Castor oil plant seeds (Ricinus communis L.) were grown in spent lubricating oil (SLO) contaminated soil at concentrations of 1-6% (w/w, oil/soil). Plant height and stem girth were depressed by spent lubricating oil at concentrations of 2% (w/w) and above. One percent (1%) spent lubricating oil in soil promoted growth of plants when compared with control. Fresh and dry weights of R. communis pl...