Category: Boom Sprayers

Main category for sprayers with horizontal booms

  • 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.

  • Exploding Sprayer Myths (ep.7): Boom Height

    Exploding Sprayer Myths (ep.7): Boom Height

    It’s a new season of Exploding Sprayer Myths so we’ve got a new opening sequence!

    In this episode we demonstrate the importance of nozzle spacing, spray angle and boom height. We also turn a hapless pineapple into a projectile and spray dyed antifreeze on a cold winter day.

    Learn more about how boom height affects spray deposit uniformity, and why that should concern you, by going here.

    This episode was filmed on location at the Syngenta Honeywood Research Facility in Plattsville, Ontario. We thank them for generously allowing us to commandeer their facility and staff for the day.

    And of course, none of this would be possible without the talented staff at Real Agriculture. Make sure you tune into RealAg radio.

    A little extra fun:

    We received this email after a grower heard Tom speak at a meeting. A compelling observation about how nozzle spacing and drift affects men everywhere:

    Tom: I really enjoyed your talk in Humboldt yesterday. During the coffee break immediately after, I went to the washroom and noticed 3 guys spread evenly across 5 urinals. Wow. Talk about worrying about spray drift. When I returned to my table and told my wife of my findings, she commented that it must have something to do about the distance to the target, as it couldn’t possibly be that the pressure was too high!

  • 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.

  • Spray Drift – Why is it still happening?

    Spray Drift – Why is it still happening?

    Despite the abundance of information available on spray drift, we continue to see widespread incidents of damage to a variety of crops every year. Do applicators just not care or are they missing some vital information when making decisions to spray? I believe it is the latter.

    What is the problem?

    In my experience, the vast majority of spray drift cases (probably 90% or more) are the result of ‘inversion drift’. That means the drift has not come from an adjacent sprayed area, it has come from one or more sources that are some distance from the site of damage. The distance between the sprayed site and the location of the damage may vary dramatically, from a few kilometres to tens of kilometres.

    Why is there so much inversion drift when labels specifically prohibit use of the products under surface temperature inversions? Many may argue that it is a blatant disregard of the label by a few applicators (translation = cowboy operators). I do not agree this is the main problem. While I can confirm the existence of ‘cowboy operators’, thankfully they are limited in number. I believe the problem is a lack of understanding about how to tell when there is an inversion and particularly not knowing how ‘day wind’ moves differently to ‘inversion wind’. I continue to see good farmers/applicators doing what they believe to be the right thing but it is not. These are people very concerned about minimizing spray drift; they honestly do not think they are doing anything wrong.

    What is ‘day wind’?

    After sunrise, the sun begins to heat the ground, the warm ground then heats the air close to the surface, and this air then rises. As that warm air rises, cold air from above sinks down to replace it. The ground then warms this cold air and it rises. This cycling of warm air rising and cold air sinking creates turbulence and then wind. This is a good thing; turbulent wind movement is much safer for spraying. ‘Day wind’ has a turbulent motion and is much more likely to pull any fine droplets to the ground within a reasonable distance. During the day, we can predict which direction and how far our fine droplets will travel.

    What is ‘inversion wind’?

    As the sun sets, the ground begins to cool quickly and this in turn cools the air next to the ground. As we all know, cold air does not rise and warm air does not sink. This means there is a layer of cold air trapped close to the surface and a layer of warm air above it. The result is no turbulent movement or mixing of the air. The air may become quite still and this is often observed around sunset when the daytime wind ceases or drops off. What happens next is where the real danger occurs for spraying.

    As the night progresses and the ground cools more, the cool air close to the surface becomes colder and therefore more dense, particularly from midnight onwards. This cold dense air then begins to move across the landscape, often down slope and in very unpredictable directions. Remember this air is not turbulent, there is no mixing, it has layers of air, something like layers in plywood, and it flows parallel to the ground. Any fine droplets released into these layers of cold non-turbulent air will simply move sideways across the surface until the sun rises and heats the ground again. This is when the fine droplets are released from the layers and they come to ground, often in the lower parts of the catchment and a long way from the site of application. It is impossible to predict what direction this ‘inversion wind’ will go. For this reason, spraying in this type of wind is extremely high risk for spray drift.

    Key indicators that and inversion is unlikely

    • We should always expect that a surface temperature inversion has formed at sunset and will persist until sometime after sunrise unless we have one or more of the following: continuous overcast weather, with low and heavy cloud;
    • continuous rain;
    • wind speed remains consistently above 11km/h for the whole time between sunset and sunrise;
    • and after a clear night, cumulus clouds begin to form.

     Inversion wind movement – practical demonstration video

    Wind is a key factor in any spray application. The problem is that not all wind is the same. To reduce the incidence of spray drift, it is critical that spray applicators understand how wind moves, particularly during a surface temperature inversion. This video uses smoke flares to visually demonstrate the air movement under inversion conditions.

    Here’s what we’re looking for: moderate wind with consistent direction that disperses spray and drives it to ground.

    Conclusion

    Many factors affect the potential for spray to drift but the main ones are; the weather conditions at the time of application, nozzle selection, products/tank mix used, actual spray quality achieved, speed of rig, and boom height. The common denominator is that all of these things are within the control of the spray operator.

    Spraying under inversion conditions is extremely high risk and prohibited on many product labels, that means it is illegal. If you are serious about preventing drift, then you must learn how to identify when an inversion is likely to be present and more importantly when it has broken.

    All agricultural chemicals have the potential to drift; it is how we use them that increases or decreases that potential. Therefore, the problem is a human one, not a chemical one. There is a suite of information available but if you are still unsure or need any assistance, please seek advice from an expert. Maintaining long-term access to key products depends on us reducing spray drift.

  • How to Properly Set Up a Crop Sprayer

    How to Properly Set Up a Crop Sprayer

    Article reprinted with kind permission from an original article written by Oliver Hill in the February, 2017 edition of Farmers Weekly. Photos ©Kathy Horniblow.

    Crop spraying is one of the most important and highly skilled jobs undertaken on any arable farm, but it is facing increased public scrutiny. This is why it is vital that the kit you use as a means to apply pesticide to crops is in prime working order and is set up correctly to deliver the product safely and accurately to its target. Optimum sprayer set up will help to maximize the efficacy of applied products, reduce spray drift and keep machinery in good condition.

    For this best practice guide to sprayer set up, Farmers Weekly teamed up with former Farm Sprayer Operator of the Year Iain Robertson. Mr. Robertson is assistant arable farm manager at David Foot Ltd, a 2,200ha mixed farm south of Dorchester in Dorset, growing wheat, barley, beans, oilseed rape and maize as forage for the farm’s three dairy herds. The machine used for this guide is a Bateman RB26 self-propelled sprayer and while most of these checks and tests are universally applicable to all sprayers, it is also important to refer to the handbook of the manufacturer of your specific machine.

    Watch the video tutorial with Mr. Robertson and then see the step-by-step guide below for more detail.

    Pre Start Checks

    Before firing up the engine, the first thing to do is your pre-start checks – that means checking your machine’s vital fluids like fuel, hydraulic oil, hydrostatic oil, engine oil and coolant levels. If yours is a self-propelled sprayer, chances are you’ll need to get up on to the back of the machine to check some of these.

    “While I’m up on the back of the sprayer I also have a quick look in the top of the tank to make sure that it is nice and clean and the tank rinse nozzles have worked properly – cleanliness is next to godliness,” says Mr. Robertson. Next, move on to the tires. Use a pressure gauge to check all tires are at the correct pressure and refer to the manufacturer’s guidelines. If you’ve got a trailed sprayer, don’t forget to check the tractor tire pressures as well.

    Aim for tires to be run at the lowest pressure recommended for the load to be carried. This will help with boom height and stability and also helps tires act like a shock absorber to ride out bumps. If using a trailed sprayer, use a spirit level to ensure that the drawbar is level. Mr. Robertson says he tries to work around the machine in a methodical, clockwise manner to ensure that he doesn’t miss anything.

    Coming to the pumps, check that they have got enough oil, check that any tool boxes have enough spare parts and any equipment needed and make sure you are carrying a spill kit with absorbent granules and a spade in case the worst happens and there is a spillage. Make sure all parts are lubricated daily and that any grease nipples are cleaned before and after use to avoid them collecting dirt and blocking.

    Check all hydraulic hoses, spray lines and air lines for any signs of wear that could result in problems while operating.

    It’s best to run the sprayer at a minimum of 5 bar to check for leaks. Also check the spray tank is fixed down securely, all straps and bolts are tight.

    Boom checks

    Once opened out, check the boom has good movement in the x- and y-axis. All machines are different so check with your manufacturer as to how the boom is set up. Mr Robertson’s Bateman has tie rods and stock bots that can be adjusted to set the boom up to ride well.

    Check the tie rod nearest the back of the machine is slightly loose when moving and that the front rod is tight. Next, check for up and down movement by gently pushing the boom down by about 50cm and letting go. The boom should return to the central position without too much bouncing around.

    “We want a little bit of movement but not excessive so that you can ride over the bumps as you go along without over- and under-dosing the crop,” says Mr. Robertson. Boom height is one of the most critical factors when spraying and the ideal height is 50cm above the crop. One of the easiest ways to work this out is by using a cable tie that is cut off at the correct length to use a visual aid from the sprayer cab.

    Don’t forget to measure from the tip of the nozzle to the crop, not the spray line.

    Good sprayer cleanliness is important, so make sure the system is rinsed through at the end of each day with clean water to make sure there’s no residue left in the boom. If your machine’s boom doesn’t have recirculation, remember to take the end caps off occasionally and flush out the whole boom.

    Nozzle checks

    Check that the nozzles are aligned both vertically and horizontally, according to the NSTS guidelines. Loosen clamps to adjust any nozzles that need realignment.

    Check the nozzle output at least twice a year by running the sprayer with clean water at 3 bar pressure. Time the output of each nozzle for 30 seconds. If nozzles have been used previously, it’s best to check their output against that of a new pair. Mr Robertson advises using a measuring cylinder rather than a jug to measure the flow rate as a jug is less accurate “because you get a bigger variation over the wider surface area”.

    With an 03 nozzle running for one minute at 3 bar pressure, the output should be 1.2 litres/minute as a rule of thumb but refer to the nozzle manufacturer’s output chart for the expected flow rate. “An easy way to remember this is: at 3 bar your nozzle size multiplied by four will give you your target litres/minute output. It works for all nozzle sizes.” If the output varies more than 4% of the average, or if the spray pattern visually doesn’t look correct, you need to change the nozzle set.

    After checking the output, cross-reference this figure with the rate controller – you may need to adjust the flow figures to ensure that the two correlate. If a nozzle becomes blocked while spraying, Mr. Robertson says he will swap it for a new one and then clean it later using a toothbrush or airline. Never blow through a nozzle with your mouth.

    Nozzle choice

    The choice of nozzle is highly dependent on the sort of job you’re doing. “Timing is crucial but using the right nozzle at the right time will make the job so much easier, cut drift and mean that you’re getting more of the product where you want it to go. If you aim at it you will hit it,” says Mr. Robertson.

    His nozzle of choice is an 03 size and he prefers to use the Defy 3D nozzle alternated forwards and backwards across the boom for pre-emergence work and T0 applications as well as the T3 ear spray. “In less than optimum conditions I may prefer to use the Amistar/Guardian Air, a fine induction nozzle. I would use this at T1 and T2 and also in sub-optimum conditions.”  This nozzle has a 3-star Local Environmental Risk Assessment for Pesticides (LERAP) rating and is 75% drift reducing.

    A water volume of 100 litres/ha is a good rate for spring fungicide application. It provides enough coverage for good disease control and allows maximum efficiency from the sprayer.

    Forward speed

    The third and final part of reducing spray drift is forward speed. Depending on nozzle size and water volume, aim to travel at 12kph.

    Mr Robertson says he finds that this speed gives a good overall output and means you don’t get shadowing or turbulence behind the machine.

    Tips and tricks

    One of the biggest risk of contamination is at fill up. “A fantastic, cheap trick that I learned through Farm Sprayer Operator of the Year is to take a 200 litre plastic drum and cut it in half to create two drip trays to catch any spillages under the induction hopper and the tank overfill.” This eliminates point source contamination, he says.

    “Finally, there’s a plethora of information out there on the internet, loads of good apps to download. The technology is there to help us do the best job possible and make our job as safe as possible.”