Use this spreadsheet to calculate the minimum boom heights needed for various applications.
Some caution:
The values are theoretical and assume the fan angles are accurate. Some nozzles don’t produce the advertised fan angle. Enter your actual angle in the spreadsheet
The theory assumes that the droplets at the edge of the fan always move in their projected direction. In fact, after some distance (say 50 to 75 cm, gravity pulls the droplets down and the pattern no longer widens at the same rate. The rate of pattern collapse depends on the droplet sizes.
Use the 0% overlap column to help with banding nozzle pattern width. Simply use the nozzle spacing column to enter your desired band width.
Note that angling the nozzles forward or backward decreases your minimum boom height, but depending on the deflection of the spray in the wind, this too has limits.
Too high a boom obviously increases drift. But patternation from overlap isn’t affected that much, largely because the pattern is now subject to aerodynamics.
Press play to listen to an audio version of this article
Agronomists help farmers manage their crop with advice on everything from crop cultivars to fertilizer rates to marketing. It’s challenging to be an expert on everything, but a few core competencies can go a long way to improving the level of service.
Agronomists are also responsible for communicating environmental
best practices. Along with fertilizer rates come messages of source, time, and
place, the 4R principles. The same is true for spraying, with messages of spray
drift, resistance management, and economic thresholds part of the consultation.
Let’s remember that we should not be indifferent to the potential consequences
of our recommendations.
Here are six skills that an agronomist should know about spray technology.
1. Recognizing major nozzle models and their spray quality and pressure requirements.
Application technologists are often asked to identify
nozzles and recommend spray pressures for clients. It’s a skill that anyone can
develop with just a bit of homework.
First, learn the colour-coding of nozzles – colours identify
flow rates and follow an international standard that all manufacturers have
adopted.
ISO Colour coding of major nozzle sizes, as well as application volumes at benchmark speeds.
Next, focus on the common nozzles on the major sprayers. John Deere sprayers will typically have three main air-induced nozzles, made for John Deere by Hypro, the Low-Drift Air (LDA), the Ultra Low-Drift (ULD), and the GuardianAIR Twin (GAT). Those with ExactApply, John Deere’s PWM system, will see the non air-induced 3D, the Guardian (LDX), and the Low-Drift Max (LDM). Recall that PWM flow control should not be used with air-induction tips.
Almost all Case sprayers have PWM, called AIM Command. Case uses Wilger ComboJet bodies and nozzles, with the ComboJet ER, SR, and MR most common, sometimes the DR or UR for dicamba.
New Holland/Miller with PWM (called IntelliSpray) are also likely to have these tips, but because these brands have TeeJet bodies on their booms, they require an adaptor for the proprietary ComboJet caps.
Otherwise, PWM units often use TeeJet’s TurboTeeJet (TT), Turbo
TwinJet (TTJ60), and Air-Induced TurboTwinJet (AITTJ60), the only air-induced
tip approved for PWM use by TeeJet.
Conventional spray systems (i.e., no PWM), will commonly
have (in alphabetical order) the Air Bubble Jet (ABJ, actually labelled BFS for
their manufacturer, Billericay Farm Systems), the Greenleaf AirMix (AM), the
Hypro GuardianAIR (GA), and the TeeJet AIXR.
Many sprayers will have a twin fan for fungicides, primarily for fusarium headblight (FHB) management. The Greenleaf Turbo Asymmetric Dual Fan (TADF), the Hypro GuardianAIR Twin (GAT), and the TeeJet AI3070 dominate, as well as a number of custom configurations using splitters and twincaps.
Where dicamba is applied on Xtend trait soybeans, some special nozzles may be used to meet label requirements for coarseness. The TeeJet TTI is very common, but Greenleaf developed a special set of tips called the TurboDrop XL-D and the TADF-D. Wilger’s version, mentioned earlier, is the UR. John Deere has just announced their new ULDM.
That covers 95% of what you’ll encounter in the North American market. In Europe, add some Lechler nozzles (ID3, IDTA, IDK, IDKT) to the mix. In Australia, Arag is gaining ground.
Identifying the nozzles on sight is the prerequisite to
finding out their average droplet size, called spray quality. Often, the
inscriptions are worn off, so visual recognition is required to get there.
We’ve published a visual identification guide with pictures of the major nozzles here.
Knowing the relative spray qualities produced by these
various nozzles will get you bonus points, but you’ll need to do some extra
research to get there.
2. Using a spray calibration chart
This skill will make you popular on the farm and at the office. A very frequent question is “what size nozzle do I need for this new sprayer?”. The best way to approach the answer is to ask several questions.
Does the sprayer have 20” nozzle spacing? (90% of sprayers do).
What is the desired water volume?
What is the expected average travel speed?
The first question guides you to the appropriate calibration chart, which can be downloaded here or can also be found in all sprayer catalogues. We explain how to use these charts here.
Calibration chart for 20: spacing, in US units.
If you don’t have a chart handy, use this shortcut: on a boom with 20” spacing, at 5 mph, every 0.1 US gpm capacity at 40 psi delivers 6 US gpa. So if you need to apply 12 gpa at 15 mph, an 06 size will get you there at 40 psi. That’s ballpark.
In metric, with 50 cm spacing, at 10 km/h every 400 mL/min (01 size) at 3 bar delivers about 50 L/ha. To deliver 200 L/ha at 20 km/h would require an 08 (white) tip.
Of course, if the tip is air-induced, make adjustments to speed or size to accommodate the higher pressure requirement of these types of nozzles.
Remember that spray pressure is key to performance, therefore the operator needs to drive at a speed, or use a volume, that results in the correct spray pressure.
3. Understanding Pulse Width Modulation
PWM technology has been on the North American and Australian market for two decades, but it remains poorly understood by those who do not use it. PWM will continue to gain popularity and has implications for nozzle selection and sizing.
Traditional rate control in the field involves the use of spray pressure to match liquid flow rates to travel speed. The rate controller knows the width of the boom (entered by the user), the travel speed (from gps), and the desired application volume (entered by the user). It does some math to identify the flow rate it needs, and compares that to the sprayer’s current flow meter reading. If the current flow is less than what’s needed, the sprayer increases pressure to increase flow. This happens continuously in the background.
When an operator speeds up, the pressure increases, and vice versa. As a result, the pressure (and therefore droplet size) will fluctuate with travel speed, and that can result in inconsistent spray patterns, coverage and drift.
PWM involves the installation of electronic solenoid valves at each nozzle body. These valves pulse on and off at 10, 15, 50, or 100 Hz, depending on the manufacturer. Each pulse contains a brief, complete shutoff of the flow. The proportion of the time the valve is open during a pulse is called the Duty Cycle (DC), and this is proportional to the flow through the nozzle.
Capstan PWM solenoid on Case AIM Command
When the system requires more flow, it no longer increases pressure. Instead, it increases the DC. The advantage of this approach is that nozzle pressure can now stay constant, ensuring consistent coverage and drift.
There are other advantages of these systems. Each nozzle can be controlled independently, offering high resolution sectional control and turn compensation.
Nozzle selection and sizing are both affected by this technology. Nozzles need to be sized larger, with about 30 to 40% more flow capacity ideal. The DC will therefore run at 60 to 70%, optimal for speed fluctuations and turn compensation. Air-Induced tips are not usually recommended because their pattern deteriorates with pulsing.
We’ve written about PWM here, here and here to get you started.
4. Validating coverage of the target
A very useful indicator of the success of a spray operation is an assessment of “coverage”. This term refers to a qualitative combination of droplet density and percent area covered, and can be quickly assessed using water sensitive paper. We’ve explained the use of WSP here and here.
It’s very useful to have some of this paper on hand (available from any retailer that sells TeeJet or Hypro products, or on-line from Sprayer Parts Warehouse in Winnipeg or Nozzle Ninja in Stettler, AB). The coverage can be assessed in four different ways:
Water-sensitive paper being used to assess spray coverage.
using the “DropScope” scanner (gives a comprehensive assessment of coverage, density, size, plus image editing tools);
using a template of coverage examples;
using experience built on years of doing this.
Water-sensitive paper is also useful as a record, for
quality assurance. A spray application is conducted and part of the record is
an image of the deposit. Should a performance issue arise, this will help
settle it.
5. Understand basic sprayer plumbing
Often, a sprayer problem can be traced back to an issue with
its plumbing. There could be mysterious sources of contamination. The pump might
not be building pressure. The agitation isn’t running. Or you need to drain all
the remaining liquid from the tank.
Sprayer plumbing seems intimidating for a number of reasons.
It’s become complex on most modern sprayers. It’s hidden under the sprayer
belly. All the lines are the same black colour, so they’re hard to tell apart.
But it’s not as bad as it seems. Basic plumbing is the same
on all sprayers. The pump draws the spray mix from the bottom of the tank, the
sump. It may also have options to draw clean water from an external supply, or
from the clean water tank for wash-down.
The pressurized supply goes to three places:
to the booms, via sectional valves;
back to the tank, via a control valve that can be used to adjust the spray pressure;
to the wash-down nozzles.
Typical sprayer plumbing for a centrifugal pump (Courtesy TeeJet).
When spraying, the less is returned to the tank, the higher the boom pressure. There may be several ways back to the tank, via agitation, via bypass (sparge), or via wash-down (used only when the pump draws water from the wash-down tank). Usually engineers can’t help themselves and introduce several what-if features that complicate the situation. But with a bit of know-how, and a flashlight, the plumbing system can be deciphered.
Pro tip: A centrifugal pump’s inlet (suction) is always the centre of the pump, its outlet (pressure) is at the periphery.
6. Matching a pesticide recommendation with application advice
It’s commonplace to recommend a specific crop protection product that matches the crop and pest situation. Recommending an ideal crop or pest stage improves the recommendation. But a truly successful outcome requires one additional step, advice on the application method. The customer may need to know if product performance depends on water volume and droplet size. Some products are more sensitive to this than others. Perhaps there is a specific nozzle type that may be helpful.
The classic example for application method is Fusarium headblight in wheat. The basics are straightforward. An agronomist recommends the fungicide, and guides the tight application window with a field visit to stage the crop, plus a look at the disease risk forecast map. But true application success requires an angled spray, with a coarser spray quality plus relatively low boom height to make it all worthwhile. That’s a full-featured recommendation.
Common herbicide applications also benefit from additional
information. Some tank mixes and weed spectra allow for coarser sprays than
others, and the ability to spray coarser means a wider application window and
therefore more accurate timing. Other tank mixes may pose a significant risk to
drift damage, requiring special measures to prevent a problem. Identifying
those opportunities adds value.
Water volume and spray quality recommendations for major herbicide mode of action groups.
Newer labels for dicamba (Xtendimax, Engenia, Fexapan) and 2,4-D
(Enlist Duo) have very specific instructions for drift prevention. This
information must be shared with customers to ensure that their drift liability
is covered.
Are there other skills that you feel agronomists should have?
Please share them with us by contacting us at the bottom of this page.
A lot of people are intimidated by sprayer plumbing. One look at the spaghetti bowl of spray mix and hydraulic hoses and valves, and they walk away. It hasn’t helped that much of it is concealed under the frame and all of it is in the same black colour, so figuring it out on your own is almost impossible.
Belly of a typical sprayer, showing black hydraulic and spray hoses.
Let’s quickly review the basics. In all sprayers, the liquid in the tank is drawn out from the bottom and pressurized by a pump. The pressurized liquid is split into two main paths. One goes to the spray boom to hydraulic atomizers (nozzles). The other goes back to the tank to agitate the liquid and act as a pressure bypass when the booms are off. Bypass throttling changes pressure. That’s it.
Sprayer plumbing diagram (Source: TeeJet).
By the way, has anyone ever thought of some colour-coding or labelling the hoses and valves on a sprayer? We’d definitely appreciate that.
Conventional boom sections
Most North-American sprayers feed the pressurized liquid to the boom, where the flow is subdivided into physical sections that define the various portions of the boom that can spray at any one time. Older sprayers might only have two sections, the left and the right boom. Wide booms now have anywhere from 5 to 13 sections, each about two to four metres wide. Each section has a pressure feed to its middle, and each section terminates at two dead ends, at which we place caps or valves for flushing.
A conventional plumbed boom with two sections. Each section has two terminal ends that require cleaning. Boom can only be flushed or primed by spraying or by opening boom end caps.
Sprayer with nine sections, each controlled by its own valve and each running a dedicated feed hose.
Two partial boom sections, each showing a central feed line and a capped boom end.
Sectional boom end showing 10 cm of capped pipe beyond last nozzle body.
Boom end with valve to facilitate draining and flushing.
Any liquid that enters this type of boom must exit at the nozzle or the boom end. It must be sprayed out or drained. This poses three distinct problems.
If the boom contains water or a previous spray mix, the boom needs to be primed with the new product before spraying. We need to spray or drain the existing product out.
If we want to clean the boom or flush it with water, again we need to push the existing liquid out.
If we have dead spots in the boom section, such as a boom end, we need to take special care to flush those out as well.
These characteristics complicate cleaning, create waste or contamination, and take time.
Recirculating booms
In a recirculating boom, the spray mixture enters the boom at one end and exits at the other, returning to the spray tank. In most cases, the left and right wing each has its own feed and return. Sectional control is achieved via individual valves (air or electric) placed on the nozzle bodies.
There are two main types of recirculating booms on the market.
The first system routes the pressurized mixture into the boom and shuts off the return line during spraying. When the nozzles are shut off for a turn, the return line opens automatically and the boom flow is pushed past the nozzles back to the tank. When the nozzles spray again, the return line closes to pressurize the boom.
Recirculating boom system offered by Pommier. One end of boom is pressurized, the other end is return. Return flows when boom spraying is shut off. Boom can be primed or flushed without spraying.
This is the system used by Pommier, the French aluminum boom manufacturer who first introduced recirculating booms to North America.
Pommier recirculating boom.
Pommier boom showing stainless steel supply and return lines, as well as air-activated shutoff valve on nozzle body.
The second type of system contains a 3-way valve, connected to the return line and the pressure side of the pump. This valve provides the option of either allowing the return line to go back to the tank, as above, or to also allow pumped flow to the return side so that the boom is pressurized at both ends.
Recirculating boom that allows return line to be either pressurized by pump, or return to tank.
Top view of D.O.T. Connect sprayer recirculating boom setup. Lower line is pressurized by pump. Upper line is return. Three-way valve allows return line to either go back to tank, or be pressurized by pump.
Tidy setup of pressure and return lines on D.O.T. Connect system.
This feature may be useful with long booms along which pressure drop is more likely to occur, or when very high flows are required, and was introduced to North America by the Dutch manufacturer Agrifac, about which we wrote here and reprinted Mick Robert’s article from Pro Operator here. A similar system is available from Rogator (starting in 2018) via their C-Series featuring LiquidLogic. It has also been used on the Connect sprayer, developed by Pattison Liquid Systems, for the D.O.T. autonomous platform.
The main advantages of this design are that it provides the option of additional pressure to the spray boom to avoid pressure drop, and to allow any spray mix in the return line to be pushed and sprayed out to the boom for rinsing in the field. This lowers the remaining volume that needs to be diluted.
Agrifac recirculating boom showing return loop at boom end.
Boom end on Rogator Liquid Logic system. Note Hypro Pro-Stop E shutoff valve.
Features
Recirculating booms offer advantages in terms of preventing soil and water contamination and also in terms of simplifying the boom cleaning process. The design provides an opportunity to graduate to a better resolved sectional control as well due to the requirement for individual nozzle shutoff valves.
Due to shorter and less complex lengths of plumbing needed, stainless steel can be used for the return lines which decreases the potential for pesticide residue being adsorbed.
To rinse a boom with product mix still in the tank, simply draw water from the on-board clean water tank and push it to the boom without activating any nozzle bodies. The mix in the boom is returned to the tank and replaced with water, nothing is sprayed or drained. The tank contents may become slightly diluted depending on the duration of the rinse.
To rinse the tank as part of the sprayer cleanout, first spray the tank empty. Then introduce clean water into the product tank via the wash-down nozzles and spray that out. As always, either use several batches of small clean water volumes, or a continuous rinse system, to dilute the remainder most effectively. There may be additional volume to dilute from the return lines compared to a conventional system, depending on the type of recirculating system is used. However, boom ends no longer exist and this saves effort and ensures a more thorough rinsing.
To prime a boom that contains water, simply open the return lines back to the tank and allow the new mix to flow through the boom. Again, some dilution of the tank will occur due to the water in the boom.
The value of spray-free rinsing and priming adds up. Each prime, for example, consumes about 30 US gallons before the spray reaches the last nozzle of the longest section. Much of that product ends up on the ground, probably while the sprayer is stationary, and probably in a similar place on the field year after year.
Since a recirculating boom requires a powered individual nozzle shutoff, this adds some cost. However, the opportunity of improved sectional control via virtual sections is significant (most monitors offer 16 virtual sections that can be configured). Well-configured virtual sections can save several percent from overlaps.
Recirculating booms remove many of the contamination problems associated with conventional plumbed sections. They save time, money, and reduce environmental impact. We think they should be offered on sprayers.
Here’s a link to a nice article on recirculating booms written by Spencer Myers for the Manitoba Co-operator. A video that goes with the article can be found here.
In almost all agronomic practices, timing is key. There are certain, and often small, windows of opportunity for getting a task done without losing yield potential or product quality. Weed specialists talk about early weed removal, pathologists talk about symptom monitoring, and entomologists remind us of economic thresholds. Acting at the right time is fundamental.
Sometimes I’m asked about comparing two different methods of
spray application. I usually dodge these questions by advising to choose the
one that gets the job done on time. “An average application at the right time
is much better than an excellent application at the wrong time” is how I put
it. Sure, I’m dodging, but I really believe that. It’s mostly in the timing.
Everything we do carries with it some time inefficiencies.
Some are rooted in technology, others in habits. It’s the habits that are
easier and cheaper to address. That’s why, when evaluating how to improve a
spraying operation, I advise to start with a stopwatch and notepad, not a
sprayer brochure.
A stopwatch and notepad provides your path to greater productivity.
Remember, if you want to improve a system, you first need to understand it. And to understand it, you need to measure it.
So, do a time accounting. You need to know how your time is used on a spray day. Note the time spent preparing for the job (loading supplies, double checking label instructions, transporting, etc.). The big users of time are sprayer transporting, filling and cleaning, but there are very many small time users and those can add up. This time is doubly important because these tasks occur during the spray day, when the weather is good and you should be maximizing spray time.
Make your own time accounting sheet, including every detail or possibility.
Even within any one operation, time can be subdivided. How
much time is spent on a turn? Since a 120’ sprayer will make about 22 of these
per half mile, that can add up. Even a spray monitor can play a productivity role
if it quickly and consistently locks onto its swath. Needing to stop and back
up while it searches for a signal can be costly.
On our farm, we sometimes used custom operators to get the cereals off. I recall how aggravating it was to watch the 8820 inch ahead of my N6. Surely it must be throwing a lot over, I thought (it was). But I usually caught it at the truck, where my unloading speed was over 1 minute faster. Redemption, briefly.
That same principle applies to these small efficiencies. A well-designed tender truck can speed loading and more than make up for lower spray productivity of a smaller sprayer. A lighter sprayer load and flotation tires can save a ton of time if it means the difference between getting stuck or cruising through that spot. A set of extra-coarse nozzles that can be rotated into place in just two minutes can help finish a field if the weather changes, or allow a margin to be sprayed, saving a return trip.
Extra nozzles to allow spraying in higher wind speeds without increasing drift are a productivity tool.
A custom operator shared some very useful tips with me a few
years back. He optimized the small things, such as re-locating the switch to
deflate his suspension airbags after driving onto the trailer, to the platform
beside the cab. He’d deflate while descending the steps, and by the time the tie-down
straps were thrown across, the unit was ready to be cinched down. No waiting.
He also opted for a slightly wider aftermarket boom so he had an even number of
spray passes per quarter, saving another 2 minutes or so per field.
The same operator made me aware of the importance of knowing
exactly how much spray is in the tank at any one time. The majority of spray
monitors are simply not accurate enough. A factory sprayer can count down from
a full tank using its flow meter, but that requires two things to be accurate,
the filled amount (entered by the operator, usually from a sight gauge) and the
flow meter itself. Point is, when we fill the last load of a field, we don’t
want too much left over, but we’d still rather not run out. By using the
AccuVolume from Simon Innovations, he was able to fill accurately and he was
also able to exactly monitor his liquid usage. If he had two passes left, and
knew he needed exactly 150 gallons (also considering when his pump drew air),
he could monitor that and make small adjustments to the application rate, if
necessary, to get there. It’s a big deal because contending with a larger
remainder is wasteful and takes time to deal with. The AccuVolume also helps
make multiple small volume batch cleaning more accurate, and therefore easier.
The AccuVolume measures your tank contents, to the nearest gallon, regardless of slope position. It’s a time saver.
A small addition to the tender truck such as an electric
hose reel or a swing arm that carries, say 20’ of hose, helps deal with the
weight of a full 3” line. Or an air-line at the pump end can be used to blow
the remaining water into the tank. Time, and mess, are saved. Still pumping
product? Induction using a venturi is much faster.
An electric hose reel makes handling 3″ plumbing manageable.
Preventing problems is probably a better use of time than
dealing with them. Take tank mixes, for example. With more products in the
tank, and adjuvants such as conditioners, fertilizers, or low-drift products
making their way in, anticipating mixing problems may require a jar test. Get
the tools, and learn how to do them. It’s important to use the actual tended
water in these tests, at the temperature it will be, because that, and water
quality such as hardness and bicarbonates, can affect mixing. And don’t
over-agitate, as that can create its own problems, especially as the tank runs
down.
Consider a hot tank. If extra labour is available, it removes a lot of time pressure for mixing dry, or multiple products. At filling time, simply pump it over and go.
A hot tank gives you more time to mix properly, and makes transfers faster. (Some additional labour required).
Consider improvements in the plumbing to save time. The new Hypro Express End Cap features a ball valve for flushing (existing Express End Caps can be retrofitted), and this valve can soon be fitted with the ProStop E (electric) valve. Flushing can then be done from the cab, saving time and mess. It’s a small change, but it brings joy.
A new valve addition is available for the Express End Cap. Manual (shown) or electric available.
The importance of time on a spray day can also be viewed economically. Let’s say a large area needs to be sprayed today, and the weather forecast calls for rain overnight. The rain will stop spraying for 5 days. What is the yield potential lost in those five days if weed or disease pressure is high? If 100 acres don’t get treated, what is the lost revenue? (for example, if 3 bpa is lost, at $6/b, that’s $18/acre or $1,800.) That’s what that hour is worth. Tell your boss.
Getting more done means getting more done on time. Evaluate your habits and technologies on that basis.
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.
