We constantly work for a better environment by developing technologies that reduce the amount of plant protection products needed and lead to fewer residues in food, drinking water and the environment.

On an EU level, we constantly see new regulations regarding chemical registrations, risk assessments and drift reduction. The last of these getting a lot of attention as it seems the easiest area to improve – plus excessive drift is both visible and measurable.

From a farmer’s point of view, where large areas must be treated in environmentally safe ways, it is vital to be aware of drift and pay close attention to the specific demands of each plant protection product – such as buffer zone, dosing, waiting times, etc.

Any spraying must also be done without generating negative contact with the non-farming community. So, for the farmer, drift reduction is a must! In a lot of countries, most sprayers are now equipped with drift-reducing injector nozzles.

Based on this, drift reduction should no longer be a major issue. But we still have a lot of discussion and daily questions from dealers and farmers. The main reason is that the drift reduction demands are different in the different EU member states, making the whole issue highly complex.

What is spray drift?

According to ISO 22866, spray drift is the amount of sprayed material that does not reach the target due to the wind at the time of application. The drift quantity that is experienced will always be closely related to the prevailing wind speed.

In legislative terms, the field boundary is most important, as the field is the target.

Experts divide drift into sedimentation and airborne components.

The sedimentation part can be measured on the ground close to the sprayed area, while the airborne drift is a cloud which moves upwards and settles further away. The sedimentation part is higher and closely related to the drift potential of the nozzle being used.

However, the amount of drift is not so high that a farmer should expect a reduction in the efficiency of the applied product when spraying under good farming practices (wind speed 2 m above ground <5 m/s). For example, in the German drift curve the measured value 1 m away from the last nozzle is less than 1%.

Does every EU member state have its own drift reduction list?

No, but every member state does have regulations designed to limit drift and generally minimise the amount of pesticides being used. For example, Denmark and Sweden are copying the German JKI drift reduction list. However, the Netherlands, Belgium, UK and France have their own list.

The major difference between each country is the reference drift curve, which has been defined in field drift trials.

In addition, the major risk zones can be different – most countries now measure drift up to 20 m away but conduct the risk assessment in different ways.

From a technical point of view, the drift and the drift potential of a specific nozzle

should be the same. However, field tests can be carried out over bare ground, short grass or a crop. All set-ups have specific challenges for the sprayer setting, especially when using HARDI TWIN sprayers, as covered in a separate article.

Wind-tunnel measurement

Today, most nozzles are tested using wind-tunnel drift tests. In these kinds of tests the drift potential of the candidate nozzle is measured, then compared to a reference drift curve. Wind-tunnel trials use a constant wind speed and the nozzle has an exact height and distance to the measuring equipment

Field drift measurement set-up in different countries

Different drift reduction classes

The required drift reduction class for a nozzle or nozzle/sprayer combination is linked to the demands of the plant protection product and the specific width of a non-sprayed buffer zone. Nozzles with the highest levels of drift reduction can be used close to a ditch or other critical area, while a lower drift reduction class demands a wider buffer zone. Some plant protection products can only be applied with drift reduction technology. The spray pressure also has an influence on the drift reduction class. Lower spray pressure leads to coarser droplets and this naturally reduces the drift and drift potential of nozzles.

In ISO Standard 22369 part 1 the drift reduction classes are specified as 50 %, 75 %, 90 %, 95 % and 99 %. The classes are in %, relative to the basic drift curve of the member state. The basic curves are different, so data from one country can’t be directly compared to another. Furthermore, not all classes are used in every country and some use other classes – such as 66 % in France and 97.5 % in NL. The graph shows the steps between the classes. So even though moving from 90 % to 95 % may seem like a small step, measured drift must reduce by 50 %.

Do end-nozzles have an effect on drift? In all drift reduction schemes, injector nozzles are listed in combination with asymmetric end-nozzles, but with the HARDI EndNozzle kit – this is not necessary.

The system uses an angled nozzle holder which turns the spray swath underneath the boom.                                                       This way you will avoid spraying liquids outside the field – meaning you can use the same nozzle across the whole boom without needing extra approvals.

Drift reduction approval of HARDI TWIN FORCE

The concept of the HARDI TWIN System was developed in the 1980s and since then has shown a high potential for reducing drift. In most trials, internally and in independent institutes, the drift reduction is around 75 % compared to the same application parameters of nozzle type, spray pressure, driving speed etc – the same settings with and without air, in other words. In fact, the same sprayer is used and just the air is switched off, even though there could be a drift reducing effect from the airbag, especially at driving speeds above 10 km/h.

You will also see a higher drift reduction if fine and medium spray quality is used, but in drift reduction tests all comparisons are done against standard drift value curves.

Specific drift results with HARDI TWIN FORCE

As a TWIN FORCE sprayer doesn’t fit into a wind-tunnel, expensive field-trials are needed. These always measure actual drift, and never just drift potential. But the resulting registration class can still vary between EU member states.

In the Netherlands, for example, nozzles in combination with TWIN FORCE will result in a higher drift reduction class.

TWIN FORCE reaches German 90 % drift reduction class

In the last year the HARDI COMMANDER TWIN FORCE was tested at the German Julius Kühn Institut in Braunschweig. For the drift reduction approval of a complete boom, a field drift trial was required, and the “real” drift was measured. The result was than compared to the German basic drift value curve and classified. As an added challenge, Germany’s basic curve is the lowest in Europe!

The TWIN FORCE boom with a HARDI MiniDrift 03 and asymmetric end-nozzle attained the 90 % class. In the tests the volume rate was 120 l/ha, with 1 bar spray pressure and 7 km/h driving speed. The test was done over a 60 cm barley crop, which added difficulty as the nozzles were 110 cm above ground and the small drifting droplets needed longer to settle.

The MiniDrift 03 had previously qualified for Germany’s 75 % drift reduction class in wind-tunnel testing. So TWIN FORCE reduced drift by at least another 60 % to reach the 90 % class.

In this field trial an ISO-F 04 was used as reference nozzle, which in most cases represents the German basic drift curve, but under this higher boom height conditions the drift of the ISO-F 04 was higher than the basic curve. Using the ISO-F 04 in combination with TWIN FORCE air assistance achieved a 75 % drift reduction.

50 % reduction with fine spray quality

TWIN FORCE is still the only approved application system to achieve a 50 % drift reduction with fine spray. Over the test crop it was used with an ISO-F 025 nozzle at a spray pressure up to 2.5 bar – the setting for 100 l/ha at 8 km/h.

With the ISO-F 04 and up to 3 bar spray pressure, the 75 % drift reduction class was reached, which is the only setting with medium spray quality listed.

TWIN FORCE has more advantages

Drift reduction is not the only advantage of the TWIN FORCE system – active air assistance also allows spraying in more challenging wind conditions and at higher driving speeds. In addition, spray penetration, coverage and deposit are all improved in dense crops.