Category: Speciality Sprayers

Main category for all sprayers that are not horizontal booms

Hol Spraying Systems – Canadian airblast gets an upgrade
The first modern airblast sprayer was developed in the mid 1900’s, but competed with existing equipment before it was adopted by the majority. As you can see below, we’ve come a long way. As application technology continues to evolve and grow, so does the array of choices facing growers.
An Ontario orchard spray crew c.1910. Pump pressure was maintained by the two operators at the right. The spraying rate by the above method could cover 1.2 to 1.6 hectares (3 to 4 acres) per hour. Image from www.farms.com
Provide Agro (a subsidiary of N. M. Bartlett Inc.) had been considering introducing a new airblast sprayer to Canada for more than ten years. After deciding not to get into the manufacturing game, they explored importing sprayers from Europe and Australia. In late 2014 they recently invited me to see their choice: the H.S.S. CF airblast sprayer built by Holland-based “Hol Spraying Systems”.
It’s not often I get to see a “new” airblast sprayer design. To be fair, H.S.S. has been building similar sprayers in Holland for more than 20 years, so technically it was new-to-me.
We met at a local apple orchard in Simcoe, where we ran the sprayer through a series of light duties. The first thing we did was explore the sprayer’s features, both optional and standard. As the ambassador to Canada, this particular model had all the bells and whistles. Here is a list of features and observations I feel are worth relating. It’s important to note that this list is in no way an endorsement, nor are any omissions intended to be a condemnation.
The H.S.S. CF sprayer. Outwardly this PTO-driven sprayer appears very different from Ontario’s typical fleet of airblast sprayers. Notably the flexible ducts and gantry comprising the tower, and the double axle. However, it operates using the same principles as our more familiar sprayers and following a brief inspection of welds and fastens (and given its more than 20 year history in Europe) it appears to be very durable.
Each duct is paired to a nozzle body, and that means each air outlet can be adjusted individually. The tower structure can be customized to match everything from vines to high-density orchards and even has an optional woolly aphid attachment for directing air and spray up-and-into the canopy. For taller crops like hops and semi-dwarf trees, a second fan can extend the tower to 5.5 m.
Anyone that’s been stuck in wet weather can appreciate the value in this adjustable double axle. Weight is distributed to reduce compaction and hopefully, the creation of ruts. This feature is standard, but you have the option to upgrade to hydraulic adjustment. I’m not sure how often an operator would want to adjust the axle length, but there it is.
The H.S.S. CF has a lot of features that promote operator safety by reducing the potential for exposure. One convenient feature is the access port separate from the tank fill port. No need to remove the basket to examine/clean the interior, and no need to remove the basket and come in contact with (potentially) concentrated pesticide residue.
Many large field sprayers feature tank rinse nozzles to facilitate sprayer cleanout following an application. Finally, airblast can boast this feature as well. The 150 L clean water tank supplies enough water to the tank rinse nozzles for a triple, low-volume rinse in the field with no need for a pressure washer or a nurse tank. This prevents residue buildup and reduces operator exposure – and it’s standard!
An optional feature is the tank level sensor, which can be tied to the agitation. If you are using a foamy tank mix, agitation won’t turn on until a preset tank level. I’m not certain about this option because proper tank suspension requires agitation from the beginning – just use a defoamer. Note the tank basket has a hose attached to the bottom… read on.
There’s a standard hydraulic jet at the bottom of the tank basket to assist in proper mixing. I don’t know if it precludes mixing a slurry, or if it will improve pesticide bag dissolution, but I have to assume it helps. I trust there’s a safety feature to prevent this nozzle from operating while the hatch is open, but I’m not certain.
This final standard feature may seem small, but it further reduces the potential for operator exposure. The onboard clean water source is separate from the spray tank and the tank-rinse supply and provides a convenient hand-wash station.
Other features include solenoid shut-offs for boom sections, a rate controller and a small-radius draw bar.
An important function of any airblast sprayer is air handling. Too often, tower sprayers have inconsistent air speeds (and presumably air volumes) over the length of the air outlet. Sometimes this can be compensated for using the small deflectors in the tower, or in extreme cases, replacing conventional hollow cone nozzles in “dead spots” with air induction hollow cones that produce coarser droplets and tend to fly farther under pressure. Using a Pitot meter, we examined the airspeed from each air outlet. The PTO was set to 400 rpm and the fan gear was in low.
Nozzle: Ground 2 3 4 5 6 7 Top
Left 70 mph 85 mph 90 mph 85 mph 80 mph 85 mph 80 mph 85 mph
Right 75 mph 90 mph 90 mph 90 mph 80 mph 90 mph 85 mph 85 mph
There were no obvious dead spots, and the left and right sides of the tower seemed about equal. The bottom two positions were notably slower than the rest, but given the distance to the target in that position, and the fact that ambient wind is slower at the ground, it’s interesting, but not necessarily a concern.
We arranged a set of water-sensitive targets in the canopies of semi dwarf apple trees to get a sense of the sprayer coverage. Admittedly, it was very humid and there was little wind that day, so coverage is much easier to achieve because so little spray evaporated or was blown off course before reaching the target. We ran different combinations of PTO speed and fan gear. These images are from 540 rpm and low fan gear using red Albuz nozzles (1.5 L/nozzle/minute @ 6 bar) spraying about 400 L/ha at about 5 kph. On a drier and windier day, higher volumes would be needed.
There were no obvious misses, even when papers were oriented parallel with the ground (exposing their narrow edge to the sprayer, such as in the paper on the right). This isn’t conclusive, but it does show that the sprayer had no trouble penetrating the canopy, and with further tweaking should be able to provide suitable coverage throughout the canopy. Personally, given the upward orientation, I would use the woolly aphid nozzle for all applications, particularly for drenches. More on that later.
One notable quality was the “quiet” operation of the sprayer. Applicators are familiar with the loud whine created by most airblast sprayers; at lower rpm’s and in low fan gear, the tractor seemed as loud (or even louder) than the sprayer operation. You can watch a video of one of the spray passes at the bottom of this article.
So the big question: “How much?”. You’ll have to contact the dealers to find out more, but I will say that stripped down to standard features, it’s comparable to some of the more expensive sprayers in Ontario. Don’t be dissuaded because I believe the expense is warranted given the features, with particular note of the on-board tank rinse system and adjustable air ducts.
So is this the sprayer for you? Well, if you’re in the market for a new sprayer, always start by prioritizing your goals. Perhaps work-rate is a priority, so look to sprayer capacity to reduce the number of refills and consider over-the-row technology (where possible) to reduce the number of passes. Perhaps the crop is adjacent to sensitive areas or residential homes and drift control is a priority; consider adjustable air direction and adjustable air speed.
When compiling a prioritized list, reflect on the positives and negatives of your current sprayer and talk to fellow growers about their experiences. It may come down to personal preference, but consider the following points. These points are in no particular order; they come from many articles I’ve read on the subject of considering new equipment purchases and from talking to dealers, mechanics and sprayer owners:
- Necessity – Is a new sprayer really needed? Manufacturers have a number of retrofit kits available to upgrade and improve sprayers. If poor pesticide performance has led to the decision to purchase a new sprayer, be sure it’s related to the technology, and not to an operating error.
- Crop Type and Acreage – Consider the size of the operation and the size, shape and density of the crop(s). Can the sprayer adapt to provide adequate coverage throughout the growing season and in the long-term? How flexible is the sprayer when spraying different products onto different targets?
  • Sprayer Capacity and Filling – Fewer refills means a higher work rate, but increased capacity also means more weight, so consider the effects on navigation, turning radius and soil compaction. Is the tank easy to fill?
- Cleaning, Calibrating and Maintenance – Moving between crops sometimes requires complete cleaning and decontamination of the tank, lines, nozzles and any shrouds or ducts. Clean water reservoirs, tank-rinsing nozzles and overall accessibility should be considered. Review the steps required to winterize and to calibrate the sprayer. Is it easy to access parts? Is operator exposure minimized
- Horsepower – This is an important consideration for airblast sprayers because fans move a lot of air and liquid. Tank agitators require power, too. Consider selecting from the higher range of manufacturer-recommended horsepower to improve longevity. Remember, however, that fans typically don’t have to operate at the maximum rated rpm’s, particularly early in the season.
- Nozzle Technology and Operating Pressure – Consider the range of nozzle-types intended for use and ensure the sprayer can provide sufficient pressure. While more expensive, diaphragm and piston pumps have fewer moving parts in contact with the spray solution, reducing cleaning time and operator exposure.
- Spraying Conditions – A sprayer has to be reliable, even in adverse conditions, so consider the operating environment. Night spraying, uneven terrain, high winds, dry conditions – many environmental factors can impact sprayer performance and may warrant special consideration. Investigate deflectors, shrouds and the structural framework and durability of the sprayer.
Since its introduction in late 2014, growers have been slowly adopting this sprayer in Ontario and the northern US. Some high-density operations have purchased the optional over-the-row boom system that allows them to spray multiple rows at once. Here at at the Simcoe Resource Station, we’re hoping to run the HOL sprayer in apples for the 2016 season to see if the optional woolly apple aphid (WAA) nozzle has any impact on scale, mites and of course, WAA control. Moreover, we plan to run that nozzle all season long to see if its upward angle improves underleaf coverage and canopy penetration.
April 8, 2016
Continuous Rinsing
We’ve recently been talking about how to save time while cleaning a sprayer. Although it’s very important to be thorough while cleaning, and to take the necessary time to do the job properly, there is always an opportunity to fine tune and spend less time. This is especially true when diluting the tank remainder down and pushing clean water to the booms. A method promoted in Europe, and coming to us via Joachim Herfort of Agrotop, is called “Continuous Rinsing”.
Continuous Rinsing requires a dedicated pump that delivers the clean water (which may contain a cleaning adjuvant) to the tank via wash-down nozzles. It works like this:
1. The operator, having carefully measured the pesticide mixture, has only a small remainder in the tank when spraying is complete.
2. This remainder is sprayed out in the field, either on a set-aside area, or over the already sprayed field at a reduced rate, product permitting (the operator would pay attention to crop tolerance and carryover issues)
3. As soon as the tank is empty, indicated by the boom spray pressure dropping, the operator switches on the clean water pump which delivers the clean water via the wash-down nozzles.
4. Soon, the main product pump starts delivering the wash-down liquid to the boom and the return lines.
5. Because the clean water pump will deliver less than the boom flow, the cleaning mixture is delivered somewhat intermittently. We are told that this helps with the cleaning action of the lines. Be cautious that the main pump does not run dry long enough to damage its seals.
6. Once the clean water tank is empty, the pressure drops again for the final time and the tank rinsate is now very dilute.
7. Testing in Europe has shown that the whole process takes only about half as long as batch mode. One key time-saving feature is that the sprayer never has to stop, and the operator never dismounts. These data also show that a significantly lower water volume is required to achieve a greater dilution of the remainder than a batch mode would have achieved.
8. For example, the European tests (we believe these were done by the Landwirtschaftskammer of Nordrhein-Westfalen, a German regional government) used a single rinse of 80 L, as well as four batch rinses of 20 L each. As expected, the four-batch process was superior to the single rinse, but took a lot of time. They then tested a continuous rinse with 40 L. The continuous rinse resulted in greater dilution than the 4 x 20 L rinse, in less time. In this case, the quality went up, and the time went down.
Our challenge in North America is to roughly match the clean water pump, wash-down nozzles, and main sprayer pump capacities so the system works. Our larger sprayers easily deliver 30 gpm, and some adjustments may be necessary.
Dilution of the tank remainder is only one aspect of sprayer cleaning. The other aspect, decontamination of surfaces and components, is also important and the process depends on the active ingredients and formulations in the tank.
An animation developed in Germany and shared via Agrotop is available here.
Note that Agrotop has suggested components to convert a sprayer to a continuous rinse system here.
March 22, 2016
Top Sprayer Retrofits
You’ve got an older sprayer. Your neighbours have newer sprayers. For various reasons, you’ve decided against a trade. How can you still get the benefits that newer sprayers deliver? Let’s explore how to improve your sprayer performance and productivity with strategic component upgrades.
Most of the biggest gains will relate to the plumbing, especially filling and cleaning. Here is a list to think about:
Nozzles. This one’s a no-brainer. Nozzles remain the cheapest and most important part of any sprayer, affecting coverage, drift, and accuracy. Although durable, nozzles do wear or get damaged over time. But perhaps more important is the changing use patterns of our pesticides. We are moving into a time of greater reliance on tank mixes that blend systemic and contact products, and also higher water volumes into mature canopies. For example, fungicides for Fusarium Head Blight benefit from twin fan nozzles. We’re also seeing new herbicide registrations with greater spray quality (droplet size) restrictions, requiring coarser sprays or higher water volumes to maintain acceptable drift amounts. Are your nozzles able to meet those needs?
Nozzle bodies or turrets. As we move towards more specialty applications, perhaps we need a greater selection of nozzles at our disposal at any given time. Bodies with 5-nozzle turrets are standard on newer sprayers, and these make sense. Burnoff, in-crop, fungicide, and fertilizer nozzles are four that most users will need just from flow-rate needs alone. But some finer or coarser options of each may also be justified, and easy access saves time in the field. New bodies also provide new seals, and the newest offer higher flow rates and exchangeable parts.
Boom end cleanout. Removing residue or air from booms is an important part of good practice. Many sprayers already have manual valves that allow this to happen relatively easily, but it’s still a process that an operator has to make time for. And on top of that, flushing boom sections results in massive doses of pesticide on the soil. One of the most innovative inventions in recent times is Hypro’s Express Nozzle Body End Cap. A DIY or dealer installation of these units allows your boom to bleed introduced air on the go. The ENBEC also forms a dead end exactly at the last nozzle position, eliminating the dead spots that introduce contamination after a pesticide switch. Cleanout and shutoff response also improves. A fast boom flush is straightforward by moving the turret to an open position. TeeJet offers a Rapid Stop extended inlet tube that evacuates trapped air from the wet boom, can be retrofitted on most bodies. Wilger Combojet bodies offer a similar design called Kwikstop. Both can be expected to improve shutoff response, but do not address boom end contamination.
Wet boom. Are your wet booms made of plastic? If so, they can warp over time and are also harder to clean. Replacement wet booms are available from several suppliers, including Hypro and Wilger. These are made of thin-walled stainless steel for excellent durability and ease of cleaning. Wilger units are very thin and light and come with their own Quick-Nut fittings and feature swept elbows and Ts. Hypro’s Express Booms come with nozzle bodies and Express Nozzle Body End Caps. Flange fittings are used in the Hypro upgrade.
New boom. Some people are recognizing the value of boom width in sprayer productivity and are considering a wholesale boom replacement from a third party. These booms come in wider sizes, lighter materials such as aluminum or even carbon fibre, and innovative plumbing options such as recirculating designs or telescoping for adjustable widths from 80’ to 150’. Perhaps a better suspension system or automatic boom levelling system is part of such a purchase.
Individual nozzle shutoff. Most sprayers have sectional control of at least 5 sections. But some of the outer wings (the part of the boom that is most often involved in sectional control) can still contain significant lengths tied to a section, creating waste. With individual shutoff valves, a boom can be converted to either many smaller sections or even nozzle-by-nozzle sections, depending on the capabilities of the rate controller. Not only do these offer excellent resolution, they also feature instant shutoff and turn-on response at the spray pressure. Because this type of installation can demonstrate product savings, it has a calculable ROI.
Rate controller. Some older sprayers struggle with responsiveness. An operator changes speed, and has to wait a long time for the rate controller to catch up. A newer controller can improve the responsiveness significantly, offer a new larger cab screen, work better with a navigation system, or even include ISO-BUS capabilities for future upgrades. Improving the user experience with a better interface can be valuable, giving an old sprayer a new capabilities and feel.
Variable rate technology. We are seeing several options that can offer better control over nozzle flow rate to suit either a greater range of travel speeds (on hilly or otherwise uneven land) or a better range of rates for prescription map application. Pulse-Width Modulation systems from Capstan (Sharpshooter) and Case (AIM Command), Raven (Hawkeye), or TeeJet (DynaJet) all offer these types of features. A new nozzle body, Hypro Duo React, achieves similar results with multiple nozzles that can switch back and forth according to flow rate needs.
Boom lights. Whether spraying at night or wishing to see spray patterns better in the day, boom lights can help. Versions are available from ATI or SprayTest. Caution is advised when spraying between evening and morning hours, as temperature inversions are common during that time.
3″ plumbing. One of the biggest productivity tools is decreasing the time required to load a sprayer. Wide booms applying large water volumes at fast travel speeds can empty even a large tank in 30 minutes or less. If the fill also takes 30 minutes, then 50% of the spray day is spent idle just for filling. Increasing the fill speed with a new load system using 3” plumbing and a high capacity pump can reduce that to 10 minutes, adding acres per hour. Make sure, though that dry products are properly hydrated so they mix well and stay out of screens. Also consider the rate of chemical induction, as that can be a bottleneck.
Tank wash down nozzles. These nozzles, installed at the top of the tank, direct a clean water source (containing a cleaning adjuvant if needed) to the tank wall, rinsing the pesticide off. Successive batches of cleaning improve the tank wall decontamination as the solution becomes more dilute. By making the wash down easier, tank cleaning can occur in the field immediately after spraying and the rinsate can be sprayed out in the field. This saves time and prevents point-source contamination.
Self-cleaning line strainers. Consider this a productivity tool. Mounted on the pressure-side of the pump, these strainers use excess pump capacity to bypass particles back to the tank. A tapered design creates a rapid flow of liquid past the screen face generating continuous wash-down of particles. Regular inspection is still recommended, but the chance of a problem is significantly reduced. Because debris is returned to the tank, proper tank sump cleaning becomes more important.
Pump. Some call it the heart of the sprayer. The pump pressurizes the spray mixture so it can be distributed evenly and atomized. To do this, it needs to produce high enough flow for our ever increasing water volumes, travel speeds, and boom widths, while maintaining enough reserve for agitation. Some use the system pump to draw water into the tank, which can present a bottleneck. Clearly, capacity and pressure are important. Pump impellers can wear and seals can leak, reducing performance. New or re-built pumps are available in long-lasting stainless steel, and the best new models have flange fittings and seals with either enhanced dry-run survivability, or dry-run capability. An upgrade definitely worth considering.
Clean water tank with dedicated clean water pump. This is another productivity tool. Cleaning the tank in the field without stopping the sprayer becomes an option with this design. Rather than use the product pump to draw clean water into the tank, mix it up, spray it out, and repeat, this design allows continuous cleaning. When the product tank is empty (signalled by a loss of pressure), the clean water pump turns on and delivers clean water through the wash-down nozzles. The pump must have enough capacity to obtain a good cleaning spray from the wash-down nozzles. As the sump fills again, the product pump delivers it to the boom and also cleans the return lines. The end result is prompt cleaning of the tank and thorough, efficient dilution of the remainder.
Boom remote control. Whether it’s for cleaning out boom ends or simply verifying proper nozzle operation, a remote boom section shutoff makes those jobs easier, safer, and more environmentally friendly. Boom remote controls let you turn on just the boom section you need to inspect. It’s also useful for nozzle calibration.
Tires. Ask yourself: what equipment do I spend more time in than any other, makes more passes over each field than any other, makes deeper ruts than any other, and gets stuck more often than any other? A new set of tires, or even tracks, might be worth considering. Low-pressure sprayer-specific tires with VF (Very High Flexion) technology are available from major suppliers. These offer sprayer-specific lug designs, they increase the footprint for increased floatation and less compaction, and they can also improve ride quality. Tracks, though considerably more expensive, are becoming available for sprayers and can make sense in some situations.
Some of these retrofits can be costly. But they can introduce new life and utility into an aging chassis, resulting in higher productivity, higher quality work, or simply a better operator experience. All of these are important and are worth investing in.
Here’s a Real Agriculture video of Tom and Jason talking sprayer retrofits at the end of Edmonton’s 2016 FarmTech.
Note the snazzy “Sprayers101” team shirts!
February 21, 2016
Exploding Sprayer Myths (ep.5): Early Morning Spraying
Should you really get up before the birds to spray? There are a lot of good reasons for early morning and night spraying, but if you’re in a strong inversion, you might be in a world of hurt. Here’s episode 5 in our series of short, educational and irreverent videos made with Real Agriculture.
February 8, 2016
What’s my Spray Quality, in 3 Simple Steps
The introduction of dicamba and 2,4-D tolerance traits in corn and soybeans was accompanied by an unprecedented emphasis on spray drift management by the registrants. Product label statements for 2,4-D choline and the new formulations of dicamba emphasize spray drift control to a greater degree than previous products.
In Canada, labels make prominent reference to the appropriate “spray quality”, a term referring to an internationally standardized droplet size classification (ASABE S572.2). In this standard, the droplet size spectrum produced by a nozzle is communicated using terms such as “Medium”, “Coarse”, “Very Coarse” etc., and used to describe the potential for spray coverage and spray drift. Spray qualities are colour coded for easy recognition.
An example of this label language is shown for Enlist Duo below:
“Droplet Size: Apply as a coarse to extremely coarse spray (ASABE S572 Standard). Use drift reducing nozzle tips in accordance with manufacturer directions that produce a droplet classification of coarse to extremely coarse to significantly reduce the potential for drift.”
Although spray qualities are voluntarily measured and published by most nozzle manufacturers, their appearance on the label makes their use a legal requirement. This is because the Pest Management Regulatory Agency (PMRA) conducts a risk assessment which assumes, in this case, that a Coarse spray quality supports certain calculated buffer zones (15 m in this case) to protect sensitive ecosystems from Enlist Duo damage.
The use of coarser sprays can be used to reduce this buffer zone somewhat, in accordance with an on-line “Site-Specific Buffer Zone Calculator” published by the PMRA.
The challenge for applicators will be to determine the spray quality of their current application method. Here’s a relatively simple three-step process to find out.
Step 1: Identify the nozzles currently on the sprayer.
It seems basic, but it’s surprising how many applicators can not name their spray nozzle. If unsure, closely inspect the nozzle, looking for the manufacturer’s name, the nozzle model, and its flow rate. Most nozzles will have this information printed right on them. Here are pictures of the most common nozzles. Can’t find the info? Have a look at this article for websites with pictures.
Major manufacturers include Hypro (John Deere via private label), Agrotop (marketed by Greenleaf in North America), Hardi, Lechler, TeeJet, Wilger, and Billericay Farm Systems (Air Bubble Jet). Manufacturers produce many models, but most are easily identified by a series of letters and numbers. For example, all nozzles will be offered in several fan angles (80º and 110º are most common), and flow rates (in US gpm).
To be more helpful, flow rates are colour coded according to an international standard. This table shows the colours and lists flow in US units in (gpm at 40 psi) and metric (L/min at 3 bar).
The combination of series of letters or numbers shown on nozzles follows a relatively consistent pattern: Fan angle and flow rate arranged as 11003 or 03-110. In this case, the nozzle produces a 110 degree fan and has a flow rate of 0.3 US gpm. The use of US gpm at 40 psi to designate flow rate is an international standard.
The nozzle model is frequently inserted into this stamp, and is manufacturer specific. For example, TeeJet may include “AIXR” in its stamp, and Agrotop may include “TDXL”. Hardi’s MiniDrift is abbreviated MD. Some nozzles may not list their fan angle. Others (Air Bubble Jet) are blank, creating a mystic aura of superiority. Others leave the information printed on the nozzle cap.
A bit of experience is very helpful, especially with John Deere nozzles, where the nomenclature inexplicably eliminates the first digit of the 110 or 120 degree fan angle. So the JD 11004 is labelled “1004”. That’s a bit like saying “my truck sas a 50 engine”, when you mean it has a 350. How’s a city person supposed to know you don’t mean the trusty old 250 straight 6?
Step 2: Obtain spray quality information on the nozzle.
Most manufacturers publish the recommended pressure range and the spray quality of their nozzles. This information can be found in their product catalogues, or on their websites, or in smartphone apps.
Although the designation of Spray Quality is governed by an international standard that is designed to standardize droplet sizing among various labs, we do see some variation in results. Part of this is due to the continued evolution of the standard, requiring manufacturers to re-do some tests, or at least re-analyze their data. For example, ASABE S572.3 was released in conjunction with ISO25358 which changed the boundaries for the coarser sprays. These changes are beginning to be seen in the newer catalogues.
Another problem is that testing is done with plain water. It is well known that the use of certain formulations or adjuvants can affect spray quality. Currently, the standard does not address these effects, and data should be used with some caution.
Step 3: Identify the expected pressure for a given travel speed and water volume.
The same catalogues or websites that publish spray quality also produce charts that list the expected spray pressures at various travel speeds and water volumes.
Becoming familiar with using these charts enables the applicator to predict the spray pressure the nozzle will be operating at. For example, if an applicator intends to apply 10 gpa using a yellow (02) nozzle, this table shows the following: The nozzle will be operating at 30 psi at 5 mph, at 40 psi at 6 mph, at 60 psi at 7 mph, at 70 psi at 8 mph, and at 90 psi at 9 mph. The applicator should know the nozzle’s spray quality at each of those pressures.
Nozzle sizing follows a slightly different procedure for Pulse-Width-Modulation (PWM) systems, requiring the nozzle to be over-sized about 30% or so. Since the majority of new sprayer sales now include PWM, we’ve prepared a special article just for this system here.
Travel speed and/or spray volume should be adjusted to ensure the sprayer operates at a pressure which creates the desired spray quality. In other words, the pressure gauge should be used as a speedometer. If the nozzle model or size doesn’t produce the desired results, the applicator should consider changing nozzles. Once the right combination of factors has been determined, the spray pressures that created the label-required spray quality should be noted. From that point, the applicator can choose travel speeds that maintain the necessary pressure range.
Summary
It is up to applicators and industry representatives to ensure that herbicide products are applied according to label requirements. We expect significant scrutiny on spray drift from new products and need to ensure that proper application methods are used at all times. It’s important that everyone understands just how to do it.
Dr. Scott Bretthauer (U. Illinois) gives a nice summary in this video by Precision Labs:
December 4, 2015