Boom spreaders can boost fertiliser accuracy

Disc fertiliser spreaders have come a long way in recent years. But they still don’t give the accuracy that some growers want, causing them to operate boom spreaders instead.

“It was a hell of an expense,” says David Miller of the spreader used by Wheatsheaf Farming, a management and mechanisation joint venture between Hampshire landowners.

See also: Kuhn AGT 6036 is a goliath

 “But the trailed boom spreader we use has given us more spreading days and enough output to save a man on the job at peak times.”

Based on the outskirts of Basingstoke, the Wheatsheaf enterprise farms more than 1,500ha of mainly loam over chalk soils. They grow breadmaking and biscuit wheats, spring barley seed, feed varieties of winter barley, and oilseed rape.

Cover crops grazed off by sheep have been introduced this year as part of a transition to a more holistic approach to soil management and crop production.

Cosmetic issue

“It was during a partners’ farm tour that the question was raised about the yellowing and fall-off in plant height around the edges of cereal crops,” Mr Miller recalls. “That’s not just a cosmetic issue – there must clearly be some impact on yield in those areas as well.”

The questions prompted a review of fertiliser spreading practice on the farms, which at the time involved a 2t capacity twin-disc spreader. It brought into sharper focus the cost of the machine’s output limitations, which resulted from the hopper size and being restricted to spreading when weather conditions allowed.

David Miller

David Miller ©Peter Hill

To overcome the former when the pressure was on to get round crops with spring dressings, a second staff member with a forklift was allocated to speed up refill turnarounds. But nothing could be done about the spreading method.

“Disc spreaders are clearly a lot more accurate across their spreading width than they used to be and you can now have them loaded with weigh-cell and GPS technologies,” says David Miller.

“But for spreading around the perimeter of fields, you still have rather basic methods of deflection to modify the spread pattern.”

Inevitably, he suggests, that results in a shortfall in application rate in the outer areas of the crop while still getting some fertiliser where it is not wanted – into field margins where it encourages grass and other weeds to encroach.

“With the boom spreader, it works across 24m to the line at the correct rate across the complete width. It’s as good as putting on liquid fertiliser in that respect.”

20 plastic deflectors

The Kongskilde Wing Jet S4000 spreader used for the past five years distributes fertiliser from 20 upturned plastic deflectors positioned across the boom and arranged in four sections, each supplied by its own metering roller mechanism via a series of rigid plastic tubes.

Distributors on the boom of the Wing Jet S4000

©Peter Hill

Sections can be switched on and off manually to adjust the working width to avoid overlaps in corners, at angled headlands and in areas where tramlines converge, or set up with automatic switching under GPS control.

This is available as a factory-fitted option on the new K-Plus Hydro model – which has hydraulic metering roller drive – in the form of a task controller that communicates with John Deere GreenStar 2630, Topcon X30 and similar terminals.

But section switching was added as a retrofit installation to Wheatsheaf’s preceding model, which involved replacing the friction metering roller drive with electric drive and adding a task controller programmed through a Topcon X20 terminal supplied by UK agent LH Agro.

“That raised the old issue of who’s responsible if something goes wrong but once everything was sorted the system worked well,” says David Miller. “In fact, we’ve since gone on to apply P and K at variable rates, and used SoylSense for variable rate N before changing over to the Yara N-Sensor for real-time nitrogen assessment and rate variation.”

Angled boom

The boom operates at a fixed height – dependent upon whether flotation or row-crop wheels and tyres are fitted – but the two halves of the spreader’s boom can be angled upwards by up to 1.5m at the tip if necessary to fit contours.

They can also be tilted in unison by the same amount to keep the boom parallel to the ground across banks.

A suspension system with hydraulic cylinders, a gas accumulator and rubber blocks to control diagonal movement keep the boom as stable as possible. However, ultimately, this depends on running over a relatively smooth field surface or tramlines.

For travel the boom folds in, gullwing-fashion, to a vertical parking position behind the stainless steel hopper. Capacity is 4,000 litres as standard and 6,000 litres with the optional extension fitted, so there’s scope to cover a lot of ground between refills.

Windy conditions

That was another contributing factor in Wheatsheaf Farming’s decision to operate a Wing Jet as it adds to the machine’s tolerance of moderately windy conditions and consequent seasonal capacity.

“You can’t go spreading in all conditions because it does rely on throwing the fertiliser into the air a bit for full width distribution, but it does have to be very windy before it stops us,” says David Miller.

“That gives us more spreading days and together with the output gain from having a larger hopper it means we no longer need someone in the field on loading duties,” he adds. “Instead, he could be put on sprayer support and have a much bigger impact on work rate and timeliness of operations.”

The Kongskilde machine comes with a spring-reel hopper cover that rolls back after rubber securing straps are released and is extended again by the operator pulling on a string from the front-mounted access ladder.

Generous hopper opening dimensions of 2.1×2.6m make it easy to fill from an IBC or loader bucket.

A calibration tray, weigh bag and scales are supplied, and the current version’s K-Plus controller provides a hopper level indicator among its numerous functions.

Hydraulic oil sourced from the tractor is used to drive the metering rollers, which as a useful bonus at a time when growers are turning to different approaches to blackgrass control, can be adapted to handle Avadex.

“A granule kit made up of plates to reduce the exposed surface of the metering rollers and flow restrictor flaps in the hopper has enabled us to put Avadex on all our winter barley at the two- to three-leaf stage,” notes David Miller.

“It introduces a different chemical mode of action to the crop rotation to help control blackgrass more effectively.”

Kongskilde and Kuhn

Kongskilde’s Wing Jet K-Plus Hydro and the Kuhn AGT 6000 are now the only pneumatic fertiliser spreaders supplied new in the UK.


The latest Wing Jet has a bigger base hopper at 4,800 litres expandable to 6,000 litres and comes with a choice of four boom sizes from 12m to 24m. The chassis is supported on a rigidly mounted axle for up-to-40kph road travel.

A new electronically controlled hydraulic transmission for the metering mechanism allows variable-rate application and four-section cut-off regulated either manually or via GPS.

List price is £71,490, with the hopper extension adding £1,480.


The trailed Kuhn machine has a 6,300-litre hopper for up to 5t of fertiliser and runs on a hydro-pneumatic suspension axle rated to 50kph.

There are three boom sizes from 30m to 36m with active height control. Six-section metering and shut-off is operated manually or by GPS, with variable application rate also available.

List price is about the £130,000 mark, depending upon the final specification.

Kuhn AGT 6036 pneumatic fertiliser spreader

©Peter Hill