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percent of nitrogen?

Discussion in 'Pesticide & Herbicide Application' started by daveand5, Jul 19, 2007.

  1. daveand5

    daveand5 LawnSite Member
    Posts: 3

    when applying urea mixed in water, 46% N, at a rate of 2 bags (100lbs) in 100 gals of water what would the % of N be? we seem to be having a disagreement at the actual rate to mark down on the state (MN) forms.one says 9% the other says 32%. Anyone know the correct way to calculate this?
  2. Runner

    Runner LawnSite Fanatic
    Posts: 13,496

    LOL. this is one of those trick questions that cannot be answered due to "insufficient data". It is like one of those "Train leaves Chicago" questions that there is no answer to. The reason being, is that this has to be calculated by rate, not content. In other words, if you mix 2 bags of 46% N to100 gallons, you have 46% N. Period. Now,...if you mix it in to 1000 gallons of water, guess what? You have 46% N.
  3. daveand5

    daveand5 LawnSite Member
    Posts: 3

    by rate if you mean application rate, its 2 gals per 1000sq ft
  4. ProMo

    ProMo LawnSite Bronze Member
    Posts: 1,468

    .46 lbs of n per gallon
  5. Ric

    Ric LawnSite Fanatic
    Posts: 11,956


    Your answer is approx 6% and here is how that is figured. A 100 gallons of water weights 833.33 Pounds the Urea is 100 pounds but only has 46 pounds of actual Nitrogen. When you mix the Urea you are not adding it to the 833.33 pounds of water but to a lesser amount to create a total of 100 gallons of finish spray that will weight close to 833.33 pounds but not exactly 833.33. The volume taken up by the 100 pound can be denser or less dense than water.

    Therefore 46 pounds of Nitrogen divided by 833.33 is .0552 or just under 6 % nitrogen. However go back to the fact we don't know the actual weight of the finish spray product. If in fact that 100 gallons of sprays weights 766 pounds then you have a real 6 % nitrogen solution. This means that 100 gallons with the urea in it would weight 66 pounds less than a 100 gallons of straight water.


    Sorry but you are mixing up Percentages and pounds of actual Nitrogen. The answer he is looking for is a percentage of Solution. Remember I taught this stuff at a college. Materials Calculations.
  6. daveand5

    daveand5 LawnSite Member
    Posts: 3

    thanks, with my observations, 500 gals water, 500 lbs 46% N, total mixed volum 550 gals, solution weight of 4670lbs, 8.49 lbs /gal, .418 lbs N, 4.91% solution of N.
    Thanks much!
    appears both foreman were wrong!
  7. tremor

    tremor LawnSite Bronze Member
    Posts: 1,476

    100 gals water = 830 lbs
    100 lbs Urea = 46 lbs N

    876 lbs/46 lbs N = 5.3-0-0
  8. Runner

    Runner LawnSite Fanatic
    Posts: 13,496

    Now take this info and run with it! :weightlifter: :drinkup: (no thanks to me):rolleyes:

  9. And at this rate, how many lbs/m of nitrogen would applied, if mixing 100 gal of water with 100 lbs of urea?
  10. heritage

    heritage LawnSite Bronze Member
    Posts: 1,268

    0.92 Lbs Actual N per 1000. (.87 A N if you wanna be really close ;) Quite the heavy shot for cool season turf in July IMO.

    Pete D.

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