Farmers in some areas, especially in southeastern Saskatchewan and southwestern Manitoba, may have to look farther afield this season for clean, clear water to fill sprayer tanks.
However, with the dry, cool weather so far this year, some farmers might get away without having to spray at all.
In Manitoba, near Melita, ground zero for drought this year, weed growth has been virtually non-existent, said Scott Chalmers, a diversification technician with Manitoba Agriculture.
“Most guys aren’t even doing a burnoff because it’s so dry and nothing is growing anyway,” he said. He added that “not a single thing” at the Westman Ag Diversification Organization test plots is growing so far this spring.
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However, farmers lucky enough to have moisture or those faced with hardy weeds poking up despite the drought, should use caution before putting water in their sprayer tanks.
It’s best to test the water first because some herbicides, most notably glyphosate, may be adversely affected by the presence of minerals or suspended solids and cloudiness. Other herbicides such as Gramoxone (paraquat/diquat) and the dessicant Reglone, may also be affected by cloudy water.
Iron is one culprit. It is easily spotted because it fouls household hot water tanks and taps. Dugouts carved into saline aquifers and water from underground sources in Alberta, Saskatchewan and parts of Manitoba may also affect herbicide effectiveness because they can contain calcium, magnesium, sodium, sulfate, chloride and bicarbonate.
Bedrock aquifers generally have soft water, while glacial till sediments tend to be on the hard side.
It might be worth trucking in municipal water, but if it comes from a well and not a surface reservoir, it may not be suitable for use with glyphosate.
“If you have water that’s hard enough, you could have pretty close to a total failure with glyphosate,” according to Rick Holm, a professor of plant sciences at the University of Saskatchewan.
“With the bicarbonates and the grass herbicides, usually it’s a reduction in activity, not a total failure.”
He added that using bad water is one of three key spraying mistakes farmers can make, along with reducing application rates and spraying too late in the season.
Municipal water in some areas might not be good enough, but it may have been tested already and analysis sheets could be available.
When studying test results, total dissolved solids in the water are the primary consideration, Holm said.
Testing for total dissolved solids is generally measured in terms of electrical conductivity or EC.
Mountain-fed river water, such as the South and North Saskatchewan rivers, are the standards for quality measurements, registering an EC of 350. Other sources may vary widely, he said. Dugouts that still have water after an extended drought may be highly mineralized.
Calcium or carbonate in excess of 350 parts per million can affect low herbicide rates, such as the standard half-litre per acre rate, while higher rates typically used for killing perennial weeds could manage with water at an EC level twice as high.
For water containing bicarbonate, anything less than 500 EC won’t affect the herbicide’s effectiveness. But as that number approaches 1,000 EC, herbicides with common chemical names ending in “dim,” such as sethoxydim and clethodim, used in Achieve, Poast Ultra, and Centurion/Select, as well as 2,4-D amine, might see problems.
“(At around 500 EC) you start to worry about it, but it’s not a huge issue. But if it’s over 1,000 you’d start to get pretty leery,” said Holm.
Farmers with no alternative water source might compensate by using an adjuvant, such as ammonium sulfate fertilizer. Another product sold under the trade name Choice can also be used to clear up hard water.
When using ammonium sulfate to combat hard water problems, always add it to the water before the herbicide.
“Once the reaction between the herbicide and the water takes place, it’s irreversible,” said Holm. “If you put the ammonium sulfate in after the herbicide, you’re too late.”
High iron content in water is not a problem with most herbicides, except glyphosate, which bonds with iron.
“Glyphosate is the one you have to worry about. It is really inactivated by iron, worse than hard water,” he added. “Anything that is staining the plumbing red, you’d probably want to go look for a different source.”
Tom Wolf, a research scientist with Agriculture Canada, said iron might cause other problems by plugging tanks, hoses and nozzles.
“When iron is simply dissolved, it’s usually not a big problem, except for with glyphosate. But if it gets in contact with oxygen, it oxidizes and can form a precipitate that can plug up your nozzles,” he said.
The best solution is to dilute herbicides as little as possible. Already, most producers apply glyphosate in water volumes of less than five gallons per acre, he said.
“When you have a higher concentration of herbicide in the spray mix, then that herbicide is better able to withstand any potential antagonism,” said Wolf.
Many rural residents have their wells tested, if only to satisfy their curiosity about what’s in their water.
The good news, said Holm, is that testing just once is usually enough for a lifetime because the results are unlikely to change.
Using bad water over a number of years won’t lead to herbicide resistance, he added, just lousy results. Once a farmer recognizes the problem and starts using clean water, the weeds will be knocked flat.
