Macronutrients dynamics in copper-contaminated soils: Implications for hemp growth and its phytoremediation potential

Fibrous plants with higher biomass, particularly industrial hemp, have ability to withstand and accumulate significant quantities of heavy metals from contaminated environments. The present study aimed to evaluate the dynamics of different levels (ratios) of macronutrients nitrogen, phosphorus and potassium (NPK) viz., NPK₁NPK (1:1:1); NPK₂NPK (2:1:1); NPK₃NPK (3:1:2); NPK₄NPK (4:1:2) on hemp growth and Cu contents under various levels of Cu stress (100, 400 and 800 mg kg⁻¹ on dry soil basis using CuSO₄·5H₂O). Results revealed that by increasing the Cu stress, growth and biomass decreased linearly and lipid per oxidation and enzymatic antioxidants increased. Balanced application of NPK improved the biomass and decreased the membrane damage by the modulation of malonaldehyde contents. Maximum concentration of Cu in roots (377.47 ± 4.90 mg kg⁻¹), shoots (137.45 ± 5.60 mg kg⁻¹) and (150.07 ± 3.57 mg kg⁻¹) was recorded at Cu₃NPK₂ treatment as compared to control. Maximum translocation factor (TF) and bioaccumulation coefficients (BAC) in the shoots and leaves of hemp plant were noticed where Cu stress was applied at the rate of 100 mg kg⁻¹. However, BAC and TF were below 1. The NPK₂ treatment enhanced biomass and increase Cu content both in leaves and stems, rather than the roots. Our study suggests that balanced application of NPK is a practicable approach to alleviate Cu stress and improve biomass production of industrial hemp plant. These findings indicate that optimum nutrient supply, under Cu stress, can maximize the growth potential and overall health of industrial hemp, making it a viable option for phytoremediation and sustainable agriculture on contaminated soils.