Phytomanagement of cadmium using Tagetes erecta in greenhouse and field conditions

Greenhouse and field studies investigated the phytoextraction potential of soil cadmium (Cd) by Tagetes erecta L., a popular ornamental flower in Asia. The effects of organic fertilizer, cattle manure, and pig manure in supporting plant growth and enhancing Cd uptake were also examined. Plants grown in soil supplemented with pig manure produced greatest biomass (12.8 ± 1.6 and 11.8 ± 0.9 g plant⁻¹ in greenhouse and field experiments, respectively). Plant parts accumulated Cd in the order: shoot > root > flower in all treatments. Furthermore, T. erecta had a high phytoextraction potential as evidenced by translocation factors and enrichment coefficients > 1 for shoots. Marigolds cultivated in Cd-contaminated soil supplemented with organic fertilizer (CdOrg) exhibited Cd concentrations in flowers below the Maximum Permissible Level for consumption (< 0.2 mg kg⁻¹), indicating that the edible flowers pose no health risk to humans. The flowers additionally contained significant quantities of total phenolics and phenolic acids, which may indicate their potential as an indicator of Cd-initiated oxidative stress. The phenolic compounds can furthermore function as precursors for manufactured medicinal products by acting as antioxidants and antimicrobials. Application of organic fertilizer and selected organic amendments may have contributed to the greater concentrations of phenolics. The Cd alone treatment resulted in lowest production of bioactive compounds and antioxidant capacity. It is proposed that T. erecta be applied for Cd phytoextraction while enhancing local economies as an ornamental species, and for plant extracts for application of bioactive compounds and antioxidant capacity.