Title page for ETD etd-10102005-104826


Document Type Doctoral Thesis
Author De Villiers, Brian Lindsay
URN etd-10102005-104826
Document Title The influence of salts in carrier water and adjuvants on glyphosate activity
Degree PhD (Agronomy)
Department Plant Production and Soil Science
Supervisor
Advisor Name Title
Prof C F Reinhardt Committee Chair
Keywords
  • agricultural chemicals adjuvants
  • glyphosate antagonists
Date 2002-08-01
Availability unrestricted
Abstract
Glyphosate, a non-selective herbicide, is antagonized by salts in the spray carrier and responds to surfactant type and concentration. Glyphosate antagonism by dissolved salts such as calcium and magnesium was verified with natural water carriers and with carriers to which salts were added. Salt antagonism of glyphosate occurred from the formation of complexes that were less absorptive than the formulated isopropylamine glyphosate. Absorption of various salts of glyphosate varied as follows: isopropylamine > acid > ammonium > sodium > calcium. Ammonium sulphate increased the absorption of glyphosate both in distilled water carriers and in water carriers containing calcium chloride. Absorption and retention of glyphosate generally increased as surfactant (nonylphenol ethoxylate) hydrophilic/lipophilic balance (HLB) increased. The optimal HLB for glyphosate absorption was lower when ammonium sulphate was added to the spray carrier. An experimental adjuvant (trade name: Power-Up) that contained nonionic surfactant and ammonium sulphate, increased glyphosate efficacy more than the currently registered South African adjuvants. This could be as a result of increased foliar absorption and/or retention on foliage. The use of acid containing adjuvants was not essential for adequate glyphosate efficacy. Visual assessment of spray droplet residuals on leaves indicated that the appearance of spray droplet residuals was linked to glyphosate efficacy. Thick, amorphous and grainy spray droplet residuals on the leaf surface was an indicator of poor efficacy, whilst thinner, smoother residuals in close contact with the leaf surface was linked to increased efficacy.

2002 University of Pretoria. All rights reserved. The copyright in this work vests in the University of Pretoria. No part of this work may be reproduced or transmitted in any form or by any means, without the prior written permission of the University of Pretoria.

Please cite as follows:

De Villiers, BL 2002, The influence of salts in carrier water and adjuvants on glyphosate activity, PhD thesis, University of Pretoria, Pretoria, viewed yymmdd < http://upetd.up.ac.za/thesis/available/etd-10102005-104826/ >

H1148/ag

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