INFLUENCE OF NON-IONIC SURFACTANTS, AMMONIUM SULPHATE, WATER QUALITY AND SPRAY VOLUME ON THE PHYTOTOXICITY OF GLYPHOSATE

Abstract

In field studies, the surfactants Tween 20, X-77 and Triton X-100 enhanced the effectiveness of low glyphosate rates on rape, wheat, oats and barley. In greenhouse studies, Triton X-A Special and Tween 20 enhanced glyphosate phytotoxicity in wild oats and barley. Concentrations of at least 0.5% vol/vol Tween 20 and 0.25% vol/vol Triton X-A Special were required for enhancement of glyphosate phytotoxicity in barley. The surfactants Renex 36, Cittowet Plus and Dupont WK reduced glyphosate phytotoxicity in field and greenhouse studies. Atplus 411F, Surfel and Triton X-114 also reduced glyphosate effectiveness in several field treatments. A number of other surfactants had no significant effects on glyphosate phytotoxicity. Glyphosate was less phytotoxic to barley when applied in tap water (45 ppm Ca⁺⁺ equivalent) compared to distilled water. With increasing spray volumes, the effectiveness of low rates of glyphosate was reduced and this reduction was more evident in tap than in distilled water. Ammonium sulphate in combination with Agral 90 enhanced glyphosate phytotoxicity in barley.