Effects of Soil Amendment on the Toxicity of a Two- Month Old Waste Engine Oil-Polluted Soil on Solanum esculentum Linn

Abstract

This study investigated the effect of sawdust on the toxicity of waste engine oil- polluted soil on Solanum esculentum grown at various concentrations of waste engine oil and changes in the physicochemical properties of soil. This was with a view to assessing the soil remediation potentials of sawdust in waste engine oil polluted-soil. This study was carried out in the screen house of the Faculty of Agriculture, Obafemi Awolowo University, Ile-Ife. Waste engine oil sample was pooled from a heavy duty vehicles auto mechanic workshop in Sabo, Ile-Ife. Six concentrations of waste engine oil 0%, 1%, 2%, 3%, 4% and 5% were used to contaminate 3 kg of air-dried soil in perforated buckets. Another set of pots containing 3 kg of air-dried soil were also contaminated with six concentrations of waste engine oil but amended with 20 t/ha of sawdust. Each treatment was replicated thrice in a Completely Randomized Design. Nursery bed was prepared for the tomato variety (Roma VF) obtained from the National Horticulture Research Institute, Ibadan. With five seeds planted per hole at the depth of 3 cm. Two weeks after germination of the seeds in the nursery bed, the seedlings were transplanted into the perforated buckets at rate of 2 seedlings per pot. The growth parameters such as plant height, number of leaves and number of branches were measured weekly for 5 weeks. At the end of the five weeks, total harvesting of plants and sorting into roots and shoots was carried out. Pre and post cropping analyses of soils were done to determine the heavy metal content and physicochemical properties of the soils using standard methods. Plant parts nutrient content and plant heavy metal content were also analysed using standard method. The data obtained were subjected to appropriate descriptive and inferential statistical analyses.

After five weeks growth in the soils treated with 5% waste engine oil, growth performance of tomato was significantly (p< 0.05) higher in sawdust treated waste engine oil- contaminated soil. Results showed that addition of sawdust increased the soil nutrient status as well as plant nutrient uptake of Solanum esculentum in waste engine oil- contaminated soil. At 5% waste engine oil contamination level, plant nutrient uptake was significantly (p< 0.05) higher in waste engine oil- contaminated soil treated with sawdust (nitrogen: 2.16%; potassium: 0.43%; magnesium: 0.22% and calcium: 0.71%) than in soils treated with only waste engine oil (nitrogen: 0.58%; potassium: 0.11%; magnesium: 0.06% and calcium: 0.20%).

This study concluded that sawdust has the potential of amending waste engine oil- contaminated soil for improved nutrient uptake by tomato. Though, in the non-contaminated soil samples, sawdust did not significantly improve nutrient availability to tomato.

Keywords: Engine-oil, Farmland, Contaminated, Pollution, Amendment, Sawdust.