Effects of used engine oil polluted-soil on seeds’ germination and seedlings’ growth characteristics of some tropical crops

The ability of Phaselous vulgaris, Zea mays L., Solanum lycopersium and Sorghum saccharatum to germinate and grow in unpolluted soils, 1% w/w and 2% w/w used engine oil polluted soils were investigated. Twenty (20) seeds of each plant species were sown in the various polluted and unpolluted soils and germination were monitored for 7 days, and subsequent growth for 7 weeks. The numbers of germinated seeds were counted daily from the 2nd to the 7th day, and percentage germination recorded. Plants' growth parameters (shoot heights and leaf area) of the seedlings were assayed and recorded on the 3rd, 5th and 7th week. Percentage germination varied for the various plant seeds. S. saccharatum had the best germination in polluted and unpolluted soil with 100%, 95% and 90% germination as against the least germination 100%, 65% and 25% observed in S. lycopersium in unpolluted, 1% w/w polluted and 2% w/w polluted soils, respectively. In terms of growth, P. vulgaris had the best performance in unpolluted and polluted soils with mean shoot heights of 47.8 cm, 41.3 cm and 28.4 cm as against S. lycopersium with mean shoot heights of 10.8 cm, 5.8 cm and 3.6 cm in unpolluted, 1% w/w and 2% w/w polluted soils, respectively at the end of the study. The results of this study showed that used engine oil inhibited the germination of these seeds in a dose depended manner, and that inhibition of seeds' germination does not connote inhibition of subsequent growth. This highlights the need to prevent agricultural soil pollution with used engine oil.