G. E. Eriyamremu

The presence of petroleum-derived compounds in the soil constitutes a significant threat to soil health and agricultural productivity. In the search for the environmentally friendly approach in the bioremediation strategies for restoration of soil health, cassava mill effluent (CME) provides an accessible, available and affordable nutrient-rich organic biowaste of cassava processing for the application of organic amendment and a sustainable biostimulant for restoration of soil health. This study investigated the efficiency of CME as a source of organic nutrients in the biorestoration of hydrocarbon degraded soil for a sustainable bioremediation strategy. This was achieved by polluting clean soil, collected and weighed into containers, with spent lubricating oil (SLO) as the source of petroleum hydrocarbon at 10% (w/w), amended with CME at 2.5% (v/w) at different frequency of daily, weekly, monthly and once for a period of six months but the control soil was not treated. The percentage changes in the quality of the amended soil were monitored at 3 and 6 months periods. Cowpea (Vigna unguiculata) were grown on the amended soils at the end of the treatment to evaluate recovery of soil quality and function. Baseline data were collected at the start of the study, and others at 3 and 6 months. For physicochemical changes in the soil, the following parameters were analysed: Soil texture, pH, cation exchange capacity (K+, Na+, Ca2+, Mg2+, Al3+), electrical conductivity (EC), total petroleum hydrocarbon (THC), and metals (Fe, Zn, Pb). Nitrogen (N2) and Phosphorus (P) contents, total organic carbon (TOC) and organic matter (OM) were also analysed. The biological activities assessed include the activities of soil enzymes (urease, phosphatase, dehydrogenase, fluorescein diacetate hydrolase and glucosidase), and microbial load