Shortly after the introduction of Roundup Ready soybean, questions arose whether these varieties and/or glyphosate applications to them alter manganese relations compared to conventional soybean varieties. It is well documented that glyphosate forms complexes with manganese and other metal cations. These complexes reduce glyphosate activity when the antagonistic cations are present in water used as a carrier.
Iowa State University
Hartzler, Robert G., "Glyphosate and Manganese Interactions in Roundup Ready Soybean" (2010). Integrated Crop Management News. 488.