Effects of two surfactant series on the absorption and translocation of 14C-glyphosate in sicklepod and prickly sida

The weed species, prickly sida (Sida spinosa L.) and sicklepod (Senna obtusifolia L.), were treated with ¹⁴C-glyphosate alone and formulated with different polyethlylane oxide (PEO) surfactants in tallow amine ethoxylate and non-ionic alkoxylate series to determine the amount of ¹⁴C-glyphosate absorption and translocation. The surface tension, contact angle, and ¹⁴C-glyphosate distribution were significantly affected by both the presence of different waxes on the plants and by the addition of surfactants to the glyphosate. The surface and contact angle values of the surfactants, with and without glyphosate, showed a significant increase as the PEO number increased in both surfactant series. A higher absorption of the ¹⁴C-glyphosate was recorded for S. spinosa compared with S. obtusifolia. The absorption and translocation of the ¹⁴C-glyphosate increased with the increase in the PEO number of tallow amine ethoxylate. In the case of the non-ionic alkoxylate surfactant series, an increase in the absorption of ¹⁴C-glyphosate was recorded when the surface tension and contact angle values decreased. There was no significant difference in the translocation values obtained in the two species after the addition of the surfactants. The amount of ¹⁴C-glyphosate absorbed by the treated leaf was significantly higher in the case of S. spinosa compared with S. obtusifolia. A linear relationship was observed with the physical properties, ¹⁴C absorption, and the efficacy of glyphosate with the addition of the non-ionic alkoxylate surfactant series. The percentage control was higher with the higher PEO surfactant in the tallow amine ethoxylate surfactant series and with the lower PEO surfactant in the non-ionic alkoxylate surfactant series as the two series are chemically different.