Impact of cassava peel on soil nutrient and microbial restoration of crude oil contaminated soil in Rivers State, Nigeria

Abstract

The decrease in essential soil nutrients and microbial load in crude oil-contaminated soils poses a significant challenge to soil restoration efforts. This research was conducted to investigate the impact of cassava peel waste on enhancing soil nutrients and restoring microbial communities in crude oil-polluted soils. The study employed a Complete Randomized Design with the following treatments: T1: Crude oil-contaminated soil + 100g cassava peel waste; T2: Crude oil-contaminated soil + 200g cassava peel waste; T3: Crude oil-contaminated soil + 300g cassava peel waste; T4: Crude oilcontaminated soil only (control) + 0g cassava peel waste T5: Uncontaminated soil only (control) + 0g cassava peel waste. Two seedlings of Abelmoschus esculentus were planted in each treatment to assess the effects on plant growth. The application of cassava peel waste in crude oil-polluted soils (T1-810.05mg/kg; T2-809mg/kg; T3-640.5mg/kg) resulted in a significant decrease in Total hydrocarbon (THC) compared to (T4-1350mg/kg). Among the treatments, T3 exhibited the greatest reduction in THC. The highest mean values of potassium (K-32.3 mg/kg), and phosphorus (P-14.8 mg/kg) were recorded in T3 and T1 for nitrogen (N- 4.92 mg/kg) content. The height of the plants varied across the treatments, with the highest measurements recorded in T1 during week 2 (15.3 cm), T3 during weeks 4 and 8 (19.6 cm and 36.9 cm, respectively), and T2 during week 6 (26.3 cm). Additionally, T4 and T5, showed the least reduction in leaf number, stem girth, fresh and dry weight, and microbial population. Higher microbial loads were observed in the treatments with cassava waste T1 at 6wks and 8kws (24.0 x104 ; 26.0 x104 ); T3 at 2wks and 4kws (7.31 x104 ; 17.2x104 ) compared to the untreated contaminated soil (T4). This increase in microbial population is essential for the biodegradation of hydrocarbons and the overall recovery of soil health. The study highlights the potential of cassava peel as a cost-effective and environmentally friendly amendment that can be utilized in large-scale soil restoration efforts, particularly in regions affected by crude oil pollution.