Study of the biochemical activity and plant growth promoting bacteria in soils polluted with oxyfluorfen

There is currently a great deal of information available about the toxic effects of oxyfluorfen on soil biochemical activity and microbial biodiversity. However, there is no information about how this herbicide affects plant growth promoting bacteria (PGPB) or their properties, such as biofilm formation, nitrogen fixation, siderophore and auxin production, and phosphate solubilisation. As such in this study an agricultural soil was polluted with the oxyfluorfen herbicide every 30 days at a dose of 4 L ha(-1) for a total period of 90 days. During this experimental period, the dehydrogenase activity was determined, a count and isolation of cultivable bacteria was performed, and the PGPB and their properties were characterized. The results indicated that oxyfluorfen inhibits the dehydrogenase activity, with this inhibition increasing with herbicide concentration in the soil (69.9% compared to non-polluted soil). It also causes changes in the population diversity of cultivable bacteria in soils. Regard to the evolution of isolated PGPB, it was found that oxyfluorfen induces the growth of nitrogen-fixing, biofilm-forming, and siderophore-producing bacteria, while negatively affecting the growth of auxin-producing and phosphate-solubilising bacteria. These results suggest that oxyfluorfen modulates the properties of PGPB in a concentration-dependent manner.