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Water Conditioning through an Injection Sprayer (07/02/15)

Question: A grower has an injection sprayer and has treated the spray solution with a water conditioner. Since I am injecting glyphosate into the water stream and then is ejected out the nozzle a second later, is the water conditioner adjuvant actually doing anything?

Water Conditioning through an Injection Sprayer

Question: A grower has an injection sprayer and has treated the spray solution with a water conditioner.  Since I am injecting glyphosate into the water stream and then is ejected out the nozzle a second later, is the water conditioner adjuvant actually doing anything?

Answer: The answer below is based on the assumption that all droplets will contain a minimum concentration of an effective water conditioner.

  1. The term “water conditioner” is broad. If this person is using any adjuvant containing ammonium sulfate (AMS) at the equivalent rate of 4 to 8.5 lb/100 gal water (dry AMS formulation) or 2.5% v/v (liquid AMS formulation) depending on water hardness then the reaction explained below will occur. Many liquid water conditioners do not contain AMS and are used at low use rates (0.5% v/v) and may not neutralize antagonistic minerals or optimize herbicides.
  2. Two reactions occur with AMS. First, is the reaction of the ammonium (from AMS) binding with glyphosate to form ammonium-glyphosate and second, the sulfate (from AMS) will bind with cationic minerals in the spray water forming Ca-sulfate, Mg-sulfate, Na-sulfate, etc. These two reactions occur in the spray droplet on the leaf. It can occur in the spray tank but Dr John Nalewaja and other weed scientists at NDSU has shown that binding effectively occurs in the spray droplets as water evaporates and is regulated by solubility. For example, as water in the spray droplet dries, sulfate will bind with Ca and precipitate out first because it is the least soluble. With the antagonistic mineral neutralized then the ammonium can bind with the weak acid herbicide (glyphosate) and will remain in solution because it is highly soluble. This ammonium-glyphosate molecule can pass through the cuticle with the aid of surfactant resulting in greater absorption and greater herbicide efficacy. Even in water with either no or low cationic salts the ammonium-herbicide binding will occur resulting in increased weed control.
  3. As stated earlier these two reactions will only occur in droplets containing AMS and glyphosate. I do not know the efficiency of getting glyphosate molecules into every droplet from an injection type sprayer system. If the grower used AMS as a water conditioner and the spray water was previously conditioned with AMS then AMS will remove/nullify the antagonistic salts from the water regardless if glyphosate is in the droplet or not.

Rich Zollinger

Extension Weed Specialist

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