The Round Up instructions at
http://www.horizononline.com/msds_sheets/pdf/rup25.pdf don't say anything
against using water with dissolved minerals, but they do say that reduced
results may occur if water containing soil is used, such as water from
ditches or ponds.

"Ether Jones" wrote in message
oups.com...

Round-up is deactivated in the soil almost immediately when it does
an ion-exchange with clay particles. It also decomposes in the soil.
It doesn't decompose in the bottle or sprayer.

A follow-up question if I may. Does it matter what kind of water you
use to mix with the Round-Up? I use well water. My well has some iron
as well as other minerals I suppose. Do these impurities tend to
deactivate the Round-Up?

The reason I ask is, everybody I talk to seems to have better luck with
Round-Up than I do. They say the weeds are dead in a week. When I
use it, it takes up to three weeks to see any difference at all; and
sometimes I have to re-apply.

I'm not skimping on the mixture. I even tried tripling the amount.

I'm using it on weeds in my gravel driveway and between patio bricks.
Also on my trail in the woods to clear underground on and around the
trail.

A farmer friend even gave me a gallon of the commercial-grade stuff he
uses, and it didn't work any better.

I suppose the next step would be to try mixing with distilled water.
Haven't had the time to mess with that yet.