Phytoremediation-Induced Recovery of Crude Oil-Polluted Soil Using Vetiveria zizanioides and Panicum maximum and Susequent Enhancement of Okra (Abelmoschus esculentus L.)

Crude oil pollution reduces soil fertility, suppresses beneficial microbial activity, and limits crop productivity in oil-producing agricultural areas. This study evaluated the capacity of Vetiveria zizanioides and Panicum maximum, used singly and with poultry manure amendment, to remediate crude oil-contaminated soil and improve the subsequent performance of okra (Abelmoschus esculentus L.). The phytoremediation phase used six treatments with four replicates over fourteen weeks, after which okra was cultivated on the remediated soils. Results showed that Vetiver combined with poultry manure produced the highest TPH reduction of 82.62%, followed by Guinea grass with poultry manure at 76.21%. The amended phytoremediation treatments improved soil nutrient status, increased hydrocarbon-utilizing bacterial populations, and enhanced okra growth and yield compared with polluted unremediated soil. These findings show that integrating tolerant grasses with organic amendment is a practical, low-cost, and sustainable strategy for restoring crude oil-contaminated agricultural soil and improving crop productivity.