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Formula for square footage

Discussion in 'Pesticide & Herbicide Application' started by grassroots lawn, Feb 13, 2007.

  1. grassroots lawn

    grassroots lawn LawnSite Member
    Messages: 84

    Hey people, there is a formula for figuring how much nitrogen is in a bag plus how much that bag will cover. Example 15-0-5 = .15 x 50lb bag = 7.5lbs of nitrogen in that 50lb bag. For some reason I can't remember the rest of the formula. Saw is a couple of weeks ago, wrote it down and the little misses seemed to eat it up. Actually, I think it tells you how much the bag covers.
    thanks people.
  2. sclawndr

    sclawndr LawnSite Senior Member
    Messages: 326

    There's really no reason to know how much nitrogen is in a bag. You migh be thinking of how to figure out the rate.. Example - you want to apply one pound of nitrogen per 1000 SF and the nitrogen percentage is 15%. Divide 1 by .15 = 6.7 lbs/1000SF.

    The formula for coverage is weight/rate per 1000 square feet. Example - 50 pounds/6.7 lbs per 1000 SF = 7,463 SF coverage.

    Are you a licensed applicactor?
  3. grassroots lawn

    grassroots lawn LawnSite Member
    Messages: 84

    thanks sc.just had brain lock
  4. southernsprayguy

    southernsprayguy LawnSite Member
    Messages: 129

    Let me tell ya the easiest trick in the book when it comes to figuring out how many sq ft a bag of fertilizer will cover....eg. 15-0-15....divide the 15 (Nitrogen) in half x 1000 to get 1 # N....15 x 1000 will give you 0.5 # N. You can do the and get technical if you want but it works every time this way.
  5. RAlmaroad

    RAlmaroad LawnSite Silver Member
    from SC
    Messages: 2,253

    Things are subjective: That 50lb bag of 15-0-15 has 7.5 lbs of nitrogen and 7.5 lbs of (K)potash in it. If your analysis or recommendation if for example centipede grass which needs from .5 to 1lb. of nitrogen/1000 sq.ft. then that 50lb. bag will cover 7500-15,000-- sq. ft. of ground. Also the coverage is right there on the bag. You can adjust your needs based on these precentages--For example: a 50lb bag of 60-0-0 of nitrogen has 30lb. of nitrogen in it. The formulas are per 100lbs. The other 20lbs. is filler (Usually lime) in an all-mineral bag content.
  6. HydroRI

    HydroRI LawnSite Member
    Messages: 120

    I have attached a cheat Sheet

    Attached Files:

  7. RAlmaroad

    RAlmaroad LawnSite Silver Member
    from SC
    Messages: 2,253

    Based on the 15% nitrogen available in the 50lb bag, your chart is exactly right: For the required 1lb/1000sq. ft--total product is 6.7lb. Therefore your 50lb bag would give you 7500 sq ft of coverage. But keep in mind all grasses don't require the same amt of N. Turfgrass, for example, requires less N than does,let's say fescue and bluegrass. Good cheat sheet but after a while you can do it in your hear just as easily

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