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This article in AJ

  1. Vol. 79 No. 1, p. 48-52
    Received: June 3, 1985

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Herbicide Compatibility and Phytotoxicity When Mixed with Liquid Fertilizers1

  1. Kip W. Sander,
  2. Orvin C. Burnside and
  3. John I. Bucy2



The need for growers to conserve energy, labor, and money has stimulated the joint application of herbicides and liquid fertilizers. Chemical and physical reactions between herbicides and liquid fertilizers may affect the compatibility or herbicidal performance of a combination. The objective of this research was to determine the compatibility and phytotoxic characteristics of 10 common herbicides when individually mixed with each of six liquid fertilizers. Of the 60 herbicide-liquid fertilizer combinations tested, 87% were compatible and 13% were incompatible. Attapulgite clay suspensions were the most compatible of the liquid fertilizers tested. Atrazine (6-chloro-N-ethyl-N'-(1-methylethyl)-1,3,5-triazine-2,4-diamine] and metribuzin [4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one] were least compatible with the liquid fertilizers. Phytotoxicity of the herbicide, when combined with the liquid fertilizers, increased in 21%, decreased in 32%, and was equal to the herbicide-water check in 47% of the combinations. Glyphosate [N-(phosphonomethyl)glycine] and paraquat (1,1'-dimethyl-4,4'-bipyridinium ion) showed the highest occurrence of decreased phytotoxicity, whereas acifluorfen {5-[2-chloro-4-(trifluoromethyl)phenoxyl-2-nitrobenzoic acid} and bentazon [3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one 2,2-dioxide] showed the highest occurrence of increased phytotoxicity when mixed with liquid fertilizers. Agitation was necessary to prevent separation in 52% of the compatible mixtures. Duration of contact between herbicide and liquid fertilizer did affect herbicidal phytotoxicity with certain combinations and especially with butylate [S-ethyl bis(2-methylpropyl) carbamothioate]-liquid fertilizer mixtures.

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