Abstract

HERNANDEZ-VALENCIA, Ismael; LAREZ, Luis Manuel  and  GARCIA, José Vicente­. Toxicity of a soil contaminated with crudes and its effect on the germination of two tropical pastures. Bioagro [online]. 2017, vol.29, n.2, pp.73-82. ISSN 1316-3361.

Oil production in Venezuela has generated a variety of environmental impacts, including contamination of ecosystems and land under agricultural use. In order to establish the impact of oil contamination on the germination of Megathyrsus maximus and Urochloa brizantha, two tropical pastures used as fodder, short-term toxicity bioassays were performed in which seeds of both grasses were exposed to soil contaminated with increasing concentrations of four crude oils with different API gravity. Crude oils were extra heavy crude (9.3 ° API), heavy crude (12.1 ° API), medium crude (27.0 ° API) and light crude (30 ° API). At the end of the trial the germination percentage of seeds, radicle elongation and germination index were evaluated. The results showed that a) with the increase of the crude concentration decreased the number of germinated seeds, radicle elongation and germination index, b) as the API gravity decreased, the seeds achieved germination at higher concentrations of the crude oil, c) for the same type and concentration of crude, both species presented a response similar in germination percentage, radicle elongation and germination index, and d) EC₅₀ were higher and similar between extra heavy and heavy crude, and smaller and similar between medium and light crude, confirming that the former are the less toxic crudes.

Keywords : Bioassay; germination; Megathyrsus maximus; Urochloa brizantha.

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