Eficácia e pH de caldas de glifosato após a adição de fertilizantes nitrogenados e utilização de pulverizador pressurizado por CO 2

Abstract

This work was developed with the objective of evaluating the effi cacy and the pH of glyphosate spray solutions after the addition of nitrogen fertilizers and the use of CO 2 -pressurized sprayer. In fi eld conditions, two rates of glyphosate (360 and 720 g ha -1 ) were applied either alone or combined with two concentrations of urea (2.5 and 5.0 g L -1 ) or ammonium sulfate (7.5 and 15.0 g L -1 ). In laboratory, the pH of the glyphosate solutions was measured after using different concentrations of the product and nitrogen fertilizers and after using a CO 2 -pressurized sprayer. For all fi eld condition evaluations, the lowest glyphosate rate had higher biological effi cacy after the addition of ammonium sulfate (15 g L -1 ) to the spray solution. Urea (5 g L -1 ) promoted benefi ts only at the 28 th -day evaluation. In laboratory, the increase of glyphosate concentration promoted gradual acidifi cation of the spray solution, which stabilized at pH 4.5. Ammonium sulfate caused minor acidifi cation of the herbicide solution, whereas urea did not change the pH. The use of CO 2 -pressurized sprayer had small effect on the solution’s pH. Highest glyphosate effi cacy identifi ed after the addition of nitrogen fertilizers has little relation with changes on the solution’s pH.