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Finding The Actual Slow Release %

Discussion in 'Pesticide & Herbicide Application' started by The Ranger, Jan 21, 2006.

  1. The Ranger

    The Ranger LawnSite Member
    from NE Ohio
    Posts: 208

    Divide the slow release % on the label by the % of N in the bag; Example

    32-5-7 with 6.8% slow release N

    Divide 6.8 by 32 = 21% slow release N

    just a little help from a friend
  2. olive123

    olive123 LawnSite Senior Member
    Posts: 500

    but 32 is not the amount of N in a bag its the pounds of N per 100 lbs of product
  3. sildoc

    sildoc LawnSite Silver Member
    Posts: 2,925

    Ahh its the little things we over look that cause us so much greif.
  4. ThreeWide

    ThreeWide LawnSite Bronze Member
    Posts: 1,116

    Unless I missed something major, I don't believe that is correct. Percentage is based on the weight of the bag/container regardless of size.
  5. New Green

    New Green LawnSite Member
    Posts: 57

    Seems so confusing... 32 is the number of passes you make if the spreader is set at #7 leaving a 5 ft swath.. 32-5-7. :)

    BTW .. that formula is the same regardless of the lawn size.
  6. olive123

    olive123 LawnSite Senior Member
    Posts: 500

    DUH :dizzy:
    i was drinking last night and was feeling harsh this morning...
  7. The Ranger

    The Ranger LawnSite Member
    from NE Ohio
    Posts: 208

    The nutrient analysis on the label (32-5-7) represents the percentage by weight of the nutrients in the bag. 32%N, x50lbs. =16lbs of N, 5%P = 2.5lbs, & 7%= 3.5lbsK. The slow release formula in the original post represents how to figure what the slow release % is compared to the total amount of N. When they put slow release on the bag @ 6.8%, if you take 6.8% of 50lbs. = 3.4lbs. That means nothing unless you compare it to the total N. 3.4 divided by 16lbs of N = 21% 21% of the total N is slow the rest is fast.
    Or divide the slow relase N 6.8 divided by the N number (32) = 21% slow release N. Both answers are the same and right, the one involves less math. Sorry for the confusion.
  8. JBIRD33

    JBIRD33 LawnSite Member
    from Georgia
    Posts: 2

    Actually you have to know the type of slow-release to make and accurate calculation. As far as PPSCU goes legally 90% of the slow-release can be claimed unless product is sold in Florida then only 50 % can be claimed. This should be expressed in units of Slow-release
    Therefore a 50% slow release product like 32-5-7 would have 16 units of slow-release but the bag will say 14.4 units slowly available from PPSCU because of the 90% rule

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