The Effect of Cations and Ammonium Sulfate on the Efficacy of Dicamba and 2,4-D

Abstract

Dicamba or 2,4-D will be used POST for the control of weeds in soybean when dicamba- or 2,4-D-resistant soybean are commercialized. The active ingredients of both herbicides are weak acids in solution and may bind to cations present from hard water used as herbicide carrier or from foliar fertilizers added to spray solutions. The objectives of this research were (1) to determine if the efficacy of dicamba or 2,4-D are influenced by divalent cations, namely calcium (Ca), magnesium (Mg), manganese (Mn), and zinc (Zn), in the spray solution, and (2) to determine if adding ammonium sulfate (AMS) to the spray solution can overcome antagonism. The factorial study included five cation solutions (deionized water [dH2O], Ca at 590 mg L−1, Mg at 630 mg L−1, Mn at 4.97 L ha−1, and Zn at 2.33 L ha−1), two herbicide treatments (dicamba or 2,4-D), and two water conditioner treatments (without or with AMS at 20.37 g L−1). Treatments were applied to common lambsquarters, horseweed, and redroot pigweed. Control of horseweed and redroot pigweed increased when AMS was added to the 2,4-D treatments, irrespective of cation solution. Control of common lambsquarters was increased when AMS was added to 2,4-D for only the Ca and Mn cation solution. In contrast to the results obtained with 2,4-D, control of horseweed with dicamba was not influenced by cation solution. Tank-mixing AMS with dicamba increased control of both redroot pigweed and common lambsquarters in the dH2O, Mg, and Mn solutions.

Divalent Cations in Spray Water Influence 2,4-D Efficacy on Dandelion (Taraxacum officinale) and Broadleaf Plantain (Plantago major)

“…Experiments were conducted with 2,4-D dimethylamine to evaluate the effect of cation and fertilizer solutions on the performance of the herbicide following the methodology similar to Roskamp et al (2013) Treatments were applied to broadleaf plantain when rosettes were 6 to 10 cm in diameter and to dandelions when rosettes were 9 to 14 cm in diameter. Plant size varied within experimental run but not within block.…”

“…Later, Naleweja et al (1991) determined that kochia injury from 2,4-D diethanolamine was reduced when applied in water containing either Ca, Mg, sodium (Na), potassium (K), or Fe salts and that antagonism could be overcome by adding AMS. More recently, Roskamp et al (2013) reported that Ca and Mn antagonized 2,4-D dimethylamine control of the annual weed common lambsquarters (Chenopodium album L.). When antagonism of 2,4-D dimethylamine occurred from Ca or Mn, AMS reduced antagonism and increased common lambsquarters control (Roskamp et al 2013).…”

“…Although AMS is commonly used to condition hard water for glyphosate applications (Whitford et al 2014), it is not commonly used with 2,4-D amine applications despite previously published reports showing that 2,4-D efficacy on annual broadleaf weeds could be enhanced when using AMS as an adjuvant (Nalewaja et al 1990Roskamp et al 2013). Additionally, the use of AMS as an adjuvant is not currently recommended on any weak-acid herbicide labels used in the turf and ornamental/landscape industry other than glyphosate and sethoxydim.…”

Glyphosate Efficacy of Different Salt Formulations and Adjuvant Additives on Various Weeds

“…Variability of herbicides aims at a greater diversity and efficacy in herbicide use. In addition, herbicide efficacy can be significantly influenced by environmental conditions, adjuvants and spray carrier water quality [3][4][5][6][7][8]. In particular, glyphosate efficacy is influenced by air temperature and light intensity [9,10].…”

“…Agronomy 2017, 7,60 Author Contributions: Ilias Travlos, Nikolina Cheimona and Dimitrios Bilalis contributed equally, reviewed the literature and wrote the paper.…”