2,4-D Interactions with Glyphosate and Sodium Bicarbonate

Abstract

2,4-D has been reported to antagonize glyphosate activity on grass weed species. In addition, sodium bicarbonate antagonized 2,4-D activity on broadleaf species. Experiments were conducted using Nuclear Magnetic Resonance (NMR) technology to evaluate interactions of 2,4-D dimethylamine and 2,4-D butoxyethylester formulations with glyphosate in solution. The 2,4-D dimethylamine formulation associated with glyphosate to form the dimethylamine salt of glyphosate. NMR spectra also showed that the molecular orientation of the glyphosate molecule was affected by the 2,4-D butoxyethylester formulation. The antagonist was not the active 2,4-D butoxyethylester molecule itself, but appeared to be due to an association of glyphosate with organic components in the 2,4-D butoxyethylester formulation. The molecular influence of sodium bicarbonate on technical grade 2,4-D free acid, and dimethylamine and butoxyethylester formulations was also evaluated. Sodium bicarbonate was found to react with the 2,4-D free acid and 2,4-D dimethylamine to form the sodium salt of 2,4-D. The 2,4-D butoxyethylester formulation did not react with sodium bicarbonate.