Pro Operator

Airforce cuts drift and boosts performance – Summer ’19 edition

Hardi sprayer

Air sleeve sprayers were all rage back in the late 1980s and 1990s, but quickly lost out to less costly and easier to use modern air inclusion nozzles. But up in Scotland one cereals grower swears by the system.


Willie French, who has been using a Hardi sleeve boom trailed sprayer for the past six seasons, says any increases in cost and complexity are more than recouped by the benefits. Indeed, he’s so convinced he has just replaced his first machine with another.

While he says his farm at New Keig, Alford in Aberdeenshire, is not particularly windy, with land at heights between 200m to 400m, it’s not that calm either and winds do pick up in the early afternoon. By using the Hardi Twin sleeve boom he is able to continue to spray for at least two extra hours each day.

“Timeliness of application is very important, particularly with fungicides,” he says. “It not only controls the drift to enable us to work longer, the air stream also parts the crop and allows the product to get right down and to the undersides of the plant. Controlling drift is of course also important and that also means more of the expensive chemical goes on the crop – not on neighbouring fields.”

But was this effect worth the extra 20% cost – about £20,000 at the time? “After six years I can say yes to that now – in fact I think it paid for itself in three years,” he says.

Hardi sprayer

It’s not just the ability to spray for longer that has helped recoup the cost. Quite quickly Willie realised with better timeliness, improved coverage, penetration and no drift he could possibly cut fungicide rates as well as water volumes down to 80-100 litres/ha.

“The cost of the spray programmes are often well over £100/ha for spring barley and more than £200/ha for winter crops,” he comments. “It really isn’t hard to save £30/ha even with the extra fuel needed, so the extra cost for the Twin machine pays itself in less than 700ha, that’s without the extra benefit of minimising drift in all conditions.”

Then there’s the timeliness advantages from being able to safely spray for long as well as the opportunity to lower water volumes, which also saves time because you can cover more ground/fill, he adds.

Hardi sprayer

“We cut fungicide rates by at least 25% to see if there was a difference and when we measured the results. The most noticeable difference, with all the treatments, is that the spray penetrates all the way to bottom of the crop and onto the stems. Following our trials we now typically use 3 litres/ha of active in 200 litres/ha of water for desiccation. We could get off with 2 litre of glyphosate, but found we got faster results with 3 litres on greener material,” explains Willie.

Also, the addition of air makes every nozzle LERAPs 3* rated. “There is no noticeable drift, which helps when working near houses – with over 60 gardens neighbouring our fields, it’s important that we minimise any drift, we need to all be aware of that now.”

University trials confirm savings

In Denmark there are strict limits of the amount of pesticides farmers can apply in a season. Independent tests carried out at Flakkeburge/Aahus University, over two years, showed the air-assisted sprayer can provide up to 30% reduction in chemical, using the same Hardi LowDrift nozzles 025 nozzles at 3 bar. At the same time it also showed a the Twin produced a significant reduction in drift.

Hardi sprayer

The research looked at three sprayer set-ups, all using ISO LD 025 nozzles operating at three bar working. This produces a medium spray quality and a droplet size comparable to the German reference nozzle for drift.

  • 150litres/ha with conventional and Twin systems at 8km/hr
  • 100 litres/ha with conventional and Twin systems at 12km/hr
  • 75 litres/ha with a Twin systems at 16km/hr

The trials looked at the deposition under the boom, drift measured to internationally recongnised protocols at two wind speeds: Low – 3-4m/sec and higher 6-8m/sec. Each test was run three times, with 15 runs/day.

In the summary of the conclusions the researchers said, overall the test showed a significant influence from the spray technique. Drift was the highest from the conventional set-up at both test speeds.

Drift from the Twin at 16km/hr was signicantly lower compared with the two speeds with the conventional nozzles. And at 12km/hr and 8km/hr the drift from the Twin was significantly further reduced.

Spray deposition results

Deposition under the 24m wide Hardi Twin boom was more even than under the conventional nozzles – up to 30% better into an open crop and on bare soil. In practical terms, says the researchers, this increase deposition indicates a possible reduction in the amount of active ingredient also by 30%.

In a dense crop the depositions are likely to be higher, they add.

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