WestVic Dairy News - May 2010 Edition
Check your water quality when using farm chemicals
By Helen Chenoweth, DPI Warrnambool
When it comes to using farm chemicals, the quality of your water supply is very important.
At the recent Heywood Discussion Group night, run in conjunction with the local Murray Goulburn Store, over 50 farmers were challenged to make sure they know the quality of the water they are mixing with chemicals to control weeds and pests in pastures. Nufarm’s south west Victoria Sales Manager Phil Jobling advised all farmers to test their water supply on a regular basis for such things as pH and iron levels as these can significantly reduce the effectiveness of chemicals used.
Local farmers Ivan Nunn, Ted Taylor, David Foster and Gerard Lloyd discuss their herbicide spray options with Nufarm's Phil Jobling.
When you mix and apply agricultural chemicals you should use the cleanest water available.
Poor quality water can reduce the effectiveness of some agricultural chemicals. It can also damage spray equipment by blocking lines and nozzles and increase wear and tear on your machinery.
The following information from the NSW Spray Sense note 12 details how the characteristics of water quality affect chemical performance, how to test water quality and, if necessary, how to improve water quality.
Effects of water quality
Water quality depends on the source of the water (dam, river, bore and aquifer) and the season (for example, has there been heavy rain or drought?).
Several characteristics of water quality affect chemical performance.
Dirt: Dirty water has very small soil particles (clay and silt) floating in it. The particles are so small that they do not sink to the bottom but remain suspended. They can adsorb and bind the chemical’s active ingredient and reduce its effectiveness (this applies especially to glyphosate and paraquat). Dirt can also block nozzles, lines and filters, reduce the sprayer’s overall performance and increase wear and tear on your machinery.
Water hardness: Water is termed hard when it has a high percentage of calcium and magnesium. Hard water can cause some chemicals to precipitate. Chemicals that tend to do this often have agents added to overcome this problem.
Hard water can also affect the balance of the surfactant system and affect properties such as wetting, emulsification and dispersion. Very hard water can also reduce the efficiency of agents used to clear dirty water.
pH: is a measure of acidity and alkalinity scaled on a range between 1 and 14. A pH of 7 is neutral; less than 7 is acid and more than 7 alkaline. Most natural waters have a pH between 6.5 and 8. In highly alkaline water (pH>8) many chemicals undergo a process called alkaline hydrolysis. This process causes the breakdown of the active ingredient into other compounds which can reduce the effectiveness of the chemical over time. This is one reason why spray mixes should not be left in spray tanks overnight. Very acid water can also affect the stability and physical properties of some chemical formulations.
Dissolved salts: The total amount of mineral salts dissolved in water is usually measured by the electrical conductivity (EC) of the water. The EC of bores and dams depends largely on the salt levels in the rock and soil that surrounds them. During a drought the salinity of water increases. Very salty water can cause blockages in equipment. It resists any change in pH.
Organic matter: Water containing a lot of organic matter (such as leaves or algae) can block nozzles, lines and filters. Algae can also react with some chemicals, reducing their effectiveness.
Temperature: Very hot or cold water can affect the performance of some chemicals.
Improving water quality
You need to test your water to see whether it will affect chemical performance. The company undertaking the test will be able to recommend improvements you can make. There are commercial products available to reduce pH, soften hard water and clear dirty water. To reduce the effects of very salty water you may need to mix it with better quality water from other sources.
Testing water quality
You need to test your water to see whether it will affect the performance of chemicals.
Home testing
You can test for pH or EC (salt) yourself with kits or meters purchased from produce, hardware or pool stores. These tools need to be regularly calibrated to give accurate results.
Sending samples away
You can also send your water away for testing. Your local chemical reseller should be able to advise you where to send the sample and both the turn around time and cost. The company undertaking the test will be able to recommend improvements you can make.
To send your water away for testing, follow these simple steps:
– Use a clean container (500 mL minimum).
– Rinse the bottle four times with the sample water, remembering to empty the rinse water away from the sample site.
– Follow sampling guidelines (see Table 1).
– Fill the bottle to the top, leaving little or no airspace and seal tightly.
– Label the container and indicate what the water will be used for (for example: domestic or stock consumption, irrigation or spraying) as this will affect interpretation of results
Table 1. Sampling guidelines
|
Water source |
Action |
|---|---|
|
New bore |
Sample after pumping for several hours. |
|
Operating bore |
Sample after pumping for 30 minutes; collect as close as possible to the head of the bore. |
|
Stream |
Sample main stream flow. |
|
Dam or Lake |
Sample away from edge and near the suction inlet to the pump. Dam water often settles into well-defined layers – so either sample layers separately or stir up the water. Filter the water to get rid of any organic matter. |
For more information
Always thoroughly read the product label before using any agricultural or veterinary chemical and refer to the product label for information on the quality of water to use when mixing. If there is no information contact your chemical reseller or the manufacturer of the chemical for advice.
The advice provided in this document is intended as a source of information only. The State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence, which may arise from you relying on any information in this publication.
