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Softened Water used for Herbicide Application (06/23/16)

Question: Rich, I received this e-mail message about switching from AMS to large commercial water softeners for herbicide application. Have you had any experience with growers using this for glyphosate applications etc.? Besides the cost what other downsides are there? Thanks!

Softened Water used for Herbicide Application

Question: Rich, I received this e-mail message about switching from AMS to large commercial water softeners for herbicide application. Have you had any experience with growers using this for glyphosate applications etc.? Besides the cost what other downsides are there? Thanks!

Answer: I direct you to the 2nd greatest book ever written - page 122 of the ND Weed Control Guide. It contains the formula that Dr. John Nalewaja, NDSU Weed Scientist developed to determine the amount of AMS needed to overcome hard water antagonism.

The amount of AMS needed to overcome antagonistic ions can be determined as follows:

Lbs AMS/100 gal = (0.002 X ppm K) + (0.005 X ppm Na) + (0.009 X ppm Ca) + (0.014 X ppm Mg) + (0.042 X ppm Fe).

Notice that the 2nd cation listed is Na and its relative strength of antagonism is 5 compared to Ca = 9, Mg = 14, and Fe = 42. Na is an antagonist. It is the basis of antagonism when Basagran is mixed with Poast where the Na from the bentazon binds with sethoxydim and antagonizes grass control.

One point that is even more important – soft water does NOT contain ammonium which is just as important as the sulfate which binds the cations. Ammonium drives the proton pump that enables weak acid herbicides to cross cell membranes and improve absorption and translocation. I wrote about this and more in last year’s crop and pest report.

Rich Zollinger

Extension Weed Specialist

 

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