Use of Biostimulants Obtained from Sewage Sludge for the Restoration of Soils Polluted by Diuron: Effect on Soil Biochemical Properties

Abstract

The use of biostimulants in the bioremediation of polluted soils in order to eliminate/reduce the toxic effects of pesticides on the soil is currently a very common environmental practice. In this study, we studied the bioremediation effect of three biostimulants obtained from sewage sludge by way of an enzymatic hydrolysis and fermentation process in a diuron-contaminated soil for 55 days under laboratory conditions. During this period of time, the enzymatic activities, bacterial community and the evolution of diuron in the soil were analyzed. Compared with the unpolluted soil, the application of diuron decreased the dehydrogenase, β-glucosidase and phosphatase activities by 60%, 40.7%, and 60.6%, respectively. The Gram-positive bacterial population was decreased by 48.5%, while the Gram-negative population was decreased by 57.7% and the fungal population was decreased by 54.3%. The application of the three biostimulants to the soil decreased the diuron concentration. However, this decrease was higher when the biostimulant obtained by enzymatic hydrolysis was applied. This may be due to the fact that this biostimulant contains a higher quality of low molecular weight proteins than the other two biostimulants obtained by fermentation processes.

Response of Biochemical Properties in Agricultural Soils Polluted with 4-Chloro-2-methylphenoxyacetic Acid (MCPA) under Severe Drought Conditions

“…Several authors have attempted to explain this decrease in the soil biochemical properties after the addition of a pesticide [6,16,28,31]. These authors observed decreases in biochemical properties and microbial biodiversity in soils contaminated with an oxyfluorfen herbicide or with chlorpyrifos and cypermethrin insecticides, suggesting that the inhibition of the biochemical properties of the soil is intimately related to the inhibition of microorganisms involved in the C, N, P and S cycle that are intolerant of, or susceptible to, the pollutant added to the soil as well as to the application dosage of said contaminant.…”

“…Urease, β-glucosidase, phosphatase and arylsulfatase enzymes are involved in the cycling of principal nutrients such as N, C, P and S [15]. Therefore, since such activities are commonly used in ecotoxicological tests to evaluate the behavior and influence of chemicals on soil systems, it may be useful to study them as early indicators of soil changes [6,16,17].…”

Study of the Biochemical Activity and Plant Growth Promoting Bacteria in Soils Polluted with Oxyfluorfen

“…To determine the microbial activity of the soil, the dehydrogenase enzymatic activity was used. This enzyme is related to oxidative phosphorylation, making it a good indicator of microbial activity (Tejada et al, 2023).…”