CURVA DOSE-RESPOSTA DO HERBICIDA METRIBUZIN E A CULTURA DO PEPINO COMO PLANTA BIOINDICADORA PARA DIFERENTES TIPOS DE SOLOS DO ESTADO DE GOIÁS

Abstract

The use of pre-emergent herbicides requires knowledge of the interaction between the molecule and soil attributes to ensure biological efficacy and environmental safety. The objective of this work was to evaluate the influence of the physicochemical attributes of five soil classes on the residual effect of metribuzin, using cucumber (Cucumis sativus) as a bioindicator plant. The experiment was conducted at the Instituto Federal Goiano, in a completely randomized design with four replications. Five doses of metribuzin (0; 0.25x; 0.5x; 1.0x and 2.0x) were tested in five soils: RQo, CXbd, LVd, LVdf and LVw. Visual phytotoxicity assessments were performed at 7, 14, 21 and 28 days after application (DAA), and the dry biomass of the aerial part was determined at the end of the period. The results indicate that clay content and CEC were strongly associated with herbicide bioavailability. In sandy soil (RQo), total plant death was observed at all treated doses from 14 DAA onwards. In contrast, clay-oxidic soil (LVdf) provided greater protection to the bioindicator, allowing plant survival at the lowest dosage up to 28 DAA. Dry biomass data confirmed the severe herbicide damage, showing a 100% reduction in plant mass in almost all treated matrices, directly correlating with the visual collapse of the bioindicator. It is concluded that soils with greater buffering capacity retain metribuzin more intensely, attenuating its immediate phytotoxicity, while light-textured soils enhance the product's action due to low adsorption.