Impact of Reglone® Herbicide Application on Soil Microbial Activity: An Assessment in the Context of Brazilian Family Farming

Family farming practices are subject to modification as new technologies become available. The act of weeding to remove weeds can require a significant investment of time from the farmer and thus has been supplanted by the use of herbicides. Such practices can cause health issues for the farmer and disrupt the soil's biological community, which could ultimately lead to a reduction in soil fertility over time. The present study aimed to evaluate the consequences of applying different concentrations of the herbicide Reglone® on soil microbial activity. Experiments were conducted with soil samples containing varying concentrations of Reglone®. The soil moisture was adjusted to 60% of its water holding capacity, and the microcosms were incubated for 28 days at 25°C. The results demonstrated that the concentration of 1.3 mg/kg, which is the Predicted Environmental Concentration of the active ingredient (diquat), did not impact soil microbial respiration in comparison to the control. However, concentrations two and three times higher resulted in a significant reduction in microbial activity, which may negatively impact the nutrient cycling and the agricultural efficiency of soils exposed to these herbicide concentrations, which are widely used for controlling weeds. It can be concluded that the application of the herbicide Reglone® exerts influence on soil microbial activity at dosages above the predicted concentration, which were 2.6 mg/kg and 3.9 mg/kg of the active ingredient. A decline in soil quality and agricultural productivity can have adverse consequences for farmers, potentially leading to reduced income and an exodus from rural areas.