Michigan’s Great Lakes EXPO is a massive horticultural convention that draws international speakers and more than 4,000 attendees to Grand Rapids every December. Like any large agricultural conference, it can be challenging to run back and forth between lecture rooms to hear key presentations. And, of course, there is always disappointment when you have to choose between two talks in concurrent sessions. When your head is full and your posterior is numb, you move onto the trade show floor.

I think the trade show might be my favourite part; Who doesn’t like filling a bag with swag? Candies, foam vegetables, pens, DVD’s, colourful brochures and all manner of gimmicks designed to get your attention in a sea of vendors that vie for “just a minute of your time”. But for me, I only have eyes for the sprayers. And wow, were there a lot of sprayers at GLEXPO.

This article is a photo journal of those sprayers (or features) that caught my eye. For some readers, these features might be old news, but for me they were insight into a different way of spraying. For example, Europe’s tolerance for spray drift is practically nil, and sprayer manufacturers have had to develop equipment that comply with that reality. Many such sprayers were present, so I had a chance to see, and ask questions, about their claims of less than 5% drift. At the other end of the spectrum, there were sprayers that proudly boasted being able to cover multiple rows in a single pass by boiling the spray over great distances… which while appealing to producers looking to save time, still makes me wince. But then, I’ve never tried to spray almonds in California, or citrus in Florida. Then there were sprayers claiming to cover multitple rows and reduce drift, which would be quite a trick. I reserve the right to be a skeptic.

So, I’m not promoting or condoning any of the equipment or claims described here. I’m just sharing what I found interesting and I’m giving the reader a peek onto a trade show floor they might not otherwise have seen.

Shrouded Herbicide Application

There are lots of approaches to making in-row or under-row herbicide applications. The concept is simple enough: You want to get the product on the ground either under or between rows without hitting the crop itself. If you don’t care about hitting a mature orchard trunk, the boomless nozzle is a good choice with it’s massive droplets and variable swath. But if you want to avoid off-target movement as much as possible, you need shrouds.

I’ve seen brushes used to great effect in asparagus because they match the contour of moderately uneven ground by dragging over it. Gaps may open in the shroud as the bristles part, but that issue may be offset by the possible advantage of physical redistribution of herbicide as it rubs over the target weeds like a weed-wicker.

Then there’s the classic flexible curtain. Similar to the brushes, it’s intended to “just” touch the ground and should maintain a reasonable seal even if said ground is moderately uneven. I often wonder how difficult it is to clean all the surfaces on these systems, but since they are only ever used with herbicide, I won’t speculate how often operators actually decontaminate (or even rinse) them.

Other variations include a hard carapace with no contouring lip. They should only be used with Coarse spray qualities or larger. Note the hefty spring on the boom for those inattentive moments where the operator might whack a trunk or fence post. The wing flexes away from the impact and snaps back into position, giving the operator time to put  down the cell phone and tweak the steering wheel. The adjustable nozzle body on the far end is a nice feature for adjusting the swath without changing nozzle spacing, but beware to maintain proper overlap.

And, if you want the heartiness of a solid carapace, wouldn’t it be nice to be able to see through it so you can spot a plugged nozzle before it becomes a problem? This variation with its heavy impact bar, tight nozzle spacing (to reduce the potential for misses) and guide wheel (to maintain correct boom height) looks ready to handle anything.

Airblast – Multi-Row, Ducted Systems

In the never-ending quest to do more in less time, multi-row airblast systems are very appealing. Delivering air to the vertical booms in each row can be challenging. I’ve seen suspended axial fans (e.g. Gregoire, not pictured) but they’ve always struck me as overkill because of the volume and speed of the air they deliver, and because they need fairly wide rows to be accommodated. Their weight is also a concern, requiring scaffolding that must be strong and still somewhat flexible to handle the inevitable pitch and yaw translated from uneven ground to the boom.

Lightweight conduits that channel air through ducts (like the Berthoud sprayer below) are a popular solution. They can be suspended to any length and telescope to any row width. Head pressure, and friction from sharp bends in the ducts can influence the air delivered, so the shorter the ducts and the less bends, the better. It was a surprise to discover the ducts in this sprayer are corrugated inside as well as out, but apparently it’s not enough to disrupt air flow significantly.

This Berthoud sprayer offers many of the optional features I’ve seen on the Hol sprayer (not pictured) such as tandem axles, a hand wash tank, low residual volume tank, and built-in boom and tank rinse systems. What’s interesting is the light weight “Drop Legs” (i.e. the vertical booms) with dual-angled “airmist diffusers” (i.e. the air shear nozzles) for multi-row vineyard applications. The close-up below uses my hand for reference. There are options for two to four diffusers on each drop leg, and they can be single or double sided, giving a lot of flexibility to match the crop.

How do you control flow? With a digital flow regulator. What if you want a different rate at each diffuser? Well, if I understand this correctly, instead of using a typical flow-metering disk placed in-line to restrict flow, you slot a conventional moulded hollowcone inline and use the nozzle manufacturer’s flow tables. And what if you are concerned about using a misting air-shear style nozzle? It appears they also offer an option to swap out the diffusers for air assisted swirl nozzles where the air flow is behind the nozzle to entrain the spray and limit dispersion. They look similar to the diffusers, except they have a nozzle cap between the slotted air outlets (not pictured).

Ducted air handling comes in many shapes and sizes. Rather than terminating in a blade-shaped diffuser, Cima has hourglass shaped distribution heads that use the venturi principle to deliver airspeeds up to 180 mph at the nozzle. That’s fast, and while it would help entrain spray as it travels longer distances, I wonder what it does to crops close-up?

In the centre of each head is the teardrop-shaped atomizer-style nozzle that produces a Very Fine spray quality between 100 and 150 µm in diameter. It was explained that the teardrop employs Bernoulli’s principle… and for the lay reader (like me), think of the teardrop the way you think of an airplane wing. Air moves over the contour at different rates, making a low pressure area at the tip. The upshot is that it creates lots of very small droplets that (according to the manufacturer) permit you to use much lower volumes that you would with an airblast sprayer using conventional hydraulic nozzles. As always, I suggest you let coverage be your guide to spray volume.

Flow is controlled by an inline disc that allow the user to select from a series of flow-restricting orifices. Look back two photos and you’ll see them as yellow circles on the tower. The photo below is a stainless steel version from an AgTec.

Air-Assist Horizontal Booms

A ducted, vertical airblast sprayer is an air-assisted horizontal boom sprayer just waiting to happen. For vegetable and berry growers, air assisted spraying is an appealing prospect. Many still use axial airblast or cannon sprayers to spray row crops, but I don’t like that. It’s my opinion that while it may be effective, it’s not efficient because it’s not possible to consistently control drift or coverage. I prefer getting the air and nozzle closer to the crop, but sprayers that can do this are few and far between.

There have been no after-market options I’m aware of for converting a horizontal boom to an air-assisted boom. That leaves only a few manufacturers of trailed boom sprayers to fill the need (e.g. the trailed Hardi Commander with Twinforce air or their new self-propelled Alpha evo). But this tradeshow opened other possibilities, as demonstrated by the Cima below. It uses all the same principles described above… it just aims down.

Not interested in ducted air delivery on a three-point hitch system from France or Italy? No problem. How about a Florida company called Airtec that offers trailed air-assist booms up to 120 ft. I wasn’t able to photograph the sprayer at the show, so here’s a picture of one in the field (from their website), as well as several I took at a spinach operation in Ontario.

Airtec offers a single axle, or a walking beam tandem axle reminiscent of the Argifac Condor. Note that the boom itself is the air conduit, which should open crop canopies, expose underleaf surfaces, entrain smaller droplets to reduce drift, and extend the spray window by allowing the operator to work in slightly windier conditions. I can’t speak to the manufacturer’s claims of reducing spray volumes (and by extension, chemicals), but you can read it on their glossy brochure.

Each air outlet terminates in an hourglass-shaped duct, similar to the Cima and ostensibly creating the same advantage, as they also claim 180 mph windspeed at the nozzle. Again, I wonder if that can be dialed back, or adjusted to match the density of the crop canopy? Unlike the Cima teardrop shear nozzle, conventional hollowcone nozzles are used (see below). They can also be suspended to match the contour of the row (look back at the first photo) improving coverage in a manner similar to using drop arms or row kits.

Airblast – Unconventional Fans

Let’s get back to airblast sprayers. The majority do not use ducts to convey air to the target – they point and blow. Pictured below is the generous Mark Ledebuhr with a Proptec rotary atomizer. I call him generous because for several hours Mark led me through the tradeshow and introduced me to many of the vendors. Perhaps more importantly, he helped me interpret what they were explaining after we left each display. Developed with his father, the Proptec system suspends individual fans with rotary atomizers so each can be aimed and operated independently, offering a lot of targeting flexibility. The fans can be electrically or hydraulically driven. Some might be reminded of a Sardi fan (not pictured) but unlike that system which uses several conventional nozzles around the circumference of the fan, Proptec employs a rotary atomizer in the centre. Rotary atomizers can produce very, very small droplets and until GLEXPO I was only familiar with their use in aerial applications.

I admit to a bias when it comes to airblast sprayers. In my mind, the further away the source of air and spray are from the target, the more opportunity there is to drift. Particularly when such small droplets are involved. I couldn’t find the Proptec video I saw looping at the tradeshow, but what I saw looked like tight columns of cycling spray, reminiscent of a tornado, firing into each row of a vineyard. I was told it was during a 15 mph wind, yet I didn’t see a lot of off target movement. A notable advantage to spraying down into the ground rather than sideways or up into the air. Here’s a good video I found of one operating in highbush blueberry (below). It seems I have a lot more to learn about this system.

Then Mark and I went over to see Michigan-based Precise Manufacturing’s EX III cross-flow rotary atomizing tower system. I was reminded of the Curtec tangential fan towers that, like this sprayer, employ rotary atomizers and a peristaltic pump. For Curtec, it’s the AccuStaltic pump. For Precise, it’s the Extreme pump. More on that shortly.

Here’s a video of the EX III operating (sourced from the Precise Mfg. website). Obviously, we’re not talking grapes, berries or high-density orchards, here. This is for big, dense targets like standard cherry, nut trees and citrus. The rotary atomizers throw spray in a circle, but the air from the tangential fans capture it and blow it all out towards the target in very laminar (i.e. not turbulent) air that carries it over long distances to the target.

Back to the peristaltic pump. It can run dry, is self-priming, is anti-backflow, low maintenance and can handle pretty much any manner of spray mix (i.e. viscosity and corrosion are non-issues). Each atomizer has its own flow channel, and by changing the diameter of each tube you change the relative flow rate to each atomizer. Certainly not something you’d do every  day, but it does allow you to match flow to the canopy density.

The Precise Touch Screen Controller is very intuitive and I liked how much control the operator has. Fan speed can be adjusted quite easily (although it would require a very knowledgeable operator to ensure the correct speed is selected). It tracks GPS position and logs where the sprayer empties and the rates used per acre. It also calculates a kind of tree-row volume by determining savings when the operator turns off nozzles that would otherwise blow over the tops of targets, or when overall flow is reduced by slowing the rpms of the pump.

Airblast – Cannons

Well, there were lots of cannon sprayers. Most airblast manufacturers have one in their lineup. Squirrel-cage style fans feed air into a tower that allows spray to come out laterally, and on a downward angle from the top of the sprayer. AgTec, pictured below, has long sold such a sprayer.

The nozzles are air-shear style, relying on fast-moving air to shear the spray into finer droplets.

They usually only have nozzles on one side and the cannon can be turned via a chain-driven gear, and aimed up or down from the cab. They are intended to spray larger areas to save the grower traveling every row, and to prevent physical damage to the crop as the sprayer passes (I’m thinking about knocking berries off, mostly).

Nurseries use cannon sprayers quite often because they spray whips (i.e. young trees), shrubs, container crops, and all manner of crops in dense plantings and they try to spray them all with a single sprayer. Generally, there’s a lot of drift potential and erratic coverage from cannon sprayers – especially when operators try to cover too much ground in a single pass. I’m always skeptical when I can’t adjust air settings without impacting spray quality, and considering the bad practice of trying to apply too wide a swath, I have a hard time with cannon sprayers. I will note that the AgTec now has baffles that allow the operator to distribute air over the height of the tower (see the hand near the hydraulic piston in the image below). However, I don’t know what that does to spray quality in each section of the tower.

Airblast – Classic Axial Fans

And, of course, there were many classic axial airblast sprayers. Even then, however, there were features to set them apart from one another. British Columbia’s Slimline TurboMist was there, featuring their turbine fans and adjustable air outlets (not pictured). Italy’s Carrarospray was there, and I’ve written about them in the past because they make a tiny sprayer that I like in cane fruit and highbush blueberry. You can hitch it to a mower and mow while you blow.

More interesting to me was their sprayer boasting two axial fans that run counter to one another. Carrarospray claims this counter-rotation creates more uniform air than a single fan… but I have no idea how.

Then there was the Andreoli Eco with it’s stainless steel high-efficiency vane system. Reminding me of the Turbomist, the suction is in the front, so the sprayer is a little less likely to draw spray into the fan when one side is shut down for border spraying and when turning at the end of a row. Louvers covering the outlets would be better, but still, this is an improvement. They also claim to have a symmetrical airflow pattern, unlike older axial fans that move air up on one side and down on the other.

The Rears Pul-Tank reminded me of just that – a tank! Heavy-duty, stainless construction and intended (with care) to last a long, long time. No special features to boast of. It would seem this sprayer adheres to old-school ideas about airblast spraying. Certainly, simple and strong are two appealing features to those operators that don’t want to be bothered with complications.

And, lastly (not leastly), was the Air-O-Fan sprayer. Another solidly-built sprayer with a few interesting features. Not shown is the reverse-style propeller which like the Andreoli Eco, claims to draw from clean air, and not spray-laden air. This is undoubtedly the biggest trash guard I’ve ever seen to protect the fan blades from drawing in dirt and leaves (see below). Looks like a CAT steam shovel.

Something that struck me was the air deflector blades inside the fan housing. In my experience, the nozzle bodies and blades are two separate components. But not here, and it makes so much sense! I’ve always taught operators to adjust the air speed/volume and direction first, then adjust nozzle direction and rates second. With this system, you aim the nozzles right along with the air. Expanded systems (e.g. for tree nut, citrus) can have as many as three nozzles per deflector blade.

There was one other very exciting feature coming to this sprayer that I promised I wouldn’t reveal until they were ready, but I’ll just write “HVES” so you will remember you heard it here, first!

Closing

So, this was a massive, sprawling article. Congratulations for getting to the end and I hope it opens your mind to the possibilities for horticultural spray application. The GLEXPO tradeshow was a great experience and I’ll try to get back there in the future. Until then, I look forward to bringing some of this equipment to Ontario to try it out in our horticulture operations. There’s always more to learn.