Effects of organic manures on the physicochemical properties of crude oil polluted soils

Abstract

The impact of crude oil pollution on the edaphic physicochemical parameters and the influence of incorporation of different types of organic manures in the polluted soils were investigated. The factorial set of treatments were six levels of crude oil pollution (0, 30, 60, 90, 120 and 150 ml), while amendment treatments were done after two weeks of pollution treatment, using the following organic manures: poultry manure (PM), cow dung manure (CM), saw dust manure (SM), poultry + cow dung manure (PM + CM), poultry + saw dust manure (PM + SM) and cow dung + saw dust manure (CM + SM) with two sets of control: pollution + no amendment and no pollution + no amendment. Results indicated that crude oil pollution significantly affected the edaphic physicochemical parameters at P ≤ 0.05. The percentage total organic carbon, total organic matter and total hydrocarbon content (THC) significantly increased two weeks after crude oil pollution while the pH, percentage total nitrogen, phosphorus and exchangeable bases (Ca, K and Mg) significantly decreased. The results also showed that the different amendment treatments significantly decreased crude oil toxicity at different degrees by improving the nutrient content and decreasing the total hydrocarbon content of the soil. The results indicated the order of their remediation potential as PM > PM+CM > CM > PM+SM > CM + SM > SM. Thus, PM followed by PM + CM are highly recommended for amendment of crude oil polluted soil for enhanced agronomic performance due to their narrowing effect on carbon : nitrogen (C:N) ratio which is an index of improved soil fertility. Key words: Crude oil, organic manures, amendment, physicochemical parameters, toxicity