What’s in Your Water? How Hard Water Can Affect Herbicide Performance

When we talk about getting a good spray result, most of the attention naturally goes to the chemical, the rate, the weather and the target weed.

But there is another part of the spray mix that can easily be overlooked:

The water.

And depending on where that water comes from — particularly bore water — it can have a bigger impact on herbicide performance than many people realise.

What is hard water?

Hard water contains higher levels of dissolved minerals, particularly calcium and magnesium.

That does not necessarily make the water unsafe or unusable. But when certain herbicides are added, those minerals can interact with the herbicide in the spray tank.

Glyphosate is one well-known example. Calcium and magnesium in hard water can bind with glyphosate and reduce the amount that is available to be taken up by the plant.

Think of it like a key and a keyhole

We want the herbicide to get through the leaf surface and into the plant as efficiently as possible.

Imagine the herbicide as a key and the plant as the keyhole.

With suitable water, that key is ready to do its job.

But in hard water, some herbicides can attach themselves to minerals such as calcium and magnesium. It is a bit like adding something bulky to the key — suddenly, it does not pass through the keyhole as easily.

The result?

Some of the herbicide you have paid for may not perform as effectively as it otherwise could.

How do you know if your water is hard?

You cannot reliably tell simply by looking at it.

This is particularly worth considering when spray water comes from a bore, dam or another source where mineral levels may be elevated.

For a proper assessment, a water sample can be professionally tested and discussed with your local agronomist.

At Swift Drone Solutions, if we have concerns about the water being supplied on site, we can also use a simple water-hardness test strip.

It does not replace a laboratory water analysis, but it can provide a quick indication that hardness may need further consideration before the spray mix is prepared.

What can be done about hard water?

Depending on the herbicide being used and its label requirements, a water-conditioning adjuvant may be recommended.

Products such as Choice Weather Master are specifically designed for hard-water conditions. Importantly, the manufacturer directs that it be added to the water before the pesticide is added, allowing the conditioner to deal with the hard-water minerals first.

There are a number of water-conditioning products available, so the appropriate product and rate should always be based on the chemical label and agronomic advice.

And while softer water is generally preferable where a herbicide is sensitive to hardness, there isn't one universal “zero hardness” requirement for every spray job. What matters is understanding the water you are using and whether it could interfere with the particular chemistry going into the tank.

It’s another part of getting the application right

Drone spraying is not simply about putting chemical in the aircraft and sending it across the paddock.

Water quality, weather conditions, mixing order, application rate and the product label all play a part in achieving the intended result.

Sometimes something as simple as checking the water before filling the tank can help protect the performance of the herbicide going into it.

Airborne precision. Ground-level results.