Variable width adjustment could reduce wastage

Working width control is becoming more commonplace as a means of minimising fertiliser wastage and keeping application coverage as even as possible. Peter Hill reports

Plenty of sprayer operators have come to appreciate the ease of use provided by GPS-guided boom-section on-off control systems. But there are now similar benefits to be gained from the variable-width controllers available on a growing number of fertiliser spreaders.

With the introduction of Kuhn’s Vari Spread for the 2013 season and Auto-Switch for the KRM-Bogballe spreaders, most of the leading suppliers can now offer auto width adjustment on their top-spec machines.

They join Kverneland’s GEOspread software, which is operated through the IsoMatch Tellus isobus terminal for Vicon Rotaflow and Accord Exacta spreaders, and Amazone’s GPS-Switch system, which gives variable width working on ZA-M mounted and – uniquely – ZG-B trailed spreaders.

As well as altering the spread width progressively when approaching headlands at an angle or where tramlines converge, these advanced control systems will also stop and start spreading at the appropriate point when approaching and departing headlands.

This function alone is provided by the Stop & Go system on Sulky X-series broadcasters from Reco, with limited automatic width adjustment provided by the border spreading mechanism on one side of the machine.Auto headland on-off is also available with the Opti Point system for Kuhn Axis mechanical and hydraulic disc drive spreaders, and for trailed Bredal spreaders from KRM and Güstrower machines from Ryetec Engineering.

Identifying the optimum switch-off and switch-on points for a fertiliser spreader is a challenging issue. For one thing, a spreader throws material almost as far behind the machine as it does to either side; for another, the distance is influenced by the type of material being applied.

It has been a big task for manufacturers to come up with calibration data for different materials and working widths that also take into account forward speed. With variable spreading width, there is the added requirement to adjust the flow of material in line with changes.

Spreading is carried out around the perimeter of the field as usual with the border setting engaged at the discs, the spreader’s electronic control system in “manual”, and with the GPS system recording the pass.

This creates a headland reference point for on-off control, so for subsequent runs the operator no longer has to judge by eye when to push a button or flick a switch. The tendency is always to err on the side of caution and over-apply rather than risk missed patches.

Spreading width is adjusted in steps wherever a significant overlap will waste fertiliser and add to the lodging risk.



  • System: GPS-Switch
  • Spreaders: ZA-M Hydro, 3,000-litre, 36m; ZA-M Ultra Hydro, 3,600-4,200-litre, 52m; ZG-B Ultra Hydro, 5,500- and 8,200-litre, 52m (trailed)
  • Disc drive: Hydraulic
  • Width adjust: Disc speed
  • Headland on/off: Yes
  • Variable width: 6 sections

Amazone’s GPS-Switch system can be used with hydraulic disc drive versions of the ZA-M mounted and ZG-B trailed spreaders to automate working width adjustment in steps on the move; it adds automatic headland shut-off and start-up. Spreading width is altered in three steps either side of centre by changing disc speed, so a machine spreading to 36m will close down in 6m steps. The system has its own operating terminal linked to the Amatron+ controller.


Kverneland Accord

  • System: GEOspread
  • Spreaders: Exacta CL EW ISO – 1,100-2,000-litre, 24m; Exacta TL – 1,500-3,900-litre, 45m
  • Disc drive: pto
  • Width adjust: Feed-on point
  • Headland on/off: Yes
  • Variable width: 24 sections

Accord Exacta spreaders with pto-driven discs and weigh cell calibration/rate regulation can operate with GPS-guided variable width control using GEOspread software, which is available to unlock on the Kverneland IsoMatch Tellus isobus terminal. This alters the disc feed-on point to change spreading width in 12 steps either side of the spreader, each up to 2m wide.



  • System: GEOspread
  • Spreaders: RotaFlow RO-M EW ISO – 1,100-2,000-litre, 24m; RotaFlow RO-XL EDW ISO – 1,500-3450-litre, 45m
  • Headland on/off: Yes
  • Variable width: 24 sections

GEOspread control software is available on the Kverneland IsoMatch Tellus isobus terminal to operate Vicon weigh cell spreaders with pto-driven discs. Spreading width is changed by altering the disc feed-on point using an electric actuator. With 24 steps of up to 2m each, a spreader working to 36m can shut down 1.5m at a time.



  • System: Vari Spread
  • Spreaders: Axis 40.1 H EMC – 1,200-3,000-litre, 42m; Axis 50.1 H EMC – 4,000-litre, 50m
  • Disc drive: HydraulicWidth adjust: Feed-on point
  • Headland on/off: Yes
  • Variable width: 8 sections

As well as headland on-off, Vari Spread adds auto spreading width adjustment for Axis spreaders with hydraulic disc drive and Electronic Mass Control (EMC) rate regulation. It can shut down the spreading width in four steps either side. It operates through the Kuhn CCI and other isobus terminals. Mechanical disc drive Axis spreaders can operate the system for left or right shut-off only.


KRM Bogballe

  • System: Auto-Switch
  • Spreaders: LW2 Trend – 700-2,050-litre, 24m; M2W Trend – 1,600-3,300-litre, 42m; MW3 Trend – 3,300-4,500-litre, 42mDisc drive: pto
  • Width adjust: Application pattern
  • Headland on/off: Yes
  • Variable width: 8 sections

The Auto-Switch system provides headland on/off and variable width control using a Patchwork BlackBox or TeeJet GPS unit with auto-guidance to provide instructions to the Bogballe Calibrator Zurf, Icon or Uniq spreader controllers updated with the relevant software. The fertiliser distribution pattern provided by the double-double layer, inward rotating spreading disc system is regulated to minimise overdosing. Auto-Switch can be operated by an isobus terminal with section control.

See more