Assessing the potential of Brassica juncea in zinc-iron humate-amended soil

Abstract

Heavy metal contamination of soils is a major environmental concern due to its detrimental effects on ecosystems and human health. Phytoremediation, the use of plants to extract or stabilize heavy metals, offers a sustainable and eco-friendly alternative to conventional remediation methods. Brassica juncea (Indian mustard) is recognized for its high biomass production and strong metal-accumulating capacity, making it an effective candidate for the remediation of chromium (Cr) contaminated soils. This study aimed to evaluate the effectiveness of Brassica juncea-based phytoremediation in Cr-contaminated soil and to assess the influence of zinc (Zn) and iron (Fe) humate supplementation on plant growth and Cr uptake. A completely randomized design (CRD) was employed in a pot experiment comprising nine treatments: control (T1), zinc humate (0.25% T2 and 0.5% T3), iron humate (0.25% T4 and 0.5% T5), combined zinc and iron humate (0.25% T6 and 0.5% T7), and mixed zinc and iron humate in varying combinations (0.25% + 0.5% T8 and 0.5% + 0.25% T9). Among the treatments, T5 (iron humate at 0.5%) significantly enhanced shoot fresh and dry weight as well as seed yield. T7 (zinc + iron humate at 0.5%) increased shoot fresh weight and plant height, while T4 (iron humate at 0.25%) promoted longer pod length. T2 (zinc humate at 0.25%) improved root length and biomass. The control (T1) recorded the highest Fe concentration in soil, whereas T8 (zinc + iron humate at 0.25% + 0.5%) resulted in the greatest Zn concentration. In conclusion, supplementation with zinc and iron humates improved the growth performance and chromium uptake of Brassica juncea, with iron humate at 0.5% (T5) showing the most consistent and favorable results. These findings highlight the potential of humate-based amendments to enhance phytoremediation efficiency in chromium-contaminated soils.