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Effects of Water Quality and Spray Volume on Glyphosate Phytotoxicity

Published online by Cambridge University Press:  12 June 2017

P. W. Stahlman
Affiliation:
Fort Hays Branch, Kansas Agric. Exp. Stn., Hays, KS 67601
W. M. Phillips
Affiliation:
Fort Hays Branch, Kansas Agric. Exp. Stn., Hays, KS 67601

Abstract

Several inorganic salts added to the spray solution reduced the herbicidal activity of glyphosate [N-(phosphonomethyl)glycine]. Of the salts tested, iron and aluminum reduced herbicidal activity most. Reductions by calcium and zinc were moderately severe; by magnesium, moderate; by potassium and sodium, none. The reduction in phytotoxicity seems to be caused by cations, but factors other than valence also may be involved.

Reduction in phytotoxicity was related to salt concentration and spray volume. Glyphosate at 0.84 kg/ha in 93 to 374 L/ha distilled water killed test plants. Tap water was an equally effective carrier at 93 and 187 L/ha volumes, but was significantly less effective at the 374 L/ha volume. Activity decreased as the molar concentration of CaCl2 increased to 0.01. Herbicidal activity was eliminated at 0.01 M and 374 L/ha; however, concentrations of CaCl2 exceeding 0.04 M reversed the trend and reacted similarly to a 0.005 M solution, which approximates the minimum hardness of most ground waters in Kansas.

Type
Research Article
Copyright
Copyright © 1979 by the Weed Science Society of America 

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References

Literature Cited

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