GPS mapping breakthrough

12 November 1999

GPS mapping breakthrough

With a price tag of £2800,

Vicons latest GPS fertiliser

application package is

considered to provide a

low cost, precision farming

system for growers.

Andy Moore reports

USING GPS technology to cut fertiliser application costs without the benefit of yield maps, might appear to be a back-to-front approach to optimising yield. But this is what Vicons latest precision farming system aims to do.

The package, known as ProFaS, is designed to be a low cost GPS mapping and recording system for applying fertiliser at variable rates to specific areas within fields.

"Many small to medium-sized growers cannot justify the high investment cost of a full yield mapping system," says Tim Baker of Vicon. "The ProFaS system is a more proactive approach to optimising yields by applying fertiliser at variable rates, within a 1 to 2% accuracy, over field areas."

Designed for use with Vicons weigh cell system used on the EDW Rotoflow spreader, the package operates in four stages.

The first uses GPS to record field characteristics such as shape, size, and boundaries. These are then logged into the farm office computer preloaded with the ProFaS software.

"Once the field area and boundaries are known, the computer draws the field outline with the GPS co-ordinates scaled-down to denote the tramlines – 24m, for example," says Mr Baker.

Application rates

Stage two involves entering the fertiliser application rates according to field growing variables gleaned from the farms existing records. These would include soil types, areas with known compaction problems, weed populations, weather history, crop development, pests and diseases, and so on.

The map then highlights areas of fields with a different colour to denote the required fertiliser application rate.

The third stage includes setting final fertiliser application rates (up to 10) onto the prescribed map, before being saved on the data card and given to the spreader operator.

The card is then entered into the reader/writer in the cab, which works with GPS signals and the ProFaS control box to vary fertiliser rates according to field area requirements.

At this stage in the operation, Mr Baker believes the ProFaS technology comes into its own. "The system automatically varies the application rate, records the rate actually applied and any additional amount put on by the operator."

Application rates are maintained based on information from the tractors forward speed, spreading width and amount of fertiliser in the hopper.

After spreading, the data card is downloaded onto the farm office computer which compares the after-spread map with the original application version.

As a new entrant to site-specific fertiliser application, Sternberg Farms at Tenterden, Kent, started with the ProFaS system in March.

"Before using the system, our control amounted to little more than altering the rates for individual fields – not specific areas within fields," says farms director Tom Forsyth. "This did not provide the level of accuracy we required if fertiliser costs were to be managed effectively."

To date, half of the farms 1600ha (3950 acres) have been spread using the ProFaS technology – four dressings applied to rape, two for wheat and one for grassland.

Mr Forsyth believes the system to be more proactive for ensuring consistent yields across field areas.

"At this stage, the aim is to build up a comprehensive history of individual field growing conditions using the GPS maps," he says.

"Perhaps in two or three seasons time, we can use GPS technology on the combines to discover how the site specific application system has performed." &#42

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