Tag: productivity

Recirculating Booms – Introduction to the Concept
Listen to the audio version of this article here
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.
January 22, 2019
Techniques to Improve Spray Productivity
Click here for an audio version of this article
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.
Evaluate your spray productivity with our
January 19, 2019
Plumbing Projects That Make Spraying Easier and Safer
Some of our biggest struggles in spraying involve the start and end of each spray day.
When starting a new field after the sprayer is cleaned, we need to prime the boom. If it’s full of water, that water has to be purged and the question is always for how long and where to do this (pro tip at bottom of article).
At the end of the day, we should ideally clean the sprayer. During that process, we may struggle with waste disposal, including large rinsate amounts, and course, the uncertainty of whether the job is actually done (since clean water looks exactly the same as contaminated water).
If not cleaning the entire sprayer plumbing, we should at least rinse the boom, even if we’re returning to the same product the following day. It can prevent future problems.
These tasks are complicated by the increasingly convoluted plumbing featured on modern sprayers. Ask someone to explain their sprayer’s plumbing system to you one day. It’s a long story! A bright spot is the well-engineered, compact, and accessible Agrifac system.
Fortunately, virtually any sprayer can be modified to suit your needs. Let’s talk about a few ideas for a winter project:
1. Boom flush. It’s good practice to flush clean water through your boom at the end of spraying even if the main tank remains full of product. Some sprayers have an air purge system to eliminate liquid from the plumbing and that is a great feature. A water flush should follow that purge so that any residual pesticide is diluted and removed before it can dry on and become hard to remove later. First you’ll need a clean water tank on the sprayer (150 gal is enough). Second, plumb a feed so that this clean tank can be the sole source of the water supplied to the solution pump. Select this source, shut return lines down or off, and pump clean water through boom. Sprayers that have an auto-rinse cycle will likely be able to draw clean water, but may not be able to push it to the boom, directing it to the wash-down nozzles instead. Check to see what’s possible, and make the changes you need.
2. Clean water pump. Installing a second pump dedicated to the clean water tank has several advantages. We’ve talked about continuous rinsing before, here, and here, as a way to dilute the tank remainder faster. It requires installation of a second pump dedicated to clean water. Additionally, give this pump the option to deliver water to the boom, not just the wash-down nozzles. Now it can be used to rinse water through the boom. The main challenge is to obtain a pump capacity that can match the needs of the boom and/or the wash-down nozzles.
3. Boom ends. We’ve mentioned this part of the boom many times. Boom ends must be flushed regularly to get rid of product and possibly debris that gets stuck there. A simple way to achieve this is to use the Express Nozzle Body End Caps from Hypro. These bleed air continuously, and also prevent accumulation of dead-end contamination. They do need to be flushed, and this can be done by pulling a plug or rotating the turret to an open (no nozzle ) position.
1. Recirculating boom. This is a significant change, but worth considering. Conventional plumbed booms are separated into five to 13 sections. Each has two ends at which the spray stops and where air and contamination can accumulate (see point #3). Each section feed has a shutoff valve. Once the spray mixture leaves the pump and bypass valve, it is committed to leaving the sprayer. In a recirculating boom, the boom becomes a part of the tank and the liquid can return to the tank if desired. Spray is pressurized at one or both ends, and valve positions determine its flow. Sectional control is achieved with individual nozzle shutoff, air or electric.
  1. Three advantages:
    (a) the boom can be primed with new product without spraying. The surplus goes back to the tank.
    (b) the boom can be flushed with water without spraying while material is still in tank, and without spilling anything on the ground. Again, the surplus goes back to the tank.
    (c) high resolution sectional control with individual nozzle shutoff is a byproduct of this design. Fast response, high res, saves money.
2. Steel lines. Steel cleans easier than plastic, and this material makes a lot of sense for booms. But it also makes sense for the boom feeds, currently handled by black rubber hose. This hose is a literal black box. We can’t see inside it, and we don’t know if and where potential contamination resides. It has considerable surface area. Consider replacing portions of your feed lines with steel. The boom is the obvious candidate. Aside from easier cleanout, it also helps with faster nozzle shutoff because it doesn’t expand with pressure.
A word about dumping the tank on the ground. It’s a bad practice for many reasons. Let’s examine just one of those. When you spray a product at 10 gpa, you actually cover each square meter with about 10 mL, or 1/3 oz, of spray mix. When you flush your boom ends on the ground, you’re probably dropping 2 or 3 gallons in the same area. That’s 1000 times the label rate at each boom end, 10 to 26 times per boom. If you dump your tank remainder and all the hoses, say 20 or 30 gallons, that’s 10,000 times the label rate if it covers 1 sq meter. That’s leaching, runoff, residual potential, and not a good story.
Many of the changes we outlined above help prevent that from being necessary.
Pro Tip: To find out how much water your plumbing (from the pump to the boom ends) holds, do this: After cleaning with water and before spraying an EC formulation (white milky appearance in tank, some crop oils are ECs) reset your sprayed gallons on your rate controller. Start spraying and watch for the last nozzle on your furthest and longest section to spray white. Stop spraying and check your sprayed gallons. That’s your volume. No matter the size of nozzle or application volume, it stays constant. To be sure the boom is primed with a new mix, spray until those gallons are reached and you’re set.
July 6, 2017
Question of the Week: Fine Sprays for Fungicides?
The following question arrived from one of our prairie clients last week:
“A retailer is promoting the use of hollow cone nozzles to be used on field sprayers (20” spacing) to apply fungicides which he claims out-perform any regular and twin fan tips. Claims:
- create an extra fine droplet for maximum coverage on the canopy
- use less water, less time spent filling
- apply at 3.5 gpa
- add vegetable oil to reduce drift
“So his direction to a specific customer was to use the TEEJET CONEJET TXA8001VK nozzle at 80 psi – travelling at 10 – 12 mph to achieve a 3.4 gpa application rate with a ‘very fine’ droplet size.
“What are your thoughts?”
Here’s how I answered (edited for clarity):
That recommendation sounds familiar – it originates from a consultant with experience in South America, where this idea is promoted to improve (aerial) spray productivity.
I fundamentally disagree with his approach. Adopting and promoting it is not only illegal (contravenes every modern label’s water volume and spray quality requirements), it also puts a generation’s worth of stewardship efforts on drift management at risk.
To be balanced, let’s explore the attractiveness of this approach. Finer sprays do provide superior coverage and save water. Every child knows this. Finer sprays also go places in the canopy where the coarser sprays can’t, for example very dense lentil canopies.
Over the years, we’ve explored the performance of fine fungicide sprays in canola, pulses, and cereals in research trials with the U of S and AAFC. To our surprise, droplet size played only a small role in fungicide performance. Water volume was much more important. Droplet size management with pressure through a low-drift nozzle was enough to get the best disease control.
The main drawbacks of very fine sprays are:
1. The fine droplets evaporate to dryness very quickly, in seconds. As they shrink, their drift potential is increased even more, and once dry, the remaining particles work much less well. The proponent corrects for this by adding an oily adjuvant as an evaporation retardant. With oil, the fines remain liquid much longer. Although many products become more effective this way, they also become more phytotoxic and less safe for the applicator and bystander. Completely off label, completely risky for crop safety, unknown effects on MRLs, extremely unsafe for the environment and humans. Remember when people dissolved 2,4-D ester in diesel, back in the 40s and 50s and sprayed it with their brass 6501 tips? That’s what this is.
2. Cone nozzles are designed for airblast sprayers and do not produce good pattern overlaps for boom sprayers. The proponent of this method actually recommends that the boom be raised to overcome the bad patterns and to (believe it or not) simulate aerial application. If this were done, the spray would be re-distributed by air-currents and come down wherever the wind blows it. Probably far away. The concept of on-target, uniform application, the practice that makes product use acceptable, and the thing we try to achieve with flat fans at a low boom height, is completely lost.
3. Producers will not have the support of pesticide manufacturers should a performance issue arise. Even worse, if regulators find out about this off-label practice, significant fines (fines for fines, get it?) can be charged under the Pest Control Products Act.
4. Airborne spray drift with an air-induced spray like the AirMix, GuardianAir, AIXR and the like, applying 10 gpa, is about 1% of the applied amount, measured at 5 m downwind of the downwind edge of the swath in a 20 km/h wind. We’ve never measured hollow cone drift from a boom sprayer, but when we used a flat fan at 5 gpa, drift increased to about 8% of applied. I’d guess a high pressure hollow cone would easily double or triple that. Illegal and irresponsible.
5. Travel and boom turbulence is a part of faster travel speeds. This would affect the finer droplets much more than the coarser ones, as we can imagine. It’s similar to drift. With a low-drift spray, the proportion of the total spray volume that is “fine”, say less than 150 microns, is about 5%. For a very fine hollow cone, it might by 50 to 75%. So a much greater proportion of the sprayed dosage would be susceptible to uncontrollable movement. This could be good, when turbulence redirects the spray to places that are unreachable by larger droplets. Or it could be bad, as turbulence pushes droplets away from an important target, creating a miss. On balance, bad. Very bad.
These types of recommendations are concocted by people who want to tell a unique story that is popular with some. Their approach differentiates them from the rest of the crowd, an old and effective marketing trick. But these proponents do not have the best interests of the industry in mind.
Our individual and collective agricultural practices must be respectful of others. Of safety. Of the law. Of the environment. We have lots of opportunities to make shortcuts…nobody’s watching most of the time. But that doesn’t make it right. It’s certainly not in ag’s long-term interest.
When considering our agricultural practices, imagine describing them to a young non-farming person. Can you justify your actions? Do your practices make you proud? If not, you have work to do.
Here’s a task: If your boom sprayer has nozzles that produce very fine sprays, take them off and throw them in the garbage. Might sound radical, but it’s the right thing to do.
July 5, 2017
Deciding on the Right Way to Spray
“What is the right way to apply this pesticide?” It’s one of the classic questions. Applicators know that spray method determines the efficacy of the application as well as its environmental impact. And it has to use time and water resources efficiently to make sense.
To answer the question properly, we need to take things one step at a time.
1. Canopy: To start, we need to look at the canopy that our application will go into. If it’s an early season spray into a seedling crop, then the canopy won’t be much of a barrier. Lower water volumes can be possible. Droplet size will only depend on the target type and the pesticide mode of action.
Small weeds require more smaller droplets to secure effective targetting
If it’s a later application into the bottom of a maturing canopy, the foliage may intercept the spray before it reaches the target area. More water will likely be needed, and droplet size may become more critical for getting the spray to its destination. Dense canopies are a real challenge and lower-canopy deposition usually benefits from finer sprays because the small droplets can turn corners better.
Dense canopies are very difficult for a spray to penetrate. Higher water volumes and smaller droplets are the key tools that help.
2. Water Volume: Regardless of canopy, the range of application possibilities will depend on the water volume and spray quality combination. It’s math: assuming some constant amount of coverage on each leaf, more layers of foliage will require more water. Using less water volume will make it necessary to use finer sprays to keep droplet numbers constant. More water will allow coarser sprays. This decision has implications for drift, and by extension, affects the number of hours we can spray in a day. More drift tolerance means better application timing and overall productivity.
The tradeoffs between water volumes and droplet sizes are seen in this figure. Once a certain threshold of coverage has been reached, a further increase in coverage may not provide any additional control.
3. Target Type and Droplet Behaviour: Whatever spray we use, the target plant or insect needs to intercept, collect, and retain the spray droplet. This is where the fun begins. Target leaves may be vertical or horizontal, large or small. Their waxy surface may be easy-to-wet or difficult-to-wet. The general rules of thumb are that larger, more horizontal and easy-to-wet surfaces are better suited for coarser sprays – these are intercepted more efficiently and stick readily. That is a reason why most broadleaf weeds and crops are very compatible with low-drift sprays.
Large targets (left) are most efficient at intercepting larger droplets (provided droplet bounce is not a problem) because smaller droplets may evade capture. Smaller targets are usually missed by larger droplets but are very capable of capturing smaller droplets.
On the other hand, smaller, vertically oriented and difficult-to-wet plants require finer sprays for effective targetting. Larger drops tend to miss these targets or bounce off them. Most grassy, and some broadleaf weeds (especially at early growth stages) fall into this category.
4. Mode of Action: There are nearly 30 modes of action on the herbicide world, and another ten modes for insecticides and fifteen for fungicides. The effect of droplet size and water volume on their uptake and translocation varies, and it’s probably not correct to generalize too much. There is one notable product, glyphosate. For this product, research has consistently shown that large droplets and more concentrated mixtures provide better uptake. But we’ve also seen problems when this is over-done, causing localized toxicity and limiting translocation.
With many products, we’ve sometimes seen better performance with finer sprays due to improved coverage, yet at other times less performance due to rapid evaporation. On the whole, it’s probably still fair to say that contact modes of action require finer sprays and higher water volumes, even if there is the occasional exception. And systemic products can typically handle coarser sprays. We’ve always been surprised just how coarse we seem to be able to push the system before any loss of efficacy.
What does it all mean? In spraying, we need to accommodate a lot of diversity. The average application is broad-spectrum, targeting large and small broadleaf and grassy plants. Many sprays are tank mixes of several modes of action. It’s impossible to prescribe a specific spray for each situation. We need a little bit of everything. And the spray should not be drift-prone. It’s easy to see that we need to aim for the middle to accommodate everything.
The traditional flat fan nozzle, either in its conventional or low-drift form, generates a wide range of droplet sizes that can range from 5 µm to about 2000 µm. If we need fine droplets, they’re there. If we need larger droplets, they’re also there. The proportion of the total spray volume in each specific size fraction depends on the nozzle choice and size, the spray pressure, and the adjuvant mix in the tank. Overall, the system is very robust, and although it requires some tweaking, a well chosen average spray can achieve most tasks well enough.
A typical spray quality chart shows the expected spray quality for a range of nozzle sizes and pressures. Spray quality measurements follow standards set by the ISO and ASABE, these change from time to time and therefore charts tend to become outdated.
Our research has repeatedly shown that a Coarse spray is a good starting point that does most things well. It is acceptable to move into a Very Coarse or coarser category provided water volumes are also raised, and provided the target types and modes of action are suited for this change.
It is rarely necessary to spray finer than Coarse, and when this is done, we recommend against spraying finer than a Medium spray. There is simply no advantage from product performance, and drift risk becomes unacceptable.
Tweaking the System. In order to maximize the performance of your spray, and the efficiency of your overall spray program, here is some advice:
1. Know the spray quality of your nozzles, and their response to spray pressure. Manufacturers publish this information in their catalogues and on-line. Make this your homework assignment.
2. Use the coarsest spray that you can afford to. This will make the application safer, it will widen the weather window, and it will simply let you get more done in a day or a season. Coarse sprays work.
3. Use spray pressure and water volume to fine tune the application for a specific purpose. If using a contact product, you can keep the same nozzle you used for a systemic product. Apply more water or use more spray pressure to generate more droplets.
4. Do not skimp on water. Higher water volumes tend to make an application more uniform, robust, and crop-safe. Spray coverage improves. Canopy penetration improves. Coarser sprays are possible. The only exception to this rule is glyphosate, which works better in lower water volumes. But with higher glyphosate rates and more tank mixing, even that exception is disappearing.
5. Learn as much as you can about how your pesticides work and where they need to be in your canopy. Apply your knowledge to select optimal water volumes and spray qualities.
6. Be wary of people who advise very low water volumes in conjunction with fine sprays. They want to appeal to your need for efficiency, but do so at the cost of consistency and environmental stewardship. Plus these types of applications are illegal for many of our products.
June 7, 2017