Effects of oil pollution on mycorrhizae activity and growth of corn (Zea mays)

There are well documented reports on improper disposal of vegetable oil after domestic usage. This ultimately causes oil pollution and affect soil physical properties by clogging pore spaces. Reduced soil aeration and water infiltration are often the consequences of clogged soil. Thereby, affecting soil microbial activities and plant growth. A symbiotic association (mycorrhizae) between plant roots and fungi has largely been used in agriculture to enhance plant growth. However, the interactions between mycorrhizae and oil from domestic wastes have not been clearly elucidated. Therefore, this study was conducted to investigate the effects of mycorrhizae as a bio-fertilizer on the growth of corn (Zea mays) in oil polluted soil. Also, to investigate the effects of oil pollution on plant growth. The experiment was conducted twice in vitro using a growth chamber set at 12 hours light duration at 25⁰ C and 12 hours of darkness at 23⁰ C with 4 treatments. Each treatment contained four potted corn seedlings planted in potting mix soil. 15g of mycorrhizae was added to three of the treatments, while no mycorrhizae were added to treatment 4 to serve as control. Afterwards, 500mL of water was added to the plastic trough containing each treatment. 5mL of vegetable oil was added to treatment 1, 1mL of oil to treatment 2. Treatment 3 has mycorrhizae, but no oil. Treatment 4 has no mycorrhizae and no oil. The growth parameters used were plant height (cm), stem width (cm), number of leaves and canopy spread (cm). The mean of each parameter per treatment was calculated. Remarkable increase in plant height, stem-width and canopy spread were observed in all treatments except treatments 1 and 2. Of the four corn plants in treatment 1 (5mL of oil with mycorrhizae), only one germinated (25% germination rate) and grew with a height of 33cm, stem-width of 1.3cm and canopy-spread of 20.5cm. 100% seed germination and remarkably higher growth were observed in treatments 3 and 4 compare to treatments 1 and 2. Crops under severe stress condition of oil pollution possess a limited amount of nutrient uptake, possibly due to the reduced amount of soil water and mineral absorbed by the host plant roots which affects the plant's metabolism. This study suggests that improper disposal of vegetable oil should be discouraged, as it affects mycorrhizae activities and stunt plant growth.