Unpublished early draft, December 2010
(too much product, not independent enough)

Nozzle choices for spring spray applications

With a wide array of nozzle types available from manufacturers, how do you decide which is best for you? We asked the nozzle makers, a top sprayer operator and a sprayer research specialist about the nozzles they would select for spring spraying.

Sprayer operators are spoiled for choice when it comes to selecting nozzles. With healthy competition between manufacturers, each offering a range of different nozzle types, you could easily spend hours researching what’s available and the claims made to justify their inclusion on the price lists.
The HGCA’s Nozzle Selection chart is a good starting point for anyone looking for guidance on the best nozzle to use for combineable crops, but even here there’s no definitive answer. In many cases two different nozzle types are said to be the preferred choice for efficacy, while for glyphosate application three types are given this honour.
To help shed some light on the issue, we spoke to a selection of people with first-hand knowledge of sprayer nozzles and spraying, and where better to start than Billericay Farm Services, which claims to be the originator of the air inclusion nozzle (see panel), sold as the BFS Bubble Jet.
The company’s Stephen Kateley had no hesitation in making his recommendation.
“For boom spraying, there are only two useful nozzles,” he said. “A Billericay Bubble Jet for day-to-day spraying and a flat fan nozzle for narrow targets.
“You may well be thinking ‘he would say that’ because these are the only nozzles we sell, but that’s the message we get back from our customers.”
It’s a picture that’s at odds with the HGCA recommendations because it tends to favour flat fan nozzles over air inclusion types for normal spraying conditions, but Mr Kateley is used to holding his ground.
“Quite simply, I don’t agree with the HGCA analysis,” he said. “They don’t credit a 500 micron Bubble Jet droplet with the same coverage properties as the much smaller droplets produced by a flat fan nozzles, yet our experience in the field is that the larger droplet, which contains air and smaller droplets, will collapse on impact with the leaf to provide better coverage than smaller flat fan droplets.
“A direct comparison between our nozzles has shown that the flat fan will get 75 per cent of the spray onto the target, while the air inclusion nozzle will achieve 95 per cent.
“For everything other than narrow targets a Bubble Jet is all you need.”
Where a flat fan nozzle might prove useful in the spring is in spring-sown crops where newly emerging seedlings and weeds are too small to be effectively treated with the larger droplets from an air inclusion nozzle.
“When you’re dealing with narrow targets it’s best to go out with a flat fan nozzle, but if it starts to blow up I wouldn’t rule out switching to an air inclusion nozzle,” Mr Kateley said. “It’s the same story if you’re on the fifth day of a six-day spray window, you just have to change to a Bubble Jet and get on with the job.”
Billericay sells nine sizes of Bubble Jet nozzle and the company is keen for operators to select the best size for the job at hand.
“Each nozzle has been designed to provide the ideal spray pattern and droplet size at its quoted working pressure, so we don’t really advocate changing the pressure to manipulate spray quality or application rates,” Mr Kateley said. “Clearly it’s a good idea to drop the pressure a bit on the headlands to get larger droplets and minimise drift, but it’s important to operate at the correct working pressure for the nozzle in the main body of the field.”
Billericay takes its spray pattern and quality extremely seriously and has built a calculator into its website that will recommend the best nozzles for the job for any given application rate and forward speed.
“Our calculator will give a selection of three or four nozzles with different working pressures that will do the job so you can select the one most appropriate to your sprayer,” he said. “Each option is also given a VMD (volume median diameter) value which is a scientific measure of droplet size and a figure for driftables, expressed as a percentage, that gives an indication of the number of small droplets at risk of being blown off target.”
So, given a three-way nozzle holder, what would Mr Kateley suggest spray operators fit.
“Clearly you want a flat fan nozzle for the narrow targets, but I’d suggest Bubble Jet nozzles for the other two spaces,” he said. “One set should be for your most common spraying set-up in terms of forward speed and application rate, with the other used for either situations where you want to travel faster across the field, or where a higher application rate is needed.
“For customers that want to experiment with different spraying set-ups, we also supply a single angled cap to change the incline of our nozzles, or a twin-cap adaptor that gives in a forward- and rear-facing nozzle spray pattern.”
At Hypro, Roger James is in broad agreement about the selection of nozzles that an operator might select for spring applications. Once again air inclusion types are the default choice with the company’s GuardianAir nozzle taking up position one and the Drift Beta, with its coarser droplets, filling the second slot for use in more challenging conditions. He would also go for a flat fan nozzle to complete the line-up, but would choose one with variable pressure characteristics to maximise flexibility.
“We find that there are really two types of sprayer operators: those that just want to fit one nozzle and get on with the job and those that want to spend time and think about the task at hand,” Mr James said. “Operators that benefit from the advice of agronomists will also be bombarded with suggestions about which nozzles to use, but in the end they need to be pragmatic about their choices. In a situation where spraying time is limited, it’s better to get round the whole farm and apply active ingredient adequately to all the crops than to apply it perfectly to just half.
“The reality is that most spraying situations will require a degree of compromise.”
In contrast to BFS, Hypro’s nozzle development programme has taken the company down the route of both single and twin angled nozzles, and the company has enjoyed a great deal of success with its GuardianAir air inclusion nozzle that has a built-in rear-facing incline.
“We designed the GuardianAir to compensate for the forward motion of the sprayer,” Mr James said. “We found that when the spray mixture is sent straight down from the boom, the fact the sprayer is moving forward results in the active ingredient carrying a momentum that results in it hitting the side of the crop; but if the nozzle is inclined to the rear, this balances out the effect of the forward motion and you get an even downward spray.”
Hypro is also a proponent of using water pressure in the spray mixture to fine tune the spray pattern to compensate for changing conditions in the field.
“If you choose your nozzle based on forward speed, a good spraying day and a crop with a good canopy might dictate an 035 nozzle to achieve 16km/hr at 3bar pressure, but if it’s a bit breezy and you’re working close to the ground, 10km/hr at 3bar will call for a 02 nozzle,” Mr James said. “But with the right nozzle, there’s really no reason why you couldn’t use an 03 for both applications by varying the pressure in the spray circuit.
“If you set an application rate in modern spray controllers, the pressure will be used to compensate for changes in speed and operators can use this to their advantage. A GuardianAir nozzle designed for 3bar can actually hold its spray pattern down to 1.50 or even 1.25bar. Clearly there will be a change in droplet size, and agronomists might not be keen on the idea, but the results will still be acceptable.”
A new development for 2011 from Hypro is the GuardianAir Twin, which produces twin air inclusion spray patterns 40 degrees forward and 40 degrees back from a single nozzle.
“There’s clearly a growing interest in this mode of spraying and we felt it made sense to produce a single nozzle for the job instead,” Mr James said. “In cost terms alone, buying a single GuardianAir Twin nozzle at about £6 is going to be more attractive than paying £12 or more for two nozzles and a twin cap to fit them to.
“The new nozzle will be available in limited quantities for the first year to spray operators that are keen on experimentation so that we can keep an eye on them and evaluate best practice.”
TeeJet’s Martin Baxter had no argument with making air inclusion nozzles the default spraying choice, in fact he can’t understand why flat fan types are still the most popular among sprayer operators.
“Clearly most agronomists are still playing it safe, and if the label on the active ingredient calls for a medium droplet size, they will automatically recommend a flat fan nozzle,” he said. “Despite the what we’re hearing from customers and reading in the farming press, not everyone has caught up with the fact that you’ll get just as good a result from air inclusion nozzles.”
Naturally TeeJet offers a comprehensive range of conventional and air induction nozzles including the AIC and AIXR Air Induction Flat SprayTips with single 110-degree spray pattern and the AITT Air Induction TwinJet with dual 110-degree spray fans set 30 degrees forward and 30 degrees back.
Backing up the manufacturers in this debate is Clare Butler-Ellis of NIAB TAG who agrees with fitting two air inclusion nozzles and one conventional flat fan on the triple nozzle adapter.
“In the spring there’s a clear advantage in using an air inclusion nozzle, except where you’re spraying early growth stage spring crops,” she said. “I really don’t think you’ll see any difference between using an air inclusion nozzle and a standard flat fan when you’re spraying into an established crop canopy in normal spraying conditions.
“In fact in any crop where the targets are a reasonable size, an air inclusion nozzle will deliver good drift control and good efficacy.”
Ms Butler-Ellis emphasised, however, that even with an air inclusion nozzle, sprayer operators still had to be careful in windy conditions.
“The rules state that you shouldn’t be spraying at wind speeds of more than 6.0m/s and that applies no matter what nozzle you are using,” she said. “However, it’s worth recognising that the windspeeds given in weather forecasts are quoted for 10m above the ground, so it’s worth checking the local windspeed at boom level, which can be considerably lower.”
Cambridgeshire-based independent agronomist and former sprayer operator of the year David Felce is well placed to provide an opinion on nozzle choice and he disagrees with the premise that the air inclusion nozzle is the prime choice.
“My default will always be the conventional flat fan,” he said, “although I would also choose two air inclusion nozzles: one small droplet type for drift control and a few specialist jobs, and an angled nozzle like the Syngenta Defy for pre-ems and early season grass weed control.”
Mr Felce acknowledges there has been a massive improvement in the choice of nozzles available in the past five years or so, but the flat fan remains hard to beat.
“Given ideal spraying conditions with little wind, good application timing and good boom stability, a flat fan nozzle will do a pretty good job on just about any crop,” he said. “Farms with a limited acreage that they can get through in a day can afford to wait for ideal conditions to get their spraying done; for them, the flat fan is really all they need.
“If the spraying takes a few days, however, and you need to maximise both timing and applications that’s when nozzle choice comes into play.”
Mr Felce added that while air inclusion nozzles allowed spraying in conditions where there was too much blow-up from flat fan types, they also represented a compromise.
“You can’t have your cake and eat it,” he said. “The larger droplets from the air inclusion nozzles reduce drift, but they also reduce coverage of the crop. You’ll have to decide on each occasion whether it’s acceptable to compromise, or whether spray quality has to come first and it’s a case of waiting until conditions are right.”
Mr Felce has been impressed by results from Syngenta’s Defy nozzle to the extent that he would give it the third position on his triple nozzle carrier.
“This nozzle has a 40-degree angle, so it produces a flatter trajectory and has shown excellent results on vertical leaf targets when used facing forward,” he said. “The Defy nozzle also has an important pre-emergence role with alternate nozzles facing forward and back. Used in this way you can coat both faces of clods and ensure good distribution of active ingredient on the soil.
“Spray operators are spoilt for choice these days and there’s scope for everyone to spend a bit more time thinking about which nozzle they should use. When it comes down to it, the operator’s job is to pick the right one for the task and then to use it correctly.”


The birth of the Bubble Jet

Billericay Farm Services developed its Bubble Jet nozzle in the early 1990s to placate the operators of the firm’s contract sprayer fleet.
According to the company’s Stephen Kateley, the sprayer drivers were prone to complaining if they couldn’t go out spraying because it was too windy as they lost out on productivity bonuses.
“Billericay’s owner, Anthony Cecil, considered fitting the sprayer fleet with the novel Airtec system to give the operators a wider application window, but he was put off by the cost,” he said. “Instead, Mr Cecil set about designing a nozzle that would do the same job, but more cost effectively.
“The concept was to produce a self-contained nozzle that would use the venturi principle to combine air with spray mix to get the same resilient spray pattern that the Airtec system – which used compressed air – produced. It took a couple of years to get to the design right, but the same principle remains behind the Bubble Jet nozzle range we sell today.”

The future of spraying

While she can’t see any obvious improvements or additions to the range of traditional spraying nozzles currently offered by manufacturers, Clare Butler-Ellis of NIAB TAG suggested that a revolution in spraying practices might be needed to get the huge cut in chemical use that is needed to protect our current armoury of active ingredients.
“If we want to stop losing actives we need to stop then getting into water and one way to do that is to use a lot less product,” she said. “The only practical way of achieving this is to target the use of products to a much higher degree, either only spraying the parts of a field that are affected by a pest or weed, or by treating the individual weeds.
“Today’s sprayers and nozzles can provide targeted treatments across selected parts of a field, but there’s a lot of development work ahead to get to the point where individual weeds can be identified in the crop and treated appropriately.”

Making nozzle choice clearer

More could be done to make nozzle choice easier for sprayer operators according to Clare Butler-Ellis of NIAB TAG.
“There needs to be more interaction between the active ingredient manufacturers and the nozzle makers,” she said. “Syngenta, for example, has to be applauded for promoting specific nozzles for specific products from its range.
“On the whole, the nozzles were already available, but Syngenta has taken the time to go out and select the best nozzles for its active ingredients and rebrand them under the Syngenta name.
“By linking the nozzles with particular products, sprayer operators can easily match the product in the tank with the correct nozzle on the sprayer boom.”