ABSTRACT
104The purpose of this study was to evaluate the rainfastening effect of four adjuvants on glyphosate (N-[phosphonomethyl] glycine) phytotoxicity.
Elymus repens (Agropyron repens) was grown from single-node rhizome fragments in 8 ℓ pots for 6 months. They were then cut down and sprayed with three doses of glyphosate when the regrowth reached the 5–6 leaf stage. Glyphosate was applied as Roundup or as a standard formulation (Mon 0139 + 0.5% G3780A) either alone or in mixture with four adjuvants, some of which were claimed to be rainfasteners. 1 Rain was applied 45, 180, and 360 min after spraying (3.5 mm at an intensity of 25 mm/hr). The rainfastening effect of the adjuvants was assessed by recording the fresh weight of the treated plants and the fresh weight of both the first and second regrowth.
Three of the adjuvants improved the rainfastness of the glyphosate formulation while the fourth, claimed to be a rainfastener, did not affect the rainfastness of glyphosate. The three adjuvants which increased the rainfastness also slighty increased the effect of glyphosate in the case of no rainfall.
The results are discussed in relation to the different formulation of the four adjuvants.
