27 February 1998

Accurate mapping is a reality for roots

GROWERS keen on precision farming, who want to extend their field knowledge by mapping root crops too, can now do so with reasonable confidence and accuracy.

Two approaches have been evaluated, using load cells on a trailer or beneath the web rollers on the harvester. Location is plotted and data collected by equipment on the tractor.

The Massey Ferguson trailer system assembled by Agco remains experimental. However, it has shown that both bulk and boxes can be weighed accurately to provide a good indication of yield variation across fields.

RDS Technology has taken its weigh cell roller design a stage further by putting it to commercial use. It is now on sale at £3200 a time.

The high value and high input costs associated with crops such as potatoes, onions, carrots and sugar beet make them especially relevant to precision farming techniques; small improvements in yield or reduction in costs can have a significant effect on the bottom line.

Relatively long rotations make it more difficult to use yield maps, but experiments are continuing to see whether yield patterns seen in combinable crops are repeated in root crops. If they are, then mapping the root element of the rotation helps fill a gap in the data.

The RDS system has been used both experimentally and commercially on potato and sugar beet harvesters. Several growers in Canada and the United States are using the system to map potatoes and the company has seen some good results from sugar beet harvesting with a co-operative in France, says RDS engineering director Peter Nelson.

"We cant achieve the same accuracy as with combinable crops, but at 5% its close enough."

The kit can be incorporated into new harvesters or retro-fitted to existing ones. It puts load cell mountings beneath two or three of the idler rollers supporting the harvester conveyor/elevator trace. A forward speed sensor on the axle and row width selector connected to the Ceres control unit provide further inputs, along with a conveyor speed sensor and on-off switch for headland turns.

"As long as the crop comes off the harvester pretty clean, or tares can be assessed with reasonable accuracy the system is pretty accurate," maintains Mr Nelson.

The RDS approach provides continuous weight data from which yield maps can be produced. By contrast trailer weighing may complicate data collection where more than a few trailers are used.

However, trailer weighing can produce accurate results. Early trials with an 8t capacity MF700-series trailer taking sugar beet off a six-row harvester came within 10kg (22lb) of weighbridge check recordings. &#42

It can be done, but is it worth it? Root crop yield mapping – in this case potatoes – can be performed on the harvester or the trailer with reasonable accuracy.