29 January 1999

Hot-sliced spuds might eke out scarce supplies

By Andrew Blake

A TECHNIQUE inspired by a visit to the US could offer salvation for potato growers short of seed for the coming season.

Slicing seed tubers in two to make supplies go further is not new, says Chris Smith of Wilts-based Quality Potato Seeds. But until now there has always been a risk of increased disease in the following crop.

The key to the method he and partner Graham Stewart have developed over the past three seasons is that the rotary knives used are heated to about 800C (1470F). This effectively cauterises the cut surface to limit the spread of blackleg and viruses, says Mr Smith.

The technique is now incorporated into commercial equipment built by Suffolk-based E W Downs & Son. "We got the idea when we saw seed being pressed on to heated knives by hand at Sumit Farms, Colorado. The people doing the job had to wear asbestos gloves and we thought there must be a better way."

The original UK hot-cutting machine was based on a Faun two-row planter fitted with circular gas-heated knives which sliced the tubers as they passed by on cup belts. The snag was that the shaft carrying the blades became so hot it needed a separate cooling system.

The new commercial version retains the same principles, but has overcome the heat problem.

Quality Potato Seeds concentrates on producing top quality seed on the chalk hills of Wilts. Last year the firm produced some 1700t, about 250t being exported to the Iberian Peninsular. Over 400t, all for the UK, was heat-sliced. Main reason for pursuing the idea was to boost the proportion of replantable seed in a given crop, says Mr Smith, who is also chairman of Cambridge University Potato Growers Research Association. "We cant afford to lift an 18t crop and get only 12t of seed and 6t of ware. We wanted our growers to be able to get nearer 15t of seed." That means grading out tubers above 55-60mm diameter for slicing, he says.

SEED SPUD CUTTING

&#8226 Boosts scarce supplies.

&#8226 Increases disease risk.

&#8226 Heat limits infection.

&#8226 New machinery option.