# Using Roundup in a Tow Behind Sprayer



## targa (Jul 2, 2021)

I'm a new member and have a couple of questions about using roundup in a new 31 gallon Northstar tow behind sprayer that I just ordered.

I have used roundup for many years with my 1 and 2 gallon pump sprayers but wonder if it is safe to use in a tow behind sprayer that has a 12 volt pump? I know Northstar literature says its safe!

I also plan to spray liquid weed killer and fertilizer and wonder what the preferred cleaning procedure is for tank and hand sprayer wand after using roundup?

I would appreciate any input.

Thank you

Dom


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## LeeB (Jul 1, 2019)

If you are new then you need to practice using the sprayer with just water a few times first. Figure out your exact lawn square footage on Google Earth. For a 1 acre lawn I would divide it in half so you use one tank on each half and spray at a rate of about 40 gallons per acre (so this means you would only make about 20 gallons per tank).

If doing a practice with water, fill to ~20 gallons and drive around in an overlapping pattern and make sure you can cover the area without running out or having too much left over. Check your pattern by spraying on a driveway or road. If you are using 30 psi (good compromise), you should drive about 2.6 mph by my calculations. I use tractor-mounted GPS to monitor my speed to the nearest 0.1 mph while spraying so I can hit my target area on a tank.

When you actually want to do the spraying, it's very important to check that the winds are less than 10 mph and the Delta T (difference between dry and wet bulb temperatures) is between 4-14ºF. This is a measure of how humid it is, because you don't want to spray when it's too dry or too humid out. Typically this means you are going to want to spray by mid-morning after the dew has dried and the winds are calm, or spray later in the evening when the winds and temp is dying down. Also think of a favorable wind direction to look for in case you do get any droplets migrating downwind.

For cleaning the tank (spray till empty first), I would fill the whole thing up to the brim with water for a first rinse, and then go spray it out on your driveway, road, or some other area where it won't matter if it kills stuff. Run the wand too to rinse that out. The second full rinse can usually just be dumped out into your lawn as it will be very low concentration. I typically don't bother with a third rinse, or just do a few gallons since everything would be very diluted at this point. You should also rinse off the outside of the sprayer with a hose to get any herbicide mist off the outside. Leave the tank open to dry.

It's important to know that if you have hard water, it will inactivate roundup. Use softened water if available, or you'll have to add ammonium sulfate to bind the hardness ions. This has to be added to the water about 30 minutes before you add the roundup so it has time to work.


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## targa (Jul 2, 2021)

Wow! Thank you LeeB for a very detailed explanation and procedure to follow.


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