Why different application rates?

Discussion in 'Pesticide & Herbicide Application' started by JLC, Nov 20, 2001.

  1. JLC

    JLC LawnSite Senior Member
    from IA
    Messages: 467

    What are the theories behind application rates? I spray at 2 gpm, while I know some companies spray at 4 gpm and still others spray at 1 gpm. I am trying to get a dedicated treatment truck put together for next year and this will have a large impact on the tank size for the spray apps. Right now, 200 gallons is not near enough with a 2 gpm tip. Maybe someone can enlighten me on what the pros and cons of each are. I really want a medium duty truck with a 600 to 1000 gallon tank, but maybe I wont need it. Why do the TG/CL size companies use these big trucks?
  2. Scraper

    Scraper LawnSite Bronze Member
    Messages: 1,656

    From what I've ssen in my area, I would say half of the TG/CL truck is used for storing materials...not necessarily all one tank.
  3. JLC

    JLC LawnSite Senior Member
    from IA
    Messages: 467

    I know some have large storage areas, but alot of guys are running the big tanks too in the trucks.
  4. Runner

    Runner LawnSite Fanatic
    Messages: 13,497

    Ok. Here we go. Essentially, there are two different lines of thinking. The amount sprayed per minute, to cover X amount of area is broke down like this. When a higher amount is used to spray (2-4 gpm) the product can be dilluted down farther and put on at a heavier rate. This is actually more effective, especially when dealing like with liquidN or something like Dursban, or something. If you only spray 1 gpm, the material is at a much higher concentrate and there ais a safety factor considered there. Say someone with a 300 gal. tank, can spray much more area per tank with a higher concentrate and a smaler nozzle BUT there is much more risk there. For instance, because the droplets are much more fine at 1 gpm, there is much more drift and much more inhalation. If you come around the corner of a building, and a wind happens to catch you, well, there goes the bushes and shrtubs if you are spraying a post emergent hc. Most companies can't find guys to spray that understand these kind of things. When these companies have larger nozzles, it is a much safer application than with a smaller nozzle. (i.e. TG/CL) It's much like a showerhead compared to a mister. With a smaller nozzle, there is just tip contact witha higher concentrate, and with a larger nozzle, it's more of a soaking process. Like I had mentioned before, about Dursban (or any other insecticide) it is more successful to actually contact the soil, as to wet the leaf of the plant, because that isn't going to do anything unless the product is rained or watered in. It defeats the purpose. Evevn with these different amounts, the sprayers should of course still be calibrated to the operator. By this, the operator should cover 1m or 10m of area he would have been able to spray. That should be timed. Then the nozzle should be adjusted accordingly to the amount of product that should be going down per 1000 sq. ft. (Time the gpm, and divide by the oz. per gallon to be applied) I hope this clarifies things. :)
  5. Kent Lawns

    Kent Lawns LawnSite Senior Member
    from Midwest
    Messages: 870

    To make it very simple:

    Low volume = herbicides

    Mid volume = insecticides & fungicides

    High volume = fertilizers

    You need all that water to spray fertilizer. Low volume liquid fertilizer will burn turf.

    If you use granular fertilizer exclusively, then a smaller tank will accomodate your spraying.
  6. JLC

    JLC LawnSite Senior Member
    from IA
    Messages: 467

    Thanks for the excellent replies so far. Let me ask this then...I spray in the spring and fall with a postemergent for weeds and have granular fertilizer tank mixed to keep the lawn green between granular fertilizer apps. Would it be best to stay with the 2gpm tip or step up to a 4 gpm tip. Keep in mind an employee does 95% of my spray apps. With a larger tank and more volume of customers I want to keep the liquid fertilizer option (as opposed to water soluble granules) available as it could potentially be more cost effective not to mention faster to mix in. With the medium duty truck I've been looking at the Tuflex 1200 gallon tank which would definately be justified when spraying a 4 gpm. I want to be sure that I leave myself as many options available before I make this leap.
  7. Ric

    Ric LawnSite Fanatic
    Messages: 11,969

    Great posts everyone.

    I Got to get my .02 in.

    Ground speed X Tip size GPminute = rate/ M

    The bigger the tip the faster you can go. As for gal/M That depends on you soil, Pest Pressure, turf, and what product you are applying. In My area we have to use a high volume 5gal/M But your market is dfferent I am sure.

    1200 Gallon Truck WOW. Have you ever driven a tanker that big?? They are hard on brakes Gas and Insurance. That a lot of water sloughing back and forth even with baffels. Haft full they are a bear. At 4 gal/M it will do 7 acres. Do you spray 7 acres a day? 22 days a month? bi-monthly treatments would mean you could spray 13,416,480 sq ft of turf. Good Luck
  8. JLC

    JLC LawnSite Senior Member
    from IA
    Messages: 467


    Some of the biggest companies up here were running these huge tanks. The medium ones still have a couple of 600 plus gallon tank trucks.

    My 200 gallon tank treats 100k with a 2 gpm tip. If I understand correctly if I throw a 4 gpm tip on and everything else remained the same I would only be able to treat 50k. To get back up to 100k I would need to have a 400 gallon tank. As I mentioned earlier, on a good day I can treat 100k in a morning and have a dry tank halfway through my day. If I wanted to treat 200k with a 4 gpm tip I would need 800 gallons capacity. This also doesn't take into account feeding a boom sprayer with the tank. Depending on application rates of the boom sprayer, I may need every bit of a big tanks capacity. This is why I was wondering about my original question of application rates.
  9. Ric

    Ric LawnSite Fanatic
    Messages: 11,969


    gpm = Gallon per minute = tip out put

    gpM = Gallon per Thousands squre Feet. = RATE/M

    60-20 tip = 60% fan at 2 gal per minute at 40 psi

    60-40 tip = 60% fan at 4 gal per minute at 40 psi

    Ground speed plays the factor here

    Ground speed + out put gpm = Rate/M

    Runner & Kent summed up Rate per product why and wherefore
  10. JLC

    JLC LawnSite Senior Member
    from IA
    Messages: 467


    Thanks for all the help. Hopefully I will be able to get all of this figured out before next spring.


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