Evaluation of Cassava Performance and Quality in Petroleum-Contaminated Soils of the Niger Delta: Implications for Human Health and Food Safety

Abstract

Petroleum contamination poses significant threats to soil quality, crop productivity, and food safety. This study evaluated the effects of crude oil pollution on cassava (Manihot esculenta) growth, yield, and heavy metal accumulation, alongside the efficacy of organic and inorganic soil amendments. Soil analysis revealed a significant reduction in petroleum hydrocarbons (2250 ± 500 mg/kg to 1400 ± 450 mg/kg, p = 0.002) and heavy metals (Pb: 12.5 ± 2.3 mg/kg to 9.8 ± 1.7 mg/kg, p = 0.005; Cd: 2.1 ± 0.6 mg/kg to 1.5 ± 0.4 mg/kg, p = 0.010) after cassava cultivation, indicating partial phytoremediation. Organic manure application resulted in higher soil nutrient retention (N: 3.2 ± 0.4%, P: 2.8 ± 0.3%, K: 2.5 ± 0.4%) compared to inorganic fertilizers, enhancing soil fertility (p< 0.05). However, petroleum contamination significantly reduced cassava growth (TME 419 height: 140 ± 15 cm vs. 180 ± 18 cm in control, p = 0.003) and yield (9.5 ± 1.2 t/ha vs. 18.5 ± 2.0 t/ha in control, p = 0.007).

Contaminated cassava tubers accumulated hazardous levels of heavy metals (Pb: 5.2 ± 1.0 mg/kg, Cd: 1.3 ± 0.4 mg/kg, As: 2.0 ± 0.6 mg/kg), exceeding WHO/FAO food safety limits and posing serious health risks. Additionally, nutrient composition was adversely affected, with reduced carbohydrate (60.5 ± 2.5%) and protein (1.8 ± 0.3%) content in contaminated samples (p< 0.05). Furthermore, phytoremediation and organic amendments should be integrated into agricultural practices to improve soil quality and reduce heavy metal bioavailability. However, government agencies should implement strict food safety monitoring and establish contamination threshold guidelines to protect public health in oil-impacted regions.