3 November 1995

Dutch aim to clean up their harvest

BRUSHES, finger rollers, lateral and axial spiral rollers, driven belts and compressed air were all deployed to rid beet of dirt tare at a harvesting demonstration near Rotterdam, Holland, last week.

The event aimed to evaluate innovations designed to cut soil tare, a major concern for the Dutch beet industry (see Arable, p56).

Most striking of all was the use of compressed air on a prototype from the Institute of Sugar Beet Research. Spiral rollers shift loose dirt and clod before jets of compressed air at 8.5 bar (120psi) blast more dirt from the roots. Small brushes provide the finishing touches.

The result on the dry, medium (40% clay) soils at Numansdorp was 2.8% dirt tare. That was matched by another IRS prototype using finger rollers and a driven belt, followed by two sets of four full-width brushes.

A two-row Edenhall trailed machine achieved a similar result, while WKM, TIM and Vredo machines all topped 5.5% dirt tare.

But the £40,000 cost of adding air is increasingly difficult to justify, says the IRSs Piet van den Linden. "Other techniques are closing the gap, so whereas as we used to get a 20-40% advantage, which justified the extra cost, we no longer are."

On light soils brushes alone may be adequate, he suggests. Improved materials mean those can now last a full 240ha (600-acre) campaign.

Particularly useful

On heavier soils, which account for two thirds of the Dutch crop, axial rollers have proved particularly useful for removing clod. They are also a boon in weedy crops.

"But to remove smeared soil something extra is needed – a driven belt or brushes," he suggests. Large diameter turbines also help reduce smearing.

Vervaet has opted for turbines followed by a driven belt carrying beet across finger rollers and on to lateral rollers.

An alternative system developed by beet harvesting newcomer Vredo used a large diameter cage auger along the side of the machine. However, that failed to get tare below 6%.

Holmer used star rollers in its machine to cut soil tare to 4.3%, TIMs lateral rollers left 6.1% dirt tare. Ploegers twin spiral rollers and brushes were unscored.

Agriface opted for extra narrow shears to cut un-lifted roots to 1.6t/ha. But despite the use of axial rollers, soil tare remained high for the site at 4.7%.

Blasting beet with jets of air (left) was the most radical approach to dislodging soil at last weeks Dutch harvester demo. Brushes (right) follow to cut tare to just 2.8% on the IRS prototype.