Effect of Petroleum Crude Oil on Mineral Nutrient Elements, Soil Properties and Bacterial Biomass of the Rhizosphere of Jojoba

Aims: This study is to evaluate the effect of petroleum crude oil contaminated soil on the mineral nutrient elements, soil properties and bacterial biomass of the rhizosphere of jojoba plants (Simmodsia chinensis).
Methodology: A pot experiment was carried out. The soil was treated with different levels of crude oil: 1, 2 and 3% v/w either alone or in combination with inorganic fertilizers.
Results: Malondialdehyde (MDA) concentration increased in jojoba leaves when grown in petroleum oil polluted soil especially at 2% and 3% crude oil. It was noted that, Na, Mg and Ca decreased while K increased in shoots of jojoba. In roots Na and Ca increased however K and Mg decreased with increasing crude oil concentration in the soil. Heavy metals, Cu, Mn, Cd and Pb increased in both shoot and root with increasing crude oil concentration while, Zn decreased comparing with the control. In soil, N and K decreased meanwhile Cu, Fe, Mn and Zn as well as organic matter increased with increasing crude oil concentration. Soil was free from P while, the addition of inorganic fertilizers improved P content. Bacterial account was significantly increased at the end of the experiment at 1% and 2% crude oil especially after addition of inorganic fertilizers. The electric conductivity and MDA of the leaves increased with increasing crude oil concentration. The addition of inorganic fertilizers to crude oil contaminated soil decreased the electric conductivity and MDA comparing with crude oil only.
Conclusion: The observed changes in composition of mineral elements in jojoba plants in the present study could be attributed to the cell injury and disruption in the cell membrane, heavy metal accumulation and toxic nature of the petroleum oil. Also this study has demonstrated that soil contamination with crude oil has a highly significant effect of reducing some mineral element composition of Jojoba plants.