Roundup Ready soybeans may require a postemergence application of glyphosate and a manganese application about the same time. These glyphosate products can be tankmixed with manganese with some precautions. The manganese products can bind with glyphosate in the spray tank and reduce glyphosate’s effectiveness. The form of manganese has an impact. Manganese chelated with EDTA does not appear to affect the performance of glyphosate, but other forms of manganese do. The addition of ammonium sulfate can overcome the problem. Thus, when tankmixing glyphosate with manganese, use an EDTA form of manganese or add ammonium sulfate to overcome the reduced weed control. When using ammonium sulfate be sure to add the ammonium sulfate to the tank first and add the glyphosate last.
