One of my earliest experiences with the effect of mixing water quality on the effectiveness of spray solutions occurred years prior to my joining the Extension Service. I overheard a producer comment that an application he had made the previous day had shown almost no effect on a severe population of Sesbania (coffeeweed) in his soybeans.
He had treated a field with the recommended rate of aciflourfen and was now ready to accuse the manufacturer of “watering-down” the product. I asked him to show me the field, and sure enough I could see very little evidence of an application except for his tire tracks in the mud.
A sample of water from his well showed that the pH was above 8.0. We added two gallons of vinegar to the next 200 gallon batch and allowed it to agitate before pouring in the chemical. Within an hour we could see that this application was working well and he actually went back and sprayed the original field again.
Today, every chemical dealer has good buffer materials that can be used instead of vinegar even though this useful material is still fine for improving the activity of products for gardeners.
The fact is that very little emphasis had been given to the importance of pH and other aspects of water quality in any of the courses I had, or at least I did not come away with an awareness of the importance of this issue. The fact is that today many of the products we use for control of weeds, insects, and diseases in crops are strongly influenced by the quality of water being used for applying them.
These products are far too expensive to risk losing their effectiveness to something this easy to correct.
Pesticide applications require attention to the issue of water quality as well as selection of the correct product, calibration of sprayers, good timing to take into consideration all the factors of weather, crop stage, and of course the label of the product being used.
We have become “spoiled” to the convenience of just filling the tank with water, pouring in the product, and spraying it out when there are many issues that can make or break the success we expect from these materials.
I realize that there are many people who are very professional as they go about the task of applying agricultural products, but I expect that for every one that does it right there are several who don’t. They are either unaware of the issues I am talking about, have forgotten how important they are, or simply ignore these issues and wonder later why their applications may not have performed well.
Determination of water quality requires extra effort and it should be done before the day the applications are to be made so that when buffer materials are needed they can be there and ready for use.
This is another issue that even the grower who is aware of it may get in a rush and fail to test and buffer the spray water prior to pouring in that expensive product. Then by the time he reaches the field and takes a lunch break much of the active ingredient has been lost.
Many of the materials we use regularly are susceptible to breakdown in alkaline water. These include but are not limited to selective grass herbicides, many true liquid insecticides, and glyphosate. Some defoliants lose much of their effectiveness when this issue is not addressed.
This year make sure your products work as well as they should by testing your spray water and dealing with this consideration. We can’t afford to retreat with commodity prices like these.