Effect of Manure and Glomus hoi on Heavy Metals and Soil Properties of Spent Engine Oil Contaminated Soil

This study aimed to assesses the impact of spent engine oil on selected soil properties including the heavy metal uptake before and after application of manure. The field experiments were carried in the early cropping season (April – July) and in the late cropping season (September – December) of year 2020 at the Obafemi Awolowo University Teaching and Research Farm, Ile-Ife. Spent-engine oil (SEO) was sourced from a mechanic workshop in Osogbo, Osun State. Amendments (poultry droppings, cow dung and leaves of Gliricidia sepium) were collected from OAU Teaching and Research Farm, Ile-Ife. Glomus hoi was also collected from around the region, and the spores were isolated through wet sieving methods. The test crop used was maize (variety is AWR- SYN- Y. A land area of 69 m x 17 m was ploughed and harrowed and arranged in an 8 X 6 alpha lattice design, containing sixteen (16) treatments with three concentrations which resulted in a total of forty-eight (48) plots in each replicate, each plot measured 2 m X 2 m with a spacing of 1 m in between the plots. The plots were impacted with Spent-engine oil (SEO) sourced from petrol engines. The oil was applied in concentration of 0 ml (0 L/ha), 400 ml (1000 L/ha) and 800 ml (2000 L/ha) to the plots. The treatments were applied to plots 7 days after Spent-engine oil (SEO) application. The layout of the experiment is as follows: Treatment 1 (T1) - Spent-engine oil only; Treatment 2 (T2) - Spent-engine oil + Cow dung; Treatment 3 (T3) - Spent-engine oil + Poultry Manure; Treatment 4 (T4) - Spent-engine oil + Glomus hoi; Treatment 5 (T5) - Spent-engine oil + Gliricidia Sepium leaves; Treatment 6 (T6) - Spent-engine oil + Cow dung + Poultry Manure; Treatment 7 (T7) - Spent-engine oil + Glomus hoi + Gliricidia sepium leaves; Treatment 8 (T8) - Spent-engine oil + Cow dung + Poultry Manure + Glomus hoi + Gliricidia sepium leaves. After treatments application, the plots were left for two weeks before planting to allow for incubation. Data collected were analyzed using appropriate statistical techniques. At the end of the experiment, all soils were impacted with the presence of increased Spent-engine oil with an increase in heavy metals in the soil. The findings suggest that a combination of different organic amendments can significantly reduce the heavy metal uptake of soils contaminated with spent-engine oil. However, further studies are needed to investigate the long-term effects of these treatments on soil quality and plant growth.