Differences in Root Surface Iron Plaque Components between Main and Ratoon Crops of Different Rice Varieties and Their Effects on Cadmium Accumulation in Brown Rice

• • High stubble (60 cm) reduced brown rice Cd in most varieties compared to low stubble (20 cm) in the ratoon crop, with reductions up to >70% as previously reported for Huanghuazhan; low stubble increased Cd in some varieties above main-crop levels, elevating non-carcinogenic risk. • • Root surface iron plaque Am-Fe and Cry-Fe concentrations were significantly lower in the ratoon crop than in the main crop; Am-Fe dominated, but Cry-Fe showed stronger negative correlation with Cd in the main crop (P < 0.05), indicating its key role in Cd sequestration. • • In the main crop, total Fe, Am-Fe, and Cry-Fe on root surfaces were significantly negatively correlated with brown rice Cd (P < 0.05), but correlations were not significant in the ratoon crop, indicating weakened iron plaque barrier function under ratoon cropping conditions. • • Carcinogenic risk from Cd exceeded acceptable levels in all treatments (main and ratoon, both stubble heights), underscoring that even with high stubble, long-term consumption poses health risks; CLY755 and LLYHZ under high stubble are recommended for lower Cd accumulation.