Archive Article: 2001/03/30

30 March 2001

"KNOW your water quality, it can affect the spray mix in your tank and the effectiveness of products," says Ken Davis of the Scottish Agricultural College in Edinburgh.

Acidity or alkalinity of water can affect some products, especially when it gets outside the normally acceptable range of pH5.8-7.8. Most supplies of potable water fall within this range, but the actual levels of your supply can be checked by calling the water company.

Water from boreholes or other supplies may be more variable and it is useful to have it tested, especially in chalky or high organic areas. High pH alkaline water may reduce the efficacy of some insecticides, for example, especially if the spraymix is in the tank for a long time.

Other problems can be caused by the calcium and magnesium ions in hard water. Those can tie up cations and reduce the efficacy of some sulfonyl urea herbicides and glyphosate, says Mr Davis.

Excess frothing

On the other hand very soft water can cause excess frothing, which can in turn cause spillage and environmental contamination and an increased risk of drift with conventional nozzles, says Clare Butler Ellis of the Silsoe Research Institute.

Tank mixing may build up the level of surfactants and increase a problem which approved anti-foam agents can help overcome. "But in the absence of foaming, water softness does not appear to affect spray quality with air induction nozzles," she adds.

Cold water can also cause problems. Early in the season water in outside storage tanks may be very cold and water dispersible granules, soluble packs and others non-liquid formulations may take a long time to disperse efficiently.

Read the labels carefully, watching for phrases like "do not mix with alkaline products" or "under low pH conditions effectiveness may be reduced". &#42

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