The objective of this work was to evaluate the effect of contamination with oil of two soils of the Monagas state on the nodulation characters in the bean crop (
Vigna unguiculata
(L.) Walp.). The soils, viz, El Tejero (Tipyc-kandiustults) and Caripito (Tipyc-haplustepts) were used. A split-plot design was used with four replications. The four levels of oil contamination (0, 3, 6 and 9 %) were the main plots and the two soils were the subplots. The commercial inoculation with rizobia were not carried out. Harvest was made at 32 days after sowing. An analysis of variance was performed and the differences between treatments were detected by the Duncan's multiple range test. A 5 % level was considered significant. The biggest nodule weight was obtained in the control (0 % of oil contamination) followed by 3 % oil contamination and these two treatment overcame the nodule weight obtained at 6 and 9 % oil contamination being the two latter similar among them. At 0 and 3 % oil contamination, more nodules were produced in the Caripito soil than El Tejero one, having similar number of nodules both soils at 6 and 9 % oil contamination. At the El Tejero soil, there was more nodules in the control (0 % ) than at 3, 6 and 9 % oil contamination and at the Caripito soil there was more nodules in the control followed by 3 % oil contamination and this latter have more nodules than 6 and 9 % oil contamination, having the two latter similar numbers of nodules. In conclusion, the nodule production was inhibited from 6 % oil contamination indicating that oil impedes the fixation of atmospheric nitrogen, therefore the association rizobia:legume is ineffective in highly polluted soils with oil.
