Spray drift continues to be a concern for the ag industry, and the manufacturers of nozzles and tips have been working to mitigate the issue for growers.
“Spray drift should always be of concern for applicators,” says Nick Fleitz, Agronomist with Pentair Hypro. “Certainly, following the litigation surrounding dicamba in 2020, there will be a lot of eyes on the prevalence of drift incidents in the 2021 spraying season.”
The push to dicamba was accelerated by growing resistance to another herbicide.
“With weed resistance to glyphosate-based herbicides, growers and applicators have had to turn to more specific crop-based herbicides,” says Gary Esselink, Precision Ag Specialist, Raven Industries.
While the dicamba lawsuits brought the issue to the forefront, Fleitz explains, this is not a new issue.
“The past few seasons of off-target issues with dicamba applications have highlighted an issue that has been present but not highly visible,” he says. “Off-target drift has been occurring since we began spraying crops, however, the highly sensitive nature of many broadleaf species to dicamba has highlighted some of our shortcomings whereas, most other chemistries we apply do not carry that high level of sensitivity across so many species.”
While the issue is well understood, not every nozzle, particularly older offerings, was designed to combat drift.
“Quite frankly for general spraying outside of the dicamba system, there are an awful lot of nozzles in use today that open the door to high levels of drift potential,” Fleitz says. “These nozzles can produce upwards of 30% to 40% of their droplets under 150 microns, which are considered highly susceptible to evaporation and off-target drift. Trying to shift out of these older nozzles into newer technology would pay dividends for all parties involved in the crop production industry.”
“In many ways, the spray nozzle is the most important part of the sprayer and is one of the major means to reduce driftable fines in real world conditions,” says Lucas Olenick, Marketing Manager, Wilger. “A perfectly picked spray tip is equivalent to having the right sized screwdriver. Sure enough, having a screwdriver that is ‘close enough’ to the right size will often do the job, but you might end up with serious implications like stripping a screw head with a tool that is too large or too small for the job.
The same occurs with spray nozzles when it comes to spray coverage and drift reduction.”
When it comes to spray drift, droplet size matters.
“Designs have been dictated by the droplet size requirements for the auxin formulations, to some extent,” explains Will Smart, Owner, Greenleaf. “XtendiMax and Engenia need an ultra-coarse droplet with less than 1% driftable fines (141 micron or smaller).”
There are a number of factors beyond droplet size that affect drift potential.
“Some nozzle designs are incorporating different spray angles to help with backside coverage of the target weeds, and some have asymmetric dual fan patterns to allow for multiple spray patterns directed at the target,” Smart says.
“One must also remember to first and foremost, follow all label recommendations for pressure and tip size for the desired herbicide application,” Raven’s Esselink says. Esselink lists other factors that could affect spray drift would be exceeding recommendations all found on the herbicide label:
- Too high of system or sprayer pressure.
- Wind speed.
- Time of day.
With older nozzles, changes in pressure meant changes in droplet size. New designs deal with that issue.
“Consistent droplet sizing across pressure ranges is the biggest breakthrough in these nozzles,” Pentair Hypro’s Fleitz says. “Traditionally spray nozzles may produce a wide range of spray droplet sizes and drift potential across their pressure range. As pressure increased so would drift potential as droplet size reduced.”
The latest technology has helped limit the potential for drift.
“Air induction nozzles have been the go-to technology for maximizing drift control for many years,” Smart says. “However, with the increased adoption of PWM (pulse width modulation) sprayers, nozzle manufacturers have had to come up with drift reducing nozzles that do not use the air induction/venturi technology, as it is not compatible with the rapid cycling of the solenoids in PWM systems.”
PWM systems do come with a learning curve, which for Wilger meant a busy pre-season of training.
“While the flexibility of the spray systems are great, the selection of nozzle to really determine the ‘sweet spot’ between spray drift and maintaining functional applications is even more important,” Wilger’s Olenick says. “As adoption rate of newer technology grows, there is a concern that there are applicators are ‘missed’ in teaching them how to change their spray tip selection to PWM spray systems. With these missed opportunities for training, there is serious risk for applicators to not get the required training to properly mitigate drift before they get into the field spraying season.”
“Most manufacturers have worked to provide inputs for consistent application and to allow them to make more informed decisions,” Esselink says.
Knowing what’s being applied and its purpose are part of the process for deciding which nozzle is the best.
“One of the first considerations should be the type of chemistry being applied,” Fleitz says. “When applying systemic herbicides, we have the ability to utilize coarser droplets and focus more on drift control. When applying contact chemistry, the focus should shift towards a more balanced approach of coverage and drift reduction together.”
There are certainly other factors to consider.
“First, they must consider the chemical label, it often dictates the spray quality or droplet size required,” Greenleaf’s Smart says. “It may even require a specific nozzle at a specific pressure range, as with the newer auxin products. Next, the applicator must take into account the field conditions and of course his speed, carrier rate, etc. Applicators should target the appropriate droplet size to the application, and not assume that any nozzle that will deliver the right rate is okay for the job.”
Pentair Hypro’s Fleitz agrees.
“Outside of droplet size and drift reduction, there are certain types of chemistry that have characteristics like viscosity that can influence how they interact with spray nozzles. For example, atrazine is notoriously viscous and can build up in plumbing and nozzle screens. When recommending nozzles for use with atrazine, I generally recommend a simpler nozzle design that provides fewer points of plugging that I might with other chemistry that has lower viscosity.”
There is one other factor growers should consider, Fleitz says.
“It is also important to consider the area surrounding your fields and of there are susceptible crops or other vegetation growing that needs enhanced protection from off-target drift,” he says. “Applicators must also consider the type of sprayer being used, is it a conventional sprayer or is it equipped with PWM. Not all spray nozzles are compatible with a PWM system.”
“The nozzles do their part, but the operator must also pay attention to wind speed and boom height, as well as sprayer speed,” Smart says. “The big challenge is controlling drift without sacrificing coverage, which can lead to reduced efficacy and, ultimately, resistance.”
Simply put, not all nozzles are the same.
“Using the correct spray tip also affects the accuracy of product applied by matching it to be within the range of the recommended rate,” Raven’s Esselink says.
In other words, not all products are distributed equally, or should be.
“The right nozzle selection can improve the performance of your sprayer and the chemistry it is applying,” Fleitz says. “I would encourage applicators to look into newer nozzle technology that is shown to provide some level of drift reduction while simultaneously improving coverage. This will make sure you achieve the pest control you’re after, while also stewarding the chemistry that is available to us.”
Even with the most advanced technology, there are some basics that growers really shouldn’t ignore.
“I will also say it is important to check the condition of your spray nozzles,” Fleitz says. “They do not last forever, in fact in 2020 we conducted field wear studies with the participation of farmers that showed in general nozzles last in the range of 30,000 to 40,000 acres before needing replaced. If you’re using worn or damaged spray nozzles, they will hinder the performance of your sprayer.”
“Consistency in application is essential for a correct and required type of application,” Esselink says. Among those inputs would are:
- PWM nozzle control. Controls the flow at the nozzle and allows for a constant system pressure.
- Automatic boom height control. The spray boom is kept at the desired and required height for the nozzles.
- Weather monitoring systems. Systems on the sprayer itself to monitor temperature, wind speed and other weather conditions.
Esselink offers one last thought: “Recordkeeping is a very important factor to ensure the product was applied in the correct conditions to avoid unwanted spray drift.”
While the nozzles can help reduce spray drift, diligent applicators much consider a number of other factors.
“An applicator’s due diligence is to use all the tools in the toolbox to reduce driftable fines,” Olenick says. “Such tools in the ‘spray drift reduction toolbox’ may vary a fair bit, but each of them stems on the applicators need to aim for more consistent application BEFORE a spray application is made. For many situations or applications, there aren’t very many second chances. Some of these tools that add up to a more consistent spray might be:
- Bolt-On drift reduction tools.
- Drift Reduction Nozzles — with means to reduce driftable fines from 50% to 95% of a conventional spray nozzle.
- Drift Retardants or Adjuvants — as long as there is no antagonism of the chemical mix, upwards of 30% to 40% drift reduction might be observed.
- Weather Station or on-machine wind & inversion monitoring — While the percentage drift reduction might vary, monitoring and adapting to weather and inversions situations are critical to planning for an ideal spray day or adapting to a non-ideal spray day.
The Latest Offerings
Raven: The Raven Hawkeye and Hawkeye 2 Nozzle Control Systems are able to control the flow at each individual nozzle. The NCV (Nozzle Control Valve) is a Post Width Modulated Valve that allows rate control at the point of application through the spray tip while still maintaining a constant pressure throughout the spray system. This means that whether the operator slows down or speeds up, the pressure remains the same and a consistent spray pattern is maintained. A consistent spray pattern is probably the most important aspect of a spray application. The Hawkeye systems also provide features like Turn Compensation, Individual Nozzle Shut-off and Individual Valve Diagnostics to monitor each spray tip.
Greenleaf: Air inducted Dual Fan nozzles have been proven to help with coverage while reducing drift. For conventional spray systems, our TurboDrop Asymmetric DualFan has been a top choice for coverage critical applications for 10 years. Our new Blended Pulse DualFan (BPDF) has worked well with PWM spray systems for the last two seasons. We have two new sizes in the BPDF range. Our TADF-D version can produce a very drift resistant spray with Ultra Coarse droplets while still providing multiple angles of coverage.
Pentair Hypro: Ultra Lo Drift Max (ULDM) spray nozzles were designed with dicamba and 2,4-D applications. The ULDM nozzles can provide up to 95% drift reduction, making them one of the most effective drift reducing technologies available. PWM compatibility allows for the ULDM nozzle to be paired with the latest in individual nozzle control systems.
Wilger: Wilger’s narrow-angle ER and DX series will definitely be something that any spot-spraying applicator would want to know about. The narrow angle spray tip options in the market have seriously been lacking compared to typical 80° to 120° spray tips, so the DX series will be a very welcome addition to the market offering new spot spraying and specialty crop applications. To start, the DX series is available commercially with the -04 to -125 nozzle sizes, but if there are applicators outside of those sizes, they are encouraged to contact either Wilger factory to check availability on a small-batch level.