Hard water antagonism of 2,4-D dimethylamine (DMA) is avoided with the inclusion of ammonium sulfate (AMS) as a water conditioning agent in mixtures. In addition to functioning as an adjuvant, AMS is also a nitrogen (N) fertilizer. Two experiments evaluated the efficacy of 2,4-D DMA when mixed with alternative N sources and rates. The first experiment sought to determine the influence of alternative N sources and N rates on 2,4-D DMA efficacy in comparison to AMS. The second experiment more closely evaluated the influence of AMS rate on 2,4-D DMA efficacy. Nitrogen sources included AMS, ammonium nitrate (AMN), potassium nitrate (KNO₃), urea–ammonium–nitrate (UAN), and urea. Each N source was tank-mixed with 2,4-D at both an adjuvant rate (20 g L⁻¹ or 25 ml L⁻¹) and a fertilizer rate (24.4 kg N ha⁻¹) in both soft (0 mg CaCO₃ L⁻¹) and hard (600 mg CaCO₃ L⁻¹) water. Efficacy of the mixtures was assessed on dandelion (Taraxacum officinale F.H. Wigg.) in the greenhouse. Without consideration to water hardness level or N rate, 2,4-D DMA efficacy with the N sources was: AMN = UAN > AMS = Urea > KNO₃. Ammonium sulfate reversed hard water antagonism of 2,4-D DMA at the adjuvant rate, but not at the fertilizer rate. When applied at the adjuvant rate in hard water, dandelion control rankings from 2,4-D mixes were generally: AMN = UAN = AMS > Urea > KNO₃. It is not advised to mix KNO₃ with 2,4-D applications based on reduced efficacy. The second experiment determined that 2,4-D efficacy decreased as AMS rate increased above the commonly used adjuvant rate (2% w/w, 20 g L⁻¹), likely from salting out. Applicators desiring to use AMS as a foliar fertilizer should apply AMS separate from 2,4-D DMA to prevent potential antagonism.

通过在混合物中加入硫酸铵 (AMS) 作为水调节剂，避免了 2,4-D 二甲胺 (DMA) 的硬水拮抗作用。除了用作佐剂外，AMS 还是一种氮 (N) 肥料。两个实验评估了 2,4-D DMA 在与替代氮源和比率混合时的功效。第一个实验旨在确定与 AMS 相比，替代氮源和氮率对 2,4-D DMA 功效的影响。第二个实验更密切地评估了 AMS 速率对 2,4-D DMA 功效的影响。氮源包括 AMS、硝酸铵 (AMN)、硝酸钾 (KNO ₃ )、尿素-硝酸铵 (UAN) 和尿素。每个 N 源都与 2,4-D 以两种佐剂比率（20 g L ^-1或 25 ml L ^-1) 和施肥量 (24.4 kg N ha ^-1 ) 在软水 (0 mg CaCO ₃ L ^-1 ) 和硬水 (600 mg CaCO ₃ L ^-1 ) 中。在温室中对蒲公英（Taraxacum officinale FH Wigg.）评估混合物的功效。不考虑水硬度水平或 N 率，N 源的 2,4-D DMA 功效为：AMN = UAN > AMS = 尿素 > KNO ₃。硫酸铵在助剂用量下逆转了 2,4-D DMA 的硬水拮抗作用，但在肥料用量下则不然。当在硬水中以佐剂比例施用时，来自 2,4-D 混合物的蒲公英控制等级通常为：AMN = UAN = AMS > 尿素 > KNO ₃。不建议混合 KNO ₃与基于降低的功效的 2,4-D 应用。第二个实验确定，2,4-D 功效随着 AMS 率增加到高于常用佐剂率（2% w/w，20 g L ^-1）而降低，可能是由于盐析。希望使用 AMS 作为叶面肥的施药者应将 AMS 与 2,4-D DMA 分开使用，以防止潜在的拮抗作用。