Mark VanGessel, Extension Weed Specialist; firstname.lastname@example.org
I have looked at some soybean fields with heavy volunteer corn pressure. The corn is Roundup Ready, so none of the glyphosate formulations will control it. The postemergence grass herbicides (Select Max, clethodim, Assure II/Targa, Fusilade, or Poast) will control emerged corn. In a trial at Purdue University, control was slightly better when these products were applied to 10 to 15 inch tall corn compared to 22 to 25 inch tall corn. If tankmixing these products with glyphosate, many of them recommend including an adjuvant and nitrogen regardless of the glyphosate formulation. Be sure to read the labels.