Tank-mixing foliar micronutrient fertilizers with glyphosate may reduce weed control because of antagonistic cations present in the spray solution. This research was conducted (1) to quantify the antagonism caused by various formulations of copper (Cu), iron (Fe), manganese (Mn), and zinc (Zn), and (2) to determine the extent that water conditioner adjuvants may prevent the antagonism from occurring. Most formulations of copper, iron, manganese, and zinc antagonized glyphosate efficacy on giant foxtail and velvetleaf. Formulations containing EDTA, HEDTA, or flavonol were the least antagonistic; those containing the sulfate salt or a lignosulfonic acid chelate were the most antagonistic. Tank mixtures including the adjuvant NT overcame the antagonism more often than those containing ammonium sulfate (AMS) or CANG. Two micronutrient blends, one with (MC) and one without (MS) the chelates citric acid and EDTA, both reduced glyphosate efficacy on giant foxtail and velvetleaf. The addition of AMS or NT to these blends increased velvetleaf control, but neither adjuvant overcame the antagonism.