Oxyfluorfen and Linuron: Residual Effect of Pre-Emergence Herbicides in Three Tropical Soils

Knowledge about the residual effect of herbicides is important in order to increase agronomic efficacy and reduce environmental problems. Therefore, the objective of this study was to evaluate the residual effect of oxyfluorfen and linuron in three soils. Pots of 0.35 dm3 were filled with three Brazilian soils: Ultisol, Oxisol, and Inceptisol. Then, the herbicides were applied at different times at 0, 15, 30, 45, 60, 90, 120, 150, 180, and 200 days and the bioindicator species of linuron and oxyfluorfen were sown. Then, the injury was evaluated at 7, 14, and 21 days after emergence (DAE) to find the half-life of the herbicide residue level (RL50) and the dose of herbicide that provides a 50% reduction in dry matter (GR50). In the soil with oxyfluorfen application, the RL50 at 21 DAE was 59, 57, and 51 days and GR50 was 49, 47, and 31 days for Ultisol, Oxisol, and Inceptisol, respectively. Soils with linuron application had RL50 of 75, 92, and 149 days and GR50 of 52, 48, and 120 days for Ultisol, Oxisol, and Inceptisol, respectively. The higher organic matter and clay content of Ultisol compared to Oxisol and Inceptisol resulted in a lower residual effect of linuron. There was little difference between soil type and the residual effect of oxyfluorfen, which may be related to the physicochemical characteristics of the molecule.