Water quality critical in farm spray application

image of sprayer
Growers and spray operators are being encouraged to test on-farm water quality this summer to ensure its effectiveness as a carrier for herbicides and pesticides and maximise chemical efficacy in the paddock. Photo GRDC.

New South Wales and Queensland grain growers and spray operators are being encouraged to test water quality before using it for the application of herbicides and pesticides.

The advice comes in the wake of a research project by the SOS Macquarie Valley group that investigated the water quality of 180 bores and assessed its suitability for use with farm chemicals.

The project found the water quality varied significantly with 78 per cent of samples more alkaline than desired and 80 per cent recording higher than ideal levels of bicarbonate concentrate, when used to apply pesticides and herbicides.

While the samples for this research project were taken from a relatively small geographic area west of the Newell Highway and north and east of the Bogan River in central western New South Wales, the issue of water quality is relevant across all farming areas of Queensland and NSW.

Grains Research and Development Corporation (GRDC) Crop Protection Officer – North Vicki Green said the quality of water used with pesticides and herbicides had a significant bearing on their effectiveness in the paddock.

“Testing your water for parameters, such as, pH, hardness, bicarbonates and salinity can identify any quality issues and allow you to make amendments to get the best outcome when you use it with farm chemicals,” she said.

“It is important you test all water sources that you are using for chemical application, including deep and shallow bores and dams.

“Understanding your water quality and knowing what you can do to make it more suitable for spraying can significantly improve your spray results, with both herbicides and pesticides.”

image of tony mcalary
SOS Macquarie Valley chairman Tony McAlary said poor water quality could reduce spray effectiveness by as much as 25 per cent, so accurate testing was critical to understand how it could impact chemical mixes. Photo Supplied.

SOS Macquarie Valley chairman Tony McAlary said his group was motivated to analyse bore water quality throughout the region to better inform growers and spray operators’ decision-making and ultimately improve spray results in the paddock.

“We felt poor water quality could be reducing our spray effectiveness by as much as 25 per cent, but we needed accurate testing to provide a better understanding of water quality and the impact it could be having on spray mixes,” he said.

“We also wanted to be able to inform growers and their advisers about what they could do to amend or adjust water quality.”

Mr McAlary said the research was also considered imperative after an SOS Macquarie Valley agronomist workshop survey revealed just 43 per cent of advisers ‘sometimes’ offered advice about water quality ahead of spraying.

“We felt this was an area worthy of research and potentially delivering information back to growers that could help them get a better result from their spray applications, by understanding the impact water quality was having on chemical efficacy when used with common farm pesticides and herbicides,” Mr McAlary said.

In partnership with the NSW Environment Protection Authority, SOS Macquarie Valley engaged Pat Hulme from Sustainable Soils Management in Warren to test 180 bore water samples for pH, hardness, bicarbonate concentrate and salinity, as part of a wider campaign to increase awareness about off-target spray drift.

The research found most of the bore water sampled was alkaline, with elevated bicarbonate concentration and moderately saline.

Mr Hulme said in the majority of samples water quality could be ‘managed or amended’ to ensure it was suitable for use with most farm chemicals. For example, ammonium sulfate (known as AMS) can assist with water hardness, whereas alkaline waters can be acidified with a range of products, such as Li-700.

Unfortunately, highly saline water was generally unsuitable for spraying, unless it was diluted with clean rain water. Dirty water or water with suspended solids could also adversely affect products such as Spray.Seed® and glyphosate so it should be filtered or settled prior to use.

“Our research showed water samples from bores in the Great Artesian Basin aquifer had consistent properties, but water chemistry from shallower bores was significantly more variable,” Mr Hulme said.

“Bore water also had the advantage over surface water of being free of sediment and organic compounds.

“It is more important to test the quality of water from each bore used than to repeatedly test water from a single bore, as bore water quality changes slowly.”

Mrs Green said accurate water testing could improve the efficacy of chemical application on-farm.

“Most water can be amended to use for spraying, but the important thing is to test to understand what you are dealing with,” she said.

Key points:

  • Poor water quality can adversely affect many products. Always consult product labels about water quality requirements.
  • Water testing should be done on a regular basis when using bore water, water from streams and rivers, reticulated (piped) water sourced from ground water, water stored in unlined dams and concrete tanks.
  • Water tests should analyse the following: pH, total hardness (including a measure of bi-carbonate levels) and total dissolved salts or salinity.
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