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6 March 2018
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Crop Protection
Crop Production

How's your water quality?

Fruitfed Supplies Senior Technical Advisor Tayah Ryan considers water quality and its impact on horticultural practices.

It’s not often we give much thought to the water we put in our spray tanks, but water quality can have a significant influence on the stability of chemicals within the spray tank.

Poor water quality can result in the breakdown of active ingredients within the tank and can negatively impact on their effectiveness on the target pest or disease. While there are a multitude of factors that impact on water quality, the two main aspects we will focus on in this article are pH and water hardness. Water hardness is a measure of the amount of positively charged ions present.

Calcium (Ca2+) is the most common, but magnesium, iron and manganese can also have the same impact.

Some agrichemical products hold a strong negative charge. Negatively charged products (e.g. glyphosate) attract positively charged particles (e.g. Ca2+) within water. Hard water containing many positively charged particles can therefore result in the product becoming ‘locked up’ and consequently unavailable for absorption into the plant. Sticking with glyphosate as our example, a water hardness reading of 300 pm can lock up to 30% of the glyphosate active. pH in its simplest form is a measure of how acidic or alkaline a solution is. Generally, when we talk about water for spraying, a pH above 8 might be considered ‘high’, although this can vary somewhat depending on the product (consult individual product labels for more detail).

Generally, the more sensitive a product is to pH, the faster it will hydrolyse, i.e. break down, in the spray tank if outside of this optimum. Insecticides tend to be particularly sensitive, and usually prefer a slightly acid pH. In comparison, copper fungicides should never be acidified, as this can result in excessive release of copper ions into the spray solution and can cause spray damage on fruit and/or leaves. General comments regarding water quality

  • A water test is generally the most accurate way to determine water quality. Your local Fruitfed Supplies store can assist with this.
  • Always check the product label for information regarding water quality and the chemical you are spraying.
  • Always try to spray out your tank in one day, and don’t leave sitting overnight. This is particularly important where your pH may not be in the optimum range for the product used.
  • There are products available to adjust both the pH and the hardness of your spray water (e.g. X-Change) if this is what’s required.

For more information on water quality and how to test, talk to your local Fruitfed Supplies store for advice. Find them here

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