Iron plaque on rice roots affects Cd uptake, but its efficacy is inconsistent due to variation in soil properties. The synergistic role of coal gasification slag (CGS) and sludge protein (SP) in mitigating soil Cd contamination, a potential alternative approach, has not yet been clarified. The research investigated how CGS and SP synergistically reduce rice Cd accumulation. Local Japonica rice LJ15 was grown in a greenhouse for 90 days, with 5 soil treatments (CK, SCd, CGS, SP, CGS + SP; 3 replicates each) and doses matched to groups: Cd (0/0.30 mg kg −1 ), CGS (0 ~ 5000 mg kg −1 ) and SP (0 ~ 5000 mg kg −1 ). The combined application of CGS and SP (CGS + SP) significantly increased rhizosphere available Fe and the formation of iron plaques on root surface (59.19% higher vs. SP and 29.57% higher vs. CGS), reduced available Cd (17.14% lower at early tillering vs. control), and promoted the formation of amorphous and crystalline iron plaques. Additionally, the combined application of CGS and SP elevated shoot Si and Fe concentrations, enhanced SOD and CAT activities, upregulated OsHMA3 expression to 3.28 times that of the CK group, and enriched rhizosphere Proteobacteria (51.22%) and Deferrisomatota (100.12%). Critically, CGS and SP exerted a synergistic effect on key Cd-mitigation outcomes: CGS + SP synergistically reduced shoot Cd content by 31.27% (early tillering, P < 0.05) and 44.98% (late tillering, P < 0.01). CGS and SP reduce rice Cd accumulation via integrated mechanisms. This integrated strategy provides a viable approach for remediating Cd-contaminated paddy soils.
Xiang et al. (Sat,) studied this question.