Influence of elemental sulfur on cadmium bioavailability, microbial community in paddy soil and Cd accumulation in rice plants

Cadmium (Cd) is highly toxic to living organisms and the contamination of Cd in paddy soil in China has received much attention. In the present study, by conducting pot experiment, the influence of S fertilizer (S(0)) on rice growth, iron plaque formation, Cd accumulation in rice plants and bacterial community in rice rhizosphere soil was investigated. The biomass of rice plants was significantly increased by S(0) addition (19.5–73.6%). The addition of S(0) increased the formation of iron plaque by 24.3–45.8%, meanwhile the amount of Cd sequestered on iron plaque increased. In soil treated with 5 mg/kg Cd, addition of 0.2 g/kg S(0) decreased the diffusive gradients in thin films (DGT) extractable Cd by 60.0%. The application of S(0) significantly decreased the concentration of Cd in rice grain by 12.1% (0.1 g/kg) and 36.6% (0.2 g/kg) respectively. The addition of S(0) significantly increased the ratio of Acidobacteria, Bacteroidetes in rice rhizosphere soil. Meanwhile, the ratio of Planctomycetes and Chloroflexi decreased. The results indicated that promoting Fe- and S-reducing and residue decomposition bacterial in the rhizosphere by S(0) may be one biological reason for reducing Cd risk in the soil-rice system.