Is your spray tank water negatively affecting your herbicide applications?

pH:

The pH scale measures the hydrogen ion concentration (acid or base) in water on a scale ranging from 0 (very acidic) to 14 (very basic) with 7 being neutral. Depending on the soil and geology of your area, the groundwater could have a pH value between 6 and 8.5. Open water sources like ponds or lakes could be even more variable. Municipal water is often treated to make it safe to use, but this could alter the pH further. More confusing still, the pH of your water source can, and often will, fluctuate throughout the year depending on seasonal rainfall and drought.

Some pesticides are sensitive to high pH water in the spray tank and begin to break down through a process called hydrolysis. This can affect the chemical stability of pesticides, meaning the active ingredients in the pesticide are changed, rendering them useless. For example, weak acid herbicides like 2, 4-D and glyphosate degrade rapidly in alkaline water (pH 8-9), reducing their efficacy. Unfortunately, some applicators increase the rates of pesticide in the tank to counter the reduced control. A better solution would be to check the pH of the spray water tank PRIOR to adding herbicides to the tank. Since the reaction can occur immediately upon addition to a spray tank, any necessary buffering must happen first.

Hardness:

Water hardness is determined by the concentration of dissolved minerals like calcium and magnesium. Hard water can negatively affect pesticides by binding with herbicide molecules, altering their chemical properties and reducing their effectiveness. Negatively charged pesticide molecules act like a magnet and attach to positively charged minerals (cations) in the spray tank. This may cause the chemically-altered molecule to not dissolve in water, penetrate the leaf tissue, or perform as it was intended.

Testing:

Testing your water sources for suitability prior to pesticide applications can provide valuable information on pH and hardness. As mentioned earlier, pH can fluctuate throughout the season and should be tested several times each season. Hardness is less likely to fluctuate, therefore a yearly check should be sufficient.

If a buffer is needed, select one that will accomplish the goals you are seeking. Just reducing the pH will not have any effect on the hardness. Helena’s Moveo® Formulation Technology, included in several herbicide offerings, removes carbonates and lowers the pH to optimize the effectiveness of the herbicides. No other buffer is needed.