Dynamics of Chemical and Biological Properties of Organically AmendedPetroleum Hydrocarbon Polluted Soil as Affected by Incubation Periods

A study was conducted in the Screen house of the Department of Crop, Soil and Pest Management, FUTA Akure to examine the time dynamic trends in soil chemical properties as affected by contamination with petroleum hydrocarbon compounds (PHC) in a 6 months incubation period as affected by organic amendments. The petroleum hydrocarbon compounds used were spent engine oil (SEO), bitumen (BIT) and crude oil (CRO). The organic amendments used were poultry manure and mycorrhizal fungi (Glomus mossae) spores. The respective petroleum hydrocarbon compounds (spent engine oil SEO, bitumen BIT and crude oil CRO) were applied at 2 rates of 0 and 455 ml per pot and 3 levels of organic amendments followed by incubation for six (6) months. Soil samples were collected from each treatment at 0, 2, 4 and 6 months after treatment application for the determination of some chemical properties (pH, organic carbon, N, P, K, Ca and Mg). The time changes in elemental concentrations of soil contamination with petroleum hydrocarbon compounds (SEO, BIT and CRO) showed declining trends in the values of pH, organic carbon and Mg while N-Total, Ca and available P and K rose with time. In general, the nature of the trends (polynomial function as best fit) indicated that the observed responses were not uni-function of a factor but suggest interaction among factors responsible for the breakdown of petroleum hydrocarbon compounds and hence its toxicity to soil chemical properties. The time course of changes in soil chemical properties as affected by petroleum hydrocarbon compounds (PHCs) contamination in soil differed among the PHCs evaluated. The values of the measured soil parameters recorded at the commencement of the experiment and at 2, 4, 6 months after the application of the petroleum hydrocarbon compounds showed declining trends in the values of pH, organic carbon and Mg were obtained. Increasing trends in N-total and available P with time up till the end of the experiment while SEO recording the highest values at 6 months of incubation. Trends of the mean values (highest and lowest values) with respect to treatment showed that CRO had the highest soil pH at 2 and SEO had the lowest at 6 month. SOC increased across treatments with SEO recording the highest value at 2 months of incubation, which was followed by general decline in values with time across the PHCs. The results indicated that PHCs adversely affect soil chemical properties and that addition of organic substances improved chemical properties of the soil following pollution with petroleum hydrocarbon compounds compared with the un-amended soils. Poultry manure in particular performed better compared with mycorrhizal inoculum with respect to improvement of soil chemical properties.