Assessment of the Effect of Application of the Herbicide S-Metolachlor on the Activity of Some Enzymes Found in Soil

Herbicides are being used more and more to increase productivity in agriculture, but their excessive has been shown to lead to adverse effects on the environment, especially on the soil. Within this study the effect of the herbicide S-metolachlor on the activity of several enzymes (dehydrogenase, protease, phosphatase and urease) found in the loamy-clayey soil has been analyzed. There were seven experimental variants corresponding to the untreated soil and to the application of six distinct doses of S-metolachlor on soil samples maintained in laboratory conditions. Biochemical analyzes have been performed to assess the activities of the investigated enzymes at 7, 14 and 21 days, respectively, and several physiochemical parameters of the soil have been also monitored during these experiments. The data obtained in the experimental determinations were subjected to statistical analysis such as to evaluate if the changes in the activities of enzymes are significant and to establish if there are correlations between the evolution of analyzed enzymatic activities and the physicochemical parameters of the soil. Molecular docking approach has been also used to assess the interactions between the herbicide and investigated enzymes. The activities of studied enzymes decreased in a dose-dependent manner when the herbicide was applied. More than 21 days were necessary to recover the activities of dehydrogenase and protease in the soil treated with S-metolachlor, the activity of protease was recovered after 14 days and the activity of urease was recuperated after 7 days of incubation. This study also emphasized significant correlations between the enzymatic activities and some physicochemical parameters of the soil: pH, moisture, organic matter, nitrogen level and available phosphorus.