Phytotoxicity in transgenic soybean treated with glyphosate doses

RR soy was designed to reduce costs and favour weed management using only one type of herbicide, the glyphosate. Although, there are just some few studies that actually evaluates the effect of this product on the physiology and final production of soybeans in northern Mato Grosso. The aim of this work was to verify the effects of the herbicide glyphosate molecule, on vegetative characteristics and productivity in transgenic soybean. The experiment was conducted at the Farm Água Viva, Sinop-MT. The experimental design was a randomized block design with five replications, with five treatments, three glyphosate concentrations (480 g ia.ha-1, 960 g ia.ha-1, 1920 g ia.ha-1) another treatment with mechanical control (hoe) and the control (no weed control). Was evaluated the following variables: phytotoxicity, plant height, chlorophyll content, fresh weight, dry weight and productivity. As for efficient control by glyphosate application at doses of 960 g ia.ha-1 and 1920 g ia.ha-1 significantly reduced weed populations up to 21 DAP. Phytotoxicity was found near the time of application, especially at the maximum concentration applied. The effect of the herbicide on the variable plant height was more pronounced at 21 DAA and the recommended concentration (960 g ia.ha-1) did not differentiate using the hoe. For fresh pasta, this was reduced with the application of herbicide and dry weight was not different between treatments. Productivity was higher in treatments with hoe, minimum and medium concentrations of glyphosate herbicide. The maximum concentration of the herbicide damaged the productivity as well as treatment unchecked, the less productive. For chlorophyll values glyphosate application promoted a significant reduction, which can be explained by the decrease in manganese uptake by the plant.