Make quality assessments at all stages of harvesting, from lifting to store loading, to help minimise potato bruising and maximise saleable yield, the Potato Council says.

The current dry weather is increasing the risk of bruising, which costs the industry £26m a year.

It also does untold damage to consumer confidence, says Gary Collins, the Potato Council’s technical executive. “Undamaged potatoes are the first thing shoppers look for.”

Growers shouldn’t adopt a one-size-fits-all approach to harvester set-up, he stresses. “Harvester settings should be altered for each crop in accordance with soil conditions.”

Test field samples before even beginning lifting, says Eric Anderson, senior agronomist for Scottish Agronomy. “Ideally samples should be put through a system, such as a bruise barrel to test bruise susceptibility.

“These samples should then be hot-boxed and assessed for bruising and damage. This will highlight the crops most at risk from harvesting and grading damage, allowing growers to choose to harvest fields with the lowest risk first.”

Alternatively, open up a field with the harvester and take representative tuber samples a day or so before committing to lifting the whole field, he suggests. “Bruising can vary between fields, so sometimes it is well worth leaving one area and returning to it at a later date.”

While lifting, growers should monitor tubers from a minimum of six loads a day at the final handling point, whether that is end of the harvester elevator or grader, and look for excessive bruising and damage.

“If this is high, more samples should be taken throughout the system to pinpoint the issues, which could be as simple as leaving agitation on when it is not needed,” Mr Anderson says.

“All loads delivered to stores should be monitored on arrival,” he adds. “And during harvesting, the operator should conduct a visual check of the harvester and compare it with Potato Council harvester guidelines.”

Bruising normally takes three days to show, so a hot-box is useful to help identify issues earlier.

“If a grower doesn’t have a hot box, the crop can go into store without bruise and damage levels being monitored,” Mr Anderson warns. “This can prove costly as there may be downgrading or rejections later on.”

Hot boxes can be made on farm, as well as commercially bought, but growers need to remember that tubers need fresh air to avoid breakdown or the development of ketones that can look like bruising.

“The set-up should be 34-36C, with 95-98% relative humidity for 15 to 24 hours,” Mr Anderson says. “Samples should be manually peeled and assessed as soon as they are removed from the hot box.”