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

Abstract

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.

Impact of the Herbicide Oxyfluorfen on the Activities of Some Enzymes Found in Soil and on the Populations of Soil Microorganisms

“…A similar behavior has been noticed when the herbicide fomesafen has been used for the soil treatment [14]. The herbicide S-metolachlor revealed an inhibitory effect against dehydrogenase, the decrease in the activities the enzyme being dose-dependent [32]. Another herbicide, butachlor stimulated activity of dehydrogenase for soil under flooded conditions, but had a detrimental affect against dehydrogenase for un-flooded conditions [19].…”

“…A similar result indicating an increase in FA during 30-day incubation has been obtained when the herbicide fomesafen have been used [14]. Other studies have shown the inhibition of FA [32,74,75], respectively a stimulation of FA in samples of soil treated with other herbicides [22,60,71,76]. Application of the herbicide butachlor conducted to stimulation in the activity of phosphatase under un-flooded conditions and inhibition under flooded conditions [19].…”

“…On the contrary, application of the herbicide imazethapyr in a field trial in a clay loam soil at the recommended field rate led to an increase in PA [79]. When the herbicide S-metolachlor has been used, the activity of protease decreased initially and increased after 14 days of incubation [32]. Activity of protease presented an inconsistent response towards butachlor usage under both un-flooded and flooded conditions [19].…”

“…When the herbicides have been applied in high doses on the soil samples, the urease activity registered first a decrease followed by an increase. This behavior indicated that fomesafen and S-metolachlor had initially an inhibitory effect against urease, but this effect gradually disappeared with increasing incubation time [14,32]. Literature data also reveal that urease activity decreased with increasing the concentration of various herbicides applied on the soil samples [9,70,71].…”

“…This method proved to be useful for characterizing the interactions between pesticides and enzymes found in soil, such as contributing to the understanding of the factors determining the biological activity of pesticides. Molecular docking has been used to assess the interactions of the herbicides chlorsulfuron and nicosulfuron, and the fungicides difenoconazole and drazoxolon with bacterial chitinases [28,29], Bacillus pasteurii urease [30] and Proteus mirabilis catalase [31], respectively, of the herbicide S-metolaclor with enzymes found in soil (dehydrogenase, protease, phosphatase and urease) [32]. These studies illustrated the inhibitory effects of investigated pesticides on the enzymes activities and that herbicides had a higher inhibitory potential than fungicides.…”