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Soil is a primary recipient of a myriad of waste products and chemicals used in modern industrial society (Brady and Weil, 2002). Modern industrialized societies have developed plastics and plasticizers, automobiles and refrigerants, fuels and solvents, pesticides and preservatives. Organic chemicals may enter the soil as contaminants in wastes applied on soils or as fertilizer (Lauhanen et al., 2004), in large or small automobile oil and fuel leaks and as sprays applied to control pests (Adesodun, 2004). Some of these wastes; fertilizers, automobile oil, fuel leaks, pesticides, preservatives etc are toxic even in very small concentrations. Once waste materials enter the soil, they become part of a biological cycle that affects all forms of life.

Contamination of a soil with toxic substances can degrade its capacity to provide habitat for crops (Brady and Weil, 2002). In Nigeria, the common sources of soil contamination are household wastes, agricultural wastes, gas flaring and spent automobile oil. Soil and water contamination by crude oil is a sensitive issue, particularly in the Niger-Delta areas (Anon, 1985). The impact of contamination by spent automobile oil in the environment has been shown to be more widespread than contamination by crude oil (Atuanya, 1987). For instance, Nigeria was reported to account for more than 87 million litres of spent oil waste annually (Anon, 1985) and adequate attention has not been given to its disposal (Anoliefo and Vwioko, 1994). Contamination of soil and groundwater with spent automobile oil otherwise called “condemned” engine oil obtained after servicing of automobiles, is a common phenomenon in the mechanic village, popularly known as “site” in Abakaliki. The spent automobile oil is disposed off indiscriminately into the surrounding environment by “motor mechanics”. Reclamation of lands contaminated with waste organic materials coupled with enhanced awareness of their potential adverse effects on the human and environment, has received increasing international attention in recent years (Susan and Kelvin, 1993; NRC, 2002). Physical and chemical methods most widely used for land treatment of oil-based waste have been criticized as grossly inadequate and in-effective (Abu and Ogiji, 1996). Besides, these methods could result in further contamination of the environment (Steven, 1991). Since oil degradation is limited by temperature, pH, oxygen and scarcity of nutrients such as nitrogen and phosphorus (Leahy and Colwell, 1990; Ladousse and Tramier, 1991), bioremediation of organic wastes has been recommended (Atlas et al., 1991), as it is commonly accepted as the most efficient, environmentally safe and cost-effective method of treatment of hydrocarbon contaminated soils with simultaneous introduction of nutrients in the form of organic matter to the contaminated soil (Odookuma and Dickson, 2003). There is the need to reclaim such soils using cheap amendments such as burnt rice husk dust, fresh or unburnt rice husk dust and sawdust which, in the study area, are available to local farmers. Even though, reclamation of crude-oil contaminated soils has increased, little or no research has been carried out to reclaim the spent automobile oil-contaminated soils, which are abundant in many cities (Odokuma and Dickson, 2003).

The main objective of this study was to evaluate the productivity of spent automobile oil - contaminated soil amended with organic wastes.

The specific objectives of the work were to:

i.              assess the physicochemical properties of spent automobile oil-contaminated and organic wastes amended soil;

ii.             quantify the productivity of spent automobile oil- contaminated and organic wastes amended soil;

iii.            evaluate maize grain yields of a spent automobile oil-contaminated and organic wastes amended soil as well as;

iv.           make recommendation based on findings for improvement of a spent automobile oil contaminated and organic wastes amended soil.

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