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1 March 2013 The Effect of Cations and Ammonium Sulfate on the Efficacy of Dicamba and 2,4-D
Jared M. Roskamp, Gurinderbir S. Chahal, William G. Johnson
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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.

Nomenclature: 2,4-D; dicamba; common lambsquarters, Chenopodium album L. CHEAL; horseweed, Conyza canadensis (L.) Cronq. ERICA; redroot pigweed, Amaranthus retroflexus L. AMARE.

Dicamba o 2,4-D serán usados POST para el control de malezas en soya cuando se comercialice la soya resistente a dicamba o 2,4-D. Los ingredientes activos de ambos herbicidas son ácidos débiles en solución los cuales pueden adherirse a cationes provenientes de aguas pesadas usadas como medio de acarreo del herbicida o de fertilizantes foliares agregados a las soluciones de aplicación. Los objetivos de esta investigación fueron (1) determinar si la eficacia de dicamba o 2,4-D es influenciada por cationes divalentes, específicamente calcium (Ca), magnesium (Mg), manganese (Mn), y zinc (Zn), en la solución de aplicación, y (2) determinar si agregar ammonium sulfate (AMS) a la solución de aplicación puede eliminar los antagonismos. El estudio factorial incluyó cinco soluciones de cationes (agua desionizada [dH2O], Ca a 590 mg L−1, Mg a 630 mg L−1, Mn a 4.97 L ha−1, y Zn a 2.33 L ha−1), dos tratamientos de herbicidas (dicamba o 2,4-D), y dos tratamientos de acondicionamiento de aguas (sin o con AMS a 20.37 g L−1). Los tratamientos fueron aplicados a Chenopodium album, Conyza canadensis y Amaranthus retroflexus. El control de C. canadensis y de A. retroflexus incrementó cuando AMS fue agregado a los tratamientos de 2,4-D sin importar la solución de cationes. El control de C. album se incrementó cuando AMS fue agregado a 2,4-D pero solamente para las soluciones de los cationes Ca y Mn. En contraste con los resultados obtenidos con 2,4-D, el control de C. canadensis con dicamba no se vio influenciado por la solución de cationes. El mezclar en tanque AMS con dicamba incrementó el control de A. retroflexus y

Jared M. Roskamp, Gurinderbir S. Chahal, and William G. Johnson "The Effect of Cations and Ammonium Sulfate on the Efficacy of Dicamba and 2,4-D," Weed Technology 27(1), 72-77, (1 March 2013).
Received: 19 July 2012; Accepted: 22 October 2012; Published: 1 March 2013

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