Abstract
ABSTRACT: Water hardness antagonism and the effect of ammonium sulphate (AMS) on efficacy of glyphosate have been well documented. However conflicting results between weed species were noted by the authors. Greenhouse experiments were conducted twice at the Ferdowsi University of Mashhad in a randomized complete block design with a factorial arrangement and three replications during 2014-2015. Four experiments were arranged separately on cypress (Kochia scoparia), redroot pigweed (Amaranthus retroflexus), little seed canary grass (Phalaris minor) and winter wild oat (Avena ludoviciana) using ammonium sulphate and deionizad water and in the presence of different salts, (i.e. NaHCO3, CaCO3, MgCl2 and CaCl2 at 500 ppm) against three doses of glyphosate (256.25, 512.5 and 1,025 g a.i. ha-1), with and without ammonium sulphate (AMS) as adjuvant (2% w/v). The results showed the application of AMS overcomes the inhibitory effects of salts in the spray solution in tested species. The degree of effectiveness in A. retroflexus was more than A. ludoviciana and P. minor. Glyphosate with AMS caused reduction in dry matter in grasses from 0.34 to 0.28 g, while glyphosate toxicity in A. retroflexus with AMS was 100 percent and all of the plants were destroyed (0.82 to 0 g). The application of AMS in overcoming the inhibitory effects of water hardness had no effect on K. scoparia control. However, Increasing AMS could overcome the inhibitory effects of hard water in the spray solution on glyphosate efficacy in A. retroflexus and K. scoparia, but it had no effect on tested grassy weeds. We may conclude that glyphosate work differently on weed species using AMS and hard water.
Highlights
Water is a universal solvent and it is used as a primary carrier for crop protection product applications
By considering contrasting results and variation of glyphosate efficacy in hard water among different species through ammonium sulphate (AMS), the objective of this research was to evaluate the influence of different salts and ammonium sulfate on K. scoparia L., A. retroflexus L., P. minor Retz., and
ANOVA showed that both degree of survival and dry weight of the weed species were significantly (p≤0.01) affected by the main effect of glyphosate and ammonium sulfate
Summary
Water is a universal solvent and it is used as a primary carrier for crop protection product applications. It has been well documented that glyphosate efficacy is reduced when applied in water containing high level cations (Nalewaja and Matysiak 1991; Chahal et al, 2012; Devkota, 2016). Nalewaja and Matysiak (1991) reported that sodium and magnesium salts were less antagonistic than calcium, zinc and iron salts. Calcium and magnesium sulphates were less antagonistic than chlorides, but sulphates and chlorides of sodium were antagonistic to glyphosate toxicity on wheat (Nalewaja and Matysiak, 1991). Numerous studies have shown that cations or foliar fertilizers can influence glyphosate efficacy, depending on the weed species (Baily et al, 2002; Mueller et al, 2006)
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