Spray water has become a hot topic in the last few years as surface water dries up and farmers seek out new water sources for spraying operations. Knowing the quality of your water is important for effective spray operations, yet it’s surprising how many farmers haven’t had their water tested.
A water analysis is the first step in determining whether a corrective measure is needed, and most retailers often provide this service for free.
Unless you have noticed an issue visually or had obvious pesticide efficacy issues, perhaps your water is just fine. In most severe cases, farmers know when they have an issue with water quality. But in less severe cases, a water test can help a grower decide if corrective action is needed and then help them narrow down which water treatment product to use.
Surface water or dugout water is an ideal water source with neutral pH, which makes it the most preferred option for spraying. However, once these areas dry up, the next option is often deep wells.
According to Clark Brenzil, the provincial weed specialist with Saskatchewan Agriculture, deep wells are often prone to high concentrations of bicarbonate, which are especially problematic on the southern and western border of Saskatchewan.
“As little as 500 parts per million of bicarbonate will antagonize when using products such as achieve tralkoxydim (Achieve) and Select-clethodim (Select/Centurion), which can prevent the active ingredient from being absorbed by the plant,” he said.
“On the south and west borders of the province, bicarbonate concentrations can run as high as 1,000 to 1,500 p.p.m.”
Hard water is the term used to describe water that is high in iron, magnesium or calcium ions. Bicarbonate is “soft” because soaps will make nice suds in waters high in these ions. Generally, the hard water ions are the positively charged ions (Ca++, Mg++, Fe++) with two or more charges on them. Bicarbonate is negatively charged (-HCO3) and binds to the positively charged ones to make calcium carbonate (CaCO3) or sodium bicarbonate (NaHCO3).
These salts can potentially cause issues with herbicides such as glyphosate and 2,4-D.
“In drier conditions these salts increase in concentration due to evaporation, so the situation actually worsens,” Brenzil said.
A water test can determine whether this is worth correcting. For example, at less than 150 p.p.m. of hard water ion (calcium/magnesium), it’s not worth adding a water treatment.
“Generally, if you have really hard water, you know you have hard water. But in less severe cases, water treatment products can affectively alter characteristics in water to improve spray efficacy with certain products. Water additives such as AMS (ammonium sulfate) and UAN (urea and ammonium nitrate) correct for bicarbonate.”
Brenzil references research done at the University of Saskatchewan in the early 1990s that altered water quality with different additives to get different responses with calcium, iron and magnesium.
“The results indicated that AMS worked to reduce bicarbonate antagonism and hard water antagonism up to a point, but there are waters that are hard enough that AMS will only reduce antagonism to a certain level until it plateaus.”
Brenzil said adding more glyphosate is one way to correct for this, as is reducing application water volumes. The U of S research didn’t include hydrogen sulfate or acidic AMS replacements.
” in the absence of hard ions and without an extremely high pH in source waters, greatly acidifying application water doesn’t improve glyphosate activity,” Brenzil said.
“Previous research has shown that acetic acid did not improve activity.”
Other salts that cause issues for farmers are iron and manganese.
“This is often seen in water where brown clouds of iron or black crystals of manganese are forming, which is very difficult to treat.”
Water pH seems to be the value that most farmers look to and on which most retailers base their hopes for selling products. These levels simply indicate if water is acidic, alkaline or close to neutral. Although it’s often said that glyphosate works better in acidic solutions, if your water pH is less than eight a treatment isn’t necessary. Most farmers are unaware that pesticides actually affect the pH of water as well. For example, the addition of glyphosate to a spray mixture may actually drop the pH of the solution from an eight to a four.
With all of the misinformation on water quality and products sold off of pH alone, it’s important for farmers to get their water tested and look beyond the pH value for information. It’s important that the water quality analysis includes pH, total dissolved salts, total hardness and bicarbonate levels.
When in doubt, do some research or seek out a second opinion from a trusted source, such as your local crop extension specialist or sprayers101.com, to determine whether a correction measure is required. Knowing the quality of water is important for pesticide application, especially because water quality can change over time. Alas, it’s too bad this research can’t be done on a rainy day.