Selectivity of Herbicide and Rhizospheric Microbial Activity on Hymenaea corbaril L. Seedlings

Current knowledge about the behavior of forest species under herbicide treatment regarding selectivity, resistance, and fitotoxic effects is insufficient. This study assesses the selectivity of sulfentrazone and glyphosate on Hymenaea courbaril L. seedlings (jatoba) and the effects of this herbicide on the rhizospheric microbial activity of those plants. For this assessment, two experiments were conducted. In the first one, 10 treatments were compounded by the combination of two herbicides (glyphosate and sulfentrazone) applied in five doses (0.00, 0.09, 0.18, 0.35, and 0.70 L ha(-1)). The second experiment assessed effects of the combination of five doses of the herbicide sulfentrazone and two types of substrate (rhizospheric and nonrhizospheric cultivated with jatoba seedling). To assess the selectivity of seedling to the herbicide, visual assessments of toxicity were carried out 15, 30, 45, and 60 days after the application. To determine the effect of sulfentrazone on rhizospheric activity, the basal respiration and of microbial biomass carbon (CBM) associated with substrates was evaluated. A good tolerance of the seedling with the herbicide was observed even at higher doses, indicating potential use in control of weeds in areas of jatoba planting in the initial phase of development. Regarding microbiological indicators, it is verified that the evolution of carbon dioxide carbon (C-CO2) and CBM were effective in the presence of herbicides, which can constitute auxiliary tools for environmental-impact monitoring of the herbicides.