Survey points to poor farmer understanding of spray drift

Only one in four farmers understands LERAP star ratings, according to a survey carried by The Arable Group, and just one in seven could answer all seven questions about spray drift and application correctly.

The results suggest spray operators still have more to learn about what causes spray drift, and how to control it.

“What surprised us was how few people understood LERAP star ratings – operators should know that a three-star-rated nozzle results in 75% or more reduction in spray drift compared with a reference 03-110 flat-fan nozzle at 3.0 bar and 0.5m boom height,” says Paul Miller, head of TAG’s spray applications unit, which devised the test.

“It was also worrying that less than half knew that boom height was such an important factor influencing spray drift. With the trend towards higher forward speeds and wider booms, it is becoming very difficult to keep a boom at half a metre above the crop and people need to be aware of the consequences of this.”

On the positive side, three-quarters correctly identified the best nozzles for blackgrass control. “It seems farmers are putting efficacy before drift, which is understandable,” says TAG’s Clare Butler Ellis. “I think we still have some work to do to convince farmers we can achieve both good efficacy and control drift. For example, the best option for control of large broadleaved weeds where drift is an issue has to be an air-induction nozzle, but nearly half of farmers thought otherwise.”

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Need a reminder about spray drift and application? Our Farmers Weekly academies are a useful learning and revision tool, complete with a test-yourself section and BASIS/NRoSO points for successfully answering all the multi-choice questions.


1. ‘Spray quality’ (eg fine, medium, coarse) of a nozzle operating at a defined pressure describes which of the following?

a) the flow rate through the nozzle

b) the uniformity of the distribution pattern

c) the droplet size distribution

d) the risk of spray drift

e) the speed of droplets leaving the nozzle

2. For a boom sprayer operating over arable crops, which of the following factors is most important when seeking to minimise the risk of drift?

a) forward speed

b) type of crop

c) wind speed

d) operating pressure

e) boom height

3. Nozzles that have achieved a “LERAP low drift star rating” will give drift reductions when compared with the reference “03” 110 flat fan at a pressure of 3.0 bar and height of 0.5m. Which of the following reductions relates to a three-star rating?

a) ≥ 75%

b) 10-50%

c) ≥ 90%

d) 50-75%

e) ≥ 66%

4. Which of the following nozzle types will give the lowest level of drift when mounted on a conventional boom sprayer?

a) hollow cone

b) air-induction flat fan

c) conventional flat fan

d) pre-orifice flat fan

e) an extended range/variable pressure flat fan nozzle

5. For treating blackgrass in the autumn at 100 litres/ha, the largest amount of chemical and best efficacy is likely to be achieved with:

a) conventional nozzles giving a fine spray quality

b) conventional nozzles giving a coarse spray quality

c) air-induction nozzles

d) a pre-orifice flat fan nozzle

e) an extended range/variable pressure nozzles

6. Formulations are known to influence spray formation and drift. Which of the following tank mixes are most likely give the greatest risk of drift?

a) a pre-emergent treatment for grass weed control in cereals

b) a mixture of two fungicide products applied as a T2 spray for winter wheat

c) a fast-acting formulation of glyphosate applied to set aside

d) a tank mix of grass weed herbicides for autumn application in cereals

e) a T3 application to winter wheat

7. Which option would be most suited for applying a selective broad leaf herbicide to relatively large weeds in an area where good control of the drift risk is also required?

a) an air-induction nozzle at 100 litres/ha

b) a conventional nozzle giving a medium quality spray and operating at 100 litres/ha

c) a hollow cone nozzle giving a medium quality spray and operating at 100 litres/ha

d) a pre-orifice nozzle at 100 litres/ha

e) a conventional nozzle giving a medium quality spray and operating at 200 litres/ha

Answers: 1c 2e 3a 4b 5e (or a) 6c 7a

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