Category: Speciality Sprayers

Main category for all sprayers that are not horizontal booms

Continuous rinsing for airblast sprayers
Why Rinse?
Airblast sprayers are not rinsed as frequently or as diligently as field sprayers. This is primarily because they are not used to spray herbicides, so residue carry-over doesn’t incur an immediately obvious penalty. The typical operator rinses prior to long-term storage or when cross contamination might cause some form of antagonism (e.g. dormant oil followed by Captan or sulfur).
Learn more about the difference between rinsing and cleaning in this article.
Aftermarket Rinsing Systems
Airblast sprayers can be outfitted with rinsing systems that permit operators to rinse quickly, easily, and dispose of dilute rinsate in rotating locations.
A Serial Rinse (SR) system, common on field sprayers, re-purposes the pump to transfer clean water from a saddle tank to the product tank via tank rinse nozzles. The operator introduces a volume of clean water to the remaining volume in the tank, circulates it through the system, and then sprays the rinsate in the crop. Repeating this process three times (i.e. the Triple Rinse) serially dilutes the remainder, resulting in a higher dilution factor than a single high-volume rinse.
A Continuous Rinse (CR) system requires the addition of a dedicated rinse pump. In this case the operator introduces clean water to the tank via tank rinse nozzles while simultaneously spraying. While there is circulation from the bypass (and/or agitation) circuit, the remaining volume is diluted and essentially displaced by clean water.
Objective
Using a fluorescent dye tracer as an analog for pesticide, we wanted to explore the effectiveness and efficiency of both systems. We describe the fluorimetry method in this article. We installed a CR system in a 2,000 L H.S.S. tower sprayer, which unlike most North American airblast sprayers, already features a SR system (150 L clean water tank and two tank rinse nozzles).
Installing a Continuous Rinse System
Installing a CR option required us to address the same three criteria we have already discussed in previous articles on field sprayer installs:
- Identifying a CR pump with sufficient flow to operate the tank rinse nozzles
- Satisfying the electrical or hydraulic requirements of the CR pump
- Matching the supply flow from the CR pump to the demand flow at the booms
The Hol sprayer with an 18-nozzle ducted tower, 150 L clean water tank and two tank rinse nozzles. Inset: Rhodamine WT dye used as a pesticide analog for comparing residue levels.
We mounted two electric Shurflo pumps in parallel to provide flow sufficient to match the typical demand at the booms without excessive electrical load.
Parallel electric Shurflo pumps drew low amperage and provided sufficient flow to the boom.
We found that while the CR flow spun the tank rinse nozzles weakly, the spray didn’t reach all interior surfaces. This was remedied by adding a deflector plate to the bottom of the nozzles to redirect flow.
A brass disc mounted on the tank rinse nozzle deflected spray to all interior surfaces.
We encountered a complication installing CR on an airblast sprayer compared to a field sprayer. Most field sprayers have rate controllers that permit the operator to adjust travel speed or ‘dial in’ a rate to match boom demand to CR pump supply. Unless the airblast sprayer already has this feature, the operator has to calculate in advance how best to match the flows.
The calculation has to be performed for each unique output (e.g. dilute or concentrate nozzle arrangements). The flow from the CR pump is a known constant. The nozzle output is variable according to operating pressure, calculated using a nozzle guide. The operator can adjust pressure (bypass or pressure regulator), PTO-speed (on positive displacement pumps), or even alternate between booms or boom-sections to match the flows.
Matching flow demand to supply using a nozzle catalogue.
In our case, the operator was using 12 blue Albuz hollow cones in their orchard. We knew the CR pump output was 24.25 L/min. So, by setting the pressure to 6.1 bar prior to rinsing, we were spraying about 24.5 L/min. We parked the sprayer and watched to ensure the sump did not fill or drain during CR. Note in the following video how well the two flow rates were balanced (the camera was accidentally turned when we showed the vertical boom).
During trials we noticed that as the sprayer climbed uphill the water level in the tank shifted and the pump drew a little air, causing the nozzles to briefly sputter. This was a welcome sight given reports that introducing a few air bubbles during continuous rinsing can be beneficial.
Field Testing
During testing, we filled the 2,000 L Hol sprayer with 500 L of water and a final concentration of 0.25 ppm rhodamine (0.5 mL dye per 500 L water). The clean water tank was filled to 150 L. We allowed the mix to circulate for two minutes before priming the booms by spraying for a minute. A 50 mL sample was then drawn from the manifold (see below) and later used to represent the starting concentration during the analysis. The sprayer then drove through the orchard, spraying until empty.
Samples were drawn after the tank, before the manifold. Note the telltale Mancozeb coating the sprayer. PPE was worn.
Serial Rinse testing: When the sprayer was empty, the operator left the cab to introduce 75 L of clean water to the main tank via the tank wash nozzles. The rinsate was circulated for one minute before the operator returned to the cab and sprayed the orchard until empty. A 50 mL sample was drawn from the manifold to represent the concentration half-way through the rinse. The process was repeated for the remaining 75 L of clean water and a second 50 ml sample was drawn to represent the final concentration. We did this twice. It took about 12 minutes to rinse the sprayer and the operator had to leave the tractor cab twice.
Continuous Rinse testing: When the sprayer was empty, the operator stopped spraying and engaged the continuous rinse pump. After a few seconds, he continued driving and spraying rinsate. When 75 L had passed through the system, we paused to draw a 50 mL sample from the manifold to represent the concentration half-way through the rinse. The operator continued until the remaining 75 L was sprayed and a second 50 ml sample was drawn to represent the final concentration. We did this twice. It took about 5 minutes, 45 seconds to rinse the sprayer and the operator did not leave the tractor cab.
Sample Analysis: A Turner TD 700 fluorometer was calibrated using samples from the tank. Samples were diluted when necessary to ensure they fell in range of the calibration curve (where there is a linear relationship between the concentration of Rhodamine WT and Raw Fluorescence Units (FSU)). This range spanned a maximum of 0.1 ppm and a detection limit of 0.01 ppm active ingredient. Having previously tested recovery accuracy of 95%, data was adjusted accordingly.
Results of rinsate analysis. n=2.
Observations
While both methods diluted the residue significantly, the remainder following both Serial and Continuous Rinse was much higher than anticipated. This may be an artifact given that both concentrations are potentially below our detection limit, per the following:
Assuming 10 L of residual spray volume left in the system once “empty”, 75 L added would give a dilution factor of 9 (according to the ). While the first 75 L of Continuous Rinse seems to remove more residue than a single addition of 75 L, both are higher than anticipated. A subsequent addition of 75 L should result in a dilution factor of 72. In this case, the remainder would be below our fluorometer’s detection limit, and could explain the results.
Nevertheless, there were positive observations:
- Continuous Rinse resulted in a more dilute rinsate with less water than Serial Rinse.
- Continuous Rinse took less time than Serial Rinse.
- The operator did not leave the tractor cab during Continuous Rinse.
- Potentially, any remaining water from the Continuous Rinse system could be used to operate a spray wand to rinse the sprayer exterior before leaving the crop.
- Both systems encourage improved airblast sprayer sanitation and reduce environmental impact from point source contamination.
Thanks to ProvideAgro for performing the installation, Wilmot Orchards in Ontario for supplying the sprayer and running the trials, and OMAFRA summer student Aidan Morgan for assistance with the data analysis.
June 4, 2019
Air Orientation for Wrap-Around Sprayers
One of the pleasures of working in agricultural extension is when you’re able to help a grower solve a problem. This was one of those happy occasions. An orchardist purchased a Lipco multi-row recycling sprayer and wanted help evaluating their spray coverage.
We worked in 3.7 m (12 foot), mature, high-density Royal Gala trees. The sprayer was driving at 5.0 km/h (3.1 mph), operating at 11 bar (160 psi) using orange Albuz 80 degree air-induction flat fans. This resulted in about 350 L/ha (~37 gpa).
This grower wisely invested in the air-assist option, which produces a vertical plane of somewhat laminar air to entrain the spray and carry it into the centre of the target canopy. Whatever spray blows through the tree should impact the opposing shroud and get recycled back to the tank. All in all, how could you miss?
…we managed to.
Water sensitive papers were placed back-to-back facing each alley (in other words, facing the spray booms). Despite our best efforts, each pass resulted in inconsistent coverage. Papers were replaced in the same location and orientation for each pass and no settings were changed. Nevertheless, sometimes a paper got spray and sometimes it didn’t. What was going on? It was as if the two air streams were interfering with one another – almost cancelling each other out.
Air from tangential (cross-flow) fans oriented perpendicular to the canopy in direct opposition will cancel out. This reduces canopy penetration.
Where possible, do not position laminar air outlets in direct opposition. The convergence creates a high-pressure zone that reduces spray penetration. Some sprayers are designed to avoid this by staggering air outlets one ahead of the other. Laminar flows will deflect unpredictably around this pressurized area and carry droplets back out of the canopy. Unless the canopy is particularly narrow and sparse, turbulent air handling systems do not typically create this problem. In both cases, canopy penetration is improved when fans are staggered and/or are angled slightly forward or backward.
Grey arrows indicate direction of travel. The air outlets of wrap-around sprayers should be symmetrical when viewed from behind. A. Tangential fans in direct opposition: Poor coverage. B. Tangential fans angled forward/backward: Possible vortices and good coverage. C. Tangential fans angled backward: Good coverage, but if the angle is too steep, air will not penetrate the canopy. D. Straight-through axial fans in direct opposition: Good coverage in denser canopies. E. Straight-through axial fans angled slightly backward: Good coverage but limit the angle to prevent the trailing edge of the air wash from missing the canopy entirely. F. Straight-through axial fans angled forward: Slight angles are acceptable, but too much in this image. Wind created by travel speed subtracts from air energy. This creates a risk of reduced coverage and increased operator exposure.
We decided to turn the outer boom/shroud/fan assemblies 10˚ backward by loosening the four bolts at the top of the gantry (see below). This minor change in configuration improved spray coverage significantly. Increasing the angle beyond 10° might have caused the air wash to trail along the canopy face and would have made sprayer turns difficult at the row ends.
We loosened the four clamping screws to adjust the fan angle on the outer boom of this Lipco Recycling Tunnel sprayer.
We replaced the water sensitive papers and ran another pass. The operator later told me he could see the leaves and branches rustling in the row where we made the adjustment, but not in the unadjusted row. The result on water-sensitive paper was dramatic.
Since experiencing this in 2013, I have been told that the Lipco instruction manual advises against air in direct opposition. It was a poorly translated and somewhat obscure sentence buried in the manual, but I concede that it was there. Determine whether your sprayer produces more laminar or more turbulent air, and explore how their relative orientation impacts canopy penetration.
Sometimes, you just have to cross the streams!
May 23, 2019
Exploding Sprayer Myths (ep.10): Airblast Coverage
Here in Episode 10 of Exploding Sprayer Myths we’ve coaxed @Nozzle_Guy back into the orchard. This is part two of a two-part mini series on airblast calibration. In Episode 9 we talked about air settings and travel speed, and now we’re tackling nozzling and coverage.
But here’s the twist: Rather than use spray math to determine the required nozzles to achieve ideal coverage, we do it backwards. This process uses ideal coverage to determine nozzles and finishes with sprayer math.
Confused? Watch the video and this surprisingly simple and versatile approach will become clear. See if you catch the subtle visual joke about “coverage” realize that to pull this off, we had to film it backwards.

Special thanks to the @RealAgriculture team, the Simcoe Research Station and Don Murdoch.
March 4, 2019
The Challenges of Spraying by Drone
Spray application by drone is here. It’s common practice in South East Asia, with a very significant proportion of ag areas now treated that way. Estimates from South Korea, for example, suggest about 30% of their ag area being sprayed by drone. It’s in the US, too. The Yamaha RMax and Fazer helicopters, which pioneered drone spraying in Japan dating back to the mid 1990s, have been approved for use in California since 2015. DJI, the world’s largest drone manufacturer, introduced their ag model, the Agras MG-1, to North America in 2016. Many other spray drones are available or in development.
As William Gibson, the author of Johnny Mnemonic, once said, “The future’s here, it’s just not widely distributed yet.”
DJI Agras MG-1 spray drone (Source: DJI.com)
Proponents of drone spraying cite a drone’s ability to access areas where topography is a problem, such as steep slopes, where productivity of manual application is much lower, or low areas where soil moisture prevents ground vehicles. Operator exposure is reduced compared to handheld application.
Opponents talk about productivity and cost factors compared to manned aerial application, spray drift, and rogue use.
Before drone spraying becomes commonplace, two important things need to happen.
1. Federal laws need to be updated to accommodate the unique features of remotely piloted aircraft systems (RPAS), as they’re now called. Current laws make many assumptions unique to manned ships, and the process to correct that will require some patience. A thorough review for US laws, and their shortcomings, can be found here.
2. Federal pesticide labels need to permit the use of drones for application. As of August, 2021, Canadian labels have no such registered use.
There is no doubt that we need to prepare for a future that includes spraying by drones. Features such as topography adjustment for height consistency and autonomous swath control are already essentially standard, and the capabilities that improve control and safety will continue to develop.
And yet I’ve been nervous about the prospect of pesticide application with drones. My primary concern is around – you guessed it – spray drift. Because a drone payload is relatively small (about 5 to 25 L, depending on the model), application volumes will need to be low to have any sort of productivity. How low? For manned aircraft with a 200 to 600 gallon hopper, 2 to 4 US gpa (18 to 36 L/ha) are the lowest commonplace volumes. The lower volumes require a Medium spray quality (among the finer sprays in modern boom spray practice) to achieve the required coverage.
It’s a simple concept: the less water is used, the smaller the droplets need to be to provide the necessary droplet density on the target. Drift control with coarser sprays requires higher volumes, and true droplet-size-based low-drift spraying can’t really happen at volumes less then, say 5 to 7 US gpa.
At 2 to 4 US gpa, a drone would be able to do perhaps 1 acre per load. While OK for spot spraying, it represents a serious productivity constraint for anything larger. There will be a push toward lower volumes, perhaps 0.5 to 1 gpa (5 to 10 L/ha). The only way these will provide sufficient coverage is with finer sprays, ASABE Fine to Very Fine, with expected problematic effects on off-target movement and evaporation. These fine droplets are also more prone to the aerodynamic eccentricities of aircraft.
Vortices from the rotor can create unpredictable droplet movement (Source: kasetforward.com)
The current regulatory models for aerial drift assessment in North America, AgDISP and AgDRIFT, are not yet able to simulate drone application. But by entering finer sprays into these models for their conventional manned rotary wing aircraft, we can see that buffer zones will be higher. Much higher. And that outcome will give pause to regulators. Failure to control the movement of a spray is, and should be, a problem.
Estimated Buffer Zones (calculated by AgDISP) for a reference rotary wing spray aircraft, using three pesticide toxicologies and two spray qualities.
Furthermore, ultra-low volume (ULV) sprays can change the efficacy of some products, and these will require new performance studies. At this time, regulators are seeking information not just on spray drift, but on product efficacy, operator and bystander exposure, and crop residues.
Regulators are currently collecting spray drift and efficacy data from drones. Since the drones available in today’s market do not conform to a common design standard like fixed or rotary winged manned aircraft, each model may have its own characteristics and need its own study. Some will have rotary atomizers, others will use hollow cone hydraulic sprays. Some will have electrostatic charging, others may propose special adjuvants.
Once data are assessed, there will likely be restrictions in flight height, flight speed, wind speed, spray quality, water volume, perhaps air temperature and relative humidity (or Delta T). This is not new to spraying, as current labels already constrain use for both ground and aerial spray application, more so for aerial.
The obvious question is how these proper application practices can possibly be assured. Operators will need more than just regulatory approval to use a drone, they will require proper training, similar to what a commercial aerial applicator now receives prior to operating a business.
Recall that our aerial applicators are governed by national organizations, the NAAA in the US and the CAAA in Canada. These organizations are in regular contact with federal regulators to assure compliance. They also help fund research into application efficacy and safety. They organize conferences in the off-season and calibration clinics in the growing season. At these, flow rates are confirmed and deposited droplet size is measured. Spray pattern uniformity is assessed and corrected as necessary.
Should drone applications be exempt from these controls? I don’t think that would be wise. Are we ready to implement them? Absolutely not.
These requirements would change the drones’ economic model. And despite these precautions, a drone may still leave the control of a pilot due to unforeseen technical or human events.
In the US, Yamaha does not sell their drone helicopters. Instead, they deploy their own teams to make the applications. This way, they have assurance that only trained and experienced pilots use the technology.
As the industry gears up for the first registrations, we see drone service companies take a leading role in testing. Much is being learned via legal applications of liquid micronutrients, for example, or limited use of pesticides under approved research permits. And I’m pleased to see the recognition of drift management in these efforts through the use of low-drift nozzles. We are off to a promising start.
Requests for drone use are in progress at our regulatory agencies. The outcomes of their risk assessments will provide important initial guidance, and food for thought and discussion. In the meantime, the drone development continues at a rapid pace, with new features and greater capacity at each iteration.
February 18, 2019
How to Calibrate an Airblast Sprayer Operator
Checking coverage on water-sensitive paper with some of the Grape Growers of Ontario members in 2012
Press play to hear the audio version of this article.
When an extension specialist, equipment retailer or consultant is asked to calibrate an airblast sprayer, they would be well advised to calibrate the sprayer operator as well.
Consider this: you and the operator are each investing three hours (average) to optimize the sprayer for a specific set of circumstances: the crop dimensions, density, and the weather conditions at the time of calibration. Depending on the reason for the application, you may even account for the product(s) mode of action and the pest location. This means that once you leave, the circumstances will change and the benefits of your efforts will quickly diminish.
Calibrations, like milk, have an expiry date.
There are three possible outcomes from a single, stand-alone calibration:
1. The operator manages efficacious applications throughout the season because the variability in weather, crop and pest isn’t significant. This is generally not the case.
2. Not recognizing that sprayer settings need constant adjustments (or being unable to make the changes) the operator experiences only modest results and decides calibration isn’t worthwhile.
3. The operator experiences failures and lays the fault with you (as the last person the touch the sprayer) and/or the agrichemical rep that sold the chemical. Few sprayer operators blame timing or spray coverage.
Explaining how to place water-sensitive paper and ribbons in an apple tree
The solution lies in the proverb “Give a man a fish and you feed him for a day; teach a man to fish and you feed him for a lifetime.” It is the sprayer calibrator’s responsibility to involve the sprayer operator and ensure they understand what is being done, why it is being done, and how to do it when you leave. Otherwise, expect to calibrate that sprayer again… soon.
Personally, I have had the most success educating and empowering sprayer operators to make their own seasonal adjustments based on a formulaic approach. Depending what you are trying to accomplish, you may not need all of the following steps, or you may perform some on your own and others as part of the education:
1) You could be working one-on-one, or you may be presenting to a large group. When it’s the latter, I like to arrive the day before to meet the host or owner of the sprayer(s). You can scope out the operation and triage the equipment so you know what parts you might need the next day. It also helps to see the space you will be working in.
2) Perform a pre-calibration inspection of the equipment with the sprayer operator. They know their equipment and can tell you about usage, history and maintenance. It also opens a dialogue between you and helps the operator to relax. Remember: from their perspective they may feel they are being judged and they will take criticisms and corrections personally. Do your best to reassure them that you are trying to make a good thing better – not to correct failings.
3) If you’re working at a large operation, educate the manager (decision maker) and the operators (drivers) at the same time. If you teach the manager, they might not effectively communicate the lessons to their operators. Likewise, if you teach the operators, they may not be able to convince the manager to let them spend money, or time, on making changes to the sprayer program. Get everyone on the same page, at the same time.
4) With the operator, perform a basic maintenance check. Specifically, confirm sprayer ground speed, evaluate pressure gauge accuracy and evaluate nozzles. Explain what you are doing, and ask the operator questions. This is where you learn about their attitude. Are they open-minded about changing how they do things? How has their efficacy been in the past? Will they spring for new parts? Do they need convincing that this process must be repeated regularly?
Demonstrating how deflectors aim air, and spray, into the target using some scrap wood.
5) With the sprayer in the crop, have the operator tie wind-indicator ribbons in the canopy (or better, use lengths pre-tied to springback clips). Explain what they are doing and why. Tell them these ribbons should be monitored, maintained and replaced season-long.
Here’s a tip: If you are working with a large audience, keeping them focused is critical. Growers will take the opportunity to catch up with each other while you are occupied with the sprayer. They are also inclined to wander away to answer cell phones. If they are not focused, you are on a service call and are not really educating. If you feel you are losing control, single out the ringleaders or wayward students and give them jobs, such as holding tools, or placing/removing water sensitive papers. When they have a responsibility, they pay closer attention.
A convenient, weather proof calibration kit for flagging tape, clips and water sensitive paper.
6) Discuss where water-sensitive papers should go, and how they should face. Give the operator a latex glove and after you write on the back of each card (position and trial number) have them clip them in place. Tell them how much they cost, where to buy them and the benefits of using them regularly.
7) Have the operator spray the target crop using their typical set-up (i.e. ground speed, pressure, rate, air settings, etc.) Have attendees and the operator watch the ribbons as the sprayer passes. Spray from one side with both booms on and then stop to discuss results. Then spray from the other side and explore the cumulative impact.
8) The operator will be very surprised to learn they have drenched or missed the papers. They may or may not be surprised to have seen the ribbons stood straight out (indicating too much air). If you like, you can even set up papers in the next alley (or alleys) to show how much spray blew through the target. When the papers are dry enough, collect them and store them somewhere safe for later comparison. They tend to blow away, so stick them to a whiteboard with two-sided tape, or clip them there with paperclips. Explain that they can (potentially) save a lot of money and lost fill-time by improving their efficiency. Get them on-board for the big change to come.
9) Optimize sprayer ground speed, air direction (i.e. deflectors) and air speed/volume (i.e. fan speed). Then re-nozzle the sprayer using brass disc and core tips to reduce output in areas that were drenched or increase output in areas of sparse coverage. Quite often, I turn off the lowest (and sometimes, highest) nozzle positions. A piece of water-sensitive paper at the top and bottom of the canopy will confirm the wisdom in this. Label a new set of papers and have the growers position them in the same locations. Spray again. This entire process should take about 1/2 an hour and is described in detail in the Airblast101 handbook.
Tying flagging tape in trees to indicate prevailing wind and to calibrate airblast air settings.
10) The goal is 85 medium droplets per square centimetre and 10-15% coverage on 80% of the target surfaces for most insecticides and fungicides. If there are still drenches or misses, or if you’ve gone too far in a few positions, correct them and try once more. This is iterative. Make sure the sprayer operator will not be spraying in particularly hot or windy conditions, or your calibration at the top of the target can be compromised. Once you are both satisfied, work out the new sprayer output per area (e.g. US gpa or L/ha). You will have to discuss whether the operator plans to concentrate the tank mix to maintain the labelled “per area” rate (not recommended by me) or will continue to mix the tank as always and simply drive further on it (recommended by me). The later is called “Crop-Adapted Spraying“. Don’t push because it’s their livelihood, and therefore their choice.
11) The final step relies on how well you’ve earned the sprayer operator’s trust throughout this process. Once you have an output and spray distribution that you are both happy with, the operator should invest in molded ceramic tips that emit similar rates to replace the brass disc-core. Then, they must be willing to repeat the process on any crops that are significantly different to ensure they have the right settings. Sometimes only modest changes are required between blocks. Perhaps they will dedicate certain sprayers to certain blocks to reduce the number of changes required. In either case, they will have to revisit these settings as the season progresses to compensate for denser and/or larger canopies.
A few examples
The following figures illustrate three airblast calibrations in Ontario apple orchards from spring 2014. Some required one attempt; others required a few trial settings before we achieved reasonable coverage. In all three cases, the sprayer operators reduced per-area rates, bought new nozzles and planned to buy water-sensitive paper. Further, they indicated they would continue to monitor ribbons (as long as they could be seen) and would review coverage after petal-fall.
Several nozzles shut off, spray re-distributed. Targets still drenched in two locations with a 24% savings in spray mix.
Three successive re-calibrations were required. Output was reduced in the first trial, but poor coverage in position 3. Top nozzles turned off and spray re-distributed in trial 2, but a gust of wind reduced coverage at the top of the tree. Bottom nozzles turned off and spray redistributed to top nozzles for a 40% savings in spray mix.
Output reduced in all nozzle positions and sprayer fan speed reduced. The high humidity greatly reduced droplet evaporation and increased the spread on the papers. In this case, it was decided not to reduce output any further to account for anticipated growth and the high humidity. There was a 27% savings in spray mix.
Conclusion
So, the next time you calibrate an airblast sprayer, be sure to teach the sprayer operator (and audience) what you are doing and why. Involve and engage them. Answer their questions. Encourage them to perform the same calibration for each significantly different block and make mid-season changes. With luck they will only call back to report success and savings, and not to condemn your efforts, or worse: to ask you to re-calibrate their sprayer!
January 24, 2019