Glyphosate effects on non-target plants: collateral impacts on elemental composition and growth of yerba mate

This work investigated collateral effects on non-target yerba mate (Ilex paraguariensis A. St.-Hil) plants when using glyphosate for weed control; growth and leaf elemental composition were examined. Special emphasis was placed on examining the heavy metals Cd and Pb due to regulations defining maximum limits in South American infusion products. The experiment was conducted in pots using glyphosate [applied to Congo grass (Brachiaria ruziziensis), soil surface application, and control], two P rates (with and without P), two clonal yerba mate cultivars, and two different soils (basalt- and rhyodacite-derived). When using glyphosate to control Congo grass, total dry matter and basal diameter of yerba mate plants decreased. This effect was enhanced by lack of P. Collateral effects of glyphosate use resulted in increased K, P, and Cu in clone 1 cultivated in basalt-derived soil; with rhyodacite-derived soil, increased levels of Ca, Mg, Mn, Fe, and Zn were observed in clone 1, while clone 2 displayed increases in B, Cd, and Pb. These observations demonstrate that glyphosate use to control undesirable plants can impact initial development and elemental composition of yerba mate, with variations between cultivars and soil type.