Tolerance Potentials of Cocoa (Theobroma cacao) in Hydrocarbon Polluted Soils

Abstract

In the present study the tolerance potentials of T. cacao in hydrocarbon polluted soil was evaluated. Top soil (0-25 cm depth) was collected from three points, bulked to form composite soil sample. Eight kilograms of the soil sample each were weighed into twenty five (25) perforated bags. The bags were polluted with 0 ml/kg, 50 ml/kg, 100 ml/kg, 150 ml/kg and 200 ml/kg of crude oil respectively with five replicates for each concentration and allowed for 2 weeks before planting. Three seeds of cocoa were sown in each of the polythene bags. Water was applied every three days to keep the soil moist.  The results showed that cocoa plants at 8 weeks after planting (WAP) had significantly higher height (P<0.05) than those of 4 weeks after planting (WAP). The plant height, petiole length, number of vine had no significant difference (P>0.05) at the different concentrations of crude oil. While the leaf length, leaf area, number of leaves, leaf width and vine length shows significant difference (P<0.05) and in treatment dependent manner. The results also showed that the concentrations of Cu, Ni, Cr and Zn in the polluted soils were treatment dose dependent but did not significantly affect the plant tolerance at P<0.05. The pH, phosphorus, nitrogen content, and other physicochemical properties of the soil were not significantly affected by the crude oil treatment. The T. cacao has been found to be tolerant to hydrocarbon polluted soil environment, its usage in oil spill impacted area should be encourage.