Tag: nozzle

  • What is Spray Quality, Part 1 – Measuring Droplet Size

    What is Spray Quality, Part 1 – Measuring Droplet Size

    It’s often been said that droplet size is the most important factor governing spray operation success. Both spray drift and pesticide efficacy depend to a large degree on droplet size. For something this important, the droplet size information from nozzles ought to be accessible and easy to understand. 

    There are a few problems to overcome before we get there.

    The first is the difficulty in measuring droplets in the first place. Spray droplets are very small and evaporate quickly.  In the early days of spray technology research, sprays would be captured on a surface and individual droplets measured and counted under a microscope. A common approach was to use magnesium-oxide coated glass slides. The magnesium oxide layer was soft, and an impinging droplet left a tell-tale crater behind, much like those found on the moon’s surface. This allowed the analysis to be done after evaporation. Magnesium oxide does a great job but relies on droplets having enough momentum to leave their mark. There is also a spread factor (ratio of crater diameter to droplet diameter) that has to be known.

    Water-sensitive paper (WSP) is the modern version of this concept, and we’ve written much about the topic. Jason in particular has done a deep dive on how WSP works and how it’s analyzed.

    We can also add dye to spray mixtures to see deposits on various glossy paper surfaces.  The resolution of the dye-droplets can be better than those from WSP but their deposits can also be so faint that they pose thresholding and analysis problems.

    The great thing about impingement methods like WSP is that they’re easy to use, and they are particularly useful for a quick visual and qualitative assessment of coverage. If wanted, coverage can be quantified by scanning the WSP for percent area covered or deposit density.

    Droplet size determination is problematic on WSP because one needs to know the spread factor (how much larger the deposit is compared to the in-flight droplet that caused it) to back-calculate the original size of the in-flight droplet.

    Spread factor depends on droplet size, velocity, formulation, and the nature and orientation of the surface it’s collected on. The SF formula provided by the paper manufacturers is a good start but it is far from perfect.

    Fig. 1: Water-sensitive paper (WSP) treated with a Very Coarse spray at about 100 L/ha. Note the coalescence and overlap of some deposits.

    In addition, the overall droplet density has to be low enough to avoid overlaps or coalescence. Usually a water volume over 50 to 100 L/ha will create issues. The WSP also has to collect the droplet in the first place. Smaller droplets often move around larger objects such as a leaf, or a similar sized piece of paper. If they impact at a sharp angle, the deposit will be elongated due to smearing and that creates additional difficulties.

    Even if the paper collected the smallest droplets, they may not appear as stains. Droplets below a certain diameter (about 50 µm) do not leave a visible deposit on the paper. 

    So, while WSP is a great tool for visualizing a deposit, its limitations usually prevent it from being used to accurately measure the droplet size spectrum of a spray. 

    The Rise of the Laser

    In the 1970s and 80s, we saw the introduction of laser-based droplet size measurements. With these, a spray simply needed to be directed into a such an instrument, and it very quickly determined the diameter, and in some cases, the velocity, of the droplets. The principles employed by various laser instruments differed, and although one could now rapidly obtain data in-situ, the numbers among the instruments didn’t always agree.

    Fig 2: Laser instruments help to measure droplet size of sprays (photo source: TeeJet)

    The Most Common Laser Systems

    Laser diffraction: One of the first droplet sizing instruments is manufactured by Malvern (https://www.malvernpanalytical.com/en), and is still in use today. A laser beam passes through a spray cloud. The system uses a laser diffraction principle that works as follows, according to Malvern: “Large particles scatter light at small angles relative to the laser beam and small particles scatter light at large angles. The angular scattering intensity data is then analyzed to calculate the size of the particles responsible for creating the scattering pattern, using the Mie theory of light scattering.”

    To calculate the droplet sizes responsible for the scattering behaviour, the laser system has light-sensitive sensors in concentric circles behind the spray plume. When a sensor in the middle of these rings picked up a signal, it likely originated from a larger droplet because of its lower light scattering properties. Sensors further from the centre picked up smaller droplets. The system thus had an idea of the relative frequency of the various droplet sizes in the spray cloud and modelled these according to the classic Rossin-Rammler spray distribution model, from which descriptive parameters are calculated.

    Laser diffraction is the most popular method for in-situ droplet sizing. The company Sympatec (https://www.sympatec.com/en/) also offers a system that competes with Malvern that is found in many labs.

    Laser Shadowing: The Particle Measuring Systems (PMS) system was one of the earliest laser systems. It was a very compact and sturdy system that shone a laser light at the spray cloud and the droplets in that cloud cast shadows against a sensor array a fixed distance away. The size of these shadows could then be measured to arrive at a droplet size distribution. The PMS was particularly good at measuring small droplets.

    Although long discontinued, the PMS system had the basic appearance of a torpedo and was often mounted on aircraft or in wind tunnels to measure cloud aerosol sizes. Very cool. The company still manufactures other particle measuring devices (https://www.pmeasuring.com/).

    Pulsed Laser Illumination: This is a different approach to the laser shadowing of the PMS system. Oxford Lasers systems (https://oxfordlasers.com/) use a video camera to view the spray cloud and freeze images from using a very high frequency pulsed laser light. This light illuminates the cloud briefly which allows a still image to be briefly displayed.  Image analysis then measures the diameter of each particle in the image, adjusting for out-of-focus images.  It’s possible to analyze the speed and direction of the particles by comparing the particle position in subsequent images. This system is quite popular among scientists due to its ease of use. A portable unit that can be deployed in fields is available.

    Phase Doppler: In the mid 1980s, a system was developed that uses the Doppler principle to measure both the speed and diameter of droplets. Two out-of-phase laser beams intersected in a spray cloud, and a droplet passing through the intersection point created a Doppler burst that signalled the speed of the droplet. The burst signal also contained information on the droplet diameter, derived from a frequency shift of the two laser beams utilized in the system. This system has very high data acquisition and was the first to create a temporal sample of the spray, increasing the accuracy of the droplet size measurements.

    Initially brought to market by Aerometrics (later acquired by TSI) and called the Phase/Doppler Particle Analyzer (PDPA), it is now mainly offered by Dantech systems (https://www.dantecdynamics.com/).

    Sampling Bias: Temporal vs Spatial

    It’s not straightforward to measure a sample of moving objects. It may seem intuitive that if one wants to know how many objects are present, taking a picture and counting the objects would provide the answer. But when objects move at different speeds, that answer will be incorrect because the slower moving objects will be over-represented.

    Let’s assume you’re working on a traffic count project to understand the number of people crossing a bridge either walking or cycling. Let’s also assume that one walker and cyclist depart for the bridge every 5 seconds, i.e., there are the same number of each. If you wait until the bridge is full of people crossing and take a picture it will show more people walking on the bridge than riding bicycles. That is because the bicycles are faster and many will already have left the frame.  Thus counting the number of people in the picture over-estimates the number of walkers because they move slower.

    The same problem arises with these laser systems because in a hydraulic spray, the smaller droplets move slower than the larger droplets. Any system that takes a picture and counts what’s in it will have what’s called a spatial sample, overestimating the slower (smaller) droplets.

    A temporal sample can measure the velocity of the droplets and therefore account for their speed, giving a more accurate measure of the abundance of the droplets. In the case of the PDPA, it acheives this simply by counting all the individual droplets that pass, in sequence, through its meassurement area, called the probe volume. As they pass, it notes their velocity and diameter.

    To address this issue with a spatial sampling instrument, many labs now use wind tunnels and direct the spray to be tested with the wind direction. This forces the droplets to move at more or less the same velocity as the wind, eliminating or at least minimizing the speed differences before the droplets reach the laser instrument.

    WSP produces a temporal sample because it ultimately catches all droplets, but it has different types of sampling bias. Large deposits usually cover smaller ones. Smaller droplets may not impact on the target due to poor collection efficiency. Small droplets may dry too quickly to leave a visible stain. As a result, even if we had accurate spread factors, we would tend to under-estimate the number of smaller droplets, opposite of the error of spatial systems.

    Scanning the pattern

    Droplets are not distributed uniformly within a spray pattern. In a flat fan nozzle, for example, the centre of the pattern contains the smaller droplets. The outside edges of the pattern contain fewer small droplets and more large droplets. Some laser systems have a very shallow depth of field, and the PDPA is a point-measurement. As a result, it is not accurate to simply point the measuring device at a single location of the spray pattern. Accurate droplet size spectra from lasers requires a thorough traversing scan of the spray pattern along at least its long axis, and preferably two or more such traverses at increasing distances from this central axis. The scanning method would likely need to be adjusted to suit various types of atomizers, such as hollow cone nozzles.

    If no traversing mechanism is available, it is acceptable to measure the spray at several discrete locations and then merge the data prior to analysis. In all cases, three replicate samples should be taken so that an estimate of variability is available.

    Many labs, having compared a full scan with many traverses to those with fewer traverses have opted for a simple back and forth traverse with little loss in accuracy.

    Fig. 3: Possible ways of scanning a spray pattern for droplet size analysis. Top: traversing scan. Bottom: point scan

    Sometimes sprays are atomized within a chamber to prevent the droplets from contaminating the surrounding area if they contain any active ingredients. These chambers can also add measurement errors from, say, small droplets that recirculate within the chamber, or due to any glass surfaces through which the laser lights must pass. These all need to be considered, as they add to the many variables that create different results even when comparing identical sprays between labs.

    The next topic, covered here, is how to use the information we gather from droplet measurements. As you might expect, this is also not as straightforward as it seems.

  • Airblast Nozzles – Distributing Flow

    Airblast Nozzles – Distributing Flow

    There’s a certain deer-in-headlights expression that creeps onto a sprayer operator’s face when we discuss nozzle selection. We sympathize with our field sprayer clients given the variety of brands, styles, flow rates and spray qualities they must choose from. And PWM has made the process even more complex. However, airblast operators face an additional challenge; Unlike horizontal booms, vertical booms often distribute the flow unevenly to reflect relative differences in the distance-to-target and the density of the corresponding portion of target canopy. We discuss the broader, iterative process of nozzling an airblast boom here, but in this article we focus on the topic of flow distribution.

    An overwhelmed operator trying to nozzle a boom.

    The question of “which rate goes where” is still debated. It’s led to diagnostic devices called Vertical Patternators which show the profile of the spray. Operators can use these to visualize their distribution… but they are few and far between. For the rest of us, deciding on the best distribution begins with understanding how the practice evolved.

    The AAMS vertical patternator. The mast moves back and forth across the swath of a parked sprayer. Each black collector intercepts the spray at different heights. The fractions collect in the tubes at the bottom to show relative volume.
    A blurry shot of an OMAFA-built vertical patternator. The sprayer parks in front of the screens, which intercept spray. It’s collected in troughs and runs into columns that show relative volume.

    1950s

    In the 1950s, the mantra was to blow as much as you could, as hard as you could, and hope something stuck. At the time, John Bean promoted a method called “The 70% Rule” whereby operators used full-cone, high volume disc-core nozzles to emit the vast majority of the spray from the top boom positions. John Bean provided a slide-rule calculator to help operators configure booms to align the top nozzles with the deepest, densest portion of the 20-25 foot standard trees they were trying to protect. Back then, most airblast sprayers were engine-driven low-profile radial monsters capable of blowing to the tops of those trees. The practice persisted into the 60s and was encouraged by Cornell University (Brann, J.L. Jr. 1965. Factors affecting the thoroughness of spray application. N.Y. State. Arg. Exp. Sta. J. paper no. 1429).

    The profile of the spray would have looked something like the following graph:

    1970s

    In the 70s, extension specialists began advising operators to tailor the distribution to match the orchard spacing, tree architecture, canopy density and weather conditions. we reached deep into our archives for the Ontario Ministry of Agriculture and Food’s 1976 publication entitled “Orchard Sprayers” to see what we used to tell airblast operators.

    The 1976 update of Ontario’s 1971 “Orchard Sprayers” guide. A trove of hard-earned knowledge that still has relevance today. I love that the Minister’s name, and not the author’s, is on the cover. Let’s set the record straight: R. W. Fisher, D. R. Menzies and A. Hikichi, based in Vineland and Simcoe, Ontario.

    Here’s a synopsis of what was advised:

    1. Choose a tree size and shape that is typical of your orchard and park the sprayer at the normal spraying distance from it.
    2. Find one or two middle nozzle position(s) and air deflector or vane settings that direct the spray up through the top-inside of the tree. This is called the “middle volume zone”.
    3. Find rates that will give a large output in this middle volume zone, and smaller outputs for positions above and below.
    4. The total output must still add up to the target volume.

    It seemed operators were getting away from high rates in the top positions and instead shifting the distribution to match the canopy shape and density. If we were to follow these recommendations, the spray profile would look something like this:

    Later, Agriculture Canada’s 1977 publication entitled “Air-Blast Orchard Sprayers – A Operation and Maintenance Manual” had similar advice. Here we find the “2/3 boom rule” as the authors state: “To ensure good distribution through the trees, about two-thirds of the spray should be emitted from the upper half of the manifold.”

    1980s

    Operators followed this approach well into the 80s, as they endeavored to aim the majority of the spray into the densest part of the canopy. Many can relate to the following illustration that divides the boom, which I modified from an array of period factsheets. The fractions represent the portion of the available boom. The percentages indicate the relative volume. Of course, it matters how large and how far away the target is for either the 2/3-boom or 70% rule to make sense (the middle volume zone is shown receiving 65-70% in the silhouette).

    1990s-2000s

    The 2/3 or 70% rules still work for standard nut and citrus trees, and perhaps for large cherry trees, but pome and tender fruit orchard architecture is densifying at this point in time. In the 90s and 00s we started transitioning from semi-dwarf into trellised, high density orchards.

    Leaping to 2005, Ohio’s Dr. Heping Zhu et al., found that a high density orchard is effectively sprayed by the same rate in each nozzle position. They wrote: “[Historical] recommendations are to use a larger nozzle at the top of each side, with the capacity of the top nozzle at least three times greater than other individual nozzles. However, results in this study with three different spray techniques showed that spray deposit was uniform across the tree canopy from top to bottom with the equal capacity nozzles on the air blast sprayer.”

    What a pleasant surprise to simplify our lives! If we can use an even distribution for dense, nearby trees, it follows that any vertical crop with the same width and density located close to the sprayer (e.g. cane fruit, trellised vines, etc.) would benefit from even distribution:

    Today (2020s)

    So, how do we do it today? There is still no simple answer; Conditions change, not all sprayers are the same, and not all applications have the same target. Let’s build on what history has taught us and establish a process to achieve better coverage uniformity and reduce waste.

    No matter the crop, the operator must first adjust air settings. Air volume and direction play the most critical role in transporting a droplet to (and into) a target canopy. Too high an air speed will cause spray to blow through the target, rather than allowing it to deposit within. Aim the air just over, and just under, the average canopy. Ensure there’s enough air to overcome ambient wind and to push the spray just past the middle of the target canopy.

    It should be noted that we assume the operator is spraying every row. With certain exceptions, alternate row middle spraying is not generally recommended. Not only can it compromise coverage on the far side of the target, it makes it far harder to match the nozzling on a single-row sprayer and is a sure-fire way to increase drift.

    Next, determine which nozzles are not needed (e.g. spraying the ground or excessively higher than the top of the canopy). Remember: hollow cones overlap very close to the boom and spread as much as 80°. Airblast sprayers rarely if ever need the lowest positions and unless spraying overhead trellises they may not need the highest either. Turning off the highest, and most drift-prone, nozzle positions in high density orchards is illustrated in the logo I was asked to create for Washington’s short-lived Pound the Plume awareness campaign in 2017.

    Then, finally, we decide on distribution. If the crop is nearby and relatively narrow, you can try even distribution. If you elect to distribute the spray unevenly to better match the variable-width target, or compensate for distance, aim half the overall output at the densest part of the canopy (the middle volume zone). Consider how the following factors might influence your choices:

    1. High humidity means more spray will reach the target, and vice versa. This is because all droplets are prone to evaporation. We have heard it said in hot, dry conditions (described by Delta T), a droplet can lose ½ its diameter every 10 feet. As they evaporate they get lighter, meaning they are less subject to their original vector and the pull of gravity, and more subject to deflection by wind. The use or coarser droplets, and/or humectants, can help, but higher volumes can help too – they increase the odds of some droplets hitting the target and actually humidify the air to slow evaporation.
    2. Windspeed increases with elevation, so spray is most likely to deflect at the top of canopies where they have already lost size (and momentum and direction). Early in the season when there is little if any foliage, wind speeds are higher overall. This is why we advise adjusting air settings using a ribbon test before considering boom distribution – you need enough air volume, aimed correctly, to get the spray to the top.
    3. The denser and deeper a canopy, the more spray is filtered and unavailable for coverage. This is why you will always achieve more coverage on the adjacent, outer portion of a canopy versus the interior. In semi dwarf apple orchards we have seen the coverage drop by half for every meter of canopy. Finer spray can penetrate more deeply because there are more droplets and they move erratically, whereas coarser droplets move in straight lines and impact on the first thing they encounter. Higher volumes will improve penetration and overall coverage, but there is a diminishing return and runoff will occur more quickly leading to more waste.
    4. Further to the last point, remember that it’s the air that propels the spray, not the pressure. Higher liquid pressure can propel coarser droplets further, but has little effect on finer droplets. imagine throwing a golf ball and a ping pong ball into a light headwind and envision how they fly. Plus, the higher the pressure, the finer the mean droplet diameter.

    Confirm Your Work

    To know how all these factors play out, you must use water sensitive paper (or some other form of coverage indicator) to diagnose the results. Remember, the goal is uniform coverage and for most foliar products, we want to achieve a minimum coverage threshold of 10-15% and a droplet density of 85 deposits per cm2 on at least 80% of the targets.

    Taking the time to match your output to the target has the potential to greatly improve coverage and reduce waste. Nozzle body flips and quick-change nozzle caps make the process of switching nozzles between blocks fast and easy. It’s worth it.

    Grateful thanks to Mark Ledebuhr, Gail Amos and Heping Zhu who edited, corrected and contributed to this article.

  • Angled Spray Nozzles in Wheat

    Angled Spray Nozzles in Wheat

    When T3 wheat rears its head, the first rainy day brings questions about spray angles. Let’s begin with a graphic that illustrates how angled sprays cover a vertical target like a wheat head. Assuming moderate wind and sufficiently large droplets, this is a simplified depiction of what we would expect to see.

    But is this how the nozzles actually perform? Are dual angles really better than a single fan with an aggressive angle? We hoped to answer these questions when we demonstrated a selection of dual fan nozzles at Canada’s Outdoor Farm Show in 2013. But it was a very windy few days and what we saw was that regardless of the nozzle, most of the spray tended to deposit with the wind.

    A 10 km/h wind will easily deflect Medium-and-smaller droplets and at 20 km/h all but the coarsest spray is deflected. This leads to non-uniform deposits and unacceptable levels of drift (yes, even through it’s a fungicide and you have lots of acreage.) To learn more, we turned to the literature to review studies performed in Ontario and Saskatchewan.

    Wolf and Caldwell

    In 2002, Dr. Tom Wolf and Brian Caldwell experimented with fan angles. They evaluated the impact of nozzle angle, travel speed, and droplet size on the “front” (facing the sprayer’s advance) and “back” (sprayer’s retreat) of vertical targets. They ran three laboratory experiments: spray configuration (single vs. double fan), travel speed (7.6 and 15.2 km/h) and spray quality (conventional versus air-induced droplets) using TeeJet XR’s and Billericay air bubbles at a rate of 175 L/ha. Here’s what they observed:

    • Larger, air-induced droplets produced higher average deposits than smaller, conventional droplets.
    • Twin fans improved overall average deposit compared to single fans.
    • Building on the first two points, twin air-induction fans improved overall average deposit versus conventional twin fans, and also improved deposit uniformity (i.e. coverage on the front versus the back of the vertical targets).
    • Higher travel speeds improved overall average deposit, but at the cost of reduced uniformity as the rear-facing target received reduced coverage (particularly in the case of conventional droplets).
    • Spray angle did not impact coverage from conventional tips, but increasing from 30 to 60 degrees improved coverage for AI tips.

    While the coverage data was compelling, growers were not reporting improved efficacy with the improved coverage. The authors felt there were confounding variables like crop susceptibility, disease pressure and product effectiveness. Their conclusion was that applicators should strive for improved coverage, but only after integrated pest management (IPM) criteria such as product choice, crop staging and application timing are satisfied.

    Hooker and Spieser

    In 2004, Dr. David Hooker (University of Guelph) and Helmut Spieser (OMAFRA) started exploring nozzle configuration and sprayer set-ups to optimize Folicur applications in wheat. For several years they ran field trials exploring panoramic wheat head coverage. That is, not only the front and back of the wheat head, but the sides as well. Ten different nozzle configurations were used:

    • TurboTeeJets mounted in dual swivel bodies (backwards and forwards)
    • AirMix air induction nozzles mounted in dual swivel bodies
    • Air induced Turbo TeeJets mounted in dual swivel bodies
    • Single Turbo TeeJets angled forward or angled backwards
    • Single Turbo FloodJets angled forward or angled backwards
    • TwinJets
    • Single Hollow cones
    • Turbo TeeJet’s mounted in Twincaps
    • Turbo TeeJet Duos
    • Single Turbo FloodJets alternating forward and backwards

    They explored boom height (0.5 m and 0.8 m above the crop), travel speed (10 km/h and 20 km/h) and application volume (93.5 L/ha and 187 L/ha). Here is a summary of their findings:

    • Travel speed did not appear to impact overall coverage.
    • Spraying higher volumes improved coverage.
    • Lowering the boom improved coverage.
    • Coverage from conventional flat fans and TwinJets gave ~15-18% coverage and 22-26 mg of copper was deposited per m2, but alternating Turbo FloodJets gave ~29% coverage and deposited ~37 mg copper per m2.
    • The highest percent coverage was obtained using Turbo TeeJets or the AirMix tips mounted in dual swivels (~26% coverage), or single Turbo Floodjets alternating forward and backwards (34% coverage) as long as the spray was not obstructed by the boom structure itself.

    Hooker and Schaafsma

    A few years later, Dr. Hooker and Dr. Art Schaafsma worked with OMAFRA to explore efficacy. DON is a mycotoxin that may be produced in wheat infected by Fusarium Head Blight (FHB) or scab. There is an indirect relationship between wheat head coverage of fungicide and the reduction of FHB and DON: The higher and more uniform the coverage (with the right timing) the lower FHB and DON.

    In two field experiments they performed in 2008, DON values in the untreated checks were around four parts per million. DON was reduced by an average of 22.5% using a single flat fan, 23.0% using a TwinJet and 41.5% using alternating Turbo FloodJets when averaged across two fields, two fungicides and four reps (n=16). They all reduced DON significantly. There was no statistical difference between singles and twins, but control from the alternating Turbo FloodJets was significantly better.

    The Return of Wolf and Caldwell

    Then, in 2012, Tom and Brian evaluated the new asymmetrical twin fan nozzles from TeeJet. The marketing claimed they could improve overall coverage at higher travel speeds because they decrease the contribution of the front-facing fan and increased the angle of the back. Tom and Brian’s lab-based experiments determined that:

    • Asymmetricals increased overall deposit amounts and uniformity versus single fan and symmetrical twin fans.
    • Nozzle orientation (alternating or not) seemed unimportant.
    • As suggested earlier, boom height was a big factor in coverage. Nozzle angle didn’t improve coverage when the boom was too high, but spray deposit increased significantly when the boom was lowered.
    • Coarser spray droplets have more momentum, so they can travel greater distances on their original vector. A coarser spray quality is the best choice for any angled fan.

    Water volumes and FHB

    Let’s address the notion that high water volumes might increase Fusarium Head Blight (FHB). This is a hypothesis that seems to have resonated with growers. Dr. David Hooker ran trials where he tried to favour FHB by spraying 40-50 gpa of water multiple times per day (even up to 100 gpa). There was no pathological impact (personal communication).

    Consider that 1″ of rain is the equivalent of 2,715 gpa of water. Raising your carrier volume from 15 gpa to 20 gpa is the equivalent of 0.000184″ of rain. Admittedly, it’s all aimed at the wheat head, but it’s still a tremendously small volume. While studies have shown a diminishing return in coverage at 30 or 40 gpa, spraying with 20 gpa appears to be a safe way to improve coverage significantly.

    Learn more about early morning spraying here, and a more in depth discussion of spraying when there is dew here.

    PWM

    What if you’re running a PWM system? Sizing for PWM requires the tip be sized about 20-40% more than if you were running a conventional sprayer. In other words, at expected travel speeds, the pulsing duty cycle should be approximately 60-80%. Nozzles that are permitted on PWM sprayers are limited and the angled fan selection for PWM is, at the time of writing, more so. It requires some experimenting. The following list uses the JD Exact Apply as an example system, and it is not exhaustive. We’re always looking for new ideas.

    1. 3D90 (the original 3D is arguably too misty) in the A or B positions, alternating front and back <or> in both A and B positions. This tip may not be readily available in North America.
    2. LDT (Low Drift Twin) which is two LD tips installed in a Twincap (twin 30° angles) in position A or B.
    3. LDM (Low Drift Max) which is two LDM installed in a Twincap in position A or B. This tip only goes down to an 03.
    4. The Deere 40 degree angled adaptor (developed for See and Spray) can be used to convert any PWM-compatible nozzle into an angled spray.
    5. GAT (GuardianAir Twin) is an air-induced tip, running in conventional “A” mode or in Auto Mode but sized for “B”. Avoid operating in A and B to prevent pattern interference.
    6. Wilger Wye Adaptor with SR nozzles. This does cause tips to drop below the boom frame but is a versatile option.
    7. Wilger Dual Angle Max. More compact than the wye adaptor, this asymmetrical assembly (30° fore and 50° aft) prioritizes Coarse spray.
    8. TeeJet Accupulse TwinJet.
    9. Greenleaf Blended Pulse Dual Fan Assembly.

    Summary

    So here’s what we can say based on all this research:

    • Higher volumes improve coverage (significantly up to ~200 L/ha or 20 gpa). Can you go to 30 gpa? Yes, and it will likely improve coverage, but it’s a diminishing return and at some point you will incur run-off.
    • When using angled sprays, coarser droplets improve vertical coverage. Compared to finer droplets, they move faster, survive longer (i.e. resist evaporation) and are less likely to be deflected by wind.
    • Maintaining the lowest operable boom height improves coverage from angled sprays. We want 100% overlap at target height, and with angled sprays that means getting pretty close. Aim for the highest wheat heads and not the tillers. If you’re 2′ away, you’re likely too high.
    • Symmetrical fans with shallow angles (e.g. 30°) improve coverage uniformity on vertical targets versus single fans, and a steeper backward-facing angle (e.g. 70°) improves coverage even more on the sprayer-retreat side.
    • Travel speed may or may not affect coverage, but slower speeds do facilitate lower booms, which do improve coverage.
    • Timing, weather and product choice are likely the most critical factors.

    Angled sprays may offer some advantage in other situations, but they are primarily intended for panoramic coverage of vertical targets.

    Short videos about dual fans

  • Nozzle Choice in Vegetable Crops – an Australian Perspective

    Nozzle Choice in Vegetable Crops – an Australian Perspective

    Editor’s Note: Any brand-specific references or recommendations in this article are based on the author’s experience. Sprayers101 endeavours to preserve brand independence and impartiality to best serve our readers. This article was originally posted in 2018.

    During my many years of work in the Australian vegetable and horticultural industry, I am continually asked:

    Q. What is the best spray unit to use?

    My answer is simple:

    A. The one that has been correctly set up and matched to the crop you are spraying.

    That can be hard to achieve, especially in vegetable crops where the target can vary enormously from bare ground to upright leaf crops (e.g. onions), to horizontal leaf crops (e.g. potatoes and brassica).

    Generally, I have found that air-assist booms offer the best starting point for achieving good spray coverage of vegetable crops. However, like any spray boom, they must be set up correctly. Air-assist booms are more expensive and require a few more horses to operate, which is why most Australian vegetable growers prefer to make do with a non air-assist boom.

    So, if air-assist isn’t an option, it then becomes imperative to determine the most suitable nozzles for their particular requirements. I have worked in many vegetable crops over the years. I’ve held my share of “fluorescent dye nights” and checked spray coverage and canopy penetration with many grower groups. Based on my experience, there are three types of nozzles I recommend for most vegetable crops:

    Nozzle #1: Air Induction Flat Fan

    Here’s what I say when the grower (inevitably) asks which nozzle is the best for every task:

    Using only one nozzle will compromise some aspect of a series of applications. However, the Syngenta 110 025 air induction nozzle generally performs well. Manufactured by Hypro it creates more droplets per liter than other air induction nozzles of the same size (as of 2018). (Editor’s note: as of 2025, a likely North American equivalent is alternating-direction Syngenta 3D 90’s. They produce a high-velocity Extremely Coarse-Ultra Coarse spray quality and the manufacturer claims they improve the penetration of broad leaf canopies over conventionally-angled sprays. However, when drift potential is low, travel speed is reasonable, and boom height is low, alternating-direction Defy 3Ds produce a Medium-Coarse Spray quality which may be more conducive to retention on hard-to-wet vertical targets).

    As long as the crop isn’t too large (e.g. later season), I recommend this nozzle with lower water volumes. This is because I tend to see more application issues arising from excessive water rates that wash product off the plant. Unless you are after soil borne diseases, avoid run-off and wastage by using the SAI 110 -25 with volumes of about 200 L/ha. The following graph shows the results of application volume on brussels sprout coverage (per Syngenta UK).

    Nozzle #2: Narrow Spray-Angle Flat Fan

    When I am trying to increase canopy penetration, I like the Syngenta Vegetable Nozzle (SV65-04 flat fan). I feel the narrow spray fan angle delivers a directed spray pattern into the crop canopy which can significantly improve penetration. This is a good fit for late-season insecticide and fungicide sprays in brassica crops, where pests and diseases can be hidden deep in the crop canopy.

    I worked with a vegetable grower who was having trouble controlling sclerotinia in his mature fennel crop. The target was the base of the stem, deep in the canopy. In the following image you can see the water sensitive paper taken from ground-level in the canopy. The nozzles used from left to right are; Hardi Twin AI 110-05, Syngenta 65-06 vegetable nozzle and Syngenta AI 110-05. Coverage was estimated using the SnapCard app (freely available for iPhone and Android platforms). (Editor’s note: as of 2025, Syngenta’s silver 06 and gold 08 vegetable nozzles are not available in North America. They produce high volume, slow-moving, Coarse-Very Coarse sprays. TeeJet’s Visiflo is a 65 degree tip, but produces too fine a spray quality to be serviceable. As spot-spraying is increasingly adopted, the development of narrow-angled nozzles is anticipated and may offer a reasonable alternative.).

    So, I know pyrethrum is a flower and not a vegetable crop (think chrysanthemum), but it can be hard to penetrate, so this is a good example. We compared five nozzles and estimated coverage using SnapCard. The Veg 65-04, AI 110-035, and Twin AI 110-04 seemed to improve coverage over the Defy 3D 85-04 and conventional AI 110-04.

    For broadacre farmers (i.e. field or cereal crops) the SV65 flat fan nozzle has also proven to be extremely successful at penetrating thick standing stubble residue when using pre-emergent herbicides. Likewise, it performs well when targeting lower leaves during fungicide applications. Again, I believe that this is due to the narrow fan angle of the spray giving a more direct spray down through both the stubble and the current season’s foliage. Be attentive to nozzle spacing and boom height when using narrow fan angles to ensure correct overlap and complete coverage.

    Nozzle #3: Angled Flat Fan

    For onions and broadleaf crops (e.g. potatoes and beans), I feel the nozzles that have their spray fans angled forwards and backwards along the (non air-assist) boom are best suited.

    The following image shows coverage from angled sprays on simulated upright targets in the field using water sensitive paper.

    The Syngenta angled nozzles are designed with a 30° incline intended to improve foliar coverage down to the lower leaves on some vegetable crops. Although originally designed for use in potato crops, I have also had success in other vegetable crops such as onions and leeks. (Editor’s note: as of 2025, the Gold 04 and Orange 05 potato nozzles do not appear to be commercially available, although possibly in Ireland. They produced a ~Medium spray quality at an angle similar to that of the vegetable nozzles).

    Summary

    No matter the nozzle choice, or how good the application technique may be, the priority should be to manage disease and insect pests early in crop development. If you are trying to control heavy pressure from disease or insects and it’s deep within the crop canopy, often, you’re going to come off second best. Prevention is always better than cure, no matter what crop protection product you are spraying.

    With that caveat, I’ll leave you with my suggested nozzle choices. Preferably, I would suggest installing (at least) a triplet nozzle selector to quickly change between three nozzles for each crop.

    CropGrowth StageWater Volume (L/ha)Suggested NozzleNotes
    CabbageSmall, open100-200Air InductionRun-off is the enemy of small plants.
    Hearted300-80065 ° Fan Angle NozzleAngled spray important to get spray under top leaves. Use twin cap option for volumes greater than 300 L/ha.
    CarrotsSmall100-200Air InductionCarrots are good at catching spray. Angling nozzles e.g. Twin Cap will give best results.
    Large200-40065 ° Fan Angle Nozzle65º fan the best for penetrating to crown. Apply volume of 200 L/ha, increasing to 400 L/ha in denser crops. Avoid air induction (aka bubble jet) and hollow cone nozzles for later application timings.
    Brussels SproutsSmall, open100-200Syngenta AI 110025Run-off is the enemy of small plants.
    Large200-300Syngenta 3D nozzle 85 04 or 85 05
    LeeksSmall100Syngenta 3D Nozzle 85 03, 85 035 and 85 04 cover both sides of the plant.Coverage, run-off and missing the target are the problems likely in Leeks. Angled spray forward and backwards is important. High Volumes = Run-off.
    Large200-300Syngenta 3D nozzle 85 04 or 85 05Angled spray forward and backward. High Volumes = Run-off.
    LettuceSmall, open100-200Air Induction Run-off is the enemy of small plants.
    Hearted300-80065 ° Fan Angle Nozzle
    OnionsSmall100Syngenta 3D Nozzle 85 03, 85 035 and 85 04 cover both sides of the plant.Coverage, run-off and missing the target are the problems likely in onions. Angled spray forward and backwards is important. High volumes = run-off.
    Large200Syngenta 3D Nozzle 85 04 or 85 05Angled spray forward and backward to cover both sides of the plant.
    PotatoesPrior to row closure100Syngenta Pre-em 03 nozzleAngled spray forward and backward.
    After row closureSyngenta 3D Nozzle 85 03, 85 035 and 85 04
    Pre harvest (desiccation)200-400Syngenta 3D Nozzle 85 04 or 85 05The desiccation of very large canopies may require up to 400 L/ha of water on the 1st application.
    Peas and Edible BeansSmall100Syngenta 3D Nozzle 85 04 for 7–9 km/hr. Syngenta 3D Nozzle 85 05 for 10–12 km/hr.Medium spray quality and use higher water volumes in dense crops. All nozzles 0.4-0.5 m above top of crop.
    Large200
  • Nitrogen Application Technology in Winter Wheat

    Nitrogen Application Technology in Winter Wheat

    With an ever growing selection of options for nozzles and streamer bars, many growers are asking the question, what should I outfit my sprayer with for winter wheat liquid fertilizer applications? Well, it depends on what are you trying to accomplish.

    If the goal is to push your winter wheat management and improve yields, then the accurate and uniform application of liquid nitrogen is key. Selecting the appropriate sprayer technology can have a huge impact. Using a twitter poll, we learned that growers use many methods:

    • 3, 5, 6 or 7 hole streamer nozzles
    • Flood nozzles
    • 3 or 5 hole streamer bars

    Let’s look at some of the options and consider why you might choose one technology over another.

    Floods on a Terra-Gator. Photo courtesy of Kyle DeCorte.

    Air Induction, Conventional Flat Fan or Flood Nozzles

    Let’s get this one out of the way first. Air induction (AI), conventional flat fan and flood nozzles are a no-go when it comes to applying 28% UAN in winter wheat. Dr. Peter Sikkema (University of Guelph) demonstrated that when 28% UAN was applied with an AI nozzle there was an increase in visual crop injury (Table 1).

    He also showed that injury increased substantially when tank-mixed with herbicides and when nitrogen applications were delayed (Table 2). So, while AI nozzles are great for herbicide applications, they are not suitable for 28%. Growers should consider fall weed control to avoid the need for spring herbicide applications.

    Table 1. Potential yield loss associated with applying UAN 28% as overall broadcast treatment using FloodJet or TeeJet nozzles. 11 gallon (Imperial) = 1.2 U.S gal. Source: P. Sikkema, University of Guelph (RCAT), 2008–2013 (OMAFRA Pub 811: Agronomy Guide).

    Application CombinationVisual InjuryYield
    200 L/ha water (18 1g/ac water)0%6.4 t/ha (95 bu/ac)
    150 L/ha water + 50L/ha UAN (13.4 g/ac water +4.5 gal/acre UAN)3%6.4 t/ha (95 bu/ac)
    100 L/ha water + 100L/ha UAN (9 g/ac water +9 g/ac UAN)5%6.1 t/ha (91 bu/ac)
    50 L/ha water + 150L/ha UAN (4.5 g/ac water +13.4 g/ac UAN)7%6.1 t/ha (91 bu/ac)
    200 L/ha UAN (18 g/ac UAN)9%6.0 t/ha (89 bu/ac)

    Table 2. Crop injury (%) and yield (bu/ac) of winter wheat following an application of 28% UAN (400 L/ha) alone with air induction nozzles and with various herbicides compared to an untreated control that received the same amount of nitrogen. Source: Dr. P.H. Sikkema, 3 trials from 2008-2010, University of Guelph (Ridgetown Campus) – Additional information on tank-mixing with herbicides can be found here.

    TreatmentHerbicide rate/acInjury (%)Yield (bu/ac)
    control (unsprayed)——0105
    28% UAN alone——6105
    28% UAN + Infinity0.33 L9104
    28% UAN + Buctril M0.4 L8103
    28% UAN + Estaprop XT0.48 L9102
    28% UAN + Refine M12 g + 0.36 L1799

    Streamer Nozzles

    Streamers significantly reduce crop injury when applying UAN 28% in winter wheat. Growers in Ontario are using a range of 3, 5, 6 and 7 hole nozzles. These nozzles provide even coverage and minimize burn compared to flat-fan or flood nozzles; however, boom height can have an impact on crop injury. This is particularly important with 3 and 6 hole streamer nozzles. If there are significant variations in boom height (e.g. uneven emergence, uneven land, or a boom with excessive sway and yaw), significant crop injury can occur. This is exacerbated by hot and dry conditions.

    The damage is the result of non-uniform coverage. Streamers deliver spray in a triangular shape. If the boom is too low gaps in the spray pattern reduce coverage. If the boom is too high the crop may receive increased overlap, resulting in crop injury. Therefore, these nozzles are an excellent option for apply UAN 28% to winter wheat crop (see image below) as long as boom height can be managed effectively.

    Pro tip: 28-0-0 often has crystals so strainers are important.

    UAN 28% being applied uniformly to winter wheat using 3 hole streamer nozzles. Photo courtesy of: Jim Patton.

    Streamer Bars

    Streamer bars (see image below) may be the best choice. Streamer bars deliver liquid nitrogen to the crop vertically. This allows for even distribution across the winter wheat crop at various boom heights, often permitting great speed. Some even have a sliding orifice to permit an easy transition between rates. Research performed in Kentucky showed that streamer bars produced a 2.8 bu/ac yield advantage compared to 3 hole streamer nozzles, and a 4.9 bu/ac yield advantage over 7 hole streamer nozzles.

    Some may argue those aren’t significant yield advantages, but most Ontario growers would argue differently. Streamer bars provide uniform coverage no matter the state of emergence, boom height, topography or even wind conditions. Streamer bars can be adapted to most sprayers and are available in 15″ or 20″ spacing. The only caveat is that they can be fragile and can make folding the boom difficult.

    Chafer streamer bar. Photo courtesy of Alex Zelem.

    Other Ways to Reduce Burn

    In addition to proper nozzle selection there are a few things you can do to reduce the risk of crop injury from N applications.

    • Avoid applications of 28% when the crop is stressed or during hot and dry conditions.
    • If conditions are more conducive for crop injury, increasing water volumes or applying less N can also help reduce burn significantly.

    At the end of the day it is important to remember the end goal – maximize yield potential. If we can deliver UAN 28% as uniformly as possible to a standing winter wheat crop while minimizing crop injury, the 100+ bu/ac wheat crop will be well worth the effort.

    Here’s Peter Johnson (@WheatPete) to tell you more in this RealAgriculture Wheat School episode: