Airblast operators should know how to read a nozzle table. They are found on dealer and manufacturer websites as well as in their catalogs. Table layout varies with brand, but they all relate a nozzle’s flow rate to operating pressure. The better tables also provide the spray angle and the median droplet size (i.e. spray quality).
Operators need this information to complete calibration calculations (aka sprayer math) and when deciding how to distribute nozzle rates, angles and spray quality along a boom relative to the target canopy.
This article focusses on hollow and full cone nozzles, which are commonly found on airblast sprayers. For more information on flat fan nozzle tables (e.g. for banded under-canopy or, vertical booms or broadcast applications from horizontal booms), refer to this article.
Reading the table
Let’s use the table below to determine a nozzle’s flow rate for a given pressure. First, find the nozzle colour in the top row. Second, find the operating pressure in the left-most column. Finally, the flow rate is indicated in the cell at the intersection between the row and column. For example, a red ATR hollow cone nozzle operated at 9 bar will emit a flow rate of 1.83 L/min.
Perhaps you want to determine which nozzle will give a specific flow rate. Find the rate in the body of the table and trace the column and row to determine which nozzle/pressure combination will achieve it. For example, if we want a flow rate of ~1.00 L/min, we can use a Yellow at 10 bar or an Orange at 5 bar. Yellow is the better choice since the Orange would have to be operated at the bottom of its pressure range (more on that later).
This Albuz nozzle table for 60 and 80 degree molded hollow cones gives flow rates in litres per minute.
Note: Do not to confuse TeeJet’s ISO-standardized TXA or TXB nozzles with TXVK or ConeJet nozzles. They may be the same colour, but their outputs are very different.
Higher flow rates or full cone patterns can be achieved using combination disc and core (or disc and whirl) nozzles. Depending on the manufacturer, the disc plate is defined by it’s diameter in 64th’s of an inch. The core or whirl plate might be described by the number of holes (e.g. 2-hole, 3-hole, etc.), or some other manufacturer-specific nomenclature (e.g. 45’s, 25’s etc.).
Using the table below, we see that a D2 disc and a DC35 core will emit 0.34 gpm at 80 psi. By continuing along the row, we see that the spray angle for this combination will be 47 degrees at that pressure.
This TeeJet nozzle table gives the flow rate for a disc (D#) and core (DC#) full cone combination nozzles in US gallons per minute.
Pressure problems
Do not choose a nozzle at the extreme of their flow or pressure range. A trailed PTO sprayer will experience pressure changes from driving on hills, or rate controllers will create pressure changes in response to changes in travel speed. In either situation, coverage will be compromised if the nozzle is pushed outside its optimal range.
Note: Use pressure to achieve small changes in flow, but for more extreme changes, switch nozzles. Remember, it takes 4x the pressure to get 2x the flow. Stated differently, it takes 1/4 the pressure to get 1/2 the flow.
You may not find a nozzle/pressure combination that emits the rate you are looking for. When your desired rate or pressure falls between the figures listed in the table, you can take the average. When nozzling an entire boom with different nozzle rates, get each position as close as you can to achieve the overall boom rate for a given pressure. It’s always a compromise – don’t stress over it.
Looking up nozzle rates during a spring calibration. The operator was running at 190 psi, but the catalogue only listed 180 psi and 200 psi. When the increment is only 20 psi, it’s reasonable to approximate the output. When the span is 50 psi increments, it is more difficult to determine the rate without testing the output (it’s not a linear relationship). This issue usually occurs at pressures above 200 psi, and that’s far too high for cane, bush, vine and high-density orchards. In these situations, consider using a lower operating pressure.
Different nozzles, same rate
Different disc core combinations, or molded nozzles at different pressures, can produce similar flow rates. However, their spray quality and spray cone angles can be very different (see last three columns in the TeeJet table above).
The angle of the spray cone can have a big impact on spray coverage. When the target is far away from the corresponding nozzle (e.g. the tops of nut trees), or the canopy is very, very dense (e.g. citrus canopies), consider tight-angled full cones under high pressure. This is inefficient and can give variable coverage, but it is sometimes the only option in extreme situations.
Oops! Two hollow cone nozzles on top and five full cone nozzles below is the exact opposite of how things should be. Note the lack of spray overlap with the full cones for the first few meters. Spray from the top two positions will likely not reach the intended target.
When the target is very close to the sprayer, full cones do not overlap and create undesirable striping or banded coverage. Creating a full, overlapping spray swath that spans the entire canopy is a function of nozzle spacing, distance-to-target, and sprayer air-settings. It can also be affected by humidity, wind speed and wind direction at the time of spraying.
Confirm your settings by parking the sprayer in the alley between crops. With the air on, spray clean water while a partner stands a safe distance behind the sprayer to look for gaps in the swath. The partner will see things the operator’s shoulder check will not reveal.
Here’s what the operator sees. But, shoulder checks may not show you what’s really happening. Have someone stand a safe distance behind the sprayer while spraying clean water to see the nozzle spray overlaps sufficiently to span the entire canopy.Here’s what the partner standing behind the sprayer sees. Take a picture with a smartphone to show the operator.
Nozzle tables can be wrong
Sometimes nozzles do not perform per the nozzle table. We have discovered errors in published tables, worldwide. Here are the big three:
Conversion errors. Manufacturers publish catalogs in Metric and in US Imperial, but we have found many errors in the conversions.
Spray angle errors. When nozzles are operated at the extremes of their pressure ranges, spray angles deviate from those listed in the tables.
Flow rate errors. When tables are not updated to reflect changes in nozzle design, or the manufacturing process, actual flow rates deviate from those listed in the tables.
Perhaps it’s not the table, but the nozzle itself. Most nozzle manufacturers accept a flow variability up to +/- 2.5% for new nozzles, but we have seen higher. It depends how they are made (machined, stamped, printed) and the material they are made of.
Validate flow rate and pattern
When errors are discovered and reported, the manufacturers can be slow to issue corrections and the errors will persist in old tables. Yes, even apps (which are often based on tables) can be wrong. So, predicted flow rates can prove unreliable. This is why it is important to double check by observing nozzle overlap and validating flow rate when you replace nozzles – even when they are brand new.
Thanks to Dr. David Manktelow (Applied Research and Technologies, Ltd., NZ) for input into this article.
Pressure is integral to nozzle performance. Reducing hydraulic pressure reduces nozzle flow rate, increases median droplet size, and typically reduces spray fan angle. Increasing pressure increases nozzle flow rate, reduces median droplet size and typically increases spray fan angle.
You can watch this Exploding Sprayer Myths video to learn how pressure, boom height and nozzle spacing interact. In extreme cases, too low a pressure can collapse the fan angle enough to reduce overlap and compromise coverage, as explained in the video at the end of this article.
Using a flat fan nozzle as an example, a lower pressure increases the median droplet diameter, reduces the droplet count, reduces the nozzle flow rate and typically reduces the spray angle. Alternately, a higher pressure decreases the median droplet diameter, increases the droplet count, increases the nozzle flow rate and typically increases the spray angle.
Always plan to operate a nozzle in the middle of its recommended range so it can handle small changes in pressure during spraying (such as from a rate controller, or when changing PTO speeds on hilly terrain). Don’t operate an air induction nozzle below 2 bar (30 psi), even if it’s rated lower in the manufacturer’s nozzle table. Most AI nozzles perform best at >4 bar (60 psi).
Pressure can be used on-the-fly to make minor changes to flow rate while spraying. This is how rate-controllers work to compensate for changes in ground speed and maintain a constant overall rate per planted area.
However, pressure should not be used to make significant changes to flow rate. It takes a 4x change in pressure for a 2x change in flow rate, so it’s inefficient. Operating pressures at the upper or lower limit of a nozzle’s range can have undesirable impacts on nozzle wear, median droplet size and swath uniformity.
For a more in-depth discussion of the relationship between spray pressure and nozzle performance, and how rate controllers work, check out this article.
Note: It is far better to simply switch nozzles when a significant change in flow rate is required.
In 2015, we ran demonstrations at Ontario’s Southwest Agriculture Crop Diagnostic Days. The 20 minute sessions were designed to explain:
Although manufacturers of air induction nozzles often rate their performance as low as 15 psi, such a low pressure collapses the spray pattern and the resulting gaps reduce coverage. Additionally, the spray quality at such low pressures is coarser than at higher pressures, reducing the number of droplets available. This further reduces coverage potential.
This video covers the key speaking points from that demonstration.
An airblast sprayer inspection is part of preventative maintenance. This daily activity identifies small problems before they become big ones. You can do it at the filling station, so it’s fairly convenient.
Don’t think of it as stealing time from your spray day… it’s part of your spray day. Don’t skip it. If time is tight there are many other ways to improve your work rate.
This spray plane was left on the runway with the engine exposed for less than four hours. When the owners returned they found a precocious bird had built a nest! Perform regular sprayer inspections – you never know what you’ll find. Photo Credit – S. Richard, New Brunswick.
Note: Always wear appropriate personal protective equipment (as indicated on the product label), including hearing protection.
Inspection steps
Follow this generic inspection process. If your sprayer manufacturer or manager advises additional steps, be sure to perform them.
Before filling
1. Work with a rinsed sprayer parked on level ground (e.g. the filling station).
2. Check lines/hoses and fittings for signs of wear or cracking. Leaks or bulging may only become apparent under pressure (see Test spray).
3. Filters, screens, strainers and nozzles are clean and unbroken. Leaks may only become apparent under pressure (see Test spray).
As a plastic suction filter ages, it can warp or become brittle. When this happens, the O-ring may no longer sit correctly and the unit may allow air to be drawn into the lines. They should be cleaned and inspected when the sprayer is rinsed.
4. Engage each nozzle shut-off valve or nozzle body flip position. They can seize or loosen with time.
Begin filling
5. Begin filling the sprayer 1/2 full with water.
6. For PTO-driven sprayers, confirm universal joint(s), sprayer-tractor hitch and all connections are clean, lubricated and secure.
7. Check that all guards (e.g. PTO shaft shield) are in place and intact.
8. Ensure fan blades are unbroken and scraped clean. Intake grill(s) must also be clean and unbroken.
9. When 1/2 full, stop filling and check tire pressure (tractor and sprayer).
Test spray
For multi-row sprayers, you may have to move the sprayer off the fill pad for the test spray; it’s easier with the air off, if possible. Perform the following steps:
10. Open the manifold valve to fill the lines and begin spraying clean water.
11. Ensure each nozzle sprays correctly. Get out of the cab to inspect, don’t just shoulder-check. This gives the opportunity to double-check for line-bulges and leaks.
12. Ensure the agitation / bypass system is functioning properly.
13. Check that the tank is secure on the chassis and both crack and leak-free.
Complete filling
Continue filling. Once the sprayer is back up to 1/2 full, mix products per usual. If your sprayer manufacturer advises contrary or additional steps for a sprayer inspection, be sure to perform them.
Sprayer inspections become repetitive, so it’s easy to accidentally miss things. Have you ever driven home while preoccupied, only to discover you don’t remember how you got there? Download our checklist to keep you engaged and to help ensure accuracy. Consider printing and laminating it for repeated use with a dry-erase marker.
You never know what you’ll find during an inspection. I found a robin’s nest hidden on this vineyard sprayer’s pump.
Anyone that operates heavy machinery should perform a preventative maintenance inspection before using the equipment. It’s no different for airblast sprayer operators; embrace the daily walkaround.
“Sprayer calibration is an important part of any crop protection program.” Everyone says so, so it must be important. But what exactly are they asking you to do, and why?
When delivering presentations I often take the opportunity to ask audiences to define airblast sprayer calibration. Their responses cover a wide range of activities that can be rolled up into three related, but quite different, definitions:
Sprayer maintenance inspection
Adjusting sprayer configuration
Validating sprayer output
Ask a group of managers, sprayer operators, agrichemical reps, gov’t regulators and equipment manufacturers to define “calibration”. Be prepared for very different answers.
Traditionally, calibration refers to Number 3: Validating sprayer output, but all three are required to ensure a safe, effective and efficient application. Don’t panic – your workload didn’t just triple.
There is a time and a place for each of these activities. Some should be performed more often than others, but none of them are difficult. This is easier to accept when you realize that only a portion of the spray-day is actually spent spraying. Filling, travel time, cleaning and calibration-related activities are all essential components.
Let’s consider each activity.
Sprayer maintenance inspection
This is more maintenance than calibration (e.g. is it properly connected, is it worn out, is it plugged, is it leaking?). It should not be confused with spring start-up or winterization. For those lucky readers in temperate regions, “winterization” is preparing the sprayer for long-term storage post season… we just use antifreeze.
The maintenance inspection is the morning walk-around, no different from what any operator of heavy machinery must do before starting their work day. Learn more about sprayer inspection and download a helpful checklist in this article.
Here are some nasty disc & cores revealed during a calibration workshop. It certainly explained the poor performance the operator was complaining about. Is it time to replace yours? Photo credit – Dr. H. Zhu, Ohio.
Adjusting sprayer configuration
This is an ongoing process whereby an operator makes minor sprayer adjustments (e.g. pressure, travel speed, air settings) to reflect environmental conditions, the product’s mode of action and the nature of the target. Would you apply an insecticide to semi-dwarf pears in high wind using the same sprayer settings to apply a fungicide to nursery whips in high humidity? I hope not.
The process is more intensive at the beginning of the spray season and again around mid-season (e.g. petal fall or whenever the crop changes sufficiently to require a reassessment). It’s described step-by-step in many articles on this website as well as in Airblast101.
Yes, it requires an investment of time and effort, but the feedback makes subsequent adjustments faster, easier and more intuitive. There are strategies to reduce the number of adjustments required. Large operations can assign sprayers to blocks with similar crop architecture (e.g. one sprayer works large orchards, another sprayer works young or high-density orchards). Smaller operations can change the order in which crops are sprayed.
Validating sprayer output
This accounting activity ensures the sprayer is applying the intended rate at the intended speed. “Sprayer math” is really only theoretical; It helps the operator plan for how much pesticide and water must go in the tank and how long the job will require. How the sprayer actually performs may be a different story.
According to 1992’s “Tools for Agriculture” a horse can deliver 500 watts of power over 10 hours, but the camel can deliver 650 watts over six. And you thought establishing tractor speed was difficult. Photo Credit – R. Derksen, Ohio. Date and location of photograph is unknown.
Validating output, or calibrating, confirms that each nozzle delivers the desired rate and that the sprayer travels at the desired speed, so the crop receives the correct dose with no unexpected left-overs or shortages.
The operator should perform these activities at the beginning of the season and after any significant change to the sprayer set-up. Examples include new nozzles, new tractor tires, using a different tractor or after replacing a pump or any lines/hoses.
The validation (i.e. calibration) process is explained in our articles on testing airblast sprayer sprayer output and travel speed.
Conclusion
Be sure to perform all three calibration-related activities as required. This will keep records up-to-date, improve your spray coverage, and save you from unexpected sprayer malfunctions – almost all of which are preventable.
This article was co-written with Mike Cowbrough, OMAFRA Weed Management Specialist – Field Crops
The time and attention spent during sprayer loading is a worthy investment. It ensures that the products in the tank perform as intended and reduces the chance of physical incompatibilities.
The label
Pesticide labels are always the first point of reference. Labelled mixing instructions should be obeyed even if they contradict conventional practices (see Mixing order, below). Consult this article on tank mix compatibility for more information on how to quickly and easily consult labels for each of your tank mix partners.
The carrier
Typically, the carrier is water. Water plays a very important role in tank mixing that is often underappreciated. Take some time to read Les Henry’s 2016 Grainnews article called “The Coles Notes of Water Chemistry“. You can also read about pH and water hardness. It should be noted that pH and the resultant hydrolysis that can affect product half-life is typically an insecticide issue (not fungicide or herbicide). The famous example is Captan, which has a half-life of 32 hours at pH 5, but only 10 minutes at pH 8. Michigan State did a great summary (in 2008 and on US product formulations) which you can find here.
Finally, learn how to read a water quality report, here.
Carrier volume
Products dissolve better in higher volumes. The sprayer tank (vat, inductor, etc.) should be at least ½ full or water before adding the first product. In the case of a fertilizer carrier, it may look like water, but it contains high levels of salts that tie up free water and reduce solubility. For fertilizers, a higher initial volume of ¾ full is required.
Note the undissolved residue collected on these swatches of red material. Products dissolve faster and better in higher carrier volumes.
The incomplete dissolution of products can leave hard-to-clean residues, plug fluid lines, and result in a non-uniform application that reduces efficacy. The risk of incompatibility is greater with low carrier volumes and high product rates (especially dry formulations). This is a common problem in regions that use low water volumes to apply multiple tank mix partners.
Carrier and product temperature
Both carrier and product temperature affect mixing. Imagine mixing sugar in hot tea versus iced tea – more sugar dissolves more quickly in hot liquid. Here are three common temperature-related issues:
Dry formulations and liquid flowables take more time
to disperse (consider using a pre-mixed slurry).
Emulsified concentrates and oil might form gels
rather than milky blooms.
Water soluble packages might not dissolve completely
and could plug filters and nozzles – or clog the pump intake.
Note the undissolved residue collected on these swatches of red material. Products dissolve faster and better when carrier and products are warmer.
Note: Water and fertilizer are very different carriers. Beware of carrier-specific incompatibilities
Agitation
Agitation should be on-going during mixing and spraying. When agitation is too low, products may not disperse or suspend and can settle out. In the case of leaving a sprayer overnight without agitation, settled product may or may not resuspend. See this article.
When agitation is too aggressive (e.g. full agitation when tank is less than half full) product can foam, causing overflows or breaking pump suction during spraying. Over agitation can also cause dispersed products (e.g. emulsifiable concentrates) to separate and cause clumping that looks like curds.
Note: When agitating, the surface of the carrier should be closer to a simmer than a rolling boil.
Pace
Products may require more than five minutes between additions. This is especially important when carrier or product is cold, or when adding dry products. When products are added too quickly, they will not entirely disperse or suspend, which could result in a physical incompatibility with subsequent additions. Learn more about the importance of time and patience during loading.
While efficient sprayer loading is an excellent opportunity to improve your work rate, complicated tank mixes still require time between additions. To save some time, sprayer operators pre-hydrate dry products in a smaller tank or use an extra tank to pre-mix whole loads and simply transfer them over.
Note: Even when dry products appear to be dissolved, they may not be. Be patient
Product formulation
Product formulation is a complicated science. In the 1950’s a formulation might have three active ingredients and an inert filler. See the historic formulation index card shared by Dr. M Doug Baumann (formally with Syngenta, Honeywood). Today, a product can include ~40 ingredients with formulation testing lasting two to four years! The more products you add to the tank, the higher the risk of antagonism.
Note: If you experience physical incompatibility during loading, don’t blame the last product you put in the tank!
Mixing order
The order in which you add tank mix partners is critical. There are several acronyms around to help you decide on your mixing order. Here are the top three:
W.A.L.E.S. is not broken. In fact, formulation chemists expect it to work ~95% of time. Generally, soluble liquids are forgiving and can be added early or late. It’s the dry formulations and emulsifiable concentrates that require more care. When there are exceptions to the order, they are clearly indicated on the pesticide label.
W.A.L.E.S. is, perhaps, a bit simplistic. Products that fall within each “letter” have their own preferred mixing order that isn’t specified by the acronym. What follows is an expanded generic mixing order.
Water-Soluble Bags (WSB) – Allow them to fully dissolve and disperse.
Wettable Powders (WP)
Water Dispersible Granules (WDG, WG, SG)
Agitation to allow dry products to mix and disperse.
Liquid Flowables (F, FL): Including, in order, Suspension Concentrates (SC), Suspo-emulsions (SE), Capsule Suspensions (CS/ZC), Dispersible Concentrates (DC), Emulsions in water (EW).
In order: Emulsifiable Concentrates (EC): Microemulsifiable Concentrates (MEC) and Oil Dispersions (OD).
In order: Solutions (SN), Soluble Liquids (SL), Liquid Fertilizers and Micronurients (when not already premixed with fertilizer).
NOTE: Regarding adjuvants, always follow the label. If the label is silent, most water conditioning utility modifiers (e.g. compatibility agents, anti-foamers) should be added before pesticides. However, drift retardant utility modifiers are added dead last. Activator adjuvants like Non-Ionic Surfactants (NIS) and Crop Oil Concentrates (COC) tend to be added after pesticides, but are sometimes added based on their formulation, falling into order just like pesticides. Again, read the label.
An example
Micronutrients like sulfur (e.g. ATS) added to nitrogen-based formulations (e.g. UAN) can cause physical incompatibilities. This became a problem during “weed-and-feed” applications in Ontario corn, and thanks to the efforts of the pesticide manufacturer, we worked out a solution.
What follows is not only a good example of why mixing order is critical, but why growers should get into the habit of performing jar tests. Learn more about a real-world ATS example here.
Left: ATS and UAN premixed, followed by Primextra created curds. Centre: UAN, followed by low-load ATS followed by Primextra worked. Right: UAN followed by Primextra followed by high-load ATS worked.
Small-plot mixing order
Mixing errors are just as likely in small plot work as in commercial sprayers. Watch this short video case study describing mixing order for Elevore and glyphosate.
The jar test
Performing a jar test is like filling a sprayer in miniature. Follow all the same rules as filling your sprayer. Always wear personal protective equipment when performing a jar test. Do so in a safe and ventilated area, away from sources of ignition.
Read all product labels. Know the product formulation (which affects mixing method and order). Look for information about the influence of carrier pH, hardness and any requirement for adjuvants. Defer to label instructions should they differ from these mixing steps.
Shake any liquid products. This ensures the active ingredient and inert ingredients are thoroughly mixed.
If using water as a carrier, add 250 ml to a 1 litre glass jar. For oil or fertilizer, add 375 ml.
Agitate (stir) between additions. In a sprayer, agitation should continue throughout the mixing process.
Add products in order (see Mixing order, above). Scale back the weights/volumes used to match the concentration intended for an actual sprayer tank (e.g. 1 kg product in a 1,000 litre sprayer tank is 0.5 g product in a 500 ml jar test). In a sprayer, you would flush an inductor with water between additions.
Wait and check. Dry products and water-soluble packets must fully disperse and/or dissolve before adding the next product. Several factors affect the duration, but 3-5 minutes is typical. If testing water-soluble packets, include a ~1cm2 cutting of the PVA packaging.
Top up the carrier to 500 ml.
Measure pH using a digital meter (litmus papers may not be readable). This is best done after all products are added to account for their impact on pH and buffering capacity. If required, pH adjusters can be added at the end of mixing to ensure the solution is in the range required by the label.
Let the solution stand in a ventilated area for 15 minutes and observe the results. If the mixture is giving off heat, these ingredients are not compatible. If gel or scum forms or solids settle to the bottom (except for the wettable powders) then the mixture is likely not compatible.
Note: jar test will only reveal physical incompatibility between products – it will not reveal any other form of antagonism.
Compatibility kits
When performing a jar test you must maintain the same product-to-carrier ratio as in a full-sized sprayer tank. This math is made easier with commercial compatibility kits such as the one from Precision Laboratories (below).
Compatibility Test Kit: Five pipettes, three bottles, gloves, instructions. ~$10.00. (Photo: Precision Laboratories)
Such kits contain a few plastic “jars” and disposable micropipettes. By following the instructions included with the kit, you can easily reduce large labelled volumes (e.g. 1 kg of product in 1,000 litres) of multiple products to small volumes at the same ratio. In this case we assume the final volume would have been 1,000 L, and so we reduce all the quantities accordingly to get 500 ml. The following mixing order is provided as an example.
Order
Ingredient
Quantity for 500 ml or 500 g of product labeled for 1,000 L of final spray volume
1
Compatibility agents
5 ml (1 teaspoon)
2
Water soluble packets, wettable powders and dry flowables. Include a 1cm2 cutting of PVA packaging.
15 g (1 tablespoon)
3
Liquid drift retardants
5 ml (1 teaspoon)
4
Liquid concentrates, micro-emulsions and suspension concentrates
5 ml (1 teaspoon)
5
Emulsifiable concentrates
5 ml (1 teaspoon)
6
Water-soluble concentrates or solutions
5 ml (1 teaspoon)
7
Remaining adjuvants and surfactants
5 ml (1 teaspoon)
Records and delayed reactions
Keep
detailed records of what you mixed and how you mixed it. This is important for traceability
(e.g. CanadaGAP) and for tracking successes and failures for next year.
The jar test itself can become a valuable record if it’s labelled and left in the chemical shed. You will see if products separate, precipitate or form residues. This may indicate if you can let a tank mix sit overnight or if it will require special attention during rinsing.
For example, a grower tank-mixed Enlist with Manzinphos, which seemed to mix and spray with no issues until they were rained out and had to park the sprayer with 100 gallons of tank mix still in the system. The mixture turned to “lard”, plugging up all of the lines, filters, and the pump. They had no choice but to disassemble the sprayer and dig some of the substance out with screwdrivers (see the picture of the filter below). Perhaps if they had run a jar test and left the jar overnight this problem could have been avoided.
Some physical incompatibilities are not immediately apparent. This occurred overnight while the partially-full sprayer waited out a rain event.
Closed transfer
As a brief mention, an expansion of closed transfers systems for loading pesticides is on the horizon in North America. Manufacturers of these systems claim they will make loading more efficient, reduce operator exposure and reduce point-source contamination. Depending on the design, however, the operator may not be able to open pesticide containers to obtain samples for jar testing. This would be a great loss.
For more information
Learn more about physical and chemical incompatibility in our article on Tank mix compatibility. Be sure to download a copy of Purdue University’s 2018 “Avoid Tank Mixing Errors”. It is an excellent reference.
