Spraying Advice, Drift reduction

How can you get the spray timing right when the weather and workload conspire against you?

Why efficient spraying?

How to spray all of the farm's cropping in the limited number of available spray days is one of the key challenges facing many growers.

Weather data recorded over nine years in the so-called "dry" county of Cambridgeshire show, during the busy spray timings of April,

May and October, only around a third of the month was suitable for spraying. This was based on suitable conditions of wind speed,

temperature and rain. In wetter areas, these figures could be lower.

But that's only half the story. With many weeds, pests or diseases, for every day that treatment is delayed, crop yield suffers. Work with wild oats

has shown delaying treatment from around mid April to late May reduced wheat yield by 1.2t/ha. That was despite achieving 98-100%

control at each timing.

As farms get larger, but often with fewer staff, efficient and timely spraying is not only important to simply "get the job done" but it can also have

a direct impact on the farm's bottom line. As a rule of thumb, you should be able to spray all your wheat in under three days.

What can be done?

Among the many factors that can affect the ability to achieve this, two of them stand out as being possible to do something about:

Boom height and drift

The further a spray droplet falls, the greater the chance it will drift. In fact, a key component of reducing spray drift is setting the boom height

correctly. Despite this, many sprayers still operate with booms set too high - at up to 1 metre. In reality, 40-50 cms from the target is

optimum for a 110° flat fan nozzle, this applies whether the target is the soil for a pre-emergence product or the crop for a foliar spray.

By lowering the boom to the optimum, not only can spray performance be improved,

but drift reduced and therefore more spraying opportunities opened up (more to

come on boom set-up in a future Academy).

To put this into perspective, consider the following:

At a wind speed of force 4 you must not spray

However, by either reducing boom height to the optimal level, or choosing a less

drift-prone nozzle, it is possible to achieve the same level of drift reduction as

with a drop of 1 level of wind speed on the Beaufort scale.

Setting boom height

A simple boom height cable tie available through Syngenta's Intelligent Farming

initiative can help set boom height accurately. It also provides a simple yet

effective solution for maintaining boom height while spraying, rather than judging it by eye.

Specially graduated at 5cm intervals along its length, it is simply attached to the boom end and trimmed to the required height using the

graduations as a guide (for example 10 graduations = 50cm). In this way, by adjusting the boom so that the end of the tie just touches

the target, users can optimise the distance that spray droplets fall.

Nozzle choice

Of course, combining correct boom height with optimum nozzle choice can help to reduce drift further.

Air induction nozzles are particularly good at reducing spray drift. The Amistar nozzle, for example, uses air induction principles and can give

double the work rate for about a quarter of the drift.

Filling efficiencies

The process of spraying itself is only one area where efficiency gains can be made. There are also gains to be had in the yard.

Anything which cuts down the time required for sprayer filling and the amount of washing out can improve work rates - to the extent where

it may even be possible to apply an extra sprayer load during the day.

choosing products which come in bottles with foil-free caps eliminates the time for removing, rinsing and

disposing of foils. Importantly, it also reduces the amount of contaminated waste. In all, it could save

about 40 seconds per pack, so could be especially useful for products in smaller 1-litre bottles.

Similarly, using a product which is approved in both wheat and barley can cut down on the time needed to

return to the farm to wash out the sprayer between crops - with estimated savings of 40 minutes or

£70 per product change for returning to the farm to wash out and refill. It also means fewer different

products to store and keep records on.

There are also time savings from using pre-formulated mixtures during time-critical periods such as T1 and

T2 - rather than DIY tank mixtures. You should also consider products which come in larger packs.

Using a ready-formulated mixture means fewer packs to load into the sprayer, fewer packs to dispose of

(important given the imminent burning ban) and, most important of all, fewer packs for rinsing.

Typically, this could save as much as 10 minutes per fill-up, which can stack up significantly when

looking to fit that extra sprayer load in a day. These simple changes could mean less time, less hassle and less disposing of waste.

Spraying, Boom stability

Suspension and tyres

Boom stability not only comes from correct set-up and maintenance of the boom suspension, but also operating with correct tyre pressures,

since tyres act as both a spring and a shock absorber. Running with pressures too high not only reduces traction but also stiffens the ride

Combined together, the suspension and tyres therefore play a major role in smoothing out surface irregularities in tramlines while spraying.

This is essential for getting the best result with any crop protection product, because it

helps achieve an even spray deposition across the entire width of the spray swath.

With an unstable boom, major problems arise at the ends furthest away from the sprayer, since

any movement created as the sprayer passes over uneven ground is magnified by the time

it reaches the boom tips. This is especially so with a wider sprayer.

The result is that the outside of the boom travels either faster or slower as it bounces around

compared with the inside, so will either deposit less or more chemical on the target than

it should.

Spray coverage results

To illustrate just how dramatic this can be, look at the differences in the number of droplets in the

photograph when water sensitive paper was placed horizontally on short posts in a wheat

crop in April, and the sprayer then driven over a specially-prepared bumpy track.

The paper with the most droplets was from the outside end of the boom on a well set-up sprayer

running with correct tyre pressures. By contrast, the paper with fewest droplets was taken

from the same position, but this time with poorly set sprayer suspension (in this case

locked off to simulate badly maintained or seized suspension) and with the sprayer tyre

pressures set too high (in this case 3 bars). As an estimate, there was probably less than half the

amount of spray deposited with the poorer set-up. If this coverage had been achieved using a crop

protection product which produces a highly visible result, for example wild oat control, it is likely

you'd be very disappointed with the level of control resulting from such under-dosing at the outside

of the boom compared to the inside, particularly if already applying it at a reduced dose.

Putting it right

Maximum boom stability is therefore critical for product performance and on modern sprayers it can be relatively simple to check. To ensure correct

set-up, check the tyre pressures against those in the manufacturer's handbook and ensure the various suspension components are working

as they should be. Very often, new tyres might come with the same pressures that were used to blow them on to the wheel rim. This might

have been fine at the time, but not for spraying. In the case of the sprayer used in the water sensitive paper experiment, the correct tyre

pressure according to the handbook was 1.2 bars, which helped achieve the desired result. Think for a moment, how often do you measure your tyre

pressures? For optimum spray performance the tyre pressure should be the lowest recommended for the weight to be carried.

Yaw and roll

The two key components which upset boom stability are yaw, which is the boom swinging backwards and

forwards at its outer edges, and roll, which is the boom ends moving up and down.

To check for roll, push the boom end down a foot and it should come back to the horizontal and not oscillate

up and down. For yaw, when moving the boom backwards and forwards, check that all its suspension

joints are fully lubricated and that springs and shock absorbers are working correctly. Listen out for

the oil moving in the shock absorbers as a guide. All these checks take just a few moments to carry

out on a regular basis, yet can have far-reaching results.

Forward speed

As well as boom stability, forward speed can also help spraying efficiency, by improving work rates by

covering more hectares per day. Spraying faster isn't simply about increasing tractor speed and

raising the spray pressure to maintain equivalent output.

This is because the amount of drift increases significantly with higher nozzle pressures and with the

extra turbulence created as the sprayer moves faster. Drag and turbulence, for example, increase

at the rate of the square of the increase in forward speed relative to the original speed. So if you

increase the forward speed from 12 to 16kph, turbulence is increased by nearly 80%. For these reasons, it is always essential to ensure a

stable boom for the speed you are spraying at, to use the correct nozzles in relation to forward speed, and to maintain the correct boom height.

Fortunately, with modern nozzles it is possible to swap from a standard spray to a less drifty alternative, such as the Amistar nozzle, very simply.

This can give you double the work rate for about a quarter of the drift. Wind direction also has an impact on spray drift. Clearly, it is essential to

only spray when wind speeds permit. However, spraying in the same direction as a breeze tends to give less drift than when driving into one. This is

because, with the breeze behind the sprayer, its direction tends to counter any turbulence caused by the movement of the sprayer, rather than

add to it. Currently, the average sprayer speed is around 12kph. There is a good case to increase this. Some fungicides, for example, have

worked well at speeds up to 16kph.

Water volume & nozzle choice

Obvious parameters for application efficiency, and easy wins, are spray volume and nozzle choice.

Why efficient spraying?

Having looked in the previous Academies at the impact of boom set-up, filling operations and forward speed, in this final instalment we look at some

of the more obvious parameters for application efficiency - spray water volume and nozzle choice. Clearly, spraying at reduced water volumes

is not possible with all products and must only be carried out where it is permitted by the timing, target, nozzle choice and spray pressure.

Careful consideration should be given before reducing water volumes.

But, where possible, lower water volumes are a very efficient way to go spraying.

Approved product

If you reduce the water volume from 200 to 100 litres/ha (with a label-approved product), then straight away you have doubled the capacity of your sprayer.

Using the example in the table - for a 2500-litre sprayer operating at 12kph and taking into account time for filling, travelling, etc - this reduction would

allow an extra 23ha a day to be treated at the lower volume.

If you had to hire a contractor to spray those 23ha to catch up, based on a contract spraying cost

of £10/ha, that would equate to about £230. In addition, studies have shown that if a T2

fungicide is delayed, then yield can fall by 70kg/ha a day, or the equivalent of about 0.5t a week.

Assuming a grain price of £80/t over 23ha the 70kg reduction would equate to a £128 a day loss.

Therefore, these two factors could make a difference of more than £350.

A further advantage of lower water volume spraying is that some products can actually work

better, enabling you to achieve a biological improvement as well.

Appropriate nozzles

Alongside reducing water volumes, appropriate nozzle choice can also boost efficiency. Fitting

the right nozzles for the job brings benefits in three ways:

1. Reduced drift - as with boom height, correct nozzles can minimise drift and, therefore,

open up more spraying opportunities. Air induction nozzles are particularly good at reducing drift, but are not widely used.

2. Increased workrates - by allowing more hectares to be sprayed a day (linked, where possible, to reduced water volumes and faster forward speeds).

3. Improved product performance - by getting more spray on the target and from

more timely spraying (again from work rates and making best use of spray

windows).

Typically, a standard nozzle fitted to sprayers is a variable pressure 110° -05 flat

fan nozzle. It will produce a medium quality spray at 200 litres/ha and, by

and large, will do a good job. But its performance can often be improved.

Often, they are used at too high a pressure. But they produce less drift at 2 bars

than at the more traditional 3 bars. So when choosing a new set of standard

nozzles, calculate the correct output at about 2 bars pressure rather than 3

bars and you could extend spraying opportunities by reducing drift.

Specialist nozzles

Specialist nozzles, although perhaps costing more, can offer advantages.

When choosing nozzles, a key aim is to get maximum spray on to the target and

minimise the amount wasted.

For spring and summer use, the Amistar Nozzle is a very low-drift nozzle, with a

3-star LERAP rating. It was developed specifically for spraying cereals in particular, at the ear or T3 timing, where its angled tip has been specially

designed to produce even coverage on both sides of the ear or plant as the sprayer passes over. Its benefits include more spray days with a

quarter of the amount of drift, and it has produced about 0.3t more yield when used to apply the same fungicide mix.

Low drift

The Amistar nozzle also produces lots of droplets per litre, and has been shown through trials to be as effective for spring grassweed control. It has been

found to deposit 30% more spray on a wild oat target than an alternative nozzle. Therefore, new for the 2007 season, it is the preferred nozzle for

Axial (pinoxaden) where it is permitted to be used in 100 litres/ha spray volume because it:

Deposits more spray on wild oats.

Utilises air induction principles. to cut spray drift and, therefore, increases available spray days.

Allows faster work rates from a 100 litres/ha spray volume (where this is permitted).

Autumn nozzle

Similarly for autumn, the 40° forward-angled Hawk nozzle has been shown to deposit more than double the amount of spray compared with a vertical

nozzle on small blackgrass plants, which are a notoriously difficult spray target to hit. This should achieve better blackgrass control and give

higher yields. Meanwhile, for a pre-emergence herbicide application, where bare soil is the target, using alternating fore- and backward-facing

Hawk nozzles along the length of the boom evens out coverage on both sides of clods. The Hawk nozzle is also designed for a 100-litre/ha spray volume,

for faster work rates and to make maximum use of spray windows. In summary, choosing the right nozzle for the job can produce better control (for

example, grass weeds), give higher yields and improved work rates from more spray days.

Spraying on livestock farms

Weedkillers protect crops and control grassland weeds, but they need to be kept out of water

Weedkillers, or herbicides, are valuable tools for producing home-grown forage, or maintaining productive grassland. Weeds reduce both quantity

and quality of forage crops and may poison stock. Some weeds, such as ragwort, must be controlled by law. Grassland weedkillers account for

just 10% of the value of the UK crop protection market and, on average, lowland

grassland is sprayed once every four or five years. Yet several herbicides,

traditionally used on spring crops and grassland, are regularly found in water

by environment agencies and water companies. While they may not threaten

aquatic life, they can increase the cost of drinking water treatment.

The law

Herbicides are classed as "plant protection products" and legally defined as

pesticides. All products that control "pests" need an approval from the Pesticides

Safety Directorate (PSD). This specifies what crops can be treated, application

rates and safety precautions. All this is on the product label which users must

follow. Additionally, the statutory Code of Practice for Using Plant Protection

Products, for the best practice advice visit

www.pesticides.gov.uk

on best practice. Failure to comply can jeopardise single farm payments.

Training

Legal controls also apply to training pesticide users. Health and Safety at Work

legislation requires all users to be trained and competent. However, for

pesticides anyone born after the 31 December 1964, contracting (including

helping a neighbour) or supervising an unqualified operator must hold an

NPTC certificate of competence. The National Register of Sprayer Operators

(NRoSO) has been set up by the Voluntary Initiative (VI). Almost 20,000

farmers and operators have now joined the scheme to benefit from regular

refresher training

Choosing weedkillers

Begin by identifying which weeds to control. To ensure correct identification and

product choice, consult a BASIS-registered adviser who is up to speed with

the latest recommendations and will know what is best for your particular situation. There should be one at your local merchant. The adviser should also provide

a recommendation sheet on what and how much to use in each field. He can also advise on correct storage, local contractors and disposal.

Storage

Concentrated pesticides pose the greatest risk, so product storage needs to be up to scratch. However, it need not be complex or expensive. For instance, a chest

freezer - correctly labelled, leakproof and locked - is a good solution for a small

livestock farm. Pay particular attention to fire prevention, as tackling a pesticide

store fire poses a major risk to water.

Buy only what is needed for each season. Each year check products held in

store are still approved. Check approval status by asking a BASIS-registered

adviser or use the pesticide register database at

www.pesticides.gov.uk

Check the sprayer

A correctly set up sprayer reduces the risk of pesticides reaching water and ensures

it does a good job. Before the spraying season use clean water to check the

sprayer is in good working order. Run the sprayer under pressure to check for

drips and leaks. Where necessary, tighten clips and replace damaged pipes

and washers. Check there is a full, matching set of nozzles producing an even spray

pattern across the boom. Use a one minute/30 second jug test to check nozzle

flow rates are consistent. When variation between nozzles exceeds 10% replace

the set. Check the pressure gauge - spraying at too high a pressure increases

spray drift. Most features can be independently checked by the National

Sprayer Testing Scheme (NSTS). (See checklist at

www.nsts.org.uk)

Filling, handling and disposal

Filling, handling and disposal practices are the most likely sources of pesticides

reaching water from livestock farms. Inspect the filling area identify where rain

water and any spills or run-off go. Farmyards often drain into a local stream or

ditch, so it may be necessary to re-site the filling area or seal off drains. A drip tray

or portable bund, can be used underneath a sprayer when filling on grass concrete

or hardcore.

Alternatively, fill in a bunded concrete area where drainage is actively managed to

stop pesticides reaching water, for example through a lined biobed. Ensure

there is enough space to work in. Keep cat litter on hand to mop up spills. Never

wash spills down the drain and take care to avoid tiny splashes when filling.

There is a strong risk of back-siphoning when filling, so use a bowser or separate

storage tank and ensure the water supply is connected via a double check valve.

Never take water direct from the mains, troughs or a river. Never leave a sprayer unattended while it is being filled. Once empty, containers should be triple rinsed,

allowed to drain and stored ready for professional disposal. Good disposal contractors will supply storage containers. Ask the contractor if different packaging

materials need to be separated. Before moving to the field, check for drips and leaks, then set agitation to the minimum required (eg 200rpm pto speed) to avoid

foaming while travelling.

Application

On the day, think through the spray operation. Check the recommendation sheet and the product label. Consider the conditions. Never spray when it is too windy,

(Force 4 or more 10-15km/hour (6-9mph)), the ground is frozen or waterlogged or if heavy rain is forecast in the next few days. Identify an area of the field where the

weed problem is less and leave untreated, so you can use it for leftover spray solution and/or sprayer washings. In the field observe any label restrictions on spraying

near water or hedges. Wherever practical, leave a 5m no-spray zone beside watercourses, hedges and neighbouring properties. With standard 110 flat fan nozzles

keep boom height 40-50cm above the crop. On uneven ground boom height may need adjusting, but increasing boom height will increase drift. After spraying, wash

the sprayer down before deposits dry. Modern sprayers often have a clean water tank, hose and brush attached with internal nozzles to clean the tank. These make

cleaning quick and easy in the field and may be available as a retrofit option. Failing this, the sprayer should be cleaned on grass well away from water. Focus external

cleaning on the boom, back of the spray tank and rear tractor wheels. Always park the sprayer under cover to protect it from the elements and to ensure any remaining

residues are not washed off. Finally, record all spray applications. These will certainly be checked at cross-compliance or farm assurance inspections.

Contractors

A contractor can take a lot of hassle out of spraying, but the farmer is still responsible for ensuring he complies with the law. Be sure: Contract spray operator holds

the right NPTC certificate of competence and is a member of NRoSO, Sprayer has current NSTS certificate, Any filling point poses no risks to water, Containers are

cleaned and drained for disposal, Agree who is responsible for disposal, Accurate spray records are promptly supplied.

What is a pesticide?

"Pesticide" is a broad definition within the Food and Environment Protection Act 1985 which includes herbicides, fungicides, insecticides, growth regulators, soil st

erilants, rodenticides and wood preservatives among others.

Water quality standards

Stringent standards are set for water quality across Europe. Sophisticated monitoring can detect pesticide levels below one part in a billion - equivalent to one stem

in 111,000 hay bales or one baked bean in 21m cans.

Spray technology

The nozzles that you choose are a critical aspect of agrochemical performance.

At worst, choosing the wrong nozzles can make the product you are applying ineffective - if droplets are too fine they will drfit away or if too heavy they

will fall to the ground.

Equally important is accurate calibration and maintainining nozzles in good condition.

Careful consideration and understanding of spraying technology will always help you to do the best spraying job, maximising the effectiveness of the

products that you choose.

Achieving good spray coverage

For typical arable spraying operations, there are two types of nozzle to choose from; Conventional and Air-Included.

For conventional flat fan sprays spray quality varies according to nozzle size (flow in l/min) and pressure - with larger sizes and lower pressures producing

larger droplets. The spray quality for each nozzle size/pressure is defined by BCPC International Spray Classification System from very fine to very coarse.

Spray manufacturers indicate the optimum spray quality on their product labels.

Air Inclusion nozzles tend to produce droplets in the medium to coarse range, but offer reduced spray drift. This category is rapidly becoming the standard

nozzle for combinable crop spraying. The 2010 HGCA* Nozzle chart indicates the relative droplet size of different AI nozzles at 3 bar.

The new classification shows that only those AI nozzles with the smallest droplets are likely to be effective in the majority of applications. Bear in mind that

a droplet which is just 20% larger (VMD) will have just half as many droplets

More droplets means better spray coverage so more spray reaches the target.

Autumn Weed Control

Nozzle choice for autumn weed control

For Pre-Emergence

Where the target is the soil and the aim is to get as much sprayed as possible a drift reducing air-inclusion nozzle is ideal, especially a finer type

(GuardianAIR) which offers more spray droplets. Inclining the spray will offer the best spray distribution where soild surfaces are uneven.

Post-Emergence

A standard flat fan nozzle that includes more fine droplets than the air-inclusion type is preferred for post Em applications to small grass weeds. Looked

at from above, even a high population of blackgrass plants does not present very much leaf area to receive spray droplets.

It is important to follow label recommendations on water volume and spray quality but equally important is the angle at which the spray hits the target

soil or leaves.

Research carried out by Silsoe Reasearch Institute has shown that an inclined spray works much better, depositing twice as much spray onto 1-2 leaf

blackgrass plants.

Field trials using an flat fan nozzle with a 40 degree forward incline have confirmed this.

Grassweeds, Nozzles and application

Autumn spraying to control grassweeds, particularly post-emergence, demands the best possible spraying technique - more so than at any other time in

the spraying calendar.

Not only are grassweeds extremely competitive, but some, especially blackgrass, are becoming increasingly difficult to control as resistance spreads.

If that weren't enough, a small grassweed is also a difficult target to hit.

What should the autumn-applied sprays achieve?

The key aim with autumn grassweed control is to get the right amount of product onto the target - the correct dose transfer. This is probably more important

than coverage - the proportion of target area that has chemical on it, although when applied to small targets, sprays that will give the highest deposits will

also give good coverage.

So the aim is to get enough active ingredient to each weed - subsequent absorption and translocation will ensure the chemical does its job. Choosing the

right equipment and using it at the right time will go along way to meeting that aim.

What nozzles should you use in the autumn?

This depends on the timing. With pre-emergence sprays, there is evidence from field trials that weed control is not sensitive to the type of nozzle used

although those giving larger droplets such as air-induction nozzles will reduce the risk of drift. Results from laboratory studies have shown that angled

nozzles and fine sprays can help sprays wrap around clods.

But with post-emergence graminicides the application method is crucial. This is the most important difference between the two timings.

A 110˚ blue (03) conventional flat fan nozzle operating at a pressure of 3.0 bar to produce a medium/fine spray will put in the order of 50% more deposit

on a grassweed leaf than for example, an air-induction nozzle giving a droplet size in the middle of the range for this type of nozzle design. This is because

air-induction nozzles produce larger droplet sizes that are less well retained on small targets.

Some horizontal spray movement, particularly of the smaller droplet sizes, is useful when trying to hit a small grassweed with upright leaves. Such

movement can be generated by the wind but it is then really important to adjust boom height according to the manufacturer's recommendations to

minimise the risk of drift.

Angling nozzles will also generate horizontal spray movement but again care is needed to control the risk of drift by keeping the boom as low as possible.

The minimum boom height will be lower when nozzles are angled than when they are directed straight down. Alternating angled nozzles also reduces drift

when compared with those all angled forwards or backwards.

Once grassweeds get to about the four-leaf stage, air-induction nozzles can be used.

Does boom height matter when spraying bare soils?

Boom height is critical at any time, but especially so when applying pre- or peri-emergence when sprays are particularly prone to drift. With 110˚ flat fan

nozzles the boom should be no more than 0.5m above the soil surface.

This will always be preferred practice, as the nozzles are operating near the ground where wind speeds are slower and more predictable. And, all other

things being equal, if boom height is doubled, drift increases by a factor of between 5 and 10.

Are high speeds bad news?

Going slowly certainly helps boom stability, but timeliness will suffer. Going beyond 15kph risks running into a new set of problems.

The faster the sprayer travels, the more turbulence or "wake" it creates behind it. Small droplets tend to be pulled into areas of high turbulence, creating

drift, and these areas also produce greater levels of deposition on to plant targets.

This results in increasingly uneven distribution as speed increases. That's bad enough with pre-emergence treatments, but it can have a much bigger

effect when trying to hit small grassweeds with the recommended medium to fine quality spray.

Maintaining high speeds across a field can be difficult, particularly close to field boundaries and where travelling conditions vary. With rate controllers,

reduced speed translates to lower pressures that can change the nozzle pattern and result in an uneven distribution.

Generally the standard recommendation for spraying speed of 12-14kph looks robust.

What pressure should you use?

For most nozzles, there is no need to exceed 5 bar. High pressures should be avoided - they generally create smaller droplets which can cause drift

problems. Perhaps more importantly, pressures below the minimum recommended for the nozzle design should not be used since this will influence

the spray pattern from the nozzle.

The most important things to get right are the nozzle and droplet size - this will dictate operating pressure, which will usually end up being between

2 and 3 bar.

Variable pressure nozzles can operate effectively over a wider pressure range enabling a wider speed range to be used with rate control systems. But

some designs produce smaller droplets and may be more prone to drift, so these need using with care

What about water volume?

Many herbicides work better at 100 litres/ha than at 200 litres/ha. It has been shown that more active ingredient will be retained on small targets at

100 litres/ha compared with 200 litres/ha and so should be used unless there is a clear reason for using higher volumes. Using the lower volume will

also give advantages in work rate and timeliness.

However, going too low may involve the use of small nozzles that are prone to blockage. So the simple message when controlling grassweeds pre- or

post-emergence is to stick to a water volume of 100 litres/ha.

How important is timeliness?

Good spray days are few and far between in the autumn, especially later in the season. So making the most of them is vital - applying sprays at the

right soil moisture level, or when leaves are dry enough, or when wind speed and temperature are within tolerable limits can make a big difference to

spray efficacy.

Choosing suitable speeds for a given sprayer and using low water volumes can all help, as do fast turnaround times. It is important to develop a system

that fits well with the farm scale and layout and enables the maximum number of tankfuls of spray to be applied in a working day.

Establishing a good routine will help to ensure the sprayer is in the field at the right time

Golden rules

• Use a fine/medium spray to treat grassweeds early post emergence

• Consider using angled nozzles to treat small grassweeds

• Apply sprays in 100 litres of water per hectare

• Maintain the lowest boom height for the nozzle you are using

Don't

• Travel at speeds where the boom becomes unstable

• Operate at pressures outside of the specified range for the nozzles you are using

Nozzle choice

Choosing and maintaining the correct nozzles has an enormous impact on the accuracy and efficiency of agrochemical application. To select the

correct nozzle for the job, follow the steps below

(a) Follow the advice given on the product label (check whether there are any local environmental restrictions or requirements, such as LERAP in the UK)

(b) Check which type of spraying technique you will be using

(d) Check your forward speed – high speeds over 12Km/h will increase your work rate and slower speeds of 8-12km/h are better for penetrating

dense canopies

(e) Check your pressure – Finer droplets are produced at higher pressures - individual nozzle charts show this relationship. Always read the pesticide

label to determine which spray quality is required.

(f) Select the spray quality that you require. See below.

(g) Select the nozzle style for the required spray pattern

(h) Make sure that you have fulfilled all criteria before you reduce buffer zone widths with LERAP rated equipment.

(i) Check that all constraints have been accounted for e.g. output of your sprayer pump.

Spray Quality

The most important performance characteristic of an agricultural spray nozzle is the size and the variation of droplets or spray quality that it produces.

Conventional nozzles are classified by the droplet size that they produce at a given pressure according to the BCPC International Spray Classification

System (e.g. coarse, medium, fine).

Different air-inclusion nozzles also produce different spray quality but this cannot be determined by nozzle size. For example GuardianAIR nozzles

produce smaller droplets than any other AI nozzle. For comaprison of different AI nozzles see the 2010 HGCA Nozzle Chart.

For Hypro nozzles, droplet-size is measured using a Phase Doppler droplet analyser and expressed as the Volume Median Diameter (VMD) in microns (μm).

The VMD is droplet size where half of the volume of spray is larger and half is smaller than the stated droplet size.

Spray Pattern

Flat fan pattern

Available as a tapered spray for boom applications or an even spray for single nozzle applications, e.g. knapsacks, they have an elliptical orifice, which

produces a narrow oval pattern. Tapered nozzles produce a triangular spray pattern where most of the spray is deposited immediately under the nozzle.

By overlapping tapered sprays across a boom an even distribution across a boom can be obtained.

Deflect pattern

Also known as anvil or flood nozzles, deflect nozzles produce wide angled flat pattern when operated at low pressures (around 1-2 bar). The nozzles

generally produce a coarse even spray and are ideal for use with knapsack sprayers or applications of liquid fertiliser.

Cone pattern

Nozzles produce either a solid circular even footprint (full cone nozzles) or a hollow circular footprint (hollow cone nozzles). Full cones are ideal for use

with knapsacks for spot spraying where as hollow cones are used on air assisted sprayers and traditional boom sprayers when good coverage in dense

canopies is required.

Nozzle filters

Sprayers provide filtration at all stages of the spraying system starting with a coarse basket, foot or suction filter at tank filling, medium filtration in front

of the pump and finer pressure line filters between the pump and the pressure regulator or between boom sections.

It is also possible to fit fine filters behind the nozzle, perhaps where no pressure line filters are fitted or for very low volume appications. However in

practice it may be easier to replace a blocked nozzle rather than replace the filter and it is always advisable to carry replacement nozzles.

Mesh size is important for nozzle filters and recommendations vary with nozzle size; 100 mesh (green) for nozzle sizes 01 and 03, 50 mesh (blue) for

04 to 08 and 30 mesh (red) for 10 to 20.

Filter mesh recommendations are available on all Hypro nozzle charts.

Nozzle filters may be cylindrical which provide the largest screening area, cup filters are an alternative where nozzle holder design dictates and ball check

filters provide some anti drip control where there is no DCV or airstop on the holder.

Calibration

Band and Overall Spraying:

Calibration is vital to ensure that the nozzles are spraying the correct amounts of fluid. It should be undertaken every 100 hectares (250 acres) using

clean water. At the same time, nozzles should be checked for wear and visible damage.

(a) Before calibrating nozzles, ensure that liquid has clear passage by checking and cleaning all filters and removing any restrictions (hose kinks etc)

in the feed and delivery lines. Check also for air leaks and pump performance.

(b) Bearing in mind your operational speed and pressure range, use nozzle selection charts to find the correct flow per minute to produce the application

rate you require.

(d) Using a watch and measuring jug or cylinder, check the output of a single nozzle at that pressure. If the output varies slightly, small pressure

adjustments may be made within the recommended pressure range until the correct output is attained.

(e) If the pressure range is outside that recommended to obtain the correct nozzle output, then change to the appropriate nozzle size. This should be

done by reference to nozzle selection charts. It may then be necessary to re-adjust the pressure setting if your nozzle spacing is other than at 50 cm centres.

(f) Once the correct output has been attained from the test nozzle, all other nozzles should be assessed. If any nozzle output varies by more than 10%, then

that nozzle should be replaced. If necessary, replace all nozzles on the boom to achieve an even spray. Replace nozzles giving broken or uneven spray

patterns. Note: Pressure is normally read from a gauge near the pressure regulator, some distance from the nozzle and consequently there may be a

pressure loss between these two points. It is a good idea to periodically check the pressure at the nozzle. Hypro recommends that periodical checking of

your boom sprayer is carried out by at an AEA or NSTS approved Sprayer Test Station.

Overall spraying:

(a) Check sprayer speed. This is vital for accurate spraying as wheel slippage can make speedometer readings inaccurate.

(b) Measure off a 60 metre (200 ft) strip down the edge of a field and mark this length permanently by using e.g. painted fence posts.

(c) Start far enough behind the first post to reach the desired speed before you pass it. Note the time it takes you to then reach the second post.

(d) Calculate your actual speed in kmph or mph.

(e) Select the correct type of spray tip using the recommendations on the chemical label.

(f) Select correct spray tip capacity the operating pressure required at the tip considering the effects of spraying pressure on droplet size, spray angle and

coverage. Or: If the desired speed is not shown or your nozzle spacing is different from the 50cm (20 inches) on which most application rate tables are based

(g) Before spraying, check the system for blockages, leaks, kinked pipework, etc, and the spray tips for damage or wear.

Before winter, remember the system should be flushed through with clean water. All caps, nozzles, and filters should be removed and cleaned for storage.

Ensure that no liquid is trapped in the system, as this may freeze.

BOOM HEIGHT

Flat fan nozzles:

The fans from alternate nozzles should meet just above the target, whether the target is the ground, top of the crop or top of the weeds – whichever is the

highest at the time of spray application.

Cone spray nozzles:

Designed to have no overlap, the patterns produced by SwirlTip and HollowTip nozzles should not touch.

SWATH MARKING

To make sure that chemical will be applied evenly over the field, it is necessary to mark-out the field using tramlines, bout marker or flags.

(a) Tramlines must match the spray boom – remember that nozzles can be blanked-off to reduce boom width

(b) Foam or bout markers are very useful for pre-emergent sprays

Care of nozzles

NOZZLE WEAR

The rate at which nozzles wear depends on the abrasiveness of the liquid, the pressure used and the material that the nozzle is made of. A worn nozzle

means that spray quality and spray pattern will both be compromised. Even with the most sophisticated flow rate governed sprayer this means that the

operator loses control of these two most important spraying parameters.

MATERIALS Polyacetal

Provides good resistance to most chemicals and superior resistance to wear with most agricultural chemistry. Susceptible to strong mineral acids and a

few organic solvents. Resistance to most alkalis is excellent. Organic solvents usually cause slight swelling without any other harmful effect.

Ceramic

Highly resistant to abrasive and corrosive chemistry and provides superior wear resistance in abrasive applications and high pressures.

Polyvinylidene fluoride (PVDF)

Should be used with acid-based agricultural defoliation chemistry. Good resistance to wear. Resists many reagents and temperatures up to 300ºF.

Susceptible to high temperatures above water boiling (210ºF) in combination with concentrated sulphuric and nitric acids. Preferred in industrial

spraying applications.

Stainless steel

Good resistance to chemicals and provides average wear resistance.

Brass

Average resistance to most chemistry and poor wear resistance. Susceptible to corrosion especially with fertilisers.

CARE OF NOZZLES

Hypro spray nozzles are precision-engineered components. Always keep a new nozzle from a set and compare used nozzles with it to assess their condition

over time. Nozzles should be replaced when their output (flow in litres per minute) has increased by 10% or more and at least every year. This can be

assessed by reference to nozzle selection charts. To clear blocked nozzles, soak in water and clean with a brush and airline. For stubborn deposits soak in

warm water and detergent, agitating occasionally. Never blow through a nozzle or poke with wires or pins – even the slightest damage to the orifice will

alter flow rate angle and spray distribution.

Care of filters

Check filters regularly, cleaning out any debris under running water. Replace filters which are damaged to prevent blocked nozzles.

Useful Websites:

Pesticides Safety Directorate (PSD)