Biostimulation of Crude Oil Polluted Soil Using Plantain Trunk Liquid Extract: An Assessment Using Maize Growth Bioassay

Abstract

Crude oil contamination poses a severe threat to soil health and agricultural productivity. This study investigated the potential of liquid extract from plantain (Musa paradisiaca) trunk as a low-cost, eco-friendly biostimulant for mitigating crude oil toxicity in soil. The extract was obtained by squeezing freshly cut plantain trunk and sieving the filtrate. Soil was artificially contaminated with 2% w/w crude oil (130g per 6.5 kg soil) and divided into two groups: contaminated soil treated with 30cl of plantain trunk liquid applied every 3 days for 7 applications (B) and contaminated untreated (C) with an additional uncontaminated soil as control (A). After treatment, maize (Zea mays) seeds were planted in each soil sample and growth parameters (coleoptile and plumule emergence days, and seedling height at 15, 18, and 21 days) were monitored for 21 days. The results showed no germination occurred in the untreated contaminated soil, demonstrating the acute toxicity of crude oil. Seeds in the treated soil exhibited delayed germination (11–13 days) and measurable seedling growth, reaching mean heights of 7.0 ± 0.28 cm (Day 15), 13.45 ± 1.06 cm (Day 18), and 19.15 ± 0.35 cm (Day 21). The uncontaminated control showed faster germination (8–11 days) and superior growth (mean heights up to 22.9 ± 0.42 cm on Day 21). These results have demonstrated that plantain trunk liquid extract effectively reduced crude oil toxicity, enabling seed germination and seedling establishment while none occurred in the untreated soil. The observed improvement is attributed to biostimulation through provision of readily available nutrients, enhanced soil moisture and promotion of indigenous hydrocarbon-degrading microbial activity. This study provides preliminary evidence that supports the use of abundant agro-waste as a sustainable, low-cost amendment for bioremediation of crude oil polluted soils. Further investigation is recommended to quantify total petroleum hydrocarbon (TPH) reduction, characterize plantain trunk liquid’s chemical composition, assess microbial shifts and optimize application rates for large scale application.