9 November 2001

Lessons of an organic potato storage disaster

By Wendy Owen

North-east correspondent

HARVESTING and storing organic potatoes was a key issue at an update day on the ADAS High Mowthorpe/Marks and Spencer Stonechair organic farm in North Yorkshire last week.

The entire 2ha (5-acre) crop of Remarka potatoes grown for seed was lost to blackleg in an ambient store on the 100ha (250 acres) of organic farmland used for the project.

Until storage the crop had looked healthy, with no pest or disease problems and no visible blackleg, said ADAS research consultant David Turley.

Yields were similar to conventional crops grown in parallel production, the Remarka yielding 25-30t/ha and conventional Cara, Maris Piper and Romano yielding 30t/ha.

The headaches started as harvest approached. "We had problems killing the haulm without using chemical desiccants, as the plant was still actively growing," Mr Turley admitted. "Flailing and burning did not achieve the total destruction of the haulm and I think secondary growth allowed the blackleg to flourish."

Harvest conditions also contributed to disease pressure. "The skin-set looked good just before lifting, three to four weeks after haulm destruction, but harvesting was in difficult conditions during mid-September when the soil was still very wet."

Seed spec will be tightened for the coming season. "Although this years seed was certified, it will be specifically tested for blackleg before we buy next time.

"We also need to make absolutely sure we have good skin-set before lifting and we are looking at installing a cold store or renting cold storage nearby for the organic crop. This years results alone would have justified the investment."

Mr Turley stressed that conventionally-grown potatoes on the farm had also suffered similar blackleg damage, partly because of the unusually warm autumn weather, which had exacerbated ambient storage problems.

Better harvesting conditions might have produced very different results, he added. Potatoes can perform well in organic systems, provided they are not subject to pest and disease pressures, such as blight and slugs, he concluded. &#42

ORGANIC POTATOES

——————

* Seed crop lost to blackleg.

* Yield matched conventional.

* In-store breakdown in warm weather.

* Haulm kill, seed hygiene and harvesting conditions blamed.

* Tighter management next year.

——————

ORGANICPOTATOES

&#8226 Seed crop lost to blackleg.

&#8226 Yield matched conventional.

&#8226 In-store blackleg breakdown in warm weather.

&#8226 Haulm kill, seed hygiene and harvesting conditions blamed.

&#8226 Tighter management next year.