Math check for ferts

Discussion in 'Fertilizer Application' started by jerrylundergard, Sep 7, 2013.

  1. jerrylundergard

    jerrylundergard LawnSite Member
    Messages: 9

    Looking to apply 1 pound of ammonium sulfate and 1/2 pound of potassium nitrate per 1000sf. Will be applied in 2 gallons of water to st augustine grass in Miami, Fl.

    Im calculating that will be .28 lb of nitrogen total and .22 potassium. Anyone disagree? Sounds about right or should I put a tiny bit more ammonium sulfate in the mix? Thanx
  2. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,812

    I agree, although I get .275 lb N.

    However, I am a bit concerned about the chance of burning the grass from the high levels of nutrients in the solution. Look up the "burn potential" You should get advice from someone who has done this before. At least, test it on a small area first. Find out if its safe at the temperature and grass type you plan to use. And find out what happens if you apply a bit too much or overlap too much. Test it at double and triple so you know what can happen.
    Also Ammonium sulfate may not be fully soluble at high rates.
  3. bug-guy

    bug-guy LawnSite Bronze Member
    Messages: 1,033

    i'm not sure about that math, or i'm misunderstanding the question
  4. foreplease

    foreplease LawnSite Silver Member
    Messages: 2,062

    It would have helped if the OP had shown the analysis for both products but I agree with the math.

    AS 21-0-0?
    PN 13.5-0-44?
  5. jerrylundergard

    jerrylundergard LawnSite Member
    Messages: 9

    The AS and PN were standard analysis for both products.

    The question was about math check and has been previously stated it was correct.

    @Riggle. I chickened out a bit and went with 1lb AS and 1/4lb PN in 2gal agua. Was irrigated in for about 5 minutes immediately after application. No signs of burn on that so Im gonna try bumping up to my intended 1/2 lb PN with the 1lb AS in 2gal. This would be followed up with the 5min irrigation again.
  6. foreplease

    foreplease LawnSite Silver Member
    Messages: 2,062

    Right. I did not comment 2 weeks ago because Riggle had concurred by the time I read your question. It seemed asked and answered. Then Bug-guy said he was not sure about the math or did not understand the question. I provided the product analysis so he and others could better understand the answer that you yourself were not sure of. Many people know the analysis of those two products, but not everyone. By including the information even people who had never seen or used AS or PN could have affirmed your figure.
  7. greendoctor

    greendoctor LawnSite Fanatic
    Messages: 10,138

    You may apply up to 5 lb AS and 1 lb PN in as little water as is necessary to get both into solution. I need 5 gallons to get that much in solution. However, this is not to be done in hot weather nor is it to be left on the grass for any length of time before it is diluted with at least 5 minutes of irrigation. I am even spraying right ahead of an irrigation zone if applying to large areas. I apply these kinds of mixes to warm season grasses growing in Hawaii.

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