Managing Hard Water Maximum Herbicide Performance

Posted April 08, 2019 

Water quality is an important factor in early season herbicide applications. Hard water can significantly reduce herbicide effectiveness, but is easy to manage with a high-performance water conditioner like CHOICE WEATHER MASTER from Loveland Products.

What is hard water?

Water hardness is a measure of the total concentration of hard water ions. These include: iron, zinc, magnesium, calcium, sodium and potassium. Calcium (Ca2+) and magnesium (Mg2+) are the biggest influencers of antagonism because they tend to be found in greater concentrations. 

Hard water cations

How does hard water affect early-season herbicide applications? 

Hard water cations react with certain pesticides, especially herbicides, reducing overall pesticide efficacy. The greater the concentration of these minerals, the harder the water. As in magnets, opposite charges attract: negatively charged pesticide molecules attach to the positively charged iron, calcium and magnesium cations in hard water. The binding of pesticides with these cations creates molecules that:

  • Cannot enter the target pest
  • Enter at a much slower rate
  • Precipitate out of the solution

The more the pesticide is bound to minerals, the more “diluted” the product becomes in the tank. In some cases, the chemically altered molecule may be unable to dissolve in water, penetrate the leaf tissue, attach to the site of activity in the pest to disrupt biological functions or perform as a pesticide. These effects are not limited to the spray tank environment but extend to the spray solution on the leaf surface, which can affect product uptake. 

Which chemistries are most affected by hard water?

Products most affected (but not limited to) are weak-acid herbicides such as glyphosate, glufosinate ammonium and 2,4-D.

Weak acid herbicides are particularly susceptible to hard water

Who has hard water?

Here is a hard water map of Canada:

What can I do to manage hard water?

Using a water conditioner, such as CHOICE WEATHER MASTER, combats all the hard water cations that negatively affect weak acid herbicides. CHOICE WEATHER MASTER has two modes of action in a convenient liquid formulation to combat all hard water cations.

Does CHOICE WEATHER MASTER improve glyphosate performance?

Yes – see below for performance on common weeds.

Doesn’t AMS manage hard water for me?

AMS will manage calcium hard water cations only, while CHOICE WEATHER MASTER will manage multiple hard water cations. See how CHOICE WEATHER MASTER compares to AMS:

How do I know if I have hard water?

Talk to your local Nutrien Ag Solutions retail about testing your water. They have instant-read hard water test strips and can also help have your water tested through a certified lab.

What rates of CHOICE WEATHER MASTER do I need?

CHOICE WEATHER MASTER can be used at 0.25% v/v to 0.5% v/v. See a rate chart below:

Does CHOICE WEATHER MASTER manage water pH?

No. Solution pH and managing hard water are two different issues. Learn more about how water pH affects pesticide sprays here.


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