Author: Jason and Tom

  • Air-Assisted Boom Sprayers

    Air-Assisted Boom Sprayers

    Air-assisted boom sprayers have been around since the 70s. More common in Europe than North America, they have demonstrated value in mitigating drift and improving canopy penetration. The majority of air-assist systems are found on three-point-hitch or trailed sprayers, which is fine (and perhaps even preferable) as long as clearance, travel speed and acreage aren’t limiting factors. In North America, trailed air-assist sprayers are used by some vegetable and strawberry growers, but air-assist in general is rare among field croppers. There are a few possible reasons for this:

    • North American field croppers are predominantly concerned with work rate and prefer the larger, faster, self-propelled option.
    • Air-assist is not ideal for herbicide applications to bare soil because unless it’s perfectly adjusted, it tends to bounce spray off the ground. A canopy is preferred to capture the spray and exhaust the air energy. This reduces the overall utility of air-assist.
    • The air-assist feature is expensive and growers are either unaware or unconvinced of its value.
    • There are few, if any, after-market air-assist upgrade kits available. This is because installations are bespoke; The apparatus is heavy, adds load to existing electrical and hydraulic systems and can interfere with boom folding. So, getting air-assist means purchasing a new (and perhaps unfamiliar) brand of self-propelled sprayer… and there aren’t many on offer.
    Figure 1 – Dammann’s massive three-axel DT3200H S4 self-propelled air-assist sprayer at Canada’s Outdoor Farm Show in 2018.
    Figure 2 – Agrifac’s AirFlowPlus (Image from Agrifac website)
    Figure 3 – Agrifac’s AirFlowPlus depicting adjustable angle (Image from Agrifac website)
    Figure 4 – This photo of a John Deere with air-assist was taken at a dealer’s lot in Southwestern Ontario in 2014. We have no idea what the history is, or who added the air-assist feature (it looks similar to a Miller Spray-Air with two blowers).

    Air assist booms came to Western Canada in the early 1980s in the form of the “Spray-Foil” sprayer, later renamed Spray-Air. This sprayer was developed and manufactured in Carseland, Alberta. It used a shear-atomizer nozzle, a “foil”, that required a strong airblast to properly atomize a liquid feed that was introduced on the foil’s leading edge. As a result, it created a powerful airblast and a very fine spray. It was marketed as a way to reduce herbicide rates, an attractive feature during the times of drought, high interest rates, low commodity prices, and general economic malaise of farming on the prairies during the 1980s. Neighbours of Spray-Foils didn’t like the drift potential of the machines, and chemical companies objected to the claims of reduced water volumes (2 gpa) and lower product rates which contravened label directions. An unflattering test report of the sprayer by PAMI in Lethbridge resulted in a protracted lawsuit which helped cast the fate of the company. A Danish company licensed the design and sold it in Europe under the name Danfoil, where it continues to exist and @Nozzle_Guy saw it in person during the 2019 Agritechnica.

    Figure 5 – A Spray-Air Trident pull-type made in Carseland, Alberta, for sale.

    Eventually, Spray-Air rose from litigation and developed an improved nozzle with the assistance of the National Research Council (the “Shear Guard”) and introduced the Trident boom which gave users the option of atomizing spray with a conventional boom with or without air assistance, in addition the the native choice of shear-atomization. The sprayer chassis itself also continued to improve with a better overall design. Nonetheless, it was sold to Miller in the 2000s after a period of sales stagnation.

    Figure 6 – A trailed one-sided Kyndestoft Air-Sprayer in Ontario field tomatoes (c. 2010)
    Figure 7 – Everyone’s favourite sprayer, the Spra-Coupe, sporting a Kyndestoft Air-Spray system (1996, PAMI)
    Figure 8 – An innovative prototype out of Alberta, the “Kaletsch fan sprayer” used pulleys to power the fans (1996, PAMI)

    A fundamental problem with shear-atomization on sprayers like the Spray-Air is the requirement for significant air velocity for the atomization to occur properly. When the canopy cannot absorb that energy, air rebounds and creates drift. And if the operator cannot reduce the airblast strength without adversely affecting atomization, it leads to problems.

    This photo (Figure 9) was submitted by Mr. L. Jones, a cash-cropper in ND, USA. It’s his JD4710 (circa 2004), which has 100′ booms and an 800 gallon tank. What’s interesting is that it has a Miller’s Spray-Air. This air-assist system is available on Miller’s Nitro and Condor line as well as New Holland sprayers (which are built by Miller). @spray_guy did some work with it on a Condor in field corn. It comes with their dual-flow nozzle system (Shear Guard™ PLUS Air Nozzles plus Dial-A-Drop™) for fungicides (applied at low volume) but you can also use conventional tips for coarser herbicide work.

    Figure 9 – A JD4710 with Miller’s Spray-Air and conventional nozzles.

    Mr. Jones says they use the flat fans when spraying a soil-applied herbicide. If it’s moderately windy, they engage the air to reduce drift. When they apply fungicide on wheat they use only enough air to move the heads as they pass over. Bystanders can see the spray enter the canopy and a portion rebounds, which they suggest (and hope) provides some underside coverage. That’s possible, but it’s generally better to keep all the spray in the canopy. This can be achieved by further reducing air speed, increasing travel speed, and/or aiming the air slightly backwards to increase the cross-sectional distance the spray has to travel and slow the spray velocity relative to the sprayer speed.

    Generally, we’re proponents of using air when spraying. It opens the crop canopy, exposes otherwise-hidden surfaces, entrains and carries droplets to the target (reducing drift and improving coverage) and it extends the spray window by out-competing moderate winds. We have no proof, but wonder if it might also help alleviate the negative impact of tire and chassis turbulence on coverage uniformity under the boom. And, before you feel we’ve ignored a big benefit, we’d would be very cautious about using air-assist as a means for reducing carrier volume. The debate about finer sprays at less volume giving greater efficacy continues. While true at times, any benefit needs to be balanced with the downsides of potentially more drift and evaporation.

    Here’s some 2018 footage from an assessment of canopy penetration in field pea using a Miller Nitro with Spray-Air. We see coverage extends deeply into the canopy, the degree of which shares an inverse relationship with depth (fairly classic). Note the heterogeneous mix of smaller and larger deposits from the air-shear nozzles. While some heterogeneity is good, this extreme span represents waste. The product tied up in the largest droplets could have been more gainfully employed as several smaller droplets. This pattern may be the result of using insufficient air energy, preventing the air-shear nozzle from fully atomizing the spray liquid.

    In 2015 we felt air-assist needed some exposure, so we held a demonstration at Canada’s Outdoor Farm Show. Over three days we used water-sensitive paper to evaluate coverage in a soybean canopy (moderately dense, planted on seven inch centres) from a Hardi Commander (Figure 10) with and without air-assistance. We originally wanted to get our hands on a self-propelled Hardi Alpha Evo (Figure 11), but there were only two in North America at the time and neither were available. By the way, the Alpha Evo is now on the third iteration, but still uses the Twin Force air-assist system which allows the operator to change the angle of the air and the air speed. Each blower can be steplessly adjusted to a maximum output of 2,000 m³/h per m of boom and a maximum (and we’d wager, often excessive) air speed of 35 m/sec. You can watch a video explaining how to dial-in a Twin Force sprayer here.

    Hardi Commander (118 foot boom) with TWIN air-assist
    Figure 10 – The Hardi Commander (118 foot boom) with Twin Force air-assist used in a spray demo at Canada’s Outdoor Farm Show.
    Figure 11 – Hardi’s Alpha Evo self-propelled sprayer employs their their Twin Force air-assist system.
    Figure 12 – Looking up from under the Hardi Alpha Evo boom. Air angle and speed can be adjusted.

    The demo treatments

    The sprayer was calibrated for 93.5 L/ha (10 gpa) at 2.75 bar (40 psi) at 9.7 km/h (6 mph). The boom was suspended 50 cm (20 inches) above the top of the canopy. On one side of the boom, we ran yellow mini drift nozzles (MD 11002’s) to create a Coarse spray quality, and on the other side we ran conventional yellow flat fans (F 11002’s) to produce a Fine spray quality.

    Water-sensitive paper was attached to rods at three canopy depths: at the top, midway down and at the bottom of the canopy. Papers were oriented both face-up and face-down (Figure 13). Following each application, papers were collected for digital analysis using “DepositScan” which calculates the percent surface coverage and the deposit density. Both of these factors contribute to overall coverage.

    We collected papers from three treatments:

    1. Fine spray quality, No air assist
    2. Coarse spray quality, No air assist
    3. Fine spray quality, Air assist
    Figure 2 - Water-sensitive papers were placed at three levels in a dense soybean canopy, facing up and down, for three conditions. Condition 1 - Air off, conventional 11002’s (medium-fine spray quality). Condition 2 - Air off, mini drift AI11002’s (very coarse spray quality). Condition 3 - Air on, conventional 11002’s (medium-fine spray quality).
    Figure 13 – Water-sensitive papers were placed at three levels in a dense soybean canopy, facing up and down, for three treatments. Treatment 1 (Fine spray quality, No air assist). Treatment 2 (Coarse spray quality, No air assist). Treatment 3 (Fine spray quality, Air assist).

    We held two demos per day at noon and 3:00 pm for three days, giving us six sets of papers to analyze for each treatment. The weather ranged from 25-29°C, 30-58% relative humidity and winds of variable direction from 3-11 km/h.

    This was a simple randomized complete block design, but it was not a rigorous experiment. We simply took the opportunity to gather numbers from the demonstration. A more fulsome experiment would require many, many more passes under more stable conditions. For example, we set the angle of the air and nozzles to about 30° forward and the air speed at maximum, which wasn’t necessarily correct. Ideally, these settings should have been fine-tuned to match the forward speed of the sprayer, the density of the crop and the weather conditions. There was a lot of boom sway (watch the video below).

    And so, caveats aside, the following graph illustrates the mean percent coverage and mean deposit density for papers in each treatment, for papers that were facing up (Figure 14). Standard error of the mean is presented alongside the average (x% ± y).

    Results

    Figure 3 – Average percent coverage (red) and droplet density (blue) for upward-facing water-sensitive papers in three canopy depths for each of three conditions. Averages rounded to the nearest 0.5 and Standard Error is indicated. * indicates significance with 95% confidence.
    Figure 14 – Average percent coverage (red) and deposit density (blue) for upward-facing water-sensitive papers in three canopy depths for each of three treatments. Averages rounded to the nearest 0.5 +/- standard error. “*” indicates significance with 95% confidence. Condition 1: Fine, No Air. Condition 2: Coarse, No Air. Condition 3: Fine, Air Assist.

    Treatment 1 (Fine, No Air) reflects a typical coverage pattern for a dense canopy. Coverage declines as a function of canopy depth because spray droplets are intercepted by plant material before they reach the ground. This is particularly evident with broadleaf canopies that create shading. The coverage data doesn’t show it, but there was an obvious (and unacceptable) plume of spray drift during these applications (see Figure 15).

    Figure 4 – The effect of air-assist on downwind drift from a medium-fine spray quality. Note that the nozzles and air are directed 30° forward. When sprayed over bare ground, the air-assist bounces spray back up, as pictured here. However, when sprayed into a canopy with the correct air settings, bounce (and drift) is virtually eliminated.
    Figure 15 – The effect of air-assist on downwind drift from a Medium-Fine spray quality. Note that the nozzles and air are directed 30° forward. When sprayed over relatively bare ground, the air-assist bounces spray back up, as pictured here. However, when sprayed into a canopy with the correct air settings, bounce is virtually eliminated.

    Treatment 2 (Coarse, No Air) follows the same coverage trend as Treatment 1. This treatment represents much larger, and fewer, droplets than Treatment 1, and yet the only obvious difference is reduced coverage in the middle of the canopy. There was little or no plume of spray drift during these applications.

    Treatment 3 (Fine, Air) also followed the trend of reduced coverage as a function of canopy depth. Mean coverage was higher at the top of the canopy compared to the other two treatments. In fact, according to an ANOVA, deposit density was significantly higher in this canopy position than the other treatments, with 95% confidence. While mean coverage in the middle of the canopy was more than 2x that of Treatment 2, it was not statistically significant. There was no apparent difference at the bottom of the canopy. It is important to note that unlike Treatment 1, there was little or no spray drift plume during these applications.

    Figure 5 – Upward-facing water-sensitive paper from mid-way into the canopy (position B) for condition 2 (very coarse droplets, air off) and condition 3 (medium-fine droplets, air on). The difference in coverage is obvious.
    Figure 16 – Upward-facing water-sensitive paper from mid-way into the canopy (position B) for Treatment 2 (Coarse spray quality, no air assist) and Treatment 3 (fine spray quality, Air assist). The difference in coverage is obvious.

    DepositScan was unable to detect coverage on any of the downward-facing papers. However, close visual inspection did reveal differences. Unsurprisingly, Treatment 2 (Coarse, No air)  did not produce any underside coverage; Large droplets do not change direction mid-flight unless acted upon by some other force. Droplets can bounce and shatter, but that did not occur here. The Medium-Fine droplets created in Treatment 1 (Fine, No Air) and Treatment 3 (Fine, Air) did leave trace coverage on the downward-facing surfaces. Generally no more than 10-30 deposits on the entire 1 x 3″ surface, representing less than 1% total surface coverage. It could not be determined if the air used in Treatment 3 improved underside coverage over that of Treatment 1.

    Did air-assist make a difference?

    Let’s start with the literature. Many experiments in peer-reviewed journals show that it does. A perfunctory literature review reveals improved coverage in the middle and lower portions of cotton, potato, soybean and wheat canopies. Some of these experiments were based on coverage using fluorescent dyes, and some with water-sensitive paper. Others were based on efficacy and report improved crop protection. The actual implementation was highly variable with some authors recommending angling the air and nozzles forward 20-25°. Others proposed 30° backwards. Most agreed (as do I) that the air speed should be set relative to the canopy density where higher speeds improved coverage deeper in the canopy, but did so at the expense of coverage in the higher canopy. Picture a bell curve on it’s side where the Y axis is canopy depth and the X axis is coverage; More air shifts the peak of the curve down the Y axis, into the canopy.

    As for our demonstration, some interpretation is required. If an operator is spraying a contact product with limited or no translocative properties, then coverage becomes especially important. In order to improve coverage, higher volumes and finer droplets combined with slower travel speeds are often advised. This may be impractical, as most operators prefer to use less water and drive faster.

    When we used Medium-Fine droplets with no air assist, coverage was good (Figure 14) and better than coverage obtained using Very Coarse droplets. However, spray drift was unacceptable (Figure 15). When air-assist was engaged, we reaped the coverage advantage of smaller droplets and drift reduction as good or better than what we saw with coarser droplets. Unexpectedly, we did not see an obvious improvement in coverage from the air assist. This begs the question “If the spray didn’t drift, where did it go?” This demo was a far cry from a formal mass accounting exercise, but my guess is it wasn’t effectively captured by our collectors and that a hefty fraction ended up on the ground. We would expect more uniform coverage under the boom, and some improvement in canopy penetration, but our ad hoc experiment wasn’t sophisticated enough to reveal it.

    In the end, we feel there are advantages to the air-assist mechanism. The ability to employ a finer spray quality when required, while greatly reducing spray drift and combating inclement weather to extend the spray window are appealing features. Research has clearly demonstrated that deep-canopy spray coverage and overall efficacy are improved when this system is properly adjusted to match spray conditions. We’re not comfortable with suggesting it warrants lower carrier volumes (i.e. not dose) because of the expertise required to adjust the system. However, to be fair, experienced operators have accomplished it

    We hope to see more air-assist options on boom sprayers.

  • The Label Summary Sheet Proposal

    The Label Summary Sheet Proposal

    We’ve identified and discussed shortcomings in the content and design of today’s pesticide labels in an earlier article. From the perspective of the spray applicator, the information needed most often can be difficult to locate, anachronistic, contradictory, subjective or even missing from the label altogether. To truly encourage an applicator to read and follow the label we need a consistent, concise and clear format that summarizes critical content.

    To that end, we have worked with growers, university/government extension and industry to develop a prototype we’re calling the “Label Summary Sheet”, or LSS for short. We presented the concept in a series of public presentations in western Canada as part of the RealAgriculture TechTour Live event in 2018. You can watch a recording of part of that event at the end of this article.

    The LSS does not replace or interpret the current label, which is a legal document. It is a summary intended to accompany it. At this stage the LSS is simply a proposal. These documents are not intended for use right now; we hope they will grow and change for the better as they stimulate discussion.

    Consider this metaphor: You have just purchased a laptop. When you unbox it, you get an in-depth instruction guide that covers everything from operation to trouble shooting and includes all the legal riders. It’s a daunting technical document that you likely won’t read unless something goes wrong. Knowing that, manufacturers include a graphic and accessible quick start-up guide that summarizes the most common and critical issues. It doesn’t replace the instruction manual, it just augments it. If you can’t find what you need in the quick start-up guide, you are referred to the more fulsome description in the instruction manual. Think of the pesticide label as the instruction manual and the LSS as the quick start-up guide.

    Some agrichemcial companies recognize this need and have developed short documents to summarize key aspects of the label, but they are inconsistent and brand-specific marketing documents that do not always contain the information we are proposing. Here, for example, is the technology sheet for Integrity herbicide.

    We tested the versatility of our LSS format by summarizing four diverse pesticide labels. Our selections are not intended to imply that these labels are particularly deficient. Only that they are commonly used, somewhat complicated and represent the spectrum of pesticide categories and application methods.

    Download and look at the variety of labels we have summarized as examples. They are available here:

    • Pristine (LSS: 3 pages. Pesticide Label: 25 pages)
    • Dual II Magnum (LSS: 3 pages. Pesticide Label: 38 pages)
    • Liberty 150 (LSS: 2 pages. Pesticide Label 20 pages)
    • Traxos (LSS: 2 pages. Pesticide Label: 12 pages)

    Note that each LSS features the same section headings and a relatively consistent layout, no matter the manufacturer. Generic icons are used to illustrate content and make it easier for users to navigate without language barriers. The LSS are black and white to facilitate reproduction and refer back to their respective pesticide labels (i.e. the online PDF, not the booklets that come with the pesticides).

    LSS Sections

    Here is the Pristine LSS broken down by section to highlight the key features.

    1. Banner Section

    The banner is at the top of every LSS. It gives the commercial product name and the date to ensure the LSS reflects the current pesticide label. Four icons represent the most common application technologies: Horizontal boom sprayer, airblast, aerial and handheld. If an application method is prohibited, a banned symbol appears (such as aerial in this case). Note we have left room for RPAAS (UAV’s) anticipating the day we have products registered for that technology. The table notes the type of pesticide (e.g. fungicide, insecticide, adjuvant, etc.). The mode of action and active ingredient(s) are noted, as well as the formulation and the Pest Control Product number.

    2. Resistance Management / Planting Restrictions

    Intended to provide key information on managing pesticide resistance, this section reflects label content about carry over and the rotation of active ingredients. Further, to aid in application decisions, it reflects any restrictions around maximum number of applications, sequential applications or plant back issues following use.

    3. Environmental Conditions


    Any restrictions regarding weather conditions during or after application are noted here. This includes set-backs or buffer zones that reflect method of application and the nature of the adjacent or downwind area in question.

    4. Sprayer Settings

    This section includes the six most commonly asked questions an applicator has when calibrating or adjusting their sprayer prior to use. It is organized by target crop and method of application. When the label provides a high level of detail, the user is referred to the correct page. Note the use of graphics to quickly direct the reader to the information they need. Any additional qualifications found in the label relating to sprayer settings are indicated in the notes beneath the table.

    5. Handling Safety (PPE)

    The concept for this simple and graphic table originated in France, and was communicated to us by Dr. Carol Black of Washington State University. This unambiguous  format encourages the use of PPE while ensuring the handler uses the appropriate level of protection for each activity.

    6. Mixing


    As operators tank mix more products to curtail resistance, improve efficacy or improve productivity, there is a greater chance of chemical or physical incompatibility. This section summarizes any restrictions noted in the label. Learn more by downloading Purdue Universities’ publication “Avoid Tank Mixing Errors“.

    7. Rates and Restricted Entry Intervals

    This table can be quite complicated depending on the pesticide label. It summarizes the rates, volumes and restricted entry intervals by crop. It reflects the broadest range of product rates listed in the label. Restricted entry duration is affected by the post application activity, and this is captured in the REI column. If more detail is required, the user is referred to the appropriate page(s) of the label. Any additional qualifications found in the label relating to rates, volumes or REI are indicated in the notes beneath the table.

    8. Equipment Cleanout

    Finally, equipment cleanout is summarized (where possible) in a sequence of steps. When the pesticide label is silent on the cleanout procedure, the user is provided with the triple rinse protocol, which is generally held to be the industry best-practice.

    Adoption

    To date, this proposal has been made to Croplife Canada, the American Society of Agricultural and Biological Engineers (ASABE), an International Organization for Standardization (ISO) mirror committee (Equipment for crop protection) and more than 1,400 growers and stakeholders across Canada.

    Our suggestion for adoption of the LSS (in its current form or something similar)  is that regulatory agencies commission a working group comprised of representatives from grower groups, industry and government to oversee the process. The working group would support registrants as they populate (or update) the LSS template when a new product is submitted for registration, or as part of the natural review cycle.

    Should the registrant encounter duplicate, missing or contradictory information while completing the LSS, it should be considered an opportunity to remedy the problem on the pesticide label. This will clarify the safest and most effective use of the pesticide for the applicator, who is currently forced to selectively ignore or interpret such errors. To our minds, this was the intent of the original labelling system, and the inclusion of the LSS is a simple and effective way to achieve that goal.

    The Confusicol Sketch

    In 2018 we participated in Real Agriculture’s TechTour Live event that toured four major cities in Western Canada in four days. We presented the “Confusicol sketch” as a light-hearted way to open a discussion with the audience on the strengths and weaknesses of Canadian pesticide labels and how the Label Summary Sheet might be a viable supplement. Here’s one of the live takes, warts and all. Turns out live sketch comedy is tricky…

  • Exploding Sprayer Myths (ep.13): Reading Nozzles and Nozzle Tables

    Exploding Sprayer Myths (ep.13): Reading Nozzles and Nozzle Tables

    After a long hiatus, it’s lucky episode 13!

    In this installment, Dr. Tom Wolf, intrepid reporter, braves the unforgiving wilds of Saskatoon as he investigates claims of mysterious devices popping up all over the city. Colloquially referred to as “nozzles” these items are imprinted with obscure codes that scientists are struggling to decipher. Be the first to learn how to read a nozzle and nozzle table in our newest installment.

    Want to know more about selecting nozzles? Check out this article and this one.

    Special thanks to the @RealAgriculture team and the Western Grains Research Foundation.

  • Nozzle Night in Canada – Parody

    Nozzle Night in Canada – Parody

    In 2021 we were invited to participate in an episode of The Vegetable Beet podcast on the Great Lakes Vegetable Producer’s Network. As well as providing excellent agronomic information for vegetable producers, the hosts and producers were talented entertainers. Many of their episodes end with a mock sponsor reel that rivals Saturday Night Live. We were asked if we would like to collaborate on one of the sponsor reels. What a question.

    Michiganders they may be, but they’re as big a group of hockey fans as any Canadian. Since then the podcast was discontinued, but you can still give a listen to our spoof sponsor reel “Spring Sprayer Startup on Centre Ice”.

  • Micron Woman – Guide to the World of Spray Droplets

    Micron Woman – Guide to the World of Spray Droplets

    You just finished a great spray day. Everything felt right! Your timing and product choice were bang-on, the weather was good, and your sprayer was calibrated. But, do you know what happened to the spray once it left the nozzle?

    The behavior of spray droplets, and how they interact with the target, can be tough concepts to teach. Ironically, the big problem is how tiny everything is.

    What if you could see what was happening from the droplet’s perspective?
    Join Jason and Tom as a lab accident during a solar eclipse brings them face to face with a mighty new heroine:

    Micron Woman!

    If you enjoyed the video, it’s not over yet! We’ve printed actual comic books as fun and useful resources for anyone that wants a copy. We’ll distribute what we have to interested parties at conferences (just ask!). If you teach adults or children about agriculture, and you’re interested in copies, let us know and we’ll see what we can arrange.

    You can also download the comic book here:

    DOWNLOAD COMIC

    Thanks to everyone that helped bring Micron Woman to life! Who knows, maybe we’ll meet her arch nemesis in episode II? Write us if this is something you’d like to see!