Tag: recirculating booms

  • Recirculating Boom Options

    Recirculating Boom Options

    If you read this site, you know we’re fans of recirculating booms. We love them for three reasons:

    1. They save money and waste by recovering spray back to the tank during priming and rinsing
    2. They make boom cleaning easier by eliminating boom-ends
    3. Most require individual nozzle shutoff, which makes for better sectional control

    If you’re new to the concept of recirculating booms, read more here.

    Until recently, these booms were only available on sprayers imported from outside North America (Horsch, Amazone, Agrifac to mention three), or via France’s Pommier booms that have been available as retrofits for many years. In 2018, Agco introduced their Liquid Logic system on the Rogator line, becoming the first North American manufacturer to offer a recirculating boom at the factory. Pattison Liquid also offers Recirculating booms as standard equipment on their Connect Sniper pull-type sprayer.

    In the meantime, three boom retrofit kits and one sectional conversion kit have become available.

    Arag Australia‘s BRS (Boom Recirculation System)

    The first was developed by Arag Australia, and is available there via Nozzles Online, and in Canada through Nozzle Ninja. Designed for John Deere R-Series and Case Patriot sprayers, the kit uses the existing line that feeds liquid to the outermost section and simply extend that line to the end where it enters the boom via two installed elbows. The liquid returns to the centre via the installed boom sections which are connected together by removing the boom end cap (or “aspirator” for John Deere) and replacing the gap with a section of hose. Back at the centre rack, the liquid from both booms meet in the middle. At this point, a three-way valve gives the choice to return the spray to the tank, or to receive pressure from the pump. There is also a manual valve that allows the return to be dumped for safe disposal.

    Arag Boom Recirculation System (Spray Mode)
    Arag Boom Recirculation System (Recirculation Mode)

    The system does not tie into the sprayer’s electronics. instead, it adds a switch in the cab that the operator uses to switch from spray mode to recirculation mode. The switch is not activated at the end of each swath, but instead to prime or flush the boom.

    A switch is added so the user chooses recirculation or spray mode. The boom would recirculate to prime or flush, and remain in spray mode during the spray operation.

    Raven

    Raven offers a recirculation kit for 3000, 4000, and 5000 series Case Patriot sprayers with Aim Command HD and an ISOBUS terminal. The approach is slightly different, as they retain the pressure feed through individual sections but also tie the sections together so the spray is returned to the tank. By including a shutoff valve between each section, the system retains the option to use conventional sectional control for high flow situations, or to isolate a section should a leak occur. The system can be configured and controlled from the sprayer monitor, either a Viper 4+, CR7, or CR12.

    Raven Boom Recircualtion System schematic (from Raven manual). Note the retention of section valves and the addition of manual valves between sections.

    John Deere

    On March 2, 2021, John Deere announced a 2022 factory option called Pressure Recirculation and Product Reclaim. The system keeps several existing sections and adds two steel lines the flull length of each boom wing. One is for supply, the other return. As these lines approach a section, the supply is fed to one end of the section and the return is connected to the other end. On a 120′ boom, there are five recirculating sections, two on each wing and the centre.

    This approach adds one more line than the other designs, and this line will hold materials that ultimately need to be cleaned, flushed, and possibly dumped or sprayed out for cleanout. A possible reason for the extra line is the ability to deliver 220 gpm to the boom, an advertised feature of John Deere high flow booms that may come in handy for topdressing liquid fertilizer. These levels of volume are not needed for pesticides.

    John Deere Boom Recirculation and Reclaim. Top two lines are supply and return and extend the length of each boom wing. These connect to the existing sections on each wing, creating several smaller recirculating sections.

    Latitude Ag

    This Wisconsin company has developed an innovative product that converts any existing plumbed section that contains boom ends into a recirculating section. It does this by incorporating a boom recirculation valve” (the “Merlin IC System“) into the original section feed line. Boom end caps are removed and replaced with sweeps and hoses that return flow to these boom valves. The flow from the boom ends is incorporated back into the sectional feed thanks to a venturi design in the recirculation valve.

    A prototype of the Merlin IC System valve made by Latitude Ag

    Advantages of this design include simplicity. No moving parts are required, the valve simply recirculates the flow from the boom ends automatically whenever that section operates. Existing sectional control, whether it’s by plumbed section or individual nozzle bodies, is unaffected. Flushing the boom with water is done with normal spraying. It takes some extra time to incorporate and dilute the contents of the boom end return lines but results in a clean boom and no section end residue. We’ve seen the results of testing and agree that it works.

    This product does not allow boom priming without spraying. However, a key advantage is that it can be used with direct injection since no product is returned to the tank. Latitude Ag says it will provide the necessary flow sensor and software to make this possible. As of 2025, this system may no longer be commercially available.

    Precision Planting ReClaim

    ReClaim is capable of operating on a sprayer with or without individual nozzle shutoff. For conventional nozzle bodies containing the original spring-loaded diaphragm check valves, the concept is to drop the liquid pressure below the cracking point of the check valves so flow continues through the sections and back to the tank without engaging the nozzles.

    Recirculation fittings are added to the end of each boom section. These feed into 3/4″ lines are installed on section ends, which in turn feed increasing diameter collector lines that eventually return all flow to the tank. Flow reaches the sections as before. When recirculation is turned on, flow exits the boom section through the new fittings and returns through 3/4″ lines to the centre of each section, where it enters 1” lines that take the flow to the center of each boom wing. There the flow in the 1” lines is combined moves to the center of the sprayer on 1.5” lines where it meets the flow from the other wing.  From there, the flow returns to the tank through an electronic ball valve and 2” line. This system ensures no back-pressure and balanced flow from each section.

    For some sprayer rate control systems such as John Deere, the pump won’t operate below about 20 psi despite operator settings. This means the priming or flushing procedure would trigger nozzles to spray if the bodies were fitted with spring-loaded diaphragm check valves. A pressure reduction kit (a second restrictor valve) is required to reduce the pressure sufficiently for ReClaim to work in these instances. More here.

    ReClaim operates independently of any electronic control systems, relying on a toggle switch to initiate recirculation. When flow back to the tank is detected, a light indicates that recirculation is working, and the operator waits approximately 60 sections for a 120’ boom to circulate all volume back to the tank. Download the operator’s guide, here.

    This system requires a lot of additional lines. A 120’ boom would require 120’ of additional 1” line and 60’ of 1.5” line. The manufacturer states that ReClaim adds about 14 gallons of volume that would need to be displaced back to the tank, adding to the standing volume. This volume can be circulated using solution from the main solution tank, or displaced back to the tank using flow from an existing clean water tank, or displaced using compressed air via an optional pneumatic port. It is not clear how spray mix in the ReClaim system can be removed from lines without returning it to the tank and draining it from there. Users should consider the additional surface area and volume that will have to be addressed during cleanout.

    Do It Yourself

    If none of the available options work for your sprayer, consider building your own system. Sprayer plumbing parts are available from the major manufacturers Banjo, Hypro, TeeJet, and Wilger. Wilger, in particular, has developed a nice suite of parts well suited to recirculating booms, including flanged sweeps and thin gauge steel booms, punched for nozzle bodies or unpunched to move product. See their support for DIY projects on this dedicated page: Wilger Retrofit.

    Take Home

    All these recirculation options improve the status quo of plumbed boom sections with boom ends. They should be considered essential equipment on sprayers.

  • Dealing with Pesticide Shortages in 2022

    Dealing with Pesticide Shortages in 2022

    We’ve had dire warnings about possible pesticide shortages and price hikes for 2022. Price hikes are one thing. But if the products we need simply won’t be available, we have a tougher challenge.  It’s time to plan pesticide conservation.

    But first, what’s behind the product shortage?

    Emily Unglesby of dtnpf.com provided an excellent overview of the issue here and here. She said the reasons for the shortage are many-fold and came together in a perfect storm. Starting about 2017 or so, pesticide manufacturers tried to reduce the overall inventory of products to improve logistical efficiencies.  That effort was rewarded in 2019 when a wet spring in the US dramatically reduced seeded area to a low of 165 M acres. The resulting lower demand again provided incentives to reduce inventories. At the same time, US trade sanctions against China in the form of tariffs impacted production and shipment of many active ingredients to US markets. When Covid-19 happened, it affected both production and shipping of many goods, including pesticides. Container shipment costs increased sharply, and the ability to move them to and from ports was hampered. This then coincided with record seeded area in the US of 180 M acres in 2021, creating higher than usual demand. By that time, very little buffer remained in the system. The growth of Enlist E3 and Xtend Flex has placed additional pressure on glufosinate.

    Then two further events occurred. Hurricane Ida forced a shutdown of Bayer’s Louisiana glyphosate plant. And China, in late 2021, legislated a temporary 90% reduction of yellow phosphorus production in Yunnan Province in anticipation of the 2022 Olympic Winter Games. With phosphorus as a fundamental ingredient in glyphosate, glufosinate, and some fertilizers, this loss of production places significant strain on many products. The usual habit of returning unused pesticides to the retailer also became less common amidst shortage news, adding difficulty to planning inventories and demand.

    Shortages of popular herbicides like glyphosate, glufosinate, and clethodim will put demand on alternatives. Spreading out risk by implementing pre-emergent products where possible will pay dividends. But the ability to ramp up production of minor products is just as dependent on the supply chain, and these alternatives may therefore not offer reprieve if ordering is left to the bitter end. Planning ahead and staying in touch with retailers about your plans and your own inventory will assist the entire system in managing production and redistributing existing stocks.

    Safe to say products will be more expensive, and possibly impossible to obtain. Here are some things to consider to minimize the impact.

    1.Grow crops that require less pesticides. Crops which have good genetic resistance to insects and disease will be more likely to cope without a protective spray. Some crops are inherently competitive early on and give less time and space for weeds to become established. Remember that the relative time of emergence is important for crop yield loss from weeds. If crops emerge before weeds, they have the upper hand and will maintain higher yield potential. Crops that can be seeded early will prevent weeds from occupying that niche.

    A competitive crop is the best herbicide.

    2. The most powerful herbicide is a competitive crop. Use agronomic tools that favour good seedling establishment. The usual advice of seeding into a warm, firm, moist seedbed, should we be fortunate enough for the weather to cooperate, applies here. There is value in higher seeding rates to help outcompete weeds. Use fertilizer placement that favours crops, not weeds, such as side banding.

    3. Sample the spray water source and have it professionally tested. After a record drought in western North America, aquifers are low and surface waters have receded. Water quality will probably not be the same it has historically been. Use water conditioners to reduce effect of hard cations and bicarbonates. Ammonium Sulphate (21-0-0-24) at 1% w/v is a general treatment, harder water may require up to 3%.

    Conduct a water test in 2022 and condition spray water if necessary.

    4. Do not use untested mixes of pesticides with specialty foliar fertilizers. These may impact herbicide performance, or worse, result in an incompatible mix.

    5. Use the lowest label rate of product that is relevant for the pest you’re trying to control. Many products have a range of rates depending on the weed species and stage. Scout your fields and take advantage of the lower rate option if you can.

    Invest in logistics and be prepared to respond to a good spray day to get the timing right.

    6. Spray herbicides early. It’s been shown that crop plants can sense the presence of weeds before they compete for resources, causing a physiological adjustment that results in irreversible yield loss. The shorter the time that weeds and crops co-exist, the better. Also, smaller weeds are easier to control. Weeds that escape this early application will need to compete with an established crop and won’t thrive or impact yield as much.

    Smaller weeds are easier to control and may allow a lower label rate.

    7. It’s not advisable to reduce product rates from the one recommended on the label. Although label rates contain a margin for poor conditions, the risk of selecting for polygenic resistance exists. Polygenic resistance occurs when some weeds happen to be slightly more tolerant to the herbicide than the rest of their cohort. These weeds may survive a lower rate, and go on to produce seeds. If these outcross with other survivors, their more tolerant offspring will increase in relative abundance. With further such selections in subsequent generations, weeds become even more tolerant and eventually dominate.

    8. Apply the spray as uniformly as possible. Make sure the spray nozzles are within a 5% flow rate tolerance along the entire boom. If the set is older, consider a wholesale replacement. But the biggest enemy of uniform deposition seems to be turbulence created by wind and driving speed around the tractor unit. Slower wind and travel speeds help somewhat. Variable deposition means that some regions receive up to 50% more than intended, and others receive 50% less. This means weeds in the lower deposit regions may survive the application. The more variable the application, the higher the rate that is needed for acceptable control.

    Slower travel speed reduces variability of the spray deposit, limiting escapes.

    9. Use finer sprays whenever the tank mix contains a contact mode of action product (e.g., Group 1, 6, 10, 14, 15, 22, 27) or targets grassy weeds. Both situations require smaller droplets for best performance. The use of finer sprays may mean fewer hours in the day when drift is acceptable, and as a result, investment in efficient tendering and cleaning as well as overall time management pays dividends.

    10. Make efficient use of the product in the tank, preventing waste. The amount of product being discarded can range to over 10% of the total needed to treat a field, but this can be reduced to 3% with the proper steps. The following are areas where improvement is possible:

    (a) Prime the boom efficiently using sectional shutoffs or better yet, a recirculating boom. These can be primed without any spray leaving the nozzle or boom ends.

    Conserve product by eliminating priming waste with a recirculating boom.

    (b) Measure the spray mix of the last tank accurately, minimizing leftover. Consider the AccuVolume system that weighs the tank contents to the closest gallon. Tanks can be filled with the exact amount, and rates can be adjusted as the leftover becomes apparent on the last passes.

    Accurate measurement of tank volumes prevents leftovers.

    (c) Invest in individual nozzle shutoffs to improve sectional control resolution. These are part of any Pulse Width Modulation system but can also be obtained as air-actuated valves that are very affordable. Such capability is necessary for recirculating booms.

    Nozzle sectional control can save 4 to 5% product use.

    14. Consider an optical spot spray system such as the WEEDit Quadro, the Trimble WeedSeeker, or the John Deere See & Spray Select, available for 2022. These systems are “Green on Brown”, meaning they selectively spray just weeds in a burnoff or chem-fallow. This can save about 70% of the spray depending on weed density. More such systems are on the way, some even offering “Green on Green” that selectively identifies weeds among a crop. The return on investment of these systems is directly related to the pesticide cost, meaning in a year with high pesticide prices they pay off faster. If shortages of product become a reality, a spot sprayer may be the only way that some fields get treated at all.

    Pesticide shortages will not be fun. Unfortunately, their appearance coincides with higher fertilizer prices, meaning crop establishment will need to overcome that factor as well. But there are tools to minimize the impact if we’re willing to implement them. Just as necessity is the mother of invention, scarcity is the father of conservation.

  • Horsch Leeb sprayer gives people what they want with 6.300 VL model

    Horsch Leeb sprayer gives people what they want with 6.300 VL model

    Theodor Leeb started building self-propelled sprayers in Bavaria, Germany in 2001 and formed a partnership with Horsch LLC in 2011 (Horsch has been selling tillage and seeding equipment in North America since 2001 and has 17 dealers in the prairie provinces). The resulting company, Horsch Leeb Application Systems GmbH, is headquartered in Landau a.d. Isar, about 120 km NE of Munich. There they build pull-type and self-propelled sprayers, employ 350 staff, and had sales of approximately $80 M USD in 2019.

    This is no Johnny come lately to the sprayer scene.

    Their current flagship sprayer in North America is the Horsch Leeb 6.300 VL. I spent a day with Mike Wasylyniuk, Product Marketing Manager for Horsch, in Crossfield, Alberta to look it over.

    The Numbers

    The sprayer chassis holds a 1700 US gallon stainless steel tank and two 100 gallon clean water tanks for a total liquid capacity of 1900 gallons. A stainless steel Pentair Hypro centrifugal pump provides the flow to the boom, and a second pump is dedicated to the clean water tanks. The sprayer is powered by a familiar FPT 6.7 L producing 310 hp. The boom is 120’ wide in 5 articulated sections with 10’ nozzle spacing fitted with Raven Hawkeye Pulse Width Modulation (PWM). Top spraying speed is 20 mph, top transport is 30 mph. Horsch claims a dry weight of 32,000 lbs when fitted with Goodyear LSW 900 50R46.

    The Horsch Leeb 6.300 VL near Crossfield, AB October 2021.

    A central tubular frame creates room for four-wheel steer that has an interior turning radius of 3 m. Wheels are suspended via hydropneumatics linked to the frame with double wishbones. Track width adjusts from 120″ to 160″, independently, allowing different track widths front and rear without pinning an axle in place. Standing beside the front wheel, one has with easy access to fuel and oil filters, the radiator is on top of the machine facing up with an air-chuck outlet for cleaning.

    Four wheel steer improves maneuverability but more importantly, reduces front wheel plowing and allows use of common wheel track in headland turns.

    Plumbing

    Any loyal reader of Sprayers101 knows that we believe the biggest room for improvement in spraying is in the plumbing. Horsch Leeb seems aware of this. First, it does away with sight tubes on the tank and relies on a more accurate digital float that reads down to an empty tank. Tank slope position is considered using a gyro mounted at the rear of the sprayer. The tank can be filled with the solution pump or from the tender truck using 3” side or front fill locations. It has auto shutoff when a target amount is reached. As is common, the majority of valves are motor operated to allow automation.

    Fill station on right side of sprayer contains a 3″ fill connection as well as a 2″ drain

    The recirculating boom plumbing is standard North American 1” OD stainless steel to suit any off the shelf nozzle body clamp. It pressurizes from both ends when spraying and returns to tank from the outside of the boom when nozzles shut off or when priming or flushing. The recirculation can run during transport, allowing boom priming en-route to the field, or continuous flushing with a cleaning solution in the main tank on the way home.

    Recirculating boom feed and return lines are standard 1″ OD stainless steel.

    The second pump, an Italian Annovi Reverberi 185 BP diaphragm, powers the continuous cleaning function. It draws from the clean water tank and can push this water to the boom for overnight storage when the tank has solution left, or to the tank’s wash-down nozzles for a continuous clean at the end of a job. In continuous clean mode, the solution pump continues to supply the boom while the cleaning water washes the walls and dilutes the remainder. The tank and boom can be washed with a minimum of liquid, and the process is automated using cab or side monitor controls.

    Dedicated to the clean water tanks, this diaphragm pump can push water to the boom, to the wash-down
    Stainless tank with baffle

    The system even has a winterizing button that controls all the necessary valves to distribute antifreeze from the clean water tanks throughout the plumbing system in minutes. Remaining antifreeze in the tank can be returned to the drum at the fill station with a convenient camlock drain.

    Readout of tank levels and pump pressure via the external monitor. Priming, cleaning and winterizing routines are available.

    Some may gloss over plumbing paragraphs in haste, but let’s not underestimate the magnitude of these features. We are talking about a plumbing system that can prime the boom without spraying, spray the field, then spray out any remainder while rinsing the tank, air purge the boom, then rinse the boom without leaving the cab or wasting material unnecessarily. Even the system strainers have flush capability that returns any residue to a removable fine mesh filter before the liquid dumps back to the tank. Such a design saves time and money and pays in acres per hour.

    Boom

    The 120’ boom is well built and has channels for wiring harnesses that are neatly zip-tied in place. An aluminum shield covers the nozzle bodies at the front to protect them from any ground contact.  Access is relatively convenient through ports on the other side. The fitted triple nozzle bodies should be enough to suit most needs. The swing-away has a sturdy steel tube on the leading edge to absorb and deflect any sudden impact. There is no exposed plastic. The recirculating boom plumbing is stainless steel throughout except at hinges, where the rubber hose loop is protected from chafing by an additional sleeve.

    The sturdy boom is shielded where the nozzles are mounted to protect them from impact. Note the vertical hinge that permits improved contour-following.
    The break-away section has additional protection via a stainless steel pipe that absorbs and deflects impact.
    Access to the 10″ spaced nozzles and PWM solenoids is via the rear of the boom.

    The Leeb philosophy is to design sprayers that control drift at the source without reliance on extremely coarse sprays that can hamper efficiency. They’ve chosen boom height as the key variable and built the boom to make this possible. First, they needed to design a system that can reliably hold the boom low and level.

    Low, uniform boom height for drift reduction is the stated goal of the Horsch Leeb sprayer

    To that end, three pivot points are used to provide independence of the tractor unit and the boom. The first is at the centre rack from which the boom hangs but can pivot thanks to the same gyro that helps read the tank level. A sudden tractor movement due to ruts, for example, can then be compensated. The wings are the second pivot point (as it is for all sprayers), and a third point is halfway out the wings, where a hinge allows for up or down adjustments to better suit the land contour.

    A giro, visible just above the backup camera, monitors the tractor aspect relative to the boom.
    The vertical boom pivot can help prevent unnecessarily high boom ends or ground strikes.

    The height sensors have a modest look ahead slant, and the company claims that 8” boom height at 10 mph is possible. We certainly tried that in the field, and after multiple runs up and down a local field with modest knolls we did not strike ground, although the boom ends did rise significantly on occasion. The claim of such low booms will be a point of considerable testing and debate.

    Eight sensors provide boom height feedback.

    To take advantage of the low heights, narrower 10″ nozzle spacings are needed. The boom therefore has 144 nozzles instead of the usual 72, each half the flow rate. This is new territory for PWM, where the smaller tips are not as widely available. For example, a traditional 5 gpa tip at 20” and 12 mph is 03 in size, with 10” spacing this is now 015.  Smaller sizes require more attention to filtering, and they have inherently greater drift potential. This would only be a problem at the lower application rates.

    Because PWM allows for individual nozzle control, the operator can select 20” spacing, based on either of the 10” positions. This means one can spray with 20” spacing and then switch to a different nozzle simply by selecting the alternate.

    The lower boom height can offer unique advantages. The first of these is drift control. Droplets emerge from the tip at about 70 km/h, and this initial speed prevents even the small ones from drifting. The higher the boom, the more they slow down before targetting, creating drift potential. Wind speeds also tend to be lower nearer to the ground.

    Second, the beneficial effects of twin fans or angled single tips are greater with low booms. Readers will know that one of the fundamental prerequisites for successful angled sprays in Fusarium head blight (FHB), for example, are low booms. We may be in for some positive outcomes.

    The User Experience

    The Class cab has the usual creature comforts with a buddy seat, four cup holders, bluetooth radio and a phone mount. It can be fitted with any ISOBUS monitor, the one we had was equipped with the Raven Viper 4. The climb up the ladder is not as stair-like as the North American sprayers, but the treads are large and there are plenty of handholds so you can climb one-handed and bring your lunch or toddler along for the day.

    There is one native Horsch monitor that controls the chassis, wheel spacing, engine specs, speed, etc. It’s controlled using a rotary button selector like the one in many cars, a wheel that highlights items by turning, then selects them with a push. The second, an ISOBUS monitor, handles the rate control and thus creates easy compatibility with a variety of aftermarket monitors.

    The joystick is backlit and buttons can be customized. Like the Fendt stick, a push forward sets the speed and it can return to the neutral position without changing that speed. A pull back is required to slow down.  It takes a bit of getting used to. Motion can also be foot operated with a speed pedal and foot brake.  Cruise control has two preset speeds, and boom height can be raised to preset values when the master switch is shut off to facilitate a headland turn. The top two thumb buttons are Master on/off and autosteer resume.

    There is no throttle control. The sprayer decides how much throttle is needed to maintain speed, saving noise and fuel when it can. Throttling up was noticeable as we climbed hills during our test drive, returning to lower rpm as we descended while maintaining our cruise control speed.

    Some touches

    • a hand wash station at the ladder to prevent contaminating the hand-holds or cab
    • a camera focused on the centre rack nozzles that are invisible from the cab
    • cameras showing front wheel position
    • mud guards behind rear wheels to protect boom
    • Rain cover over electronics mounted on centre rack
    • A clean underbelly with good clearance and tow hooks front and back
    • Inductive (wireless) phone charging mount

    Overall Impression

    It’s clear that Horsch Leeb wants to succeed in North America. I’ve hardly ever seen a company so bent on delivering what the market wants (for familiarity and compatibility) while delivering what it knows they need (like plumbing and drift control). Spending the day with Mike I learned how quickly the engineers and fabricators implemented his suggestions at the factory. That is perhaps the most promising aspect of all, a company that listens to its customers and continually evolves its product as a result.

  • The Ideal Sprayer (an open letter to sprayer manufacturers)

    The Ideal Sprayer (an open letter to sprayer manufacturers)

    Today’s sprayer has to excel at a lot of things. It has to have capacity and low weight. It has to go fast but be comfortable. It needs wide booms that stay level over complex terrain. It has to deliver the right spray volume at the right spray quality for the job. It has to be easy to fill and easy to clean. And of course, it has to be reliable, affordable, and come with dealer support.

    We’ve definitely made progress in many of these areas. But the overall package still leaves lots of room for improvement and doesn’t address some issues that are of importance to applicators. Is it time for a reset?

    Let’s say cost is no object. Here’s where I think the industry could go.

    Focus on spray delivery

    Spraying is done to protect crops. We need to do it without harming the environment while being economical with the inputs. These three tenets make up the Application Triangle, sometimes known as the 3 Es of spraying: Efficacy, Environment, Efficiency. The triangle represents the need for balance. A gain in one or two areas often requires a loss in another. That’s why there has never been a so-called “silver bullet” in spraying.

    Priority 1: Only spray when and where required.  Site specific treatments and IPM have been slow to make their way to the spraying world partly because of the low cost of inputs, but also because of difficulties defining and mapping areas that require different rates or products. The machine learning revolution is changing that. Green on Brown or Green on Green sensing can do more than save inputs. They can generate maps that document the change of weed patches over time, identifying priority areas and threshold densities and flagging problems early.

    Priority 2: Integrate air assist. Air carries small droplets towards the target, protecting them from displacement by travel-induced or ambient winds. Once there, air can improve target interception and retention. It has to be done right, though, as improper adjustment can result in the opposite outcome. The reason it’s high on this list is because it improves efficacy and environmental protection at a modest cost.

    Priority 3: Improve droplet size control.  Nozzle design has improved, but the overall range of spray qualities that is achievable for any specific nozzle remains narrow. Sprays can be made finer or coarser with spray pressure, but this has implications for pattern uniformity. Twin Fluid nozzles currently offer the widest range of spray qualities, allowing one nozzle to do it all. We simply need greater droplet size flexibility on the spray boom.

    Priority 4: Use nozzle-specific rate control.  At minimum, a sprayer needs a system that allows for individual nozzle rate control within a wide window, say 4:1. This allows consistent dosing over a wide speed range, turn compensation, or local adjustments to dose for specific (sensed) canopy conditions. By layering direct injection at the nozzle on top of this, the sprayer can change rate and volume independently. Being able to spray the right amount in the right spray quality at the right volume, where needed completes the opportunity created by pest and canopy sensing.

    Create better infrastructure

    The backbone of the sprayer, the frame, drivetrain, boom, tank, pump, and plumbing, are responsible for carrying and delivering the spray liquid. Poor management of these variables results in an unproductive, heavy machine.

    Priority 1: Prepare booms for future.  A limiting factor in sprayer performance is boom width and stability. Consistent and low boom heights are the cornerstone of good application, ensuring uniform distribution, reducing drift potential, and improving targeting within the canopy. But perhaps as importantly, stable booms are essential for accurate optical spot spraying and any other sensing tasks that will rise in importance. Set a standard for sway, say target height plus or minus 10 cm along the width of the boom, 90% of the time. Do the same for yaw. Accommodate brackets for sensors and wiring harnesses when designing the boom fold.

    Priority 2: Improve plumbing.  Poorly executed sprayer plumbing causes waste and decontamination headaches. Although rubber hoses attached to plastic fittings provide a very versatile and generic building block, they generate and hide countless niches in which pesticide mixtures or active ingredient residue can accumulate. A simplified design that incorporates more engineered stainless steel tubing, smooth directional and dimensional transitions, interior surfaces that don’t accumulate residues and generate more efficient flows – all these would improve many aspects of the spray operation. It needs to be goal oriented – i.e., zero waste in priming and cleaning, guaranteed decontaminated after a rinse cycle. Draining on the ground should not be necessary.

    Priority 3: Save weight. Weight causes compaction and eats fuel. Advanced materials or techniques can save weight while preserving strength. Savings can be applied to capacity. We need to explore advanced materials and trussed or exoskeletal designs (see “Aerodynamics”).

    Priority 4: Consider aerodynamics in chassis and boom design. Wind blowing past a tractor, tank or boom, or counter-rotating air from wheels creates turbulence that displaces small droplets within it, reducing uniformity. Cleaner air makes it easier to use smaller droplets, easier to implement air assist or any other drift-reducing technology. This is no small task, as air can come from any direction. But as units become larger and travel faster, this effect can’t be ignored. Monocoque designs that use aerodynamic exteriors to carry machine weight may provide an answer.

    Provide quality control

    Spraying can be a guessing game, hence the terms “Spray and Pray”. We don’t know the outcome for days or weeks, depending on the mode of action, and by the time the result is known, it is too late to do anything if it’s unsatisfactory. But we can do better in assuring some sort of standard.

    Priority 1: Confirm pressure, flow, and patterns at nozzles. The average sprayer has one flow- and one pressure-sensor. It can confirm the flow of the entire spray boom but cannot do that at the nozzle level. PWM has helped, by inferring flow from duty cycle. But actual liquid flow, and its pressure, remain unverified at the spray tip. A visual inspection of the pattern is necessary, and this is not only impractical but also wasteful and potentially hazardous.

    Priority 2: Characterize canopy. If we knew the crop canopy was dense or sparse, we could adjust the water volume or rate of the product accordingly. LiDAR (Light Detection and Ranging) can characterize the physical structure of an object that would indicate density or porosity for which a dose (or droplet size, or air) adjustment may be necessary. This is not some future technology. The iPhone 12 Pro has it. Even RGB image processing could do something very similar.

    Priority 3: Confirm coverage and drift.  Say we’ve characterized the canopy and adjusted the atomization to suit. Is it having the intended impact? We will need a way to verify that the settings of the sprayer result in the required canopy penetration and coverage, even drift, on-the-go. We would need sprayer-mounted sensors that see spray deposits or an airborne spray cloud. The verification must be fast enough to make corrections during the spray operation. This kind of quality control provides the feedback loop to the first priority, spray delivery. It creates a perfect environment for machine learning and continuous improvement.

    Priority 4: Improve user interface.  The complexity of modern equipment monitors is great if you’re familiar with their features. But if you’re a new user or less comfortable with layers of screens and buttons and warning beepers, navigating the monitor can be a game stopper. Can we have beginner modes? Or a system where the monitor more actively engages with the user, asking questions or reminding a novice of key settings? The friendliness of the interface is a sleeper issue, it seems less important at first look but can over-ride many equipment features because of the power of a positive user experience.

    I challenge sprayer manufacturers to conceptualize and show us the ideal sprayer they’re working towards. The perfect unit may never reach us, as this proposal is rife with technological and cost barriers. But it is nonetheless important to identify priorities and identify possible ways to meet them. As we creep towards the solution with incremental improvements, recall that its not the size of the step that matters, it’s the direction.

  • Putting a Number on Pesticide Waste

    Putting a Number on Pesticide Waste

    Waste (noun): an act or instance of using or expending something to no purpose.

    In agriculture, environment and economy are intertwined. Producers strive to obtain the maximum return on their inputs. They study incremental returns and avoid applying more inputs than necessary, especially if conditions don’t warrant it.  The financial incentive is powerful, and waste is a four-letter word. This applies to seed, fertilizer, and pesticide. Pesticide labels identify the rate needed to obtain the desired result, and there is no incentive to over-apply. In fact, it’s illegal.

    But there are plenty of other places where applications incur waste. As with time efficiency, it’s a good idea to identify where this waste occurs, and the only tool needed is a sharp pencil.

    When might we incur waste in the spray application process?

    • Mixing more than we need because we don’t trust the flow meter or the tank gauge entirely, or don’t know the exact field size.
    • Priming the boom before the first swath.
    • Overlapping due to curvy terrain and coarse sectional control.
    • Spray drift away from the intended swath.

    How big are the losses?

    Let’s say we have a clean sprayer and need to spray 160 acres before moving to a new crop and product. We plan to apply 10 gallons per acre and have a 1,200 gallon tank with a 120 foot boom. That means we need 1,600 gallons of spray mix in total.

    Once we’re at the field we prime the boom. Each sprayer is different, but depending on operator experience, 30 to 50 gallons are usually needed to push product from the tank to the last nozzle. Only part of that is lost to the ground, as boom sections can be shut off as soon as product has reached every nozzle of that section. We’re assuming 0.2 gallons per foot of boom is lost.

    Spraying itself is relatively straightforward. Swath and sectional control handle the overlaps, but in less ideal terrain, double application is known to account for 4 to 5% of the area to reach non-square parts of the field. This is even more likely when the outer section is 10’ or more. Early turn-on of the boom prior to leaving the headland, to allow boom to reach operating pressure, adds to this.

    Air-activated shutoff for individual nozzles reduces section size at a reasonable cost.

    With an average nozzle, we can expect about 2% of the product to airborne drift. Most airborne won’t return to the ground within the field borders, so it’s a complete loss.

    Most of the spray that travels more than 5 m after leaving boom stays airborne and should be considered a total loss from the field.

    As we finish, the pump will draw air before the tank is empty due to sloshing or foaming, and a 50 to 60 gallon remainder may not be unusual. This simulation has assumed 5% of tank volume remains.

    We also need to purge spray from the boom at cleanout, consuming approximately 0.4 gallons per foot of boom. This occurs after the field is completely sprayed and is therefore considered waste.

    So how does this add up? The following table shows the approximate losses associated with five setups.

    Table 1: Spray mix losses during a sprayer operation. Setup 1 = baseline, Setup 2 = low application volume, Setup 3 = baseline with recirculating boom, tank level monitor, and low-drift nozzles, Setup 4 = large area between cleaning, Setup 5 = large area with recirculating boom, tank level monitor, and low-drift nozzles.

    In the first scenario, we spray just 160 acres at 10 gallons per acre. Priming the boom with 0.4 gallons per foot (allowing for all associated feed lines) consumes 48 gallons, but only wastes half of that, or 1.5% of the total volume needed for the field.

    Four percent overlap consumes another 64 gallons.

    If we have 5% of the tank volume left over, that’s 60 gallons. That amount is so small it doesn’t even register on the sight gauge but nonetheless it represents another 4% of the total sprayed amount.

    Upon cleaning the boom, we need to push the spray mix out of all the  plumbing after the pump, as it has nowhere else to go. At an assumed 0.4 gallons per foot, that’s another 48 gallons or 3%.

    If we add to that a conservative 2% drift loss, it sums to a surprising 14% of the total spray volume. For those that use lower water volumes (the second scenario), the volumetric losses are slightly less, but their proportion is higher, now accounting for 23% (!) of the total spray mix.

    In the third scenario, let’s assume we use a recirculating boom that returns the initial prime volume to the tank, eliminating any waste. We’ll also upgrade to individual nozzle sectional control, reducing overlap to 1%. And, since we want to know exactly what’s left in the tank, let’s invest in an AccuVolume system to precisely monitor tank volume. This allows us to make small rate adjustments up or down to be sure as much of the mixed product goes onto the sprayed swath as possible.

    Recirculating booms allows the spray mix to pass through entire length of boom without being sprayed, saving waste during priming and allowing waste-free boom rinses.

    When the sump begins to empty, we can introduce some water from the clean water tank to push the last of the mix to the boom (a continuous rinse system makes this easy).

    An AccuVolume sensor shows the exact volume left in the tank at any slope position and with 1 gallon resolution, allowing greater accuracy when filling and emptying.

    We’ll assume our sump waste is now reduced to 12 gallons. We still need to dispose of the content of the boom somehow, so the recirculating boom offers no saving there. But let’s also add better low-drift nozzles to reduce drift by 50% (now 1% total volume). Total loss is now just 6%.

    Low-drift nozzles such as this AirMix (Agrotop) SoftDrop reduce airborne drift by 50 to 90%.

    The last two rows in the table repeat the first and third scenarios for a larger sprayed area (1000 acres) before a tank cleaning is needed. This doesn’t change the magnitude of the volumetric loss, but reduces its proportion. Percent loss is down by a factor of two from the 160 acre interval, to 3 to 7%.

    Experienced operators might cheat the system a bit by mixing the required pesticide with some extra water to make up for the plumbing waste. Doing so prevents extra pesticide from being consumed, but it doesn’t reduce the inherent inefficiency.

    Lessons

    This exercise suggests that waste from spraying is probably higher than we assumed. If we average the scenarios, there is 10 to 15% waste. At, say, $200,000 spent on pesticide for a single spraying season, that’s $20 – $30,000 worth of product and water hauled that ends up where it doesn’t belong. Beyond the time and money, there can also be environmental consequences depending on how that waste is treated.

    There are some things that can be done.

    • Know the exact area of the field to be sprayed.
    • Study your sprayer plumbing and consider improvements such as recirculating booms and continuous cleanout.
    • Improve monitoring of tank content to allow lower remainders.
    • Consider individual nozzle shutoff to improve sectional control. These are part of Pulse Width Modulation (PWM) systems, but can also be achieved with less expensive valves.
    • Plan spray operations to minimize the amount of product changeovers.
    • Consider direct injection.

    The return on investment for plumbing improvements can be high and result in considerable future savings over the life of the sprayer. It’s worth thinking about.

    Spray Waste WorksheetDownload