Fertilizer Application Calculation

Discussion in 'Soils, Fertilizers and Composting' started by LilSprout, Oct 21, 2009.

  1. LilSprout

    LilSprout Active Member

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    How much Ammonium Sulphate (21-0-0) is required to apply 3 pounds of Nitrogen to 2392 square yards?
     
  2. cowboy

    cowboy Active Member

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    A 100 lb. bag of fertilizer will contain 21 lbs. of nitrogen. So, a simple ratio calculation tells us you need 14 lbs. of fertilzer applied over your garden area to give you 3 lbs. of nitrogen.

    100 - 21
    x - 3

    x = 300 / 21

    x = 14.3
     
  3. soccerdad

    soccerdad Active Member 10 Years

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    True enough, but since the answer is independent of the 2392 figure, I suspect that the questioner meant something like "3 lbs per thousand square feet".
     
  4. cowboy

    cowboy Active Member

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    Soccerdad, you may well be correct but I answered the question as it was asked.

    Certainly 3 pounds of nitrogen over 21,528 square feet (just under 1/2 acre) is not very much. If this application is for a lawn, then 3 pounds per 1,000 square feet is about right. Spread over two or three applications would be my choice.

    The other question would be, "Why all the sulfur?"
     
  5. soilguy

    soilguy Member

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    Ammonium sulfate (21-0-0) in an acid environment (coastal BC) is not adviced unless you have acid loving plants or need the sulfur to balance nitrogen - i.e., you are trying to improve protien in your crop. Sulfur is not really deficient here. I would suggest calcium nitrate or urea are better sources of nitrogen. 3 lbs of nitrogen per 100 sq ft is ample for individual applications to lawn. You may wish to consider a slow release nitrogen for grass so you don't get flushy growth. The numbers on a fertilizer bag refer to the percentage nitrogen (as N), phophorus (as P2O5) and potassium (as K2O). 21-0-0 also contains about 24% sulfur.
     

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