While some of us have made, and possibly already broken, our New Year’s Resolutions, Dean Sandford – technical sales manager for the North West – has an additional one for growers that it makes sense to keep!  Using plant growth regulators (PGR’s) more effectively for both economic and environmental reasons.

Here Dean explains the impact of water quality on PGR performance and recommends steps that can be taken to optimise the end result.   

Over recent years I have seen a noticeable increase in awareness of the part water quality can have on aspect of production.

Studies show water quality can have implications on the effectiveness of pesticides and herbicides.  The pH and hardness (calcium and magnesium content) of irrigation water can significantly impact on the efficacy of many products. When pesticides are added to water they begin to degrade, due to hydrolysis, and for many products this is accelerated by a high pH.

There is perhaps less awareness of the fact recent research indicates pH and alkalinity (presence of bicarbonates and carbonates) can play a role in the effectiveness of PGRs.

Some studies conclude that growth regulator solutions made with high pH water, or highly buffered, may be less effective depending on the particular PGR.  To maximise effectiveness the general recommendation is to use a water source with a pH of less than 7.0, and less than 100 ppm bicarbonates.

However, a 2015 research project concludes this recommendation may not be accurate for all PGRs. The work showed some growth regulators are moderately to strongly acidic in reaction - lowering the pH of the initial water sample. In contrast chlormequat chloride, daminozide and ethephon increased the pH of the water, while other PGRs including (paclobutrazol) are chemically neutral, ie they do not affect pH to a significant degree.

As you might expect, in general the higher the PGR rate the greater the associated increase or decrease in pH.  Just to complicate it, there appears to be one exception - chlormequat chloride, where it depends on the initial water pH and the rate.

So what should growers resolve to do?

• Use PGRs effectively for economic as well as environmental reasons.
• Consult with your PGR representative to determine the recommended final solution pH range.
• Take a representative water sample from your nursery and have it tested at a commercial laboratory to pinpoint pH and alkalinity.
• Have your water quality tested at least once a year as parameters can change due to environmental factors - such as droughts, excessive rains. This is particularly important if using bore or abstracted water.
• To check PGR applications are as effective as possible, test the pH of the spray solution with a simple hand-held pH meter.
• To simplify the process, use ICL’s pHixer specialist water conditioner.

Our specialist new water conditioner pHixer adjusts the spray tank water pH to the optimum.  Containing chemical water conditioners that dissolve carbonates in the water and reduce their ability to react, it uniquely changes colour to indicate the correct pH range.  

For samples of pHixer, and for water analysis, speak to your technical area sales manager.

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