How sure are you do the 1.7 lbs/gal for the ammonium sulfate? That sounds like too much.
Actually, pretty sure. I found that it even helped our softened water due to the residual carbonate ions in our softened water. (Water softeners only remove significant amounts of calcium and magnesium.) All of the other ions come along for the ride and can cause issues with glyphosate absorption.
AMS works two ways; one by making the glyphosate more absorbable by plants by masking the calcium and magnesium ions that tend to make the roundup insoluble and therefore unavailable to the plants, and two, by providing a burst of available nitrogen that encourages rapid leaf growth.
Some sites allow up to half of that, but if you look at the original papers, the higher dose is what is most effective. Harder water benefits from the higher dosing more than water that is more pure. Again, given that you are having issues, I would start at the 1.7lbs/gallon of final mix, and once you have baseline effectiveness, you could titrate it back down, if you want. For me, my time is valuable enough that I don't like to respray, so I mix at the higher level. AMS is cheap.
To mix: Add most of the water first, then add the ammonium sulfate, mix, and when the ammonium sulfate is fully dissolved, add the glyphosate.
You can read more here;
Glyphosate is one of the most widely used herbicides in the North America. The widespread use of glyphosate is due in part to its very broad weed spectrum and high efficacy. Additionally, glyphosate-resistant crops allow the in-crop use of the herbicide without the risk of crop injury. This Crop...
www.pioneer.com
Reports from farmers indicate potential troubles with plugged sprayer screens.
www.canr.msu.edu
Jeff Stachler, NDSU and U of M weed specialist, says you can get better weed control by following these steps.
www.farmprogress.com
There is a web calculator, if you want to plug in your specific water quality values to get the minimum ammonium sulfate level.
Water is a universal solvent that serves as the primary carrier for pesticide applications. The quality of the water used as a carrier can have a large influence on the performance of herbicides such as…
smallgrains.wsu.edu
I couldn't get the calculator to work for me, but perhaps it works for you.
One note: glyphosate works by preventing water absorption in the roots, so leaves have to absorb the glyphosate, the glyphosate has to get moved to the roots, and then there needs to be enough water demand (heat, rapid growth, etc.) to dehydrate the plant to kill it. No absorption, no heat, no growth, or lots of rain after the application and it won't work well. Adding surfactant really helps cut through the leaf oils for good absorption for oily leaves like poison ivy, poison oak, etc.
All the best,
Peter
www.farmprogress.com
