Category: General Operation

Articles that discuss general field sprayer operation and productivity factors

Do Labels Help us Apply Pesticides Properly?
It happened three times this spring. As is often the case, I was contacted by growers who wanted help with herbicide application. In most of these calls, the discussion revolves around the proper choice of nozzles for a specific task, perhaps some questions on spray pressure, water volume and travel speed.
But these three were different. Instead of being seasoned applicators, all three were new to the business. And more importantly, they had done their homework by looking at product labels before calling.
Labels give us important information on product rates, crop and weed staging, mixing order, sprayer cleaning, and personal and environmental protection. They’re very valuable there. But they also provide application information, and that’s where the problems begin.
Perseverance Required
I have to commend my three clients: they showed great tenacity by actually finding application information on a pesticide label in the first place. This document is so mired in legalese protectionist language at the front that it discourages all but the most persistent.
And often, the application information comes in several parts, interspersed among other information. Mixing instructions. A little later, application. Somewhere nearby, buffer zones. Another paragraph for cleaning. Rainfastness? Keep looking.
It forces the reader to skim through the document, hunting for relevant information.
But once my clients found application instructions, they obviously questioned if they should believe it, or else they wouldn’t have called. The application statements on many labels, simply put, are from long ago, and it’s obvious.
Consider the following two label excerpts, the first from a product initially registered in the mid 1980s and still available, the second from one registered about 30 years later:
1980s:
Application should be made using a minimum of 55-110 litres of water per hectare, at a pressure of 275 kPa, or 310 kPa if using check valves, and at a ground speed of 6-8 kph.
The use of 80° or 110° flat fan nozzles is recommended for optimum spray coverage.
Do not use flood jet nozzles, controlled droplet application equipment or Sprafoil® equipment.
Application of the spray at a 45° angle forward and higher water volumes will result in better spray coverage and penetration of the crop canopy.
Uniform, thorough coverage is important to obtain consistent weed control. Higher water volumes should be used under dense crop and weed canopies to ensure thorough coverage of the target weeds.
2010s:
Apply in a spray volume of 46.8 – 93.5 L/ha unless otherwise specified in tankmix partner section of this label – at 207-345 kPa (30-50 PSI) pressure to ensure proper weed coverage.
Flat fan nozzles of 80° or 110° are recommended for optimum coverage.
Do not use floodjet or controlled droplet application equipment or Sprafoil® equipment.
Nozzles may be oriented 45° forward to enhance crop penetration and to give better weed coverage.
Uniform, thorough coverage is important to obtain consistent weed control. Higher water volumes should be used under dense crop and weed canopies to ensure thorough coverage of the target weeds.
Thirty years apart, but remarkably similar.
Crop protection companies spend about 10 yrs. and $250 million to produce a new pesticide and register it for use. Having made this commitment, it would be most useful to see a small further investment to provide current application information that is relevant to applicators.
After all, these applicators purchase the active ingredient to provide a return on this multi-million dollar investment, to the tune of about 2 billion dollars per year in Canada alone. They deserve good application information.
Imagine this scene:
“Doctor, thank you for this new high tech pharmaceutical engineered to help me with my serious illness. How should I take it?”
“Not sure. Here, read this cough syrup label I found in my drawer. Should be pretty close.”
It’s clearly ridiculous
Let’s dissect these labels to see how they could be improved.
Flat fan nozzles of 80° or 110° are recommended for optimum coverage…
Our sample labels refer to what we assume are conventional flat fan nozzles. While popular in the 80s, these have all but disappeared from sprayers over the course of the past 20 years or so. We haven’t recommended them since then because they drift too much. They’ve been replaced by low-drift nozzles, either pre-orifice, or air-induction.
Nozzle fan angles are now generally 110 degrees or more, and frankly, the difference between 80 and 110 degrees is not that important. What’s important is proper overlap, achievable with a visual assessment followed by boom height and pressure adjustments. Unfortunately the label is silent on that.
Application should be made … at a pressure of 275 kPa, or 310 kPa if using check valves…
A nozzle’s recommended operating pressure depends on the specific nozzle model and on the spray quality (average droplet size) required. With literally many dozens of nozzles now available to each applicator, general pressure suggestions are likely to be wrong, and are more of a liability than a help. And they force label non-compliance when over-ruled by a nozzle manufacturer’s recommendations.
Speaking of spray quality, growers crave to know at what spray quality a product should be applied for best performance and lowest drift. Some labels refer to spray quality (e.g. “apply with a Coarse spray”), but this is with reference to spray drift and buffer zone distances, not efficacy, and that distinction is not made. Knowing the right quality for efficacy would help applicators choose the right nozzle and pressure to meet that criteria.
Higher pressures if using check valves? Nobody has brass screens with check valves anymore. Sprayers have had modern diaphragm check valves for a generation, and those don’t produce pressure losses.
And we all know that six to eight km/h is hardly a common speed these days.
Do not use floodjet or controlled droplet application equipment or Sprafoil^® equipment
Sprafoil nozzles have not been produced in Canada for about 25 years, in fact their manufacturer is no longer in business. Controlled droplet atomizers, while becoming more popular again on aircraft, were last seen on ground sprayers in the 1980s. Even then, total installed numbers were probably in the single digits.
As for FloodJet nozzles, those went out of style for herbicides in the late 70s, and were replaced by the very successful TurboTeeJet nozzles shortly after.
Nozzles may be oriented 45° forward…
Nozzles are rarely tilted 45 degrees forward for herbicide application anymore. Maybe that’s because spray booms aren’t built that way today, or because modern booms on self-propelled sprayers are now about 30” (75 cm) above ground, and we travel at about 15 mph (22 km/h). So the forward tilting, though shown to be effective for grassy weeds at 5 mph (8 km/h) and 20” (50 cm) boom heights, as researched in the 1970s, isn’t relevant for herbicides with higher booms.
Uniform, thorough coverage is important to obtain consistent weed control.
Statements advocating for good coverage are nice, but they aren’t useful. Everybody knows we want good coverage. What applicators need to know is how they should measure coverage, and what good coverage actually is. Can we use water-sensitive paper? How much of the target should be covered? How many droplets should be in each square centimetre? How can we measure that in the field, right now? How does it depend on the crop canopy, on weed stage, and on spray quality? The more information an applicator gets, the higher the chance of success.
Apply in a spray volume of 46.8 – 93.5 L/ha…
The only statement that survives our little examination is about water volume. Water volume is important. But even there we have a problem. The volume is in L/ha. This is useful in some parts of Canada, but not in the west, where producers communicate primarily in US gallons per acre. And in the west, provincial guidelines have generated this odd hybrid of L/acre, which few people use for spray volume. But 46.8 to 93.5 L/ha? How is that level of precision justified? (I know that this is a conversion from 5 and 10 US gpa…so why not just say so?)
A Solution
The problem with having outdated or impractical information on labels is that it creates disrespect. Since labels are documents enforceable by federal law, applicators want to comply. At this time, they can’t, and probably shouldn’t, if they want to do the job right.
A vision for a good label should be one that respects the needs of the applicator. Such a label:
- places the information that applicators need at the top;
- is updated regularly to reflect modern practice and useful advice;
- helps a new applicator work out how to apply the product with any equipment;
- identifies a spray quality that offers good coverage and low drift;
- makes reference to research that supports variations in the application guidelines;
- is available electronically, readable on a mobile device, i.e., not pdf.
This label would protect the environment and bystanders, and would foster better pesticide performance.
This label is easy to generate.
This label would be read by applicators.
What’s it going to take?
Additional:
This article created a great deal of discussion. We decided that if we were going to point out issues with the current labelling system, we should also propose a way forward. Read about our Label Summary Sheet proposal.
November 7, 2018
Smart Spraying Tips and Tricks
This 2018 article was written by Victoria Berry for the Ontario Grain Grower.
In the era of social media and keyboard warriors, it’s easy to feel like someone is always watching and ready to force their opinion on the world. The “tweet first, think later” mentality often adds to misinformation, and worse, it can leave science as a bystander — especially when it comes to modern farming techniques.
Farmers feed the world and they need to ensure they are growing high quality, high yielding crops. One of the most important elements of protecting high-quality crops is spraying. As farmers and custom applicators become more innovative and more knowledgeable about spraying techniques they have to strike a delicate balance, according to Jason Deveau, Application Technology Specialist with the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA).
Deveau recently sat down for a Q&A session to discuss tips and tricks for smart spraying, understanding drift, and how important it is for farmers to share smart practices and be champions to others in the community.
V.B.: WHAT ARE SOME OF THE KEY AREAS TO SPRAYING? WHAT ARE THE TOP MUST-DOS?
J.D.: First and foremost, the laws of physics have never changed. We may present the facts in different ways to help people understand, or to make them more accessible, but when it comes to spray coverage and spay drift, there are three speaking points:
1. We want farmers to use the largest droplet size they can without compromising coverage.
2. We want the boom at the lowest practicable height to the field.
3. We want farmers to adjust their spraying practices to match weather conditions, and know when spraying isn’t advisable.
V.B.: OK. LET’S START FROM THE TOP. WHY AND HOW DO FARMERS CHOOSE THE LARGEST DROPLET SIZE?
J.D.: Droplet size is an effective tool for combating physical drift. Larger droplets have more mass, which means they are more likely to fall rather than be carried away. But, for a given rate, the number of droplets a nozzle produces decreases as average droplet size increases. It’s the same amount of pie no matter how many slices.
Fewer droplets might compromise spray coverage, particularly when targeting small weeds or when using a contact pesticide in a dense canopy. The answer is to use more volume to bring the droplet count back up, but that means more refills for the sprayer operator, which is time consuming. A good operator is always considering the balance between drift potential, coverage, and efficiency. Even with sophisticated technologies, these considerations always lead to nozzle choice.
Traditionally, a grower would choose a nozzle based on the desired rate (e.g. gallons per minute) for a given pressure. As the sprayer changed speed, this would lead to over — or under — application. So, for convenience and consistency, most growers use rate controllers that monitor speed and auto-adjust the rate using pressure. But pressure also changes droplet size and spray pattern. Patterns can collapse at lower pressures (say <30 psi) and average droplet size decreases as pressures increase. You can see that droplet size wasn’t really on the radar. Pulse-width systems have changed this, but they are still few and far between.
And even if a grower chooses a nozzle with a coarse spray quality, they may be surprised to learn it still produces some fine droplets, too. Look at a bell curve. That’s how a nozzle is rated for droplet size — a lot of average sizes in the middle, and then a few smaller or larger sizes. A coarse nozzle does not make you bullet proof; there will still be some drift. That is why we always observe weather and time-of-day restrictions and adhere to the buffer zones that appear on the pesticide label.
V.B.: HOW DO LOW BOOMS IMPACT DRIFT AND WHY DO SOME FARMERS RESIST THIS ADVICE?
J.D.: Imagine holding out your arm and dropping a feather. It will move a ways downwind before landing. Now climb a ladder and do the same thing — it goes considerably further. It’s exactly the same for water droplets. To add insult to injury, releasing spray from a higher point also prolongs evaporation, making it even smaller and exacerbating the problem. And if that weren’t enough incentive to lower booms, the high booms create inconsistent spray coverage, undermining the whole reason for spraying in the first place.
The resistance to low booms comes from the desire to drive fast. North American booms sway and yaw, even with boom leveling systems. Higher speeds may get the job done faster, but it requires most farmers to raise the boom to prevent it hitting the ground. It may seem counter-intuitive, but there are several ways a farmer can slow down, drop the boom, and spray more acres in a day — it just requires them to look at their spray operation differently. A great deal of time is spent filling, idling, turning, and travelling between jobs. It’s been demonstrated that saving time on sprayer-related tasks has a big impact on efficiency — more than simply driving faster.
V.B.: HOW DO YOU KNOW WHEN THE WEATHER IS RIGHT FOR SPRAYING?
J.D.: Everyone knows the obvious cues. If your hat blows off, it’s probably not the time to spray. But, we’re learning that calm conditions may contribute to chemical trespass even more than wind. There’s no hard and fast rule, but three kilometres an hour to 10 kilometres an hour winds are a good range.
In calm weather, you may find yourself in a thermal inversion, which does not allow fine particles (or volatiles) to disperse and ground. Instead, they hang in a layer of undisturbed air, either moving downhill like water, or eventually moving in an unpredictable direction when the wind picks back up. It’s suspected that this phenomenon has played a significant role in the off target crop damage issues in the U.S. in 2016 and 2017.
In a very telling demonstration, an Ontario agrichemical rep showed that the smoke from a smoke bomb (representing pesticide vapour) travelled 1.7 kilometres during an inversion. In another demo, he showed it moving back and forth across the same field for hours after the application. Learning how to recognize a strong inversion, and knowing when there is too much or too little wind will require a different way of thinking, but will greatly reduce the potential for chemical trespass.
V.B.: WHAT OTHER PRACTICES SHOULD FARMERS BE AWARE OF TO COUNTER DRIFT?
J.D.: There are a lot of other considerations, but let’s highlight two.
First – Downwind neighbours (residential and agricultural) can take actions based on your spraying schedule. If there’s a possibility of chemical trespass, it’s a courtesy to let them know your plans, or at least make spray records available and be prepared to answer questions. Quite often explaining what’s happening prevents them getting misinformation elsewhere. It may sometimes be a nuisance, but educating others is part of maintaining the public trust. Ontario farmers are experienced and certified and, frankly, the industry needs them to help educate people on all the good work being done.
Second – Night spraying. Please stop. Time is short and weather can force us to take opportunities where we find them, but calm, clear nights represent the highest potential for a strong thermal inversion. Knowing the weather conditions that affect product performance (for better or for worse), minding pollinator presence, knowing what’s downwind, and STILL following integrated pest management means there seem to be fewer hours left to spray. But, it’s really a matter of understanding which of those factors trumps the others in the decision to spray, or wait. It requires today’s farmer to play an active role when it comes to spraying.
V.B.: YOU MENTIONED PUBLIC TRUST. HOW WILL SPRAYING AND PUBLIC TRUST IMPACT FARMERS’ BUSINESSES?
J.D.: We talk about soil, stewardship, and environmental sustainability. But at the core of all those important considerations is the customer driving those agendas. We are getting close to the day (if we’re not there already) where the grocery store dictates farm practices.
Many broad acre farms are still self-regulating to a large degree. They do their best to maintain high standards for safety, transparency, and record-keeping. But, as specialty crop and livestock operations already know, we are moving towards tracing the history of a farm product from the customer all the way back to the seed. Farmers should adopt best practices proactively, before they become mandatory.
So, the level of attention on field crops is more acute than ever before. Many are not used to being under the public microscope. Customers are asking when, how, and what was it sprayed, and they want to know the weather and cleaning practices that were followed. We need to have those answers ready to show what we’ve always known — that farmers are self-aware, are stewards, and are responsible partners in public health and safety.
So spray like everybody’s watching… because they are.
April 24, 2018
Agrifac Launch – Endurance II is a High Tech Offensive
Agrifac shunned the Agritechnica show last year, choosing instead to introduce its latest Condor Endurance II alongside a wide range of high-tech controls at the opening of its new factory at Steenwijk, in The Netherlands.
Booms up to 80m wide can be tested in the new 14,000m² factory, which Agrifac has constructed on its existing site at Steenwijk in the Netherlands.
Agrifac has seen quite remarkable growth in recent years, no doubt the result of investment from its owner – the sprayer specialist group, Exel Industries – which bought the struggling manufacturer in 2012.
Since then, sales of self-propelled sprayers have rocketed – from 20/year in 2008 to more than 200 today. The new factory is currently building a machine a day and Agrifac is now looking to boost sales further by expanding operations in Australia, North America as well as central and eastern Europe.
Sales of Agrifac self-propelled sprayers have risen from 20/year in 2008 to more than 200 today. Its new factory has the capacity to build one machine every day.
Indeed the impressive new, architect designed factory is set-up to test booms up to 80m (~262 ft) wide, which is a massive jump from its current 52m (~170 ft) maximum. Unsurprisingly it’s looking at carbon fibre to reach these widths.
While not launched officially, Agrifac made no secret of this at the open day, showing a ‘hybrid’ with carbon fibre outer sections fitted to the existing steel one. While there are few details about this prototype, it uses a lattice-work construction, with the nozzles mounted at the top of a triangle.
Targeting greater precision
Under the banner of ‘Need Farming’ Agrifac is promoting a range of systems to apply products with ultimate precision. Top of the technology tree is AiCPlus, which identifies individual plants and applies a specifically-tailored product rate – on the move.
By the way, Agrifac explains AiC is pronounced ‘I See’, with the AI an abbreviation of Artificial Intelligence.
Cameras, mounted along the boom, scan 3m (~10 ft) wide bands of crop in ‘real time’ and, use special software algorithms to interpret what they detect. This could be individual weeds, diseases or pest damage.
Ultimate spraying precision and control delivered by AiCPlus, which uses boom-mounted sensors to identify areas down to 50cm and deliver targeted treatments with single nozzle accuracy.
Applications are targeted using control to single nozzles, which are operated by Pulse Width Modulation (PWM). This enables the nozzles to be turned on/off at up to 100 times/sec, allowing the system to not only vary and apply the dose for the target, but also maintain the correct droplet size for the product.
Solenoid valves switch nozzles on/off up to 100 times/sec and maintain the application rate without changing pressure. The system also reduces flow to the inner nozzles and increases it to the outside automatically during turns.
To accomplish this degree of precision application, Agrifac has introduced a range of other new technology. Along with the sensors and single control there is another new system, DynamicDosePlus (here’s a smartphone video), which implements control down to a resolution of a single nozzle.
Pesticide rates, rather than just the total application volume, are changed on the move using SmartDosePlus. And to ensure products are applied accurately there is StrictSprayPlus, which includes turn compensation.
Precise prescription maps
For precise applications, without using AiCPlus on the move sensing, Agrifac has developed DynamicDosePlus. This, it claims, is the first system to create application plans to one nozzle precision.
As well as planning applications it also executes the operations, not only controlling applications, turning nozzles on/off, but also varying the pesticide rate between 0-100%. To do this AiCPlus requires high precision prescription maps.
Agrifac has developed a completely new high resolution system for creating prescription maps and executing the instructions on machines equipped with single nozzle control.
Mixing on the move
With AiCPlus varying pesticide rates on the move and to one-nozzle precision, Agrifac says it is difficult, or even impossible, to predict the chemical concentration required before application.
To overcome this, it has developed its SmartDosePlus direct injection system. Just clean water is held in the spray tank with the concentrated chemical stored separately. According to required pesticide rates detected by the sensors or stored on the map, the system’s software then meters the precise quantity of active required for the specific area and mixes it ahead of the boom.
The valve system and full boom circulation and priming ensures each nozzle receives the correct mix. It also doesn’t matter how many nozzles are in operation at the time.
It also enables other active ingredients to be added to treat certain areas and turned off when the patch is passed. Similarly, pesticide rates can be reduced dramatically or even stopped completely in environmentally sensitive areas.
Another big advantage of carrying just clean water in the tank, adds Agrifac, is it significantly cuts cleaning time and the amount of washings. This not only speeds up turnarounds between products, but can also help reduce the risk of cross contamination when working in sensitive crops.
The right rate and droplet size
As well as single nozzle control, StrictSprayPlus also provides application volume control that is unrelated to pressure, which maintains the droplet size regardless of changes in forward speed or pressure.
Automatic controllers normally set the application volume, according to speed by varying the pressure. In most cases as speed rises the droplet size reduces, increasing the risk of drift. As the pressure falls the droplets get larger and this may have adverse effect on efficacy.
Pulse Width Modulation overcomes this by using solenoids to turn the flow to the nozzle on/off up to 100 times/sec to maintain the correct application volume. The pressure is unaltered, so the droplet size remains the same.
StrictSprayPlus nozzle control also delivers turn compensation – to maintain the correct application volume when spraying around corners. As the sprayer turns the nozzles on tip of the outside boom move considerably faster than those on the inside of the turn.
With a fixed application volume, this results in under-dosing on the outside and overdosing on the inside. Agrifac says its system detects the speed differences and calculates the rate required for each nozzle across the boom.
But, experts warn, it’s important to note that PWM currently does not work with many of the popular Air-Inclusion (AI) nozzles in use today.
On the level
Regardless of the other technology on board, setting and maintaining the best boom height is crucial to maintaining spray efficacy and cutting drift.
For its new StrictHeightPlus auto-boom height control, which works in conjunction with the BalancePlus and variable geometry on its J Boom, Agrifac has developed new ‘wide view’ sensors.
Three sensors are fitted into four separate clusters, mounted across the boom that, it adds, scan a wider area than other systems. This is said to provide a better overview of the crop as well as help to distinguish between irregularities, misses and tramlines, which can affect performance.
A new auto-boom height control system, developed in house, uses three sensors in a cluster to scan a wider crop area. Four clusters are used on the boom.
The system is also now fully integrated into the firm’s own EcoTronic terminal, eliminating the need for another box in the cab.
More power and control for Endurance II
The Endurance II is powered by a 420hp engine and is equipped with a new, advanced control panel and joystick.
The sleek new EcoTronicPlus II joystick and touch-pad clusters commonly used controls into areas, providing finger-tip control of operations.
While the manufacturer sticks with the Claas Vista cab, inside operators will find a sleek new, modern control panel. Called EcoTronicPlus II, it is designed solely for use on a sprayer and incorporates a stylish joystick ahead of the armrest pad, which is surrounded by touch buttons.
These are accompanied by a single touch-screen, which is used for both the sprayer and the GPS-controlled equipment, such as section control, mapping and even road navigation. The screen changes automatically to display only information that is required for the current operation.
Elsewhere the Endurance II retains familiar equipment such as the existing StabiloPlus chassis, GreenFlowPlus multi-stage centrifugal pump and spray system as well as the 8,000 litre (~2,110 gal.) capacity tank and booms from 24m (~80 ft) to 55m (~180 ft).
Be sure to check out Pro Operator Magazine’s Facebook page and stay tuned for their new website!
April 5, 2018
Sprayer Turn Compensation
Turn compensation is a feature in pulse width modulation (PWM) sprayers in which nozzle output matches the boom’s speed during a turn. When turning, the inside and outside of a boom travel at different speeds, resulting in over-dosing on the inside and under-dosing on the outside. Read about PWM systems here, here, and here.
The degree of the problem depends on the inside turn diameter. Clearly, the tighter the turn, the more severe the over-and under-dosing. The ability of a PWM sprayer to compensate also depends on the turn tightness, as well as the Duty Cycle (DC) the system is operating at during the turn.
In the above example, a 120 ft boom makes a turn around an object with a 60 ft diameter. Assuming a 12 mph speed and an application volume of 10 gpa, the inside of the boom travels at 4 mph and applies 30 gpa, or 3x. On the outermost nozzle, the speed is 20 mph with an application volume of 6 gpa, or 0.6 x. A sprayer operating at 60% DC would be able to correct the application in this turn by operating at 100% DC on the outside and 20% DC on the inside.
But completing the turn at other DCs may be problematic. In this case, lower sprayer DC would require the inside DC to operate below 20%, which may not be possible, depending on the system. Conducting the turn at higher DC would prevent the outer boom from meeting the flow requirements, resulting in under-dosing.
Optimizing the benefit of turn compensation requires the operator to enter the turn at a DC that meets the objectives. Is it more important to prevent under-dosing of the outside perimeter? If so, slow down in the turn (reducing DC) and maximize the extra capacity at the outside of the boom, possibly at the cost of over-dosing the inside.
The agronomic benefit of turn compensation is to provide sufficient pesticide dosage where it’s needed. It’s been reported that repeatedly applying sublethal herbicide dosages at the same site can lead to the development of polygenic resistance in some outcrossing weed species. These areas are likely to occur at the outside boom location of a permanent landscape feature that the sprayer moves around year after year.
Turn compensation is a valuable feature in all agricultural operations where input distribution uniformity is important. Spraying is no exception, and PWM makes it possible.
April 3, 2018
ExactApply Primer
ExactApply is an application system capable of PWM, introduced by John Deere in August, 2017, with its first customer field season in 2018. ExactApply offers several unique features that differentiate it from the existing systems. Here is a brief description of its major components and capabilities:
Nozzle Body Design:
- The body contains a turret with six numbered nozzle locations, all pointed down, and two solenoids, one on either side of the body. Three nozzle locations are on short feeds (locations 1, 2, and 3), whereas the remainder are on long feeds (4, 5, and 6). The front locations and left solenoid is called “A”, whereas the right solenoid and rear location is “B”.
ExactyApply nozzle body
- Nozzles are paired so that A or B or both are capable of spraying at a time, depending on the selected mode. Pairs are 1 & 4, 2 & 5, and 3 & 6. The operator manually rotates the desired nozzle pair into position.
- When a short feed (1, 2, or 3) is placed at the front of the body, the system is in Separated Mode. In this mode, the left solenoid controls the front nozzle and the right solenoid control the rear nozzle. Either or both can be used, in pulsing (PWM) or conventional mode, selected through the monitor.
- When a long feed (4, 5, or 6) is placed at the front, the body is in Combined Mode. Now, all flow from the right and left solenoid can only exit the front nozzle. Very high flows are achievable in Combined Mode, making it suitable for liquid fertilizer application. It may not have other practical applications in Western Canada.
View from left side of body (solenoids removed). Turret position #4 (tall feed) is in front, and #1 (short feed) is in back, placing the body in Combined Mode.
- In Pulsing Mode, each solenoid pulses at 15 Hz, meaning it completes 15 open-and-close-cycles per second. The A and B solenoid timing is offset by 180 degrees, so that the B nozzle is in the middle of its on-cycle when the A nozzle is in the middle of its off cycle. In combined mode, this means that the system operates at 30 Hz.
- Adjacent bodies are also 180 degrees out of sync with each other, similar to Capstan, Raven, and TeeJet bodies, so that whenever a nozzle is off, its adjacent partners are on (when operating at 50% DC and above). Another way of saying this is that all even-numbered bodies act together, and all odd-numbered bodies act together but half a cycle later. This results in a blended pulse that prevents skips.
Plunger assembly inside solenoid. Black plastic portion can be removed, exposing poppet and spring.
- The proportion of each cycle that the solenoids are open is known as the duty cycle (DC). At 100% DC, the valves are always open. At 50% DC, the valves are open 50% of the time. The minimum DC allowed by the system in default is 25%. This can be lowered to a smaller value within the monitor.
Opened plunger assembly showing tip of poppet (right) and seat (left)
Poppet inside plunger assembly is pulled back by magnet inside solenoid 15 times per second
- DC is closely related to the flow rate of the nozzle. There are two ways of looking at this. An 08 sized tip operating at 40 psi will have a flow rate of 0.8 US gpm at 100% DC, about 0.4 US gpm at 50% DC, and close to 0.2 US gpm at 25% DC. This feature is primarily useful when sprayer speed is changed, requiring new flow rates without a change in spray pressure.
- Pulsing Mode is not available for nozzles sized smaller than 02, or for air-induced tips.
- Pulsing can be disabled to allow the use of air-induced or other tip technologies that may not function well when pulsed. This is called AutoSelect Mode.
AutoSelect Mode:
- AutoSelect Mode (“Auto Mode” in 4600 monitor) can be used to achieve three unique flow rates. “A” alone, “B” alone, or “A” & “B”. When properly staggered, a travel speed range similar to Pulsing Mode can be achieved, although pressure will rise within each nozzle as travel speeds increase, as in a conventional system.
- In AutoSelect Mode, the user selects a tip for position A, and an incrementally larger tip for position B. The monitor requires that the user inputs minimum and maximum pressures for A, B, and A&B. Travels speeds corresponding to these tip and pressure choices are calculated, and the monitor warns the user when speeds don’t overlap. The user either changes minimum and maximum spray pressures, or selects a different sized tip to eliminate the gap.
- AutoSelect Mode is useful when a certain specific tip is required which is not compatible with Pulsing Mode, for example drift protection with air-induced tips.
Pulsing Mode Nozzle Selection
At this time, John Deere nozzles best suited to the ExactApply’s Pulsing Mode are the LDM, LD, LDX, and 3D. Of these, the LDM most closely represents the spray quality of the LDA and ULD that John Deere operators are accustomed to. The remainder are considerably finer.
ASABE spray qualities for Low-Drift Max (LDM) tips. Being Very Coarse at lower pressures, applicators are advised to use higher spray pressures (50 to 70 psi) when coverage is important.
ASABE spray qualities for Guardian (LDX) tips. Note that the smaller sizes (03, 04, 05) produce finer sprays and will require pressures below 40 psi to have any reasonable drift reduction.
ASABE spray qualities for 3D tips. As with LDX, the smaller sizes (03, 04, 05) produce finer sprays and will require pressures below 30 psi to have any reasonable drift reduction. Such low pressures may narrow the spray pattern.
ASABE spray qualities for Low-Drift (LD) tips. As with LDX, the smaller sizes (03, 04) produce finer sprays and will require pressures below 40 psi to have any reasonable drift reduction.
ASABE spray qualities for the Low-Drift Twin (LDT). Comprised of two same-sized LD tips assembled in a TwinCap.
Proper sizing for PWM requires that tips be sized for about 20 to 40% extra capacity. In other words, at expected average travel speeds, the pulsing duty cycle should be approximately 60 to 80%. The following chart has a highlighted column at 70% duty cycle for that reason. Assuming an ExactApply operator expects to apply 5 gpa and travel at 15 mph on average, possible nozzle options (highlighted in yellow) are:
03 at 60 psi
04 at 30 psi
05 at 20 psi
06 at 15 psi
Calibration chart for PWM systems. Nozzles are sized at about 70% Duty Cycle (grey column). Options for 5 gpa at 15 mph are highlighted yellow. Black highlights represent speeds >25 mph, not available.
The best choice will likely be either of the first two options, as the third and fourth have spray pressures which are probably too low for good nozzle performance. The decision would depend on the spray quality obtained for each of the remaining two options.
Of course, spray pressure can be altered to suit the operator’s spray quality requirements. This merely affects the available speed range as well as the DC at which the system operates at a given target speed, possibly affecting Pulsing Mode utility.
The row of speeds adjacent to the selected nozzle and pressure identifies the approximate travel speed range that can be expected, from 25 to 100% DC.
It’s important to know your current DC to be sure the system is operating properly, and also to take full advantage of turn compensation features. We’ve described a way to place a DC display module on your home screen here.
Download an Excel version of this chart here.
ExactApply Nozzles Pulse Mode-June 2020 Download
The application volume can be changed to suit the specific use, the chart’s speed values are updated automatically. Make sure the nozzle spacing at the top left is correct for your sprayer
Pressure Drop across Solenoids
PWM solenoids represent a restriction to flow, and may cause a pressure drop. John Deere has published the pressure drop, and it is shown in the above chart (download version only). The pressure drop is fairly low, only 2 psi for an 04 tip operating in separated mode at 40 psi. For an 06 tip, the drop is 3 psi, and for an 08, it’s 6 psi. a #10 tip has a 10 psi drop at 40 psi. These pressure drops must be added to the operating pressure of the sprayer. Pressure drop is important because the LDX, LD, and 3D tips will be operated at low pressures to obtain coarse sprays for drift protection. Operating an 08 tip at 20 psi (at which pressure it has s drop of 3 psi) will result in in a tip pressure of 17 psi. Since we are at the low end of a nozzle’s operating range, pattern stability may be compromised when the drop is not taken into account.
Why 70% Duty Cycle?
An operator of any PWM system needs to know their current duty cycle. On ExactApply, a module can be installed on the home screen that provides a visual display. We show how to do this here.
There are five main reasons a nozzle should be sized to run at approximately 70% DC. The first is to provide speed flexibility. An operator may need to speed up somewhat, but usually not more than 30%. On the other hand, slowing down is much more common to accommodate challenging terrain, and a factor of two to three is possible (from 70% DC to 25% DC).
Secondly, drift reduction through lower spray pressure usually requires less speed due to the associated lower flow rate. With some DC room to spare, the loss of flow can be corrected without requiring a speed change.
Thirdly, spot spraying at a slightly higher rate is possible, again through DC alone.
Fourth, Nozzle Rate Boost of up to 25% for up to six nozzle locations is possible within the monitor, but only if the system is operating at 75% DC or less.
Finally, turn compensation, during which the outside boom travels faster than the tractor unit and the inside boom slower, requires this additional capacity. More on turn compensation here.
AutoSelect Mode Nozzle Selection
AutoSelect Mode allows for three flow rates to be used in succession: A, then B, the AB. The key to success is to use small size increments between A and B, and to use tips that have a wide pressure range.
In the example below, the A location was an 02 tip and the B was an 03, for a total of 05. Pressure was not allowed to drop below 30 psi to retain good patterns. Pressure at switch over to the next largest flow rate therefore needed to be 80 psi to make the moves possible without pressure gaps resulting in over-application. As a result, the spray quality can be expected to fluctuate three times as the sprayer accelerates through A, B, and AB in succession.
Nozzle selection should seek to emphasize the middle of the pressure range of either B or AB to avoid unnecessary fluctuations.
Spray pressure and travel speed as Auto Mode moves through A, then B, then both A&B
Download an Excel sheet that assists in nozzle selection for Auto Mode here.
ExactApply Nozzles Auto Mode Download
Maintenance
A maintenance kit comes with each ExactApply sprayer. It contains two spare plunger assemblies, clips, and pins, as well as a brush, an O-ring picker, and a torque driver.
Maintenance kit
The ExactApply body is fairly easy to take apart for servicing. Hair pins at the back of the unit secure each solenoid, and both pull out easily. The plunger assembly can be disassembled without tools. Take care not to drop the poppet spring!
Reassembly of the plunger requires the use of the torque driver fitted with a 17 mm socket, included in the kit. Do not over-tighten the plastic component.
Aside from the manual rotation of the turret to select a different nozzle combination, the only moving part in the ExactApply body is the poppet in the plunger assembly. This piece is the valve that controls flow rate, and opens and closes 15 times per second whenever pulsing mode is on, moving like a piston in a cylinder. Debris (sand, fertilizer crystals, etc.) can interfere with the seal of the poppet against its seat, and good filtration is important.
In the first generation, metal flakes began appearing inside some plunger assemblies . A coating de-laminates off the sleeve and can cause the plunger to stick. This has been starting at 800 h of use. The springs have also been observed to break. This problem has been addressed in newer generations.
Metal flakes interfering with plunger action
Plunger damage showing likely source of metal flakes
Broken plunger spring
Certain formulations may build up a residue that interferes with poppet movement. It’s impossible to predict all possible formulation impacts, but oily formulations such as emulsifiable concentrates (EC, milky appearance) are likely to be more problematic than solutions (S, clear appearance). John Deere recommends a daily rinse of the boom through both the A and B valves with Erase, a tank cleaner product. Fortunately, the R series sprayer allow for boom flushes from the clean water tank even when the product tank has product in it.
Each nozzle body contains ten O-rings and two sets of seals. The turret assembly has two large rings, and each plunger assembly has four. Care needs to be taken to prevent damage to these rings to prevent leaks.
O-rings in nozzle body
Some Recommendations
The ExactApply system is very full featured and customers new to PWM can be overwhelmed by the number of choices at their disposal. Let’s simplify the system and make some basic recommendations.
1. Pulsing mode is likely to be the most useful feature of the system. Plan to use this feature for most spraying operations.
2. In Pulsing mode, select from John Deere’s LDM, LDX, LD, and 3D tips. The LDX, LD, and 3D offer similar Medium spray qualities and should be operated between 20 and 40 psi to produce lower-drift sprays. Check spray patterns at these pressures and ensure that 100% overlap is achieved (pattern width is twice nozzle spacing).
3. The LDM (Low Drift Max) is coarser than the above nozzles (comparable to ULD or LDA) and is available in 03, 04, 05, 06, 08, and 10 sizes. This will be the tip of choice for pulsing mode and can be used at higher pressures to ensure good pattern formation.
4. Separated mode can handle most flow rates, and offers the flexibility of choosing A (front tip) or B (rear tip) or both. This means turret 1, 2, or 3 will be in the forward (A) location.
5. Equip the A location with your low volume tip (say, 5 gpa). Place the high volume tip (say 10 gpa) at the B location. Use both together for late season sprays into dense canopies (in this case, A&B=15 gpa)
6. Twin tips for Fusarium Head Blight (FHB) can be achieved in five different ways.
  1. 3D tips in “A” or “B”, alternating their orientation along the boom (forward, backward, forward…). Pulsing Mode. (Since these tips are not very coarse, low pressures are needed to ensure that the angle of the spray persists more than a few inches).
  2. 3D tips in “A” and “B” on each body, front facing forward, rear facing backward, and operating in A&B. Pulsing Mode.
  3. LDT (Low Drift Twin) in “A” or “B”. LDT is a TwinCap with two LD tips installed. Pulsing Mode.
  4. LDM (Low Drift Max) in installed in a TwinCap in “A” or “B”. These are coarser sprays that will retain their direction longer and are well suited for FHB. Pulsing Mode.
  5. GAT (GuardianAIR Twin), an air-induced tip, running in either conventional “A” mode or in Auto Mode but sized for “B” (avoid operating in A&B to prevent pattern interference).
Some recent recommendations: A customer wanted tips for 5, 10, and 15 gpa at 14 mph, and the 15 gpa was for FHB. He didn’t want to be too coarse. We recommended the LDM 03 at 60 psi (5 gpa) in “B”, the 3D 08 at 30 psi (10 gpa) in “A”, and both together, with the 3D facing forward, for FHB for 15 gpa. The sprays would be “Coarse”, a nice middle ground.
ExactApply joins Capstan PinPoint II, Raven Hawkeye, and WEEDit Quadro, Agrifact StrictSprayPlus, and TeeJet DynaJet with PWM capable systems. Auto Mode is a version of nozzle switching first introduced into the market as Arag Seletron and Hypro DuoReact. It appears to be a full-featured system that is fully integrated into the new John Deere 4600 display but is also available as a retrofit on the older R-Series 2630-equipped sprayers.
March 30, 2018