Revista Brasileira De Herbicidas 2001; 2(3): 119-124
Influence of simulated rain on the efficacy of different formulations and doses of glyphosate
DOI: 10.7824/rbh.v2i3.360
The effects of simulated rainfall on the performance of different formulations and doses of glyphosate in the control of Brachiaria plantaginea (Link) Hitchc. were studied under field conditions. The experimental design used was that of a split-block in strips. The strips consisted of the irrigation factor. Formulation and doses were arranged in a factorial arrangement, with four replications. Plots measured 2.5 m x 4.0 m. The irrigation factor consisted of a simulated rainfalI of 20 mm applied at different timings (l, 2, 4 and 24 hours after treatment application) which was carried-out using a system of sprinklers. Rainfall simulated less than 4 hours after spraying the products reduced the phytotoxicity of the ammonium salt formulated as water auto-dispersible granules (WG) to a greater extent than that of the potassium and isopropylamine salts formulated as soluble concentrate (SC) when alI compounds were applied at the rate of 360 g/ha acid equivalent. Higher rates of glyphosate reduced the negative rainfall effect. The efficiency of the compound was affected by the type of salt and formulation. The isopropylamine and the potassium salts both as SC formulation, presented daily control rates higher than the isopropylamine as WG formulation. The final control of B. plantaginea was also affected by the formulation; both the isopropylamine salt and the potassium salt formulated as SC showed control rates higher than the ammonium salt formulated as WG. In conc1usion, glyphosate efficiency is determined by its salt type, formulation, rate, and time interval between its application and rainfall. These factors affect glyphosate absorption and translocation determining the final controllevel of the studied species.
88