In 2025 I ran a comparison between five florescent dyes and three UV lamps to determine which combination worked best for tracing spray deposition. If you haven’t read part 1, go do so and come back.
In early 2026 my colleague and I used the winning combination to evaluate spot sprayer deposition in an onion field, and it worked “OK”. Only “OK”. In fact, I think many of the growers attending that twilight meeting were being polite when they said they could clearly discern the coverage. The fundamental problem was that we required almost complete darkness for the dye to be visible, and even then, you had to hold the lights just right. Photography was nearly impossible.
That’s when my colleague showed me that I’d brought a knife to a gunfight when he illuminated the scene with a new UV lamp. It was a veritable lightsaber! The high wattage and different wavelength changed everything. I knew immediately that we would have to redo the dye comparison in “light” of this new development.
The Old (left) and the New (right).UV dyes are more easily discerned at twilight or darker. Note that this image was taken while it was still light outside using the new UV lamp. A game changer.
In September, 2026 we returned to Falcon Blueberries to paint the town red (well, green, orange and yellow). The images, which were taken with a cellphone, are stunning and yet they really don’t capture what we were able to see in person.
Dyes Used
We used the same dyes, mixed in the same ratios with NIS as in the previous study:
Risk Reactor IFWB-C81PT
Risk Reactor UVTRACER-G1PT
Eco Pigment Blaze Orange SPL15JX
Tri Art Fluorescent Yellow Tempura Paint
We omitted the Phosphor Powder (Zinc Orthosilicate: Manganese CAS#11-47-2) used in the last study because the SDS really didn’t qualify it as non-toxic, and it’s not within reach of most people. Also, you won’t see any photos of the Tempura paint, because there was nothing to see. Historically, I’ve held out hope that it was a viable option, but it’s really only ever worked when super-concentrated and applied by a hand sprayer. So, if you’re doing that, go ahead, but I’ll never use it in a commercial sprayer again.
Application
We used the same Turbomist airblast sprayer, and the operational settings aren’t really relevant, here. Suffice it to say we made a single pass with their conventional settings, and left 8 rows between blocks (that is, a buffer of four rows on each side of the pass) to ensure we didn’t cross contaminate the dyes. Then we waited for dark.
Even in daylight, dye helps visualize spray. Those top nozzles should have been off, but this was a post-harvest mock-up. When the bushes were larger and fuller there would have been better interception at the top.Adding colourful, non-toxic dye to a completely clean sprayer proved very interesting to the next generation of Falcon Blueberries.
Risk Reactor IFWB-C81PT
This dye was pretty spectacular, which it absolutely was not when we tried last year using the weaker UV lamps.
IFWB-C81PT – Immediate row (sprayed directly).IFWB-C81PT – Next row over (sprayed indirectly).
Risk Reactor UVTRACER-G1PT
This dye didn’t perform well. It didn’t seem to leave any residue other than accumulated runoff (drip points) at the tips of the leaves. It wasn’t the volume or adjuvant, because while there was some runoff with the other dyes, they were nothing like this. We speculated it was a function of the dye’s formulation. On the up side, we did capture a few good photos of bad coverage when applying a foliar product.
Risk Reactor UVTRACER-G1PT. Incurred run-off on the immediate row (sprayed directly) and was not visible beyond this row.
Eco Pigment Blaze Orange SPL15JX
Once again, this pigment put on a quite a show. Whole not unique to this dye, we noted particular accumulation along the veins of the leaves where we suspect the pigments (which are not water soluble) collected. It was also visible on the petioles, under-leaf surfaces and the stems, branches and trunks.
Not only did we see it three rows out, but it was all over the ground, the hood of the tractor, the operator’s boots and pretty much everywhere the sprayer went.
The last few shots are a public service announcement. The TOPPS water protection project in Europe once performed a study on a variety of airblast sprayers to determine where pesticide residue accumulated. They concluded that the header was the worst offender (that is, the booms, air ducts and fan at the rear of the unit).
While we saw evidence of dye deposition all over the sprayer, and on the tractor’s radiator grille (air inlet), the sprayer header was by far the most contaminated region. Always assume an unwashed sprayer has residue – wear your PPE.
Four dyes, one pass each, and no wind left the sprayer header completely covered. We would expect far more accumulation following an actual spray day. Do not touch contaminated application equipment, even if it appears clean, without PPE.
Thanks to Cesar Cappa, OMAFA Horticultural Weed Specialist for introducing the new UV lamp, for the photography, and for not complaining every time I blinded him with the light. Thanks to Falcon Blueberries for their time and collaboration.
Sprayer math can be intimidating, but the effort gives solid value. When combined with a calibrated sprayer you reap the following benefits:
Determine how much spray mix is required to apply the intended rate.
Estimate how much crop protection product must be ordered for the season.
Populate spray records which allow you to review practices, respond to enquiries and satisfy traceability requirements.
There are many ways to perform sprayer math, and you need only look to local pesticide safety courses, industrial catalogues, and extension resource centres for examples. If you’re already comfortable with your current method, don’t mix and match with others. Sprayer math is a series of related calculations that employ constants to keep the units straight. It’s all or none.
Walkthrough
Let’s start with the classic, US Imperial formula for calculating the sprayer output. We’ll weave in Metric, later. This base formula can be adjusted to allow you to solve for any factor, as long as you’re only missing one piece of information. Turns out your high school teacher was right – you DO need algebra.
GPM = [GPA x MPH x W] ÷ 5,940
In this case, you can determine an output rate (GPM – gallons per minute). You’ll need to know your target volume (GPA – gallons per acre), your average travel speed (MPH – miles per hour) and your nozzle spacing (W – which is width in inches). The number “5,940” is a constant that handles all the unit conversions. If you divide the GPM by the number of nozzles on your sprayer (assuming they are all the same rate), you can hone in on the ideal nozzle size.
But, as we noted earlier, you can do a lot more with sprayer math than just pick the ideal nozzle size. The rest of this article includes examples of both Metric and US Imperial formulae, but watch out for unit conversions. If at any time you don’t see the units you’re looking for, you can consult our unit conversion tool.
Grab your calculator – it’s math time!
Don’t be intimidated. With a little practice, sprayer math gets easier and it’s always worthwhile. The real trick is navigating unit conversions.
Step 1 – How large is the area you need to spray?
Multiply the length of the area you plan to spray times the width. If you are using metres, then divide the product by 10,000, which is the number of m2 in a hectare (ha). For feet and acres, divide by 43,560 which is the number of ft2 in an acre (ac):
Step 2 – How much product is needed to spray the area?
Consult the rate(s) shown on the label. In Canada, rates are often based on planted area (E.g. hectares). In Australia and New Zealand, they may be based on row length (not covered in this article). If you measure your area in acres, you’ll have to convert the rate by multiplying by a constant: 0.4.
Now multiply the area you want to spray (step 1) by the rate (step 2).
Step 3 – How far can you go on a full tank?
You know your sprayer output (determined through calibration) so you divide that into your tank size. Watch your units:
Step 4 – How much pesticide per tank?
Multiply the area that can be sprayed per tank (Step 3) by the pesticide rate (Step 2). Again, watch your units:
Step 5 – How much area is left to spray?
Just subtract what you’ve already sprayed from the total area.
Step 6 – How much pesticide in the last, partially-full tank?
Multiply the area you have left to spray (Step 5) by the pesticide rate (Step 2). Yes, watch your units:
Step 7 – How much spray mix will I need for the partial tank to finish spraying the total area?
Multiply the area you have left to spray (Step 5) by the sprayer output (determined through calibration). Guess what? Watch your units:
Sample problems
Time to test your knowledge. Let’s suppose you want to apply a product rate of 3 L/ha to your blueberries. You calibrate your sprayer and determine your output to be 50 L/ha. Your tank holds 400 L of spray mix. Your planting is 500 m long and 200 m wide.
Q1 – How large is the area you need to spray?
Q2 – How much product is needed to spray the area?
Q3- How much area can be sprayed on one tank?
Q4 – How much product should be added to a full tank?
Q5 – After the tank is empty, how much area is left to spray?
Q6 – How much product to add to the last, partially full tank?
Q7 – How much spray mix will be needed to finish spraying?
Tank mix calculator
You might feel we buried the lead by adding this calculator to the end of the article. It’s important for a sprayer operator to understand the math required to interpret labels and calculate tank mixes, so hopefully you read and understood the process before you got here. And now that you have, this is a very helpful tool. Try it online, or download a standalone version.
Notable exceptions
Certain situations aren’t covered in this article. If you are spraying a greenhouse, the math is different. If you are performing a banded application, the math is different. And, if you’re an airblast operator trying to reconcile why a pesticide label uses planted area rather than canopy volume for its rates, you’re in for some additional reading.
Canada, like most of the world, is officially Metric. America operates using the US Imperial system. It sounds very cut and dried, doesn’t it?
However, anyone that’s tried to calibrate a sprayer in Canada quickly discovers that we’re really an amalgam of the two systems. We like to call it “Mock-tric“. By way of evidence, some operators still adhere to the dreaded L/ac. You know who you are. To be fair, some of our sprayers and nozzles originate from the states, meaning nozzle tables and rarely, sprayer indicators, can be in US Imperial.
This leads to mind-bending questions such as:
I drive 12 mph, spraying 150 L/ha and my pressure is about 40 psi. How many ml/min should my 72 nozzles emit for a product that wants a 6 oz/acre acid equivalent?
Cue the quiet sobbing…
Frustrated back in 2017, we created a set of conversion tables to help operators with almost any Imperial/Metric emergency. Admittedly, they were in 4-point font and therefore too cumbersome for practical use. We’ll keep one here for posterity.
The good old days of “look-up tables”. RIP.
Happily time has marched on and we now have a better way. Explore our new Sprayer Calibration and Unit Conversion Tool, below. While it doesn’t do it all, it certainly does a lot! You can:
Convert between common (and some uncommon) agriculturally-relevant units.
Calibrate a field sprayer for both broad acre or banded applications.
Calibrate an airblast sprayer for almost every traffic pattern and swath width.
Calibrate a plot sprayer, either for a handheld boom (any number of nozzles) or for a backpack sprayer mist/wand in 3D rows.
Calibrate a fogger for common closed environment structures
To use this suite of calculators correctly, the user needs some agronomic understanding of what these variables mean and how to obtain them. In order to provide context, and reduce the friction, we’ve added a link to relevant articles at the top of each calculator.
Grab an offline version here, or try it out below. We’ve tried to validate every path, but if you find a bug, please let us know. Once you know your calibration settings, go here to determine how much goes in the sprayer tank.
Drone operational settings such as capacity, speed, and swath width are useful figures for calculating productivity, but they only describe the airborne portion of the job. A commercial application business must also transport water, mix product, charge batteries, and establish an efficient staging area that is both safe for operators and maintains drone connectivity. If any of these functions fall behind, productivity suffers.
We consulted several mission records to develop a productivity calculator that can model a range of scenarios. We assumed a shuttle (back-and-forth) flight pattern to apply successive spray swaths for uniform coverage of a treatment area. Download our offline version or try it online at the end of this article.
How to use
In this, version 3.0 of our drone productivity calculator, we’ve expanded the functionality to include several tendering options. If you are uncertain what the variables mean, consult this handy instruction manual to walk you through the process.
Use it as a planning tool, or simply as a way to explore the impact of different operational settings on mission productivity. We propose adjusting variables one at a time to determine their effect. You can then compound the effect by changing another, or return to the base value and choose another variable to manipulate. In this way you can explore the relative influence of each variable on the overall job.
Which factors matter most?
The relative impact of each operational setting (or the geometry of the target area) on productivity is situation-specific. Nevertheless, here are some generic observations:
While swath width and flight speed play a role, both are limited by the agronomic realities of the job. So, while you can change them in the calculator, it does not follow that the results of the application will be successful.
Water rate (e.g. L/ha) has an impact on productivity, but once again there are agronomic considerations. Too low a volume can compromise product efficacy and contribute to off target drift, and quite often the minimum volume is stipulated on the product label.
The drone’s tank capacity depends on the model, but maxing it out may not be the best option. Some large drones suffer reduced battery life and slower acceleration when filled completely. Note that when the user forces a refill/battery swap, there will be spray mix left in the drone. It is prudent to minimize this residual by not overfilling the drone in the first place.
The ferrying distance between where the drone empties and the staging area a critical productivity factor, so minimizing it is a reasonable objective. Doing so can mean additional sorties, which require additional refills and battery swaps. Small improvements here compound into big impacts, but pay close attention to see if the additional sorties are worth the time savings.
The number of operators have a significant effect on productivity. If a solo operator has to retrieve additional water, or move the tender truck to a new location, the drone isn’t spraying.
Batteries – A potentially limiting factor
The calculator assumes that a sufficiently charged battery is ready whenever the drone returns to the tender, so battery charging does not extend the entered refill and battery-swap time.
In practice, flight endurance can change dramatically with payload. For example, a heavily loaded aircraft may fly for only a few minutes, while the same aircraft may remain airborne much longer with an empty tank. Repeated short, high-load sorties may therefore consume charged batteries faster than they can be recharged.
If the battery inventory, chargers, generator capacity or electrical supply cannot keep pace, the crew may eventually have to wait for batteries, reducing actual productivity below the calculator’s estimate. Additional batteries, higher-capacity charging equipment or improved generator capacity may be required to sustain the projected workflow.
Thanks to Mike Verhoog (Drone Spray Canada) for reviewing and contributing to the design of this model.
Airblast sprayer operators must know their average travel speed to calculate how much pesticide and time is required to complete a spray job. Note that it’s an average, not a constant, because travel speed is significantly affected by ground surface conditions (e.g. slippage), grade (e.g. hills) and the weight of the rig (e.g. as spray mix is depleted).
The pursuit of productivity and the unchallenged status quo of traditional spray volumes, blinds many operators to the fact that travel speed is a critical factor in focusing air energy on the target canopy. As long as droplets are small enough to be entrained and directed by the air, we believe that optimizing the fit between air energy and the target canopy leads to the most frugal and effective use of spray mix and should therefore dictate travel speed. If that speed proves to be painfully slow, or terrifyingly fast, then a mismatch is revealed between the sprayer design and the operational conditions and the overall spraying strategy should be reconsidered.
This article describes a method for modelling an ideal travel speed. It can be used as a sanity check for existing operations or for those seeking to evaluate the fit of a new airblast sprayer. However, this method can only approximate travel speed. A true optimization of sprayer settings will require fine tuning using the ribbon method and, ultimately, coverage feedback from water sensitive paper (see here and an older article here). We’ll begin with how to measure average travel speed.
How to measure average travel speed
Beware the tractor speedometer or rate controller that monitors wheel rotations; both can be fooled by changes in wheel size, tire wear or slippage. GPS or radar-based speed sensors are the most accurate method.
Those that prefer a manual method can follow this classic protocol for determining average travel speed:
Go to a row that is representative of the terrain in your planting. Measure out a distance of 50 m (150 ft) and mark the start and finish positions with wire marker flags.
Fill the sprayer tank half full of water.
Select the gear and engine speed in which you intend to spray. If using a pull-behind sprayer, ensure the PTO is running or you could introduce errors.
Bring the sprayer up to speed for a running start and begin timing as the front wheel passes the first flag. This is far easier when there are two people.
Stop the timer as the front wheel passes the second flag.
Stay out of any ruts and run the course two more times.
Determine the average drive time for the three runs (i.e. the sum of all three times in seconds divided by three).
Finally, calculate travel speed using one of the following formulae, depending on preferred units:
Ground Speed (km/h) = Average drive time for 50 m (s) ÷ 13.9 (a constant)
Those that prefer a less accurate but convenient hack can download any smartphone speedometer app that can calculate an average (similar to a runner’s GPS wristwatch). Fill the sprayer tank half full and drive a representative section of your operation with the fan on and the spray off. Consult the phone for your average speed for each pass. Take a screen shot and email it to yourself as a time-stamped component of your spray records.
The “Air Displacements” method
Dwell time
Airblast sprayers use fans to move a volume of air at a certain speed, often measured in m3/hr or ft3/min. Imagine that volume of air as a three dimensional shape extending from the air outlet over a distance. Likewise, imagine the void between the sprayer outlet and the target canopy as a three dimensional shape penetrating roughly halfway into that canopy (assuming we intend to spray every row).
How long must the sprayer dwell in one spot before it pushes all the intervening air out of the way and replaces it with spray-laden air? If the sprayer drives too slowly, it will wastefully push spray through and beyond the target (i.e. blow-through). If the sprayer moves too quickly, the spray will not have an opportunity to penetrate the target canopy and most certainly not reach the highest point. This concept of focusing air energy using travel speed is called Dwell Time.
We want to calculate the volume of air the sprayer generates, compare that to the volume we want displaced, and then determine how fast we must drive to optimize the fit. We can do all this with a tape measure, an anemometer, and a partner to record the data and do a little math.
1. Measure air outlet area
With the sprayer safely off, measure the area of the air outlet(s) on one side of the sprayer. We’ll use a Turbomist 30P Low Drift Tower (below) as an example. There are two air outlets that are 5 cm wide by 150 cm high for a total area of 0.075 m2 on each side. Be sure to look inside the outlet for any irregularities like baffles or obstructions intended to block air. Subtract those areas from the total. Don’t worry about small things like nozzle bodies.
For rectilinear outlets: Height (m) x width (m) = Area (m2)
For circular outlets: 3.14 x radius2 (m) = Area (m2)
The air outlet on this Turbomist 30P Low Drift tower sprayer is 5 cm wide by 150 cm tall for a total area of 0.075 m2.
2. Measure air speed
First, a few safety warnings: High speed air is loud and can carry debris, so always wear ear and eye protection and respect the hazards inherent to working with air-assist sprayers. Only use an anemometer rated for at least 160 km/h (100 mph) (e.g. here). Do not use a handheld weather meter such as a Kestrel because the impellor could be destroyed and become dangerous shrapnel.
Use an anemometer rated for at least 160 km/h (100 mph) (e.g. here). Do not use a handheld weather meter such as a Kestrel because the impellor could be destroyed and become dangerous shrapnel.
Bring the fan up to speed and holding the meter about 25 cm (10 in.) from the outlet, measure the air speed at several locations along the air outlet both vertically and horizontally. We calculate an average speed because many air outlets do not produce uniform air speed or volume along their outlets. For this example, we measured four locations along the air outlet on both sides of the sprayer and saw significant differences. We did this both in low and high gear (see table below).
High Gear
High Gear
Low Gear
Low Gear
Location Along Outlet
Left Side (m/s)
Right Side (m/s)
Left Side (m/s)
Right Side (m/s)
Top 1/4
41.1
80.3
42.9
24.6
Upper
34.9
32.2
26.4
30.8
Lower
30.8
30.0
24.0
26.4
Bottom 1/4
33.5
40.2
26.8
31.3
Average
35.1
45.7
30.0
28.3
Anemometer readings from the low drift tower sprayer outlets, on left and right side, in high and low fan gear. Four readings from bottom to top to determine the average. Readings taken 25 cm from edge of outlet and PTO set to 540 rpm.
Multiple air outlets
Before we continue with the method, let’s change sprayers to this Turbomist 30P Grape Tower (below). The design is intended to spray adjacent rows from the vertical outlets (5 cm x 150 cm = 0.075 m2) along the tower. The upper, inverted outlets (10 cm x 63.5 cm = 0.0635m2) throw spray over the adjacent rows and cover the outside rows. The intention is to improve productivity by covering four rows of grape (or possibly three) per pass.
The Turbomist 30P Grape Tower Sprayer is a multirow system intended to drive every third or fourth row.Lower, vertical ducts are 5 cm x 150 cm = 0.075 m2Upper, inverted ducts are 10 cm x 63.5 cm = 0.0635m2
However, when we consider this design through the Air Displacement lens, it’s almost like having two sprayers performing two jobs simultaneously. The vertical outlets and the upper, inverted outlets are different shapes. Further, their position (distance and angle, as the top outlets are angled back more aggressively) relative to their respective target canopies are significantly different. How fast must this sprayer drive to optimize the fit? Do we have to compromise coverage and incur drift and waste from one set of outlets to accommodate the other set? The manufacturer has worked to address this potential issue by partitioning the majority of the air energy to the top outlets, but let’s see how that affects travel speed.
3. Total volumetric flow
Having already measured the outlet area, we then measured average air speed (see table below).
High Gear
High Gear
Low Gear
Low Gear
Location Along Outlet
Left Side (m/s)
Right Side (m/s)
Left Side (m/s)
Right Side (m/s)
Top Outlet
27.0
26.5
27.0
26.0
Bottom Outlet
12.0
13.0
10.5
12.5
Average anemometer readings (n=4) for top and bottom outlets, on left and right side, in high and low fan gear. Readings taken 25 cm from edge of outlet and PTO set to 540 rpm.
Now we can use these two values to determine how much air the sprayer generates by calculating total volumetric flow. We first have to convert air speed from m/s to m/h to make the units work, so just multiply it by 3,600. Then we multiply that by the outlet area and we get the table below.
Average air speed (m/s) x 3,600 (a constant) = Average air speed (m/h)
Average air speed (m/h) x Outlet area (m2) = Total volumetric flow (m3/h)
High Gear
High Gear
Low Gear
Low Gear
Location Along Outlet
Left Side (m3/h)
Right Side (m3/h)
Left Side (m3/h)
Right Side (m3/h)
Top Outlet
6,172.0
6,058.0
6,172.0
5,944.0
Bottom Outlet
3,240.0
3,510.0
2,835.0
3,375.0
Total volumetric flow for top and bottom outlets, on left and right side, in high and low fan gear, with PTO at 540 rpm.
4. Target volume to displace
Now that we know the volume of air the sprayer generates, let’s determine the volume of air we need to replace with that spray laden air. This is really the only tricky bit because you have to picture a cross section and then measure the shape. See the illustration below.
For the bottom outlet, it’s simple. The outlet is 81 cm from the grape panel and the grape panel is 112 cm high. We calculate the area of a rectangle by multiplying length by width, so:
Length (cm) x Width (cm) = Area (cm2)
However, the sprayer design makes the top outlet’s job trickier to figure out. This isn’t a rectangle, it’s a “quadrilateral”. We get this odd shape when either the sprayer outlet or the target canopy are significantly taller than the other. Fortunately this one has a right angle so we don’t have to brush off our high school trigonometry textbooks. Instead, we can lean on the internet using this link and plug in the values. As we can see below, the cross sectional areas spanning from the outlets and the middle of the target canopies are 0.9 m2 for the bottom outlet, and 2.35 m2 for the upper outlets.
This gives us a cross sectional area, but we need to convert that to a volume so we can compare the air generated to the air needed. To do that, we multiply the cross sectional area by 100 m, representing how much air would be needed over 100 m of row length. The formula and the results are presented below.
Cross sectional area (m2) x 100 m of row length = Target displacement volume (m3)
Outlet
Target Displacement Volume (m3)
Top Outlet
235.0
Bottom Outlet
90.0
Target displacement volume for each outlet over 100 m of canopy row.
5. Displacement rate
We see the target displacement volumes for each outlet are significantly different. Assuming the air from the upper outlet maintains its integrity and reaches its target canopy without being blown off course, it must produce enough air energy to fill more than twice the displacement volume of the lower outlet. We can see from the earlier calculations that it does produce almost twice the total volumetric flow. But is it enough? To know we must calculate the Displacement Rate for each outlet. Let’s just focus on the left side of the sprayer in high gear.
Displacement Rate (displacements/h) for left side of sprayerin high gear
Top Outlet
26.25
Bottom Outlet
36.0
Displacement rates for the outlets on the left side of the sprayer in high gear.
So we see that the outlets at the top of the sprayer, if stationary, could displace the target volume of air 26.25 times an hour. However, the lower outlet would displace its target volume 36 times in that same hour. We see that we might have a problem. But this is for a stationary sprayer and not a sprayer in motion. The last step gives us what we came here for.
6. Ideal travel speed
We can now determine the ideal travel speed for this sprayer using that same 100 m row length.
[Displacement rate (displacements/h) x 100 m of row length] ÷ 1,000 (a constant) = Ideal travel speed (km/h)
Outlet
Ideal travel speed (km/h) based on left side of sprayer
Top Outlet
2.6
Bottom Outlet
3.6
Ideal travel speed for each outlet on the left side of the sprayer in high gear.
As we stated at the beginning of this article, this is only a model. It doesn’t account for canopy density and assumes the spray laden volume of air produced by the sprayer can reach the target intact over a given distance. However it does indicate that there is a potential issue that will lead to either over spraying the adjacent row (slower travel speed) or under spraying the distant rows (faster travel speed) which could lead to waste, drift and poor coverage.
In the image below, we chose to drive close to 2.6 km/h in high gear. No effort was made to adjust the liquid flow (i.e. change the nozzles) so there was too much spray volume here, but we can see the losses on the left (upwind) side, and the blow-through three rows over on the right (downwind) side. Leaving aside the excessive liquid volume, we could drive faster or reduce the fan gear to reduce the blow-through on the adjacent rows, but we may go too fast (or reduce the rate of air displacement) for the upper outlets to reach the target. We can already see the integrity of the upper-left outlet breaking down as it sprays into the wind.
Testing a travel speed. No effort was made to adjust liquid flow, which is excessive here. Cross wind was from the left to the right in the image. Photo by Corey Parker (Instagram: _parkerproductions)
Take home
An ideal travel speed for an airblast sprayer is more than just being productive. The spray must reach and penetrate the target. If this requires dangerously high speeds, or if you simply can’t move slowly enough, it suggests a problem with the spraying strategy. Changes will have to be made to the sprayer, the target canopy, or even the weather conditions you’re willing to spray in. Getting the job done quickly should not compromise the quality of the job. Use this method to re-evaluate your practices, or to assess the capabilities of candidate sprayers if you’re considering a new purchase. Be sure to confirm what this model is telling you using some coverage indicator, such as water sensitive paper.
Calculator
Now that you’ve read through the process, you can try this online calculator designed to make the process a little easier. The embedded illustrations are there for general guidance, and may not reflect the sprayer design, but the calculations work. Recognize that while this calculator will provide an idealized travel speed based on the data entered, it cannot judge whether the outcome is realistic. Obviously a recommendation to drive 25 km/h is unrealistic, but it does alert the user to the fact that the sprayer is overpowered. Try it out!
Dr. David Manktelow, Applied Research and Technologies Ltd., is gratefully acknowledged for patiently explaining the concept of “Air Displacements” to the author.
