Busy contractor gives thumbs up to top-up system

28 January 2000

Busy contractor gives thumbs up to top-up system

AFTER a seasons use one Norfolk contractor is already enthusiastic about PrecisioN Sensor, the nitrate topping-up system developed by Hydro.

Giving a plant only the amount of nitrogen it needs – no more, no less – is the principle behind the PrecisioN Sensor. But its effectiveness still has to be evaluated in financial terms, says Rick Hartley.

Last year Hartley Farm Services of Carleton Rode, Norfolk, did about 600ha (1480 acres) of variable rate nitrogen application. Results have been encouraging allowing the same quantities of nitrogen to be applied to customer fields, but with variations within fields to reflect the needs of different areas of crop.

"We are not saving on a customers nitrogen bill, nor increasing it – PrecisioN Sensor has simply allowed more precise application of nitrogen," he says. "As a result, there has been a reduction in lodging. It has convinced me that N variations are justified."

The tractor-mounted system senses the reflectance and colour of the crop, varying the rates of second and third splits of N accordingly. "In virtually every field we used the PrecisioN Sensor, the variation in application rates was much less on the third application – in the space of about four-five weeks, each crops nitrogen requirement had evened out."

But with such a high dependence on light for accurate sensing of crop colour, the system has a limited working window, he adds. "Weather permitting, we have been confined to variable rate N applications between 9.30am and 4.30pm."

In future Mr Hartley would like to see the system developed further so it could be used for variable rate desiccation on oilseed rape, for example. &#42

Geoff Ashcroft


The Chavtrac 410 power unit (above) is equipped with a demountable Bredal spreader body, the PrecisioN Sensor sitting atop the Chavtracs cab. Raven electronic controls and GPS equipment link the spreader and sensor to vary rates. The majority of Mr Hartleys spreading work is on 24m (79ft) tramlines, at 10-11mph.

Variable-rate N applications worked for Norfolk contractor Rick Hartley last year. In-cab Raven rate-controllers linked to Hydros PrecisioN Sensor adjusted bagged N application rate according to need. But good daylight is needed for effective use – something which restricted use last year.

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