Prediction of Heavy Metal Uptake in Red Radish (Raphanus sativus var. sativus) in Relation to Soil Characteristics and Sewage Sludge Amendments

This study developed predictive models to assess the uptake of nine heavy metals (Cd, Co, Cr, Cu, Fe, Mn, Ni, Pb, Zn) in red radish (Raphanus sativus var. sativus) shoots and roots under increasing sewage sludge amendments (0–50 g/kg soil). Sewage sludge application significantly altered soil properties, including pH, EC, and organic matter content. Cd, Co, Pb, and Zn were enriched in sewage sludge, whereas Cr, Cu, Fe, Mn, and Ni were more abundant in soil. Post-cultivation analysis showed significant changes in soil properties and heavy metal levels with increasing sewage sludge amendments. Red radish preferentially accumulated heavy metals in roots, though Zn showed the highest translocation to shoots. Bioaccumulation factors (BAFs) and translocation factors (TFs) indicated metal-specific uptake patterns influenced by soil pH, electrical conductivity (EC), organic matter (OM), and initial heavy metal contents. Also, multiple linear regression predicted heavy metal accumulation based on soil parameters with high model efficiency and low prediction errors. Thus, excessive sewage sludge application poses contamination risks, necessitating regulated application to safeguard agricultural systems.