Hyperaccumulator Oilcake Manure as an Alternative for Chelate-Induced Phytoremediation of Heavy Metals Contaminated Alluvial Soils

The ability of hyperaccumulator oilcake manure as compared to chelates was investigated by growing <i>Calendula officinalis</i> L for phytoremediation of cadmium and lead contaminated alluvial soil. The combinatorial treatment T₆ [2.5 g kg⁻¹oilcake manure + 5 mmol kg⁻¹ EDDS] caused maximum cadmium accumulation in root, shoot and flower up to 5.46, 4.74 and 1.37 mg kg⁻¹and lead accumulation up to 16.11, 13.44 and 3.17 mg kg⁻¹, respectively at Naini dump site, Allahabad (S₃). The treatment showed maximum remediation efficiency for Cd (RR = 0.676%) and Pb (RR = 0.202%) at Mumfordganj contaminated site (S₂). However, the above parameters were also observed at par with the treatment T₅ [2.5 g kg⁻¹oilcake manure +2 g kg⁻¹ humic acid]. Applied EDDS altered chlorophyll–a, chlorophyll–b, and carotene contents of plants while application of oilcake manure enhanced their contents in plant by 3.73–8.65%, 5.81–17.65%, and 7.04–17.19%, respectively. The authors conclude that Calendula officinalis L has potential to be safely grown in moderately Cd and Pb-contaminated soils and application of hyperaccumulator oilcake manure boosts the photosynthetic pigments of the plant, leading to enhanced clean-up of the cadmium and lead-contaminated soils. Hence, the hyperaccumulator oilcake manure should be preferred over chelates for sustainable phytoremediation through soil-plant rhizospheric process.