Effect of Water pH on the Effectiveness of the Herbicide Glyphosate, Fluazifop-p-butyl and Bentazon

Abstract

Three experiments were conducted to evaluate carrier pH effect on the efficacy of three postemergence herbicide formulations glyphosate monoammonium salt (Roundup Max® 680 SG), Fluazifop-p-butyl ester (Fusilade 12.5 EC®), and Bentazon sodic salt (Basagran 48 EC®). Each herbicide was an experiment and for each herbicide, water pH of 4.50, 6.50 or 8.50 were evaluated. Each pH was used with the recommended dose of the formulator, and 75% of that dose for weed control. In addition, there was an unapplied plot (control) that was not used in the statistical analysis. The variable evaluated was weed control; for glyphosate and Fluazifop-p-butil the weed applied was African bermudagrass (Cynodon nlemfuensis Vanderyst), for Bentazon it was butter daisy (Melampodium divaricatum [Rich.] DC). Glyphosate was applied at 2500 or 1870 g i.a./ha. No statistical difference was found on weed control among the water pH. It was found that when Roundup Max® 680 SG was added to the water, water pH was lowered to 4.00-4.15, regardless if the initial water pH was 8.50, 6.50 or 4.50. Fluazifop-p-butil was applied at 210 or 160 g i.a./ha. There was a reduction in weed control with water pH 8.5 and the dose was reduced to 75% (160 g i.a./ha) of the manufacturer’s recommendation, compared to the other treatments. When the recommended dose was used there was no weed control reduction caused by the water pH used. With Bentazon there were some differences in control of Melampodium divaricatum (Rich.) DC.; with water pH of 4.50 and 8.50, and the dose reduced to 75% (840 g i.a./ha) of the recommended amount had a reduction in weed control, compared to the other treatments. However, there was no weed control reduction when the recommended dose was used. Water pH did not change weed control, with any of the herbicides, when the recommended dose was used.

Key words: Basagran 48 EC®; carrier; Fusilade 12.5 EC®; Roundup Max® 68 SG.

DOI: http://dx.doi.org/10.5377/ceiba.v47i1-2.443

Ceiba, 2006. Volumen 47(1-2):19-23