No farmers want to unintentionally alter the efficacy of their crop protection products because of water quality pumped into the tank. However, farmers may do just that if they do not have their farm water source tested every year and take the appropriate actions based on the results of those tests.
There are several factors in your water source that could lower the efficacy of your herbicide, insecticide or fungicide sprays.
In Saskatchewan, hard water (high magnesium and calcium levels) can be common in wells that tap into glacial water deposits. Wells in bedrock aquifers usually draw soft water, but can contain bicarbonate — even low levels of this compound can interfere with crop protection product effectiveness. In addition, water with high levels of bicarbonate but low levels of other anions (negatively charged ions) such as sulphate and chloride can reduce performance levels.
Furthermore, these water characteristics can change in the same farm water source from year to year, says Yvan Bruneau, general manager at Central Testing Laboratory in Winnipeg, Man. “Water can change depending on the type of source and use — well or dugout, geology, weather and environmental conditions,” he explains. “The best practice is to test once per year, to follow trends and changes.”
Labs usually offer a “spray package” of tests that include alkalinity, pH, calcium, magnesium, sodium, potassium, sulphate, calculated total dissolved solids, hardness, sodium absorption ratio and more.
Lab samples can be dropped off if the laboratory is close by, otherwise they should be sent by courier as mailing is too slow. Samples sent to ALS Environmental laboratories, for example, must be received within 30 hours of sampling (and must be accompanied by a submission form).
However, some growers also do their own quick water tests. A conductivity meter can be used to initially measure hardness. If the electrical conductivity value is higher than 500 millisiemens per centimetre, a hardness analysis should be done to check for antagonizing cations (positively charged ion). Paper test strips with a colour scale are a quick way to determine hardness. Paper pH test strips are also readily available.
Shelby LaRose, proprietary products manager at Loveland Products Canada in Saskatchewan, has provided a roundup of common water quality problems and possible corrective actions.
“Before doing any of these corrective actions, test your water to determine any problems you may have. Also consult the labels of the pesticides you are using to determine the correct water quality for the pesticide being applied,” she says.
If water is hard, growers can add a water conditioner agent (like Choice Weather Master) at 0.25-0.5%v/v to the tank first before adding any herbicide. “This will tie up the many ‘hard water’ molecules in your water source before tying up the herbicide,” LaRose says. “Adding products like ammonium sulphate (AMS), urea ammonium nitrate or other softeners will only take care of calcium and that may not be the only source of your hard water.”
Turbidity occurs when the surface water sources contain clay soils or soil from runoff. Turbidity can be reduced by adding aluminum sulphate to your water source, agitating and letting it sit for 24 to 48 hours.
Bicarbonate’s antagonistic effects depend on the presence of other ions including calcium, magnesium, sodium and potassium. “Any acid source, such as sulfuric or phosphoric will reduce the pH and prevent carbonate salts from forming,” says LaRose.
Water pH can be lowered with buffers, such as adjuvants with acidification buffers and water-conditioning agents. Being able to lower water pH will also help reduce the “tie-up” of herbicide molecules and will help with the efficacy of the spray solution, LaRose says. Lowering the pH works for most herbicide solutions except for sulphonylurea chemistries.