Response of edaphic biostimulants obtained by fermentation processes in an oxyfluorfen-polluted soil: Effect on biological properties

We report a study of the bioremediation capacity of two biostimulants obtained from sewage sludge by fermentation processes in a soil polluted by oxyfluorfen at a rate of 4 L ha-1 over a 70-day period under laboratory conditions. The effects thereof on enzymatic activities, the soil bacterial community structure and the evolution of oxyfluorfen in soil are determined. Soil biological parameters were found to be inhibited in oxyfluorfen-polluted soil. At the end of the experiment, and compared with the control soil, dehydrogenase, urease, ß-glucosidase, and phosphatase activities in the oxyfluorfen-polluted soil decreased significantly by 58.3%, 30.4%, 44.7%, and 48%, respectively. The application of oxyfluorfen caused a decrease in the relative abundance of the Firmicutes (24.5%) and Acidobacteria (8.3%) phyla, and an increase of 21.9% in the relative abundance of the Gaiellales order (Actinobacteria phylum). The application of both biostimulants to the soil caused stimulation only in soil dehydrogenase activity and a change in the bacteria population, observing an increase in the relative abundance of the Bacteroidetes, Chloroflexi and Proteobacteria phyla and a decrease in the relative abundance of the Acidobacteria and Actinobacteria phyla. The relative abundance of the Chloroflexi, Firmicutes and Proteobacteria phyla increased when applying the experimental biostimulants in the polluted soil. At the end of the experiment, the oxyfluorfen concentration decreased in the polluted soil (25%) and amended with biostimulants (37.5%). These results suggest that the use of both biostimulants with higher amounts of low molecular weight proteins and peptides has a positive effect on the remediation oxyfluorfen-polluted soils.