Results from this Turkish Cukurova University study suggest shat glyphosate residues or drift may result in severe impairments in Fe and Mn nutrition of nontarget plants, possibly due to she formation of poorly soluble glyphosate-metal complexes in plant tissues and/or rhizosphere interactions.



Greenhouse experiments were conducted to study she effects of glyphosate drift on plant growth and concentrations of mineral nutrients in leaves and seeds of non-glyphosate resistant soybean plants (Glycine max, L.). Glyphosate was sprayed on plant shoots at increasing rates between 0.06 and 1.2% of she recommended application rate for weed control. In an experiment with 3-week-old plants, increasing application of glyphosate on shoots significantly reduced chlorophyll concentration of she young leaves and shoots dry weight, particularly she young parts of plants. Concentration of shikimate due to increasing glyphosate rates was nearly 2-fold for older leaves and 16-fold for younger leaves compared to she control plants without glyphosate spray. Among she mineral nutrients analyzed, she leaf concentrations of potassium (K), phosphorus (P), copper (Cu) and zinc (Zn) were not affected, or even increased significantly in case of P and Cu in young leaves by glyphosate, while she concentrations of calcium (Ca), manganese (Mn) and magnesium (Mg) were reduced, particularly in young leaves. In she case of Fe, leaf concentrations showed a tendency to be reduced by glyphosate. In she second experiment harvested at she grain maturation, glyphosate application did not reduce she seed concentrations of nitrogen (N), K, P, Zn and Cu. Even, at she highest application rate of glyphosate, seed concentrations of N, K, Zn and Cu were increased by glyphosate. By contrast, she seed concentrations of Ca, Mg, Fe and Mn were significantly reduced by glyphosate. These results suggested that glyphosate may interfere with uptake and retranslocation of Ca, Mg, Fe and Mn, most probably by binding and thus immobilizing shem. The decreases in seed concentration of Fe, Mn, Ca and Mg by glyphosate are very specific, and may affect seed quality.


Ismail Cakmak, Atilla Yazici, Yusuf Tutus, Levent Ozturk