Effect of Hard Water and Ammonium Sulfate on Weak Acid Herbicide Activity

Glyphosate is a weak acid herbicide and can bind with calcium in the spray carrier. Diammonium sulfate is commonly used as an adjuvant with glyphosate to enhance phytotoxicity and overcome antagonistic effect of these cations. Most postemergence herbicides are also weak acid herbicides. Data is limited for other weak acid herbicides and the effect of diammonium sulfate in enhancing herbicide activity and overcoming antagonism. Field studies were conducted with aminopyralid, tembotrione, dicamba plus diflufenzopyr, and glufosinate to determine if (1) these weak acid herbicides are enhanced by ammonium, (2) if they are antagonized by calcium and magnesium in the spray solution, (3) if diammonium sulfate overcomes salt antagonism, and (4) if a previously published equation for the amount of ammonium sulfate required to overcome salt antagonism of glyphosate based on cation concentration in spray water correctly predicts to other weak acid herbicides. The activity of the four weak acid herbicides increased with the addition of ammonium to the spray solution, all were antagonized by calcium and magnesium, and diammonium sulfate overcame the antagonism. The previously published equation to calculate the amount the diammonium sulfate needed to overcome 500 and 1000 ppm hardness was accurate and can be used for these herbicides and possibly other weak acid herbicides.

[1]  J. D. Nalewaja,et al.  Spray Volume, Formulation, Ammonium Sulfate, and Nozzle Effects on Glyphosate Efficacy1 , 2003, Weed Technology.

[2]  D. Pratt,et al.  Substitutes for Ammonium Sulfate as Additives with Glyphosate and Glufosinate1 , 2003, Weed Technology.

[3]  J. D. Nalewaja,et al.  Quinclorac Efficacy as Affected by Adjuvants and Spray Carrier Water1 , 2003, Weed Technology.

[4]  S. E. Hart,et al.  Effect of ammonium sulfate on the efficacy, absorption, and translocation of glufosinate , 2000, Weed Science.

[5]  K. Thelen,et al.  The Basis for the Hard-Water Antagonism of Glyphosate Activity , 1995, Weed Science.

[6]  J. D. Nalewaja,et al.  Sethoxydim Response to Spray Carrier Chemical Properties and Environment , 1994, Weed Technology.

[7]  J. D. Nalewaja,et al.  Optimizing Adjuvants to Overcome Glyphosate Antagonistic Salts , 1993, Weed Technology.

[8]  J. D. Nalewaja,et al.  Spray Carrier Salts Affect Herbicide Toxicity to Kochia (Kochia scoparia) , 1993, Weed Technology.

[9]  J. D. Nalewaja,et al.  Influence of diammonium sulfate and other salts on glyphosate phytotoxicity , 1993 .

[10]  J. D. Nalewaja,et al.  Sodium Bicarbonate Antagonism of 2,4-D Amine , 1990, Weed Technology.

[11]  J. A. Ivany.  CONTROL OF QUACKGRASS WITH GLYPHOSATE AND ADDITIVES , 1988 .

[12]  P. Shea,et al.  Reversal of Cation-Induced Reduction in Glyphosate Activity by EDTA , 1984, Weed Science.

[13]  O. Burnside,et al.  Effect of Water Quality, Carrier Volume, and Acid on Glyphosate Phytotoxicity , 1983, Weed Science.

[14]  J. O'donovan,et al.  INFLUENCE OF NON-IONIC SURFACTANTS, AMMONIUM SULPHATE, WATER QUALITY AND SPRAY VOLUME ON THE PHYTOTOXICITY OF GLYPHOSATE , 1981 .

[15]  W. Phillips,et al.  Effects of Water Quality and Spray Volume on Glyphosate Phytotoxicity , 1979, Weed Science.