Lead (Pb) and cadmium (Cd) accumulation in leafy vegetables raises food-safety concerns, but evidence on how bacterial consortium complexity affects metal accumulation remains limited. This study aimed to evaluate Pb and Cd concentrations in edible spinach (Amaranthus viridis) tissues after applying compost enriched with increasingly complex Pumakkal bacterial consortia. A completely randomized design comprised six treatments (P0: uninoculated control; P1–P5: 3, 6, 9, 12, and 15 bacterial isolates, respectively), with six plant replicates per treatment. Oil-palm empty fruit bunches and chicken manure were co-composted at a 3:1 ratio. Plant growth was evaluated using height, leaf number, and fresh weight, while Pb and Cd concentrations were determined spectrophotometrically at the treatment level. Growth data were analyzed using Kruskal–Wallis tests, whereas metal concentrations were analyzed descriptively. Pb concentrations decreased from 0.012 ppm (P0) to 0.001 ppm (P5), representing 91.7% attenuation, while Cd decreased from 0.0066 to 0.0017 ppm, representing 74.2% attenuation. Plant height (p = 0.008), leaf number (p = 0.039), and fresh weight (p = 0.010) differed significantly, with P5 showing the strongest overall growth response. These findings indicate an association between Pumakkal consortium formulation complexity, reduced edible-tissue metal concentrations, and improved spinach growth. The results highlight the potential of Pumakkal-enriched compost as a sustainable organic amendment for improving vegetable quality, although replicate-level metal analyses and mechanistic validation are needed before broader application.
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