Picking the proper spray tip requires walking a fine line between good coverage and drift control.
Unfortunately, the nozzle with perfect coverage — a small fine droplet — is also likely to be at greater risk for drift, while a nozzle that eliminates drift with a large droplet size is likely to produce less-than-ideal coverage.
But there is a happy medium to be found for savvy applicators.
“If we select the right nozzle tip and operate it correctly with appropriate boom pressure, boom height and nozzle direction, we can manage spray drift and still get the efficacy we need,” says Bob Klein, University of Nebraska extension cropping systems specialist.
Controlling drift is a no-brainer for no-tillers neighboring sensitive crops, but Klein says everybody benefits from minimizing drift as much as possible.
“If we have 8% drift, that’s like throwing away 8% of your spray investment,” he says.
An application that runs $10 per acre would result in an 80-cent-per-acre loss, or $240 over a 300-acre field in lost material alone. That’s not including decreased efficacy or the cost of off-target damage.
To avoid those losses and get the most out of a chemical investment, no-tillers need to carefully select nozzle tips and manage their spray operations. That may mean using more than one set of nozzles to get through a year of applications.
Here’s a quick look at the types of nozzle tips from which no-tillers can choose, along with their strengths.
Turbo TeeJet. This newer nozzle designed for drift reduction features two orifices, one for measurement and one to determine spray pattern.
“The two orifices give larger spray droplets,” Klein explains. “The nozzles can be used from 15 to 90 pounds per square inch (psi) and you can achieve a lot of different droplet sizes with pressure changes.”
A Turbo TeeJet at lower pressures is rated excellent when using systemic pesticides.
Air Induction (AI). Taking the same double-orifice strategy as the Turbo TeeJet, these nozzles also have holes to bring in air and produce large air-filled drops through the use of a venture air aspirator.
“AI nozzles have an outlet orifice that can be up to twice the size of the inlet orifice, which drops the pressure quite a bit,” Klein says. “But sucking the air in reduces the pressure loss. These nozzles create a larger particle size that can significantly reduce drift.”
This nozzle has become even more important as the self-propelled sprayer market grows.
“Drift wasn’t as big of an issue before self-propelled sprayers,” explains Will Smart, president of Greenleaf Technologies. “They might apply from 6 to 18 mph. A regular nozzle couldn’t handle that range because when you double speed, you quadruple pressure and the droplet size becomes very fine.
“Air injection nozzles can handle a wider pressure range without as much of a change in droplet size.”
Maintaining a larger particle size helps control drift, but it can also mean reduced coverage.
“If you get too big of a droplet, you can reduce efficacy, especially when using fewer gallons of carrier per acre,” Klein says. “You can instead go to more gallons of carrier to improve the coverage while using the larger, more drift-resistant particle size.”
Not all applications lend themselves well to larger spray volumes, Klein warns. More gallons of carrier and higher spray volumes with glyphosate applications mean more additives.
Applicators will get better results with a more concentrated mix, he says.
“Instead, increase performance by going to a smaller droplet size that will get better coverage, but still balance that with managing drift,” Klein says.
The TurboDropXL from Greenleaf Technologies was the first AI on the market, Smart says, and has a slightly different design from other AIs.
“It was designed for contact chemicals, specifically Liberty and Ignite,” Smart explains. “Bayer needed a nozzle that would get good penetration and coverage to defend against resistance.
“With that in mind, engineers focused on achieving a medium droplet size across a wide spectrum of pressures. We achieved that and ours is the only air induction nozzle they recommend for applying these products.”
The TurboDropXL is a two-piece AI. It has a patented stabilization chamber and pulsation dampener to more evenly mix the air and chemical, which results in a more uniform droplet spectrum. The two-piece design allows many different pattern tips to be easily and quickly interchanged.
“You can quickly change the spray operation in the field, putting on a different pattern, changing the spray angle or even putting on a twin fan,” Smart says. “You’re still using the same metering device, just changing the tip.
“Some farmers even take off the spray tip and use the TurboDrop Venturi alone as a streaming nozzle for fertilizer. It’s a very versatile nozzle.”
Air Induction Extended Range (AIXR). These nozzles do not have as much difference in orifice size, and are designed so they can be used at lower pressures. Extended range refers to the fact that the nozzles can be used at a wider range of pressures.
“For most regular air induction nozzles, we suggest that they be used at 50 to 70 psi with many pesticides, and you can use the AIXR nozzles at 30 to 50 psi with good results,” Klein says.
Extended Range Flat Fan. Usually used at about 25 to 40 psi for herbicides, these nozzles are ideal for getting thorough coverage with contact herbicides, insecticides and fungicides at lower spray pressures.
“With a traditional flat fan nozzle, you can spray in wind conditions up to 7 mph and still get good coverage,” says Allen Harmon, Lechler USA agricultural division manager.
The crop growth stage, chemical and timing are things producers must consider when setting up a spray rig.
“Take the time to pick the right tip,” says Peter DeHaan, TeeJet Technologies applications engineer. “Know what pressure you like to spray at, what droplet size you want and how the chemical you’re applying works.”
He explains that when applying a contact herbicide, producers will need to produce a smaller droplet size to achieve better coverage. Systemic herbicides, such as glyphosate, move through the plant so complete coverage isn’t necessary and larger droplets can be used.
Figuring out what size of droplet needed should be easier in the future, Klein says, as many pesticide labels will include recommended carrier rate and ideal spray particle size.
The recommendation will vary from product to product. Fungicides require better coverage and a finer spray particle; with fertilizer applications, you can use a nozzle which gives a large particle size.
“When putting down a pre-emergence herbicide with nitrogen, it’s more beneficial to use a larger droplet,” says DeHaan. “There’s no reason to risk losing chemical to drift when you just need to cover the ground.”
When better coverage is necessary, such as when applying fungicides, a twin nozzle setup may be the answer.
“Twin nozzles were first developed when we thought soybean rust was going to be an issue,” Harmon explains. “That didn’t develop, but this setup still provides the best coverage you can get and is a good way to spray.”
Using two nozzles set at different angles can help achieve great coverage while minimizing drift. Applicators can even use two different nozzles in a twin setup to get two spray patterns or a mix of particle sizes.
“A twin nozzle setup will have one nozzle spraying forward and one spraying backward with a 60-degree inclusion between the two,” DeHaan explains. “It’s like making two passes with half the material.”
He says hitting the plant from two different angles may help get better penetration into the canopy.
“Spraying from the front nozzle can get the crop moving a little; then the rearward nozzle reaches deeper into the foliage,” Harmon says.
Greenleaf Technologies’ asymmetric twin fan sprays 10 degrees forward and 50 degrees to the rear.
“When dealing with a vertical target, like wheat, the asymmetric twin fan will achieve coverage on both sides of the plant, which is difficult to do with a standard flat fan,” Smart says. A twin fan is a good idea when spraying small weeds. “They’re easy to control, but they’re also small targets,” he says. “You have to hit them to kill them. Two patterns coming out of one nozzle give you two chances to hit each weed.”
Fast or Slow
Speed is another important consideration, especially when determining what degree nozzle to purchase.
“An 80-degree, flat-fan nozzle is the most common in the industry and a 20-inch spacing is common on a row-crop boom,” Harmon says. “Ideally, that setup should be run 30 inches above the crop or bare ground for the best coverage.
“The industry also sells 90-, 110- and 120-degree flat fan nozzles. The difference is — using the 110-degree nozzle, for example — is it needs to be used steady at 20 inches above the crop.”
At 30 inches, producers can drive faster without as much concern that the boom tips will hit the ground. A lower boom height generally means slower application.
“If you’re trying to make sure your material reaches its target and doesn’t drift away, the 110-degree nozzles get you 10 inches closer to the crop with the same flow and pressure at a slower speed, resulting in less chance for drift,” Harmon says. “But when speed is most important, producers should choose a narrower pattern tip.”
Adjuvants In The Mix
Surfactants and crop oils can change the type of droplets that a nozzle produces.
They often affect the surface tension of spray droplets, which helps to ensure good coverage and better uptake by plants. This is especially important when applying chemical to crops with waxy leaves.
According to Ohio State University research, surfactants helped increase contact area with waxy leaves by a factor of 2 and the contact area with hairy leaves by a factor of 4 with medium-sized spray droplets.
While helpful for improving chances of chemical uptake, the resulting reduced surface tension of the water droplet may produce smaller droplets than they intended.
“It makes smaller droplets for better coverage, but it doesn’t make the droplets heavier, so they’re still subject to drift,” Harmon says. “The secret to spraying with adjuvants is to adjust your tankmix and program and slow down, spray during better weather conditions and pick a larger nozzle size that can be used at a lower pressure so you create less fines.”
Poor fall conditions in 2009 meant fewer anhydrous applications, so DeHaan expects to see more liquid fertilizer applications in 2010.
TeeJet Technologies makes two stream jet nozzles for applying liquid nitrogen, the SJ7 and the SJ3.
“The SJ7 forces material out of the tip parallel to the ground, then gravity pulls the seven different streams to the ground,” DeHaan says. “This allows more leeway for height-dependent distribution and is definitely great for sidedressing or topdressing.”
But no-tillers may want to opt for the SJ3.
“Distribution isn’t as good with the SJ3, but because it sprays straight down to the ground instead of relying on gravity, it gets better penetration, which may be better for getting through no-till crop residue,” DeHaan says.
No-tillers who want to achieve variable-rate fertilizer applications with sprayers have a new option. The six-hole streaming TurboDrop variable-rate fertilizer nozzle allows four different rates of fertilizer to be applied at any speed and can maintain a constant rate through a 4X speed change.
“Instead of making a massive pressure change to achieve this, an additional flow path opens inside the nozzle at a certain point to allow more chemical to flow through,” Smart explains.
No matter the tip, producers need to know the weight of liquid fertilizer when calibrating their sprayers.
“All the rate charts for tips are published for water, but liquid fertilizer is denser,” DeHaan says. “Make sure to do rate conversions dependent on the weight of the fertilizer being applied and set the pressure accordingly.”
Plastic, Stainless Or Ceramic?
After selecting the right nozzle type, applicators need to determine what material their nozzles should be made of. They can choose brass, stainless steel, ceramic and a variety of plastics.
“Ceramic nozzles wear much better than anything else. A producer might get 50,000 acres out of a nozzle if they aren’t spraying abrasive chemicals,” Harmon says. “But they will break.
“If you have rough, uneven ground or strike the boom tips on the ground or any obstructions, they can fracture.”
If nozzle breakage is a concern, stainless steel or plastic are good options. Brass is available, but wears the most of all the materials that nozzles are made of, Harmon says.
Most plastics hold up well and are affordable, but Harmon says some chemicals could ruin plastic nozzles.
Cotton defoliation programs may have multiple chemicals mixed together and they’re acidic, and that means they will soften plastics. A grower can choose polypropylene plastic nozzles that are chemical resistant.
Pick The Nozzle
Once an applicator has pinned down their desired pressure, speed, nozzle type and droplet size, picking the right nozzle should be simple.
The American Society of Agricultural Engineers and the British Crop Protection Council created six droplet size classifications that promote understanding of drift potential.
Every spray tip manufacturer prints the ISO color-coded classifications for the flow rate produced by each nozzle through its range of pressures.
“Once you know the nozzle size you need and the pressure range you want to work with, use the chart to pick the nozzle that works,” Smart says. “If two different nozzles fit your needs, go with the one that gives you the right droplet size for the application.
“With the TurboDrop, medium has proven to be the most useful droplet size, but coarse is usually good for glyphosate. You can often achieve either droplet size by simply adjusting pressure.”
Tips On Tips
Experts share these general tips:
“I purchase combination nozzles where the tip is built right into the cap for quick attachments,” Klein says. “I buy several extra so if a nozzle gets plugged in the field, I snap in a new one and keep moving. Then I clean out the plugged nozzles back at the shop with compressed air to do it safely.”
“There are a lot of factors that go into tip wear, so you never know how much use you’ll get out of a tip,” DeHaan says. “Buy an extra tip and keep it in the cab. A few times a year, snap that tip on and do a collection test comparing that new tip to another tip on the sprayer.
“If the spray volume is 10% different for the same time and pressure, it’s time to change your tips.”
“Don’t be afraid to replace a nozzle or trade out different nozzles during the spray season to get the job done right,” Klein says. “The quality job a $250,000 sprayer does depends almost entirely on that $5 to $20 nozzle tip.”