Glyphosate application using solution of urea + ammonium sulfate

Abstract

Several trials have been carried out for increasing glyphosate efficacy on weed burndown, including the addiction of ammonium sulfate and urea as adjuvants. On a physiological approach, there are explanations to complementary effect of these fertilizers when concomitantly added to herbicide spray solution. Therefore, three experiments were developed in field conditions with the objective of evaluating glyphosate efficacy for burning down different weed species by using solution of nitrogen fertilizers as spraying vehicles. Six treatments were evaluated, as follows: glyphosate (540 g a.e. ha^-1) application using water, solution of ammonium sulfate – AMS (15 g L^-1), solution of urea – U (5 g L^-1), solution of U+AMS (2.5 + 7.5 g L^-1) as spraying vehicles, glyphosate at 1080 g a.e. ha^-1 sprayed with water, and check without application. Treatment’s efficacy was evaluated on mixed community of weeds, Brachiaria decumbens and Sorghum halepense. The use of nitrogen fertilizer solutions as glyphosate spraying vehicles did not increase B. decumbens control. The lower rate of glyphosate had higher efficacy over mixed weed community and over S. halepense due to the use of ammonium sulfate (15 g L^-1) or U+AMS (2,5 + 7,5 g L^-1) solution as spraying vehicles. The positive results reached after glyphosate application with nitrogen fertilizers were also observed on the reduction of the mixed weed community fresh mass and for S. halepense fresh and dry mass.