Take home messages

• Self-propelled sprayers have fully replaced pull type sprayers in western Canada
• Self-propelled sprayers have challenges – tyre size, boom stability and height at typical speed of operation have reduced deposit uniformity and increased drift
• Spot sprayers have not been adopted in Canada to the extent they have in Australia for a number of reasons but primarily due to the reduced window for green on brown application in the pre-seed system
• Sprayer productivity is greatly enhanced by improvements in logistics and boom width, more so than sprayer speed
• Product registration and legislation is holding back uptake of drone pesticide application, but they are being used nonetheless despite challenging deposit patterns.

Background

The past 20 years have seen historic changes in spray application in both North America and elsewhere.

Self-propelled sprayers

In Canada, first and foremost among those trends has been the wholesale switch from pull-type sprayers to self-propelled units. In fact, the once burgeoning pull type sprayer manufacturing base represented by Flexi-Coil, Brandt, Bourgault, and Ag-Shield has completely disappeared. In its place we are seeing self-propelled sprayers by John Deere (#1 in sales) followed by Case, and some distance back AGCO, New Holland/Miller, Apache and other smaller units. Within this group, sprayers offering 1600 US gallon tank capacity (6000 L) are the best sellers, with the 36 m boom being most common. Notable trends in this sector are wider booms, with 40 m gaining popularity and two manufacturers offering 48 m units.

Figure 1. Self-propelled sprayers have completely displaced pull-types in the Canadian retail market.

Tire size

A problematic side effect of the large self-propelled sprayers is weight, with 18 tonne dry weights not unusual. This has required the use of wider tires, with 800 and 900 mm wide rubber displacing the once common 650 flotation tires. Skinnies have moved from 320 to 380 mm widths, with 54 inch wheels in some cases, to increase floatation. Nonetheless, soil compaction and crop trampling are increasingly problematic with no obvious solutions for those issues.

Figure 2. Larger tires, necessitated by heavier equipment, introduce aerodynamic challenges that affect deposition uniformity.

Travel speeds

Sprayer travel speeds have increased as well but there is increasing realization that faster speeds are not the key to increased productivity. Speeds of 25 km/h are common; we see speeds as slow as 20 km/h but also up to 30 km/h. The use of Pulse Width Modulation (PWM) has contributed to faster speeds as the nozzle sizing used with PWM has a built-in capacity for the extra flow required.

Spray drift

We have not been able to document trends in drift complaints as the majority of these elude the attention of a government or other reporting agency, and issues are typically resolved privately between the affected parties. But our research studies suggest that for a given spray quality (say, ASABE Very Coarse), airborne spray drift has increased about two-fold for a high clearance sprayer travelling at 25 km/h at a 90 cm boom height compared to one travelling at 13 km/h with a 60 cm boom height. The increase in drift is attributed to the combined effects of boom height and travel speed, creating a trailing plume of drift that contains a larger proportion of the applied volume. There seems to be few mitigating actions other than lowering the boom and slowing down. The alternative, to use a coarser spray, while also effective, will challenge coverage, particularly since the use of contact modes of action has become more important in the age of herbicide resistance.

Boom stability

Lagging behind the tractor unit size and speed revolution is boom design. Applicators are finding it necessary to keep booms at 75 to 90 cm above ground to avoid issues due to boom sway. Some are claiming lower heights (say 60 cm), but this would only be possible on predictably flat land. Unacceptable boom sway and yaw remain as one of the inexplicable laggards in sprayer design. Few more important priorities exist, with only marginal improvements in domestic products to show for it.

Figure 3. Boom sway continues to be unacceptable despite high equipment prices.

Deposit patterns

We have focused on studying spray patterns as a possible negative consequence of the larger tractor units coupled with the common sprayer speeds. Our results have been surprising, with coefficients of variation (CV) of the deposit behind a 36 m boom at 25 km/h frequently over 25% and as high as 35%. These results leapfrog the conventional standard for an acceptable spray deposit CV of 15%. The consequence of higher-than-expected CVs are more regions of suboptimal, possibly sub-lethal, deposition that allow weed escapes. Again, a reduction of travel speed, coupled with lower booms and coarser sprays, was found to ameliorate some of this variability. Of note is the observation that the areas of lowest deposition occurred behind the wheels. The study of aerodynamics is necessary to identify designs and operational parameters that limit these deficiencies.

Figure 4. Deposit uniformity has become more of a problem with faster driving speeds and higher booms.

Nozzles

The Canadian (and global) nozzle market is stable and is dominated by air-induced and pre-orifice tips that produce Coarse and Very Coarse spray qualities. Relatively few new products have been introduced since the move to Ultra Coarse sprays required on dicamba/soybean labels since 2017. These nozzles are excessively coarse for general use but may have utility in extreme weather conditions or times of near zero drift tolerance. We are seeing demand for pulse width modulation (PWM) compatible nozzles that is not being adequately met by most manufacturers. This market requires drip-free operation under rapid pulsing cycles as well as high flow rate capability (08, 10, 12, 15 sized nozzles). Twin nozzles have utility for some specialized applications but are not necessary for most early post-emergent herbicide sprays.

Plumbing

Sprayer plumbing complexity, coupled with poor functionality, has resulted in a new era of herbicide residue issues related to the adsorption of oily pesticides to rubber components, notably the inside wall of rubber hoses. The use of stainless steel, particularly in sprayer tanks, has helped reduce the severity of cleanout problems. But the adoption of recirculating booms that avoid waste during air purge or primes was slow to reach Canada and systems are only now becoming available at the factory. Most installations are after-market. Some sprayers are designed to preserve very high-flow capacity requirements that exist outside of Canada, (e.g., high rates of liquid fertilizer topdressing in corn), and this unnecessarily adds complexity and volume on the boom, creating waste and undermining the utility of the recirculating concept.

We have seen fairly enthusiastic adoption of the continuous cleaning concept as a do-it-yourself project on sprayers; this concept dramatically reduces the liquid volume and time requirement of an initial rinsing of the sprayer tank. In the simplest terms, a continuous rinsing system requires the addition of a small pump dedicated to the clean water rinse tank, whose pressure feed goes directly to the wash-down nozzles. This allows the simultaneous operation of the solution pump to the boom, eliminating rinsate as it’s generated. If the remaining liquid can be minimized during this operation, a 600 L rinse is more effective and much faster than three 200 L batch rinses.

Figure 5. Recirculating booms, for long a staple of sprayers in the rest of the world, are only recently catching on in North America.

Productivity

During the initial roll-out of self-propelled sprayers in the late 1990s and early 2000s, tanks were 4000 L, booms were about 30 m and most on-farm refilling plumbing was 2 inches. Coupled with products being in 10 L jugs, filling times could be as high as 30 minutes. Sprayer productivity was addressed primarily by increased sprayer speed.

We have since seen a revolution in tendering, with many farms owning a 30,000 L capacity tendering (bowser) trailer equipped with 3” transfer pump and chemical induction from totes. This has made it possible to very significantly reduce time needed to fill, down to 5 to 10 minutes per 6000 L tank. Owing to 30 to 40% productivity gains (ha/h) from this change alone, sprayer speeds have moderated, and many are now between 20 to 25 km/h, modest by recent standards. This has allowed boom heights to be reduced, and drift issues to be better managed. There has now been a new trend to wider booms, facilitated by the moderation in travel speeds. In other words, paying attention to the logistics of the spray operation has opened opportunities for better quality work done by the sprayer itself.

Figure 6. Improved tendering has been the key change leading to increased sprayer productivity.

Competition

For many years, the north American sprayer market has been dominated by few manufacturers, and even within these, we have seen consolidation. The overall diversity of offering has been stagnant, and prices have risen at twice the rate of inflation without adding as much innovation as should be expected by the price change. Part of the underlying cause is consolidation in dealer ownership, larger dealerships with less brand diversity, and few opportunities for independent dealer establishment owing to diluted overhead costs by large networks. The opportunity to bundle products for a discount, and for large farms to negotiate better deals, has created more brand loyalty within any given farm.

Figure 7. Imported sprayers, such as this Horsch-Leeb, have offered superior designs to domestic units, particularly regarding boom stability.

The entrance of competition from abroad, in the form of Agrifac since 2015, and Horsch-Leeb since 2018, and possibly Amazone in the near future, has been welcome. These sprayers offer not only first-in class size (8000 L tanks and 48 m booms), four-wheel steer and sophisticated wheel suspension, they also have superior plumbing designs (both in simplicity and functionality) and reasonable price points. But most noteworthy has been the boom stability. Coupled with 25 cm spacing, we are seeing applicators running booms significantly lower than the competition, as low as 40 to 50 cm. This has advantages for drift management as well as deposit uniformity.

Spot sprayers

Canada lags significantly behind Australia in the adoption of spot sprayers. In the Green-on-Brown (GoB) segment, opportunities for spot sprayers are primarily in the pre-seed operation, where we typically run a single knock on a glyphosate tank mix platform. Weeds are just emerging after the winter and are not more than the cotyledon to two true leaf stage. As such, the simultaneous broadcast feature is a requirement, at least in the first half of the pre-seed season, limiting savings. Secondly, glyphosate sprays remain inexpensive, again limiting savings. And finally, the systems are priced so that attractive returns on investment (ROI) can only be realized by larger farms.

Desiccation and pre-harvest weed control in pulse crops such as peas and lentils are a large potential use of the GoB systems, as is the application of fungicides based on a fairly high green index threshold setting.

Nonetheless, we see approximately two dozen WEEDit systems running in western Canada. This system remains the performance leader and is meeting with good user satisfaction. Croplands has withdrawn from the Canadian market and Rometron will be taking over the marketing and distribution of the system starting in 2025.

John Deere’s See & Spray Select (whose design originated in Australia) is experiencing fast growth, with many dozens of units operating in 2024 after just a few years of active promotion. The main issues are basic scepticism around the performance claims for small sized weeds, and the existing investment that most applicators have made in PWM systems that cannot be transferred to a spot spray installation. They thus require a new boom and that is a deterrent.

Figure 8. Green-on-Brown systems, such as this Greeneye unit, have largely been limited to row crops in North America.

Another complicating issue is the relatively poor availability of spray nozzles suited to spraying a narrow band, say 25 to 40 cm wide. Most of these nozzles are older style, drift prone. Only Wilger (ComboJet) has committed to a complete line of 20, 40, and 60 degree fan low-drift spot spray tips, the DX series. Others, such as the Agrotop Spot Fan are also available. But specifically produced spot spray nozzles from many of the major manufacturers are absent, and this means compromises in outfitting a sprayer and possibly forfeiting some of the savings afforded by the technology.

Of course, boom sway is an issue with both camera and nozzle systems, both of which have a restricted boom height window for optimal operation. Nonetheless, we have not seen any hints of a manufacturer offering toolbars or other wheeled booms that address these issues.

Green-on-Green (GoG) systems are in their infancy in Canada, with only Agrifac AICPlus (Bilberry/Trimble) having made any inroads in the western market with about one dozen units sold. They offer algorithms in cereals, oilseeds, and pulses, as well as GoB. In eastern Canada, where row crops of corn and soybeans are commonplace, John Deere’s See & Spray Ultimate is selling. This system is not yet available for small grains and is not sold in the west.

Drones

Canada’s Pest Management Regulatory Agency (PMRA) determined that drones represent a significantly new pesticide application method and require a full and new risk assessment prior to labelling. As a result, we have only four pest control products registered by drone, three are biological mosquito larvicides and one is an industrial product for control of woody perennials in rights of way (Garlon™ XRT, triclopyr). Canada does not yet have an agricultural use registered for drones as of February 2025.

Figure 9. Although attractively priced, spray drones are a setback in terms of spray swath width and uniformity.

Nonetheless, spray drones are selling well with an estimated 450 large spray drones being sold in Canada in 2024. Producers are opting to try these drones on their farms owing to their low cost ($37,000 CAD for DJI T50; ~$41,235 AUD), and many are foregoing pilot licensing and drone registration. We are seeing water volumes of about 20 to 30 L/ha, with spray droplet sizes of 250 µm VMD (Fine to Medium) being deployed, primarily for fungicides.

Research results show that drones produce poor spray patterns with very high variability, and also with narrower swath widths than advertised by the manufacturer. In addition, swath widths are inconsistent, being a function of flying height, spray volume and droplet size, wind direction, payload, and flying speed. Recently, we have measured swath widths in a number of different crop canopies and found a 20 to 30% reduction in width when applying into a mature canopy as would be the case for fungicides. As a result, striping is commonplace.

Registering a use for drones is the prerogative of the registrant and we are not seeing as much interest as expected. It is possible that only a few pesticides will see drone registration over the next several years. The PMRA may, after conducting their risk assessments and being relatively certain of the place of drones, consider grandfathering in prior aerial labels for drone use, as the majority of the US states have done.

Conclusion

Spray application remains a very dynamic space. Despite the significant capital investment required for a new spray system, overall, the success of the spray operation has been declining not just due to resistance, but also due to excessive travel speeds, boom heights, and compromises on the ideal weather operating conditions due to excessive workload. Key areas of attention for manufacturers should be boom stability and plumbing simplicity. For applicators, they should be logistics that enable slower operating speeds.

Contact details

Tom Wolf
Agrimetrix Research & Training
Saskatoon, SK
Email: agrimetrix@gmail.com

Date published
February 2025