pounds of N calculation

Discussion in 'Pesticide & Herbicide Application' started by humble1, Jan 11, 2008.

  1. humble1

    humble1 LawnSite Silver Member
    from MA
    Messages: 2,519

    I wanted to ask a question I know part of it. If I buy a say 34-3-8 fert 33% scu and its labeled for 17,000 sq ft at 1 pound N per 1000. If i put it down at .8 pounds per 1000. formula is .8/34 X 100 equals pounds per 1000. 2.35 pounds per 1000 sq ft or a new coverage of 21,000 sq ft. My question is this
    what would my calculation change the bag N numbers to 27-2-6? I am trying to justify buying a higher N and being able to stretch the application out, and not burning the turf in hot weather, where appling the higher N at full rate would more lickely burn the turf. Im not sure if this is making sense. Also would be getting better coverage. plus if i put down 4 pounds n per year .8 for my 5 apps.
  2. sclawndr

    sclawndr LawnSite Senior Member
    Messages: 326

    What do you mean by "stretching the application out"? If the N number you're targeting is the same - .8 in your example - then a higher analysis will make a bag go farther in terms of square feet but won't change anything else. So whether you apply 2.96 pounds per thousand of 27% N or 2.5 pounds per thousand of 32% N, it's still .8 pounds per thousand of N. The only difference is you'll need fewer bags of 32%. If you don't want to burn the turf, use a higher SCU or reduce the N.

    The math is straight forward - divide the target N by the percent of N in the bag to determine the rate per thousand. Divide the bag weight by the app rate to determine coverage.
  3. (wi) Roots

    (wi) Roots LawnSite Member
    from 9
    Messages: 152

    Using your formula of .8lbs, you would get if using analysis 27-2-6= 2.96lbs/1000, Which, will convert to approx, =16,888 Sq.Ft. Or, 2.578 bags of 50lbs of fert per Acer.
  4. crazy4green

    crazy4green LawnSite Member
    Messages: 50

    i have used higher n for past couple years and in hot summer used bag per 21- 22 thousand. used less bags a year and lawns did look as good if not better than before. and it figures out to correct amount of lbs of n you want in a year. just be little care full in summer on those lawns that don't have irigation and cut back little more and using this method retention went up from 67% to 76% so if customers are happy i'm happy
  5. humble1

    humble1 LawnSite Silver Member
    from MA
    Messages: 2,519

    what i was trying to do was also shooting for if I am appling a 24-0-8 merit application to the area of the lawn that historically gets grub damage, and i want to apply fert to the rest of the lawn and get a good match. If all i have is a 32-0-10 75% scu how can i cut the amount to get a match, i maybe am not getting my question across on this senario.
  6. RigglePLC

    RigglePLC LawnSite Fanatic
    Messages: 13,810

    Merit 24-0-8 covers 14.3 Msqft. Since there is only 12 lbs of nitrogen you are applying about .84lbs nitrogen per 1000 sqft.

    32-0-10 has 16 pounds of nitrogen. Divide by .84 and get coverage needed of 19 Msqft. Close enough.

    But it is 75 percent scu--not sure it would act the same. I don't know what to do after that to make it comparable. Good luck.
  7. humble1

    humble1 LawnSite Silver Member
    from MA
    Messages: 2,519

    thanks that was what i was trying to arrive at. Do you think the slow release could pose a problem, i dont want to have various shades of green, but didnt want to blanket the property w/ merit as grubs are not a problem all over the yard.

    PSUTURFGEEK LawnSite Senior Member
    Messages: 579

    Just some advice, when using straight fert it's ok to go at a lower rate with a higher nitrogen but when your'e dealing in combo products and I am telling you from experience, for example 13-2-5 dimension .15 at the 5.6# rate you will get better coverage than if you use maybe 13-2-5 .21 at a lower rate.
    the theory behind this is more particles, anytime you can get more particles down per m2 you will have much better control. if you pour salt out on the table at a standard particle size you see the gaps, if you pour a mcdonalds salt packet on that same table you wont see many gaps between particles.
    This means a better soil barrier, I also would use a mini for combo's when possible, the cost is a little higher but the results and customer retention far outweigh the little jump in cost per bag.
  9. bug-guy

    bug-guy LawnSite Bronze Member
    Messages: 1,033


    private mess me your e-mail address and i will send you a fert. worksheet it's an excell spreadsheet( you will need excell) you just enter the fert anaylisis lbs of n you want per 1000 sq ft arces to fert and it will do the math. i use it at work a just made another one tonite if you want. you can enter dec. pts so you do .5 (1/2 lb) per 1000 if you want
  10. MStine315

    MStine315 LawnSite Senior Member
    Messages: 789

    Why not use .5G Merit on areas you need grub control and your 32-0-10 on the whole lawn? You're still making 2 trips, just one is over more area, but then you don't worry about varying amounts of N and would seem to be a lot less headache. I appreciate your line of thinking, just a thought.

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