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Need Help in Calculation, Please

beth4
15 years ago

I'm trying to spot kill some Bermuda grass from my Kentucky Blue Grass lawn. I've got a pretty good way to isolate the spray (pulling the Bermuda tendrils up through the spout of a cut-off gallon milk jug, and then spraying), so that most of the lawn will be protected.

However, I need some help figuring out how to convert the 44% Glyophosphate solution I purchased to a 2% solution when mixed with 1 gallon of water, so I can then spray the Bermuda. This is stronger than the typical Round-up, and was recommended by the fellow who fertilizes and weeds my lawn as being a more effective strength than the typical 1% Round-up solution.

The back of the Glyophosphate bottle says to mix 5 Tbs of solution to 1 gallon of water, but it doesn't indicate what that yields...whether that's 1% or 2% or what.

Would someone help me, and show me the equation, so I can figure out similar problems in the future?

Thanks so much for your help!

Comments (19)

  • bpgreen
    15 years ago

    There are 256 tablespoons in a gallon of water, so 5 tablespoons would be just under 2% of a gallon.

    Rounding up to 2% shows that the concentration would be .88% (just under the normal 1%).

    To get a 2% concentration, you'd need 2/44 * 256 tablespoons. That works out to 11.6363636 . . .

    Since there are 4 tablespoons in 1/4 cup, I'd call the number above 12 and say you want 3/4 cup of the concentrate to get to 2%.

  • digit
    15 years ago

    Wow, that sounds strong! Are you sure it is a 44% and you are trying for 2%?

    I use 41% Glyophosphate all the time in the flower garden - I'm going out in all this heat up here to use some now!

    The annual weed dilution at 3 Tablespoons per gallon is what I use on a regular basis. No, it does not kill perennials like bindweed but it puts a stop to their development. If I hit them again in a week or 2, they're usually "fried."

    I can't find 44% solution on the internet. But, no more time to look now. I'll be back after sundown and check this thread again.

    digitSteve

  • beth4
    Original Author
    15 years ago

    DigitSteve -- My older eyes mis-read the label. You are correct: It is 41% Glyophosphate. Yes, I'm sure 2% is correct. The fellow who treats my lawn (who really is a professional, with a masters in horticulture from our state Aggie university) was very clear that 1% would not kill the Bermuda. And, because Bermuda is so invasive, I need to be aggressive. He said I needed to create a 2% solution to do that....AND he emphasized that 2% would be over-kill for the weeds that I have in the perennial beds. About the only thing I should use the 2% solution on is the Bermuda grass and that @#&*$ Snake Grass.....another weed that drives me nuts.

    bpgreen: Thanks for the equation. "There are 256 tablespoons in a gallon of water, so 5 tablespoons would be just under 2% of a gallon. Rounding up to 2% shows that the concentration would be .88% (just under the normal 1%).
    To get a 2% concentration, you'd need 2/44 * 256 tablespoons. That works out to 11.6363636 . . .
    Since there are 4 tablespoons in 1/4 cup, I'd call the number above 12 and say you want 3/4 cup of the concentrate to get to 2%."

    I followed everything (THANKS for the TBS definition of 1 gallon!) except for the statement: "Rounding up to 2% shows that the concentration would be .88% (just under the normal 1%)." Could you explain that better so my feeble brain will understand?

    When I did the math for the 41%, I find that 2% = 5.12 TBS, and 5 TBS = 1.95% of 1 gallon. Substituting 2/41 for 2/44, I think I'll need 12.4878 TBS or 3/4 cup + 1/2 TBS of the 41% solution added to 1 gallon of water.. Did I figure that correctly?

    And that, I'm hoping, will put the Bermuda Grass and Snake Grass out of my misery!!

    Thank you guys so much for your help!!

  • bpgreen
    15 years ago

    I got the number of tablespoons in a gallon using google calculator (easier than converting 4 T in 1/4 c to gallons).

    I got the .88% by multiplying 2% by 44%. Since per cent means for each hundred, 2% is the same as .02, so I got .88% by multiplying .02 by 44.

    Your math is correct. You'd need 2/4 c + 1/2 T.

  • digit
    15 years ago

    Okay . . . I know absolutely nothing about Bermuda or Snake grass. But, I do find all the grasses I spray very easy to kill - quack, crab, etc. and the lawn grasses that sneak into my flower garden paths. So, both annuals and perennials and I'm not really sure why they are easy to kill. Perhaps because if the glyophosphate takes the roots out, there's nothing much left of the plant.

    I looked at the recommended rates for the Green Light Com-pleet and it is 1.5 to 2.5 fluid ounces - 3 to 5 Tablespoons per gallon water. And the recommended rates from Alabama Cooperative Extension System for all the glyphosates are about the same.

    2/3rds of a cup of 41% is more than double what ACES lists and about 5 times what it takes for me to kill quack grass.

    Just sayin' . . .

    digitS'

  • bpgreen
    15 years ago

    "I know absolutely nothing about Bermuda or Snake grass. But, I do find all the grasses I spray very easy to kill"

    Your link doesn't work for me.

    I don't have Bermuda, but everything I've read about it says that it is very difficult to kill.

    If you're willing to isolate the Bermuda the way you describe, you might have better luck using a diluted Roundup application for an extended period of time.

    Somebody recommended something like this for bindweed. Let the Bermuda grow first. Dilute the roundup to 1/2 strength and put it in some kind of jar. Snake some of the Bermuda into the jar and bury the jar to keep it from spilling.

    The idea behind this is that it keeps the weed alive longer, giving it more opportunity to translocate the glyphosate to the roots.

  • david52 Zone 6
    15 years ago

    I use 2 oz per gallon of that concentrated stuff, and it will kill any grass I spray with it. The advantage of that is I use a cheapo plastic meat baster to measure the stuff out of the bottle.

  • digit
    15 years ago

    Sorry . . . tired - 103° here yesterday afternoon. (Winds calm but probably around 60 mph here in front of the computer ;o)

    And the recommended rates from Alabama Cooperative Extension System for all the glyphosates are about the same.

  • bpgreen
    15 years ago

    I think it's interesting that the ready to use stuff is around 2%, but they tell you to mix the concentrate so that it's only about .8%.

    I know some people who used the concentrate to kill their entire lawn before reseeding elite KBG were complaining that it didn't work as well as the ready to use stuff. I'll bet that's why.

  • beth4
    Original Author
    15 years ago

    Hmmm....very interesting. My ready-to-use Round Up says 1% on the spray container. My lawn guy and I checked out all of my products on Friday, and when he saw the ready-to-use Round Up was only 1%, that's when he told me I needed to purchase the concentrated variety and mix it with water to achieve the 2% solution. He was very specific.

    I like the idea of putting the Bermuda tendrils in a pot of solution and leaving them...but I have too many, so that's not feasible.

    I think Bermuda is so difficult to kill because it is a woody plant (feel the stem), the roots are exceptionally deep and cannot be pulled up, and the grass spreads by its roots as well as by seed, so if not totally killed, it'll continue to spread across the lawn.

    Fortunately, it's in a small patch of my lawn, but there are many tendrils in that small area. So, I'll attack aggressively with the 2% solution...and I may well have to repeat applications. My lawn guy told me to leave it un-cut for 3-4 weeks, applying additional killer, to ensure the Bermuda takes the poison down to its roots and kills the roots.

    Thank you all for your help.

  • digit
    15 years ago

    Thank you Beth, we beat heck out of that one . . . NEXT!!

  • david52 Zone 6
    15 years ago

    Not wishing to be a pill, but are you sure you have Bermuda Grass? I was looking it up on the trusty inner-net and it wouldn't appear to be in either Utah or Colorado.

    I sure have some tough grass to deal with as well, my favorite is bromme grass, which shoots roots out about 3 feet and then they pop up.....

    Here is a link that might be useful: bermuda grass info. I have no idea if this is good stuff

  • bpgreen
    15 years ago

    I've seen some maps that show it in Utah. Here is one from the USDA plants database.

  • david52 Zone 6
    15 years ago

    Thanks, bpgreen. The Colo map doesn't have it in my neck of the woods, but the Utah map has it in San Juan Country, which is but a hop, skip, and a couple canyons over. I've got some sort of grass that looks suspicious. I'll get out my magnifying glass. The temperature limits on my link would seem to preclude it, but this wouldn't be the first time the plant never read the memo.

  • jaliranchr
    15 years ago

    Took me three years and plenty of frustration, but I finally succeeded using this method from a Utah site. :)

  • bpgreen
    15 years ago

    David--I was also told that if the map doesn't show it in your county, that doesn't necessarily mean it isn't in your county--just that the USDA hasn't documented that it is in your county.

  • digit
    15 years ago

    I had no idea that Bermuda grass was so hard to kill until I looked at Jaliranchr's Utah Extension page. Spray with glyphosate just to "make it mad." Sheesh!

    The map shows it up here but I'd be hard pressed to ID it.

    Steve

  • jaliranchr
    15 years ago

    Steve, it is a nightmare to try to get rid of. I hope you never have to deal with it. Patience is required, and several handfuls of hair. :)

  • beth4
    Original Author
    15 years ago

    Jail --

    Thanks for the link to Jerry's article on how to kill the dreaded Bermuda grass. Jerry writes a weekly horticulture column for the Ogden Standard Examiner, and I've always found his advice very helpful. I thought the article was helpful, but also a bit worrisome....it certainly corresponded with what my lawn guy told me, who got his Masters from Utah State University in horticulture. And the very worst part is that your lawn is still vulnerable in the future because of the way the grass spreads from neighboring lawns, sprinkler water (here in northern Utah, we use secondary, untreated water for our sprinkling systems), etc.

    I guess that's why gardening is a full time hobby!

    The good news is that my long Bermuda tendrils are not happy, after application of the 1st 2% solution. And, I'm going to give them another dose tomorrow, then wait a couple of weeks to hit again. I want to hit them the hardest while it's still hot and the grass is thriving.

    I hope the Colorado gardeners (my birth state!) never have to deal with this -- Ugh!