Precision potential

27 November 1999

Precision potential

Unconvinced about precision technology? So was one Kent farmer until he got his hands on a variable rate spreading system, reports Peter Hill.

AFTER 2,500ha-worth of experience with a variable rate fertiliser spreading system, Tom Forsyth, farms director at Sternberg Farms, Tenterden, Kent is convinced there is a place for such equipment in agriculture.

As guinea-pig user of Vicons ProFaS precision farming software, he and tractor driver Mark Babbage have seen at first hand how computer controlled variation rate application and recording can be used as a tool to cut costs, make more efficient use of fertiliser, and simplify some management aspects of the operation.

"I have never been convinced about the value of yield mapping because thats only telling you whats happened in the past," says Mr Forsyth. "With this system, we have been able to use it from day one to improve our use of fertiliser, so you get a quick return on what will be a modest investment."

ProFaS is mapping software developed by Vicons in-house electronics department that enables field maps to be created from GPS data, then application maps to control the spreader. The operation itself can be recorded to provide individual job records.

The latter aspect will become more important in light of environmental concerns and crop assurance, believes Mr Forsyth.

"With this system, we can show an exact record of what has been put on where, and even the time of day, how long the job took and even the average speed of the tractor," he points out.

But it is the ability to determine application rates and reliably apply them that is of most value, adds Tom Forsyth.

"Our spreader operator Mark Babbage would already adjust rates to some extent according to our previous experience and what he finds in the field," he says. "But now we can do that in a more structured way."

With no yield maps on which to base such decisions, this process relies on practical experience of field and crop characteristics, as well as soil analysis – now possible with greater accuracy thanks to GPS – in the case of phosphate and potash.

Different top dressing rates on light and heavier soils, for example; easing off rates where crops are thick, raising them a touch when tillering needs a boost. Trimming rates in "wind funnels" between trees to discourage lodging and on headlands to reduce lodging caused by over-applications that result from spreading overlaps.

New uses for the technology have also been found.

"We map volunteer rape before cultivations, for example, as an indicator of slug activity within different areas of the field, then apply pellets after drilling accordingly," explains Mr Forsyth. "And spreading fertiliser on dairy paddocks within fields has become so much easier by boundary mapping the areas that are done on a particular day so we have a clear indication of which ones need doing next time around."

As Mr Forsyth says, far better than a scribbled note on a crumpled piece of paper in his back pocket.

For operator Mark Babbage, the spreading operation has become a lot more interesting and satisfying.

"With regular tray testing to check the spread pattern and a built-in weighing system on the spreader checking calibration, we are already doing things as well as possible," he says. "GPS spreading and recording completes the set and puts spreading accuracy on a level with spraying."

Putting fertiliser on the map

ALTHOUGH ProFaS can be used with sprayers and seed drills through the Vicon implement controller, fertiliser spreading offers the most obvious and valuable benefits, says Tim Baker, technical manager at Vicon in the UK.

"At around £2,800 for a complete system, including GPS receiver and annual correction signal subscription, it also has the prospect of giving a quick return on the investment," he suggests.

There is the added cost of using a more sophisticated spreader (Vicons weigh-cell equipped Rotaflow RS-XL EDW costs £32,565 – more than a standard electronic model), but the hidden gains of more accurate and effective use of fertilisers, especially of materials with poorer spreading characteristics, must also be taken into account.

To get the system up and running, field boundaries must first be mapped by simply driving around them to record GPS position data. Then, application maps can be created on a desktop computer by overlaying a grid, setting an overall application rate, and clicking squares with a different rate as required.

Information is stored on low-cost chip cards so that it can be transferred to the spreader controller which reads both GPS position and application rate data to put on the right amount in the right place.

The operator can record the spreading operation at the same time. So any manual rate adjustments decided in the field, or any variation caused by changes in spreading characteristics, can be included in the master field records and taken into account when subsequent dressings are made.

Rene Koorhuis of Vicon says future developments are likely to include automatic spreader adjustment to avoid excessive overlap at headlands and on short work, and the ability to return to mid-tramline after a hopper fill-up and automatically start spreading where the machine left off.

Premium for weigh-cell version of Vicon Rotaflow RS-XL disc spreader with electronic calibration and control system £2,565

ProFaS computer software £187

Racal OmniStar GPS receiver £1,812

Annual subscription to Racal OmniStar GPS correction signal £483

Two data card readers/writers £300

Two RS232 cables £23

Total £5,370

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