Growth response of vetiver grass (Chrysopogon zizanioides (L.) Roberty) to chemical amendments in assisted phytoremediation of contaminated mined soil

The application of chemical amendment to improve metal availability is a key strategy in phytoremediation and an important determinant for successful removal of heavy metals from soil, although empirical data on their effects on plants used in phytoremediation are scanty. In this study, field-based assisted phytoremediation with ethylene-diamine-tetra-acetic acid (EDTA), nitrogen-potassium-phosphorus fertilizer (NPK) and combination of EDTA and NPK modelled after the completely randomized block design was used to determine the effects of chemical amendments on some morphological and physiological growth parameters of vetiver grass (Chrysopogon zizanioides (L.) Roberty) as well as the relative effects of chemical amendment and free heavy metal ions contamination. Results showed that the soil amendments (EDTA, NPK, EDTA + NPK) enhanced plant height and diameter, and reduced the toxicity of free metal ions. On the other hand, heavy metals reduced plant chlorophyll-a and -b, and plant root, and correlated with lipid peroxidation. Notably, EDTA contributed the least to enhancing plant height, diameter, and root length although it interacted positively with NPK to enhance the above-mentioned parameters. In general, the results of this study confirm the effectiveness of chemical amendments (EDTA and NPK in this case) in reducing the toxicity of free heavy metal ions in plant during phytoremediation.