Not so long ago, 36 metres was considered a large spray boom. But in recent years the rise of engineered aluminium has made 48.5 and even 54.5 metre booms increasingly normal.

Larger booms boost productivity – getting more ground covered in the available weather window and sparing the operator many hours on the sprayer. However the tip-to-tip speed difference across a wide, turning boom is also driving the need for a fast, precise nozzle control technology.

As HARDI Australia’s Product Manager for large sprayers Steve Lancaster points out, the outer tip of a 48.5 m boom travels considerably faster than the inner tip in every turn – leading to significant under- and over-dosing around headlands or any obstacle in the paddock.

“HARDI solves the problem by combining multi-tiered spraying with the H-SELECT system,” he says. “It provides accurate target rate control over the widest possible speed range.”

H-SELECT co-ordinates up to four different nozzles at each nozzle body to continually maintain the required target rate across the boom and speed range.

“H-SELECT calculates the speed of the sprayer and automatically activates the best combination of nozzles for each boom section,” Lancaster explains.

This rapid, blended switching between nozzle combinations means H-SELECT can achieve a target rate accuracy of 90% or better over the entire paddock – virtually eliminating patches of over- or under-dosage.

The nozzles can be activated individually and together. For example, a nozzle in the Number 1 position can be selected in any of eight combinations:

1, 1-2, 1-3, 1-4, 1-2-3, 1-2-4, 1-3-4, or 1-2-3-4

Similar selections are also possible with each of the Number 2, 3, and 4 positions.

Discounting duplications (like 1-2 vs. 2-1), H-SELECT effectively functions as a 16-tier spraying system.

The nozzle switching is controlled by a solenoid-activated air pressure system, which also enables constant fluid recirculation and lets the boom be operated in unlimited sections. (18 sections is standard.)

Air switching frees the system from the electrical losses incurred by electronic platforms when the wire runs exceed about 18 metres per side, or 36 metres overall.

Precise droplet control also makes H-SELECT an effective drift management system. Because it uses combinations of nozzles to manage the target rate at a constant pressure, the droplet size doesn’t change with the rate adjustments.

“The operator can set a droplet size and even change it on the move, using the in-cab Run Screen,” Lancaster reports. “It means they can adjust their droplet size throughout the day, to manage wind speed, temperature and humidity changes.”

“Farmers can also use a coarse droplet to spray the paddock perimeter, then change to a finer setting once they’re away from the fence lines.”

Operators are able to plan their H-SELECT set-up with the complementary Nozzle Watch desktop application for Windows® PCs.

This software automatically calculates the optimum nozzle selection for a desired droplet size, target rate and speed range. Alternatively, operators can specify nozzles or specify fewer than four (keeping one position free for a fertilizer nozzle, for example).

Nozzle Watch then displays nozzle combinations and speed bands, plus overall rate accuracy for the job. Use all four recommended nozzles and that will usually be 90% or above.

Readers can get an overview of Nozzle Watch and download the software to try, via a video hosted by HARDI’s Territory Manager for Queensland/Northern NSW, David Wooley. You can access the video by clicking this link. 

Meanwhile, Steve Lancaster feels sure H-SELECT is the solution that large-scale spray operators have been waiting for.

“We believe the combination of air switching and multi-tier nozzle selection makes H-SELECT an effective nozzle control technology for booms 36 meter and above,” Steve Lancaster concludes.

“And with so much riding on sprayer productivity, these big booms are the way of the future.”

H-SELECT is currently available on HARDI RUBICON and SARITOR 62 ACTIVE self-propelled machines, and HARDI COMMANDER trailed sprayers. The system integrates with the on-board ISOBUS.