Is your spray water killing your herbicide?
The Purdue weed specialists report that extreme pH levels, such as below 5.0 or above 8.0 not only affect the performance of the herbicide but also impact its residual in the soil. And the last thing you want to do is pay a lot of money for an herbicide and have it last only half as long as it should. Extreme pH levels will also reduce the solubility of the herbicide and leave residues in your tank that will clog screens and nozzles. Such residue can also react with the next herbicide you use and neutralize it. If you need to use water to fill your sprayer that has an adverse pH, there are pH adjusters that allow you to create the optimum chemistry for your herbicide. But before you use a buffer, consider whether the herbicide already has one.
Sometimes rural water sources are very soft and others are very hard, with a lot of mineral content. The hardness level of the water and the metals in the water can also have a dramatic effect on your spray efficacy, such as reducing their ability to be absorbed into the plant tissue. To the rescue is ammonium sulfate or AMS which has ions that bind with the cations of the other metals, and increases the absorption of the herbicide into the weed tissue.
Grass herbicides such as SELECTMAX, Poast, and growth regulators like 2,4-D can give a poor performance if your spray water has a high level of carbonates and bicarbonates. A tank mix with diammonium sulfate could help overcome the problems but it needs to have the right amount. Check the source page for information on computing the amount of AMS to use.
If you are pumping spray water from a drainage ditch, there may be a turbidity problem with mud and cloudiness. The presence of organic particles such as soil can bind to the herbicide molecules and neutralize them. Such particulates can also clog screens and nozzles.
The bottom line for spray water is a wide variety exists, and many can innocently be acceptable for nearly all uses, except as a carrier for your herbicide spray. Spray water from ground wells can vary widely in chemical makeup, particularly in pH, turbidity and hardness. Depending upon the needs of the herbicide, the well water used for spraying may have to be modified.