28 February 1997

Why blow when you

can suck?

A novel potato storage system validated by the PMBs Sutton Bridge Experimental Unit is showing promise on two East Anglian farms. Andrew Blake reports

SUCKED airrather than blown is finding favour. That is the idea behind the suction wall method of positive ventilation for box stores which offers several advantages over existing forced air approaches, according to PMB monitoring.

Commercialised by Scottish firm FJ Pirie & Co, the system offers more even air (and CIPC gas) distribution than so-called letter-box systems, rapid post-harvest drying, and easier management.

Adrian Cunnington and Steve Saunders are monitoring two installations in Norfolk as part of the PMBs Sutton Bridge Experimental Units £350,000 a year applied research and development programme.

Box storage has caught on well in recent years, but most growers still rely on simple in-store air circulation for temperature control, says Mr Cunnington. Positive ventilation, by means of blown letter box systems or the new suction method, potentially gives growers much tighter control and helps get air to all tubers – including those at the centre of the boxes, he explains.

"The beauty of the negative pressure arrangement is that in theory you get a much more uniform and even air flow."

Limited tests to date confirm the claims for the concept, he says. 1995/96 monitoring of 1250t of Saturna for crisping in James Mermagens new ambient air store at Chaucer Farm, Gresham showed that once outside temperatures were suitable cooling was rapid and even. Temperature variation throughout, measured by 21 probes, was only about 1C (1.8F).

Average weight loss at 6.5% over the Oct-May storage period was commercially acceptable as was post-storage fry quality, reports Mr Cunnington.

SUCKED airrather than blown is finding favour. That is the idea behind the suction wall method of positive ventilation for box stores which offers several advantages over existing forced air approaches, according to PMB monitoring.

Commercialised by Scottish firm FJ Pirie & Co, the system offers more even air (and CIPC gas) distribution than so-called letter-box systems, rapid post-harvest drying, and easier management.

Adrian Cunnington and Steve Saunders are monitoring two installations in Norfolk as part of the PMBs Sutton Bridge Experimental Units £350,000 a year applied research and development programme.

Box storage has caught on well in recent years, but most growers still rely on simple in-store air circulation for temperature control, says Mr Cunnington. Positive ventilation, by means of blown letter box systems or the new suction method, potentially gives growers much tighter control and helps get air to all tubers – including those at the centre of the boxes, he explains.

"The beauty of the negative pressure arrangement is that in theory you get a much more uniform and even air flow."

Limited tests to date confirm the claims for the concept, he says. 1995/96 monitoring of 1250t of Saturna for crisping in James Mermagens new ambient air store at Chaucer Farm, Gresham showed that once outside temperatures were suitable cooling was rapid and even. Temperature variation throughout, measured by 21 probes, was only about 1C (1.8F).

Average weight loss at 6.5% over the Oct-May storage period was commercially acceptable as was post-storage fry quality, reports Mr Cunnington.

Sucking air through potato boxes has improved storage conditions for Norfolk grower James Mermagen (left), seen here with PMB researchers Adrian Cunnington (centre) and Steve Saunders.