Category: General Operation

Articles that discuss general field sprayer operation and productivity factors

  • How Do Hydraulic Low-Drift Nozzles Work?

    How Do Hydraulic Low-Drift Nozzles Work?

    Low drift nozzles have become the standard way to apply pesticides from a boom sprayer. In order to use them properly, we need to understand how they are designed and how they are intended to work.

    Sprayer nozzles have three functions on a sprayer.

    1. Metering flow
    2. Atomizing liquid
    3. Distributing liquid uniformly

    Accurate metering of the flow is done through precise machining or molding of the nozzle.

    Atomization of a liquid occurs by imposing some sort of force on the liquid that causes it to break up from a stream or a sheet into droplets of the desired spray quality.

    Distribution is done by generating a pattern that, in combination with adjacent nozzles, produces similar dosages in appropriate droplet sizes and densities, along the target area.

    All three of these functions are confirmed by the nozzle manufacturer, but the properties are likely to change with wear.

    Atomization

    Atomization forces could be air-shear (used in some aircraft, airblast, or twin-fluid nozzles), centrifugal energy (used in rotary atomizers), electrical energy (used in some electrostatic sprayers), or hydraulic pressure (used in the most common nozzles, the flat fan or hollow-cone tips).

    Typically, the higher the applied energy, the greater the break-up of the spray. More air-shear resulting from faster aircraft or fan speeds, faster rotation of a cage, or more hydraulic pressure all have similar effects: they create finer sprays.

    Most nozzles produce polydisperse sprays, comprised of a large number of different droplet sizes. For hydraulic flat fan nozzles, droplets ranging from 5 to 2000 µm can be produced. The exact distribution of the volume in these droplet sizes depends on the nozzle design, the spray liquid, and the pressure. Here are three examples, representing approximately Medium, Coarse, and Extremely Coarse sprays.

    Droplet size distribution by number and volume from a Medium spray. Note the majority of the droplets are small, but the majority of the volume (dose) is in somewhat larger droplets.
    Droplet size distribution by number and volume from a Coarse spray. Like in the Medium spray, the majority of the droplets are small although there is fewer of them. The majority of the volume is in intermediate sized droplets.
    Droplet size distribution by number and volume from a Very Coarse spray. While the majority of the droplets are small as in the finer sprays, their overall number is sharply reduced from the finer sprays. The volume is now in the largest droplet sizes.

    Let’s focus on hydraulic nozzles, by far the most common in agriculture.

    Spray Pressure

    Spray pressure is a useful tool for controlling droplet size from any hydraulic nozzle. Need a finer spray?  Add pressure. It is also the basis for the age-old recommendation that lower pressures are a good tool for reducing drift.

    We impose practical limits on the upper and lower range of recommended pressures based on several other factors, chief among them the spray pattern.

    Spray patterns of a certain width, or angle, are required for proper pattern overlap. The convention is to space hydraulic nozzles at 15 or 20 inch intervals along a boom, and operate them at about 20” above the target. Boom height values will depend on the fan angle of the nozzle and the degree of overlap required. For low-drift flat fan tips, a minimum 100% overlap is best. With 100% overlap, the spray pattern width at target height is twice the nozzle spacing. With this approach, at any point under the boom, the target receives droplets from the closest two nozzle patterns.

    Pattern angles are published by manufacturers, but in practice, angles often differ from those values and can vary with spray formulation. Importantly, they tend to become narrower at lower pressures. The exact pressure at which this happens depends on the tip design, but experience shows that pressures below 20 psi for conventional nozzles, and 30 to 40 psi for low-drift nozzles, result in poor (too narrow) patterns. Narrow patterns reduce overlap, resulting in poor distribution.

    TeeJet AI11003 at 20 psi
    TeeJet AI 11003 at 80 psi

    We might also limit pressures at the upper end, based on drift potential. Most conventional flat fan nozzles, for example, drift excessively at pressures above 60 psi or so, hence that limit.

    Low Drift Nozzles

    Low drift nozzles were quickly adopted by applicators due to their ability to reduce drift and thereby widen the window of safe spray application. They work by using a two-stage design (often called “pre-orifice”) to reduce the internal operating pressure of the tip. The pre-orifice, the original liquid inlet, is round and sized for the nominal flow of the tip. The exit orifice is eliptical in shape and has a larger flow capacity than the pre-orifice, by about 1.2-fold to 2.5-fold. The larger exit creates an internal pressure drop, so the pattern formation produces larger droplets as though the operating pressure had been reduced. Most modern low-drift tips also introduce air into the nozzle via a built-in venturi. This further suppresses the formation of driftable droplets and introduces air into the interior of the nozzle, adding some pressure back to the system.. The Albuz AVI nozzle schematic below explains the venturi design.

    Cross-section of the Albuz AVI venturi nozzle.

    The tapered channel inside the nozzle is a venturi, which draws air into the nozzle via integrated ports. When low-drift nozzles are operated beside conventional nozzles at the same pressure, low-drift nozzles produce much fewer driftable fines, and also more larger droplets.

    But while the two-stage design is useful for managing drift, it also conceals the actual operating pressure of the exit orifice in these tips. The exit orifice is important – it is the part of the nozzle that does the atomizing and that forms the pattern.

    Let’s illustrate the pressure inside a low-drift tip by operating an air-induced low-drift nozzle at 60 psi. This nozzle has a pre-orifice size of 03 (0.3 US gpm at 40 psi, blue) and an exit orifice size of 06 (0.6 US gpm at 40 psi, grey). The operator sees 60 psi on the gauge. What is the exit orifice pressure?

    The exit tip has twice the flow-rate of the pre-orifice, and therefore operates at one quarter the pressure, or 15 psi. Recall the square-root relationship between flow rate and pressure.

    The relationship between spray pressure and flow rate. Doubling the flow rate requires a quadrupling of pressure

    That’s not the whole story. The internal venturi is drawing additional air into the nozzle chamber, and depending on the operating pressure, this could be from 5 to 15 psi. The amount added depends on the specific nozzle, its flow rate, and its pressure. Let’s add 10 psi in this case. The exit tip is actually at 25 psi.

    Now let’s assume the pressure gauge reads 40 psi, and that the venturi generates 5 psi additional pressure. The actual exit orifice pressure is now only 15 psi. This is at the lower limit at which a spray is atomized, and at which a good pattern can form.

    Our general recommendation with venturi-style low-drift tips has been to avoid pressures below 30 or 40 psi for that reason. We’re trying to prevent the spray becoming too coarse for adequate coverage, and also to prevent the spray pattern from collapsing.

    The upside of this design is that the same principle allows for much higher-pressure operation without creating excessive drift. These types of nozzle can, in fact, be operated at 70 to 90 psi without becoming very drift-prone because the pressure at which the spray liquid is atomized is likely only 30 or 40 psi (the actual exit pressure and drift potential will depend on the nozzle and the formulation).

    Speed Range

    A low-drift nozzle with a pressure operating range from 30 to 90 psi (i.e., 3-fold) would have a flow rate range of 1.73 (i.e., the square root of 3 due to the square root relationship of flow rate and spray pressure). This means that the fastest travel speed (at 90 psi) would be 1.73 times the slowest travel speed (at 30 psi).

    A conventional nozzle operating between 20 and 60 psi would have the same travel speed range. So why don’t we just do that? The main reason is that the two-stage design lowers the overall amount of drift substantially, something a conventional nozzle can’t achieve even at very low pressures.

    A second reason is that even at high pressures, a two-stage design will likely drift less than an conventional nozzle. This is still the case if the conventional nozzle is operating at low pressures. Any spray quality chart comparing spray qualities of conventional and low-drift tips will demonstrate that.

    Pulse Width Modulation

    PWM uses a solenoid to intermittently shut off nozzle flow, between 10 and 100 times per second (Hz) depending on the manufacturer. This has implications for nozzle design because the nozzle must not leak liquid during the brief off-cycle. If it does, the small amount of liquid leaving the nozzle will not only not atomize properly, it will also cause a pressure drop within the nozzle which must be replenished with the next on-pulse. This will mean the on-pulse will operate at a lower initial pressure, affecting pattern development and atomization. For this reason, venturi-style low-drift nozzles have not been recommended with PWM. The venturi provides an alternate exit for air or liquid, compromising nozzle performance.

    And yet, some venturi style nozzles do, in fact, produce acceptable patterns with PWM according to the nozzle manufacturers. This goes to show that nozzle design can continue to evolve to provide the best in drift reduction technology with PWM. Design for PWM suitability should be at the top of nozzle manufacturers’ agendas.

    Nozzle design continues to evolve. But in the foreseeable future, spray pressure will continue to control pattern width and droplet size. That’s why understanding the pressure limits of any specific nozzle type, and maintaining pressure within those limits, is so important in any spray operation.

  • Three Features that Should be Standard on all Sprayers

    Three Features that Should be Standard on all Sprayers

    One of my main activities in the winter is public speaking. Attending producer meetings gives me the privilege of meeting many farmers, learning about their operations, and sharing my research results.

    I enjoy providing practical solutions to problems. But there are three issues that always come up to which I wish I had better answers. Here they are:

    1. The Correct Spray. We’re stuck with compromises in this area. We need small droplets for coverage. We need large droplets for drift control. We need to keep application volumes moderate for productivity. We’ve basically asked the nozzle to shoulder the entire burden of our application needs, seeking a spray that hits all the right notes. Not too fine. Not too coarse. Able to work with fast and variable travel speeds and high, variable boom heights.

    Based on our research in field crops such as wheat, canola, corn, lentils, etc., we can be confident that Coarse, even Very Coarse sprays, coupled with a reasonable water volume, are appropriate for most modes of actions and target situations. These sprays contain enough small droplets for good coverage, and their larger droplets work surprisingly well in most cases. Sure, a finer spray could save some water. And a coarser spray would reduce drift even more. But we need a compromise spray, combined with some lucky weather, to get the job done.

    And yet we usually make spray quality recommendations with caveats, because droplet size alone isn’t enough. Drift is always a possibility, no matter how coarse we go. Coverage is not guaranteed, especially if the canopy is dense. Finer sprays will get deeper into a broadleaf canopy, but then we may have drift or evaporation to deal with.  The nozzle size, volume, and travel speed relationship has to be just right so the spray pressure is in the correct range. And on it goes.

    I’d like to give the overworked nozzle some help. We used to use shrouds to protect fine sprays from drift. Now it’s time to let air assist take over that task.

    Air assist booms can accelerate (i.e., add kinetic energy to) small droplets so they’re less prone to off-target movement. Properly adjusted, air assist can carry these droplets deeper into the canopy and enhance their deposition.

    A good air-assist system allows the user to select the strength and direction of the airblast to match canopy, boom height, and travel speed conditions.

    Air assist is the workhorse of most fruit-tree and vineyard spraying.  It has to be done right to provide all the benefits I mentioned, and certain approaches should be rejected. For example, there are some companies using air assist to promote very fine sprays with very low volumes. That’s the wrong use of the technology, and invites a backlash.

    Instead, we need systems that work with existing spray practice to address some of its classic shortcomings, such as drift management, deposit uniformity, and canopy penetration.

    Let’s see some products. It’s time to bring air-assist to the mainstream of agricultural spraying.

    1. Boom Height, Level, Sway and Yaw Control. Boom height is so fundamental it’s almost boring. We’ve long said that it’s important to set the boom at the right height for proper nozzle overlap and drift control. It was easy with wheeled booms. But over the last 15 years, suspended booms coupled with fast speeds have caused booms to rise again (RISE OF THE BOOMS!).

    Fact is that there are some tasks we’re asking of nozzles that they simply can’t achieve without level, low booms. Drift control is one such thing. Low booms are surprisingly effective at reducing drift, not only because winds are lower closer to the canopy, but also because droplet velocities are faster closer to the nozzle.

    Angled sprays for fusarium headlight control are another thing that is more effective with low booms.

    Spray droplets released from an angled spray soon slow down and get swept back by air resistance and begin to fall vertically, or move with wind currents, reducing their intended benefit. Low booms can prevent that.

    Uniform and low booms also keep deposit variability more manageable. They can save energy needed for air-assist systems. The shorter the path to the target, the less air-velocity will be needed to get it there.

    So how about it? Can we have boom linkages and suspension systems, coupled with sensors and hydraulics, that are stable and maintain 20” above canopy at 16 mph on uneven ground? Can we have systems that do this reliably enough that we’re prepared to invest in, say, expensive nozzle bodies? It’s possible.

    1. Sprayer Cleanout. One of my favourite questions about cleanout is: “When do you know that you’re finished cleaning the sprayer tank and booms?” Inevitably, someone from the back yells: “In two weeks!” And we laugh, knowingly.

    We have a terrible system of sprayer decontamination. It’s a process that is awkward, imperfect, and time consuming, often leading to poor practice. I’ll ask a group of producers what they do with their pesticide waste. The response is silence. I don’t blame them for not telling me that they dump the remainder on the ground somewhere, but I’d rather they didn’t. Sprayer designs don’t help.

    What we need is a system that guarantees results. To start, a tank gauge that is reliably accurate to the nearest gallon would remove some of the filling guesswork and help minimize leftovers.

    We need a remainder volume (volume left in the non-boom plumbing after the pump sucks air) that is known and small, because that remainder can’t be expelled and needs to be diluted. The smaller it is, the easier it is to dilute.

    We need pumps that can run dry, so nobody has to fear spraying the tank out completely.

    We need a wash system that requires little volume and works quickly, like continuous rinsing.

    We need plumbing that is easy to understand and whose inside surfaces do not absorb pesticide, or hide it in corners and dead ends. Perhaps it’s a recirculating system. Perhaps it hasn’t been invented yet.

    We need pesticide formulations that clean up easily. We need an easier way to inspect and clean filters. And we need a safe place to put any waste that can’t be sprayed out in a field.

    I’d like to see a sprayer that can be decontaminated in 10 minutes without the operator leaving the cab, and without any spillage of spray mixture. Clean enough to spray conventional soybeans after a tank of dicamba. Clean enough to spray canola after a tank of tribenuron. I know it’s possible.

    I also know what many of our European readers are thinking right now. Much of what I’ve discussed exists in the EU in some form or another. Why does the North American, and to a lesser extent the Australian market, not have these features?

    Part of the reason is federal standards and regulations. Some European countries test and approve products for remaining tank volume, boom stability, and spray drift, for example. Others have sprayer performance criteria that must be met to be eligible for sale in that country. An increasing number have mandatory sprayer inspection.

    These requirements serve to protect the producer and the environment. They’re an example of useful government actions. Despite, or perhaps because of, stricter rules, the entire EU marketplace is very competitive, with about 75 sprayer manufacturers. Bottom line: producers benefit.

    We need leadership, preferably from a combination of government, industry, and producers, to achieve better sprayer designs. Our market has room for products that make it easier to prevent drift, protect water, and protect yields.

    As they say, a rising tide lifts all boats. And it will certainly make my job easier.

  • Boom Collisions on Twitter

    Boom Collisions on Twitter

    An interesting technology recently came to our attention. The Horsch BoomSight detects potential obstacles and as the sprayer passes it raises the boom to avoid the impact. We figured it was worthy of a tweet, which read:

    The Horsch BoomSight

    @Spray_Guy:
    Ever accidentally hit something with your boom?
    <35 km/h, perhaps the Horsch BoomSight can help:
    http://bit.ly/2j6ShBx

    Now, when you tweet something, you hope it has some impact. That’s usually a few “likes”, maybe a few “retweets” and if you’re lucky someone may take the time to write a response. We received the following response:

    @WcropW:
    Yes, often bumping into kangaroos as they hop out of my crop.
    Got to be quick to lift boom above them!

    @Spray_Guy:
    Still can’t decide if that’s a joke or not, but it certainly made me laugh.

    ‏@WcropW:
    Was looking for picture – definitely true! Has happened 3 or 4 times!

    @spraydriftgirl:
    Definitely true! Plague numbers in crops down here #strayamat.

    @ryan_milgate:
    Yep I’ve hit plenty of kangaroos, esp in canola.

    @Wilkshag:
    Kangaroo- out side window of sprayer. They get stuck jumping through canola.

    @Spray_Guy:
    Wow! What a photo!
    Is there any product registered for kangaroo in canola in Canada?

    Photo Credit: Randall Wilksch

    —

    And so, it got us thinking… What other strange and unexpected things do sprayer operators hit, or nearly hit, during all those hours of spraying? So we asked:

    @Spray_Guy:
    Hey Twitterverse!
    What’s the strangest thing you’ve hit with spray boom?
    “Kangaroo” currently in lead.

    In less than 48 hours, that tweet earned more than 10,000 impressions as the Twitterverse shared all. What follows is a slightly edited transcript of that thread: snarky responses, pictures, videos and all. We don’t know if there’s any educational value, but it’s certainly fun and surprising. No one wrote “fencepost” or “tree”. They covered everything else, though.

    —

    @SteveTwynstra:
    Wild Turkey!

    @Spray_Guy:
    Is that what you hit, or WHY you hit?

    @SteveTwynstra:
    Jumped right up outta the standing wheat 50 odd feet to my right.
    Next day, grazed a fawn 2 fields over…

    @Spray_Guy:
    Putting the “Bam” in Bambi.

    @SteveTwynstra:
    The doe did give me a dirty look…..

    —

    @MarkDavis0129:
    I snagged a boat, dragged it 150 yds.
    The fisherman had quite the look on their faces once I stopped.

    @Spray_Guy:
    A BOAT!?
    Nope… I’m pretty imaginative, but this escapes me.
    How was that possible?

    @MarkDavis0129:
    It’s true, have land right to shoreline in few spots.
    Turning on head land and snagged it.

    @Spray_Guy:
    Priceless.
    I’m still laughing picturing that.

    @MarkDavis0129:
    Was last fall, 18′ alum flat bottom, they were nosed up to shore, snagged boweye on boom tip.

    —

    @Paulvdb2016:
    I have hit an abandoned small liquid manure spreader in a fast turn.
    Boom hit at 30+ mph!

    @Spray_Guy:
    The $hit hit the flatfan…

    —

    @AgronomoOz:
    @Pontaragrain has hit his own drone and put it on Youtube.
    #honesty

    @Spray_Guy:
    Ouch.
    UAV’s aren’t cheap.
    Got the link, Andrew?

    @CrystalSeedSeer:
    Let’s hope crop inspector isn’t in there! LOL!

    @Spray_Guy:
    From this thread, it seems like he’d be at risk of being hit, too!

    Turn up the volume on this video.
    Great soundtrack! Shared with permission from Michael Pfitzner (@farmingfitz)

    And believe it or not, it’s happened to more than one person. Bad time for battery to run low.
    Shared with permission from Warwick Holding (@Pontaragrain)

    —

    @MattTolton2:
    I’d only run a sprayer a few months but once slapped a duck out of mid air.

    @Spray_Guy:
    A solid example of booms set too high… or ducks too low.
    Tell me you shouted “DUCK”!

    @JoannaMWallace:
    This thread is winning Twitter for me today.

    —

    @vg_tim:
    Knocked over a wild turkey and porcupine at same time. Years ago, but can still remember.

    @Spray_Guy:
    Yikes… what were they doing when you hit them? #Darwinwouldntapprove

    @vg_tim:
    it seemed suspicious, they were just standing in a bean field looking at each other…

    —

    @DavidKucher:
    I may have hit an oilwell or two.

    —

    @MaizingPete:
    Almost hit a hippy sleeping off a punk party in the fence line.

    @Spray_Guy:
    LOL! You may have de-throned ‘kangaroo’ with ‘hippy’! We still have hippies?
    We have hipsters… we should hit more of them.

    @MaizingPete:
    For sure Hippy… That poor b@stard thought he was still in Woodstock.

    —

    @BlackPearl152:
    I gave two coyotes a good spank with the boom once.

    —

    @cropperandy2:
    Have hit deer, a coyote, in ON and a moose in AB.

    —

    @jamesschiltz85:
    1982 International cab cover.

    —

    @GregOldhaver:
    Had a flock of partridge lift up and get smacked out of the air with boom.

    —

    @cjrnumber6:
    An endangered Lesser Prairie Chicken.

    @Spray_Guy:
    Somewhat more endangered now, it would seem…

    —

    @DarLinFarms:
    Travel trailer.
    Guy drove into boom unfolding infield.
    He watching as unfold.
    Crash into me.

    —

    @Joe_Widdup:
    Had a near miss with a guy who stopped to take photos.
    Scared the hell out of me.

    —

    @Luckycangus:
    Deer and sharp tail grouse.

    —

    @RowcropAust:
    Emus at night go crazy in the lights.
    I have hit a couple over the years.

    @Spray_Guy:
    I’ve heard of people jacking deer (headlights and hunting) but never emu.
    Educational!

    —

    @kerriRaeMillar:
    Llama in the hills of south-central Manitoba.

    (Photo credit Lucas Millar)

    —

    @Jeremycnobel:
    Hit a gopher in head with a foam cup as he came out of his hole.
    Ended with Blue dye foam ?

    @Spray_Guy:
    That’s one way to mark your A-B line. Trying to think of a #caddyshack joke…

    —

    And that’s the thread. So look up from your smart phones occasionally while you’re spraying. It seems there are all kinds of unexpected obstacles in the field.

  • Does Higher Pressure Increase Spray Penetration?

    Does Higher Pressure Increase Spray Penetration?

    A very common question we hear at sprayer demonstrations is:

    “I want to drive the spray deeper into the canopy – does higher pressure help?”

    Well, here’s the classic government answer:

    “…yes and no.”

    It depends on two things. First, the size of the droplet and second, your tolerance for drift (ours is almost zero, BTW). The following video explains how Fine droplets behave very differently than Coarse droplets. It’s always nice to get outside and toss a few balls around:

    Well, that last statement in the video isn’t strictly correct…

    It’s true that changes in pressure have greater impact on the momentum of coarser droplets, but there is some impact on finer droplets, too. Sufficiently high pressure makes for a finer spray quality and finer sprays have been shown to penetrate dense canopies more effectively. We have seen improved canopy penetration in ginseng, field peppers and matted-row strawberry using finer spray under higher pressure. If pressure is high enough, it will create air-inclusion and impart additional momentum to even Fine spray droplets over a short distance, but it’s a case of diminishing return. That is, it takes a lot of pressure to do it and relatively speaking they only got a bit faster/further. In our work, we used pressures between 90 and 300 psi. Excepting hollow cones, that’s generally on the upper end, or beyond a nozzles rated pressure range and it may even be outside the pumps capacity.

    The reason we downplay pressure as a tool for improving canopy penetration is because finer spray under high pressure causes unbelievable drift. A fraction of the spray does get deeper into canopies when you “fog it in”, but the plume of spray blowing beyond the sprayer is entirely unacceptable. Slowing down the travel speed, spraying on cool, humid, low-wind days and lowering boom height can help, but in every trial where we’ve used high pressure and Fine spray quality, we see the image below… or far worse:

    Staged drift in peppers using water
    Staged drift in peppers using water and high pressure combined with Fine spray quality

    The compromise in canopy penetration is to use a Medium spray quality and higher water volume. Stay within the pressure range the nozzle requires to achieve that Medium spray quality. If canopy penetration is still insufficient, consider canopy management (like planting density and pruning) and explore drop-arms to direct the spray, or booms that offer an air-assist or air-deflection option (a few shown here) to entrain and carry spray into the canopy.

    Don’t use higher pressure to increase canopy penetration.

  • The Sprayer Operator – The Most Important Factor in Spraying

    The Sprayer Operator – The Most Important Factor in Spraying

    Spray application is one of the most important activities regularly done in any crop operation. It can also be one of the most expensive and time-consuming. Integrated Pest Management (IPM) is a multi-step process that helps sprayer operators make informed choices about when and what to spray. But, the decision to spray is not the end of the process.

    Spraying highbush blueberry in British Columbia just after a rain. Not ideal, but sometimes the window for application is very small. It’s not the ideal situation, but one strategy for spraying a protectant fungicide on wet leaves is to concentrate the tank mix and use less spray per hectare. The fewer, and more concentrated, spray droplets will dilute in the water already on the leaves and the possibility of run-off is reduced. This is a stop-gap measure, only. The spray will not dry or distribute as it was intended and this strategy will require an additional full-rate application as soon as the weather improves, as long as the label permits. It is often said there is no such thing as a wasted fungicide application.
    Spraying highbush blueberry in British Columbia just after a rain. Not ideal, but sometimes the window for application is very small. It’s not the ideal situation, but one strategy for spraying a protectant fungicide on wet leaves is to concentrate the tank mix and use less spray per hectare. The fewer, and more concentrated, spray droplets will dilute in the water already on the leaves and the possibility of run-off is reduced. This is a stop-gap measure, only. The spray will not dry or distribute as it was intended and this strategy will require an additional full-rate application as soon as the weather improves, as long as the label permits. It is often said there is no such thing as a wasted fungicide application.

    The sprayer operator now faces a lot of decisions about sprayer set-up and application method. These decisions determine if the application will be effective, and they also determine if it will be efficient. Efficient spraying saves money and reduces environmental impact. The goal is to be both effective and efficient.

    So what should the operator be aware of?

    A quick Google search reveals a seemingly endless number of sprayer articles by government, industry and academia (and many on this website!). There are differences in definitions, opinions on priorities vary, and classic sprayer wisdom is sometimes supported and sometimes debunked by current research. But, if you read enough of them you will find more similarities than differences, and common themes will emerge.

    Most agree that the objective of spraying is the safe and timely delivery of an effective, uniform dose of product to a target area. Any product not deposited on the target (e.g. spray drift, sprayer leaks, run-off, etc.) reduces efficiency and is called wastage. The literature points to six broad elements that affect spray efficiency and effectiveness. Sprayer operators should actively consider all six elements before, and during, each spray application.

    The six elements in the illustration overlap because changing one of the elements often means reconsidering others. For example, increasing droplet size to reduce drift potential also reduces the number of droplets sprayed. This may warrant higher spray volumes, which means you might require a more dilute tank-mix to maintain the rate-per-area. Only the sprayer operator’s decisions affect all the elements, which is why it’s pictured in the centre. Technology or technique can not compensate for an inattentive operator; an operator’s skill and willingness to do a good job impacts the overall efficiency and effectiveness of every spray application. Understanding how droplets behave (or misbehave) is essential.

    The six elements of effective and efficient spray application.

    Each element is comprised of many contributing factors. Some of these factors might fit under multiple elements and certainly we’ve reorganized this list many times over the years. No matter how they are presented, all of these factors (and more) contribute to the success of spray applications and they should figure into the operator’s considerations.

    The expanded six elements of effective and efficient spray application.

    So, as sprayer operators, we should all be aware of how the factors that affect an application. Take an active role! Don’t be afraid to get out of the tractor and make changes to your pressure or your nozzle choice. Check your coverage as you spray, and make adjustments as the weather changes. Finally, recognize when it’s a waste of time and spray, and know when to pack it in. The days of “set it and forget it” are no more!