Phytonutrient Effect of Velvet Bean (Mucuna Pruriens) Powder on Petroleum Hydrocarbon Impacted Soil

Crude oil stressed agricultural soil, make microbial activities less active due to contaminant concentrations which needed urgent attention for treatment. The velvet bean powder (VBP) was analyzed for its nutrients content of nitrogen 5.87 mg/kg, phosphorus 1.36 mg/kg and potassium 28.34 mg/kg. The samples contained fixed masses of soil 2000 g and crude oil of 500 g blended with different VBP proportion of 4:1, 8:2:1, 4:1:1, 8:2:3, and 4:1:2 respectively, option (A – E), and control option (A) without any form of treatment for an interval of 45 days. There was reduction under all conditions ranging from 5215 to 289 mg/kg with the most reduction in option (C, D, and E) containing 4:1:1, 8:2:3 and 4:1:2 corresponding to 96, 96, and 97.2% respectively. There was a surge in microbial growth even though there was evidence of hydrocarbons in the soil, the levels of nutrient interaction were highly significant (p<0.05). The pH levels increased with VBP application from 5.75 to 6.99 under all conditions. The observed changes in electrical conductivity (EC) were in the crude oil saturated soil control (option A) 15 and 45 days (709 and 877 μS/cm) respectively, and the treatment option C and E (613 and 692 μS/cm). The addition of VBP amendments resulted in a significant increase in TN, TP, and TK in option D and E ratios 8:2:3 and 4:1:2 respectively. This shows that VBP can provide favourable environment for the growth of microorganisms that facilitate the degradation of petroleum hydrocarbons in soil.