The novel study aimed to determine the optimal population density of jerango (Acorus calamus L.) plants as the phytoremediators and examine the heavy metal absorption by rice plants under mercury-contaminated soil stress conditions. The experiment, carried out in a two-factorial randomized design, had the first factor being the number of Jerango plants per square meter with six phytoremediation treatments, viz., F₀ (control), F₁ (1 plant/m²), F₂ (2 plants/m²), F₃ (3 plants/m²), F₄ (4 plants/m²), and F₅ (5 plants/m²). The second factor was the levels of HgCl₂-treated soil medium with seven treatments, i.e., K₀ (0 ppm), K₁ (3 ppm), K₂ (6 ppm), K₃ (9 ppm), K₄ (12 ppm), K₅ (15 ppm), and K₆ (18 ppm). The experiment had two repetitions to recognize the variations in rice growth at the early vegetative stage under mercury-contaminated soil stress conditions. The results showed phytoremediation treatment with three jerango plants/m² reduced the soil mercury content below the threshold level, improved growth and production, and lessened mercury content in rice roots, stems, leaves, and grains below the quality standard threshold. No studies have yet reported jerango (A. calamus L.) as a phytoremediation plant.

Keywords: Jerango (A. calamus L.), amalgamation waste, growth traits, heavy metals, mercury-contaminated soil, tolerant rice cultivar

Key findings: Phytoremediation with three plants/m² of jerango (A. calamus L.) considerably reduced the soil mercury content below the threshold level, increased rice growth and production, and reduced the mercury content in the rice roots, stems, leaves, and grains.