. Rice yields increased but Cd concentrations decreased at suitable S addition rates. Conclusions Appropriate sulfur amendment combined with water management can be a feasible strategy to enhance the Cd remediation efficiency of the hyperaccumulator and reduce the accumulation of Cd in the rice grains in this rotation.