Does Water Quality Affect Herbicides?

A simple question and a resounding yes.  For instance, most of you know that some herbicides, glyphosate being one of them, lose activity in the soil but that also applies to soil particles in the water.  So if you are dragging water from a pond, even if you are filtering you need to be careful that the filters are good enough to take out any fine soil particles.  Apart from that you run the risk of clogging your nozzles.

The other big factor is water hardness.  This is often overlooked but can impact upon herbicide performance.  Hard water cations, especially calcium and magnesium, but also sodium, iron, potassium, zinc and aluminium, can cause major problems if not managed properly.

Herbicides that are weak acids like glyphosate, GA200 (glufosinate ammonium) and 2,4-D 720 Amine are the most susceptible but hard water can impact on most herbicides including the sulfonylurea herbicides like MSF600 and Ranger, but also on Dicamba 500 SL. 

Some of you and many contractors will use ammonium sulphate in your spray mix but this really only counters the effect of the calcium cations and doesn’t address the impact of magnesium, iron and aluminium cations.

Luckily in most parts of New Zealand we generally have soft water but there are some parts of the country with hard water.  Normally you will know as you will get white calcium build up or scale on pipes and it is more difficult to lather with soap.

If you are in a hard water area then using a water conditioner and dealing with hard water you will find that herbicides blend and mix better and generally apply better and more evenly, giving more uniform coverage, improved adhesion and improved drift control from the ability to better manage droplet size.

Below is a guideline as to the ranges for hard and soft water and most councils will have available water testing results so you can easily check if you have hard or soft water. 

If you have hard water, we recommend you either use a water conditioner or install a water conditioning filter.