Differential Phytochemical Response to Increased Nitrogen in Manihot esculenta Crantz (Cassava) Grown in Mining Soil

Ikpeshi and Okpella, communities in Edo State, Nigeria, are areas with active mining operations. These activities can significantly impact the surrounding environment, including the plant life and, consequently, the phytochemical composition of plants growing in these areas. This study investigated the effects of nitrogen amendment on the phytochemical composition of cassava grown in mining soil. The experiment was conducted on loamy sandy soil collected from two different sites each from Ikpeshi and Okpella, and the experiment was arranged in a completely randomized design in triplicate with two treatments of 2 g and 2.5 g nitrogen. Steroids, terpenoids, flavonoids, anthraquinones, phlobatannins, saponins, cardiac glycosides with a steroidal nucleus (CG1), cardiac glycosides with deoxy sugar, cardiac glycosides with cardenolides, and phenols, except for anthraquinone, which was absent, were analyzed in the methanolic extract cassava. The highest concentration of all parameters was recorded for CG1 at Okpella site A (4.91 ± 0.16), and phlobatannin was observed to have the lowest concentration of all parameters, at 0.04 ± 0.02 for Ikpeshi site A at 2 g nitrogen. Increased nitrogen concentration significantly increased the concentrations of alkaloids, flavonoids, and phenols, while other phytochemicals remained relatively stable. At 2.5 g nitrogen, the highest flavonoid concentration was recorded for IKA (1.69 ± 0.02), the highest phenol concentration was recorded for IKB (1.39 ± 0.06), and the highest alkaloid concentration was recorded for OKB (1.69 ± 0.28). This study provides evidence that nitrogen amendment influences the phytochemical composition of cassava grown in post-mining soils from Ikpeshi and Okpella.